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

[Victor Tapia]

** Description changed:

- Using MAAS as DHCP server, the client receives the following IPv4 lease:
+ 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 
+ $ 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;
+   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)
+ 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 
+ 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 
+ $ cat /etc/network/eth0.config
  iface eth0 inet manual
  
  auto br0
  iface br0 inet dhcp
-   bridge_ports eth0
+   bridge_ports eth0

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https://bugs.launchpad.net/bugs/1403955

Title:
  DHCP's "Option interface-mtu 9000" is being ignored on bridge
  interface br0

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