- dev - passt

[PATCH v3 1/5] util: Be more defensive about buffer overruns in read_file()
by David Gibson 07 Jan '26

07 Jan '26

clang-21.1.7 complains about read_file(), thinking that total_read might come to exceed buf_size, leading to an out of bounds access at the end of the function. In fact, the semantics of read()'s return mean this can't ever happen. But we already have to check for the total_read == buf_size case, so it's basically free to change it to >= and suppress the error. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> Reviewed-by: Laurent Vivier <lvivier(a)redhat.com> --- util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/util.c b/util.c index 27303950..a48f727c 100644 --- a/util.c +++ b/util.c @@ -715,7 +715,7 @@ static ssize_t read_file(const char *path, char *buf, size_t buf_size) close(fd); - if (total_read == buf_size) { + if (total_read >= buf_size) { buf[buf_size - 1] = '\0'; return -ENOBUFS; } -- 2.52.0

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[PATCH] udp_vu: Discard datagrams when RX virtqueue is not usable
by Laurent Vivier 07 Jan '26

07 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

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[PATCH v2 2/5] migrate: Don't use terminator element for versions[] array
by David Gibson 07 Jan '26

07 Jan '26

When scanning the versions[] array we use a dummy entry to detect when we're finished. Use ARRAY_SIZE() instead, which is almost as easy, a little safer, and doesn't cause clang-tidy 21.1.7 to complain. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> Reviewed-by: Laurent Vivier <lvivier(a)redhat.com> --- migrate.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/migrate.c b/migrate.c index 48d63a07..a70ea7b7 100644 --- a/migrate.c +++ b/migrate.c @@ -123,7 +123,6 @@ static const struct migrate_version versions[] = { * MSS and omitted timestamps, which meant it usually wouldn't work. * Therefore we don't attempt to support compatibility with it. */ - { 0 }, }; /* Current encoding version */ @@ -180,6 +179,7 @@ static const struct migrate_version *migrate_target_read_header(int fd) const struct migrate_version *v; struct migrate_header h; uint32_t id, compat_id; + unsigned i; if (read_all_buf(fd, &h, sizeof(h))) return NULL; @@ -196,9 +196,9 @@ static const struct migrate_version *migrate_target_read_header(int fd) return NULL; } - for (v = versions; v->id; v++) - if (v->id <= id && v->id >= compat_id) - return v; + for (i = 0; i < ARRAY_SIZE(versions); v++) + if (versions[i].id <= id && versions[i].id >= compat_id) + return &versions[i]; errno = ENOTSUP; err("Unsupported device state version: %u", id); -- 2.52.0

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[PATCH v2 1/5] util: Be more defensive about buffer overruns in read_file()
by David Gibson 07 Jan '26

07 Jan '26

clang-21.1.7 complains about read_file(), thinking that total_read might come to exceed buf_size, leading to an out of bounds access at the end of the function. In fact, the semantics of read()'s return mean this can't ever happen. But we already have to check for the total_read == buf_size case, so it's basically free to change it to >= and suppress the error. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> Reviewed-by: Laurent Vivier <lvivier(a)redhat.com> --- util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/util.c b/util.c index 27303950..a48f727c 100644 --- a/util.c +++ b/util.c @@ -715,7 +715,7 @@ static ssize_t read_file(const char *path, char *buf, size_t buf_size) close(fd); - if (total_read == buf_size) { + if (total_read >= buf_size) { buf[buf_size - 1] = '\0'; return -ENOBUFS; } -- 2.52.0

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[PATCH 0/5] Fixes for Fedora 43 (or other bitrot)
by David Gibson 07 Jan '26

07 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

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[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

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[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

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[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

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[PATCH 0/3] Allow listen functions to return fds
by David Gibson 05 Jan '26

05 Jan '26

For future forwarding changes, it makes more sense for the tcp and udp listen functions to return socket fds, rather than just success / failure. Make the change, fixing bug 186 and adding a debugging option along the way. Link: https://bugs.passt.top/show_bug.cgi?id=186 David Gibson (3): conf: Introduce --no-bindtodevice option for testing tcp, udp, conf: Don't silently ignore listens on unsupported IP versions tcp, udp: Make {tcp,udp}_listen() return socket fds conf.c | 26 +++++++++++++++++++------- passt.1 | 6 ++++++ tcp.c | 13 ++++--------- udp.c | 10 ++++------ 4 files changed, 33 insertions(+), 22 deletions(-) -- 2.52.0

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[PATCH 0/7] flow: Introduce flow_epoll_set() to centralize epoll operations
by Laurent Vivier 27 Dec '25

27 Dec '25

Currently, each protocol handler (TCP, TCP splice, ICMP/ping, UDP) has its own code to add or modify file descriptors in epoll. This leads to duplicated boilerplate across icmp.c, tcp.c, tcp_splice.c, and udp_flow.c, with each setting up epoll_ref unions and calling epoll_ctl() with flow-type-specific details. This series introduces flow_epoll_set() in flow.c to handle epoll operations for all flow types in a unified way. The function evolves across the series, progressively absorbing more responsibilities: 1. Initial version takes explicit fd, events, and ctx parameters 2. Events computation is moved inside the function by relocating tcp_conn_epoll_events() and tcp_splice_conn_epoll_events() into flow.c 3. The ctx parameter is removed by using epoll_id_to_fd[EPOLLFD_ID_DEFAULT] directly for new flows 4. The fd parameter is removed by having the function extract the file descriptor from the flow structure based on the epoll type The final API is simply: int flow_epoll_set(enum epoll_type type, const struct flow_common *f, unsigned int sidei); This centralized approach will be essential for queue pair migration in the upcoming multithreading work, where flows need to be moved between different epoll instances owned by different threads. Preparatory patches: - Patch 1 fixes EPOLL_TYPE_TCP_TIMER to use the actual timer fd - Patch 2 refactors udp_flow_sock() to assign the socket internally - Patch 3 refactors tcp_splice_conn_epoll_events() to per-side computation Core series: - Patch 4 introduces the initial flow_epoll_set() function - Patch 5 removes the ctx parameter - Patch 6 moves event computation inside flow_epoll_set() - Patch 7 removes the fd parameter, completing the refactoring Laurent Vivier (7): tcp: Update EPOLL_TYPE_TCP_TIMER fd udp_flow: Assign socket to flow inside udp_flow_sock() tcp_splice: Refactor tcp_splice_conn_epoll_events() to per-side computation flow: Introduce flow_epoll_set() to centralize epoll operations flow: Use epoll_id_to_fd[EPOLLFD_ID_DEFAULT] in flow_epollid_set() flow: Compute epoll events inside flow_epoll_set() flow: Have flow_epoll_set() retrieve file descriptor from flow structure flow.c | 158 +++++++++++++++++++++++++++++++++++++++++++++++++++ flow.h | 4 ++ icmp.c | 8 +-- tcp.c | 68 +++------------------- tcp_splice.c | 77 +++++-------------------- udp_flow.c | 17 ++---- 6 files changed, 190 insertions(+), 142 deletions(-) -- 2.51.1

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