To be able to manage buffers inside a shared memory provided
by a VM via a vhost-user interface, we cannot rely on the fact
that buffers are located in a pre-defined memory area and use
a base address and a 32bit offset to address them.

We need a 64bit address, so replace struct desc by struct iovec
and update range checking.

Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>
---
 packet.c | 80 ++++++++++++++++++++++++++++++--------------------------
 packet.h | 14 ++--------
 2 files changed, 45 insertions(+), 49 deletions(-)

diff --git a/packet.c b/packet.c
index ccfc84607709..37489961a37e 100644
--- a/packet.c
+++ b/packet.c
@@ -22,6 +22,35 @@
 #include "util.h"
 #include "log.h"
 
+/**
+ * packet_check_range() - Check if a packet memory range is valid
+ * @p:		Packet pool
+ * @offset:	Offset of data range in packet descriptor
+ * @len:	Length of desired data range
+ * @start:	Start of the packet descriptor
+ * @func:	For tracing: name of calling function
+ * @line:	For tracing: caller line of function call
+ *
+ * Return: 0 if the range is valid, -1 otherwise
+ */
+static int packet_check_range(const struct pool *p, size_t offset, size_t len,
+			      const char *start, const char *func, int line)
+{
+	if (start < p->buf) {
+		trace("packet start %p before buffer start %p, "
+		      "%s:%i", (void *)start, (void *)p->buf, func, line);
+		return -1;
+	}
+
+	if (start + len + offset > p->buf + p->buf_size) {
+		trace("packet offset plus length %lu from size %lu, "
+		      "%s:%i", start - p->buf + len + offset,
+		      p->buf_size, func, line);
+		return -1;
+	}
+
+	return 0;
+}
 /**
  * packet_add_do() - Add data as packet descriptor to given pool
  * @p:		Existing pool
@@ -41,34 +70,16 @@ void packet_add_do(struct pool *p, size_t len, const char *start,
 		return;
 	}
 
-	if (start < p->buf) {
-		trace("add packet start %p before buffer start %p, %s:%i",
-		      (void *)start, (void *)p->buf, func, line);
+	if (packet_check_range(p, 0, len, start, func, line))
 		return;
-	}
-
-	if (start + len > p->buf + p->buf_size) {
-		trace("add packet start %p, length: %zu, buffer end %p, %s:%i",
-		      (void *)start, len, (void *)(p->buf + p->buf_size),
-		      func, line);
-		return;
-	}
 
 	if (len > UINT16_MAX) {
 		trace("add packet length %zu, %s:%i", len, func, line);
 		return;
 	}
 
-#if UINTPTR_MAX == UINT64_MAX
-	if ((uintptr_t)start - (uintptr_t)p->buf > UINT32_MAX) {
-		trace("add packet start %p, buffer start %p, %s:%i",
-		      (void *)start, (void *)p->buf, func, line);
-		return;
-	}
-#endif
-
-	p->pkt[idx].offset = start - p->buf;
-	p->pkt[idx].len = len;
+	p->pkt[idx].iov_base = (void *)start;
+	p->pkt[idx].iov_len = len;
 
 	p->count++;
 }
@@ -96,36 +107,31 @@ void *packet_get_do(const struct pool *p, size_t idx, size_t offset,
 		return NULL;
 	}
 
-	if (len > UINT16_MAX || len + offset > UINT32_MAX) {
+	if (len > UINT16_MAX) {
 		if (func) {
-			trace("packet data length %zu, offset %zu, %s:%i",
-			      len, offset, func, line);
+			trace("packet data length %zu, %s:%i",
+			      len, func, line);
 		}
 		return NULL;
 	}
 
-	if (p->pkt[idx].offset + len + offset > p->buf_size) {
+	if (len + offset > p->pkt[idx].iov_len) {
 		if (func) {
-			trace("packet offset plus length %zu from size %zu, "
-			      "%s:%i", p->pkt[idx].offset + len + offset,
-			      p->buf_size, func, line);
+			trace("data length %zu, offset %zu from length %zu, "
+			      "%s:%i", len, offset, p->pkt[idx].iov_len,
+			      func, line);
 		}
 		return NULL;
 	}
 
-	if (len + offset > p->pkt[idx].len) {
-		if (func) {
-			trace("data length %zu, offset %zu from length %u, "
-			      "%s:%i", len, offset, p->pkt[idx].len,
-			      func, line);
-		}
+	if (packet_check_range(p, offset, len, p->pkt[idx].iov_base,
+			       func, line))
 		return NULL;
-	}
 
 	if (left)
-		*left = p->pkt[idx].len - offset - len;
+		*left = p->pkt[idx].iov_len - offset - len;
 
-	return p->buf + p->pkt[idx].offset + offset;
+	return (char *)p->pkt[idx].iov_base + offset;
 }
 
 /**
diff --git a/packet.h b/packet.h
index a784b07bbed5..8377dcf678bb 100644
--- a/packet.h
+++ b/packet.h
@@ -6,16 +6,6 @@
 #ifndef PACKET_H
 #define PACKET_H
 
-/**
- * struct desc - Generic offset-based descriptor within buffer
- * @offset:	Offset of descriptor relative to buffer start, 32-bit limit
- * @len:	Length of descriptor, host order, 16-bit limit
- */
-struct desc {
-	uint32_t offset;
-	uint16_t len;
-};
-
 /**
  * struct pool - Generic pool of packets stored in a buffer
  * @buf:	Buffer storing packet descriptors
@@ -29,7 +19,7 @@ struct pool {
 	size_t buf_size;
 	size_t size;
 	size_t count;
-	struct desc pkt[1];
+	struct iovec pkt[1];
 };
 
 void packet_add_do(struct pool *p, size_t len, const char *start,
@@ -54,7 +44,7 @@ struct _name ## _t {							\
 	size_t buf_size;						\
 	size_t size;							\
 	size_t count;							\
-	struct desc pkt[_size];						\
+	struct iovec pkt[_size];					\
 }
 
 #define PACKET_POOL_INIT_NOCAST(_size, _buf, _buf_size)			\
-- 
2.47.0

Add vhost_user.c and vhost_user.h that define the functions needed
to implement vhost-user backend.

Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
---
 Makefile     |   4 +-
 vhost_user.c | 970 +++++++++++++++++++++++++++++++++++++++++++++++++++
 vhost_user.h | 208 +++++++++++
 virtio.h     |   1 +
 4 files changed, 1181 insertions(+), 2 deletions(-)
 create mode 100644 vhost_user.c
 create mode 100644 vhost_user.h

diff --git a/Makefile b/Makefile
index 88efe57a681e..f553c8da0ac0 100644
--- a/Makefile
+++ b/Makefile
@@ -54,7 +54,7 @@ FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
 PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c flow.c fwd.c \
 	icmp.c igmp.c inany.c iov.c ip.c isolation.c lineread.c log.c mld.c \
 	ndp.c netlink.c packet.c passt.c pasta.c pcap.c pif.c tap.c tcp.c \
-	tcp_buf.c tcp_splice.c udp.c udp_flow.c util.c virtio.c
+	tcp_buf.c tcp_splice.c udp.c udp_flow.c util.c vhost_user.c virtio.c
 QRAP_SRCS = qrap.c
 SRCS = $(PASST_SRCS) $(QRAP_SRCS)
 
@@ -64,7 +64,7 @@ PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h flow.h
fwd.h \
 	flow_table.h icmp.h icmp_flow.h inany.h iov.h ip.h isolation.h \
 	lineread.h log.h ndp.h netlink.h packet.h passt.h pasta.h pcap.h pif.h \
 	siphash.h tap.h tcp.h tcp_buf.h tcp_conn.h tcp_internal.h tcp_splice.h \
-	udp.h udp_flow.h util.h virtio.h
+	udp.h udp_flow.h util.h vhost_user.h virtio.h
 HEADERS = $(PASST_HEADERS) seccomp.h
 
