- dev - passt

[PATCH v3 0/6] Add --dhcp-boot and --dhcp-opt options
by Anshu Kumari 01 Jun '26

01 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 | 29 ++++- dhcp.c | 322 ++++++++++++++++++++++++++++++++++++++++++++++++++++---- dhcp.h | 1 + passt.1 | 41 ++++++++ passt.h | 16 +++ 5 files changed, 389 insertions(+), 20 deletions(-) -- 2.54.0

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[PATCH] udp: Provide dummy iov in udp_peek_addr() to avoid Coverity warning
by Jon Maloy 31 May '26

31 May '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

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[PATCH] util, passt: Close daemon-lifetime fds on exit to avoid Coverity warning
by Jon Maloy 31 May '26

31 May '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 29 May '26

29 May '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 28 May '26

28 May '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 0/8] splice() forwarding cleanups
by David Gibson 28 May '26

28 May '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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[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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Startup fd to avoid busywaits
by Lisanna Dettwyler 27 May '26

27 May '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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