Date: Mon, 13 Feb 2006 23:07:38 -0500 From: Jerry Bell <jbell@stelesys.com> To: Jerry Bell <jbell@stelesys.com> Cc: freebsd-questions@freebsd.org Subject: Re: Help with strange web server problem Message-ID: <43F1578A.8060803@stelesys.com> In-Reply-To: <43F13D9F.5040606@stelesys.com> References: <1716.209.134.164.18.1139835495.squirrel@www.stelesys.com> <9CB4E9E3-EE93-4E65-AD74-0ACC9B3C64FF@mac.com> <4026.209.134.164.18.1139861525.squirrel@www.stelesys.com> <1DFDCA44-74AC-475A-96A9-0E3AD5B492C4@mac.com> <43F13D9F.5040606@stelesys.com>
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Looks like it's still an issue, so I'd say the firewall issue is still
in play. If there is not a firewall/proxy in place, are there any known
issues with IPFW (or anything else with FBSD) that could cause this
behavior?
Jerry Bell wrote:
> Charles - thank you for your excellent investigation! I'm pretty sure
> that my colo provider isn't running a firewall (I've asked them not
> to, anyhow). I am running IPFW on that box, with the standard "allow
> tcp from any to any established" followed by the "allow tcp any to
> my_ip 80 setup". I've done that on other servers without it being a
> problem like this. I'm going to have the colo double check for router
> acl's or something like that in the morning.
>
> Since this is such an intermittent problem, I can't yet say that it's
> fixed, but I ran with the "disks being idled" theory and wrote a small
> script that creates a file and deletes a file every minute, and since
> that's been running, I've not seeing the issue repeat - but then this
> is not a very repeatable problem.
>
> Thanks again for your great assistance.
>
> Jerry
>
>
> Charles Swiger wrote:
>> On Feb 13, 2006, at 3:12 PM, Jerry Bell wrote:
>>> I didn't want to spam the link out, but it's www.musiclodge.com. I
>>> will
>>> gather the capture data from working and non working sessions and
>>> send it
>>> out.
>>
>> Well, I can confirm the behavior you've described.
>>
>> It looks somewhat like a stateful firewall or is in the way and is
>> generating an RST, even while your webserver tries to generate a
>> response. However, once the firewall sees the outbound traffic, it
>> seems to create a dynamic rule which lets the traffic from subsequent
>> connections through:
>>
>> 5-pan# tcpdump -tnXs 0 host www.musiclodge.com
>> tcpdump: verbose output suppressed, use -v or -vv for full protocol
>> decode
>> listening on en0, link-type EN10MB (Ethernet), capture size 65535 bytes
>> IP 199.103.21.238.50740 > 63.175.100.44.80: S
>> 2282569549:2282569549(0) win 65535 <mss 1460,nop,wscale
>> 0,nop,nop,timestamp 1159441862 0>
>> 0x0000: 4510 003c 4653 4000 4006 7328 c767 15ee
>> E..<FS@.@.s(.g..
>> 0x0010: 3faf 642c c634 0050 880d 3f4d 0000 0000
>> ?.d,.4.P..?M....
>> 0x0020: a002 ffff 815f 0000 0204 05b4 0103 0300
>> ....._..........
>> 0x0030: 0101 080a 451b adc6 0000 0000 ....E.......
>> IP 63.175.100.44.80 > 199.103.21.238.50740: S
>> 2634350592:2634350592(0) ack 2282569550 win 65535
>> 0x0000: 4500 0028 0000 4000 2506 d49f 3faf 642c
>> E..(..@.%...?.d,
>> 0x0010: c767 15ee 0050 c634 9d05 0000 880d 3f4e
>> .g...P.4......?N
>> 0x0020: 5012 ffff 03bc 0000 0000 0000 0000 1b60
>> P..............`
>> 0x0030: 2678 &x
>> IP 199.103.21.238.50740 > 63.175.100.44.80: . ack 1 win 65535
>> 0x0000: 4510 0028 4655 4000 4006 733a c767 15ee
>> E..(FU@.@.s:.g..
>> 0x0010: 3faf 642c c634 0050 880d 3f4e 9d05 0001
>> ?.d,.4.P..?N....
>> 0x0020: 5010 ffff 03bd 0000 P.......
