oops/bug in tcp, SACK doesn't work?

Perhaps this has been covered somewhere before, but for some reason it doesn't look like the 2.4.7 (and previous 2.4.x?) kernels responds to SACK correctly. Instead of just resending the missing packet Linux resends the entire packet stream as if it never received the SACK.

Only reason I noticed this was that I was debugging connection problems with our servers that were running 2.4.5. I didn't figure the problem out for several days, when I exhausted all else I decided it must be the checksum of the retransmitted packets. With that in hand a simple google search turned up that there was already a patch for this included in the 2.4.7 kernel. Doh!

Hence I am now scanning through 100-200 emails a day with the rest of you just trying to keep up on the issues and bugs that affect me. There must be a place to look for current and fixed bugs without pouring over change logs and the entire mailing list?

In any case both of these problems were easily duplicated with three machines. One of the machines was used as a router running NIST net emulator ( http://snad.ncsl.nist.gov/itg/nistnet/ ) that allows you to set packet delay, bandwidth and loss. This is a free implementation for Linux that is currently in useable alpha (yup sometimes it crashes the router when loaded), but hey it works reliable enough to get some testing done.

Marty Poulin
[email protected]
Lead Programmer
Host/Client Communications
Playnet Inc./Cornered Rat Software