nanog mailing list archives
Re: SYN flood messages flooding my mailbox
From: "Jonathan M. Bresler" <jmb () freefall freebsd org>
Date: Tue, 17 Sep 1996 11:32:47 -0700 (PDT)
Curtis Villamizar wrote:
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.
The SYN_RCVD bug has been fixed in FreeBSD source. i should know, i wrote the patch. as a result, the attacker has to sink the machine in less than 75 seconds, else it begins to free resources. before the patch the attacker had ~11 minutes to do the deed. (would have been 2 hours but for retransmission of the SYN-ACK packet by the target) the bug is dicsussed in detail on page 191 of tcp/ip illustrated by rick stevens. we have not yet moved to a hask table. soon. our SO_MAXCONN is 128, rather than the common 5. jmb -- Jonathan M. Bresler FreeBSD Postmaster jmb () FreeBSD ORG FreeBSD--4.4BSD Unix for PC clones, source included. http://www.freebsd.org/ PGP 2.6.2 Fingerprint: 31 57 41 56 06 C1 40 13 C5 1C E3 E5 DC 62 0E FB
Curtis ps- (My 6 year old has a FreeBSD system, but its 2.0.5. Got to get him to upgrade. :)
darn tooting! ;) - - - - - - - - - - - - - - - - -
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)
- Re: SYN flood messages flooding my mailbox Vadim Antonov (Sep 23)