On Sat, 20 Oct 2007, Willy Tarreau wrote:
<CUT>
What is very strange is that linux uses random increments, so your ISNs
should not wrap in a matter of a few seconds.
Good point. I need to investigate this.
netcat is very convenient for such tests. It's easy to bind it to a
source port for consecutive tests while you run tcpdump in the background :
$ echo bla | nc -p 1234 192.168.1.2 80
$ echo bla | nc -p 1234 192.168.1.2 80
Also, please try this with tcp_timestamps enabled and disabled to see if it
changes anything.
Interesting... :|
2.6.20:
18:52:33.558379 IP 192.168.0.33.3333 > 212.77.100.101.80: S 3708509816:3708509816(0)
win 5840 <mss 1460,sackOK,timestamp 1884090256 0,nop,wscale 1>
18:52:33.882129 IP 192.168.0.33.3333 > 212.77.100.101.80: S 3708833567:3708833567(0)
win 5840 <mss 1460,sackOK,timestamp 1884090580 0,nop,wscale 1>
18:52:34.084000 IP 192.168.0.33.3333 > 212.77.100.101.80: S 3709035437:3709035437(0)
win 5840 <mss 1460,sackOK,timestamp 1884090782 0,nop,wscale 1>
2.6.21:
18:58:36.074969 IP 192.168.0.66.3333 > 212.77.100.101.80: S 110585153:110585153(0)
win 5840 <mss 1460,sackOK,timestamp 112007046 0,nop,wscale 5>
18:58:36.440084 IP 192.168.0.66.3333 > 212.77.100.101.80: S 110950271:110950271(0)
win 5840 <mss 1460,sackOK,timestamp 112007412 0,nop,wscale 5>
18:58:36.830141 IP 192.168.0.66.3333 > 212.77.100.101.80: S 111340328:111340328(0)
win 5840 <mss 1460,sackOK,timestamp 112007802 0,nop,wscale 5>
2.6.22:
18:59:34.525097 IP 192.168.0.7.3333 > 212.77.100.101.80: S 3303295586:3303295586(0)
win 5840 <mss 1460,sackOK,timestamp 1111842 0,nop,wscale 6>
18:59:34.942104 IP 192.168.0.7.3333 > 212.77.100.101.80: S 3720303240:3720303240(0)
win 5840 <mss 1460,sackOK,timestamp 1112259 0,nop,wscale 6>
18:59:35.412229 IP 192.168.0.7.3333 > 212.77.100.101.80: S 4190427367:4190427367(0)
win 5840 <mss 1460,sackOK,timestamp 1112729 0,nop,wscale 6>
2.6.22+tcp_timestamps=0:
19:00:38.285554 IP 192.168.0.7.3333 > 212.77.100.101.80: S 2639244549:2639244549(0)
win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 6>
19:00:39.448675 IP 192.168.0.7.3333 > 212.77.100.101.80: S 3802363348:3802363348(0)
win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 6>
19:00:43.003850 IP 192.168.0.7.3333 > 212.77.100.101.80: S 3062574559:3062574559(0)
win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 6>
19:00:45.950863 IP 192.168.0.7.3333 > 212.77.100.101.80: S 1714619373:1714619373(0)
win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 6>
So it seems that ISNs are not randomly incremented but rather randomly
generated. Adding netdev@vger.kernel.org to the CC list.
Best regards,
Krzysztof Olędzki
