- dev - passt

[PATCH 0/5] Fixes for Fedora 43 (or other bitrot)
by David Gibson 06 Jan '26

06 Jan '26

While away, I updated my laptop to Fedora 43. Naturally a bunch of things in the passt tests broke. First there were the usual breakages due to a new static checker version (also one real bug). Then several other problems. David Gibson (5): util: Be more defensive about buffer overruns in read_file() migrate: Don't use terminator element for versions[] array treewide: Don't rely on terminator records in ip[46].dns arrays test: Handle Operating System Command escapes in terminal output test: Include sshd-auth in mbuto guest image conf.c | 8 ++++++-- dhcp.c | 4 +++- dhcpv6.c | 4 +++- migrate.c | 3 +-- ndp.c | 4 +++- passt.h | 4 ++-- test/lib/term | 4 ++-- test/passt.mbuto | 6 ++++++ util.c | 2 +- 9 files changed, 27 insertions(+), 12 deletions(-) -- 2.52.0

2 11

[PATCH] udp_vu: Discard datagrams when RX virtqueue is not usable
by Laurent Vivier 06 Jan '26

06 Jan '26

During vhost-user device initialization, UDP datagrams may arrive on listening sockets before the guest has enabled the RX virtqueue. When this happens, udp_vu_sock_recv() returns 0 without consuming the datagram from the socket. The caller, udp_sock_fwd(), uses a while loop with udp_peek_addr() to process pending datagrams. Since the datagram remains in the socket buffer, udp_peek_addr() keeps returning data available, causing a busy loop with 100% CPU usage. Add an early check for virtqueue readiness in udp_vu_sock_to_tap(), mirroring tcp_vu_data_from_sock(). When the queue is not enabled or not started, explicitly discard the datagram with recvmsg() and return. The caller will drain remaining datagrams through repeated calls. Fixes: 28997fcb29b5 ("vhost-user: add vhost-user") Link: https://bugs.passt.top/show_bug.cgi?id=185 Signed-off-by: Laurent Vivier <lvivier(a)redhat.com> --- udp_vu.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/udp_vu.c b/udp_vu.c index c30dcf97698f..67f4ee619bfb 100644 --- a/udp_vu.c +++ b/udp_vu.c @@ -211,6 +211,17 @@ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx) struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; int i; + if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) { + struct msghdr msg = { 0 }; + + debug("Got UDP packet, but RX virtqueue not usable yet"); + + if (recvmsg(s, &msg, MSG_DONTWAIT) < 0) + debug_perror("Failed to discard datagram"); + + return; + } + for (i = 0; i < n; i++) { ssize_t dlen; int iov_used; -- 2.52.0

2 2

[PATCH 2/2] fwd: Minor cleanup to fwd_nat_from_splice()
by David Gibson 06 Jan '26

06 Jan '26

The order we do things in this function is slightly odd, and we have a redundant assignment to tgt->oport. Remove that, and re-order for clarity. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- fwd.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/fwd.c b/fwd.c index 9b701ad0..961c533f 100644 --- a/fwd.c +++ b/fwd.c @@ -660,13 +660,15 @@ uint8_t fwd_nat_from_splice(const struct ctx *c, uint8_t proto, return PIF_NONE; } + /* Preserve the src & dest (loopback) addresses */ + tgt->oaddr = ini->eaddr; tgt->eaddr = ini->oaddr; - /* Preserve the specific loopback address used, but let the kernel pick - * a source port on the target side - */ - tgt->oaddr = ini->eaddr; + /* Let the kernel pick a host side source port */ tgt->oport = 0; + if (proto == IPPROTO_UDP) + /* But for UDP preserve the source port */ + tgt->oport = ini->eport; tgt->eport = ini->oport; if (proto == IPPROTO_TCP) @@ -674,12 +676,6 @@ uint8_t fwd_nat_from_splice(const struct ctx *c, uint8_t proto, else if (proto == IPPROTO_UDP) tgt->eport += c->udp.fwd_out.delta[tgt->eport]; - /* Let the kernel pick a host side source port */ - tgt->oport = 0; - if (proto == IPPROTO_UDP) - /* But for UDP preserve the source port */ - tgt->oport = ini->eport; - return PIF_HOST; } -- 2.52.0

