nanog mailing list archives
Re: SYN flood messages flooding my mailbox
From: Matt Bush <xomox () boris eden com>
Date: Tue, 17 Sep 1996 13:29:42 -0500 (CDT)
In message <199609161637.MAA20184 () netaxs com>, Avi Freedman writes:implementation. This is a denial of service exposure that has gone unaddressed in host implementations until recently. BSD now uses a hash table on the TCP PCBs (protocol control blocks in the kernel) and with change of removal of the check can support close to 64K-2000 PCBsHmm. Interesting. I was told that NetBSD did not... Which version of BSD should I look at? A hash table on a static array of PCBs is a much better solution than letting a linked list get to 2000 entries...Oops. That's in a BSDI patch (PATCH K210-019) but I'm not sure about FreeBSD or NetBSD distributions since I don't have one handy.
I'm not sure about prior releases, but FreeBSD 2.1.0 and above do hash PCB's, with a default hash size of 128. The constant name is TCBHASHSIZE in netinet/tcp_subr.c. To raise it, just add options "TCBHASHSIZE=2048" # More capable TCB hash ... and if you feel the need, add options "UDBHASHSIZE=1024" # More capable UDB hash to your kern config file.
Curtis ps- (My 6 year old has a FreeBSD system, but its 2.0.5. Got to get him to upgrade. :)
Version 2.1.5-Release is now available. ;-) Cheers, -Matt - - - - - - - - - - - - - - - - -
Current thread:
- SYN flood messages flooding my mailbox Curtis Villamizar (Sep 16)
- Re: SYN flood messages flooding my mailbox Perry E. Metzger (Sep 16)
- Re: SYN flood messages flooding my mailbox Avi Freedman (Sep 16)
- Re: SYN flood messages flooding my mailbox Curtis Villamizar (Sep 17)
- Re: SYN flood messages flooding my mailbox Matt Bush (Sep 17)
- Re: SYN flood messages flooding my mailbox Jonathan M. Bresler (Sep 17)
- Re: SYN flood messages flooding my mailbox Jonathan M. Bresler (Sep 17)
- Re: SYN flood messages flooding my mailbox Curtis Villamizar (Sep 17)
- <Possible follow-ups>
- Re: SYN flood messages flooding my mailbox Vadim Antonov (Sep 16)
- Re: SYN flood messages flooding my mailbox alex (Sep 17)
- Re: SYN flood messages flooding my mailbox Curtis Villamizar (Sep 17)
- Re: SYN flood messages flooding my mailbox Paul Ferguson (Sep 18)
- Re: SYN flood messages flooding my mailbox Curtis Villamizar (Sep 18)
- Re: SYN flood messages flooding my mailbox Paul Ferguson (Sep 18)
- Re: SYN flood messages flooding my mailbox Vadim Antonov (Sep 19)
- Re: SYN flood messages flooding my mailbox Curtis Villamizar (Sep 23)