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The TCPIPLibs library docs remind us that a socket can be modified via setsockopt() to have a non-default timeout for receive (SO_RCVTIMEO) and send (SO_SNDTIMEO) operations, however neither of these options were honoured if set. Instead, a default timeout of ~60s was given.
This is because although the Internet module stores and propagates (via sbwait()) the timeouts correctly, the underlying tsleep() function is non compliant: it makes no distinction between returning due to a timeout and returning due to being awoken by an event. See
  https://www.freebsd.org/cgi/man.cgi?query=tsleep&sektion=9&manpath=FreeBSD+4.4-RELEASE

for details.

lib/unixenv.c: differentiate between timing out and being awoken, and return EWOULDBLOCK for timeouts.

Aside: select() worked because when tsleep() returned with 0 for a timeout this caused a retry attempt, and the retry loop happens to include its own timer compare, causing select() to return. Now that tsleep() r...