Date: Wed, 21 Mar 2012 17:20:32 -0700 From: Chuck Swiger <cswiger@mac.com> To: =?iso-8859-1?Q?Seyit_=D6zg=FCr?= <seyit.ozgur@istanbul.net> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Malformed syn packet cause %100 cpu and interrupts FreeBSD 9.0 release Message-ID: <2805EAC2-BC15-4BC8-B85B-0908FCF255C5@mac.com> In-Reply-To: <3807CE6F3BF4B04EB897F4EBF2D258CE5C064A80@yuhanna.magnetdigital.local> References: <3807CE6F3BF4B04EB897F4EBF2D258CE5C05F221@yuhanna.magnetdigital.local> <38FA7BAB-AC2B-4515-85CF-27F77C3F4313@mac.com> <3807CE6F3BF4B04EB897F4EBF2D258CE5C064A80@yuhanna.magnetdigital.local>
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On Mar 21, 2012, at 7:15 AM, Seyit =D6zg=FCr wrote: > Hello chris, I'm Chuck, but no matter. > Here i get tcpdump with X param..=20 >=20 > First look input errors.. its about 60 mbit/sec and much more packets = can't > process >=20 > packets errs idrops bytes packets errs bytes colls > 36356 42777 0 7747642 243 0 263462 0 > 36732 41709 0 7681242 240 0 359432 0 [ ... ] 60 mbit/s of SYNs is a pretty significant DoS attack. You should be = involving your ISP to filter the source IPs before they hit your pipe, = and probably pull in the police and/or national CERT organization. > Then tcpdump with X param, also i attach txt file in mail.. >=20 > 16:02:53.954863 IP 88.133.15.78 > x.x.x.x: tcp > 0x0000: 4500 0050 10ba 07d0 6b06 7382 5885 0f4e = E..P....k.s.X..N > 0x0010: 556f 065a f386 0050 45c4 8c77 9592 0241 = Uo.Z...PE..w...A > 0x0020: 00a3 3c4c b5a3 0000 8807 a83a f215 b40d = ..<L.......:.... > 0x0030: 0006 acb5 0038 8f76 afd7 3d00 0000 0000 = .....8.v..=3D..... > 0x0040: 0000 0000 0000 0000 0000 0000 0000 0000 = ................ =46rom inspection, that looks to be a normal TCP over IPv4 SYN packet = from client port 62342 to your port 80...I didn't validate the = checksums, though. (No real point in obscuring the destination IP = address, as it's in the packets you're showing.) Regards, --=20 -Chuck
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