 C := \#include <sys/random.h>\nint main(){int a=getrandom(0, 0, 0);}
diff --git a/vhost_user.c b/vhost_user.c
new file mode 100644
index 000000000000..1e302926b8fe
--- /dev/null
+++ b/vhost_user.c
@@ -0,0 +1,970 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * vhost-user API, command management and virtio interface
+ *
+ * Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ *
+ * Some parts from QEMU subprojects/libvhost-user/libvhost-user.c
+ * licensed under the following terms:
+ *
+ * Copyright IBM, Corp. 2007
+ * Copyright (c) 2016 Red Hat, Inc.
+ *
+ * Authors:
+ *  Anthony Liguori &lt;aliguori(a)us.ibm.com&gt;
+ *  Marc-André Lureau &lt;mlureau(a)redhat.com&gt;
+ *  Victor Kaplansky &lt;victork(a)redhat.com&gt;
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later.  See the COPYING file in the top-level directory.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <string.h>
+#include <assert.h>
+#include <stdbool.h>
+#include <inttypes.h>
+#include <time.h>
+#include <net/ethernet.h>
+#include <netinet/in.h>
+#include <sys/epoll.h>
+#include <sys/eventfd.h>
+#include <sys/mman.h>
+#include <linux/vhost_types.h>
+#include <linux/virtio_net.h>
+
+#include "util.h"
+#include "passt.h"
+#include "tap.h"
+#include "vhost_user.h"
+#include "pcap.h"
+
+/* vhost-user version we are compatible with */
+#define VHOST_USER_VERSION 1
+
+/**
+ * vu_print_capabilities() - print vhost-user capabilities
+ * 			     this is part of the vhost-user backend
+ * 			     convention.
+ */
+/* cppcheck-suppress unusedFunction */
+void vu_print_capabilities(void)
+{
+	info("{");
+	info("  \"type\": \"net\"");
+	info("}");
+	exit(EXIT_SUCCESS);
+}
+
+/**
+ * vu_request_to_string() - convert a vhost-user request number to its name
+ * @req:	request number
+ *
+ * Return: the name of request number
+ */
+static const char *vu_request_to_string(unsigned int req)
+{
+	if (req < VHOST_USER_MAX) {
+#define REQ(req) [req] = #req
+		static const char * const vu_request_str[VHOST_USER_MAX] = {
+			REQ(VHOST_USER_NONE),
+			REQ(VHOST_USER_GET_FEATURES),
+			REQ(VHOST_USER_SET_FEATURES),
+			REQ(VHOST_USER_SET_OWNER),
+			REQ(VHOST_USER_RESET_OWNER),
+			REQ(VHOST_USER_SET_MEM_TABLE),
+			REQ(VHOST_USER_SET_LOG_BASE),
+			REQ(VHOST_USER_SET_LOG_FD),
+			REQ(VHOST_USER_SET_VRING_NUM),
+			REQ(VHOST_USER_SET_VRING_ADDR),
+			REQ(VHOST_USER_SET_VRING_BASE),
+			REQ(VHOST_USER_GET_VRING_BASE),
+			REQ(VHOST_USER_SET_VRING_KICK),
+			REQ(VHOST_USER_SET_VRING_CALL),
+			REQ(VHOST_USER_SET_VRING_ERR),
+			REQ(VHOST_USER_GET_PROTOCOL_FEATURES),
+			REQ(VHOST_USER_SET_PROTOCOL_FEATURES),
+			REQ(VHOST_USER_GET_QUEUE_NUM),
+			REQ(VHOST_USER_SET_VRING_ENABLE),
+			REQ(VHOST_USER_SEND_RARP),
+			REQ(VHOST_USER_NET_SET_MTU),
+			REQ(VHOST_USER_SET_BACKEND_REQ_FD),
+			REQ(VHOST_USER_IOTLB_MSG),
+			REQ(VHOST_USER_SET_VRING_ENDIAN),
+			REQ(VHOST_USER_GET_CONFIG),
+			REQ(VHOST_USER_SET_CONFIG),
+			REQ(VHOST_USER_POSTCOPY_ADVISE),
+			REQ(VHOST_USER_POSTCOPY_LISTEN),
+			REQ(VHOST_USER_POSTCOPY_END),
+			REQ(VHOST_USER_GET_INFLIGHT_FD),
+			REQ(VHOST_USER_SET_INFLIGHT_FD),
+			REQ(VHOST_USER_GPU_SET_SOCKET),
+			REQ(VHOST_USER_VRING_KICK),
+			REQ(VHOST_USER_GET_MAX_MEM_SLOTS),
+			REQ(VHOST_USER_ADD_MEM_REG),
+			REQ(VHOST_USER_REM_MEM_REG),
+		};
+#undef REQ
+		return vu_request_str[req];
+	}
+
+	return "unknown";
+}
+
+/**
+ * qva_to_va() -  Translate front-end (QEMU) virtual address to our virtual
+ * 		  address
+ * @dev:		vhost-user device
+ * @qemu_addr:		front-end userspace address
+ *
+ * Return: the memory address in our process virtual address space.
+ */
+static void *qva_to_va(struct vu_dev *dev, uint64_t qemu_addr)
+{
+	unsigned int i;
+
+	/* Find matching memory region.  */
+	for (i = 0; i < dev->nregions; i++) {
+		const struct vu_dev_region *r = &dev->regions[i];
+
+		if ((qemu_addr >= r->qva) && (qemu_addr < (r->qva + r->size)))
{
+			/* NOLINTNEXTLINE(performance-no-int-to-ptr) */
+			return (void *)(qemu_addr - r->qva + r->mmap_addr +
+					r->mmap_offset);
+		}
+	}
+
+	return NULL;
+}
+
+/**
+ * vmsg_close_fds() - Close all file descriptors of a given message
+ * @vmsg:	vhost-user message with the list of the file descriptors
+ */
+static void vmsg_close_fds(const struct vhost_user_msg *vmsg)
+{
+	int i;
+
+	for (i = 0; i < vmsg->fd_num; i++)
+		close(vmsg->fds[i]);
+}
+
+/**
+ * vu_remove_watch() - Remove a file descriptor from our passt epoll
+ * 		       file descriptor
+ * @vdev:	vhost-user device
+ * @fd:		file descriptor to remove
+ */
+static void vu_remove_watch(const struct vu_dev *vdev, int fd)
+{
+	/* Placeholder to add passt related code */
+	(void)vdev;
+	(void)fd;
+}
+
+/**
+ * vmsg_set_reply_u64() - Set reply payload.u64 and clear request flags
+ * 			  and fd_num
+ * @vmsg:	vhost-user message
+ * @val:	64-bit value to reply
+ */
+static void vmsg_set_reply_u64(struct vhost_user_msg *vmsg, uint64_t val)
+{
+	vmsg->hdr.flags = 0; /* defaults will be set by vu_send_reply() */
+	vmsg->hdr.size = sizeof(vmsg->payload.u64);
+	vmsg->payload.u64 = val;
+	vmsg->fd_num = 0;
+}
+
+/**
+ * vu_message_read_default() - Read incoming vhost-user message from the
+ * 			       front-end
+ * @conn_fd:	vhost-user command socket
+ * @vmsg:	vhost-user message
+ *
+ * Return:  0 if recvmsg() has been interrupted or if there's no data to read,
+ *          1 if a message has been received
+ */
+static int vu_message_read_default(int conn_fd, struct vhost_user_msg *vmsg)
+{
+	char control[CMSG_SPACE(VHOST_MEMORY_BASELINE_NREGIONS *
+		     sizeof(int))] = { 0 };
+	struct iovec iov = {
+		.iov_base = (char *)vmsg,
+		.iov_len = VHOST_USER_HDR_SIZE,
+	};
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = control,
+		.msg_controllen = sizeof(control),
+	};
+	ssize_t ret, sz_payload;
+	struct cmsghdr *cmsg;
+
+	ret = recvmsg(conn_fd, &msg, MSG_DONTWAIT);
+	if (ret < 0) {
+		if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
+			return 0;
+		die_perror("vhost-user message receive (recvmsg)");
+	}
+
+	vmsg->fd_num = 0;
+	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
+	     cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+		if (cmsg->cmsg_level == SOL_SOCKET &&
+		    cmsg->cmsg_type == SCM_RIGHTS) {
+			size_t fd_size;
+
+			ASSERT(cmsg->cmsg_len >= CMSG_LEN(0));
+			fd_size = cmsg->cmsg_len - CMSG_LEN(0);
+			ASSERT(fd_size <= sizeof(vmsg->fds));
+			vmsg->fd_num = fd_size / sizeof(int);
+			memcpy(vmsg->fds, CMSG_DATA(cmsg), fd_size);
+			break;
+		}
+	}
+
+	sz_payload = vmsg->hdr.size;
+	if ((size_t)sz_payload > sizeof(vmsg->payload)) {
+		die("vhost-user message request too big: %d,"
+			 " size: vmsg->size: %zd, "
+			 "while sizeof(vmsg->payload) = %zu",
+			 vmsg->hdr.request, sz_payload, sizeof(vmsg->payload));
+	}
+
+	if (sz_payload) {
+		do
+			ret = recv(conn_fd, &vmsg->payload, sz_payload, 0);
+		while (ret < 0 && errno == EINTR);
+
+		if (ret < 0)
+			die_perror("vhost-user message receive");
+
+		if (ret == 0)
+			die("EOF on vhost-user message receive");
+
+		if (ret < sz_payload)
+			die("Short-read on vhost-user message receive");
+	}
+
+	return 1;
+}
+
+/**
+ * vu_message_write() - Send a message to the front-end
+ * @conn_fd:	vhost-user command socket
+ * @vmsg:	vhost-user message
+ *
+ * #syscalls:vu sendmsg
+ */
+static void vu_message_write(int conn_fd, struct vhost_user_msg *vmsg)
+{
+	char control[CMSG_SPACE(VHOST_MEMORY_BASELINE_NREGIONS * sizeof(int))] = { 0 };
+	struct iovec iov = {
+		.iov_base = (char *)vmsg,
+		.iov_len = VHOST_USER_HDR_SIZE + vmsg->hdr.size,
+	};
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = control,
+	};
+	int rc;
+
+	ASSERT(vmsg->fd_num <= VHOST_MEMORY_BASELINE_NREGIONS);
+	if (vmsg->fd_num > 0) {
+		size_t fdsize = vmsg->fd_num * sizeof(int);
+		struct cmsghdr *cmsg;
+
+		msg.msg_controllen = CMSG_SPACE(fdsize);
+		cmsg = CMSG_FIRSTHDR(&msg);
+		cmsg->cmsg_len = CMSG_LEN(fdsize);
+		cmsg->cmsg_level = SOL_SOCKET;
+		cmsg->cmsg_type = SCM_RIGHTS;
+		memcpy(CMSG_DATA(cmsg), vmsg->fds, fdsize);
+	}
+
+	do
+		rc = sendmsg(conn_fd, &msg, 0);
+	while (rc < 0 && errno == EINTR);
+
+	if (rc < 0)
+		die_perror("vhost-user message send");
+
+	if ((uint32_t)rc < VHOST_USER_HDR_SIZE + vmsg->hdr.size)
+		die("EOF on vhost-user message send");
+}
+
+/**
+ * vu_send_reply() - Update message flags and send it to front-end
+ * @conn_fd:	vhost-user command socket
+ * @vmsg:	vhost-user message
+ */
+static void vu_send_reply(int conn_fd, struct vhost_user_msg *msg)
+{
+	msg->hdr.flags &= ~VHOST_USER_VERSION_MASK;
+	msg->hdr.flags |= VHOST_USER_VERSION;
+	msg->hdr.flags |= VHOST_USER_REPLY_MASK;
+
+	vu_message_write(conn_fd, msg);
+}
+
+/**
+ * vu_get_features_exec() - Provide back-end features bitmask to front-end
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: True as a reply is requested
+ */
+static bool vu_get_features_exec(struct vu_dev *vdev,
+				 struct vhost_user_msg *msg)
+{
+	uint64_t features =
+		1ULL << VIRTIO_F_VERSION_1 |
+		1ULL << VIRTIO_NET_F_MRG_RXBUF |
+		1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
+
+	(void)vdev;
+
+	vmsg_set_reply_u64(msg, features);
+
+	debug("Sending back to guest u64: 0x%016"PRIx64, msg->payload.u64);
+
+	return true;
+}
+
+/**
+ * vu_set_enable_all_rings() - Enable/disable all the virtqueues
+ * @vdev:	vhost-user device
+ * @enable:	New virtqueues state
+ */
+static void vu_set_enable_all_rings(struct vu_dev *vdev, bool enable)
+{
+	uint16_t i;
+
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++)
+		vdev->vq[i].enable = enable;
+}
+
+/**
+ * vu_set_features_exec() - Enable features of the back-end
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_features_exec(struct vu_dev *vdev,
+				 struct vhost_user_msg *msg)
+{
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	vdev->features = msg->payload.u64;
+	/* We only support devices conforming to VIRTIO 1.0 or
+	 * later
+	 */
+	if (!vu_has_feature(vdev, VIRTIO_F_VERSION_1))
+		die("virtio legacy devices aren't supported by passt");
+
+	if (!vu_has_feature(vdev, VHOST_USER_F_PROTOCOL_FEATURES))
+		vu_set_enable_all_rings(vdev, true);
+
+	return false;
+}
+
+/**
+ * vu_set_owner_exec() - Session start flag, do nothing in our case
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_owner_exec(struct vu_dev *vdev,
+			      struct vhost_user_msg *msg)
+{
+	(void)vdev;
+	(void)msg;
+
+	return false;
+}
+
+/**
+ * map_ring() - Convert ring front-end (QEMU) addresses to our process
+ * 		virtual address space.
+ * @vdev:	vhost-user device
+ * @vq:		Virtqueue
+ *
+ * Return: True if ring cannot be mapped to our address space
+ */
+static bool map_ring(struct vu_dev *vdev, struct vu_virtq *vq)
+{
+	vq->vring.desc = qva_to_va(vdev, vq->vra.desc_user_addr);
+	vq->vring.used = qva_to_va(vdev, vq->vra.used_user_addr);
+	vq->vring.avail = qva_to_va(vdev, vq->vra.avail_user_addr);
+
+	debug("Setting virtq addresses:");
+	debug("    vring_desc  at %p", (void *)vq->vring.desc);
+	debug("    vring_used  at %p", (void *)vq->vring.used);
+	debug("    vring_avail at %p", (void *)vq->vring.avail);
+
+	return !(vq->vring.desc && vq->vring.used && vq->vring.avail);
+}
+
+/**
+ * vu_set_mem_table_exec() - Sets the memory map regions to be able to
+ * 			     translate the vring addresses.
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ *
+ * #syscalls:vu mmap munmap
+ */
+static bool vu_set_mem_table_exec(struct vu_dev *vdev,
+				  struct vhost_user_msg *msg)
+{
+	struct vhost_user_memory m = msg->payload.memory, *memory = &m;
+	unsigned int i;
+
+	for (i = 0; i < vdev->nregions; i++) {
+		struct vu_dev_region *r = &vdev->regions[i];
+		/* NOLINTNEXTLINE(performance-no-int-to-ptr) */
+		void *mm = (void *)r->mmap_addr;
+
+		if (mm)
+			munmap(mm, r->size + r->mmap_offset);
+	}
+	vdev->nregions = memory->nregions;
+
+	debug("vhost-user nregions: %u", memory->nregions);
+	for (i = 0; i < vdev->nregions; i++) {
+		struct vhost_user_memory_region *msg_region = &memory->regions[i];
+		struct vu_dev_region *dev_region = &vdev->regions[i];
+		void *mmap_addr;
+
+		debug("vhost-user region %d", i);
+		debug("    guest_phys_addr: 0x%016"PRIx64,
+		      msg_region->guest_phys_addr);
+		debug("    memory_size:     0x%016"PRIx64,
+		      msg_region->memory_size);
+		debug("    userspace_addr   0x%016"PRIx64,
+		      msg_region->userspace_addr);
+		debug("    mmap_offset      0x%016"PRIx64,
+		      msg_region->mmap_offset);
+
+		dev_region->gpa = msg_region->guest_phys_addr;
+		dev_region->size = msg_region->memory_size;
+		dev_region->qva = msg_region->userspace_addr;
+		dev_region->mmap_offset = msg_region->mmap_offset;
+
+		/* We don't use offset argument of mmap() since the
+		 * mapped address has to be page aligned.
+		 */
+		mmap_addr = mmap(0, dev_region->size + dev_region->mmap_offset,
+				 PROT_READ | PROT_WRITE, MAP_SHARED |
+				 MAP_NORESERVE, msg->fds[i], 0);
+
+		if (mmap_addr == MAP_FAILED)
+			die_perror("vhost-user region mmap error");
+
+		dev_region->mmap_addr = (uint64_t)(uintptr_t)mmap_addr;
+		debug("    mmap_addr:       0x%016"PRIx64,
+		      dev_region->mmap_addr);
+
+		close(msg->fds[i]);
+	}
+
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+		if (vdev->vq[i].vring.desc) {
+			if (map_ring(vdev, &vdev->vq[i]))
+				die("remapping queue %d during setmemtable", i);
+		}
+	}
+
+	return false;
+}
+
+/**
+ * vu_set_vring_num_exec() - Set the size of the queue (vring size)
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_vring_num_exec(struct vu_dev *vdev,
+				  struct vhost_user_msg *msg)
+{
+	unsigned int idx = msg->payload.state.index;
+	unsigned int num = msg->payload.state.num;
+
+	debug("State.index: %u", idx);
+	debug("State.num:   %u", num);
+	vdev->vq[idx].vring.num = num;
+
+	return false;
+}
+
+/**
+ * vu_set_vring_addr_exec() - Set the addresses of the vring
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_vring_addr_exec(struct vu_dev *vdev,
+				   struct vhost_user_msg *msg)
+{
+	/* We need to copy the payload to vhost_vring_addr structure
+         * to access index because address of msg->payload.addr
+         * can be unaligned as it is packed.
+         */
+	struct vhost_vring_addr addr = msg->payload.addr;
+	struct vu_virtq *vq = &vdev->vq[addr.index];
+
+	debug("vhost_vring_addr:");
+	debug("    index:  %d", addr.index);
+	debug("    flags:  %d", addr.flags);
+	debug("    desc_user_addr:   0x%016" PRIx64,
+	      (uint64_t)addr.desc_user_addr);
+	debug("    used_user_addr:   0x%016" PRIx64,
+	      (uint64_t)addr.used_user_addr);
+	debug("    avail_user_addr:  0x%016" PRIx64,
+	      (uint64_t)addr.avail_user_addr);
+	debug("    log_guest_addr:   0x%016" PRIx64,
+	      (uint64_t)addr.log_guest_addr);
+
+	vq->vra = msg->payload.addr;
+	vq->vring.flags = addr.flags;
+	vq->vring.log_guest_addr = addr.log_guest_addr;
+
+	if (map_ring(vdev, vq))
+		die("Invalid vring_addr message");
+
+	vq->used_idx = le16toh(vq->vring.used->idx);
+
+	if (vq->last_avail_idx != vq->used_idx) {
+		debug("Last avail index != used index: %u != %u",
+		      vq->last_avail_idx, vq->used_idx);
+	}
+
+	return false;
+}
+/**
+ * vu_set_vring_base_exec() - Sets the next index to use for descriptors
+ * 			      in this vring
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_vring_base_exec(struct vu_dev *vdev,
+				   struct vhost_user_msg *msg)
+{
+	unsigned int idx = msg->payload.state.index;
+	unsigned int num = msg->payload.state.num;
+
+	debug("State.index: %u", idx);
+	debug("State.num:   %u", num);
+	vdev->vq[idx].shadow_avail_idx = vdev->vq[idx].last_avail_idx = num;
+
+	return false;
+}
+
+/**
+ * vu_get_vring_base_exec() - Stops the vring and returns the current
+ * 			      descriptor index or indices
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: True as a reply is requested
+ */
+static bool vu_get_vring_base_exec(struct vu_dev *vdev,
+				   struct vhost_user_msg *msg)
+{
+	unsigned int idx = msg->payload.state.index;
+
+	debug("State.index: %u", idx);
+	msg->payload.state.num = vdev->vq[idx].last_avail_idx;
+	msg->hdr.size = sizeof(msg->payload.state);
+
+	vdev->vq[idx].started = false;
+
+	if (vdev->vq[idx].call_fd != -1) {
+		close(vdev->vq[idx].call_fd);
+		vdev->vq[idx].call_fd = -1;
+	}
+	if (vdev->vq[idx].kick_fd != -1) {
+		vu_remove_watch(vdev, vdev->vq[idx].kick_fd);
+		close(vdev->vq[idx].kick_fd);
+		vdev->vq[idx].kick_fd = -1;
+	}
+
+	return true;
+}
+
+/**
+ * vu_set_watch() - Add a file descriptor to the passt epoll file descriptor
+ * @vdev:	vhost-user device
+ * @fd:		file descriptor to add
+ */
+static void vu_set_watch(const struct vu_dev *vdev, int fd)
+{
+	/* Placeholder to add passt related code */
+	(void)vdev;
+	(void)fd;
+}
+
+/**
+ * vu_check_queue_msg_file() - Check if a message is valid,
+ * 			       close fds if NOFD bit is set
+ * @vmsg:	vhost-user message
+ */
+static void vu_check_queue_msg_file(struct vhost_user_msg *msg)
+{
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+	int idx = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+
+	if (idx >= VHOST_USER_MAX_QUEUES)
+		die("Invalid vhost-user queue index: %u", idx);
+
+	if (nofd) {
+		vmsg_close_fds(msg);
+		return;
+	}
+
+	if (msg->fd_num != 1)
+		die("Invalid fds in vhost-user request: %d", msg->hdr.request);
+}
+
+/**
+ * vu_set_vring_kick_exec() - Set the event file descriptor for adding buffers
+ * 			      to the vring
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_vring_kick_exec(struct vu_dev *vdev,
+				   struct vhost_user_msg *msg)
+{
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+	int idx = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	vu_check_queue_msg_file(msg);
+
+	if (vdev->vq[idx].kick_fd != -1) {
+		vu_remove_watch(vdev, vdev->vq[idx].kick_fd);
+		close(vdev->vq[idx].kick_fd);
+		vdev->vq[idx].kick_fd = -1;
+	}
+
+	if (!nofd)
+		vdev->vq[idx].kick_fd = msg->fds[0];
+
+	debug("Got kick_fd: %d for vq: %d", vdev->vq[idx].kick_fd, idx);
+
+	vdev->vq[idx].started = true;
+
+	if (vdev->vq[idx].kick_fd != -1 && VHOST_USER_IS_QUEUE_TX(idx)) {
+		vu_set_watch(vdev, vdev->vq[idx].kick_fd);
+		debug("Waiting for kicks on fd: %d for vq: %d",
+		      vdev->vq[idx].kick_fd, idx);
+	}
+
+	return false;
+}
+
+/**
+ * vu_set_vring_call_exec() - Set the event file descriptor to signal when
+ * 			      buffers are used
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_vring_call_exec(struct vu_dev *vdev,
+				   struct vhost_user_msg *msg)
+{
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+	int idx = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	vu_check_queue_msg_file(msg);
+
+	if (vdev->vq[idx].call_fd != -1) {
+		close(vdev->vq[idx].call_fd);
+		vdev->vq[idx].call_fd = -1;
+	}
+
+	if (!nofd)
+		vdev->vq[idx].call_fd = msg->fds[0];
+
+	/* in case of I/O hang after reconnecting */
+	if (vdev->vq[idx].call_fd != -1)
+		eventfd_write(msg->fds[0], 1);
+
+	debug("Got call_fd: %d for vq: %d", vdev->vq[idx].call_fd, idx);
+
+	return false;
+}
+
+/**
+ * vu_set_vring_err_exec() - Set the event file descriptor to signal when
+ * 			     error occurs
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_vring_err_exec(struct vu_dev *vdev,
+				  struct vhost_user_msg *msg)
+{
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+	int idx = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	vu_check_queue_msg_file(msg);
+
+	if (vdev->vq[idx].err_fd != -1) {
+		close(vdev->vq[idx].err_fd);
+		vdev->vq[idx].err_fd = -1;
+	}
+
+	if (!nofd)
+		vdev->vq[idx].err_fd = msg->fds[0];
+
+	return false;
+}
+
+/**
+ * vu_get_protocol_features_exec() - Provide the protocol (vhost-user) features
+ * 				     to the front-end
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: True as a reply is requested
+ */
+static bool vu_get_protocol_features_exec(struct vu_dev *vdev,
+					  struct vhost_user_msg *msg)
+{
+	uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK;
+
+	(void)vdev;
+	vmsg_set_reply_u64(msg, features);
+
+	return true;
+}
+
+/**
+ * vu_set_protocol_features_exec() - Enable protocol (vhost-user) features
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_protocol_features_exec(struct vu_dev *vdev,
+					  struct vhost_user_msg *msg)
+{
+	uint64_t features = msg->payload.u64;
+
+	debug("u64: 0x%016"PRIx64, features);
+
+	vdev->protocol_features = msg->payload.u64;
+
+	return false;
+}
+
+/**
+ * vu_get_queue_num_exec() - Tell how many queues we support
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: True as a reply is requested
+ */
+static bool vu_get_queue_num_exec(struct vu_dev *vdev,
+				  struct vhost_user_msg *msg)
+{
+	(void)vdev;
+
+	vmsg_set_reply_u64(msg, VHOST_USER_MAX_QUEUES);
+
+	return true;
+}
+
+/**
+ * vu_set_vring_enable_exec() - Enable or disable corresponding vring
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: False as no reply is requested
+ */
+static bool vu_set_vring_enable_exec(struct vu_dev *vdev,
+				     struct vhost_user_msg *msg)
+{
+	unsigned int enable = msg->payload.state.num;
+	unsigned int idx = msg->payload.state.index;
+
+	debug("State.index:  %u", idx);
+	debug("State.enable: %u", enable);
+
+	if (idx >= VHOST_USER_MAX_QUEUES)
+		die("Invalid vring_enable index: %u", idx);
+
+	vdev->vq[idx].enable = enable;
+	return false;
+}
+
+/**
+ * vu_init() - Initialize vhost-user device structure
+ * @c:		execution context
+ * @vdev:	vhost-user device
+ */
+/* cppcheck-suppress unusedFunction */
+void vu_init(struct ctx *c, struct vu_dev *vdev)
+{
+	int i;
+
+	vdev->context = c;
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+		vdev->vq[i] = (struct vu_virtq){
+			.call_fd = -1,
+			.kick_fd = -1,
+			.err_fd = -1,
+			.notification = true,
+		};
+	}
+}
+
+/**
+ * vu_cleanup() - Reset vhost-user device
+ * @vdev:	vhost-user device
+ */
+/* cppcheck-suppress unusedFunction */
+void vu_cleanup(struct vu_dev *vdev)
+{
+	unsigned int i;
+
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+		struct vu_virtq *vq = &vdev->vq[i];
+
+		vq->started = false;
+		vq->notification = true;
+
+		if (vq->call_fd != -1) {
+			close(vq->call_fd);
+			vq->call_fd = -1;
+		}
+		if (vq->err_fd != -1) {
+			close(vq->err_fd);
+			vq->err_fd = -1;
+		}
+		if (vq->kick_fd != -1) {
+			vu_remove_watch(vdev, vq->kick_fd);
+			close(vq->kick_fd);
+			vq->kick_fd = -1;
+		}
+
+		vq->vring.desc = 0;
+		vq->vring.used = 0;
+		vq->vring.avail = 0;
+	}
+
+	for (i = 0; i < vdev->nregions; i++) {
+		const struct vu_dev_region *r = &vdev->regions[i];
+		/* NOLINTNEXTLINE(performance-no-int-to-ptr) */
+		void *m = (void *)r->mmap_addr;
+
+		if (m)
+			munmap(m, r->size + r->mmap_offset);
+	}
+	vdev->nregions = 0;
+}
+
+/**
+ * vu_sock_reset() - Reset connection socket
+ * @vdev:	vhost-user device
+ */
+static void vu_sock_reset(struct vu_dev *vdev)
+{
+	/* Placeholder to add passt related code */
+	(void)vdev;
+}
+
+static bool (*vu_handle[VHOST_USER_MAX])(struct vu_dev *vdev,
+					struct vhost_user_msg *msg) = {
+	[VHOST_USER_GET_FEATURES]	   = vu_get_features_exec,
+	[VHOST_USER_SET_FEATURES]	   = vu_set_features_exec,
+	[VHOST_USER_GET_PROTOCOL_FEATURES] = vu_get_protocol_features_exec,
+	[VHOST_USER_SET_PROTOCOL_FEATURES] = vu_set_protocol_features_exec,
+	[VHOST_USER_GET_QUEUE_NUM]	   = vu_get_queue_num_exec,
+	[VHOST_USER_SET_OWNER]		   = vu_set_owner_exec,
+	[VHOST_USER_SET_MEM_TABLE]	   = vu_set_mem_table_exec,
+	[VHOST_USER_SET_VRING_NUM]	   = vu_set_vring_num_exec,
+	[VHOST_USER_SET_VRING_ADDR]	   = vu_set_vring_addr_exec,
+	[VHOST_USER_SET_VRING_BASE]	   = vu_set_vring_base_exec,
+	[VHOST_USER_GET_VRING_BASE]	   = vu_get_vring_base_exec,
+	[VHOST_USER_SET_VRING_KICK]	   = vu_set_vring_kick_exec,
+	[VHOST_USER_SET_VRING_CALL]	   = vu_set_vring_call_exec,
+	[VHOST_USER_SET_VRING_ERR]	   = vu_set_vring_err_exec,
+	[VHOST_USER_SET_VRING_ENABLE]	   = vu_set_vring_enable_exec,
+};
+
+/**
+ * vu_control_handler() - Handle control commands for vhost-user
+ * @vdev:	vhost-user device
+ * @fd:		vhost-user message socket
+ * @events:	epoll events
+ */
+/* cppcheck-suppress unusedFunction */
+void vu_control_handler(struct vu_dev *vdev, int fd, uint32_t events)
+{
+	struct vhost_user_msg msg = { 0 };
+	bool need_reply, reply_requested;
+	int ret;
+
+	if (events & (EPOLLRDHUP | EPOLLHUP | EPOLLERR)) {
+		vu_sock_reset(vdev);
+		return;
+	}
+
+	ret = vu_message_read_default(fd, &msg);
+	if (ret == 0) {
+		vu_sock_reset(vdev);
+		return;
+	}
+	debug("================ Vhost user message ================");
+	debug("Request: %s (%d)", vu_request_to_string(msg.hdr.request),
+		msg.hdr.request);
+	debug("Flags:   0x%x", msg.hdr.flags);
+	debug("Size:    %u", msg.hdr.size);
+
+	need_reply = msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK;
+
+	if (msg.hdr.request >= 0 && msg.hdr.request < VHOST_USER_MAX &&
+	    vu_handle[msg.hdr.request])
+		reply_requested = vu_handle[msg.hdr.request](vdev, &msg);
+	else
+		die("Unhandled request: %d", msg.hdr.request);
+
+	/* cppcheck-suppress legacyUninitvar */
+	if (!reply_requested && need_reply) {
+		msg.payload.u64 = 0;
+		msg.hdr.flags = 0;
+		msg.hdr.size = sizeof(msg.payload.u64);
+		msg.fd_num = 0;
+		reply_requested = true;
+	}
+
+	if (reply_requested)
+		vu_send_reply(fd, &msg);
+}
diff --git a/vhost_user.h b/vhost_user.h
new file mode 100644
index 000000000000..5af349ba58b8
--- /dev/null
+++ b/vhost_user.h
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * vhost-user API, command management and virtio interface
+ *
+ * Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ */
+
+/* some parts from subprojects/libvhost-user/libvhost-user.h */
+
+#ifndef VHOST_USER_H
+#define VHOST_USER_H
+
+#include "virtio.h"
+#include "iov.h"
+
+#define VHOST_USER_F_PROTOCOL_FEATURES 30
+
+#define VHOST_MEMORY_BASELINE_NREGIONS 8
+
+/**
+ * enum vhost_user_protocol_feature - List of available vhost-user features
+ */
+enum vhost_user_protocol_feature {
+	VHOST_USER_PROTOCOL_F_MQ = 0,
+	VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
+	VHOST_USER_PROTOCOL_F_RARP = 2,
+	VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
+	VHOST_USER_PROTOCOL_F_NET_MTU = 4,
+	VHOST_USER_PROTOCOL_F_BACKEND_REQ = 5,
+	VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
+	VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
+	VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
+	VHOST_USER_PROTOCOL_F_CONFIG = 9,
+	VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
+	VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
+	VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
+	VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
+	VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
+
+	VHOST_USER_PROTOCOL_F_MAX
+};
+
+/**
+ * enum vhost_user_request - List of available vhost-user requests
+ */
+enum vhost_user_request {
+	VHOST_USER_NONE = 0,
+	VHOST_USER_GET_FEATURES = 1,
+	VHOST_USER_SET_FEATURES = 2,
+	VHOST_USER_SET_OWNER = 3,
+	VHOST_USER_RESET_OWNER = 4,
+	VHOST_USER_SET_MEM_TABLE = 5,
+	VHOST_USER_SET_LOG_BASE = 6,
+	VHOST_USER_SET_LOG_FD = 7,
+	VHOST_USER_SET_VRING_NUM = 8,
+	VHOST_USER_SET_VRING_ADDR = 9,
+	VHOST_USER_SET_VRING_BASE = 10,
+	VHOST_USER_GET_VRING_BASE = 11,
+	VHOST_USER_SET_VRING_KICK = 12,
+	VHOST_USER_SET_VRING_CALL = 13,
+	VHOST_USER_SET_VRING_ERR = 14,
+	VHOST_USER_GET_PROTOCOL_FEATURES = 15,
+	VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+	VHOST_USER_GET_QUEUE_NUM = 17,
+	VHOST_USER_SET_VRING_ENABLE = 18,
+	VHOST_USER_SEND_RARP = 19,
+	VHOST_USER_NET_SET_MTU = 20,
+	VHOST_USER_SET_BACKEND_REQ_FD = 21,
+	VHOST_USER_IOTLB_MSG = 22,
+	VHOST_USER_SET_VRING_ENDIAN = 23,
+	VHOST_USER_GET_CONFIG = 24,
+	VHOST_USER_SET_CONFIG = 25,
+	VHOST_USER_CREATE_CRYPTO_SESSION = 26,
+	VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
+	VHOST_USER_POSTCOPY_ADVISE  = 28,
+	VHOST_USER_POSTCOPY_LISTEN  = 29,
+	VHOST_USER_POSTCOPY_END     = 30,
+	VHOST_USER_GET_INFLIGHT_FD = 31,
+	VHOST_USER_SET_INFLIGHT_FD = 32,
+	VHOST_USER_GPU_SET_SOCKET = 33,
+	VHOST_USER_VRING_KICK = 35,
+	VHOST_USER_GET_MAX_MEM_SLOTS = 36,
+	VHOST_USER_ADD_MEM_REG = 37,
+	VHOST_USER_REM_MEM_REG = 38,
+	VHOST_USER_MAX
+};
+
+/**
+ * struct vhost_user_header - vhost-user message header
+ * @request:	Request type of the message
+ * @flags:	Request flags
+ * @size:	The following payload size
+ */
+struct vhost_user_header {
+	enum vhost_user_request request;
+
+#define VHOST_USER_VERSION_MASK     0x3
+#define VHOST_USER_REPLY_MASK       (0x1 << 2)
+#define VHOST_USER_NEED_REPLY_MASK  (0x1 << 3)
+	uint32_t flags;
+	uint32_t size;
+} __attribute__ ((__packed__));
+
+/**
+ * struct vhost_user_memory_region - Front-end shared memory region information
+ * @guest_phys_addr:	Guest physical address of the region
+ * @memory_size:	Memory size
+ * @userspace_addr:	front-end (QEMU) userspace address
+ * @mmap_offset:	region offset in the shared memory area
+ */
+struct vhost_user_memory_region {
+	uint64_t guest_phys_addr;
+	uint64_t memory_size;
+	uint64_t userspace_addr;
+	uint64_t mmap_offset;
+};
+
+/**
+ * struct vhost_user_memory - List of all the shared memory regions
+ * @nregions:	Number of memory regions
+ * @padding:	Padding
+ * @regions:	Memory regions list
+ */
+struct vhost_user_memory {
+	uint32_t nregions;
+	uint32_t padding;
+	struct vhost_user_memory_region regions[VHOST_MEMORY_BASELINE_NREGIONS];
+};
+
+/**
+ * union vhost_user_payload - vhost-user message payload
+ * @u64:		64-bit payload
+ * @state:		vring state payload
+ * @addr:		vring addresses payload
+ * vhost_user_memory:	Memory regions information payload
+ */
+union vhost_user_payload {
+#define VHOST_USER_VRING_IDX_MASK   0xff
+#define VHOST_USER_VRING_NOFD_MASK  (0x1 << 8)
+	uint64_t u64;
+	struct vhost_vring_state state;
+	struct vhost_vring_addr addr;
+	struct vhost_user_memory memory;
+};
+
+/**
+ * struct vhost_user_msg - vhost-use message
+ * @hdr:		Message header
+ * @payload:		Message payload
+ * @fds:		File descriptors associated with the message
+ * 			in the ancillary data.
+ * 			(shared memory or event file descriptors)
+ * @fd_num:		Number of file descriptors
+ */
+struct vhost_user_msg {
+	struct vhost_user_header hdr;
+	union vhost_user_payload payload;
+
+	int fds[VHOST_MEMORY_BASELINE_NREGIONS];
+	int fd_num;
+} __attribute__ ((__packed__));
+#define VHOST_USER_HDR_SIZE sizeof(struct vhost_user_header)
+
+/* index of the RX virtqueue */
+#define VHOST_USER_RX_QUEUE 0
+/* index of the TX virtqueue */
+#define VHOST_USER_TX_QUEUE 1
+
+/* in case of multiqueue, the RX and TX queues are interleaved */
+#define VHOST_USER_IS_QUEUE_TX(n)	(n % 2)
+#define VHOST_USER_IS_QUEUE_RX(n)	(!(n % 2))
+
+/* Default virtio-net header for passt */
+#define VU_HEADER ((struct virtio_net_hdr){	\
+	.flags = VIRTIO_NET_HDR_F_DATA_VALID,	\
+	.gso_type = VIRTIO_NET_HDR_GSO_NONE,	\
+})
+
+/**
+ * vu_queue_enabled - Return state of a virtqueue
+ * @vq:		virtqueue to check
+ *
+ * Return: true if the virqueue is enabled, false otherwise
+ */
+/* cppcheck-suppress unusedFunction */
+static inline bool vu_queue_enabled(const struct vu_virtq *vq)
+{
+	return vq->enable;
+}
+
+/**
+ * vu_queue_started - Return state of a virtqueue
+ * @vq:		virtqueue to check
+ *
+ * Return: true if the virqueue is started, false otherwise
+ */
+/* cppcheck-suppress unusedFunction */
+static inline bool vu_queue_started(const struct vu_virtq *vq)
+{
+	return vq->started;
+}
+
+void vu_print_capabilities(void);
+void vu_init(struct ctx *c, struct vu_dev *vdev);
+void vu_cleanup(struct vu_dev *vdev);
+void vu_control_handler(struct vu_dev *vdev, int fd, uint32_t events);
+#endif /* VHOST_USER_H */
diff --git a/virtio.h b/virtio.h
index 94efeb049fbc..6410d60f9b3f 100644
--- a/virtio.h
+++ b/virtio.h
@@ -105,6 +105,7 @@ struct vu_dev_region {
  * @protocol_features:	Vhost-user protocol features
  */
 struct vu_dev {
+	struct ctx *context;
 	uint32_t nregions;
 	struct vu_dev_region regions[VHOST_USER_MAX_RAM_SLOTS];
 	struct vu_virtq vq[VHOST_USER_MAX_QUEUES];
-- 
2.47.0

