Public bug reported:
The openssh-client bundled with Ubuntu 12.04 fails to set the IP Type of
Service field to "minimize delay (0x04)" for interactive SSH sessions. Just
about any other flavor of Linux/UNIX does this without any trouble. Even if I
attempt to force the setting in /etc/ssh/sshd_config:
IPQoS lowdelay
The outgoing SSH packets do not have the bit set.
See this example with tcpdump output:
[steve.polyack@galvatron ~]$ sudo tcpdump -i eth0 -vvv -tttt -n 'host 2.2.2.2
&& dst port 22'
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535
bytes
^Z
[1]+ Stopped sudo tcpdump -i eth0 -vvv -tttt -n 'host 2.2.2.2
&& dst port 22'
[steve.polyack@galvatron ~]$ bg
[1]+ sudo tcpdump -i eth0 -vvv -tttt -n 'host 2.2.2.2 && dst port 22' &
[steve.polyack@galvatron ~]$ ssh 2.2.2.2
2012-10-16 17:20:39.113321 IP (tos 0x0, ttl 64, id 58664, offset 0, flags [DF],
proto TCP (6), length 60)
1.1.1.1.36127 > 2.2.2.2.22: Flags [S], cksum 0x2dd5 (incorrect -> 0x200d),
seq 3930407303, win 14600, options [mss 1460,sackOK,TS val 1670554799 ecr
0,nop,wscale 7], length 0
2012-10-16 17:20:39.298676 IP (tos 0x0, ttl 64, id 58665, offset 0, flags [DF],
proto TCP (6), length 52)
1.1.1.1.36127 > 2.2.2.2.22: Flags [.], cksum 0x2dcd (incorrect -> 0x5cd6),
seq 3930407304, ack 1359170341, win 115, options [nop,nop,TS val 1670554846 ecr
2310866035], length 0
2012-10-16 17:20:39.329979 IP (tos 0x0, ttl 64, id 58666, offset 0, flags [DF],
proto TCP (6), length 52)
1.1.1.1.36127 > 2.2.2.2.22: Flags [.], cksum 0x2dcd (incorrect -> 0x5c8c),
seq 0, ack 40, win 115, options [nop,nop,TS val 1670554853 ecr 2310866063],
length 0
2012-10-16 17:20:39.330082 IP (tos 0x0, ttl 64, id 58667, offset 0, flags [DF],
proto TCP (6), length 91)
1.1.1.1.36127 > 2.2.2.2.22: Flags [P.], cksum 0x2df4 (incorrect -> 0x9e6b),
seq 0:39, ack 40, win 115, options [nop,nop,TS val 1670554853 ecr 2310866063],
length 39
2012-10-16 17:20:39.759001 IP (tos 0x0, ttl 64, id 58668, offset 0, flags [DF],
proto TCP (6), length 1324)
1.1.1.1.36127 > 2.2.2.2.22: Flags [P.], cksum 0x32c5 (incorrect -> 0x916a),
seq 39:1311, ack 776, win 126, options [nop,nop,TS val 1670554961 ecr
2310866492], length 1272
The problem persists even after login, once the SSH session is fully
interactive:
2012-10-16 17:20:49.626239 IP (tos 0x0, ttl 64, id 58694, offset 0, flags [DF],
proto TCP (6), length 116)
1.1.1.1.36127 > 2.2.2.2.22: Flags [P.], cksum 0x2e0d (incorrect -> 0xb06e),
seq 3479:3543, ack 5344, win 226, options [nop,nop,TS val 1670557427 ecr
2310876270], length 64
This causes problems in environements where QoS is used and IP ToS is obeyed.
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: openssh-client 1:5.9p1-5ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-27.43-generic 3.2.21
Uname: Linux 3.2.0-27-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu13
Architecture: amd64
Date: Tue Oct 16 17:14:19 2012
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcEnviron:
LANGUAGE=en_US:en
TERM=xterm
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
RelatedPackageVersions:
ssh-askpass N/A
libpam-ssh N/A
keychain N/A
ssh-askpass-gnome 1:5.9p1-5ubuntu1
SSHClientVersion: OpenSSH_5.9p1 Debian-5ubuntu1, OpenSSL 1.0.1 14 Mar 2012
SourcePackage: openssh
UpgradeStatus: Upgraded to precise on 2012-07-06 (102 days ago)
modified.conffile..etc.ssh.ssh.config: [modified]
mtime.conffile..etc.ssh.ssh.config: 2012-10-05T09:52:10.902327
** Affects: openssh (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug precise
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Server Team, which is subscribed to openssh in Ubuntu.
https://bugs.launchpad.net/bugs/1067522
Title:
openssh-client / ssh does not set IP Type-of-service field
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