How to disable syncookies & syncache
smithi at nimnet.asn.au
Sun Nov 7 12:38:43 UTC 2010
In freebsd-questions Digest, Vol 335, Issue 14, Message: 2
On Sun, 7 Nov 2010 12:09:26 +0100 Alexander Frolkin <avf at eldamar.org.uk> wrote:
> I spent all day yesterday trying to get my FreeBSD box (8.1-RELEASE,
> amd64) to talk to a Qlogic 4010 iSCSI card.
> The problem is that when the Qlogic card tries to make a connection,
> FreeBSD resets it (SYN, SYN|ACK, ACK, RST).
> If I turn on net.inet.tcp.log_in_vain, I can see a message similar to
> TCP: [172.16.25.2]:30557 to [172.16.25.1]:3260 tcpflags 0x10<ACK>;
> syncache_expand: TSECR 0 != TS 267223, segment rejected
> for each connection attempt.
> I've tried fiddling around with the net.inet.tcp.syn* sysctls, but all
> I've managed to to is change the message to
> TCP: [172.16.25.2]:29387 to [172.16.25.1]:3260 tcpflags 0x10<ACK>;
> syncache_expand: Segment failed SYNCOOKIE authentication, segment
> rejected (probably spoofed)
> (this was with net.inet.tcp.syncookies_only=1, I believe) --- the
> connection still gets reset, as before.
> The only "solution" I've found so far is to comment out the bit of code
> in sys/netinet/tcp_syncache.c that checks if TSECR == TS, but needless
> to say, this is horrible, and will probably create other problems.
> Now, I know what you're probably going to say --- the Qlogic card has a
> broken TCP implementation. While that may well be true, this is the
> card I have and I'm stuck with it, so there's not much I can about that.
> Any suggestions welcome. :-)
Only that if I had such an issue I'd head for net at freebsd.org and post
the above there, where the syncache cookie monsters tend to hang out :)
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