IP bad-len 0 ( on em0 )

Vitezslav Novy vnovy at vnovy.net
Mon Mar 10 14:27:07 PDT 2008

Steven Hartland wrote:
> Did you ever get anywhere with this? Did Jack respond?
> ----- Original Message ----- From: "Nikolay Pavlov" <qpadla at gmail.com>
> On Wednesday 06 February 2008 19:12:20 Vitezslav Novy wrote:
>> >> Do you have set TSO flag on interface?
>> >
>> > Good catch. The problem is gone with net.inet.tcp.tso set to 0.
>> > But TSO is enabled by default in 7.0. Could this be a em driver bug?
>> I don't know. I only saw this when researched another TSO related
>> problem.
>> vita
> May be Jack could say something about this?

It is TSO related problem of em driver.
Affects only cards with adapter->hw.mac.type < e1000_82575.
During transmit function em_tso_setup is called and this function sets 
packet ip_len field to zero. (also ip csum)

After successful transmit, packet is injected to BPF with zeroed ip_len 


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