passt/udp_flow.c, branch podman23739

flow, treewide: Promote priority of selected flow-linked messages

2026-06-09T02:28:20+00:00

Most of out flow specific log messages are debug level for fear of flooding
the logs, even when they report real error conditions that might be off
significance.

Now that we have the mechanisms for log message rate limiting, we can do
better.  Promote many flow related messages to warning or error level, with
rate limiting.  While we're there add ratelimiting to a handful of existing
warning or error level messages.

They general heuristic is to promote messages that report a failure which
is not something that should be triggered by the guest doing something
weird.  This mostly means failures from socket operations we expect to be
legitimate.

Adding the ratelimiting means plumbing the 'now' timestamp through much
more of the code, hence the large churn.

Signed-off-by: David Gibson

flow: Safer errno handling in flowside_connect() callers

2026-06-09T02:18:40+00:00

flowside_connect() behaves much like connect(2) itself, returning -1 on
error with errno set to the error code.  One of the callers, in
udp_flow_sock(), uses the errno code with flow_dbg_perror() *after* it's
called epoll_del() and close() either of which could clobber errno.

Change flowside_connect() to use the more regular convention for internal
functions: return a negative errno code on error, rather than just -1.
Save it in the callers and use that rather than raw errno to print the
message.

Signed-off-by: David Gibson

tap, tcp, udp: Use rate-limited logging

2026-04-15T18:59:35+00:00

Now that rate-limited logging macros are available, promote several
debug messages to higher severity levels.  These messages were
previously kept at debug to prevent guests from flooding host
logs, but with rate limiting they can safely be made visible in
normal operation.

In tap.c, refactor tap4_is_fragment() to use warn_ratelimit() instead
of its ad-hoc rate limiting, and promote the guest MAC address change
message to info level.

In tcp.c, promote the invalid TCP SYN endpoint message to warn level.

In udp.c, promote dropped datagram messages to warn level, and
rate-limit the unrecoverable socket error message.

In udp_flow.c, promote flow allocation failures to err_ratelimit.

Link: https://bugs.passt.top/show_bug.cgi?id=134
Signed-off-by: Anshu Kumari 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

treewide: Spell ASSERT() as assert()

2026-03-20T20:05:29+00:00

The standard library assert(3), at least with glibc, hits our seccomp
filter and dies with SIGSYS before it's able to print a message, making it
near useless.  Therefore, since 7a8ed9459dfe ("Make assertions actually
useful") we've instead used our own implementation, named ASSERT().

This makes our code look slightly odd though - ASSERT() has the same
overall effect as assert(), it's just a different implementation.  More
importantly this makes it awkward to share code between passt/pasta proper
and things that compile in a more typical environment.  We're going to want
that for our upcoming dynamic configuration tool.

Address this by overriding the standard library's assert() implementation
with our own, instead of giving ours its own name.

The standard assert() is supposed to be omitted if NDEBUG is defined,
which ours doesn't do.  Implement that as well, so ours doesn't
unexpectedly differ.  For the -DNDEBUG case we do this by *not* overriding
assert(), since it will be a no-op anyway.  This requires a few places to
add a #include  to let us compile (albeit with warnings) when
-DNDEBUG.

Signed-off-by: David Gibson 
[sbrivio: Fix some conflicts and missing conversions as a result of
 applying "vu_common: Move iovec management into vu_collect()" first]
Signed-off-by: Stefano Brivio

udp: Split activity timeouts for UDP flows

2026-02-15T01:48:34+00:00

Frequent DNS queries over UDP from a container or guest can result
in many sockets shown in ss(8), typically one per flow. This is
expected and harmless, but it can make the output of ss(8) look
noisy and potentially concern users.

This patch splits UDP flow timeouts into two, mirroring the Linux
kernel, and sources the values from kernel parameters. The shorter
timeout is applied to unidirectional flows and minimal bidirectional
exchanges (single datagram and reply), while the longer timeout is
used for bidirectional flows with multiple datagrams on either side.

Link: https://bugs.passt.top/show_bug.cgi?id=197
Suggested-by: Stefano Brivio 
Signed-off-by: Yumei Huang 
Signed-off-by: Stefano Brivio

flow: Remove EPOLLFD_ID_INVALID

2026-01-20T18:37:53+00:00

As all flows are now registered with an epollid at creation, we no
longer need to test if a flow is in epoll.  Remove all related code
including flow_in_epoll() and flow_epollid_clear().

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

flow, fwd: Optimise forwarding rule lookup using epoll ref when possible

2026-01-18T11:48:09+00:00

Now that listening sockets include a reference to the forwarding rule
which created them we can, in many cases, avoid a linear search of the
forwarding table when we want to find the relevant rule.  Instead we
can take the rule index from the socket's epoll reference, and use
that to immediately find the correct rule.

This is conceptually simple, but requires a moderate amount of
plumbing to get the index from the reference through to the rule
lookup.  We still allow fall back to linear search if we don't have
the index, and this may (rarely) be used in the udp_flush_flow() case,
where we could get packets for one flow on a different flow's socket,
rather than through a listening socket as usual.

Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio

flow: Introduce flow_epoll_set() to centralize epoll operations

2026-01-14T00:07:51+00:00

Currently, each flow type (TCP, TCP_SPLICE, PING, UDP) has its own
code to add or modify file descriptors in epoll. This leads to
duplicated boilerplate code across icmp.c, tcp.c, tcp_splice.c, and
udp_flow.c, each setting up epoll_ref unions and calling epoll_ctl()
with flow-type-specific details.

Introduce flow_epoll_set() in flow.c to handle epoll operations for
all flow types in a unified way.

This will be needed to migrate queue pair from an epollfd to another.

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

udp_flow: Assign socket to flow inside udp_flow_sock()

2026-01-14T00:07:51+00:00

Move the assignment of uflow->s[sidei] from the caller (udp_flow_new())
into udp_flow_sock() itself, placing it after the successful connect().

This is a pure refactoring with no functional change.  The socket fd is
now assigned within udp_flow_sock() where the socket is created, rather
than requiring the caller to capture the return value.  On error paths,
uflow->s[sidei] remains at its initialized value of -1 rather than being
set to the negative error code, which is semantically cleaner (though
functionally equivalent given the >= 0 check in udp_flow_close()).

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

udp_flow: remove unneeded epoll_ref indirection

2026-01-14T00:07:51+00:00

The fref union was used to convert flow_sidx_t to uint32_t for
assignment to ref.data.  This is unnecessary since epoll_ref already
contains a flowside member of type flow_sidx_t, so we can assign
directly.

This aligns with how icmp.c and other callers assign flow_sidx_t to
epoll_ref.

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio