I just converted my machine at home to RedHat 6.0 (2.2.9 kernel), and I am now
having trouble with transfers of large files. This happens only to some
machines - in particular, a machine at work running RedHat 5.2 (2.2.9 kernel)
and the server for the TUX mailing list archives. It's fairly easy to
reproduce - all I have to try to do is upload the 2.2.9 kernel source via FTP.
When I run tcpdump at both ends, what I see is that the transfer proceeds
for a short while, and then a data packet gets dropped, leaving a hole.
My home machine sends ack's to indicate the start of the hole, but they
never get to the far end. Meanwhile, the machine at work eventually figures
out that something has gone wrong, and re-sends what it thinks is the missing
packet. Unfortunately, since it never sees the right ack, it sends the wrong
data. At this point, the connection sits forever, until I kill the ftp
process. I've appended parts of the tcpdump output below.
Other bits of possibly relevent information:
- this doesn't happen when the machine at the work is running Solaris,
Linux 2.0.32 or Linux 2.0.36. It also did not happen when the machine at
home was running 2.0.32 (Slackware 3.4)
- this doesn't happen when the machine at home runs SLIP instead of PPP.
- the transmit and receive counts reported by ifconfig/netstat match the
number of packets seen by tcpdump on the machine at home.
- cutting the MTU on my home machine from 552 to 500 did not help. (I tested
SLIP with MTU=296, for what it's worth.)
- I dial in to an Annex server running S/Key; I use DIP to start pppd.
Does anyone out there recognize this? Is there any more debugging I can do?
As you might imagine, this makes PPP rather useless.
-------------------------------------------------------------------------------
Home machine TCP dump
192.4.9.136 is home machine
192.4.7.122 is FTP server
22:26:29.526516 192.4.7.122.20 > 192.4.9.136.1078: . 124501:125001(500) ack 1 win
32500 <nop,nop,timestamp 114048504 572556> (DF) [tos 0x8]
22:26:29.526619 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 573449 114048504,nop,nop, sack 2 {120501:125001}[|tcp]> (DF) [tos
0x8]
22:26:29.686509 192.4.7.122.20 > 192.4.9.136.1078: . 125001:125501(500) ack 1 win
32500 <nop,nop,timestamp 114048504 572556> (DF) [tos 0x8]
22:26:29.686604 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 573465 114048504,nop,nop, sack 2 {120501:125501}[|tcp]> (DF) [tos
0x8]
22:26:29.856504 192.4.7.122.20 > 192.4.9.136.1078: . 125501:126001(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:29.856588 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 573482 114048552,nop,nop, sack 2 {120501:126001}[|tcp]> (DF) [tos
0x8]
22:26:30.016507 192.4.7.122.20 > 192.4.9.136.1078: . 126001:126501(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:30.016591 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 573498 114048552,nop,nop, sack 2 {120501:126501}[|tcp]> (DF) [tos
0x8]
22:26:30.176513 192.4.7.122.20 > 192.4.9.136.1078: . 126501:127001(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:30.176611 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 573514 114048552,nop,nop, sack 2 {120501:127001}[|tcp]> (DF) [tos
0x8]
22:26:30.336512 192.4.7.122.20 > 192.4.9.136.1078: . 127001:127501(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:30.336604 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 573530 114048552,nop,nop, sack 2 {120501:127501}[|tcp]> (DF) [tos
0x8]
22:26:30.506514 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114049153 572604> (DF) [tos 0x8]
