Re: ipv4 connection problems
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On Sat, Mar 05, 2005 at 10:16:06PM -0700, Peter Avalos wrote:
> On Sat, Mar 05, 2005 at 06:37:48PM -0800, Matthew Dillon wrote:
> >=20
> > :Over the past few weeks I've been having a problem with Apache not
> > :responding to port it's listening on. After some investigation, I
> > :was able to determine that it was only happening on ipv4. IPv6 was
> > :working just fine. If I restarted the server, everything would be fine
> > :for about an hour or so (depending on traffic), and then it would
> > :start up again. I figured this was an Apache problem, since it was
> > :only happening with my web server.
> > :
> > :Today, I was stressing out my ftp server (the vanilla base version),
> > :and I saw that it was doing the same thing my web server was doing:
> > :
> > :box:~% telnet -4 theshell.com 21
> > :Trying 209.200.146.2...
> > :telnet: connect to address 209.200.146.2: Operation timed out
> > :telnet: Unable to connect to remote host
> > :
> > :And without doing anything...
> > :
> > :box:~% telnet -4 theshell.com 21
> > :Trying 209.200.146.2...
> > :Connected to theshell.com.
> > :Escape character is '^]'.
> > :220 box.theshell.com FTP server (Version 6.00LS) ready.
> > :quit
> > :221 Goodbye.
> > :Connection closed by foreign host.
> > :
> > :Note: This is not a network connectivity issue since those telnets
> > :are on the same box (box is 209.200.146.2).
> > :
> > :Again, ipv6 seems to work just fine. Other than this, I don't really
> > :know what other information I can provide that can help in finding
> > :where the problem is. Any thoughts?
> > :
> > :Peter
> >=20
> > You need to do a bit more investigation. Use tcpdump on the server
> > to see if the machine is even *receiving* the connection attempt th=
at
> > is timing out on you, and check that your Apache has not hit its=20
> > programmed simultanious connection limit, controlled by its config
> > file (there's an apachectl command that will do that).
> >=20
>=20
> In the above test I was connecting to the ftp port on the machine. I'm
> confident this has nothing to do with Apache now. I'll have to see
> about running tcpdump and see what's going on. I was assuming that since
> I was running telnet directly from the box that the server is running,
> it's not a network connectivity problem. I have a feeling that the socket
> is not getting the connection attempts for some reason. I'm curious if
> anyone else is seeing this behavior.
>=20
> Peter
Here's a tcpdump output of a 'telnet 0 80':
07:21:41.872244 IP (tos 0x10, ttl 64, id 43935, offset 0, flags [none], le=
ngth: 64) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,wscale 0,nop,nop,sackOK,nop,nop,time=
stamp 251468000 0>
07:21:44.868076 IP (tos 0x10, ttl 64, id 45093, offset 0, flags [none], le=
ngth: 64) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,wscale 0,nop,nop,sackOK,nop,nop,time=
stamp 251468300 0>
07:21:48.068122 IP (tos 0x10, ttl 64, id 46299, offset 0, flags [none], le=
ngth: 64) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,wscale 0,nop,nop,sackOK,nop,nop,time=
stamp 251468620 0>
07:21:51.268172 IP (tos 0x10, ttl 64, id 47481, offset 0, flags [none], le=
ngth: 48) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,nop,sackOK>
07:21:54.468226 IP (tos 0x10, ttl 64, id 48667, offset 0, flags [none], le=
ngth: 48) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,nop,sackOK>
07:21:57.668273 IP (tos 0x10, ttl 64, id 49811, offset 0, flags [none], le=
ngth: 48) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,nop,sackOK>
07:22:03.868365 IP (tos 0x10, ttl 64, id 52138, offset 0, flags [none], le=
ngth: 48) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,nop,sackOK>
07:22:16.068553 IP (tos 0x10, ttl 64, id 56963, offset 0, flags [none], le=
ngth: 48) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,nop,sackOK>
07:22:40.268914 IP (tos 0x10, ttl 64, id 64387, offset 0, flags [none], le=
ngth: 48) 209.200.146.2.3828 > 209.200.146.2.80: S [tcp sum ok] 4209775517:=
4209775517(0) win 57344 <mss 16344,nop,nop,sackOK>
Hopefully that means something.
