interface-mtu change from yesterday hoses the network interface

[Manoj Kasichainula]

With the recent changes to request interface-mtu from the dhcp server, the mtu
on that interface got set to 64, effectively making it useless.

I don't know yet if it's a bug in the dhcp client or server, but given that the
dhcp server is part of a NAT-in-a-box bought in a store, I'm guessing I won't be
the only one to see this either way. Reverting the change in dhclient.conf
myself fixed it. I'm not sure the dhcp server will always know the right MTU,
given there can be multiple layer 1 network media hooked up to it in theory, but
ignoring the theory, it breaks for me :)

Environment:

dhcp client: Thinkpad T40p, Atheros 5212 a/g minipci card. Ubuntu hoary updated
frequently
network + dhcp server: SMC 7004ABR w/ 1.42.019 firmware, original Apple graphite
airport w/ Lucent Gold card and latest firmware acting as access point

Entry in /var/run/dhclient.ath0.leases:

lease {
  interface "ath0";
  fixed-address 192.168.2.3;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 604800;
  option routers 192.168.2.1;
  option dhcp-option-overload 3;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.2.1;
  option domain-name-servers 192.168.2.1;
  option interface-mtu 64;
  option broadcast-address 255.255.255.255;
  option domain-name "speakeasy.net";
  renew 6 2005/3/26 20:42:47;
  rebind 6 2005/3/26 20:42:47;
  expire 6 2005/3/26 20:42:47;
}

ifconfig output (after network was host, trying to down + up the interface, MTU
is the important value):

ath0 Link encap:Ethernet HWaddr 00:05:4E:43:4A:87
          UP BROADCAST RUNNING MULTICAST MTU:64 Metric:1
          RX packets:101862 errors:26203 dropped:0 overruns:0 frame:26203
          TX packets:99847 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:199
          RX bytes:31879865 (30.4 MiB) TX bytes:10517044 (10.0 MiB)
          Interrupt:3 Memory:f8be0000-f8bf0000

[Matt Zimmerman (mdz)]

This bug has been marked as a duplicate of bug 14547.

[Manoj Kasichainula (manoj+ubuntu-com)]

Umm, no, this is not a duplicate of 8213. I experienced 8213 and worked around
it already. This is different, please read the description again.

[Matt Zimmerman (mdz)]

Sorry for the confusion.

dhcp3 (3.0.1-1ubuntu4) hoary; urgency=low

  * Revert changes to debian/dhclient.conf, apparently at least some DHCP
    servers supply broken interface-mtu information, so this isn't safe to
    enable without broader testing (Ubuntu #8241)

 -- Matt Zimmerman <email address hidden> Sat, 26 Mar 2005 19:30:09 -0800

[Manoj Kasichainula (manoj+ubuntu-com)]

Entirely coincidentally, I just switched to an openwrt box, so this isn't an
issue for me anymore, but I imagine others may still hit this. thanks for the fix.