>>
>> 3-way handshake is completed here, next traffic should be from my
>> machine making the "GET /", request, but instead your machine sends
>> another ACK:
>>
>> IP 63.175.100.44.80 > 199.103.21.238.50740: S
>> 2238145710:2238145710(0) ack 2282569550 win 65535 <mss
>> 1460,nop,wscale 1,nop,nop,timestamp 1453026167 1159441862>
>> 0x0000: 4500 003c 57fa 4000 3206 6f91 3faf 642c
>> E..<W.@.2.o.?.d,
>> 0x0010: c767 15ee 0050 c634 8567 64ae 880d 3f4e
>> .g...P.4.gd...?N
>> 0x0020: a012 ffff 9cdb 0000 0204 05b4 0103 0301
>> ................
>> 0x0030: 0101 080a 569b 6b77 451b adc6 9345 1153
>> ....V.kwE....E.S
>>
>> Interesting that the previous ack had no TCP options set, whereas
>> this one does include a timestamp in response.
>>
>> IP 199.103.21.238.50740 > 63.175.100.44.80: . ack 396204883 win 65535
>> <nop,nop,timestamp 1159441863 1453026167>
>> 0x0000: 4510 0034 4656 4000 4006 732d c767 15ee
>> E..4FV@.@.s-.g..
>> 0x0010: 3faf 642c c634 0050 880d 3f4e 9d05 0001
>> ?.d,.4.P..?N....
>> 0x0020: 8010 ffff 8157 0000 0101 080a 451b adc7
>> .....W......E...
>> 0x0030: 569b 6b77 V.kw
>>
>> Where did sequence # 396204883 come from? And your side follows up
>> with a pair of connection resets, and a normal ACK packet, too.
>>
>> IP 63.175.100.44.80 > 199.103.21.238.50740: R
>> 2634350593:2634350593(0) win 0
>> 0x0000: 4500 0028 b6f6 4000 3206 10a9 3faf 642c
>> E..(..@.2...?.d,
>> 0x0010: c767 15ee 0050 c634 9d05 0001 0000 0000
>> .g...P.4........
>> 0x0020: 5004 0000 cb24 0000 0000 0000 0000 f3fa
>> P....$..........
>> 0x0030: 5489 T.
>> IP 63.175.100.44.80 > 199.103.21.238.50740: R
>> 2634350593:2634350593(0) win 0
>> 0x0000: 4500 0028 4bfc 4000 3206 7ba3 3faf 642c
>> E..(K.@.2.{.?.d,
>> 0x0010: c767 15ee 0050 c634 9d05 0001 0000 0000
>> .g...P.4........
>> 0x0020: 5004 0000 cb24 0000 0000 0000 0000 abb8
>> P....$..........
>> 0x0030: c9be ..
>> IP 63.175.100.44.80 > 199.103.21.238.50740: S
>> 2238145710:2238145710(0) ack 2282569550 win 65535 <mss
>> 1460,nop,wscale 1,nop,nop,timestamp 1453026467 1159441862>
>> 0x0000: 4500 003c 3a9d 4000 3206 8cee 3faf 642c
>> E..<:.@.2...?.d,
>> 0x0010: c767 15ee 0050 c634 8567 64ae 880d 3f4e
>> .g...P.4.gd...?N
>> 0x0020: a012 ffff 9baf 0000 0204 05b4 0103 0301
>> ................
>> 0x0030: 0101 080a 569b 6ca3 451b adc6 bdd6 d7c9
>> ....V.l.E.......
>>
>> ...and my side closes, too. Something is badly confused.
>>
>> IP 199.103.21.238.50740 > 63.175.100.44.80: R
>> 2282569550:2282569550(0) win 0
>> 0x0000: 4500 0028 465a 4000 4006 7345 c767 15ee
>> E..(FZ@.@.sE.g..
>> 0x0010: 3faf 642c c634 0050 880d 3f4e 0000 0000
>> ?.d,.4.P..?N....
>> 0x0020: 5004 0000 a0cf 0000 P.......
>>
>> -------------------
>>
>> When I repeat the connection attempt a few seconds later:
>>
>> IP 199.103.21.238.50743 > 63.175.100.44.80: S 262625798:262625798(0)
>> win 65535 <mss 1460,nop,wscale 0,nop,nop,timestamp 1159442517 0>
>> 0x0000: 4510 003c 46c8 4000 4006 72b3 c767 15ee
>> E..<F.@.@.r..g..
>> 0x0010: 3faf 642c c637 0050 0fa7 5a06 0000 0000
>> ?.d,.7.P..Z.....
>> 0x0020: a002 ffff 815f 0000 0204 05b4 0103 0300
>> ....._..........