sockstat | grep httpd:
www httpd 91658 3 tcp4 209.200.146.2:80 *:*
www httpd 91658 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91640 3 tcp4 209.200.146.2:80 *:*
www httpd 91640 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91563 3 tcp4 209.200.146.2:80 *:*
www httpd 91563 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91477 3 tcp4 209.200.146.2:80 *:*
www httpd 91477 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91477 47 tcp4 209.200.146.2:80 67.173.210.133:15=
04
www httpd 91474 3 tcp4 209.200.146.2:80 *:*
www httpd 91474 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91398 3 tcp4 209.200.146.2:80 *:*
www httpd 91398 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91388 3 tcp4 209.200.146.2:80 *:*
www httpd 91388 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91370 3 tcp4 209.200.146.2:80 *:*
www httpd 91370 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91370 47 tcp4 209.200.146.2:80 65.247.90.59:35332
www httpd 91369 3 tcp4 209.200.146.2:80 *:*
www httpd 91369 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91365 3 tcp4 209.200.146.2:80 *:*
www httpd 91365 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91126 3 tcp4 209.200.146.2:80 *:*
www httpd 91126 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 91126 47 tcp4 209.200.146.2:80 202.134.244.220:3=
589
www httpd 91116 3 tcp4 209.200.146.2:80 *:*
www httpd 91116 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 90808 3 tcp4 209.200.146.2:80 *:*
www httpd 90808 4 tcp6 2001:4830:2130::1:80 *:*
www httpd 90808 47 tcp4 209.200.146.2:80 212.117.224.50:31=
728
root httpd 43531 3 tcp4 209.200.146.2:80 *:*
root httpd 43531 4 tcp6 2001:4830:2130::1:80 *:*
And immediately after the first telnet that failed:
07:27:26.690268 IP (tos 0x10, ttl 64, id 39344, offset 0, flags [none], le=
ngth: 64) 209.200.146.2.3837 > 209.200.146.2.80: S [tcp sum ok] 3035751191:=
3035751191(0) win 57344 <mss 16344,nop,wscale 0,nop,nop,sackOK,nop,nop,time=
stamp 251502468 0>
07:27:26.690313 IP (tos 0x0, ttl 64, id 39345, offset 0, flags [none], len=
gth: 64) 209.200.146.2.80 > 209.200.146.2.3837: S [tcp sum ok] 3527180342:3=
527180342(0) ack 3035751192 win 57344 <mss 16344,nop,wscale 0,nop,nop,times=
tamp 251502468 251502468,nop,nop,sackOK>
07:27:26.690340 IP (tos 0x10, ttl 64, id 39346, offset 0, flags [none], le=
ngth: 52) 209.200.146.2.3837 > 209.200.146.2.80: . [tcp sum ok] 1:1(0) ack =
1 win 57344 <nop,nop,timestamp 251502468 251502468>
07:27:28.526883 IP (tos 0x10, ttl 64, id 40180, offset 0, flags [none], le=
ngth: 58) 209.200.146.2.3837 > 209.200.146.2.80: P [tcp sum ok] 1:7(6) ack =
1 win 57344 <nop,nop,timestamp 251502652 251502468>
07:27:28.527404 IP (tos 0x0, ttl 64, id 40181, offset 0, flags [none], len=
gth: 268) 209.200.146.2.80 > 209.200.146.2.3837: P 1:217(216) ack 7 win 573=
44 <nop,nop,timestamp 251502652 251502652>
07:27:28.527531 IP (tos 0x0, ttl 64, id 40182, offset 0, flags [none], len=
gth: 52) 209.200.146.2.80 > 209.200.146.2.3837: F [tcp sum ok] 217:217(0) a=
ck 7 win 57344 <nop,nop,timestamp 251502652 251502652>
07:27:28.527539 IP (tos 0x10, ttl 64, id 40183, offset 0, flags [none], le=
ngth: 52) 209.200.146.2.3837 > 209.200.146.2.80: . [tcp sum ok] 7:7(0) ack =
218 win 57344 <nop,nop,timestamp 251502652 251502652>
07:27:28.527711 IP (tos 0x10, ttl 64, id 40184, offset 0, flags [none], le=
ngth: 52) 209.200.146.2.3837 > 209.200.146.2.80: F [tcp sum ok] 7:7(0) ack =
218 win 57344 <nop,nop,timestamp 251502652 251502652>
07:27:28.527721 IP (tos 0x0, ttl 64, id 40185, offset 0, flags [none], len=
gth: 52) 209.200.146.2.80 > 209.200.146.2.3837: . [tcp sum ok] 218:218(0) a=
ck 8 win 57344 <nop,nop,timestamp 251502652 251502652>
Obviously that one went through.
Any ideas?
Peter
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