On Mon, Mar 23, 2026 at 03:31:49PM +0100, Laurent Vivier wrote:
udp_vu_sock_recv() currently mixes two concerns: receiving data from the socket and managing virtqueue buffers (collecting, rewinding, releasing). This makes the function harder to reason about and couples socket I/O with virtqueue state.
Move all virtqueue operations, vu_collect(), vu_init_elem(), vu_queue_rewind(), vu_set_vnethdr(), and the queue-readiness check, into udp_vu_sock_to_tap(), which is the only caller. This turns udp_vu_sock_recv() into a pure socket receive function that simply reads into the provided iov array and adjusts its length.
Signed-off-by: Laurent Vivier
Reviewed-by: David Gibson
--- udp_vu.c | 110 +++++++++++++++++++++++++------------------------------ 1 file changed, 49 insertions(+), 61 deletions(-)
diff --git a/udp_vu.c b/udp_vu.c index 6638cb0ddc5f..dc949e30a793 100644 --- a/udp_vu.c +++ b/udp_vu.c @@ -33,9 +33,6 @@ #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() - Sum size of all headers, from UDP to virtio-net * @v6: Set for IPv6 packet @@ -58,78 +55,35 @@ static size_t udp_vu_hdrlen(bool v6)
/** * udp_vu_sock_recv() - Receive datagrams from socket into vhost-user buffers - * @c: Execution context * @iov: IO vector for the frame (in/out) * @cnt: Number of IO vector entries (in/out) - * @vq: virtqueue to use to receive data * @s: Socket to receive from * @v6: Set for IPv6 connections * - * Return: size of received data, 0 if the datagram - * was discarded because the virtqueue is not ready, -1 on error + * Return: size of received data, -1 on error */ -static ssize_t udp_vu_sock_recv(const struct ctx *c, struct iovec *iov, - size_t *cnt, unsigned *elem_used, - struct vu_virtq *vq, int s, bool v6) +static ssize_t udp_vu_sock_recv(struct iovec *iov, size_t *cnt, int s, bool v6) { - const struct vu_dev *vdev = c->vdev; - struct msghdr msg = { 0 }; + struct iovec msg_iov[*cnt]; + struct msghdr msg = { 0 }; struct iov_tail payload; - size_t hdrlen, iov_used; - unsigned elem_cnt; - unsigned i, j; + size_t hdrlen; ssize_t dlen;
- assert(!c->no_udp); - - if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) { - debug("Got UDP packet, but RX virtqueue not usable yet"); - - if (recvmsg(s, &msg, MSG_DONTWAIT) < 0) - debug_perror("Failed to discard datagram"); - - *cnt = 0; - return 0; - } - /* compute L2 header length */ hdrlen = udp_vu_hdrlen(v6);
- elem_cnt = vu_collect(vdev, vq, elem, ARRAY_SIZE(elem), - iov, *cnt, &iov_used, - IP_MAX_MTU + ETH_HLEN + VNET_HLEN, NULL); - if (elem_cnt == 0) - return -1; - - assert((size_t)elem_cnt == iov_used); /* one iovec per element */ - - payload = IOV_TAIL(iov, iov_used, hdrlen); + payload = IOV_TAIL(iov, *cnt, hdrlen);
- struct iovec msg_iov[payload.cnt]; msg.msg_iov = msg_iov; msg.msg_iovlen = iov_tail_clone(msg.msg_iov, payload.cnt, &payload);
/* read data from the socket */ dlen = recvmsg(s, &msg, 0); - if (dlen < 0) { - vu_queue_rewind(vq, elem_cnt); + if (dlen < 0) return -1; - } - - *cnt = vu_pad(iov, iov_used, 0, dlen + hdrlen); - - *elem_used = 0; - for (i = 0, j = 0; j < *cnt && i < elem_cnt; i++) { - if (j + elem[i].in_num > *cnt) - elem[i].in_num = *cnt - j; - j += elem[i].in_num; - (*elem_used)++; - }
- vu_set_vnethdr(iov[0].iov_base, *elem_used); - - /* release unused buffers */ - vu_queue_rewind(vq, elem_cnt - *elem_used); + *cnt = vu_pad(iov, *cnt, 0, dlen + hdrlen);
return dlen; } @@ -217,26 +171,60 @@ static void udp_vu_csum(const struct flowside *toside, */ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx) { + static struct iovec iov_vu [VIRTQUEUE_MAX_SIZE]; + static struct vu_virtq_element elem [VIRTQUEUE_MAX_SIZE]; const struct flowside *toside = flowside_at_sidx(tosidx); bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)); struct vu_dev *vdev = c->vdev; struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; - struct iov_tail data; int i;
+ assert(!c->no_udp); + + if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) { + struct msghdr msg = { 0 }; + + debug("Got UDP packet, but RX virtqueue not usable yet"); + + for (i = 0; i < n; i++) { + if (recvmsg(s, &msg, MSG_DONTWAIT) < 0) + debug_perror("Failed to discard datagram"); + } + + return; + } + for (i = 0; i < n; i++) { - unsigned elem_used; + unsigned elem_used, elem_cnt, j, k; size_t iov_cnt; ssize_t dlen;
- iov_cnt = ARRAY_SIZE(iov_vu); - dlen = udp_vu_sock_recv(c, iov_vu, &iov_cnt, &elem_used, vq, - s, v6); - if (dlen < 0) + elem_cnt = vu_collect(vdev, vq, elem, ARRAY_SIZE(elem), + iov_vu, ARRAY_SIZE(iov_vu), &iov_cnt, + IP_MAX_MTU + ETH_HLEN + VNET_HLEN, NULL); + if (elem_cnt == 0) + break; + + dlen = udp_vu_sock_recv(iov_vu, &iov_cnt, s, v6); + if (dlen < 0) { + vu_queue_rewind(vq, elem_cnt); break; + } + + elem_used = 0; + for (j = 0, k = 0; k < iov_cnt && j < elem_cnt; j++) { + if (k + elem[j].in_num > iov_cnt) + elem[j].in_num = iov_cnt - k; + k += elem[j].in_num; + elem_used++; + } + + /* release unused buffers */ + vu_queue_rewind(vq, elem_cnt - elem_used);
if (iov_cnt > 0) { - data = IOV_TAIL(iov_vu, iov_cnt, 0); + struct iov_tail data = IOV_TAIL(iov_vu, iov_cnt, 0); + vu_set_vnethdr(iov_vu[0].iov_base, elem_used); udp_vu_prepare(c, &data, toside, dlen); if (*c->pcap) { udp_vu_csum(toside, &data); -- 2.53.0
-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson