[Bug 998832] [NEW] [procps] sysctl reports missing variable that isn't (net.ipv4.tcp_allowed_congestion_control)

[Rebecca Menessec]

Public bug reported:

sysctl can list this variable, but apparently not set it. strace output
is pretty useless:

open("/proc/version", O_RDONLY)         = 3
fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fe6d54f9000
read(3, "Linux version 3.2.0-24-generic ("..., 1024) = 143
close(3)                                = 0
munmap(0x7fe6d54f9000, 4096)            = 0
open("/sys/devices/system/cpu/online", O_RDONLY|O_CLOEXEC) = 3
read(3, "0-3\n", 8192)                  = 4
close(3)                                = 0
open("/proc/sys/net/ipv4/tcp_allowed_congestion_control", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fe6d54f9000
write(3, "illinois westwood lp\n", 21)  = -1 ENOENT (No such file or directory)
close(3)                                = 0
munmap(0x7fe6d54f9000, 4096)            = 0
write(2, "error: \"No such file or director"..., 89error: "No such file or directory" setting key "net.ipv4.tcp_allowed_congestion_control"
) = 89
exit_group(-1)                          = ?

Here's listing and failing to set:

host ~ [0]# sysctl net.ipv4.tcp_allowed_congestion_control
net.ipv4.tcp_allowed_congestion_control = illinois cubic reno
host ~ [0]# sysctl net.ipv4.tcp_allowed_congestion_control="illinois westwood lp"
error: "No such file or directory" setting key "net.ipv4.tcp_allowed_congestion_control"
host  ~ [255]#

Is this possibly related to a bad AppArmor profile? I've never
encountered this on a non-Ubuntu system. On top of this, I can set
net.ipv4.tcp_congestion_control with no error, and sysctl shows the
change afterward.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: procps 1:3.2.8-11ubuntu6
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Sun May 13 13:25:31 2012
InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: procps
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.sysctl.conf: 2012-05-13T13:22:37.626745

** Affects: procps (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug precise third-party-packages

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https://bugs.launchpad.net/bugs/998832

Title:
  [procps] sysctl reports missing variable that isn't
  (net.ipv4.tcp_allowed_congestion_control)

Status in “procps” package in Ubuntu:
  New

Bug description:
  sysctl can list this variable, but apparently not set it. strace
  output is pretty useless:

  open("/proc/version", O_RDONLY)         = 3
  fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
  mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fe6d54f9000
  read(3, "Linux version 3.2.0-24-generic ("..., 1024) = 143
  close(3)                                = 0
  munmap(0x7fe6d54f9000, 4096)            = 0
  open("/sys/devices/system/cpu/online", O_RDONLY|O_CLOEXEC) = 3
  read(3, "0-3\n", 8192)                  = 4
  close(3)                                = 0
  open("/proc/sys/net/ipv4/tcp_allowed_congestion_control", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
  fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
  mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fe6d54f9000
  write(3, "illinois westwood lp\n", 21)  = -1 ENOENT (No such file or directory)
  close(3)                                = 0
  munmap(0x7fe6d54f9000, 4096)            = 0
  write(2, "error: \"No such file or director"..., 89error: "No such file or directory" setting key "net.ipv4.tcp_allowed_congestion_control"
  ) = 89
  exit_group(-1)                          = ?

  Here's listing and failing to set:

  host ~ [0]# sysctl net.ipv4.tcp_allowed_congestion_control
  net.ipv4.tcp_allowed_congestion_control = illinois cubic reno
  host ~ [0]# sysctl net.ipv4.tcp_allowed_congestion_control="illinois westwood lp"
  error: "No such file or directory" setting key "net.ipv4.tcp_allowed_congestion_control"
  host  ~ [255]#

  Is this possibly related to a bad AppArmor profile? I've never
  encountered this on a non-Ubuntu system. On top of this, I can set
  net.ipv4.tcp_congestion_control with no error, and sysctl shows the
  change afterward.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: procps 1:3.2.8-11ubuntu6
  ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
  Uname: Linux 3.2.0-24-generic x86_64
  ApportVersion: 2.0.1-0ubuntu7
  Architecture: amd64
  Date: Sun May 13 13:25:31 2012
  InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
  ProcEnviron:
   TERM=linux
   PATH=(custom, no user)
   LANG=en_US.utf8
   SHELL=/bin/bash
  SourcePackage: procps
  UpgradeStatus: No upgrade log present (probably fresh install)
  mtime.conffile..etc.sysctl.conf: 2012-05-13T13:22:37.626745

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