CVS commit: src/sys/netinet

["Christos Zoulas" <christos%netbsd.org@localhost>]

Module Name:    src
Committed By:   christos
Date:           Mon Apr 27 16:50:17 UTC 2015

Modified Files:
        src/sys/netinet: tcp_output.c

Log Message:
Apply Revision 220794 from FreeBSD to avoid dup ACKs:

When checking to see if a window update should be sent to the remote peer,
don't force a window update if the window would not actually grow due to
window scaling.  Specifically, if the window scaling factor is larger than
2 * MSS, then after the local reader has drained 2 * MSS bytes from the
socket, a window update can end up advertising the same window.  If this
happens, the supposed window update actually ends up being a duplicate ACK.
This can result in an excessive number of duplicate ACKs when using a
higher maximum socket buffer size.

Pointed out by Ricky Charlet, in tech-net.


To generate a diff of this commit:
cvs rdiff -u -r1.181 -r1.182 src/sys/netinet/tcp_output.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.