[Dnsmasq-discuss] Forked processes and supervise

[clemens fischer]

'uname -rims' -> Linux 2.6.34-spott i686 AuthenticAMD
'dnsmasq -v' ->
Dnsmasq version 2.56test2  Copyright (c) 2000-2010 Simon Kelley
Compile time options IPv6 GNU-getopt no-DBus no-I18N DHCP TFTP

I'm running a number of processes supervised by [1] and logged by [2].
The design of these tools requires the supervised service to be
a single, possibly threaded process sending all status info either to
syslog or to stdout/stderr.  The often very simple script starting the
service _must_ use execve(2) on it, which is the only way the superviser
can see if the real server process is alive.  This also means that
processes that fork(2) the "real" server and then wait for it or
terminate sabotage this mechanism.

My problem is this:

Every once in a while clients receiving DHCP/DNS from dnsmasq are "hung
up".  I'm quite certain that it is not dnsmasq killing the networking,
but when this happens, I suddenly see two dnsmasq processes, one being
a child of the other:

  pstree -Aa ->
  ...
  `-runsv,2290 dhcp-server
      |-dnsmasq,1880,nobody -C /etc/dnsmasq.conf -u nobody -g nobody ...
      |   `-dnsmasq,1944,root -C /etc/dnsmasq.conf -u nobody -g nobody ...
      `-svlogd,30206,log -r . ./log/ ./notify/
  ...

Normally I have exactly one dnsmasq and its logger with a pipe between
them managed by runsv.

So my question is:  under what circumstance does dnsmasq fork itself
when run by exec?


[1] http://smarden.org/runit/
[2] http://smarden.org/runit/svlogd.8.html (http://smarden.org/socklog/)


clemens