Date: Mon, 5 Oct 2009 14:49:16 +0000 (UTC) From: Robert Watson <rwatson@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/kern uipc_usrreq.c Message-ID: <200910051449.n95EneJu096884@repoman.freebsd.org>
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rwatson 2009-10-05 14:49:16 UTC
FreeBSD src repository
Modified files:
sys/kern uipc_usrreq.c
Log:
SVN rev 197775 on 2009-10-05 14:49:16Z by rwatson
First cut at implementing SOCK_SEQPACKET support for UNIX (local) domain
sockets. This allows for reliable bi-directional datagram communication
over UNIX domain sockets, in contrast to SOCK_DGRAM (M:N, unreliable) or
SOCK_STERAM (bi-directional bytestream). Largely, this reuses existing
UNIX domain socket code. This allows applications requiring record-
oriented semantics to do so reliably via local IPC.
Some implementation notes (also present in XXX comments):
- Currently we lack an sbappend variant able to do datagrams and control
data without doing addresses, so we mark SOCK_SEQPACKET as PR_ADDR.
Adding a new variant will solve this problem.
- UNIX domain sockets on FreeBSD provide back-pressure/flow control
notification for stream sockets by manipulating the send socket
buffer's size during pru_send and pru_rcvd. This trick works less well
for SOCK_SEQPACKET as sosend_generic() uses sb_hiwat not just to
manage blocking, but also to determine maximum datagram size. Fixing
this requires rethinking how back-pressure is done for SOCK_SEQPACKET;
in the mean time, it's possible to get EMSGSIZE when buffers fill,
instead of blocking.
Discussed with: benl
Reviewed by: bz, rpaulo
MFC after: 3 months
Sponsored by: Google
Revision Changes Path
1.234 +123 -16 src/sys/kern/uipc_usrreq.c
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