May 2026 - dev

[PATCH 0/8] splice() forwarding cleanups
by David Gibson 05 Jun '26

05 Jun '26

As we discussed on an earlier call, while fixing bug 202 I noticed a number of warts in the surrounding splice() forwarding code. Most are just things that are longer or harder to follow than they need to be, but in some cases there may be real (if unlikely to trigger) bugs. Here's a collection of fixes. David Gibson (8): tcp_splice: Remove never-invoked SO_RCVLOWAT logic tcp_splice: Simplify EPOLLRDHUP / eof / FIN handling tcp_splice: Improve EOF exit condition for the loop tcp_splice: Remove goto from forwarding loop tcp_splice: Simplify shutdown(2) handling tcp_splice: Simplify / correct OUT_WAIT flag handling tcp_splice: Remove questionable "optimisation" of pending bytes tracking tcp_splice: Exit forwarding earlier when stalled read side tcp_splice.c | 100 ++++++++++++++++----------------------------------- 1 file changed, 31 insertions(+), 69 deletions(-) -- 2.54.0

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Startup fd to avoid busywaits
by Lisanna Dettwyler 03 Jun '26

03 Jun '26

Hello! I would like to propose a patch that allows the invoker to pass a "ready fd" on startup that gets written to once the setup has been completed, similar to slirp4netns's `--ready-fd` flag. Currently we have to poll the interface in a loop to wait for setup to be completed, and it would be much better if we could instead block on fd activity. Just wanted to check if such a contribution would be welcome before putting in the work of authoring it, or if there's already a better way to wait for the interface to come up. This is our current implementation: https://github.com/NixOS/nix/pull/15919/changes#diff-2a9176262efad1ef345d88… Thanks, Lisanna

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[PATCH] udp: Provide dummy iov in udp_peek_addr() to avoid Coverity warning
by Jon Maloy 02 Jun '26

02 Jun '26

udp_peek_addr() initialises struct msghdr without setting msg_iov, leaving it implicitly NULL. Coverity flags this as FORWARD_NULL, believing recvmsg() will dereference the NULL pointer. In practice, msg_iovlen being zero means the kernel never touches msg_iov, so the warning is a false positive. We now provide a one-byte dummy iov to make msg_iov non-NULL, hence suppressing this warning without changing the function's behaviour. Signed-off-by: Jon Maloy <jmaloy(a)redhat.com> --- udp.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/udp.c b/udp.c index c28d6ee2..f648cb8b 100644 --- a/udp.c +++ b/udp.c @@ -734,9 +734,16 @@ static int udp_peek_addr(int s, union sockaddr_inany *src, { char sastr[SOCKADDR_STRLEN], dstr[INANY_ADDRSTRLEN]; char cmsg[PKTINFO_SPACE]; + char dummy; + struct iovec iov = { + .iov_base = &dummy, + .iov_len = sizeof(dummy), + }; struct msghdr msg = { .msg_name = src, .msg_namelen = sizeof(*src), + .msg_iov = &iov, + .msg_iovlen = 1, .msg_control = cmsg, .msg_controllen = sizeof(cmsg), }; -- 2.52.0

2 1

[PATCH] util, passt: Close daemon-lifetime fds on exit to avoid Coverity warning
by Jon Maloy 02 Jun '26