1 0

[PATCH 0/2] Small cleanups to splice forwarding logic
by David Gibson 06 Jan '26

06 Jan '26

While working on more flexible forwarding stuff, noticed a couple of warts here. David Gibson (2): fwd: Remove now-unnecessary handling of unspecified oaddr from splice fwd: Minor cleanup to fwd_nat_from_splice() fwd.c | 25 ++++++++----------------- 1 file changed, 8 insertions(+), 17 deletions(-) -- 2.52.0

1 1

[PATCH] conf, pasta: Add --no-tap option
by Yumei Huang 05 Jan '26

05 Jan '26

This patch introduces a mode where we only forward loopback connections and traffic between two namespaces (via the loopback interface, 'lo'), without a tap device. With this, podman can support forwarding ::1 in custom networks when using rootlesskit for forwarding ports. In --no-tap mode, --host-lo-to-ns-lo, --no-icmp and --no-ra is automatically enabled. Options requiring a tap device (--ns-ifname, --ns-mac-addr, --config-net, --outbound-if4/6) are rejected. Link: https://bugs.passt.top/show_bug.cgi?id=149 Signed-off-by: Yumei Huang <yuhuang(a)redhat.com> --- conf.c | 56 +++++++++++++++++++++++++++++++++++++++++--------------- fwd.c | 3 +++ passt.1 | 5 +++++ passt.h | 2 ++ pasta.c | 3 +++ tap.c | 11 +++++++---- 6 files changed, 61 insertions(+), 19 deletions(-) diff --git a/conf.c b/conf.c index 84ae12b..353d0a5 100644 --- a/conf.c +++ b/conf.c @@ -1049,7 +1049,8 @@ pasta_opts: " --no-copy-addrs DEPRECATED:\n" " Don't copy all addresses to namespace\n" " --ns-mac-addr ADDR Set MAC address on tap interface\n" - " --no-splice Disable inbound socket splicing\n"); + " --no-splice Disable inbound socket splicing\n" + " --no-tap Don't create tap device\n"); passt_exit(status); } @@ -1451,6 +1452,7 @@ void conf(struct ctx *c, int argc, char **argv) {"no-ndp", no_argument, &c->no_ndp, 1 }, {"no-ra", no_argument, &c->no_ra, 1 }, {"no-splice", no_argument, &c->no_splice, 1 }, + {"no-tap", no_argument, &c->no_tap, 1 }, {"freebind", no_argument, &c->freebind, 1 }, {"no-map-gw", no_argument, &no_map_gw, 1 }, {"ipv4-only", no_argument, NULL, '4' }, @@ -1947,8 +1949,11 @@ void conf(struct ctx *c, int argc, char **argv) } } while (name != -1); - if (c->mode != MODE_PASTA) + if (c->mode != MODE_PASTA) { c->no_splice = 1; + if (c->no_tap) + die("--no-tap is for pasta mode only"); + } if (c->mode == MODE_PASTA && !c->pasta_conf_ns) { if (copy_routes_opt) @@ -1957,6 +1962,25 @@ void conf(struct ctx *c, int argc, char **argv) die("--no-copy-addrs needs --config-net"); } + if (c->mode == MODE_PASTA && c->no_tap) { + if (c->no_splice) + die("--no-tap is incompatible with --no-splice"); + if (*c->ip4.ifname_out || *c->ip6.ifname_out) + die("--no-tap is incompatible with --outbound-if4/6"); + if (*c->pasta_ifn) + die("--no-tap is incompatible with --ns-ifname"); + if (*c->guest_mac) + die("--no-tap is incompatible with --ns-mac-addr"); + if (c->pasta_conf_ns) + die("--no-tap is incompatible with --config-net"); + + c->host_lo_to_ns_lo = 1; + c->no_icmp = 1; + c->no_ra = 1; + c->no_dns = 1; + c->no_dns_search = 1; + } + if (!ifi4 && *c->ip4.ifname_out) ifi4 = if_nametoindex(c->ip4.ifname_out); @@ -1980,9 +2004,9 @@ void conf(struct ctx *c, int argc, char **argv) log_conf_parsed = true; /* Stop printing everything */ nl_sock_init(c, false); - if (!v6_only) + if (!v6_only && !c->no_tap) c->ifi4 = conf_ip4(ifi4, &c->ip4); - if (!v4_only) + if (!v4_only && !c->no_tap) c->ifi6 = conf_ip6(ifi6, &c->ip6); if (c->ifi4 && c->mtu < IPV4_MIN_MTU) { @@ -1998,30 +2022,32 @@ void conf(struct ctx *c, int argc, char **argv) (*c->ip6.ifname_out && !c->ifi6)) die("External interface not usable"); - if (!c->ifi4 && !c->ifi6 && !*c->pasta_ifn) { + if (!c->ifi4 && !c->ifi6 && !*c->pasta_ifn && !c->no_tap) { strncpy(c->pasta_ifn, pasta_default_ifn, sizeof(c->pasta_ifn) - 1); } if (!c->ifi4 && !v6_only) { - info("IPv4: no external interface as template, use local mode"); - - conf_ip4_local(&c->ip4); + if (!c->no_tap) { + info("IPv4: no external interface as template, use local mode"); + conf_ip4_local(&c->ip4); + } c->ifi4 = -1; } if (!c->ifi6 && !v4_only) { - info("IPv6: no external interface as template, use local mode"); - - conf_ip6_local(&c->ip6); + if (!c->no_tap) { + info("IPv6: no external interface as template, use local mode"); + conf_ip6_local(&c->ip6); + } c->ifi6 = -1; } - if (c->ifi4 && !no_map_gw && + if (c->ifi4 > 0 && !no_map_gw && IN4_IS_ADDR_UNSPECIFIED(&c->ip4.map_host_loopback)) c->ip4.map_host_loopback = c->ip4.guest_gw; - if (c->ifi6 && !no_map_gw && + if (c->ifi6 > 0 && !no_map_gw && IN6_IS_ADDR_UNSPECIFIED(&c->ip6.map_host_loopback)) c->ip6.map_host_loopback = c->ip6.guest_gw; @@ -2116,10 +2142,10 @@ void conf(struct ctx *c, int argc, char **argv) conf_ports(c, name, optarg, &c->udp.fwd_out); } while (name != -1); - if (!c->ifi4) + if (c->ifi4 <= 0) c->no_dhcp = 1; - if (!c->ifi6) { + if (c->ifi6 <= 0) { c->no_ndp = 1; c->no_dhcpv6 = 1; } else if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) { diff --git a/fwd.c b/fwd.c index 44a0e10..2f4a89a 100644 --- a/fwd.c +++ b/fwd.c @@ -780,6 +780,9 @@ uint8_t fwd_nat_from_host(const struct ctx *c, uint8_t proto, return PIF_SPLICE; } + if (c->no_tap) + return PIF_NONE; + if (!nat_inbound(c, &ini->eaddr, &tgt->oaddr)) { if (inany_v4(&ini->eaddr)) { if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.our_tap_addr)) diff --git a/passt.1 b/passt.1 index db0d662..2d643f7 100644 --- a/passt.1 +++ b/passt.1 @@ -755,6 +755,11 @@ Default is to let the tap driver build a pseudorandom hardware address. Disable the bypass path for inbound, local traffic. See the section \fBHandling of local traffic in pasta\fR in the \fBNOTES\fR for more details. +.TP +.BR \-\-no-tap +Do not create a tap device in the namespace. In this mode, only local loopback +traffic between namespaces is forwarded using splice. + .SH EXAMPLES .SS \fBpasta diff --git a/passt.h b/passt.h index 79d01dd..0c1ec4c 100644 --- a/passt.h +++ b/passt.h @@ -200,6 +200,7 @@ struct ip6_ctx { * @no_ndp: Disable NDP handler altogether * @no_ra: Disable router advertisements * @no_splice: Disable socket splicing for inbound traffic + * @no_tap: Do not create tap device * @host_lo_to_ns_lo: Map host loopback addresses to ns loopback addresses * @freebind: Allow binding of non-local addresses for forwarding * @low_wmem: Low probed net.core.wmem_max @@ -277,6 +278,7 @@ struct ctx { int no_ndp; int no_ra; int no_splice; + int no_tap; int host_lo_to_ns_lo; int freebind; diff --git a/pasta.c b/pasta.c index 0ddd6b0..3510ec5 100644 --- a/pasta.c +++ b/pasta.c @@ -316,6 +316,9 @@ void pasta_ns_conf(struct ctx *c) die("Couldn't bring up loopback interface in namespace: %s", strerror_(-rc)); + if (c->no_tap) + return; + /* Get or set MAC in target namespace */ if (MAC_IS_ZERO(c->guest_mac)) nl_link_get_mac(nl_sock_ns, c->pasta_ifi, c->guest_mac); diff --git a/tap.c b/tap.c index 9d1344b..9b4eedc 100644 --- a/tap.c +++ b/tap.c @@ -1491,13 +1491,16 @@ static int tap_ns_tun(void *arg) */ static void tap_sock_tun_init(struct ctx *c) { - NS_CALL(tap_ns_tun, c); - if (c->fd_tap == -1) - die("Failed to set up tap device in namespace"); + if (!c->no_tap) { + NS_CALL(tap_ns_tun, c); + if (c->fd_tap == -1) + die("Failed to set up tap device in namespace"); + } pasta_ns_conf(c); - tap_start_connection(c); + if (!c->no_tap) + tap_start_connection(c); } /** -- 2.49.0