Export tcp_fill_headers[4|6]() and tcp_update_check_tcp[4|6]().

They'll be needed by vhost-user.

Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>
---
 tcp.c          | 30 +++++++++++++++---------------
 tcp_internal.h | 15 +++++++++++++++
 2 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/tcp.c b/tcp.c
index 56ceba607fc9..e4dcd4601893 100644
--- a/tcp.c
+++ b/tcp.c
@@ -758,9 +758,9 @@ static void tcp_sock_set_bufsize(const struct ctx *c, int s)
  * @iov_cnt:	Length of the array
  * @l4offset:	IPv4 payload offset in the iovec array
  */
-static void tcp_update_check_tcp4(const struct iphdr *iph,
-				  const struct iovec *iov, int iov_cnt,
-				  size_t l4offset)
+void tcp_update_check_tcp4(const struct iphdr *iph,
+			   const struct iovec *iov, int iov_cnt,
+			   size_t l4offset)
 {
 	uint16_t l4len = ntohs(iph->tot_len) - sizeof(struct iphdr);
 	struct in_addr saddr = { .s_addr = iph->saddr };
@@ -810,9 +810,9 @@ static void tcp_update_check_tcp4(const struct iphdr *iph,
  * @iov_cnt:	Length of the array
  * @l4offset:	IPv6 payload offset in the iovec array
  */
-static void tcp_update_check_tcp6(const struct ipv6hdr *ip6h,
-				  const struct iovec *iov, int iov_cnt,
-				  size_t l4offset)
+void tcp_update_check_tcp6(const struct ipv6hdr *ip6h,
+			   const struct iovec *iov, int iov_cnt,
+			   size_t l4offset)
 {
 	uint16_t l4len = ntohs(ip6h->payload_len);
 	size_t check_ofs;
@@ -979,11 +979,11 @@ static void tcp_fill_header(struct tcphdr *th,
  *
  * Return: The IPv4 payload length, host order
  */
-static size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
-				struct tap_hdr *taph,
-				struct iphdr *iph, struct tcp_payload_t *bp,
-				size_t dlen, const uint16_t *check,
-				uint32_t seq, bool no_tcp_csum)
+size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
+			 struct tap_hdr *taph,
+			 struct iphdr *iph, struct tcp_payload_t *bp,
+			 size_t dlen, const uint16_t *check,
+			 uint32_t seq, bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
 	const struct in_addr *src4 = inany_v4(&tapside->oaddr);
@@ -1031,10 +1031,10 @@ static size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
  *
  * Return: The IPv6 payload length, host order
  */
-static size_t tcp_fill_headers6(const struct tcp_tap_conn *conn,
-				struct tap_hdr *taph,
-				struct ipv6hdr *ip6h, struct tcp_payload_t *bp,
-				size_t dlen, uint32_t seq, bool no_tcp_csum)
+size_t tcp_fill_headers6(const struct tcp_tap_conn *conn,
+			 struct tap_hdr *taph,
+			 struct ipv6hdr *ip6h, struct tcp_payload_t *bp,
+			 size_t dlen, uint32_t seq, bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
 	size_t l4len = dlen + sizeof(bp->th);
diff --git a/tcp_internal.h b/tcp_internal.h
index a5a47df8203d..d5d5d064f5ab 100644
--- a/tcp_internal.h
+++ b/tcp_internal.h
@@ -177,6 +177,21 @@ void tcp_rst_do(const struct ctx *c, struct tcp_tap_conn *conn);
 
 struct tcp_info_linux;
 
+void tcp_update_check_tcp4(const struct iphdr *iph,
+			   const struct iovec *iov, int iov_cnt,
+			   size_t l4offset);
+void tcp_update_check_tcp6(const struct ipv6hdr *ip6h,
+			   const struct iovec *iov, int iov_cnt,
+			   size_t l4offset);
+size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
+			 struct tap_hdr *taph,
+			 struct iphdr *iph, struct tcp_payload_t *bp,
+			 size_t dlen, const uint16_t *check,
+			 uint32_t seq, bool no_tcp_csum);
+size_t tcp_fill_headers6(const struct tcp_tap_conn *conn,
+			 struct tap_hdr *taph,
+			 struct ipv6hdr *ip6h, struct tcp_payload_t *bp,
+			 size_t dlen, uint32_t seq, bool no_tcp_csum);
 size_t tcp_l2_buf_fill_headers(const struct tcp_tap_conn *conn,
 			       struct iovec *iov, size_t dlen,
 			       const uint16_t *check, uint32_t seq,
-- 
2.47.0

add virtio and vhost-user functions to connect with QEMU.

  $ ./passt --vhost-user

and

  # qemu-system-x86_64 ... -m 4G \
        -object memory-backend-memfd,id=memfd0,share=on,size=4G \
        -numa node,memdev=memfd0 \
        -chardev socket,id=chr0,path=/tmp/passt_1.socket \
        -netdev vhost-user,id=netdev0,chardev=chr0 \
        -device virtio-net,mac=9a:2b:2c:2d:2e:2f,netdev=netdev0 \
        ...

Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
---
 Makefile     |   6 +-
 conf.c       |  21 ++-
 epoll_type.h |   4 +
 iov.c        |   1 -
 isolation.c  |  17 +-
 packet.c     |  11 ++
 packet.h     |   8 +-
 passt.1      |  10 +-
 passt.c      |   9 +
 passt.h      |   7 +
 pcap.c       |   1 -
 tap.c        |  77 ++++++--
 tap.h        |   5 +-
 tcp.c        |   7 +
 tcp_vu.c     | 515 +++++++++++++++++++++++++++++++++++++++++++++++++++
 tcp_vu.h     |  12 ++
 udp.c        |  11 ++
 udp_vu.c     | 336 +++++++++++++++++++++++++++++++++
 udp_vu.h     |  13 ++
 vhost_user.c |  47 +++--
 vhost_user.h |   4 +-
 virtio.c     |   5 -
 vu_common.c  | 285 ++++++++++++++++++++++++++++
 vu_common.h  |  60 ++++++
 24 files changed, 1416 insertions(+), 56 deletions(-)
 create mode 100644 tcp_vu.c
 create mode 100644 tcp_vu.h
 create mode 100644 udp_vu.c
 create mode 100644 udp_vu.h
 create mode 100644 vu_common.c
 create mode 100644 vu_common.h

diff --git a/Makefile b/Makefile
index f553c8da0ac0..1dc12c5cc52f 100644
--- a/Makefile
+++ b/Makefile
@@ -54,7 +54,8 @@ FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
 PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c flow.c fwd.c \
 	icmp.c igmp.c inany.c iov.c ip.c isolation.c lineread.c log.c mld.c \
 	ndp.c netlink.c packet.c passt.c pasta.c pcap.c pif.c tap.c tcp.c \
-	tcp_buf.c tcp_splice.c udp.c udp_flow.c util.c vhost_user.c virtio.c
+	tcp_buf.c tcp_splice.c tcp_vu.c udp.c udp_flow.c udp_vu.c util.c \
+	vhost_user.c virtio.c vu_common.c
 QRAP_SRCS = qrap.c
 SRCS = $(PASST_SRCS) $(QRAP_SRCS)
 
@@ -64,7 +65,8 @@ PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h flow.h
fwd.h \
 	flow_table.h icmp.h icmp_flow.h inany.h iov.h ip.h isolation.h \
 	lineread.h log.h ndp.h netlink.h packet.h passt.h pasta.h pcap.h pif.h \
 	siphash.h tap.h tcp.h tcp_buf.h tcp_conn.h tcp_internal.h tcp_splice.h \
-	udp.h udp_flow.h util.h vhost_user.h virtio.h
+	tcp_vu.h udp.h udp_flow.h udp_internal.h udp_vu.h util.h vhost_user.h \
+	virtio.h vu_common.h
 HEADERS = $(PASST_HEADERS) seccomp.h
 
 C := \#include <sys/random.h>\nint main(){int a=getrandom(0, 0, 0);}
diff --git a/conf.c b/conf.c
index 14411b4e130b..f5a87f1bb1ab 100644
--- a/conf.c
+++ b/conf.c
@@ -45,6 +45,7 @@
 #include "lineread.h"
 #include "isolation.h"
 #include "log.h"
+#include "vhost_user.h"
 
 /**
  * next_chunk - Return the next piece of a string delimited by a character
@@ -767,9 +768,14 @@ static void usage(const char *name, FILE *f, int status)
 			"    default: same interface name as external one\n");
 	} else {
 		FPRINTF(f,
-			"  -s, --socket PATH	UNIX domain socket path\n"
+			"  -s, --socket, --socket-path PATH	UNIX domain socket path\n"
 			"    default: probe free path starting from "
 			UNIX_SOCK_PATH "\n", 1);
+		fprintf(f,
+			"  --vhost-user		Enable vhost-user mode\n"
+			"    UNIX domain socket is provided by -s option\n"
+			"  --print-capabilities	print back-end capabilities in JSON format,\n"
+			"    only meaningful for vhost-user mode\n");
 	}
 
 	FPRINTF(f,
@@ -1303,6 +1309,10 @@ void conf(struct ctx *c, int argc, char **argv)
 		{"map-guest-addr", required_argument,	NULL,		22 },
 		{"host-lo-to-ns-lo", no_argument, 	NULL,		23 },
 		{"dns-host",	required_argument,	NULL,		24 },
+		{"vhost-user",	no_argument,		NULL,		25 },
+		/* vhost-user backend program convention */
+		{"print-capabilities", no_argument,	NULL,		26 },
+		{"socket-path",	required_argument,	NULL,		's' },
 		{ 0 },
 	};
 	const char *logname = (c->mode == MODE_PASTA) ? "pasta" :
"passt";
@@ -1496,6 +1506,15 @@ void conf(struct ctx *c, int argc, char **argv)
 				break;
 
 			die("Invalid host nameserver address: %s", optarg);
+		case 25:
+			if (c->mode == MODE_PASTA) {
+				err("--vhost-user is for passt mode only");
+				usage(argv[0], stdout, EXIT_SUCCESS);
+			}
+			c->mode = MODE_VU;
+			break;
+		case 26:
+			vu_print_capabilities();
 			break;
 		case 'd':
 			c->debug = 1;
diff --git a/epoll_type.h b/epoll_type.h
index 0ad1efa0ccec..f3ef41584757 100644
--- a/epoll_type.h
+++ b/epoll_type.h
@@ -36,6 +36,10 @@ enum epoll_type {
 	EPOLL_TYPE_TAP_PASST,
 	/* socket listening for qemu socket connections */
 	EPOLL_TYPE_TAP_LISTEN,
+	/* vhost-user command socket */
+	EPOLL_TYPE_VHOST_CMD,
+	/* vhost-user kick event socket */
+	EPOLL_TYPE_VHOST_KICK,
 
 	EPOLL_NUM_TYPES,
 };
diff --git a/iov.c b/iov.c
index 3f9e229a305f..3741db21790f 100644
--- a/iov.c
+++ b/iov.c
@@ -68,7 +68,6 @@ size_t iov_skip_bytes(const struct iovec *iov, size_t n,
  *
  * Returns:    The number of bytes successfully copied.
  */
-/* cppcheck-suppress unusedFunction */
 size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt,
 		    size_t offset, const void *buf, size_t bytes)
 {
diff --git a/isolation.c b/isolation.c
index 45fba1e68b9d..c944fb35c3a4 100644
--- a/isolation.c
+++ b/isolation.c
@@ -379,12 +379,21 @@ void isolate_postfork(const struct ctx *c)
 
 	prctl(PR_SET_DUMPABLE, 0);
 
-	if (c->mode == MODE_PASTA) {
-		prog.len = (unsigned short)ARRAY_SIZE(filter_pasta);
-		prog.filter = filter_pasta;
-	} else {
+	switch (c->mode) {
+	case MODE_PASST:
 		prog.len = (unsigned short)ARRAY_SIZE(filter_passt);
 		prog.filter = filter_passt;
+		break;
+	case MODE_PASTA:
+		prog.len = (unsigned short)ARRAY_SIZE(filter_pasta);
+		prog.filter = filter_pasta;
+		break;
+	case MODE_VU:
+		prog.len = (unsigned short)ARRAY_SIZE(filter_vu);
+		prog.filter = filter_vu;
+		break;
+	default:
+		ASSERT(0);
 	}
 
 	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) ||
diff --git a/packet.c b/packet.c
index 37489961a37e..e5a78d079231 100644
--- a/packet.c
+++ b/packet.c
@@ -36,6 +36,17 @@
 static int packet_check_range(const struct pool *p, size_t offset, size_t len,
 			      const char *start, const char *func, int line)
 {
+	if (p->buf_size == 0) {
+		int ret;
+
+		ret = vu_packet_check_range((void *)p->buf, offset, len, start);
+
+		if (ret == -1)
+			trace("cannot find region, %s:%i", func, line);
+
+		return ret;
+	}
+
 	if (start < p->buf) {
 		trace("packet start %p before buffer start %p, "
 		      "%s:%i", (void *)start, (void *)p->buf, func, line);
diff --git a/packet.h b/packet.h
index 8377dcf678bb..3f70e949c066 100644
--- a/packet.h
+++ b/packet.h
@@ -8,8 +8,10 @@
 
 /**
  * struct pool - Generic pool of packets stored in a buffer
- * @buf:	Buffer storing packet descriptors
- * @buf_size:	Total size of buffer
+ * @buf:	Buffer storing packet descriptors,
+ * 		a struct vu_dev_region array for passt vhost-user mode
+ * @buf_size:	Total size of buffer,
+ * 		0 for passt vhost-user mode
  * @size:	Number of usable descriptors for the pool
  * @count:	Number of used descriptors for the pool
  * @pkt:	Descriptors: see macros below
@@ -22,6 +24,8 @@ struct pool {
 	struct iovec pkt[1];
 };
 
+int vu_packet_check_range(void *buf, size_t offset, size_t len,
+			  const char *start);
 void packet_add_do(struct pool *p, size_t len, const char *start,
 		   const char *func, int line);
 void *packet_get_do(const struct pool *p, const size_t idx,
diff --git a/passt.1 b/passt.1
index f0849787217e..a100e0f1d727 100644
--- a/passt.1
+++ b/passt.1
@@ -397,12 +397,20 @@ interface address are configured on a given host interface.
 .SS \fBpasst\fR-only options
 
 .TP
-.BR \-s ", " \-\-socket " " \fIpath
+.BR \-s ", " \-\-socket-path ", " \-\-socket " " \fIpath
 Path for UNIX domain socket used by \fBqemu\fR(1) or \fBqrap\fR(1) to connect to
 \fBpasst\fR.
 Default is to probe a free socket, not accepting connections, starting from
 \fI/tmp/passt_1.socket\fR to \fI/tmp/passt_64.socket\fR.
 
+.TP
+.BR \-\-vhost-user
+Enable vhost-user. The vhost-user command socket is provided by \fB--socket\fR.
+
+.TP
+.BR \-\-print-capabilities
+Print back-end capabilities in JSON format, only meaningful for vhost-user mode.
+
 .TP
 .BR \-F ", " \-\-fd " " \fIFD
 Pass a pre-opened, connected socket to \fBpasst\fR. Usually the socket is opened
diff --git a/passt.c b/passt.c
index e6980f2c8fda..fc8f027a9de7 100644
--- a/passt.c
+++ b/passt.c
@@ -52,6 +52,7 @@
 #include "arch.h"
 #include "log.h"
 #include "tcp_splice.h"
+#include "vu_common.h"
 
 #define EPOLL_EVENTS		8
 
@@ -74,6 +75,8 @@ char *epoll_type_str[] = {
 	[EPOLL_TYPE_TAP_PASTA]		= "/dev/net/tun device",
 	[EPOLL_TYPE_TAP_PASST]		= "connected qemu socket",
 	[EPOLL_TYPE_TAP_LISTEN]		= "listening qemu socket",
+	[EPOLL_TYPE_VHOST_CMD]		= "vhost-user command socket",
+	[EPOLL_TYPE_VHOST_KICK]		= "vhost-user kick socket",
 };
 static_assert(ARRAY_SIZE(epoll_type_str) == EPOLL_NUM_TYPES,
 	      "epoll_type_str[] doesn't match enum epoll_type");
@@ -363,6 +366,12 @@ loop:
 		case EPOLL_TYPE_PING:
 			icmp_sock_handler(&c, ref);
 			break;
+		case EPOLL_TYPE_VHOST_CMD:
+			vu_control_handler(c.vdev, c.fd_tap, eventmask);
+			break;
+		case EPOLL_TYPE_VHOST_KICK:
+			vu_kick_cb(c.vdev, ref, &now);
+			break;
 		default:
 			/* Can't happen */
 			ASSERT(0);
diff --git a/passt.h b/passt.h
index 72c7f723a7bb..076f7db43345 100644
--- a/passt.h
+++ b/passt.h
@@ -25,6 +25,7 @@ union epoll_ref;
 #include "fwd.h"
 #include "tcp.h"
 #include "udp.h"
+#include "vhost_user.h"
 
 /* Default address for our end on the tap interface.  Bit 0 of byte 0 must be 0
  * (unicast) and bit 1 of byte 1 must be 1 (locally administered).  Otherwise
@@ -43,6 +44,7 @@ union epoll_ref;
  * @icmp:	ICMP-specific reference part
  * @data:	Data handled by protocol handlers
  * @nsdir_fd:	netns dirfd for fallback timer checking if namespace is gone
+ * @queue:	vhost-user queue index for this fd
  * @u64:	Opaque reference for epoll_ctl() and epoll_wait()
  */
 union epoll_ref {
@@ -58,6 +60,7 @@ union epoll_ref {
 			union udp_listen_epoll_ref udp;
 			uint32_t data;
 			int nsdir_fd;
+			int queue;
 		};
 	};
 	uint64_t u64;
@@ -94,6 +97,7 @@ struct fqdn {
 enum passt_modes {
 	MODE_PASST,
 	MODE_PASTA,
+	MODE_VU,
 };
 
 /**
@@ -229,6 +233,7 @@ struct ip6_ctx {
  * @freebind:		Allow binding of non-local addresses for forwarding
  * @low_wmem:		Low probed net.core.wmem_max
  * @low_rmem:		Low probed net.core.rmem_max
+ * @vdev:		vhost-user device
  */
 struct ctx {
 	enum passt_modes mode;
@@ -291,6 +296,8 @@ struct ctx {
 
 	int low_wmem;
 	int low_rmem;
+
+	struct vu_dev *vdev;
 };
 
 void proto_update_l2_buf(const unsigned char *eth_d,
diff --git a/pcap.c b/pcap.c
index 23205ddfed84..3d623cfead77 100644
--- a/pcap.c
+++ b/pcap.c
@@ -143,7 +143,6 @@ void pcap_multiple(const struct iovec *iov, size_t frame_parts,
unsigned int n,
  * @iovcnt:	Number of buffers (@iov entries)
  * @offset:	Offset of the L2 frame within the full data length
  */
-/* cppcheck-suppress unusedFunction */
 void pcap_iov(const struct iovec *iov, size_t iovcnt, size_t offset)
 {
 	struct timespec now = { 0 };
diff --git a/tap.c b/tap.c
index e3f992064013..3bee8bd16f8b 100644
--- a/tap.c
+++ b/tap.c
@@ -58,6 +58,8 @@
 #include "packet.h"
 #include "tap.h"
 #include "log.h"
+#include "vhost_user.h"
+#include "vu_common.h"
 
 /* IPv4 (plus ARP) and IPv6 message batches from tap/guest to IP handlers */
 static PACKET_POOL_NOINIT(pool_tap4, TAP_MSGS, pkt_buf);
@@ -78,16 +80,22 @@ void tap_send_single(const struct ctx *c, const void *data, size_t
l2len)
 	struct iovec iov[2];
 	size_t iovcnt = 0;
 
-	if (c->mode == MODE_PASST) {
+	switch (c->mode) {
+	case MODE_PASST:
 		iov[iovcnt] = IOV_OF_LVALUE(vnet_len);
 		iovcnt++;
-	}
-
-	iov[iovcnt].iov_base = (void *)data;
-	iov[iovcnt].iov_len = l2len;
-	iovcnt++;
+		/* fall through */
+	case MODE_PASTA:
+		iov[iovcnt].iov_base = (void *)data;
+		iov[iovcnt].iov_len = l2len;
+		iovcnt++;
 
-	tap_send_frames(c, iov, iovcnt, 1);
+		tap_send_frames(c, iov, iovcnt, 1);
+		break;
+	case MODE_VU:
+		vu_send_single(c, data, l2len);
+		break;
+	}
 }
 
 /**
@@ -414,10 +422,18 @@ size_t tap_send_frames(const struct ctx *c, const struct iovec
*iov,
 	if (!nframes)
 		return 0;
 
-	if (c->mode == MODE_PASTA)
+	switch (c->mode) {
+	case MODE_PASTA:
 		m = tap_send_frames_pasta(c, iov, bufs_per_frame, nframes);
-	else
+		break;
+	case MODE_PASST:
 		m = tap_send_frames_passt(c, iov, bufs_per_frame, nframes);
+		break;
+	case MODE_VU:
+		/* fall through */
+	default:
+		ASSERT(0);
+	}
 
 	if (m < nframes)
 		debug("tap: failed to send %zu frames of %zu",
@@ -976,7 +992,7 @@ void tap_add_packet(struct ctx *c, ssize_t l2len, char *p)
  * tap_sock_reset() - Handle closing or failure of connect AF_UNIX socket
  * @c:		Execution context
  */
-static void tap_sock_reset(struct ctx *c)
+void tap_sock_reset(struct ctx *c)
 {
 	info("Client connection closed%s", c->one_off ? ", exiting" :
"");
 
@@ -987,6 +1003,8 @@ static void tap_sock_reset(struct ctx *c)
 	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, c->fd_tap, NULL);
 	close(c->fd_tap);
 	c->fd_tap = -1;
+	if (c->mode == MODE_VU)
+		vu_cleanup(c->vdev);
 }
 
 /**
@@ -1206,6 +1224,11 @@ static void tap_backend_show_hints(struct ctx *c)
 		info("or qrap, for earlier qemu versions:");
 		info("    ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio");
 		break;
+	case MODE_VU:
+		info("You can start qemu with:");
+		info("    kvm ... -chardev socket,id=chr0,path=%s -netdev
vhost-user,id=netdev0,chardev=chr0 -device virtio-net,netdev=netdev0 -object
memory-backend-memfd,id=memfd0,share=on,size=$RAMSIZE -numa node,memdev=memfd0\n",
+		     c->sock_path);
+		break;
 	}
 }
 
@@ -1233,8 +1256,8 @@ static void tap_sock_unix_init(const struct ctx *c)
  */
 void tap_listen_handler(struct ctx *c, uint32_t events)
 {
-	union epoll_ref ref = { .type = EPOLL_TYPE_TAP_PASST };
 	struct epoll_event ev = { 0 };
+	union epoll_ref ref = { 0 };
 	int v = INT_MAX / 2;
 	struct ucred ucred;
 	socklen_t len;
@@ -1274,6 +1297,10 @@ void tap_listen_handler(struct ctx *c, uint32_t events)
 		trace("tap: failed to set SO_SNDBUF to %i", v);
 
 	ref.fd = c->fd_tap;
+	if (c->mode == MODE_VU)
+		ref.type = EPOLL_TYPE_VHOST_CMD;
+	else
+		ref.type = EPOLL_TYPE_TAP_PASST;
 	ev.events = EPOLLIN | EPOLLRDHUP;
 	ev.data.u64 = ref.u64;
 	epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
@@ -1340,7 +1367,7 @@ static void tap_sock_tun_init(struct ctx *c)
  * @base:	Buffer base
  * @size	Buffer size
  */
-static void tap_sock_update_pool(void *base, size_t size)
+void tap_sock_update_pool(void *base, size_t size)
 {
 	int i;
 
@@ -1360,7 +1387,10 @@ static void tap_sock_update_pool(void *base, size_t size)
  */
 void tap_backend_init(struct ctx *c)
 {
-	tap_sock_update_pool(pkt_buf, sizeof(pkt_buf));
+	if (c->mode == MODE_VU)
+		tap_sock_update_pool(NULL, 0);
+	else
+		tap_sock_update_pool(pkt_buf, sizeof(pkt_buf));
 
 	if (c->fd_tap != -1) { /* Passed as --fd */
 		struct epoll_event ev = { 0 };
@@ -1368,10 +1398,17 @@ void tap_backend_init(struct ctx *c)
 