02 Jun '26

conf_open_files() opens four file descriptors (fd_tap_listen, fd_repair_listen, pidfile_fd, fd_control_listen) that are held for the entire daemon lifetime. Because no close() call exists for them anywhere, Coverity flags each as INCOMPLETE_DEALLOCATOR. This is clearly a false positive, but we still want to get rid of this warning. We now register the execution context so that passt_exit() can use to close these descriptors before calling _exit(). All exit paths (signal handler, die(), die_perror()) funnel through passt_exit(), so this covers all cases. Signed-off-by: Jon Maloy <jmaloy(a)redhat.com> --- log.h | 2 ++ passt.c | 1 + util.c | 22 ++++++++++++++++++++++ 3 files changed, 25 insertions(+) diff --git a/log.h b/log.h index 69cfb507..079f429c 100644 --- a/log.h +++ b/log.h @@ -63,7 +63,9 @@ extern bool debug_flag; /* This would make more sense in util.h, but because we use it in die(), that * would cause awkward circular reference problems. */ +struct ctx; void passt_exit(int status) __attribute__((noreturn)); +void passt_exit_set_ctx(struct ctx *c); #define LOGFILE_SIZE_DEFAULT (1024 * 1024UL) #define LOGFILE_CUT_RATIO 30 /* When full, cut ~30% size */ diff --git a/passt.c b/passt.c index b6fc12d4..ec6aa57a 100644 --- a/passt.c +++ b/passt.c @@ -392,6 +392,7 @@ int main(int argc, char **argv) sock_probe_features(&c); conf(&c, argc, argv); + passt_exit_set_ctx(&c); trace_init(c.trace); pasta_netns_quit_init(&c); diff --git a/util.c b/util.c index b64c29ed..f15b1f9a 100644 --- a/util.c +++ b/util.c @@ -1097,6 +1097,17 @@ void abort_with_msg(const char *fmt, ...) abort(); } +static struct ctx *exit_cleanup_ctx; + +/** + * passt_exit_set_ctx() - Register context for cleanup on exit + * @c: Execution context + */ +void passt_exit_set_ctx(struct ctx *c) +{ + exit_cleanup_ctx = c; +} + /** * passt_exit() - Perform vital cleanup and exit * @@ -1108,6 +1119,17 @@ void abort_with_msg(const char *fmt, ...) */ void passt_exit(int status) { + if (exit_cleanup_ctx) { + if (exit_cleanup_ctx->fd_tap_listen >= 0) + close(exit_cleanup_ctx->fd_tap_listen); + if (exit_cleanup_ctx->fd_repair_listen >= 0) + close(exit_cleanup_ctx->fd_repair_listen); + if (exit_cleanup_ctx->pidfile_fd >= 0) + close(exit_cleanup_ctx->pidfile_fd); + if (exit_cleanup_ctx->fd_control_listen >= 0) + close(exit_cleanup_ctx->fd_control_listen); + } + /* Make sure we don't leave the pcap file truncated */ if (pcap_fd != -1 && fsync(pcap_fd)) warn_perror("Failed to flush pcap file, it might be truncated"); -- 2.52.0

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[PATCH v2 0/6] Add --dhcp-boot and --dhcp-opt options
by Anshu Kumari 02 Jun '26

02 Jun '26

This series adds support for custom DHCP options in passt, enabling network boot (PXE/UEFI HTTP Boot) and arbitrary DHCP option injection. Two new command-line flags are introduced: --dhcp-boot URL Sets the boot file URL (DHCP option 67 and the legacy boot file field) --dhcp-opt CODE,VALUE Sets any DHCP option by numeric code, with type-aware parsing per RFC 2132 The DHCP reply path is extended with option overload support (RFC 2132 option 52), allowing options to overflow into the file and sname fields when the standard options area is full. Anshu Kumari (6): conf: Add --dhcp-opt command-line option conf: Add --dhcp-boot command-line option dhcp: Add option type table and value parser dhcp: Refactor fill_one() to operate on a generic buffer dhcp: Add option overload doc: Add --dhcp-boot and --dhcp-opt to man page conf.c | 64 +++++++++++++- dhcp.c | 253 +++++++++++++++++++++++++++++++++++++++++++++++++++----- dhcp.h | 17 ++++ passt.1 | 41 +++++++++ passt.h | 16 ++++ 5 files changed, 370 insertions(+), 21 deletions(-) -- 2.54.0

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[PATCH] apparmor: Fix signaling issues from podman
by Bittner, Jan 01 Jun '26

01 Jun '26

This fixes a bug that causes a crash in podman. Podman uses signal to communicate with pasta. Without this patch apparmor does not allow podman to signal pasta and kills pasta instead. Killing pasta causes podman to crash. You can reproduce this by starting a rootless podman socket and starting a container via the socket using podman remote or docker. Links: https://bugs.launchpad.net/ubuntu/+source/passt/+bug/2154379 Signed-off-by: Jan Philipp Bittner <jan.bittner(a)kdo.de> --- contrib/apparmor/usr.bin.pasta | 3 +++ 1 file changed, 3 insertions(+) diff --git a/contrib/apparmor/usr.bin.pasta b/contrib/apparmor/usr.bin.pasta index 56b5024..b0838de 100644 --- a/contrib/apparmor/usr.bin.pasta +++ b/contrib/apparmor/usr.bin.pasta @@ -18,6 +18,9 @@ include <tunables/global> profile pasta /usr/bin/pasta{,.avx2} flags=(attach_disconnected) { include <abstractions/pasta> + # Allow podman to signal pasta + signal (receive) peer=podman, + # Alternatively: include <abstractions/user-tmp> /tmp/** rw, # tap_sock_unix_open(), # tap_sock_unix_init(), pcap(), -- 2.43.0

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[PATCH v2 1/6] conf: Add --dhcp-opt command-line option
by Anshu Kumari 28 May '26