4 5

[PATCH 3/3] fwd, tcp, udp: Consolidate epoll refs for listening sockets
by David Gibson 05 Jan '26

05 Jan '26

The epoll references we use for TCP listening sockets and UDP "listening" sockets have identical information. Combine them into a single structure. Note that, despite the name, epoll_ref.udp was only ever used for "listening" sockets, not flow sockets. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- epoll_ctl.h | 6 ++---- fwd.h | 14 ++++++++++++++ tcp.c | 8 ++++---- tcp.h | 14 -------------- udp.c | 6 +++--- udp.h | 15 --------------- 6 files changed, 23 insertions(+), 40 deletions(-) diff --git a/epoll_ctl.h b/epoll_ctl.h index 02b081e2..3f802e76 100644 --- a/epoll_ctl.h +++ b/epoll_ctl.h @@ -21,8 +21,7 @@ * @fd: File descriptor number (implies < 2^24 total descriptors) * @flow: Index of the flow this fd is linked to * @flowside: Index and side of a flow this fd is linked to - * @tcp_listen: TCP-specific reference part for listening sockets - * @udp: UDP-specific reference part + * @listen: Information for listening sockets * @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 @@ -35,8 +34,7 @@ union epoll_ref { union { uint32_t flow; flow_sidx_t flowside; - union tcp_listen_epoll_ref tcp_listen; - union udp_listen_epoll_ref udp; + union fwd_listen_ref listen; uint32_t data; int nsdir_fd; int queue; diff --git a/fwd.h b/fwd.h index 77925822..bf41907b 100644 --- a/fwd.h +++ b/fwd.h @@ -16,6 +16,20 @@ struct flowside; void fwd_probe_ephemeral(void); bool fwd_port_is_ephemeral(in_port_t port); +/** + * union fwd_listen_ref - information about a single listening socket + * @port: Bound port number of the socket + * @pif: pif in which the socket is listening + * @fe: Index of forwarding entry + */ +union fwd_listen_ref { + struct { + in_port_t port; + uint8_t pif; + }; + uint32_t u32; +}; + enum fwd_ports_mode { FWD_UNSET = 0, FWD_SPEC = 1, diff --git a/tcp.c b/tcp.c index e7fa85f3..9fc385d2 100644 --- a/tcp.c +++ b/tcp.c @@ -2485,8 +2485,8 @@ void tcp_listen_handler(const struct ctx *c, union epoll_ref ref, * address, record that as our address, as implemented for vhost-user * mode only, below. */ - ini = flow_initiate_sa(flow, ref.tcp_listen.pif, &sa, - NULL, ref.tcp_listen.port); + ini = flow_initiate_sa(flow, ref.listen.pif, &sa, + NULL, ref.listen.port); if (getsockname(s, &sa.sa, &sl) || inany_from_sockaddr(&ini->oaddr, &ini->oport, &sa) < 0) @@ -2685,7 +2685,7 @@ void tcp_sock_handler(const struct ctx *c, union epoll_ref ref, int tcp_listen(const struct ctx *c, uint8_t pif, const union