Il 23/04/2014 16.07, Tom Eastep ha scritto:
> On 4/23/2014 5:53 AM, Erica Liverani wrote:
>> Hello,
>>     I am using Shorewall 4.5.6 to access a customer's service via leased
>> line. Our network (172.24.80/22) is masquerated as 192.168.54.197 to
>> customer service (194.169.8.222).
>>     My application (running on laptop (172.24.82.84) different from
>> Shorewall system) connects to the service with SO_KEEPALIVE flag, sends
>> the probe every 15 seconds but gets no answer.
>>
>>     Tcpdump on Shorewall system, our side, shows these packets:
>>
>> 13:21:20.055444 IP 172.24.82.84.51160 > 194.169.8.222.53640: Flags [.],
>> seq 4134671944:4134671945, ack 3708838363, win 3999, length 1
>>          0x0000:  001e 58e0 2f18 60eb 6907 d154 0800 4500  ..X./.`.i..T..E.
>>          0x0010:  0029 6dfe 4000 8006 c2dc ac18 5254 c2a9  .)[email protected]..
>>          0x0020:  08de c7d8 d188 f672 1648 dd10 61db 5010  .......r.H..a.P.
>>          0x0030:  0f9f f137 0000 0000 0000 0000            ...7........
>> 13:21:34.950024 IP 172.24.82.84.51158 > 194.169.8.222.53610: Flags [.],
>> seq 0:1, ack 1, win 3999, length 1
>>          0x0000:  001e 58e0 2f18 60eb 6907 d154 0800 4500  ..X./.`.i..T..E.
>>          0x0010:  0029 008a 4000 8006 3051 ac18 5254 c2a9  .)[email protected]..
>>          0x0020:  08de c7d6 d16a a04e 3fc9 4c8d 73d5 5010  .....j.N?.L.s.P.
>>          0x0030:  0f9f 9c84 0000 0000 0000 0000            ............
>> 13:21:35.056108 IP 172.24.82.84.51160 > 194.169.8.222.53640: Flags [.],
>> seq 0:1, ack 1, win 3999, length 1
>>          0x0000:  001e 58e0 2f18 60eb 6907 d154 0800 4500  ..X./.`.i..T..E.
>>          0x0010:  0029 00c4 4000 8006 3017 ac18 5254 c2a9  .)[email protected]..
>>          0x0020:  08de c7d8 d188 f672 1648 dd10 61db 5010  .......r.H..a.P.
>>          0x0030:  0f9f f137 0000 0000 0000 0000            ...7........
>>
>>     On customer's side, I see also the ACKs:
>>
>> 13:21:20.055462 IP 192.168.54.197.51160 > 194.169.8.222.53640: Flags
>> [.], seq 19:20, ack 25, win 3999, length 1
>>          0x0000:  0019 e2eb 2ec6 001e 58e0 2f1b 0800 4500  ........X./...E.
>>          0x0010:  0029 6dfe 4000 7f06 cadb c0a8 36c5 c2a9  .)[email protected]...
>>          0x0020:  08de c7d8 d188 f672 1648 dd10 61db 5010  .......r.H..a.P.
>>          0x0030:  0f9f f836 0000 00                        ...6...
>> 13:21:20.076780 IP 194.169.8.222.53640 > 192.168.54.197.51160: Flags
>> [.], ack 20, win 46, options [nop,nop,sack 1 {1041772106:1041772107}],
>> length 0
>>          0x0000:  001e 58e0 2f1b 0019 e2eb 2ec6 0800 4500  ..X./.........E.
>>          0x0010:  0034 d37b 4000 3706 ad53 c2a9 08de c0a8  .4.{@.7..S......
>>          0x0020:  36c5 d188 c7d8 dd10 61db f672 1649 8010  6.......a..r.I..
>>          0x0030:  002e df7c 0000 0101 050a 348a 447f 348a  ...|......4.D.4.
>>          0x0040:  4480                                     D.
>> 13:21:34.950041 IP 192.168.54.197.51158 > 194.169.8.222.53610: Flags
>> [.], seq 19:20, ack 25, win 3999, length 1
>>          0x0000:  0019 e2eb 2ec6 001e 58e0 2f1b 0800 4500  ........X./...E.
>>          0x0010:  0029 008a 4000 7f06 3850 c0a8 36c5 c2a9  .)[email protected]...
>>          0x0020:  08de c7d6 d16a a04e 3fc9 4c8d 73d5 5010  .....j.N?.L.s.P.
>>          0x0030:  0f9f a383 0000 00                        .......
>> 13:21:34.971211 IP 194.169.8.222.53610 > 192.168.54.197.51158: Flags
>> [.], ack 20, win 46, options [nop,nop,sack 1 {1998813038:1998813039}],
>> length 0
>>          0x0000:  001e 58e0 2f1b 0019 e2eb 2ec6 0800 4500  ..X./.........E.
>>          0x0010:  0034 a69f 4000 3706 da2f c2a9 08de c0a8  [email protected]../......
>>          0x0020:  36c5 d16a c7d6 4c8d 73d5 a04e 3fca 8010  6..j..L.s..N?...
>>          0x0030:  002e dfb0 0000 0101 050a 1771 b724 1771  ...........q.$.q
>>          0x0040:  b725                                     .%
>> 13:21:35.056124 IP 192.168.54.197.51160 > 194.169.8.222.53640: Flags
>> [.], seq 19:20, ack 25, win 3999, length 1
>>          0x0000:  0019 e2eb 2ec6 001e 58e0 2f1b 0800 4500  ........X./...E.
>>          0x0010:  0029 00c4 4000 7f06 3816 c0a8 36c5 c2a9  .)[email protected]...
>>          0x0020:  08de c7d8 d188 f672 1648 dd10 61db 5010  .......r.H..a.P.
>>          0x0030:  0f9f f836 0000 00                        ...6...
>> 13:21:35.078037 IP 194.169.8.222.53640 > 192.168.54.197.51160: Flags
>> [.], ack 20, win 46, options [nop,nop,sack 1 {1041772106:1041772107}],
>> length 0
>>          0x0000:  001e 58e0 2f1b 0019 e2eb 2ec6 0800 4500  ..X./.........E.
>>          0x0010:  0034 d37c 4000 3706 ad52 c2a9 08de c0a8  .4.|@.7..R......
>>          0x0020:  36c5 d188 c7d8 dd10 61db f672 1649 8010  6.......a..r.I..
>>          0x0030:  002e df7c 0000 0101 050a 348a 447f 348a  ...|......4.D.4.
>>          0x0040:  4480                                     D.
>>
>> Someone can help me to pinpoint the problem ?
>>
>
> If 'echo 1 > /proc/sys/net/netfilter/nf_conntrack_tcp_be_liberal'
> corrects the problem, then you can adjust your /etc/sysctl.conf to
> enforce that setting. Otherwise, we'll need to see the output of
> 'shorewall dump' collected as described at
> http://www.shorewall.org/support.htm#Guidelines.
>
> Thanks,
> -Tom

Thank you Tom: your first indication corrects the problem.
-Erica

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