[Bug 293241] sys/netpfil/ipfw/log:bpf test fails intermittently in CI

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=293241

--- Comment #3 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:

URL:
https://cgit.FreeBSD.org/src/commit/?id=38edf96b1787ce3d8c00e4466348dab891c7a9ea

commit 38edf96b1787ce3d8c00e4466348dab891c7a9ea
Author:     Gleb Smirnoff <glebius@FreeBSD.org>
AuthorDate: 2026-02-19 02:39:00 +0000
Commit:     Gleb Smirnoff <glebius@FreeBSD.org>
CommitDate: 2026-02-19 02:53:16 +0000

    tests/ipfw: fix log:bpf test flakyness

    There were several problems:

    o Using 'netstat -B' is not a reliable way to make sure that all tcpdumps
      have attached to bpf(4).  The problem is that tcpdump (via libpcap) does
      several ioctl(2)s after the attach including two BIOCSETF.  Each of them
      flushes the input buffer.  So we can see tcpdump attached in 'netstat -B'
      and start sending packets and the packet will be captured by bpf(4)
      before BIOCSETF and freed and tcpdump won't read anything.  Instead of
      using netstat(1), use ps(1) and make sure each tcpdump is blocked on the
      "bpf" wait channel, which guarantees it is done with ioctl(2)s and is now
      blocked in read(2).
    o Using 'nc -w 0' sets timeout not only on the connect(2) (as documented)
      but also on poll(2), which is not documented.  There is a race in shell
      that will make stdin not yet filled by 'echo foo' when nc(1) does
      poll(2).  With zero timeout, this poll(2) will immediately return and nc
      will exit.
    o The waiting loop had two errors: using wrong variable name as well as
      invoking a subshell, that actually can't wait on the pid.
    o The reading tcpdump was lacking '-q' option, that prevents any protocol
      interpretations.  Sometimes, when random port chosen by nc(1) would
      match some well-known (to tcpdump) port, the output would differ from
      the expected.

    PR:     293241

 tests/sys/netpfil/ipfw/log.sh | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

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