SIOCGIFMEDIA problems

[gnn at freebsd.org]

At Fri, 13 May 2005 19:17:05 +0200,
Sebastien Petit wrote:
> 
> On Fri, 13 May 2005 08:33:32 -0400
> gnn at freebsd.org wrote:
> 
> > At Fri, 13 May 2005 11:10:13 +0200,
> > Sebastien Petit wrote:
> > > 
> > > Hi -net hackers,
> > > 
> > > A little question about SIOCGIFMEDIA ioctl:
> > >
> > > Somebody reports me that some interfaces (bge / em but anothers
> > > perhaps) seem to discard packet(s) during SIOCGIFMEDIA ioctl, Is it
> > > true and why ?
> > 
> > At least in the case of the em driver it's because eventually
> > em_init_locked() is called which re-initializes the whole device,
> > including the memory buffers.  It is unlikely that packets in the
> > buffers would survive that :-)  I suspect the same is true of bge.
> 
> Hmm. Ok,
> 

> My question is oriented for my software freevrrpd, for checking the
> state of the network cards and do some monitoring on the network
> cards, I use the SIOCGIFMEDIA ioctl in a regular interval. But some
> VRRP packets from the MASTER server are dropped by the SLAVE server
> if this ioctl occurs in the same time.  A solution will be to
> disable this ioctl but I cannot check the network card status
> anymore without perturbating communications.  Why it's necessary to
> reinitialize the device for that ?! I propose to modify the
> SIOCGIFMEDIA for no resetting cards if it's not necessary for
> checking state :) btw, em and bge cards under FreeBSD 4.x are very
> long for changing state (down to up in 2 or 3 seconds before packets
> can be sent/received), I don't know if this is the case under
> FreeBSD 5.x but this can cause some problems :/
> 
> What do you think about that ?

Actually, my mistake, it is the SIFMEDIA ioctl that causes a reset.
GIFMEDIA should not cause a problem, at least not in that way so I'm
not sure why this is happening.  I don't see anything obvious in the
code, but perhaps someone more expert in em/bge will chime in.

Later,
George