28 May '26

Introduce the --dhcp-opt flag that allows setting arbitrary DHCP options from command-line in the form of [Option CODE,VALUE]. This patch adds the option storage in struct ctx and CLI parsing; the type-aware value parser and DHCP reply injection follow in subsequent patches. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari <anskuma(a)redhat.com> --- v2: - Added kerneldoc for @custom_opts, @custom_opts.code, @custom_opts.str, and @custom_opts_count in struct ctx - Removed len and val[255] fields from struct (moved to patch 3) - Removed braces from case 33, moved declarations (optcode, comma, end) to function scope - Renamed code → optcode to follow function-scope convention --- conf.c | 34 +++++++++++++++++++++++++++++++++- passt.h | 12 ++++++++++++ 2 files changed, 45 insertions(+), 1 deletion(-) diff --git a/conf.c b/conf.c index 029b9c7..89d2127 100644 --- a/conf.c +++ b/conf.c @@ -47,6 +47,7 @@ #include "lineread.h" #include "isolation.h" #include "log.h" +#include "dhcp.h" #include "vhost_user.h" #include "epoll_ctl.h" #include "conf.h" @@ -616,7 +617,8 @@ static void usage(const char *name, FILE *f, int status) " -S, --search LIST Space-separated list, search domains\n" " a single, empty option disables the DNS search list\n" " -H, --hostname NAME Hostname to configure client with\n" - " --fqdn NAME FQDN to configure client with\n"); + " --fqdn NAME FQDN to configure client with\n" + " --dhcp-opt CODE,VAL Set DHCP option by code\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); else @@ -844,6 +846,10 @@ static void conf_print(const struct ctx *c) info(" router: %s", inet_ntop(AF_INET, &c->ip4.guest_gw, buf, sizeof(buf))); + for (i = 0; i < c->custom_opts_count; i++) + info(" option %u: %s", + c->custom_opts[i].code, + c->custom_opts[i].str); } for (i = 0; i < ARRAY_SIZE(c->ip4.dns); i++) { @@ -1233,6 +1239,7 @@ void conf(struct ctx *c, int argc, char **argv) {"migrate-no-linger", no_argument, NULL, 30 }, {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, + {"dhcp-opt", required_argument, NULL, 33 }, { 0 }, }; const char *optstring = "+dqfel:hs:c:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:"; @@ -1248,10 +1255,13 @@ void conf(struct ctx *c, int argc, char **argv) uint8_t prefix_len_from_opt = 0; unsigned int ifi4 = 0, ifi6 = 0; const char *logfile = NULL; + unsigned long optcode; char *runas = NULL; size_t logsize = 0; + const char *comma; long fd_tap_opt; int name, ret; + char *end; uid_t uid; gid_t gid; @@ -1465,6 +1475,28 @@ void conf(struct ctx *c, int argc, char **argv) die("Can't display statistics if not running in foreground"); c->stats = strtol(optarg, NULL, 0); break; + case 33: + comma = strchr(optarg, ','); + if (!comma) + die("--dhcp-opt requires Option CODE,VALUE format"); + + optcode = strtoul(optarg, &end, 0); + if (end != comma || optcode < 1 || optcode > 254) + die("DHCP option code must be 1-254: %s", + optarg); + + if (c->custom_opts_count >= MAX_CUSTOM_DHCP_OPTS) + die("Too many --dhcp-opt entries (max %d)", + MAX_CUSTOM_DHCP_OPTS); + + c->custom_opts[c->custom_opts_count].code = optcode; + if (snprintf_check(c->custom_opts[c->custom_opts_count].str, + sizeof(c->custom_opts[0].str), + "%s", comma + 1)) + die("DHCP option value too long: %s", + comma + 1); + c->custom_opts_count++; + break; case 'd': c->debug = 1; c->quiet = 0; diff --git a/passt.h b/passt.h index 1726965..3a0816f 100644 --- a/passt.h +++ b/passt.h @@ -182,6 +182,10 @@ struct ip6_ctx { * @dns_search: DNS search list * @hostname: Guest hostname * @fqdn: Guest FQDN + * @custom_opts: User-specified DHCP options from --dhcp-opt + * @custom_opts.code: DHCP option code + * @custom_opts.str: Original string value from command line + * @custom_opts_count: Number of entries in @custom_opts * @ifi6: Template interface for IPv6, -1: none, 0: IPv6 disabled * @ip6: IPv6 configuration * @pasta_ifn: Name of namespace interface for pasta @@ -263,6 +267,14 @@ struct ctx { char hostname[PASST_MAXDNAME]; char fqdn[PASST_MAXDNAME]; +#define MAX_CUSTOM_DHCP_OPTS 32 + + struct { + uint8_t code; + char str[256]; + } custom_opts[MAX_CUSTOM_DHCP_OPTS]; + int custom_opts_count; + int ifi6; struct ip6_ctx ip6; -- 2.54.0

