LSA Update checksum breaks with large LSA Updates

[Neil Wilson]

Using Bird 1.3.1 OSPF with 'rx buffer large' in the config.

This test system is a couple of bird instances talking to each other.

I've noticed that when LSA updates get above 4000 the checksum system
seems to break.

Before:

Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest: Scheduling routing
table calculation
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest: LSUPD packet received
from 192.168.0.201 via eth0
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest:     length   3964
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest:     router
192.168.0.201
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest:     LSA      Type:
0001, Id: 192.168.0.201, Rt: 192.168.0.201, Age: 0, Seq: 8000000a, Sum:
7113
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest: LSACK packet sent via
eth0
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest:     length   44
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest:     router
192.168.0.20
Jul  1 18:39:21 acer-aspire-5536 bird: cloudtest:     LSA      Type:
0001, Id: 192.168.0.201, Rt: 192.168.0.201, Age: 0, Seq: 8000000a, Sum:
7113

After:

Jul  1 18:39:26 acer-aspire-5536 bird: cloudtest: LSUPD packet received
from 192.168.0.201 via eth0
Jul  1 18:39:26 acer-aspire-5536 bird: cloudtest:     length   4192
Jul  1 18:39:26 acer-aspire-5536 bird: cloudtest:     router
192.168.0.201
Jul  1 18:39:26 acer-aspire-5536 bird: cloudtest:     LSA      Type:
0001, Id: 192.168.0.201, Rt: 192.168.0.201, Age: 1, Seq: 8000000a, Sum:
b77a
Jul  1 18:39:26 acer-aspire-5536 bird: Received bad lsa checksum from
192.168.0.201: 7ab7 4f5b

The two processes then get stuck in a loop constantly requesting,
updating and failing.

Any ideas where the issue might lie?

Rgs

Neil Wilson