Alan,
We are having some trouble with RedHat's 2.2.19 kernel talking TCP when
the ack of the syn-ack during the 3 way handshake gets dropped.
The kernel has no additional patches, but has been recompiled.
tcpdump trace of RedHat's 2.2.19, decom01-gr is running Linux, nrs02-pu
is running Tru64 4.0d:
10:24:42.007945 > decom51-gr.dish.uplink.1016 >
nrs02-pu.dish.uplink.1022: S 2181164545:2181164545(0) win 32120 <mss
1460,sackOK,timestamp 68814196 0,nop,wscale 0> (DF)
10:24:42.049098 < nrs02-pu.dish.uplink.1022 >
decom51-gr.dish.uplink.1016: S 1985791700:1985791700(0) ack 2181164546
win 33580 <mss 1460,nop,wscale 0> (DF)
*** this ack gets lost ***
10:24:42.049198 > decom51-gr.dish.uplink.1016 >
nrs02-pu.dish.uplink.1022: . 1:1(0) ack 1 win 32120 (DF)
*** nrs02 retransmits syn-ack ***
10:24:48.505996 < nrs02-pu.dish.uplink.1022 >
decom51-gr.dish.uplink.1016: S 1985791700:1985791700(0) ack 2181164546
win 33580 <mss 1460,nop,wscale 0> (DF)
*** nrs02 retransmits syn-ack ***
10:25:13.007212 < nrs02-pu.dish.uplink.1022 >
decom51-gr.dish.uplink.1016: S 1985791700:1985791700(0) ack 2181164546
win 33580 <mss 1460,nop,wscale 0> (DF)
*** nrs02 resets link, but even then Linux does not respond ***
10:25:57.507858 < nrs02-pu.dish.uplink.1022 >
decom51-gr.dish.uplink.1016: R 0:0(0) ack 1 win 33580 (DF)
20 minutes later, connection has not timed out.
The problem does not occur with RedHat's 2.2.17-14:
13:29:55.168486 > decom51-gr.dish.uplink.1016 >
nrs02-pu.dish.uplink.1019: S 1023562949:1023562949(0) win 32120 <mss
1460,sackOK,timestamp 663579 0,nop,wscale 0> (DF)
13:29:55.213289 < nrs02-pu.dish.uplink.1019 >
decom51-gr.dish.uplink.1016: S 129268475:129268475(0) ack 1023562950 win
33580 <mss 1460,nop,wscale 0> (DF)
*** this ack gets lost ***
13:29:55.213360 > decom51-gr.dish.uplink.1016 >
nrs02-pu.dish.uplink.1019: . 1:1(0) ack 1 win 32120 (DF)
*** nrs02 retransmits syn-ack ***
13:30:01.275229 < nrs02-pu.dish.uplink.1019 >
decom51-gr.dish.uplink.1016: S 129268475:129268475(0) ack 1023562950 win
33580 <mss 1460,nop,wscale 0> (DF)
*** Linux resends ack ***
13:30:01.275293 > decom51-gr.dish.uplink.1016 >
nrs02-pu.dish.uplink.1019: . 1:1(0) ack 1 win 32120 (DF)
13:30:01.320754 < nrs02-pu.dish.uplink.1020 >
decom51-gr.dish.uplink.shell: P 6:15(9) ack 1 win 33580 (DF)
<snip>
Please let me know if you want any extra info.
Andre
--
andre.delafontaine at echostar.com
F20 DSS: BD75 66D9 5B2C 66CE 9158 BB27 B199 59CE D117 4E9F
F16 RSA: F8 04 FE 50 02 B5 03 02 F6 87 C7 8D F9 2E B8 58
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