inany_addr *addr, const char *ifname, in_port_t port) { - union tcp_listen_epoll_ref tref = { + union fwd_listen_ref ref = { .port = port, .pif = pif, }; @@ -2722,7 +2722,7 @@ int tcp_listen(const struct ctx *c, uint8_t pif, } s = pif_sock_l4(c, EPOLL_TYPE_TCP_LISTEN, pif, addr, ifname, - port, tref.u32); + port, ref.u32); if (fwd->mode == FWD_AUTO) { if (!addr || inany_v4(addr)) diff --git a/tcp.h b/tcp.h index 516dfef5..ef1e3544 100644 --- a/tcp.h +++ b/tcp.h @@ -30,20 +30,6 @@ void tcp_update_l2_buf(const unsigned char *eth_d); extern bool peek_offset_cap; -/** - * union tcp_listen_epoll_ref - epoll reference portion for TCP listening - * @port: Bound port number of the socket - * @pif: pif in which the socket is listening - * @u32: Opaque u32 value of reference - */ -union tcp_listen_epoll_ref { - struct { - in_port_t port; - uint8_t pif; - }; - uint32_t u32; -}; - /** * struct tcp_ctx - Execution context for TCP routines * @port_to_tap: Ports bound host-side, packets to tap or spliced diff --git a/udp.c b/udp.c index eda55c39..747d4dd4 100644 --- a/udp.c +++ b/udp.c @@ -928,7 +928,7 @@ void udp_listen_sock_handler(const struct ctx *c, const struct timespec *now) { if (events & (EPOLLERR | EPOLLIN)) - udp_sock_fwd(c, ref.fd, ref.udp.pif, ref.udp.port, now); + udp_sock_fwd(c, ref.fd, ref.listen.pif, ref.listen.port, now); } /** @@ -1141,7 +1141,7 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif, int udp_listen(const struct ctx *c, uint8_t pif, const union inany_addr *addr, const char *ifname, in_port_t port) { - union udp_listen_epoll_ref uref = { + union fwd_listen_ref ref = { .pif = pif, .port = port, }; @@ -1175,7 +1175,7 @@ int udp_listen(const struct ctx *c, uint8_t pif, } s = pif_sock_l4(c, EPOLL_TYPE_UDP_LISTEN, pif, - addr, ifname, port, uref.u32); + addr, ifname, port, ref.u32); if (!addr || inany_v4(addr)) socks[V4][port] = s < 0 ? -1 : s; diff --git a/udp.h b/udp.h index 5407db3b..94c698e2 100644 --- a/udp.h +++ b/udp.h @@ -22,21 +22,6 @@ int udp_init(struct ctx *c); void udp_port_rebind_all(struct ctx *c); void udp_update_l2_buf(const unsigned char *eth_d); -/** - * union udp_listen_epoll_ref - epoll reference for "listening" UDP sockets - * @port: Source port for connected sockets, bound port otherwise - * @pif: pif for this socket - * @u32: Opaque u32 value of reference - */ -union udp_listen_epoll_ref { - struct { - in_port_t port; - uint8_t pif; - }; - uint32_t u32; -}; - - /** * struct udp_ctx - Execution context for UDP * @fwd_in: Port forwarding configuration for inbound packets -- 2.52.0