22:26:30.506586 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 573547 114049153,nop,nop, sack 2 {120501:127501}[|tcp]> (DF) [tos
0x8]
22:26:57.596519 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114052157 572604> (DF) [tos 0x8]
22:26:57.596623 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 576256 114052157,nop,nop, sack 2 {120501:127501}[|tcp]> (DF) [tos
0x8]
22:27:57.666526 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114058165 572604> (DF) [tos 0x8]
22:27:57.666635 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 582263 114058165,nop,nop, sack 2 {120501:127501}[|tcp]> (DF) [tos
0x8]
22:29:57.656583 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114070165 572604> (DF) [tos 0x8]
22:29:57.656694 192.4.9.136.1078 > 192.4.7.122.20: . ack 96001 win 31500
<nop,nop,timestamp 594262 114070165,nop,nop, sack 2 {120501:127501}[|tcp]> (DF) [tos
0x8]
-------------------------------------------------------------------------------
Server TCP dump
22:26:27.884460 192.4.7.122.20 > 192.4.9.136.1078: . 121001:121501(500) ack 1 win
32500 <nop,nop,timestamp 114048404 572458> (DF) [tos 0x8]
22:26:27.884473 192.4.7.122.20 > 192.4.9.136.1078: . 121501:122001(500) ack 1 win
32500 <nop,nop,timestamp 114048404 572458> (DF) [tos 0x8]
22:26:27.884510 192.4.7.122.20 > 192.4.9.136.1078: . 122001:122501(500) ack 1 win
32500 <nop,nop,timestamp 114048404 572458> (DF) [tos 0x8]
22:26:28.378977 192.4.9.136.1078 > 192.4.7.122.20: . ack 92501 win 31500
<nop,nop,timestamp 572507 114047574> (DF) [tos 0x8]
22:26:28.379014 192.4.7.122.20 > 192.4.9.136.1078: P 122501:123001(500) ack 1 win
32500 <nop,nop,timestamp 114048454 572507> (DF) [tos 0x8]
22:26:28.379027 192.4.7.122.20 > 192.4.9.136.1078: . 123001:123501(500) ack 1 win
32500 <nop,nop,timestamp 114048454 572507> (DF) [tos 0x8]
22:26:28.379056 192.4.7.122.20 > 192.4.9.136.1078: . 123501:124001(500) ack 1 win
32500 <nop,nop,timestamp 114048454 572507> (DF) [tos 0x8]
22:26:28.879880 192.4.9.136.1078 > 192.4.7.122.20: . ack 94001 win 31500
<nop,nop,timestamp 572556 114047606> (DF) [tos 0x8]
22:26:28.879918 192.4.7.122.20 > 192.4.9.136.1078: . 124001:124501(500) ack 1 win
32500 <nop,nop,timestamp 114048504 572556> (DF) [tos 0x8]
22:26:28.879931 192.4.7.122.20 > 192.4.9.136.1078: . 124501:125001(500) ack 1 win
32500 <nop,nop,timestamp 114048504 572556> (DF) [tos 0x8]
22:26:28.879960 192.4.7.122.20 > 192.4.9.136.1078: . 125001:125501(500) ack 1 win
32500 <nop,nop,timestamp 114048504 572556> (DF) [tos 0x8]
22:26:29.361982 192.4.9.136.1078 > 192.4.7.122.20: . ack 95001 win 32500
<nop,nop,timestamp 572604 114047651> (DF) [tos 0x8]
22:26:29.362023 192.4.7.122.20 > 192.4.9.136.1078: . 125501:126001(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:29.362035 192.4.7.122.20 > 192.4.9.136.1078: . 126001:126501(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:29.362061 192.4.7.122.20 > 192.4.9.136.1078: . 126501:127001(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:29.362083 192.4.7.122.20 > 192.4.9.136.1078: . 127001:127501(500) ack 1 win
32500 <nop,nop,timestamp 114048552 572604> (DF) [tos 0x8]
22:26:35.368110 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114049153 572604> (DF) [tos 0x8]
22:27:05.407080 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114052157 572604> (DF) [tos 0x8]
22:28:05.485030 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114058165 572604> (DF) [tos 0x8]
22:30:05.480930 192.4.7.122.20 > 192.4.9.136.1078: . 95001:95501(500) ack 1 win 32500
<nop,nop,timestamp 114070165 572604> (DF) [tos 0x8]
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