 		ASSERT(c->one_off);
 		ref.fd = c->fd_tap;
-		if (c->mode == MODE_PASST)
+		switch (c->mode) {
+		case MODE_PASST:
 			ref.type = EPOLL_TYPE_TAP_PASST;
-		else
+			break;
+		case MODE_PASTA:
 			ref.type = EPOLL_TYPE_TAP_PASTA;
+			break;
+		case MODE_VU:
+			ref.type = EPOLL_TYPE_VHOST_CMD;
+			break;
+		}
 
 		ev.events = EPOLLIN | EPOLLRDHUP;
 		ev.data.u64 = ref.u64;
@@ -1379,9 +1416,14 @@ void tap_backend_init(struct ctx *c)
 		return;
 	}
 
-	if (c->mode == MODE_PASTA) {
+	switch (c->mode) {
+	case MODE_PASTA:
 		tap_sock_tun_init(c);
-	} else {
+		break;
+	case MODE_VU:
+		vu_init(c);
+		/* fall through */
+	case MODE_PASST:
 		tap_sock_unix_init(c);
 
 		/* In passt mode, we don't know the guest's MAC address until it
@@ -1389,6 +1431,7 @@ void tap_backend_init(struct ctx *c)
 		 * first packets will reach it.
 		 */
 		memset(&c->guest_mac, 0xff, sizeof(c->guest_mac));
+		break;
 	}
 
 	tap_backend_show_hints(c);
diff --git a/tap.h b/tap.h
index 8728cc5c09c3..dfbd8b9ebd72 100644
--- a/tap.h
+++ b/tap.h
@@ -40,7 +40,8 @@ static inline struct iovec tap_hdr_iov(const struct ctx *c,
  */
 static inline void tap_hdr_update(struct tap_hdr *thdr, size_t l2len)
 {
-	thdr->vnet_len = htonl(l2len);
+	if (thdr)
+		thdr->vnet_len = htonl(l2len);
 }
 
 void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
@@ -68,6 +69,8 @@ void tap_handler_pasta(struct ctx *c, uint32_t events,
 void tap_handler_passt(struct ctx *c, uint32_t events,
 		       const struct timespec *now);
 int tap_sock_unix_open(char *sock_path);
+void tap_sock_reset(struct ctx *c);
+void tap_sock_update_pool(void *base, size_t size);
 void tap_backend_init(struct ctx *c);
 void tap_flush_pools(void);
 void tap_handler(struct ctx *c, const struct timespec *now);
diff --git a/tcp.c b/tcp.c
index e4dcd4601893..7f30f636fa73 100644
--- a/tcp.c
+++ b/tcp.c
@@ -304,6 +304,7 @@
 #include "tcp_internal.h"
 #include "tcp_info.h"
 #include "tcp_buf.h"
+#include "tcp_vu.h"
 
 /* MSS rounding: see SET_MSS() */
 #define MSS_DEFAULT			536
@@ -1313,6 +1314,9 @@ int tcp_prepare_flags(const struct ctx *c, struct tcp_tap_conn
*conn,
 static int tcp_send_flag(const struct ctx *c, struct tcp_tap_conn *conn,
 			 int flags)
 {
+	if (c->mode == MODE_VU)
+		return tcp_vu_send_flag(c, conn, flags);
+
 	return tcp_buf_send_flag(c, conn, flags);
 }
 
@@ -1706,6 +1710,9 @@ static int tcp_sock_consume(const struct tcp_tap_conn *conn,
uint32_t ack_seq)
  */
 static int tcp_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
 {
+	if (c->mode == MODE_VU)
+		return tcp_vu_data_from_sock(c, conn);
+
 	return tcp_buf_data_from_sock(c, conn);
 }
 
diff --git a/tcp_vu.c b/tcp_vu.c
new file mode 100644
index 000000000000..44fd538628a6
--- /dev/null
+++ b/tcp_vu.c
@@ -0,0 +1,515 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* tcp_vu.c - TCP L2 vhost-user management functions
+ *
+ * Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ */
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <netinet/ip.h>
+
+#include <sys/socket.h>
+
+#include <linux/tcp.h>
+#include <linux/virtio_net.h>
+
+#include "util.h"
+#include "ip.h"
+#include "passt.h"
+#include "siphash.h"
+#include "inany.h"
+#include "vhost_user.h"
+#include "tcp.h"
+#include "pcap.h"
+#include "flow.h"
+#include "tcp_conn.h"
+#include "flow_table.h"
+#include "tcp_vu.h"
+#include "tap.h"
+#include "tcp_internal.h"
+#include "checksum.h"
+#include "vu_common.h"
+
+static struct iovec iov_vu[VIRTQUEUE_MAX_SIZE + 1];
+static struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE];
+
+/**
+ * tcp_vu_hdrlen() - return the size of the header in level 2 frame (TCP)
+ * @v6:		Set for IPv6 packet
+ *
+ * Return: Return the size of the header
+ */
+static size_t tcp_vu_hdrlen(bool v6)
+{
+	size_t hdrlen;
+
+	hdrlen = sizeof(struct virtio_net_hdr_mrg_rxbuf) +
+		 sizeof(struct ethhdr) + sizeof(struct tcphdr);
+
+	if (v6)
+		hdrlen += sizeof(struct ipv6hdr);
+	else
+		hdrlen += sizeof(struct iphdr);
+
+	return hdrlen;
+}
+
+/**
+ * tcp_vu_update_check() - Calculate TCP checksum
+ * @tapside:	Address information for one side of the flow
+ * @iov:	Pointer to the array of IO vectors
+ * @iov_used:	Length of the array
+ */
+static void tcp_vu_update_check(const struct flowside *tapside,
+			        struct iovec *iov, int iov_used)
+{
+	char *base = iov[0].iov_base;
+
+	if (inany_v4(&tapside->oaddr)) {
+		const struct iphdr *iph = vu_ip(base);
+
+		tcp_update_check_tcp4(iph, iov, iov_used,
+				      (char *)vu_payloadv4(base) - base);
+	} else {
+		const struct ipv6hdr *ip6h = vu_ip(base);
+
+		tcp_update_check_tcp6(ip6h, iov, iov_used,
+				      (char *)vu_payloadv6(base) - base);
+	}
+}
+
+/**
+ * tcp_vu_send_flag() - Send segment with flags to vhost-user (no payload)
+ * @c:		Execution context
+ * @conn:	Connection pointer
+ * @flags:	TCP flags: if not set, send segment only if ACK is due
+ *
+ * Return: negative error code on connection reset, 0 otherwise
+ */
+int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
+{
+	struct vu_dev *vdev = c->vdev;
+	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	const struct flowside *tapside = TAPFLOW(conn);
+	size_t l2len, l4len, optlen, hdrlen;
+	struct vu_virtq_element flags_elem[2];
+	struct iovec flags_iov[2];
+	struct ethhdr *eh;
+	int elem_cnt;
+	int nb_ack;
+	int ret;
+
+	hdrlen = tcp_vu_hdrlen(CONN_V6(conn));
+
+	vu_set_element(&flags_elem[0], NULL, &flags_iov[0]);
+
+	elem_cnt = vu_collect(vdev, vq, &flags_elem[0], 1,
+			      hdrlen + sizeof(struct tcp_syn_opts), NULL);
+	if (elem_cnt != 1)
+		return -1;
+
+	vu_set_vnethdr(vdev, flags_elem[0].in_sg[0].iov_base, 1);
+
+	eh = vu_eth(flags_elem[0].in_sg[0].iov_base);
+
+	memcpy(eh->h_dest, c->guest_mac, sizeof(eh->h_dest));
+	memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
+
+	if (CONN_V4(conn)) {
+		struct tcp_flags_t *tcp_flags;
+		struct iphdr *iph;
+		uint32_t seq;
+
+		eh->h_proto = htons(ETH_P_IP);
+
+		iph = vu_ip(flags_elem[0].in_sg[0].iov_base);
+		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP);
+
+		tcp_flags = vu_payloadv4(flags_elem[0].in_sg[0].iov_base);
+		memset(&tcp_flags->th, 0, sizeof(tcp_flags->th));
+		tcp_flags->th.doff = offsetof(struct tcp_flags_t, opts) / 4;
+		tcp_flags->th.ack = 1;
+
+		seq = conn->seq_to_tap;
+		ret = tcp_prepare_flags(c, conn, flags, &tcp_flags->th,
+					&tcp_flags->opts, &optlen);
+		if (ret <= 0) {
+			vu_queue_rewind(vq, 1);
+			return ret;
+		}
+
+		l4len = tcp_fill_headers4(conn, NULL, iph,
+					  (struct tcp_payload_t *)tcp_flags,
+					  optlen, NULL, seq, true);
+		l2len = sizeof(*iph);
+	} else {
+		struct tcp_flags_t *tcp_flags;
+		struct ipv6hdr *ip6h;
+		uint32_t seq;
+
+		eh->h_proto = htons(ETH_P_IPV6);
+
+		ip6h = vu_ip(flags_elem[0].in_sg[0].iov_base);
+		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP);
+
+		tcp_flags = vu_payloadv6(flags_elem[0].in_sg[0].iov_base);
+		memset(&tcp_flags->th, 0, sizeof(tcp_flags->th));
+		tcp_flags->th.doff = offsetof(struct tcp_flags_t, opts) / 4;
+		tcp_flags->th.ack = 1;
+
+		seq = conn->seq_to_tap;
+		ret = tcp_prepare_flags(c, conn, flags, &tcp_flags->th,
+					&tcp_flags->opts, &optlen);
+		if (ret <= 0) {
+			vu_queue_rewind(vq, 1);
+			return ret;
+		}
+
+		l4len = tcp_fill_headers6(conn, NULL, ip6h,
+					  (struct tcp_payload_t *)tcp_flags,
+					  optlen, seq, true);
+		l2len = sizeof(*ip6h);
+	}
+	l2len += l4len + sizeof(struct ethhdr);
+
+	flags_elem[0].in_sg[0].iov_len = l2len +
+				   sizeof(struct virtio_net_hdr_mrg_rxbuf);
+	if (*c->pcap) {
+		tcp_vu_update_check(tapside, &flags_elem[0].in_sg[0], 1);
+		pcap_iov(&flags_elem[0].in_sg[0], 1,
+			 sizeof(struct virtio_net_hdr_mrg_rxbuf));
+	}
+	nb_ack = 1;
+
+	if (flags & DUP_ACK) {
+		vu_set_element(&flags_elem[1], NULL, &flags_iov[1]);
+
+		elem_cnt = vu_collect(vdev, vq, &flags_elem[1], 1,
+				      flags_elem[0].in_sg[0].iov_len, NULL);
+		if (elem_cnt == 1) {
+			memcpy(flags_elem[1].in_sg[0].iov_base,
+			       flags_elem[0].in_sg[0].iov_base,
+			       flags_elem[0].in_sg[0].iov_len);
+			nb_ack++;
+
+			if (*c->pcap)
+				pcap_iov(&flags_elem[1].in_sg[0], 1, 0);
+		}
+	}
+
+	vu_flush(vdev, vq, flags_elem, nb_ack);
+
+	return 0;
+}
+
+/** tcp_vu_sock_recv() - Receive datastream from socket into vhost-user buffers
+ * @c:		Execution context
+ * @conn:	Connection pointer
+ * @v6:		Set for IPv6 connections
+ * @fillsize:	Number of bytes we can receive
+ * @iov_cnt:	number of iov (output)
+ *
+ * Return: Number of iov entries used to store the data
+ */
+static ssize_t tcp_vu_sock_recv(const struct ctx *c,
+				const struct tcp_tap_conn *conn, bool v6,
+				size_t fillsize, int *iov_cnt)
+{
+	struct vu_dev *vdev = c->vdev;
+	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	struct msghdr mh_sock = { 0 };
+	uint16_t mss = MSS_GET(conn);
+	int s = conn->sock;
+	size_t hdrlen;
+	int elem_cnt;
+	ssize_t ret;
+
+	*iov_cnt = 0;
+
+	hdrlen = tcp_vu_hdrlen(v6);
+
+	vu_init_elem(elem, &iov_vu[1], VIRTQUEUE_MAX_SIZE);
+
+	elem_cnt = 0;
+
+	while (fillsize > 0 && elem_cnt < VIRTQUEUE_MAX_SIZE) {
+		struct iovec *iov;
+		size_t frame_size;
+		int cnt;
+
+		if (mss > fillsize)
+			mss = fillsize;
+
+		cnt = vu_collect(vdev, vq, &elem[elem_cnt],
+				 VIRTQUEUE_MAX_SIZE - elem_cnt,
+				 mss + hdrlen, &frame_size);
+		if (cnt == 0)
+			break;
+
+		frame_size -= hdrlen;
+		iov = &elem[elem_cnt].in_sg[0];
+		iov->iov_base = (char *)iov->iov_base + hdrlen;
+		iov->iov_len -= hdrlen;
+
+		fillsize -= frame_size;
+		elem_cnt += cnt;
+
+		/* All the frames must have the same size (except the last one),
+		 * otherwise we will no able to scan the iov array
+		 * to find iov entries with headers
+		 * (headers are spread every frame_size in the the array
+		 */
+		if (frame_size < mss)
+			break;
+	}
+
+	if (peek_offset_cap) {
+		mh_sock.msg_iov = iov_vu + 1;
+		mh_sock.msg_iovlen = elem_cnt;
+	} else {
+		mh_sock.msg_iov = iov_vu;
+		mh_sock.msg_iovlen = elem_cnt + 1;
+	}
+
+	do
+		ret = recvmsg(s, &mh_sock, MSG_PEEK);
+	while (ret < 0 && errno == EINTR);
+
+	*iov_cnt = elem_cnt;
+
+	return ret;
+}
+
+/**
+ * tcp_vu_prepare() - Prepare the packet header
+ * @c:		Execution context
+ * @conn:	Connection pointer
+ * @first:	Pointer to the array of IO vectors
+ * @dlen:	Packet data length
+ * @check:	Checksum, if already known
+ */
+static void tcp_vu_prepare(const struct ctx *c,
+			   struct tcp_tap_conn *conn, struct iovec *first,
+			   size_t dlen, const uint16_t **check)
+{
+	const struct flowside *toside = TAPFLOW(conn);
+	char *base = first->iov_base;
+	struct ethhdr *eh;
+
+	/* we guess the first iovec provided by the guest can embed
+	 * all the headers needed by L2 frame
+	 */
+
+	eh = vu_eth(base);
+
+	memcpy(eh->h_dest, c->guest_mac, sizeof(eh->h_dest));
+	memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
+
+	/* initialize header */
+	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
+		struct tcp_payload_t *payload;
+		struct iphdr *iph;
+
+		ASSERT(first[0].iov_len >= sizeof(struct virtio_net_hdr_mrg_rxbuf) +
+		       sizeof(struct ethhdr) + sizeof(struct iphdr) +
+		       sizeof(struct tcphdr));
+
+		eh->h_proto = htons(ETH_P_IP);
+
+		iph = vu_ip(base);
+		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP);
+		payload = vu_payloadv4(base);
+		memset(&payload->th, 0, sizeof(payload->th));
+		payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
+		payload->th.ack = 1;
+
+		tcp_fill_headers4(conn, NULL, iph, payload, dlen,
+				  *check, conn->seq_to_tap, true);
+		*check = &iph->check;
+	} else {
+		struct tcp_payload_t *payload;
+		struct ipv6hdr *ip6h;
+
+		ASSERT(first[0].iov_len >= sizeof(struct virtio_net_hdr_mrg_rxbuf) +
+		       sizeof(struct ethhdr) + sizeof(struct ipv6hdr) +
+		       sizeof(struct tcphdr));
+
+		eh->h_proto = htons(ETH_P_IPV6);
+
+		ip6h = vu_ip(base);
+		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP);
+
+		payload = vu_payloadv6(base);
+		memset(&payload->th, 0, sizeof(payload->th));
+		payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
+		payload->th.ack = 1;
+
+		tcp_fill_headers6(conn, NULL, ip6h, payload, dlen,
+				  conn->seq_to_tap, true);
+	}
+}
+
+/**
+ * tcp_vu_data_from_sock() - Handle new data from socket, queue to vhost-user,
+ *			     in window
+ * @c:		Execution context
+ * @conn:	Connection pointer
+ *
+ * Return: Negative on connection reset, 0 otherwise
+ */
+int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
+{
+	uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap;
+	struct vu_dev *vdev = c->vdev;
+	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	const struct flowside *tapside = TAPFLOW(conn);
+	uint16_t mss = MSS_GET(conn);
+	size_t hdrlen, fillsize;
+	int i, iov_cnt, iov_used;
+	int v6 = CONN_V6(conn);
+	uint32_t already_sent = 0;
+	const uint16_t *check;
+	struct iovec *first;
+	int frame_size;
+	int num_buffers;
+	ssize_t len;
+
+	if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
+		flow_err(conn,
+			 "Got packet, but RX virtqueue not usable yet");
+		return 0;
+	}
+
+	already_sent = conn->seq_to_tap - conn->seq_ack_from_tap;
+
+	if (SEQ_LT(already_sent, 0)) {
+		/* RFC 761, section 2.1. */
+		flow_trace(conn, "ACK sequence gap: ACK for %u, sent: %u",
+			   conn->seq_ack_from_tap, conn->seq_to_tap);
+		conn->seq_to_tap = conn->seq_ack_from_tap;
+		already_sent = 0;
+		if (tcp_set_peek_offset(conn->sock, 0)) {
+			tcp_rst(c, conn);
+			return -1;
+		}
+	}
+
+	if (!wnd_scaled || already_sent >= wnd_scaled) {
+		conn_flag(c, conn, STALLED);
+		conn_flag(c, conn, ACK_FROM_TAP_DUE);
+		return 0;
+	}
+
+	/* Set up buffer descriptors we'll fill completely and partially. */
+
+	fillsize = wnd_scaled - already_sent;
+
+	iov_vu[0].iov_base = tcp_buf_discard;
+	iov_vu[0].iov_len = already_sent;
+
+	/* collect the buffers from vhost-user and fill them with the
+	 * data from the socket
+	 */
+	len = tcp_vu_sock_recv(c, conn, v6, fillsize, &iov_cnt);
+	if (len < 0) {
+		vu_queue_rewind(vq, iov_cnt);
+		if (errno != EAGAIN && errno != EWOULDBLOCK) {
+			tcp_rst(c, conn);
+			return -errno;
+		}
+		return 0;
+	}
+
+	if (!len) {
+		vu_queue_rewind(vq, iov_cnt);
+		if ((conn->events & (SOCK_FIN_RCVD | TAP_FIN_SENT)) == SOCK_FIN_RCVD) {
+			int ret = tcp_vu_send_flag(c, conn, FIN | ACK);
+			if (ret) {
+				tcp_rst(c, conn);
+				return ret;
+			}
+
+			conn_event(c, conn, TAP_FIN_SENT);
+		}
+
+		return 0;
+	}
+
+	if (!peek_offset_cap)
+		len -= already_sent;
+
+	if (len <= 0) {
+		vu_queue_rewind(vq, iov_cnt);
+		conn_flag(c, conn, STALLED);
+		return 0;
+	}
+
+	conn_flag(c, conn, ~STALLED);
+
+	/* Likely, some new data was acked too. */
+	tcp_update_seqack_wnd(c, conn, false, NULL);
+
+	/* initialize headers */
+	hdrlen = tcp_vu_hdrlen(v6);
+	iov_used = 0;
+	num_buffers = 0;
+	check = NULL;
+	frame_size = 0;
+
+	/* iov_vu is an array of buffers and the buffer size can be
+	 * smaller than the frame size we want to use but with
+	 * num_buffer we can merge several virtio iov buffers in one packet
+	 * we need only to set the packet headers in the first iov and
+	 * num_buffer to the number of iov entries
+	 */
+	for (i = 0; i < iov_cnt && len; i++) {
+
+		if (frame_size == 0)
+			first = &iov_vu[i + 1];
+
+		if (iov_vu[i + 1].iov_len > (size_t)len)
+			iov_vu[i + 1].iov_len = len;
+
+		len -= iov_vu[i + 1].iov_len;
+		iov_used++;
+
+		frame_size += iov_vu[i + 1].iov_len;
+		num_buffers++;
+
+		if (frame_size >= mss || len == 0 ||
+		    i + 1 == iov_cnt || !vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
+			if (i + 1 == iov_cnt)
+				check = NULL;
+
+			/* restore first iovec base: point to vnet header */
+			first->iov_base = (char *)first->iov_base - hdrlen;
+			first->iov_len += hdrlen;
+			vu_set_vnethdr(vdev, first->iov_base, num_buffers);
+
+			tcp_vu_prepare(c, conn, first, frame_size, &check);
+			if (*c->pcap)  {
+				tcp_vu_update_check(tapside, first, num_buffers);
+				pcap_iov(first, num_buffers,
+					 sizeof(struct virtio_net_hdr_mrg_rxbuf));
+			}
+
+			conn->seq_to_tap += frame_size;
+
+			frame_size = 0;
+			num_buffers = 0;
+		}
+	}
+
+	/* release unused buffers */
+	vu_queue_rewind(vq, iov_cnt - iov_used);
+
+	/* send packets */
+	vu_flush(vdev, vq, elem, iov_used);
+
+	conn_flag(c, conn, ACK_FROM_TAP_DUE);
+
+	return 0;
+}
diff --git a/tcp_vu.h b/tcp_vu.h
new file mode 100644
index 000000000000..6ab6057f352a
--- /dev/null
+++ b/tcp_vu.h
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ */
+
+#ifndef TCP_VU_H
+#define TCP_VU_H
+
+int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags);
+int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn);
+
+#endif  /*TCP_VU_H */
diff --git a/udp.c b/udp.c
index 85952e509e55..323b31e3c9a4 100644
--- a/udp.c
+++ b/udp.c
@@ -110,6 +110,7 @@
 #include "log.h"
 #include "flow_table.h"
 #include "udp_internal.h"
+#include "udp_vu.h"
 
