[Bug 234576] hastd exits ungracefully

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=234576

--- Comment #15 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:

URL:
https://cgit.FreeBSD.org/src/commit/?id=b7e5c2e008f5b441611830ad3a0329de0882419e

commit b7e5c2e008f5b441611830ad3a0329de0882419e
Author:     Dag-Erling Smørgrav <des@FreeBSD.org>
AuthorDate: 2026-09-08 20:55:15 +0000
Commit:     Dag-Erling Smørgrav <des@FreeBSD.org>
CommitDate: 2026-09-16 13:56:44 +0000

    hastd: Use fixed-length protocol names

    All communication between hastd nodes and internally between hastd and
    its worker children passes through the same pair of send / receive
    functions.  The receive function uses recv(2) with the MSG_WAITALL flag,
    which in theory means we should never get a short read.  However, when
    handing off a socket to a worker child, we also pass a variable-length
    string identifying the type of socket we're passing, and reading this
    string relies on a short read.  This used to work because the arrival of
    the descriptor would interrupt the recv(2) call, but this bug was fixed
    when the AF_UNIX code was rewritten a while ago and hastd has been
    broken ever since.

    Fixing the length of the protocol name to four characters including the
    terminating null solves the short-read bug by never requiring a short
    read (nothing else in hastd requires one).

    Note that this issue appears to have been reported independently first
    by Alessandro Sagratini in PR 234576 and then by Martin Vidovic in
    D57511.  I ended up going in a different direction than Martin's patch,
    but his analysis was invaluable, hence the double credit below.

    PR:             234576
    Reported by:    Martin Vidovic <xtronom@gmail.com>
    MFC after:      1 week
    Event:          EuroBSDcon DevSummit 2026
    Reviewed by:    xtronom_gmail.com, kevans, glebius, gjb
    Differential Revision:  https://reviews.freebsd.org/D59521

 sbin/hastd/proto.c            | 15 +++++----------
 sbin/hastd/proto_impl.h       |  2 +-
 sbin/hastd/proto_socketpair.c |  2 +-
 3 files changed, 7 insertions(+), 12 deletions(-)

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