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[PATCH v2 2/6] conf: Add --dhcp-boot command-line option
by Anshu Kumari 28 May '26

28 May '26

Introduce the --dhcp-boot flag that sets the boot file URL for network boot specially for ipxe. This patch adds the option storage and CLI parsing. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari <anskuma(a)redhat.com> --- v2: - Removed separate dhcp_boot[PATH_MAX] field — --dhcp-boot foo now stores into custom_opts[] as code 67 (same as --dhcp-opt 67,foo) --- conf.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/conf.c b/conf.c index 89d2127..ae8ee26 100644 --- a/conf.c +++ b/conf.c @@ -618,6 +618,7 @@ static void usage(const char *name, FILE *f, int status) " a single, empty option disables the DNS search list\n" " -H, --hostname NAME Hostname to configure client with\n" " --fqdn NAME FQDN to configure client with\n" + " --dhcp-boot URL Boot file URL for network boot\n" " --dhcp-opt CODE,VAL Set DHCP option by code\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); @@ -1239,6 +1240,7 @@ void conf(struct ctx *c, int argc, char **argv) {"migrate-no-linger", no_argument, NULL, 30 }, {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, + {"dhcp-boot", required_argument, NULL, 32 }, {"dhcp-opt", required_argument, NULL, 33 }, { 0 }, }; @@ -1475,6 +1477,18 @@ void conf(struct ctx *c, int argc, char **argv) die("Can't display statistics if not running in foreground"); c->stats = strtol(optarg, NULL, 0); break; + case 32: + if (c->custom_opts_count >= MAX_CUSTOM_DHCP_OPTS) + die("Too many DHCP options (max %d)", + MAX_CUSTOM_DHCP_OPTS); + + c->custom_opts[c->custom_opts_count].code = 67; + if (snprintf_check(c->custom_opts[c->custom_opts_count].str, + sizeof(c->custom_opts[0].str), + "%s", optarg)) + die("Boot file name too long: %s", optarg); + c->custom_opts_count++; + break; case 33: comma = strchr(optarg, ','); if (!comma) -- 2.54.0

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[PATCH 0/2] Fix a Coverity reported socket leak
by David Gibson 28 May '26

28 May '26

I got coverity working for me again, version 2026.3.0. This pointed out a potentially fairly nasty socket leak in tcp_listen_handler(). Here's a series that fixes it. David Gibson (2): tcp, tcp_splice: Make helper for setting SO_LINGER socket option tcp: Don't leak sockets on error paths tcp.c | 42 ++++++++++++++++++++++++++---------------- tcp_conn.h | 3 +++ tcp_splice.c | 20 +++----------------- 3 files changed, 32 insertions(+), 33 deletions(-) -- 2.54.0

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passt: new version 2026_05_26.038c51e available
by Stefano Brivio 27 May '26

