Date: Sun, 20 Apr 2008 20:23:28 +0200 From: Holger Kipp <hk@alogis.com> To: stable@freebsd.org Subject: [FOUND] connection reset after second syn-ack was sent (FreeBSD 7.0) Message-ID: <20080420182328.GA99572@intserv.int1.b.intern> In-Reply-To: <20080418131318.GA27272@intserv.int1.b.intern> References: <20080418131318.GA27272@intserv.int1.b.intern>
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On Fri, Apr 18, 2008 at 03:13:18PM +0200, Holger Kipp wrote:
> I have a little problem here that is driving me nuts:
Found it (must have been blind) - sorry for wasting the bandwidth...
> I occasionally experience the following:
> 2008-04-18 10:38:46.454495 IP 192.168.1.1.55784 > 192.168.188.188.515: S 2765551688:2765551688(0) win 32768 <mss 1460,wscale 0,nop>
> 2008-04-18 10:38:46.454507 IP 192.168.188.188.515 > 192.168.1.1.55784: S 3468383339:3468383339(0) ack 2765551689 win 65535 <mss 1460,nop,wscale 3>
> 2008-04-18 10:38:49.453868 IP 192.168.188.188.515 > 192.168.1.1.55784: S 3468383339:3468383339(0) ack 2765551689 win 65535 <mss 1460,nop,wscale 3>
> 2008-04-18 10:38:49.722767 IP 192.168.1.1.55784 > 192.168.188.188.515: . ack 1 win 32768
> 2008-04-18 10:38:49.722786 IP 192.168.188.188.515 > 192.168.1.1.55784: R 3468383340:3468383340(0) win 0
> 2008-04-18 10:38:49.727926 IP 192.168.1.1.55784 > 192.168.188.188.515: P 1:7(6) ack 1 win 32768
> 2008-04-18 10:38:49.819709 IP 192.168.188.188.515 > 192.168.1.1.55784: P 1:2(1) ack 7 win 65535
> 2008-04-18 10:38:50.006543 IP 192.168.1.1.55784 > 192.168.188.188.515: R 2765551695:2765551695(0) win 0
dhcp-383-1# tcpdump -n -l -tttt -vvv -S -r 20080417_tcpdump_ru_all_515.dump port 53479
reading from file 20080417_tcpdump_ru_all_515.dump, link-type EN10MB (Ethernet)
2008-04-19 16:38:28.149039 IP (tos 0x0, ttl 53, id 64087, offset 0, flags [DF], proto TCP (6), length 48) 192.168.1.1.53479 > 192.168.188.188.515: S, cksum 0x7a8f (correct), 2316685919:2316685919(0) win 32768 <mss 1460,wscale 0,nop>
2008-04-19 16:38:28.149091 IP (tos 0x0, ttl 64, id 14400, offset 0, flags [DF], proto TCP (6), length 48) 192.168.188.188.515 > 192.168.1.1.53479: S, cksum 0xded3 (correct), 1506132195:1506132195(0) ack 2316685920 win 65535 <mss 1460,nop,wscale 3>
2008-04-19 16:38:31.148742 IP (tos 0x0, ttl 64, id 14401, offset 0, flags [DF], proto TCP (6), length 48) 192.168.188.188.515 > 192.168.1.1.53479: S, cksum 0xded3 (correct), 1506132195:1506132195(0) ack 2316685920 win 65535 <mss 1460,nop,wscale 3>
2008-04-19 16:38:31.332618 IP (tos 0x0, ttl 53, id 64089, offset 0, flags [DF], proto TCP (6), length 40) 192.168.1.1.53479 > 192.168.188.188.515: ., cksum 0x8a94 (correct), 2316685926:2316685926(0) ack 1506132196 win 32768
2008-04-19 16:38:31.332634 IP (tos 0x0, ttl 64, id 14402, offset 0, flags [DF], proto TCP (6), length 40) 192.168.188.188.515 > 192.168.1.1.53479: R, cksum 0x671d (correct), 1506132196:1506132196(0) win 0
2008-04-19 16:38:31.395882 IP (tos 0x0, ttl 53, id 64090, offset 0, flags [DF], proto TCP (6), length 46) 192.168.1.1.53479 > 192.168.188.188.515: P, cksum 0xdedb (correct), 2316685920:2316685926(6) ack 1506132196 win 32768
2008-04-19 16:38:31.468651 IP (tos 0x0, ttl 64, id 14417, offset 0, flags [DF], proto TCP (6), length 41) 192.168.188.188.515 > 192.168.1.1.53479: P, cksum 0x0a8c (correct), 1506132196:1506132197(1) ack 2316685926 win 65535
2008-04-19 16:38:31.652240 IP (tos 0x0, ttl 53, id 64091, offset 0, flags [DF], proto TCP (6), length 40) 192.168.1.1.53479 > 192.168.188.188.515: R, cksum 0x254b (correct), 2316685926:2316685926(0) win 0
OK, so this is what happenes:
ID 64087 receive SYN 19:19
-------- send SYN-ACK 95:95 for 20
-------- send SYN-ACK 95.95 for 20 again after three seconds
ID 64089 receive ACK 26:26 for 96 (interesting, not 20:26)
-------- send RST because ACK is not 20:xx, I assume
ID 64090 receive ACK 20:26 for 96
but shouldn't the ID be in sequence?
-------- send ACK 96:97 for 26
as we got the correct ACK now.
ID 64091 receive RST 26:26
Well, still open questions here. Sight.
Suggestions welcome. Ah, the initiating system is HP-UX...
Anyway, thanks for listening.
Best regards,
Holger Kipp
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