From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: expected behavior of PF_PACKET on NETIF_F_HW_VLAN_RX device?
Date: Thu, 01 Nov 2007 15:07:23 -0700 (PDT)
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From: Rick Jones <rick.jones2@hp.com>
Date: Thu, 01 Nov 2007 15:04:12 -0700

> David Miller wrote:
> > From: Rick Jones <rick.jones2@hp.com>
> > Date: Thu, 01 Nov 2007 14:48:45 -0700
> > 
> > 
> >>One could I suppose try to ammend the information passed to allow
> >>tcpdump to say "oh, this was a tx packet on the same machine on
> >>which I am tracing so don't worry about checksum mismatch"
> > 
> > 
> > We do this already!
> 
> I'll try to go pester folks in tcpdump-workers then.

The thing to check is "TP_STATUS_CSUMNOTREADY".

When using mmap(), it will be provided in the descriptor.  When using
recvmsg() it will be provided via a PACKET_AUXDATA control message
when enabled via the PACKET_AUXDATA socket option.