1 0

[PATCH 0/3] Clean ups to epoll references
by David Gibson 05 Jan '26

05 Jan '26

A handful of simple cleanups to epoll references. David Gibson (3): tcp: Remove unused tcp_epoll_ref epoll_ctl: Add missing description for flowside field of epoll_ref fwd, tcp, udp: Consolidate epoll refs for listening sockets epoll_ctl.h | 7 +++---- fwd.h | 14 ++++++++++++++ tcp.c | 8 ++++---- tcp.h | 24 ------------------------ udp.c | 6 +++--- udp.h | 15 --------------- 6 files changed, 24 insertions(+), 50 deletions(-) -- 2.52.0

1 2

[PATCH 3/3] tcp, udp: Make {tcp,udp}_listen() return socket fds
by David Gibson 05 Jan '26

05 Jan '26

{tcp,udp}_listen() currently return 0 on success, rather than the socket fd they created. Historically, that was because these functions could sometimes create multiple sockets. We've now refactored things to avoid that, so it makes more sense for them to return the socket on success. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 14 +++++++------- tcp.c | 7 ++----- udp.c | 4 ++-- 3 files changed, 11 insertions(+), 14 deletions(-) diff --git a/conf.c b/conf.c index cc3c20a9..5db49653 100644 --- a/conf.c +++ b/conf.c @@ -149,7 +149,7 @@ static void conf_ports_range_except(const struct ctx *c, char optname, { bool bound_one = false; unsigned i; - int ret; + int fd; if (first == 0) { die("Can't forward port 0 for option '-%c %s'", @@ -185,23 +185,23 @@ static void conf_ports_range_except(const struct ctx *c, char optname, fwd->delta[i] = to - first; if (optname == 't') - ret = tcp_listen(c, PIF_HOST, addr, ifname, i); + fd = tcp_listen(c, PIF_HOST, addr, ifname, i); else if (optname == 'u') - ret = udp_listen(c, PIF_HOST, addr, ifname, i); + fd = udp_listen(c, PIF_HOST, addr, ifname, i); else /* No way to check in advance for -T and -U */ - ret = 0; + fd = 0; - if (ret == -ENFILE || ret == -EMFILE) { + if (fd == -ENFILE || fd == -EMFILE) { die("Can't open enough sockets for port specifier: %s", optarg); } - if (!ret) { + if (fd >= 0) { bound_one = true; } else if (!weak) { die("Failed to bind port %u (%s) for option '-%c %s'", - i, strerror_(-ret), optname, optarg); + i, strerror_(-fd), optname, optarg); } } diff --git a/tcp.c b/tcp.c index 67007c05..80b47f3c 100644 --- a/tcp.c +++ b/tcp.c @@ -2680,7 +2680,7 @@ void tcp_sock_handler(const struct ctx *c, union epoll_ref ref, * @ifname: Name of interface to bind to, NULL for any * @port: Port, host order * - * Return: 0 on success, negative error code on failure + * Return: Socket fd on success, negative error code on failure */ int tcp_listen(const struct ctx *c, uint8_t pif, const union inany_addr *addr, const char *ifname, in_port_t port) @@ -2729,10 +2729,7 @@ int tcp_listen(const struct ctx *c, uint8_t pif, socks[port][V6] = s < 0 ? -1 : s; } - if (s < 0) - return s; - - return 0; + return s; } /** diff --git a/udp.c b/udp.c index 8cfa1e1f..63dc7c25 100644 --- a/udp.c +++ b/udp.c @@ -1136,7 +1136,7 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif, * @ifname: Name of interface to bind to, NULL if not configured * @port: Port, host order * - * Return: 0 on success, negative error code on failure + * Return: Socket fd on success, negative error code on failure */ int udp_listen(const struct ctx *c, uint8_t pif, const union inany_addr *addr, const char *ifname, in_port_t port) @@ -1180,7 +1180,7 @@ int udp_listen(const struct ctx *c, uint8_t pif, if (!addr || !inany_v4(addr)) socks[V6][port] = s < 0 ? -1 : s; - return s < 0 ? s : 0; + return s; } /** -- 2.52.0

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[PATCH 2/3] tcp, udp, conf: Don't silently ignore listens on unsupported IP versions
by David Gibson 05 Jan '26