27 May '26

The new version with tag 2026_05_26.038c51e includes the following changes: 038c51e vhost_user: Offer VIRTIO_NET_F_GUEST_CSUM 196a9e5 ip: Wrap CASE macro body in braces for pre-C23 compatibility da00969 tcp_splice: Simplify tracking of read/written bytes ac9814e tcp_splice: Clean up flow control path for splice forwarding bda8230 tcp_splice: Avoid missing EOF recognition while forwarding aa6b796 tcp_splice: Improve error reporting 21ea343 tcp_vu: Support multibuffer frames in tcp_vu_send_flag() feb9a11 tcp_vu: Support multibuffer frames in tcp_vu_sock_recv() f8cace2 tcp_vu: Build headers on the stack and write them into the iovec 92845dd tcp: Encode checksum computation flags in a single parameter dec66c0 udp: Pass iov_tail to udp_update_hdr4()/udp_update_hdr6() 9361b6b iov: Introduce IOV_PUSH_HEADER() macro 28ee143 udp_vu: Allow virtqueue elements with multiple iovec entries 76fd546 selinux: Allow pasta to create and use its control socket when started by Podman cea2d19 Makefile: Remove misleading comments on BASE_*FLAGS 5038f92 netlink: Fix comments to variables for netlink sockets and sequence d00255b netlink: Use regular request/response netlink socket for initial neighbour sync b64ef53 conf, repair, tap: Document reasons for blocking Unix sockets 5ef0fc4 tap: Report accept() errors 1d16476 treewide: Add SOCK_CLOEXEC to accept() calls that are missing it db798fc vhost-user: Centralise Ethernet frame padding in vu_collect() and vu_pad() de6387a tcp: Pass explicit data length to tcp_fill_headers() d83470f vu_common: Pass explicit frame length to vu_flush() 533ef11 pcap: Pass explicit L2 length to pcap_iov() aa78f63 checksum: Pass explicit L4 length to checksum functions 7cd5afb udp_vu: Pass iov explicitly to helpers instead of using file-scoped array ee0ba3f udp_vu: Move virtqueue management from udp_vu_sock_recv() to its caller d3a4868 vu_common: Move vnethdr setup into vu_flush() d7259ea iov: Add iov_memcpy() to copy data between iovec arrays a804574 iov: Introduce iov_memset() bcc3d37 util: Fix changes to assert_with_msg() 296d7e3 fwd_rule: Allow parsing * as a forwarding address 666ef9e fwd_rule: Don't attempt dual stack listen()s if only one IP family 8bb21e3 test: Add test for builds with -DNDEBUG e514945 Fix build with -DNDEBUG fd4b637 test: Extend exeter build tests to cover more recent binaries ab12293 lib/term: Quote tr character ranges to prevent glob expansion 9b1ef47 pesto: Run static checkers on pesto sources bf63970 passt-repair: Run static checkers 3c6e797 passt-repair: Simplify construction of Unix path from inotify 1254a1f passt-repair: Split out inotify handling to its own function a2a2f40 Makefile: Split static checker targets b356b62 cppcheck, clang-tidy: Static checkers don't need non-preprocessor flags fb9be08 Makefile: Split $(FLAGS) into cpp and cc components 88ce87e Makefile: Add header dependencies for secondary binaries 9015b76 Makefile: Remove unhelpful $(HEADERS) variable d4632a4 Makefile: Use common binary compilation rule 59b14b2 Makefile: Make conditional definition of $(BIN) clearer 1cd6276 Makefile: Use make variables for static checker configuration 4de7c38 clang-tidy: Suppress some new unhelpful new warnings 97e478b treewide: Make some additional variables static 90f175d packet, clang-tidy: Packet pool buffers are not NULL 7bafe71 clang-tidy: Suppress sscanf() warning harder a82a217 clang-tidy: Squash inconsistent brace warnings in foreach macros db02221 conf: Fix not-actually-const parameter to conf_runas() and conf_ugid() 5b3ca87 virtio: Reduce scope of variable 1e6b638 netlink: erromsg should be const in nl_status() https://passt.top/passt/log/?qt=range&q=2026_05_07.1afd4ed..2026_05_26.038c… Packages: - Alpine Linux: https://pkgs.alpinelinux.org/packages?name=passt - Arch Linux: https://www.archlinux.org/packages/extra/x86_64/passt/ https://archlinuxarm.org/packages/aarch64/passt https://archlinuxarm.org/packages/armv7h/passt - Chimera: https://pkgs.chimera-linux.org/packages?name=passt - Clear Linux: https://github.com/clearlinux-pkgs/passt/ - Copr (CentOS Stream, EPEL, Fedora, Mageia): https://copr.fedorainfracloud.org/coprs/sbrivio/passt/build/10514454/ permanent mirror: https://passt.top/builds/copr/0^20260526.g038c51e/ - Debian tracker: https://tracker.debian.org/pkg/passt - Fedora updates: https://bodhi.fedoraproject.org/updates/?packages=passt - Gentoo versions: https://packages.gentoo.org/packages/net-misc/passt - GNU Guix: https://packages.guix.gnu.org/packages/passt/ - Homebrew: https://formulae.brew.sh/formula/passt - NixOS: https://github.com/NixOS/nixpkgs/tree/nixos-unstable/pkgs/by-name/pa/passt - openSUSE: https://software.opensuse.org/package/passt - OpenMandriva: https://github.com/OpenMandrivaAssociation/passt/tree/master - PLD Linux: https://git.pld-linux.org/cgi-bin/gitweb.cgi?p=packages/passt.git - Solus: https://github.com/getsolus/packages/tree/main/packages/p/passt - Ubuntu tracker: https://launchpad.net/ubuntu/+source/passt - Void Linux: https://voidlinux.org/packages/?q=passt - Static builds: - Package for other RPM-based distributions, x86_64 only: https://passt.top/builds/latest/x86_64/passt-g038c51e-1.x86_64.rpm - x86_64 static binaries: https://passt.top/builds/latest/x86_64/ - Debian package, from x86_64 static build: https://passt.top/builds/latest/x86_64/passt_038c51e-1_all.deb -- Stefano

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