[Bug 598275] Re: read() builtin doesn't work with /proc files containing only an integer value

[Brian Murray]

** Summary changed:

- munin-node fw_conntrack plugin reports incorrect critical threshold
+ read() builtin doesn't work with /proc files containing only an integer value

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https://bugs.launchpad.net/bugs/598275

Title:
  read() builtin doesn't work with /proc files containing only an
  integer value

Status in “dash” package in Ubuntu:
  Confirmed
Status in “dash” package in Debian:
  Confirmed

Bug description:
  Binary package hint: munin

  Ubuntu 10.04 LTS, munin-node 1.4.4-1ubuntu1.  On my newly installed
  Lucid server, Munin's fw_conntrack plugin reports the "critical"
  number of network connects as 5 or 6.  This means that I get constant
  alerts about having too many network connections.  I think this is
  actually caused by a bug in dash's built-in read command.
  Fw_conntrack gets its max connection number by reading
  /proc/sys/net/ipv4/ip_conntrack_max or
  /proc/sys/net/ipv4/netfilter/ip_conntrack_max around line 110 of
  /usr/share/munin/plugins/fw_conntrack.  Like this:

      read MAX < /proc/sys/net/ipv4/netfilter/ip_conntrack_max

  If I run this in bash:

      bash# read MAX < /proc/sys/net/ipv4/netfilter/ip_conntrack_max && echo good: $MAX || echo bad: $MAX
      good: 7852

  but in dash:

      dash# read MAX < /proc/sys/net/ipv4/netfilter/ip_conntrack_max && echo good: $MAX || echo bad: $MAX
      bad: 7

  So dash's read is failing AND setting $MAX.  I imagine this is a bug
  in dash, but fw_conntrack is also ignoring the fact that read is
  returning failure.

  Changing fw_conntrack's #! line to #!/bin/bash works around the
  problem, but I wouldn't call that a fix.

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