dhclient uses 100% cpu when ipv6 is not igored

[Oli Wade]

When network manager is set so "automatic" or "automatic (addresses only)" for ipv6, dhclient is observed to use 100% CPU.

There are no apparent errors in the syslog. Setting ipv6 to "ignore" solves the problem.

When it is not ignored, ipv6 addressing seems to complete (both dhcp and sac); when it is ignored only the sac address gets configured.

Typical "top" output without ignoring ipv6:
====
top - 22:51:11 up 20 min, 2 users, load average: 2.43, 2.85, 2.15
Tasks: 158 total, 3 running, 155 sleeping, 0 stopped, 0 zombie
Cpu(s): 48.2%us, 22.6%sy, 0.0%ni, 29.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1015240k total, 913120k used, 102120k free, 41016k buffers
Swap: 1648636k total, 18388k used, 1630248k free, 398052k cached

  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
 2981 root 20 0 2924 1352 1040 R 99 0.1 12:10.90 dhclient
 2382 i 20 0 771m 171m 31m S 10 17.3 2:36.07 firefox
====

[Oli Wade (olithered)]

Version "4.1.ESV-R4-0ubuntu5.8" in Precise (12.04).