Comment 0 for bug 1176046

Ubuntu 13.04 Server 64-bit. Fresh install. Only one network adapter.

dhclient process is listening on two randomly chosen udp ports in addition to the usual port 68. This appears to be a bug in the discovery code for probing information on interfaces in the system.

Initial research of the code also suggested omapi, but adding omapi port 9999 to /etc/dhcp/dhclient.conf only opened a forth port with the two random udp ports still enabled.

Version of included distro dhclient was 4.2.4. I also tested with the latest isc-dhclient-4.2.5-P1 and got the same results.

Debian has the same bug: http://forums.debian.net/viewtopic.php?f=10&t=95273&p=495605#p495605

One impact of these random ports is that security hardening becomes more difficult. The purpose of these random ports and security implications are unknown.

Example netstat -lnp output:

udp 0 0 0.0.0.0:21117 0.0.0.0:* 2659/dhclient
udp 0 0 0.0.0.0:68 0.0.0.0:* 2659/dhclient
udp6 0 0 :::45664 :::* 2659/dhclient