05 Jan '26

Currently, it's possible to explicitly ask for forwarding from an IPv4 address, while disabling IPv4: $ pasta -t 192.0.2.1/12345 -6 or vice versa: $ pasta -t 2001:db8::1/12345 -4 Currently, the impossible to implement forwarding option will be silently ignored. That's potentially confusing since in a complex setup, it might not be obvious why the requested forward isn't taking effect. Specifically, it's ignored at a fairly low level: tcp_listen() and udp_listen() ignore it and return 0. Those run kind of late to give a good error message. Change the low-level functions to return -EACCES (chosen because that's what the kernel will return if you request IPv6 when it's disabled by sysctl). Most callers of {tcp,udp}_listen() ignore the return code, so this is a no-op for them. In the remaining caller, conf_ports_range_except() check for the case explicitly, and provide a meaningful error message. Of itself, this bug is insignificant, but this is a roadblock to having {tcp,udp}_listen() return socket fds, which in turn is a roadblock to my flexible forwarding work. So, might as well fix it. Link: https://bugs.passt.top/show_bug.cgi?id=186 Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 10 ++++++++++ tcp.c | 6 ++---- udp.c | 6 ++---- 3 files changed, 14 insertions(+), 8 deletions(-) diff --git a/conf.c b/conf.c index 70ea168c..cc3c20a9 100644 --- a/conf.c +++ b/conf.c @@ -162,6 +162,16 @@ static void conf_ports_range_except(const struct ctx *c, char optname, optname, optarg); } + if (addr) { + if (!c->ifi4 && inany_v4(addr)) { + die("IPv4 is disabled, can't use -%c %s", + optname, optarg); + } else if (!c->ifi6 && !inany_v4(addr)) { + die("IPv6 is disabled, can't use -%c %s", + optname, optarg); + } + } + for (i = first; i <= last; i++) { if (bitmap_isset(exclude, i)) continue; diff --git a/tcp.c b/tcp.c index e7fa85f3..67007c05 100644 --- a/tcp.c +++ b/tcp.c @@ -2700,16 +2700,14 @@ int tcp_listen(const struct ctx *c, uint8_t pif, /* Restrict to v6 only */ addr = &inany_any6; else if (inany_v4(addr)) - /* Nothing to do */ - return 0; + return -EACCES; } if (!c->ifi6) { if (!addr) /* Restrict to v4 only */ addr = &inany_any4; else if (!inany_v4(addr)) - /* Nothing to do */ - return 0; + return -EACCES; } if (pif == PIF_HOST) { diff --git a/udp.c b/udp.c index eda55c39..8cfa1e1f 100644 --- a/udp.c +++ b/udp.c @@ -1162,16 +1162,14 @@ int udp_listen(const struct ctx *c, uint8_t pif, /* Restrict to v6 only */ addr = &inany_any6; else if (inany_v4(addr)) - /* Nothing to do */ - return 0; + return -EACCES; } if (!c->ifi6) { if (!addr) /* Restrict to v4 only */ addr = &inany_any4; else if (!inany_v4(addr)) - /* Nothing to do */ - return 0; + return -EACCES; } s = pif_sock_l4(c, EPOLL_TYPE_UDP_LISTEN, pif, -- 2.52.0

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[PATCH 1/3] conf: Introduce --no-bindtodevice option for testing
by David Gibson 05 Jan '26

05 Jan '26

We need to support (as best we can) older kernels which don't allow unprivilieged processes to use the SO_BINDTODEVICE socket option. Fallcaks for that case are controlled by the c->no_bindtodevice variable. Currently testing behaviour of those fallbacks requires setting up a test system with a kernel that doesn't support the option, which is pretty awkward. We can test it almost as well and much more easily by adding a command line option to explicitly disable use of SO_BINDTODEVICE. Like --no-splice this is envisaged as something for developers' and testers' convenience, not a supported option for end users. The man page text reflects that. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 2 ++ passt.1 | 6 ++++++ 2 files changed, 8 insertions(+) diff --git a/conf.c b/conf.c index ceb9aa55..70ea168c 100644 --- a/conf.c +++ b/conf.c @@ -962,6 +962,7 @@ static void usage(const char *name, FILE *f, int status) " --no-ndp Disable NDP responses\n" " --no-dhcpv6 Disable DHCPv6 server\n" " --no-ra Disable router advertisements\n" + " --no-bindtodevice Disable SO_BINDTODEVICE\n" " --freebind Bind to any address for forwarding\n" " --no-map-gw Don't map gateway address to host\n" " -4, --ipv4-only Enable IPv4 operation only\n" @@ -1454,6 +1455,7 @@ void conf(struct ctx *c, int argc, char **argv) {"no-dhcpv6", no_argument, &c->no_dhcpv6, 1 }, {"no-ndp", no_argument, &c->no_ndp, 1 }, {"no-ra", no_argument, &c->no_ra, 1 }, + {"no-bindtodevice", no_argument, &c->no_bindtodevice, 1}, {"no-splice", no_argument, &c->no_splice, 1 }, {"freebind", no_argument, &c->freebind, 1 }, {"no-map-gw", no_argument, &no_map_gw, 1 }, diff --git a/passt.1 b/passt.1 index db0d6620..4859d9e5 100644 --- a/passt.1 +++ b/passt.1 @@ -348,6 +348,12 @@ namespace will be silently dropped. Disable Router Advertisements. Router Solicitations coming from guest or target namespace will be ignored. +.TP +.BR \-\-no-bindtodevice +Development/testing option, do not use. Disables use of +SO_BINDTODEVICE socket option. Implicitly enabled on older kernels +which don't permit unprivileged use of SO_BINDTODEVICE. + .TP .BR \-\-freebind Allow any binding address to be specified for \fB-t\fR and \fB-u\fR -- 2.52.0

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