kern/64718: [patch] Bridged packets still seen by BPF listener after BIOCSEESENT ioctl.

[Darren Reed]

The following reply was made to PR kern/64718; it has been noted by GNATS.

From: Darren Reed <darrenr at hub.freebsd.org>
To: Ed Maste <emaste at sandvine.com>
Cc: Darren Reed <darrenr at FreeBSD.ORG>,
	freebsd-gnats-submit at FreeBSD.org
Subject: Re: kern/64718: [patch] Bridged packets still seen by BPF listener after BIOCSEESENT ioctl.
Date: Sat, 10 Apr 2004 20:43:59 -0700

 On Sat, Apr 10, 2004 at 10:15:07PM -0400, Ed Maste wrote:
 > >It is your expectation that is wrong here.
 > 
 > No, I'm sorry, but at the very least the documentation is 
 > inconsistent.  You left out part of the man page:
 > 
 > BIOCGSEESENT  (u_int) Set or get the flag determining whether locally
 >              generated packets on the interface should be returned by
 >              BPF.  Set to zero to see only incoming packets on the
 >              interface.  
 > 
 > The above makes no reference to packets that are not locally 
 > generated nor received on the interface. 
 
 Ok, can we agree the man page is, perhaps, ambiguous about what
 should happen to forwarded packets ?
 
 In the case of a host that is not a gateway, the above entry does
 make sense.  Agreed ?
 
 > Note however that independent of the above, there's still a bug 
 > with the seesent code.  A struct m_hdr is allocated on the stack
 > and cast to a struct mbuf * in ether_input before the call to
 > bpf_mtap.  The seesent check then accesses m->m_pkthdr.rcvif.
 
 Yes, I can see that.
 However, FreeBSD-current doesn't work this way any more, so this
 fix would be a 4.x one only, if something were to be changed.
 
 Darren