Strange TCP behaviour in STABLE

[hiren panchasara]

On 01/15/16 at 02:48P, Slawa Olhovchenkov wrote:
> 02:14:20.410159 IP 127.0.0.1.5423 > 127.0.0.1.80: Flags [S], seq 818919263, win 65535, options [mss 16344,nop,wscale 9,sackOK,TS val 749536482 ecr 0], length 0
> 02:14:20.410173 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [S.], seq 644693209, ack 818919264, win 65535, options [mss 16344,nop,wscale 9,sackOK,TS val 3209080170 ecr 749536482], length 0
> 02:14:20.410193 IP 127.0.0.1.5423 > 127.0.0.1.80: Flags [.], ack 1, win 159, options [nop,nop,TS val 749536482 ecr 3209080170], length 0
> 02:14:20.410212 IP 127.0.0.1.5423 > 127.0.0.1.80: Flags [P.], seq 1:417, ack 1, win 159, options [nop,nop,TS val 749536482 ecr 3209080170], length 416
> 02:14:20.410236 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [.], ack 417, win 158, options [nop,nop,TS val 3209080170 ecr 749536482], length 0
> 02:14:20.412066 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [P.], seq 1:557, ack 417, win 159, options [nop,nop,TS val 3209080172 ecr 749536482], length 556
> 02:14:20.412086 IP 127.0.0.1.5423 > 127.0.0.1.80: Flags [.], ack 557, win 158, options [nop,nop,TS val 749536484 ecr 3209080172], length 0
> 02:14:20.412163 IP 127.0.0.1.5423 > 127.0.0.1.80: Flags [F.], seq 417, ack 557, win 159, options [nop,nop,TS val 749536484 ecr 3209080172], length 0
> 02:14:20.412175 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [.], ack 418, win 159, options [nop,nop,TS val 3209080172 ecr 749536484], length 0
> 02:14:20.412241 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209080172 ecr 749536484], length 0
> 02:14:20.656139 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209080416 ecr 749536484], length 0
> 02:14:20.918187 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209080678 ecr 749536484], length 0
> 02:14:21.249783 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209081010 ecr 749536484], length 0
> 02:14:21.692560 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209081452 ecr 749536484], length 0
> 02:14:22.371972 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209082133 ecr 749536484], length 0
> 02:14:23.531776 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209083292 ecr 749536484], length 0
> 02:14:25.651788 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209085412 ecr 749536484], length 0
> 02:14:29.722527 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209089482 ecr 749536484], length 0
> 02:14:37.618090 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209097379 ecr 749536484], length 0
> 02:14:53.178362 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209112938 ecr 749536484], length 0
> 02:15:08.737766 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209128498 ecr 749536484], length 0
> 02:15:24.307989 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [F.], seq 557, ack 418, win 159, options [nop,nop,TS val 3209144068 ecr 749536484], length 0
> 02:15:39.869441 IP 127.0.0.1.80 > 127.0.0.1.5423: Flags [R.], seq 558, ack 418, win 159, options [nop,nop,TS val 3209159630 ecr 749536484], length 0
> 
> What purpose for this retransmits?

A few questions:
1) What svn rev are you on? 
2) Does this happen all the time or is there a specific trigger?
3) Do you see this on -head?

Cheers,
Hiren
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