 /* "Spliced" sockets indexed by bound port (host order) */
 static int udp_splice_ns  [IP_VERSIONS][NUM_PORTS];
@@ -628,6 +629,11 @@ void udp_listen_sock_handler(const struct ctx *c,
 			     union epoll_ref ref, uint32_t events,
 			     const struct timespec *now)
 {
+	if (c->mode == MODE_VU) {
+		udp_vu_listen_sock_handler(c, ref, events, now);
+		return;
+	}
+
 	udp_buf_listen_sock_handler(c, ref, events, now);
 }
 
@@ -697,6 +703,11 @@ static void udp_buf_reply_sock_handler(const struct ctx *c, union
epoll_ref ref,
 void udp_reply_sock_handler(const struct ctx *c, union epoll_ref ref,
 			    uint32_t events, const struct timespec *now)
 {
+	if (c->mode == MODE_VU) {
+		udp_vu_reply_sock_handler(c, ref, events, now);
+		return;
+	}
+
 	udp_buf_reply_sock_handler(c, ref, events, now);
 }
 
diff --git a/udp_vu.c b/udp_vu.c
new file mode 100644
index 000000000000..863b6dac0682
--- /dev/null
+++ b/udp_vu.c
@@ -0,0 +1,336 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* udp_vu.c - UDP L2 vhost-user management functions
+ *
+ * Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ */
+
+#include <unistd.h>
+#include <assert.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/udp.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <sys/uio.h>
+#include <linux/virtio_net.h>
+
+#include "checksum.h"
+#include "util.h"
+#include "ip.h"
+#include "siphash.h"
+#include "inany.h"
+#include "passt.h"
+#include "pcap.h"
+#include "log.h"
+#include "vhost_user.h"
+#include "udp_internal.h"
+#include "flow.h"
+#include "flow_table.h"
+#include "udp_flow.h"
+#include "udp_vu.h"
+#include "vu_common.h"
+
+static struct iovec     iov_vu		[VIRTQUEUE_MAX_SIZE];
+static struct vu_virtq_element	elem		[VIRTQUEUE_MAX_SIZE];
+
+/**
+ * udp_vu_hdrlen() - return the size of the header in level 2 frame (UDP)
+ * @v6:		Set for IPv6 packet
+ *
+ * Return: Return the size of the header
+ */
+static size_t udp_vu_hdrlen(bool v6)
+{
+	size_t hdrlen;
+
+	hdrlen = sizeof(struct virtio_net_hdr_mrg_rxbuf) +
+		 sizeof(struct ethhdr) + sizeof(struct udphdr);
+
+	if (v6)
+		hdrlen += sizeof(struct ipv6hdr);
+	else
+		hdrlen += sizeof(struct iphdr);
+
+	return hdrlen;
+}
+
+static int udp_vu_sock_init(int s, union sockaddr_inany *s_in)
+{
+	struct msghdr msg = {
+		.msg_name = s_in,
+		.msg_namelen = sizeof(union sockaddr_inany),
+	};
+
+	return recvmsg(s, &msg, MSG_PEEK | MSG_DONTWAIT);
+}
+
+/**
+ * udp_vu_sock_recv() - Receive datagrams from socket into vhost-user buffers
+ * @c:		Execution context
+ * @s:		Socket to receive from
+ * @events:	epoll events bitmap
+ * @v6:		Set for IPv6 connections
+ * @dlen:	Size of received data (output)
+ *
+ * Return: Number of iov entries used to store the datagram
+ */
+static int udp_vu_sock_recv(const struct ctx *c, int s, uint32_t events,
+			    bool v6, ssize_t *dlen)
+{
+	struct vu_dev *vdev = c->vdev;
+	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	int iov_cnt, idx, iov_used;
+	struct msghdr msg  = { 0 };
+	size_t off, hdrlen;
+
+	ASSERT(!c->no_udp);
+
+	if (!(events & EPOLLIN))
+		return 0;
+
+	/* compute L2 header length */
+	hdrlen = udp_vu_hdrlen(v6);
+
+	vu_init_elem(elem, iov_vu, VIRTQUEUE_MAX_SIZE);
+
+	iov_cnt = vu_collect(vdev, vq, elem, VIRTQUEUE_MAX_SIZE,
+			     IP_MAX_MTU - sizeof(struct udphdr) + hdrlen,
+			     NULL);
+	if (iov_cnt == 0)
+		return 0;
+
+	/* reserve space for the headers */
+	iov_vu[0].iov_base = (char *)iov_vu[0].iov_base + hdrlen;
+	iov_vu[0].iov_len -= hdrlen;
+
+	/* read data from the socket */
+	msg.msg_iov = iov_vu;
+	msg.msg_iovlen = iov_cnt;
+
+	*dlen = recvmsg(s, &msg, 0);
+	if (*dlen < 0) {
+		vu_queue_rewind(vq, iov_cnt);
+		return 0;
+	}
+
+	/* restore the pointer to the headers address */
+	iov_vu[0].iov_base = (char *)iov_vu[0].iov_base - hdrlen;
+	iov_vu[0].iov_len += hdrlen;
+
+	/* count the numbers of buffer filled by recvmsg() */
+	idx = iov_skip_bytes(iov_vu, iov_cnt, *dlen + hdrlen, &off);
+
+	/* adjust last iov length */
+	if (idx < iov_cnt)
+		iov_vu[idx].iov_len = off;
+	iov_used = idx + !!off;
+
+	vu_set_vnethdr(vdev, iov_vu[0].iov_base, iov_used);
+
+	/* release unused buffers */
+	vu_queue_rewind(vq, iov_cnt - iov_used);
+
+	return iov_used;
+}
+
+/**
+ * udp_vu_prepare() - Prepare the packet header
+ * @c:		Execution context
+ * @toside:	Address information for one side of the flow
+ * @dlen:	Packet data length
+ *
+ * Return: Layer-4 length
+ */
+static size_t udp_vu_prepare(const struct ctx *c,
+			     const struct flowside *toside, ssize_t dlen)
+{
+	struct ethhdr *eh;
+	size_t l4len;
+
+	/* ethernet header */
+	eh = vu_eth(iov_vu[0].iov_base);
+
+	memcpy(eh->h_dest, c->guest_mac, sizeof(eh->h_dest));
+	memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
+
+	/* initialize header */
+	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
+		struct iphdr *iph = vu_ip(iov_vu[0].iov_base);
+		struct udp_payload_t *bp = vu_payloadv4(iov_vu[0].iov_base);
+
+		eh->h_proto = htons(ETH_P_IP);
+
+		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_UDP);
+
+		l4len = udp_update_hdr4(iph, bp, toside, dlen, true);
+	} else {
+		struct ipv6hdr *ip6h = vu_ip(iov_vu[0].iov_base);
+		struct udp_payload_t *bp = vu_payloadv6(iov_vu[0].iov_base);
+
+		eh->h_proto = htons(ETH_P_IPV6);
+
+		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_UDP);
+
+		l4len = udp_update_hdr6(ip6h, bp, toside, dlen, true);
+	}
+
+	return l4len;
+}
+
+/**
+ * udp_vu_csum() - Calculate and set checksum for a UDP packet
+ * @toside:	ddress information for one side of the flow
+ * @l4len:	IPv4 Payload length
+ * @iov_used:	Length of the array
+ */
+static void udp_vu_csum(const struct flowside *toside, int iov_used)
+{
+	const struct in_addr *src4 = inany_v4(&toside->oaddr);
+	const struct in_addr *dst4 = inany_v4(&toside->eaddr);
+	char *base = iov_vu[0].iov_base;
+	struct udp_payload_t *bp;
+
+	if (src4 && dst4) {
+		bp = vu_payloadv4(base);
+		csum_udp4(&bp->uh, *src4, *dst4, iov_vu, iov_used,
+			  (char *)&bp->data - base);
+	} else {
+		bp = vu_payloadv6(base);
+		csum_udp6(&bp->uh, &toside->oaddr.a6, &toside->eaddr.a6,
+			  iov_vu, iov_used, (char *)&bp->data - base);
+	}
+}
+
+/**
+ * udp_vu_listen_sock_handler() - Handle new data from socket
+ * @c:		Execution context
+ * @ref:	epoll reference
+ * @events:	epoll events bitmap
+ * @now:	Current timestamp
+ */
+void udp_vu_listen_sock_handler(const struct ctx *c, union epoll_ref ref,
+				uint32_t events, const struct timespec *now)
+{
+	struct vu_dev *vdev = c->vdev;
+	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	int i;
+
+	if (udp_sock_errs(c, ref.fd, events) < 0) {
+		err("UDP: Unrecoverable error on listening socket:"
+		    " (%s port %hu)", pif_name(ref.udp.pif), ref.udp.port);
+		return;
+	}
+
+	for (i = 0; i < UDP_MAX_FRAMES; i++) {
+		const struct flowside *toside;
+		union sockaddr_inany s_in;
+		flow_sidx_t sidx;
+		uint8_t pif;
+		ssize_t dlen;
+		int iov_used;
+		bool v6;
+
+		if (udp_vu_sock_init(ref.fd, &s_in) < 0)
+			break;
+
+		sidx = udp_flow_from_sock(c, ref, &s_in, now);
+		pif = pif_at_sidx(sidx);
+
+		if (pif != PIF_TAP) {
+			if (flow_sidx_valid(sidx)) {
+				flow_sidx_t fromsidx = flow_sidx_opposite(sidx);
+				struct udp_flow *uflow = udp_at_sidx(sidx);
+
+				flow_err(uflow,
+					"No support for forwarding UDP from %s to %s",
+					pif_name(pif_at_sidx(fromsidx)),
+					pif_name(pif));
+			} else {
+				debug("Discarding 1 datagram without flow");
+			}
+
+			continue;
+		}
+
+		toside = flowside_at_sidx(sidx);
+
+		v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr));
+
+		iov_used = udp_vu_sock_recv(c, ref.fd, events, v6, &dlen);
+		if (iov_used <= 0)
+			break;
+
+		udp_vu_prepare(c, toside, dlen);
+		if (*c->pcap) {
+			udp_vu_csum(toside, iov_used);
+			pcap_iov(iov_vu, iov_used,
+				 sizeof(struct virtio_net_hdr_mrg_rxbuf));
+		}
+		vu_flush(vdev, vq, elem, iov_used);
+	}
+}
+
+/**
+ * udp_vu_reply_sock_handler() - Handle new data from flow specific socket
+ * @c:		Execution context
+ * @ref:	epoll reference
+ * @events:	epoll events bitmap
+ * @now:	Current timestamp
+ */
+void udp_vu_reply_sock_handler(const struct ctx *c, union epoll_ref ref,
+			        uint32_t events, const struct timespec *now)
+{
+	flow_sidx_t tosidx = flow_sidx_opposite(ref.flowside);
+	const struct flowside *toside = flowside_at_sidx(tosidx);
+	struct udp_flow *uflow = udp_at_sidx(ref.flowside);
+	int from_s = uflow->s[ref.flowside.sidei];
+	struct vu_dev *vdev = c->vdev;
+	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	int i;
+
+	ASSERT(!c->no_udp);
+
+	if (udp_sock_errs(c, from_s, events) < 0) {
+		flow_err(uflow, "Unrecoverable error on reply socket");
+		flow_err_details(uflow);
+		udp_flow_close(c, uflow);
+		return;
+	}
+
+	for (i = 0; i < UDP_MAX_FRAMES; i++) {
+		uint8_t topif = pif_at_sidx(tosidx);
+		ssize_t dlen;
+		int iov_used;
+		bool v6;
+
+		ASSERT(uflow);
+
+		if (topif != PIF_TAP) {
+			uint8_t frompif = pif_at_sidx(ref.flowside);
+
+			flow_err(uflow,
+				 "No support for forwarding UDP from %s to %s",
+				 pif_name(frompif), pif_name(topif));
+			continue;
+		}
+
+		v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr));
+
+		iov_used = udp_vu_sock_recv(c, from_s, events, v6, &dlen);
+		if (iov_used <= 0)
+			break;
+		flow_trace(uflow, "Received 1 datagram on reply socket");
+		uflow->ts = now->tv_sec;
+
+		udp_vu_prepare(c, toside, dlen);
+		if (*c->pcap) {
+			udp_vu_csum(toside, iov_used);
+			pcap_iov(iov_vu, iov_used,
+				 sizeof(struct virtio_net_hdr_mrg_rxbuf));
+		}
+		vu_flush(vdev, vq, elem, iov_used);
+	}
+}
diff --git a/udp_vu.h b/udp_vu.h
new file mode 100644
index 000000000000..ba7018d3bf01
--- /dev/null
+++ b/udp_vu.h
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ */
+
+#ifndef UDP_VU_H
+#define UDP_VU_H
+
+void udp_vu_listen_sock_handler(const struct ctx *c, union epoll_ref ref,
+				uint32_t events, const struct timespec *now);
+void udp_vu_reply_sock_handler(const struct ctx *c, union epoll_ref ref,
+			       uint32_t events, const struct timespec *now);
+#endif /* UDP_VU_H */
diff --git a/vhost_user.c b/vhost_user.c
index 1e302926b8fe..25cdbbe25ea3 100644
--- a/vhost_user.c
+++ b/vhost_user.c
@@ -48,12 +48,13 @@
 /* vhost-user version we are compatible with */
 #define VHOST_USER_VERSION 1
 
+static struct vu_dev vdev_storage;
+
 /**
  * vu_print_capabilities() - print vhost-user capabilities
  * 			     this is part of the vhost-user backend
  * 			     convention.
  */
-/* cppcheck-suppress unusedFunction */
 void vu_print_capabilities(void)
 {
 	info("{");
@@ -163,9 +164,7 @@ static void vmsg_close_fds(const struct vhost_user_msg *vmsg)
  */
 static void vu_remove_watch(const struct vu_dev *vdev, int fd)
 {
-	/* Placeholder to add passt related code */
-	(void)vdev;
-	(void)fd;
+	epoll_ctl(vdev->context->epollfd, EPOLL_CTL_DEL, fd, NULL);
 }
 
