[Bug 265588] [TCP] - tcp send a retransmission identical sequence number packet with different payload

From: <bugzilla-noreply_at_freebsd.org>
Date: Thu, 20 Oct 2022 08:16:42 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=265588

--- Comment #5 from Richard Scheffenegger <rscheff@freebsd.org> ---
Where are the two independent packet traces, if you traced on both client and
server at the same time?

Also, disabling SACK will lead to much worst packet loss recovery performance,
while also prevent TSO / LRO issues simulatanouely.

A SACK enabled, LRO/TSO disabled test would be interesting.



I asked awk to create a simple 32bit sum of the 1448-byte payload segments
making up the LRO chunks, for all the data segments with an even multiple:

(sum32 is not perfect, but should be sufficient to see identical sub-sections;
note that prior to the capture, the packets  appear to have been sent before,
which are in frame #4 - #21.

the first 1448byte chunk in #63 is identical to #66, indicating this could be
an off-by-one mbuf issue. All duplicate, subsequently seen chunks are prefixed
with # below.


packet #63 should have many overlaps with packets #55 and #57 - but they do NOT
correspond properly...

3rd chunk of #63 should be 1st chunk of #55, but only chunks 4 and 2 (and
following) are the same, similar between #63/13 and #57/1, where only
subsequent chunks are the same...


frame.number ip.src tcp.seq(rel) tcp.ack(rel) tcp.len #_1448_segs
[sum32 sum32...]


2 10.234.1.9 35249 229 15928 11
72053392291     385714934591    419632206729    401031568921    410043220839   
398170924830    381008236919    388657879560    400554947764    390059647829
401051361480

4 10.234.1.9 8689 229 1448 1
402468043721
5 10.234.1.9 10137 229 1448 1
401277757279
6 10.234.1.9 11585 229 1448 1
415282924207
7 10.234.1.9 13033 229 1448 1
384078634026
8 10.234.1.9 14481 229 1448 1
403972324660
9 10.234.1.9 15929 229 1448 1
406377582180
10 10.234.1.9 17377 229 1448 1
395849724237
11 10.234.1.9 18825 229 1448 1
407105644009
12 10.234.1.9 20273 229 1448 1
391049306449
13 10.234.1.9 21721 229 1448 1
392972187658
14 10.234.1.9 23169 229 1448 1
412806674913
15 10.234.1.9 24617 229 1448 1
368815440121
16 10.234.1.9 26065 229 1448 1
441426216789
17 10.234.1.9 27513 229 1448 1
413962289118
18 10.234.1.9 28961 229 1448 1
410986024398
19 10.234.1.9 30409 229 1448 1
411104040736
20 10.234.1.9 31857 229 1448 1
401688330533
21 10.234.1.9 33305 229 1448 1
0

23 10.234.1.9 51177 229 2896 2
#0      203246954054



27 10.234.1.9 54073 229 5792 4
394852055780    384030294443    392529581011    386143976667

29 10.234.1.9 59865 229 7240 5
396719530022    411466448353    385699980034    379232637059    398683035014

31 10.234.1.9 67105 229 2896 2
404469974242    419769008759

33 10.234.1.9 70001 229 7240 5
390781603776    405293380528    401115408251    408555360267    401962764123

35 10.234.1.9 77241 229 5792 4
410414639507    399252713459    422519480994    402128188056

37 10.234.1.9 83033 229 5792 4
397118187855    389763261786    385790875737    396498279313

39 10.234.1.9 88825 229 10136 7
410833492195    394727248034    434370688504    405654811556    415670751773   
381338791549    363187342839

41 10.234.1.9 98961 229 7240 5
373714275313    408842605624    118929186736    #0      772816864

43 10.234.1.9 106201 229 2896 2
409221826523    405055397380

45 10.234.1.9 109097 229 5792 4
409248775808    407813669100    400196811736    393952527415

47 10.234.1.9 114889 229 5792 4
428166500303    407670732874    391317321268    398231044986

49 10.234.1.9 120681 229 4344 3
153542385751    #0      1379131396

51 10.234.1.9 125025 229 7240 5
383437534358    417050426910    408105259593    391024117815    402553991311



55 10.234.1.9 132265 229 7240 5
398609113564    394899607335    404273196631    377759935477    372329922394

57 10.234.1.9 139505 229 17376 12
406899099155    377008101980    389519299155    398503947093    403573177749   
412798843978    378308644919    409772644714    397983176629    424631857245
397732366425     386270375516




62 10.234.1.9 129369 229 1448 1
421647638868
63 10.234.1.9 129369 229 27512 19
409602081388    400590437965    395728025774    #394899607335   #404273196631  
#377759935477   #372329922394   407165511753    411371394473    384531841671
365127713737     404990193304    407773333546    #377008101980   #389519299155 
 #398503947093   #403573177749   #412798843978   #378308644919


66 10.234.1.9 130817 457 1448 1
#409602081388
67 10.234.1.9 156881 457 5792 4
403565719067    397983667401    432116192336    383972004598

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