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[Bug 1403955] [NEW] DHCP's "Option interface-mtu 9000" is being ignored on bridge interface br0

To: touch-packages@xxxxxxxxxxxxxxxxxxx
From: Launchpad Bug Tracker <1403955@xxxxxxxxxxxxxxxxxx>
Date: Mon, 05 Jan 2015 10:37:00 -0000
Reply-to: Bug 1403955 <1403955@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

You have been subscribed to a public bug:

In an env with jumbo frames enabled, and using MAAS as DHCP server, the
client receives the following IPv4 lease:

$ cat /var/lib/dhcp/dhclient.br0.leases
lease {
  interface "br0";
  fixed-address 10.230.20.26;
  filename "pxelinux.0";
  option subnet-mask 255.255.248.0;
  option dhcp-lease-time 43200;
  option routers 10.230.16.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 10.230.20.1;
  option domain-name-servers 10.230.20.1;
  option interface-mtu 9000;
  option broadcast-address 10.230.23.255;
  option domain-name "ctsstack.qa.1ss";
  renew 3 2014/12/17 16:48:15;
  rebind 3 2014/12/17 21:52:09;
  expire 3 2014/12/17 23:22:09;
}

The interfaces show the following config after boot:

$ ifconfig br0
br0       Link encap:Ethernet  HWaddr a0:d3:c1:01:9d:58
          inet addr:10.230.20.26  Bcast:10.230.23.255  Mask:255.255.248.0
          inet6 addr: fe80::a2d3:c1ff:fe01:9d58/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:530530 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1591569 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:68713489 (68.7 MB)  TX bytes:213710979 (213.7 MB)

$ ifconfig eth0
eth0      Link encap:Ethernet  HWaddr a0:d3:c1:01:9d:58
          inet6 addr: fe80::a2d3:c1ff:fe01:9d58/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:10539274 errors:0 dropped:3394 overruns:0 frame:454
          TX packets:2627412 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2320560616 (2.3 GB)  TX bytes:3562885157 (3.5 GB)
          Interrupt:32


"option interface-mtu 9000;" from the lease file is being ignored by br0. Could it be related to eth0 MTU size? If that's the case, shouldn't both interfaces be updated?

Other info:

$ brctl show br0
bridge name	bridge id		STP enabled	interfaces
br0		8000.a0d3c1019d58	no		eth0

$ cat /etc/network/eth0.config
iface eth0 inet manual

auto br0
iface br0 inet dhcp
  bridge_ports eth0

** Affects: isc-dhcp (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: cts
-- 
DHCP's "Option interface-mtu 9000" is being ignored on bridge interface br0
https://bugs.launchpad.net/bugs/1403955
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