 /**
@@ -487,6 +486,14 @@ static bool vu_set_mem_table_exec(struct vu_dev *vdev,
 		}
 	}
 
+	/* As vu_packet_check_range() has no access to the number of
+	 * memory regions, mark the end of the array with mmap_addr = 0
+	 */
+	ASSERT(vdev->nregions < VHOST_USER_MAX_RAM_SLOTS - 1);
+	vdev->regions[vdev->nregions].mmap_addr = 0;
+
+	tap_sock_update_pool(vdev->regions, 0);
+
 	return false;
 }
 
@@ -611,13 +618,20 @@ static bool vu_get_vring_base_exec(struct vu_dev *vdev,
 /**
  * vu_set_watch() - Add a file descriptor to the passt epoll file descriptor
  * @vdev:	vhost-user device
- * @fd:		file descriptor to add
+ * @idx:	queue index of the file descriptor to add
  */
-static void vu_set_watch(const struct vu_dev *vdev, int fd)
+static void vu_set_watch(const struct vu_dev *vdev, int idx)
 {
-	/* Placeholder to add passt related code */
-	(void)vdev;
-	(void)fd;
+	union epoll_ref ref = {
+		.type = EPOLL_TYPE_VHOST_KICK,
+		.fd = vdev->vq[idx].kick_fd,
+		.queue = idx
+	 };
+	struct epoll_event ev = { 0 };
+
+	ev.data.u64 = ref.u64;
+	ev.events = EPOLLIN;
+	epoll_ctl(vdev->context->epollfd, EPOLL_CTL_ADD, ref.fd, &ev);
 }
 
 /**
@@ -674,7 +688,7 @@ static bool vu_set_vring_kick_exec(struct vu_dev *vdev,
 	vdev->vq[idx].started = true;
 
 	if (vdev->vq[idx].kick_fd != -1 && VHOST_USER_IS_QUEUE_TX(idx)) {
-		vu_set_watch(vdev, vdev->vq[idx].kick_fd);
+		vu_set_watch(vdev, idx);
 		debug("Waiting for kicks on fd: %d for vq: %d",
 		      vdev->vq[idx].kick_fd, idx);
 	}
@@ -829,14 +843,14 @@ static bool vu_set_vring_enable_exec(struct vu_dev *vdev,
  * @c:		execution context
  * @vdev:	vhost-user device
  */
-/* cppcheck-suppress unusedFunction */
-void vu_init(struct ctx *c, struct vu_dev *vdev)
+void vu_init(struct ctx *c)
 {
 	int i;
 
-	vdev->context = c;
+	c->vdev = &vdev_storage;
+	c->vdev->context = c;
 	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
-		vdev->vq[i] = (struct vu_virtq){
+		c->vdev->vq[i] = (struct vu_virtq){
 			.call_fd = -1,
 			.kick_fd = -1,
 			.err_fd = -1,
@@ -849,7 +863,6 @@ void vu_init(struct ctx *c, struct vu_dev *vdev)
  * vu_cleanup() - Reset vhost-user device
  * @vdev:	vhost-user device
  */
-/* cppcheck-suppress unusedFunction */
 void vu_cleanup(struct vu_dev *vdev)
 {
 	unsigned int i;
@@ -896,8 +909,7 @@ void vu_cleanup(struct vu_dev *vdev)
  */
 static void vu_sock_reset(struct vu_dev *vdev)
 {
-	/* Placeholder to add passt related code */
-	(void)vdev;
+	tap_sock_reset(vdev->context);
 }
 
 static bool (*vu_handle[VHOST_USER_MAX])(struct vu_dev *vdev,
@@ -925,7 +937,6 @@ static bool (*vu_handle[VHOST_USER_MAX])(struct vu_dev *vdev,
  * @fd:		vhost-user message socket
  * @events:	epoll events
  */
-/* cppcheck-suppress unusedFunction */
 void vu_control_handler(struct vu_dev *vdev, int fd, uint32_t events)
 {
 	struct vhost_user_msg msg = { 0 };
diff --git a/vhost_user.h b/vhost_user.h
index 5af349ba58b8..464ba21e962f 100644
--- a/vhost_user.h
+++ b/vhost_user.h
@@ -183,7 +183,6 @@ struct vhost_user_msg {
  *
  * Return: true if the virqueue is enabled, false otherwise
  */
-/* cppcheck-suppress unusedFunction */
 static inline bool vu_queue_enabled(const struct vu_virtq *vq)
 {
 	return vq->enable;
@@ -195,14 +194,13 @@ static inline bool vu_queue_enabled(const struct vu_virtq *vq)
  *
  * Return: true if the virqueue is started, false otherwise
  */
-/* cppcheck-suppress unusedFunction */
 static inline bool vu_queue_started(const struct vu_virtq *vq)
 {
 	return vq->started;
 }
 
 void vu_print_capabilities(void);
-void vu_init(struct ctx *c, struct vu_dev *vdev);
+void vu_init(struct ctx *c);
 void vu_cleanup(struct vu_dev *vdev);
 void vu_control_handler(struct vu_dev *vdev, int fd, uint32_t events);
 #endif /* VHOST_USER_H */
diff --git a/virtio.c b/virtio.c
index 380590afbca3..0598ff479858 100644
--- a/virtio.c
+++ b/virtio.c
@@ -328,7 +328,6 @@ static bool vring_can_notify(const struct vu_dev *dev, struct vu_virtq
*vq)
  * @dev:	Vhost-user device
  * @vq:		Virtqueue
  */
-/* cppcheck-suppress unusedFunction */
 void vu_queue_notify(const struct vu_dev *dev, struct vu_virtq *vq)
 {
 	if (!vq->vring.avail)
@@ -504,7 +503,6 @@ static int vu_queue_map_desc(struct vu_dev *dev, struct vu_virtq *vq,
unsigned i
  *
  * Return: -1 if there is an error, 0 otherwise
  */
-/* cppcheck-suppress unusedFunction */
 int vu_queue_pop(struct vu_dev *dev, struct vu_virtq *vq, struct vu_virtq_element *elem)
 {
 	unsigned int head;
@@ -565,7 +563,6 @@ void vu_queue_unpop(struct vu_virtq *vq)
  * @vq:		Virtqueue
  * @num:	Number of element to unpop
  */
-/* cppcheck-suppress unusedFunction */
 bool vu_queue_rewind(struct vu_virtq *vq, unsigned int num)
 {
 	if (num > vq->inuse)
@@ -621,7 +618,6 @@ void vu_queue_fill_by_index(struct vu_virtq *vq, unsigned int index,
  * @len:	Size of the element
  * @idx:	Used ring entry index
  */
-/* cppcheck-suppress unusedFunction */
 void vu_queue_fill(struct vu_virtq *vq, const struct vu_virtq_element *elem,
 		   unsigned int len, unsigned int idx)
 {
@@ -645,7 +641,6 @@ static inline void vring_used_idx_set(struct vu_virtq *vq, uint16_t
val)
  * @vq:		Virtqueue
  * @count:	Number of entry to flush
  */
-/* cppcheck-suppress unusedFunction */
 void vu_queue_flush(struct vu_virtq *vq, unsigned int count)
 {
 	uint16_t old, new;
diff --git a/vu_common.c b/vu_common.c
new file mode 100644
index 000000000000..3f176ffea831
--- /dev/null
+++ b/vu_common.c
@@ -0,0 +1,285 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ *
+ * common_vu.c - vhost-user common UDP and TCP functions
+ */
+
+#include <unistd.h>
+#include <sys/uio.h>
+#include <sys/eventfd.h>
+#include <linux/virtio_net.h>
+
+#include "util.h"
+#include "passt.h"
+#include "tap.h"
+#include "vhost_user.h"
+#include "pcap.h"
+#include "vu_common.h"
+
+/**
+ * vu_packet_check_range() - Check if a given memory zone is contained in
+ * 			     a mapped guest memory region
+ * @buf:	Array of the available memory regions
+ * @offset:	Offset of data range in packet descriptor
+ * @size:	Length of desired data range
+ * @start:	Start of the packet descriptor
+ *
+ * Return: 0 if the zone is in a mapped memory region, -1 otherwise
+ */
+int vu_packet_check_range(void *buf, size_t offset, size_t len,
+			  const char *start)
+{
+	struct vu_dev_region *dev_region;
+
+	for (dev_region = buf; dev_region->mmap_addr; dev_region++) {
+		/* NOLINTNEXTLINE(performance-no-int-to-ptr) */
+		char *m = (char *)dev_region->mmap_addr;
+
+		if (m <= start &&
+		    start + offset + len <= m + dev_region->mmap_offset +
+					       dev_region->size)
+			return 0;
+	}
+
+	return -1;
+}
+
+/**
+ * vu_init_elem() - initialize an array of virtqueue element with 1 iov in each
+ * @elem:	Array of virtqueue element to initialize
+ * @iov:	Array of iovec to assign to virtqueue element
+ * @elem_cnt:	Number of virtqueue element
+ */
+void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov, int elem_cnt)
+{
+	int i;
+
+	for (i = 0; i < elem_cnt; i++)
+		vu_set_element(&elem[i], NULL, &iov[i]);
+}
+
+/**
+ * vu_collect() - collect virtio buffers from a given virtqueue
+ * @vdev:		vhost-user device
+ * @vq:			virtqueue to collect from
+ * @elem:		Array of virtqueue element
+ * 			each element must be initialized with one iovec entry
+ * 			in the in_sg array.
+ * @max_elem:		Number of virtqueue element in the array
+ * @size:		Maximum size of the data in the frame
+ * @frame_size:		The total size of the frame (output)
+ *
+ * Return: number of element used to contain the frame
+ */
+int vu_collect(struct vu_dev *vdev, struct vu_virtq *vq,
+	       struct vu_virtq_element *elem, int max_elem,
+	       size_t size, size_t *frame_size)
+{
+	size_t current_size = 0;
+	int elem_cnt = 0;
+
+	while (current_size < size && elem_cnt < max_elem) {
+		struct iovec *iov;
+		int ret;
+
+		ret = vu_queue_pop(vdev, vq, &elem[elem_cnt]);
+		if (ret < 0)
+			break;
+
+		if (elem[elem_cnt].in_num < 1) {
+			warn("virtio-net receive queue contains no in buffers");
+			vu_queue_detach_element(vq);
+			break;
+		}
+
+		iov = &elem[elem_cnt].in_sg[0];
+
+		if (iov->iov_len > size - current_size)
+			iov->iov_len = size - current_size;
+
+		current_size += iov->iov_len;
+		elem_cnt++;
+
+		if (!vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
+			break;
+	}
+
+	if (frame_size)
+		*frame_size = current_size;
+
+	return elem_cnt;
+}
+
+/**
+ * vu_set_vnethdr() - set virtio-net headers
+ * @vdev:		vhost-user device
+ * @vnethdr:		Address of the header to set
+ * @num_buffers:	Number of guest buffers of the frame
+ */
+void vu_set_vnethdr(const struct vu_dev *vdev,
+		    struct virtio_net_hdr_mrg_rxbuf *vnethdr,
+		    int num_buffers)
+{
+	vnethdr->hdr = VU_HEADER;
+	if (vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
+		vnethdr->num_buffers = htole16(num_buffers);
+}
+
+/**
+ * vu_flush() - flush all the collected buffers to the vhost-user interface
+ * @vdev:	vhost-user device
+ * @vq:		vhost-user virtqueue
+ * @elem:	virtqueue element array to send back to the virqueue
+ * @iov_used:	Length of the array
+ */
+void vu_flush(const struct vu_dev *vdev, struct vu_virtq *vq,
+	      struct vu_virtq_element *elem, int elem_cnt)
+{
+	int i;
+
+	for (i = 0; i < elem_cnt; i++)
+		vu_queue_fill(vq, &elem[i], elem[i].in_sg[0].iov_len, i);
+
+	vu_queue_flush(vq, elem_cnt);
+	vu_queue_notify(vdev, vq);
+}
+
+/**
+ * vu_handle_tx() - Receive data from the TX virtqueue
+ * @vdev:	vhost-user device
+ * @index:	index of the virtqueue
+ * @now:	Current timestamp
+ */
+static void vu_handle_tx(struct vu_dev *vdev, int index,
+			 const struct timespec *now)
+{
+	struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE];
+	struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
+	struct vu_virtq *vq = &vdev->vq[index];
+	int hdrlen = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+	int out_sg_count;
+	int count;
+
+	if (!VHOST_USER_IS_QUEUE_TX(index)) {
+		debug("vhost-user: index %d is not a TX queue", index);
+		return;
+	}
+
+	tap_flush_pools();
+
+	count = 0;
+	out_sg_count = 0;
+	while (count < VIRTQUEUE_MAX_SIZE) {
+		int ret;
+
+		vu_set_element(&elem[count], &out_sg[out_sg_count], NULL);
+		ret = vu_queue_pop(vdev, vq, &elem[count]);
+		if (ret < 0)
+			break;
+		out_sg_count += elem[count].out_num;
+
+		if (elem[count].out_num < 1) {
+			warn("virtio-net transmit queue contains no out buffers");
+			break;
+		}
+		ASSERT(elem[count].out_num == 1);
+
+		tap_add_packet(vdev->context,
+			       elem[count].out_sg[0].iov_len - hdrlen,
+			       (char *)elem[count].out_sg[0].iov_base + hdrlen);
+		count++;
+	}
+	tap_handler(vdev->context, now);
+
+	if (count) {
+		int i;
+
+		for (i = 0; i < count; i++)
+			vu_queue_fill(vq, &elem[i], 0, i);
+		vu_queue_flush(vq, count);
+		vu_queue_notify(vdev, vq);
+	}
+}
+
+/**
+ * vu_kick_cb() - Called on a kick event to start to receive data
+ * @vdev:	vhost-user device
+ * @ref:	epoll reference information
+ * @now:	Current timestamp
+ */
+void vu_kick_cb(struct vu_dev *vdev, union epoll_ref ref,
+		const struct timespec *now)
+{
+	eventfd_t kick_data;
+	ssize_t rc;
+
+	rc = eventfd_read(ref.fd, &kick_data);
+	if (rc == -1)
+		die_perror("vhost-user kick eventfd_read()");
+
+	debug("vhost-user: ot kick_data: %016"PRIx64" idx:%d",
+	      kick_data, ref.queue);
+	if (VHOST_USER_IS_QUEUE_TX(ref.queue))
+		vu_handle_tx(vdev, ref.queue, now);
+}
+
+/**
+ * vu_send_single() - Send a buffer to the front-end using the RX virtqueue
+ * @c:		execution context
+ * @buf:	address of the buffer
+ * @size:	size of the buffer
+ *
+ * Return: number of bytes sent, -1 if there is an error
+ */
+int vu_send_single(const struct ctx *c, const void *buf, size_t size)
+{
+	struct vu_dev *vdev = c->vdev;
+	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE];
+	struct iovec in_sg[VIRTQUEUE_MAX_SIZE];
+	size_t total;
+	int elem_cnt;
+	int i;
+
+	debug("vu_send_single size %zu", size);
+
+	if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
+		err("Got packet, but RX virtqueue not usable yet");
+		return 0;
+	}
+
+	vu_init_elem(elem, in_sg, VIRTQUEUE_MAX_SIZE);
+
+	size += sizeof(struct virtio_net_hdr_mrg_rxbuf);
+	elem_cnt = vu_collect(vdev, vq, elem, VIRTQUEUE_MAX_SIZE, size, &total);
+	if (total < size) {
+		debug("vu_send_single: no space to send the data "
+		      "elem_cnt %d size %zd", elem_cnt, total);
+		goto err;
+	}
+
+	vu_set_vnethdr(vdev, in_sg[0].iov_base, elem_cnt);
+
+	total -= sizeof(struct virtio_net_hdr_mrg_rxbuf);
+
+	/* copy data from the buffer to the iovec */
+	iov_from_buf(in_sg, elem_cnt, sizeof(struct virtio_net_hdr_mrg_rxbuf),
+		     buf, total);
+
+	if (*c->pcap) {
+		pcap_iov(in_sg, elem_cnt,
+			 sizeof(struct virtio_net_hdr_mrg_rxbuf));
+	}
+
+	vu_flush(vdev, vq, elem, elem_cnt);
+
+	debug("vhost-user sent %zu", total);
+
+	return total;
+err:
+	for (i = 0; i < elem_cnt; i++)
+		vu_queue_detach_element(vq);
+
+	return -1;
+}
diff --git a/vu_common.h b/vu_common.h
new file mode 100644
index 000000000000..901d97216c67
--- /dev/null
+++ b/vu_common.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright Red Hat
+ * Author: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
+ *
+ * vhost-user common UDP and TCP functions
+ */
+
+#ifndef VU_COMMON_H
+#define VU_COMMON_H
+#include <linux/virtio_net.h>
+
+static inline void *vu_eth(void *base)
+{
+	return ((char *)base + sizeof(struct virtio_net_hdr_mrg_rxbuf));
+}
+
+static inline void *vu_ip(void *base)
+{
+	return (struct ethhdr *)vu_eth(base) + 1;
+}
+
+static inline void *vu_payloadv4(void *base)
+{
+	return (struct iphdr *)vu_ip(base) + 1;
+}
+
+static inline void *vu_payloadv6(void *base)
+{
+	return (struct ipv6hdr *)vu_ip(base) + 1;
+}
+
+/**
+ * vu_set_element() - Initialize a vu_virtq_element
+ * @elem:	Element to initialize
+ * @out_sg:	One out iovec entry to set in elem
+ * @in_sg:	One in iovec entry to set in elem
+ */
+static inline void vu_set_element(struct vu_virtq_element *elem,
+				  struct iovec *out_sg, struct iovec *in_sg)
+{
+	elem->out_num = !!out_sg;
+	elem->out_sg = out_sg;
+	elem->in_num = !!in_sg;
+	elem->in_sg = in_sg;
+}
+
+void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov,
+		  int elem_cnt);
+int vu_collect(struct vu_dev *vdev, struct vu_virtq *vq,
+	       struct vu_virtq_element *elem, int max_elem, size_t size,
+	       size_t *frame_size);
+void vu_set_vnethdr(const struct vu_dev *vdev,
+		    struct virtio_net_hdr_mrg_rxbuf *vnethdr,
+                    int num_buffers);
+void vu_flush(const struct vu_dev *vdev, struct vu_virtq *vq,
+	      struct vu_virtq_element *elem, int elem_cnt);
+void vu_kick_cb(struct vu_dev *vdev, union epoll_ref ref,
+		const struct timespec *now);
+int vu_send_single(const struct ctx *c, const void *buf, size_t size);
+#endif /* VU_COMMON_H */
-- 
2.47.0

From: David Gibson <david(a)gibson.dropbear.id.au>

tcp_vu_send_flag() and tcp_vu_prepare() both needs to do some different
things for IPv4 vs. IPv6.  However the two paths have a number of lines of
duplicated code.  We can share those at the expense of an additional
conditional (which we might be able to simplify again later).

Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
---
 tcp_vu.c | 91 ++++++++++++++++++++++++--------------------------------
 1 file changed, 39 insertions(+), 52 deletions(-)

diff --git a/tcp_vu.c b/tcp_vu.c
index cc6d4f0f262e..260dda7887e1 100644
--- a/tcp_vu.c
+++ b/tcp_vu.c
@@ -32,6 +32,7 @@
 #include "tcp_internal.h"
 #include "checksum.h"
 #include "vu_common.h"
+#include <time.h>
 
 static struct iovec iov_vu[VIRTQUEUE_MAX_SIZE + 1];
 static struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE];
@@ -96,8 +97,12 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn,
int flags)
 	const struct flowside *tapside = TAPFLOW(conn);
 	size_t l2len, l4len, optlen, hdrlen;
 	struct vu_virtq_element flags_elem[2];
+	struct tcp_flags_t *tcp_flags;
+	struct ipv6hdr *ip6h = NULL;
 	struct iovec flags_iov[2];
+	struct iphdr *iph = NULL;
 	struct ethhdr *eh;
+	uint32_t seq;
 	int elem_cnt;
 	int nb_ack;
 	int ret;
@@ -119,60 +124,44 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn,
int flags)
 	memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
 
 	if (CONN_V4(conn)) {
-		struct tcp_flags_t *tcp_flags;
-		struct iphdr *iph;
-		uint32_t seq;
-
 		eh->h_proto = htons(ETH_P_IP);
 
 		iph = vu_ip(flags_elem[0].in_sg[0].iov_base);
 		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP);
 
 		tcp_flags = vu_payloadv4(flags_elem[0].in_sg[0].iov_base);
-		memset(&tcp_flags->th, 0, sizeof(tcp_flags->th));
-		tcp_flags->th.doff = offsetof(struct tcp_flags_t, opts) / 4;
-		tcp_flags->th.ack = 1;
-
-		seq = conn->seq_to_tap;
-		ret = tcp_prepare_flags(c, conn, flags, &tcp_flags->th,
-					&tcp_flags->opts, &optlen);
-		if (ret <= 0) {
-			vu_queue_rewind(vq, 1);
-			return ret;
-		}
-
-		l4len = tcp_fill_headers4(conn, NULL, iph,
-					  (struct tcp_payload_t *)tcp_flags,
-					  optlen, NULL, seq, true);
-		l2len = sizeof(*iph);
 	} else {
-		struct tcp_flags_t *tcp_flags;
-		struct ipv6hdr *ip6h;
-		uint32_t seq;
-
 		eh->h_proto = htons(ETH_P_IPV6);
 
 		ip6h = vu_ip(flags_elem[0].in_sg[0].iov_base);
 		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP);
-
 		tcp_flags = vu_payloadv6(flags_elem[0].in_sg[0].iov_base);
-		memset(&tcp_flags->th, 0, sizeof(tcp_flags->th));
-		tcp_flags->th.doff = offsetof(struct tcp_flags_t, opts) / 4;
-		tcp_flags->th.ack = 1;
-
-		seq = conn->seq_to_tap;
-		ret = tcp_prepare_flags(c, conn, flags, &tcp_flags->th,
-					&tcp_flags->opts, &optlen);
-		if (ret <= 0) {
-			vu_queue_rewind(vq, 1);
-			return ret;
-		}
+	}
+
+	memset(&tcp_flags->th, 0, sizeof(tcp_flags->th));
+	tcp_flags->th.doff = offsetof(struct tcp_flags_t, opts) / 4;
+	tcp_flags->th.ack = 1;
+
+	seq = conn->seq_to_tap;
+	ret = tcp_prepare_flags(c, conn, flags, &tcp_flags->th,
+				&tcp_flags->opts, &optlen);
+	if (ret <= 0) {
+		vu_queue_rewind(vq, 1);
+		return ret;
+	}
 
+	if (CONN_V4(conn)) {
+		l4len = tcp_fill_headers4(conn, NULL, iph,
+					  (struct tcp_payload_t *)tcp_flags, optlen,
+					  NULL, seq, true);
+		l2len = sizeof(*iph);
+	} else {
 		l4len = tcp_fill_headers6(conn, NULL, ip6h,
 					  (struct tcp_payload_t *)tcp_flags,
 					  optlen, seq, true);
 		l2len = sizeof(*ip6h);
 	}
+
 	l2len += l4len + sizeof(struct ethhdr);
 
 	flags_elem[0].in_sg[0].iov_len = l2len +
@@ -296,7 +285,10 @@ static void tcp_vu_prepare(const struct ctx *c,
 			   size_t dlen, const uint16_t **check)
 {
 	const struct flowside *toside = TAPFLOW(conn);
+	struct tcp_payload_t *payload;
 	char *base = first->iov_base;
+	struct ipv6hdr *ip6h = NULL;
+	struct iphdr *iph = NULL;
 	struct ethhdr *eh;
 
 	/* we guess the first iovec provided by the guest can embed
@@ -309,10 +301,8 @@ static void tcp_vu_prepare(const struct ctx *c,
 	memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
 
 	/* initialize header */
-	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
-		struct tcp_payload_t *payload;
-		struct iphdr *iph;
 
+	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
 		ASSERT(first[0].iov_len >= sizeof(struct virtio_net_hdr_mrg_rxbuf) +
 		       sizeof(struct ethhdr) + sizeof(struct iphdr) +
 		       sizeof(struct tcphdr));
@@ -322,17 +312,7 @@ static void tcp_vu_prepare(const struct ctx *c,
 		iph = vu_ip(base);
 		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP);
 		payload = vu_payloadv4(base);
-		memset(&payload->th, 0, sizeof(payload->th));
-		payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
-		payload->th.ack = 1;
-
-		tcp_fill_headers4(conn, NULL, iph, payload, dlen,
-				  *check, conn->seq_to_tap, true);
-		*check = &iph->check;
 	} else {
-		struct tcp_payload_t *payload;
-		struct ipv6hdr *ip6h;
-
 		ASSERT(first[0].iov_len >= sizeof(struct virtio_net_hdr_mrg_rxbuf) +
 		       sizeof(struct ethhdr) + sizeof(struct ipv6hdr) +
 		       sizeof(struct tcphdr));
@@ -343,10 +323,17 @@ static void tcp_vu_prepare(const struct ctx *c,
 		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP);
 
 		payload = vu_payloadv6(base);
-		memset(&payload->th, 0, sizeof(payload->th));
-		payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
-		payload->th.ack = 1;
+	}
 
+	memset(&payload->th, 0, sizeof(payload->th));
+	payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
+	payload->th.ack = 1;
+
+	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
+		tcp_fill_headers4(conn, NULL, iph, payload, dlen,
+				  *check, conn->seq_to_tap, true);
+		*check = &iph->check;
+	} else {
 		tcp_fill_headers6(conn, NULL, ip6h, payload, dlen,
 				  conn->seq_to_tap, true);
 	}
-- 
2.47.0

From: David Gibson <david(a)gibson.dropbear.id.au>

Currently tcp_fill_headers[46] return the size of the IP payload,
which we use to adjust the size of the last IOV entry for the frame,
so that it only includes the expected data.  This was originally done
to isolate knowledge of the header layout to the header building
functions.  However, we've since reorganised things so that the
callers have knowledge of the layout anyway.

Use that knowledge to adjust iov_len *before* we call tcp_fill_headers*().
This means that the header building functions are called with the IOV
containing the frame and only the frame, which will be useful later on.

For the vhost-user flags, this also simplifies things a bit, since
we'd actually already separately calculated the header length.  For
the vhost-user data case, we'd already shortened the final IOV from
tcp_vu_data_from_sock().

Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
---
 tcp.c          | 24 ++++++++----------------
 tcp_buf.c      | 36 +++++++++++++++++-------------------
 tcp_internal.h | 17 +++++++++--------
 tcp_vu.c       | 22 +++++++++-------------
 4 files changed, 43 insertions(+), 56 deletions(-)

diff --git a/tcp.c b/tcp.c
index 63870aa5e454..85d783d403a2 100644
--- a/tcp.c
+++ b/tcp.c
@@ -977,13 +977,11 @@ static void tcp_fill_header(struct tcphdr *th,
  * @check:		Checksum, if already known
  * @seq:		Sequence number for this segment
  * @no_tcp_csum:	Do not set TCP checksum
- *
- * Return: The IPv4 payload length, host order
  */
-size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
-			 struct tap_hdr *taph, struct iphdr *iph,
-			 struct tcp_payload_t *bp, size_t dlen,
-			 const uint16_t *check, uint32_t seq, bool no_tcp_csum)
+void tcp_fill_headers4(const struct tcp_tap_conn *conn,
+		       struct tap_hdr *taph, struct iphdr *iph,
+		       struct tcp_payload_t *bp, size_t dlen,
+		       const uint16_t *check, uint32_t seq, bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
 	const struct in_addr *src4 = inany_v4(&tapside->oaddr);
@@ -1014,8 +1012,6 @@ size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
 	}
 
 	tap_hdr_update(taph, l3len + sizeof(struct ethhdr));
-
-	return l4len;
 }
 
 /**
@@ -1028,13 +1024,11 @@ size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
  * @check:		Checksum, if already known
  * @seq:		Sequence number for this segment
  * @no_tcp_csum:	Do not set TCP checksum
- *
- * Return: The IPv6 payload length, host order
  */
-size_t tcp_fill_headers6(const struct tcp_tap_conn *conn,
-			 struct tap_hdr *taph, struct ipv6hdr *ip6h,
-			 struct tcp_payload_t *bp, size_t dlen,
-			 uint32_t seq, bool no_tcp_csum)
+void tcp_fill_headers6(const struct tcp_tap_conn *conn,
+		       struct tap_hdr *taph, struct ipv6hdr *ip6h,
+		       struct tcp_payload_t *bp, size_t dlen,
+		       uint32_t seq, bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
 	size_t l4len = dlen + sizeof(bp->th);
@@ -1065,8 +1059,6 @@ size_t tcp_fill_headers6(const struct tcp_tap_conn *conn,
 	}
 
 	tap_hdr_update(taph, l4len + sizeof(*ip6h) + sizeof(struct ethhdr));
-
-	return l4len;
 }
 
 /**
diff --git a/tcp_buf.c b/tcp_buf.c
index 6f8f5bb5cc21..52a19eda850c 100644
--- a/tcp_buf.c
+++ b/tcp_buf.c
@@ -194,28 +194,26 @@ void tcp_payload_flush(const struct ctx *c)
  * @check:	Checksum, if already known
  * @seq:	Sequence number for this segment
  * @no_tcp_csum: Do not set TCP checksum
- *
- * Return: IP payload length, host order
  */
-static size_t tcp_l2_buf_fill_headers(const struct tcp_tap_conn *conn,
-				      struct iovec *iov, size_t dlen,
-				      const uint16_t *check, uint32_t seq,
-				      bool no_tcp_csum)
+static void tcp_l2_buf_fill_headers(const struct tcp_tap_conn *conn,
+				    struct iovec *iov, size_t dlen,
+				    const uint16_t *check, uint32_t seq,
+				    bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
 	const struct in_addr *a4 = inany_v4(&tapside->oaddr);
 
 	if (a4) {
-		return tcp_fill_headers4(conn, iov[TCP_IOV_TAP].iov_base,
-					 iov[TCP_IOV_IP].iov_base,
-					 iov[TCP_IOV_PAYLOAD].iov_base, dlen,
-					 check, seq, no_tcp_csum);
+		tcp_fill_headers4(conn, iov[TCP_IOV_TAP].iov_base,
+				  iov[TCP_IOV_IP].iov_base,
+				  iov[TCP_IOV_PAYLOAD].iov_base, dlen,
+				  check, seq, no_tcp_csum);
+	} else {
+		tcp_fill_headers6(conn, iov[TCP_IOV_TAP].iov_base,
+				  iov[TCP_IOV_IP].iov_base,
+				  iov[TCP_IOV_PAYLOAD].iov_base, dlen,
+				  seq, no_tcp_csum);
 	}
-
-	return tcp_fill_headers6(conn, iov[TCP_IOV_TAP].iov_base,
-				 iov[TCP_IOV_IP].iov_base,
-				 iov[TCP_IOV_PAYLOAD].iov_base, dlen,
-				 seq, no_tcp_csum);
 }
 
 /**
@@ -252,8 +250,9 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn,
int flags)
 		return ret;
 
 	tcp_flags_used++;
-	l4len = tcp_l2_buf_fill_headers(conn, iov, optlen, NULL, seq, false);
+	l4len = optlen + sizeof(struct tcphdr);
 	iov[TCP_IOV_PAYLOAD].iov_len = l4len;
+	tcp_l2_buf_fill_headers(conn, iov, optlen, NULL, seq, false);
 
 	if (flags & DUP_ACK) {
 		struct iovec *dup_iov;
@@ -287,7 +286,6 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn
*conn,
 {
 	const uint16_t *check = NULL;
 	struct iovec *iov;
-	size_t l4len;
 
 	conn->seq_to_tap = seq + dlen;
 	tcp_frame_conns[tcp_payload_used] = conn;
@@ -305,8 +303,8 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn
*conn,
 		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_payload_ip[tcp_payload_used]);
 		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
 	}
-	l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq, false);
-	iov[TCP_IOV_PAYLOAD].iov_len = l4len;
+	iov[TCP_IOV_PAYLOAD].iov_len = dlen + sizeof(struct tcphdr);
+	tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq, false);
 	if (++tcp_payload_used > TCP_FRAMES_MEM - 1)
 		tcp_payload_flush(c);
 }
diff --git a/tcp_internal.h b/tcp_internal.h
index 21e31a03a83d..2989db7fb224 100644
--- a/tcp_internal.h
+++ b/tcp_internal.h
@@ -183,14 +183,15 @@ void tcp_update_check_tcp4(const struct iphdr *iph,
 void tcp_update_check_tcp6(const struct ipv6hdr *ip6h,
 			   const struct iovec *iov, int iov_cnt,
 			   size_t l4offset);
-size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
-			 struct tap_hdr *taph, struct iphdr *iph,
-			 struct tcp_payload_t *bp, size_t dlen,
-			 const uint16_t *check, uint32_t seq, bool no_tcp_csum);
-size_t tcp_fill_headers6(const struct tcp_tap_conn *conn,
-			 struct tap_hdr *taph, struct ipv6hdr *ip6h,
-			 struct tcp_payload_t *bp, size_t dlen,
-			 uint32_t seq, bool no_tcp_csum);
+void tcp_fill_headers4(const struct tcp_tap_conn *conn,
+		       struct tap_hdr *taph, struct iphdr *iph,
+		       struct tcp_payload_t *bp, size_t dlen,
+		       const uint16_t *check, uint32_t seq, bool no_tcp_csum);
+void tcp_fill_headers6(const struct tcp_tap_conn *conn,
+		       struct tap_hdr *taph, struct ipv6hdr *ip6h,
+		       struct tcp_payload_t *bp, size_t dlen,
+		       uint32_t seq, bool no_tcp_csum);
+
 int tcp_update_seqack_wnd(const struct ctx *c, struct tcp_tap_conn *conn,
 			  bool force_seq, struct tcp_info_linux *tinfo);
 int tcp_prepare_flags(const struct ctx *c, struct tcp_tap_conn *conn,
diff --git a/tcp_vu.c b/tcp_vu.c
index 260dda7887e1..4df7186d0006 100644
--- a/tcp_vu.c
+++ b/tcp_vu.c
@@ -95,7 +95,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int
flags)
 	struct vu_dev *vdev = c->vdev;
 	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
 	const struct flowside *tapside = TAPFLOW(conn);
-	size_t l2len, l4len, optlen, hdrlen;
+	size_t optlen, hdrlen;
 	struct vu_virtq_element flags_elem[2];
 	struct tcp_flags_t *tcp_flags;
 	struct ipv6hdr *ip6h = NULL;
@@ -150,22 +150,18 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn,
int flags)
 		return ret;
 	}
 
+	flags_elem[0].in_sg[0].iov_len = hdrlen + optlen;
+
 	if (CONN_V4(conn)) {
-		l4len = tcp_fill_headers4(conn, NULL, iph,
-					  (struct tcp_payload_t *)tcp_flags, optlen,
-					  NULL, seq, true);
-		l2len = sizeof(*iph);
+		tcp_fill_headers4(conn, NULL, iph,
+				  (struct tcp_payload_t *)tcp_flags, optlen,
+				  NULL, seq, true);
 	} else {
-		l4len = tcp_fill_headers6(conn, NULL, ip6h,
-					  (struct tcp_payload_t *)tcp_flags,
-					  optlen, seq, true);
-		l2len = sizeof(*ip6h);
+		tcp_fill_headers6(conn, NULL, ip6h,
+				  (struct tcp_payload_t *)tcp_flags,
+				  optlen, seq, true);
 	}
 
-	l2len += l4len + sizeof(struct ethhdr);
-
-	flags_elem[0].in_sg[0].iov_len = l2len +
-				   sizeof(struct virtio_net_hdr_mrg_rxbuf);
 	if (*c->pcap) {
 		tcp_vu_update_check(tapside, &flags_elem[0].in_sg[0], 1);
 		pcap_iov(&flags_elem[0].in_sg[0], 1,
-- 
2.47.0