https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=260116
Bug ID: 260116
Summary: [sctp] POLLOUT/EVFILT_WRITE is always true for
poll/kqueue
Product: Base System
Version: 13.0-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
It seems like POLLOUT/EVFILT_WRITE always is true for SCTP sockets even if the
socket send buffer is full.
Besides this, it should also account for SO_SNDLOWAT but it is possible that we
will get this for "free" since it looks like the functionality already is
there.
Based on some experiments (which might be faulty), SCTP sockets doesn't use
struct sockbuf in the same way as TCP uses it. A lot of the fields in that
struct are 0 for SCTP sockets since it also has its own structs.
This seems to affect filt_sowrite() in
(https://github.com/freebsd/freebsd-src/blob/main/sys/kern/uipc_socket.c). More
specifically, this line:
kn->kn_data = sbspace(&so->so_snd);
I have tested to replace that line with:
kn->kn_data = (so->so_snd.sb_hiwat - so->so_snd.sb_acc);
Which seems to do the trick, but I expect this to have side effects.
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