Messages in this thread | | | Date | Fri, 12 Jan 2001 00:04:57 +0000 (GMT) | From | Mark Longair <> | Subject | [2.2.18] outgoing connections getting stuck in SYN_SENT |
| |
I'm having a problem where twice a day or so, any new tcp connection it gets stuck in SYN_SENT. Eventually this situation rights itself, but obviously in the meantime many services (e.g. squid, X) are broken. The machine does IP masquerdading with ipchains, and masqueraded connections through it seem to be unaffected. The kernel version is 2.2.18, although the same happened with 2.2.17.
I can't work out what's causing this to happen, or how to fix it when it occurs, short of rebooting. (Killing off daemons, lowering and raising the network interfaces, etc. have no effect on the problem.) It is still possible to connect to the computer (e.g. with ssh) while the problem is happening. I'm logging all packets that are rejected by the ipchains setup, but no rejected packets appear in the logs when you attempt an outgoing connection.
I've included a tcpdump of an attempt to `wget http://www.yahoo.com/' while the problem is occuring. (This is a dump of the external network interface, an EtherExpress Pro100.) AIUI, the first two lines are as you would expect, but then it tells the server that the external interface is unreachable. I'm not sure what this means; that address can still be pinged from everywhere.
I've searched around for similar problems on this list, the web and dejanews, but I haven't found anything that has helped. I'd be very grateful for any suggestions - my apologies if I've missed something obvious.
cheers mark
This output is from `tcpdump -i eth0 -vvv | grep yahoo' just before `wget http://www.yahoo.com/':
18:38:15.361774 starfruit.iw3d.co.uk.2327 > www9.dcx.yahoo.com.www: S 2996758185:2996758185(0) win 32120 <mss 1460,sackOK,timestamp 1360740[|tcp]> (DF) (ttl 64, id 14541) 18:38:15.465524 www9.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2327: S 3898083689:3898083689(0) ack 2996758186 win 17520 <mss 1460> (DF) [tos 0x60] (ttl 44, id 51680) 18:38:15.472910 starfruit.iw3d.co.uk > www9.dcx.yahoo.com: icmp: host starfruit.iw3d.co.uk unreachable [tos 0xc0] (ttl 255, id 14557) 18:38:15.472943 starfruit.iw3d.co.uk > www3.dcx.yahoo.com: icmp: host starfruit.iw3d.co.uk unreachable [tos 0xc0] (ttl 255, id 14558) 18:38:18.352908 starfruit.iw3d.co.uk.2327 > www9.dcx.yahoo.com.www: S 2996758185:2996758185(0) win 32120 <mss 1460,sackOK,timestamp 1361040[|tcp]> (DF) (ttl 64, id 14564) 18:38:18.456461 www9.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2327: . ack 1 win 17520 (DF) [tos 0x60] (ttl 44, id 57794) 18:38:18.463769 www9.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2327: S 3898083689:3898083689(0) ack 2996758186 win 17520 <mss 1460> (DF) [tos 0x60] (ttl 44, id 57809) 18:38:20.602904 starfruit.iw3d.co.uk.2325 > www3.dcx.yahoo.com.www: S 2983862334:2983862334(0) win 32120 <mss 1460,sackOK,timestamp 1361265[|tcp]> (DF) (ttl 64, id 14569) 18:38:20.729037 www3.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2325: . ack 2983862335 win 17520 (DF) [tos 0x60] (ttl 44, id 49883) 18:38:21.145902 www3.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2325: S 992130302:992130302(0) ack 2983862335 win 17520 <mss 1460> (DF) [tos 0x60] (ttl 44, id 50913) 18:38:21.452904 starfruit.iw3d.co.uk > www3.dcx.yahoo.com: icmp: host starfruit.iw3d.co.uk unreachable [tos 0xc0] (ttl 255, id 14570) 18:38:21.452920 starfruit.iw3d.co.uk > www3.dcx.yahoo.com: icmp: host starfruit.iw3d.co.uk unreachable [tos 0xc0] (ttl 255, id 14571) 18:38:24.352902 starfruit.iw3d.co.uk.2327 > www9.dcx.yahoo.com.www: S 2996758185:2996758185(0) win 32120 <mss 1460,sackOK,timestamp 1361640[|tcp]> (DF) (ttl 64, id 14573) 18:38:24.457700 www9.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2327: . ack 1 win 17520 (DF) [tos 0x60] (ttl 44, id 4335) 18:38:24.468653 www9.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2327: S 3898083689:3898083689(0) ack 2996758186 win 17520 <mss 1460> (DF) [tos 0x60] (ttl 44, id 4354) 18:38:24.727569 www3.dcx.yahoo.com.www > starfruit.iw3d.co.uk.2326: S 1025447007:1025447007(0) ack 2988099611 win 17520 <mss 1460> (DF) [tos 0x60] (ttl 44, id 59842) 18:38:25.092905 starfruit.iw3d.co.uk > www3.dcx.yahoo.com: icmp: host starfruit.iw3d.co.uk unreachable [tos 0xc0] (ttl 255, id 14574) 18:38:25.092924 starfruit.iw3d.co.uk > www9.dcx.yahoo.com: icmp: host starfruit.iw3d.co.uk unreachable [tos 0xc0] (ttl 255, id 14575)
This is the start of the output of `netstat -ape' from another occasion when the problem occurred - I've snipped most of the (very similar) output; any new outgoing connections get into the same SYN_SENT, one byte in Send-Q state that the fetchmail daemons at the top are in.
Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State User Inode PID/Program name tcp 0 1 starfruit.iw3d.co.:2391 mango.iw3d.co.uk:pop3 SYN_SENT mark 11996 828/fetchmail tcp 0 1 starfruit.iw3d.co.:2387 eidosnet.co.uk:pop3 SYN_SENT mjs 11739 493/fetchmail tcp 0 1 starfruit.iw3d.co.:2384 mango.iw3d.co.uk:pop3 SYN_SENT mjs 11594 493/fetchmail tcp 0 1 starfruit.iw3d.co.:2383 mango.iw3d.co.uk:pop3 SYN_SENT mark 11590 828/fetchmail tcp 0 1 starfruit.iw3d.co.:2382 *:* CLOSE mjs 11561 493/fetchmail tcp 0 1 starfruit.iw3d.co.:2381 *:* CLOSE mark 11533 828/fetchmail tcp 0 1 starfruit.iw3d.co.:2380 *:* CLOSE root 11528 279/stunnel tcp 0 0 starfruit.iw3d.co.u:ssh modem-246.elros.di:3841 ESTABLISHED root 11493 2123/sshd tcp 0 1 starfruit.iw3d.co.:2378 *:* CLOSE mark 11457 828/fetchmail tcp 0 1 starfruit.iw3d.co.:2377 *:* CLOSE mjs 11420 493/fetchmail tcp 0 1 starfruit.iw3d.co.:2376 *:* CLOSE mark 11411 828/fetchmail tcp 0 1 starfruit.iw3d.co.:2372 *:* CLOSE mjs 11374 493/fetchmail tcp 0 1 starfruit.iw3d.co.:2359 *:* CLOSE mjs 10866 493/fetchmail [...] - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
| |