>> 0x0030: 0101 080a 451b b055 0000 0000 ....E..U....
>> IP 63.175.100.44.80 > 199.103.21.238.50743: S 362624500:362624500(0)
>> ack 262625799 win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp
>> 1453058903 1159442517>
>> 0x0000: 4500 003c e034 4000 3206 e756 3faf 642c
>> E..<.4@.2..V?.d,
>> 0x0010: c767 15ee 0050 c637 159d 35f4 0fa7 5a07
>> .g...P.7..5...Z.
>> 0x0020: a012 ffff 169b 0000 0204 05b4 0103 0301
>> ................
>> 0x0030: 0101 080a 569b eb57 451b b055 55d6 9ceb
>> ....V..WE..UU...
>> IP 199.103.21.238.50743 > 63.175.100.44.80: . ack 1 win 65535
>> <nop,nop,timestamp 1159442517 1453058903>
>> 0x0000: 4510 0034 46c9 4000 4006 72ba c767 15ee
>> E..4F.@.@.r..g..
>> 0x0010: 3faf 642c c637 0050 0fa7 5a07 159d 35f5
>> ?.d,.7.P..Z...5.
>> 0x0020: 8010 ffff 8157 0000 0101 080a 451b b055
>> .....W......E..U
>> 0x0030: 569b eb57 V..W
>>
>> 3-way handshake finishes OK, this time your initial ACK is OK and
>> includes a timestamp back.
>>
>> IP 199.103.21.238.50743 > 63.175.100.44.80: P 1:17(16) ack 1 win
>> 65535 <nop,nop,timestamp 1159442525 1453058903>
>> 0x0000: 4510 0044 46cd 4000 4006 72a6 c767 15ee
>> E..DF.@.@.r..g..
>> 0x0010: 3faf 642c c637 0050 0fa7 5a07 159d 35f5
>> ?.d,.7.P..Z...5.
>> 0x0020: 8018 ffff 8167 0000 0101 080a 451b b05d
>> .....g......E..]
>> 0x0030: 569b eb57 4745 5420 2f20 4854 5450 2f31
>> V..WGET./.HTTP/1
>> 0x0040: 2e30 0d0a .0..
>>
>> Here was my GET, which you then ACK....
>>
>> IP 63.175.100.44.80 > 199.103.21.238.50743: . ack 17 win 33304
>> <nop,nop,timestamp 1453059309 1159442525>
>> 0x0000: 4500 0034 052a 4000 3206 c269 3faf 642c
>> E..4.*@.2..i?.d,
>> 0x0010: c767 15ee 0050 c637 159d 35f5 0fa7 5a17
>> .g...P.7..5...Z.
>> 0x0020: 8010 8218 be99 0000 0101 080a 569b eced
>> ............V...
>> 0x0030: 451b b05d db4e 4827 E..].NH'
>> IP 199.103.21.238.50743 > 63.175.100.44.80: P 17:19(2) ack 1 win
>> 65535 <nop,nop,timestamp 1159442526 1453059309>
>> 0x0000: 4510 0036 46ce 4000 4006 72b3 c767 15ee
>> E..6F.@.@.r..g..
>> 0x0010: 3faf 642c c637 0050 0fa7 5a17 159d 35f5
>> ?.d,.7.P..Z...5.
>> 0x0020: 8018 ffff 8159 0000 0101 080a 451b b05e
>> .....Y......E..^
>> 0x0030: 569b eced 0d0a V.....
>>
>> ...followed by a correct data response.
>>
>> IP 63.175.100.44.80 > 199.103.21.238.50743: . 1:1449(1448) ack 19 win
>> 33304 <nop,nop,timestamp 1453059329 1159442526>
>> 0x0000: 4500 05dc c865 4000 3206 f985 3faf 642c
>> E....e@.2...?.d,
>> 0x0010: c767 15ee 0050 c637 159d 35f5 0fa7 5a19
>> .g...P.7..5...Z.
>> 0x0020: 8010 8218 2e5f 0000 0101 080a 569b ed01
>> ....._......V...
>> 0x0030: 451b b05e 4854 5450 2f31 2e31 2032 3030
>> E..^HTTP/1.1.200
>> 0x0040: 204f 4b0d 0a44 6174 653a 204d 6f6e 2c20
>> .OK..Date:.Mon,.
>> [ ... ]
>>
>> Check your firewall, or see whether your ISP or whoever has put a
>> HTTP reverse proxy in place which is breaking these connections.
>>
>> ---Chuck
>>
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