RE: BUG(?) - SNAT causes networking to stop.

["Darrell Dieringer" <netfilter@darrelldieringer.com>]

I had a goofy problem quite awhile ago that sounds a lot like yours -
I couldn't ping the router box from the LAN unless the router box was
already pinging the particular LAN box from which I was trying to ping
the router.

I didn't use strace, but tcpdump showed me that the packets were
indeed _not_ on the wire.

After banging my head for awhile, I tried a different (identical)
network card in the router for the LAN.  The unusual ping problem was
gone immediately without a single change to the firewall rules.

It's worth a shot.

Darrell Dieringer - Madison, WI


> -----Original Message-----
>
> Howdy folks,
>
> 	I've got a router I am experamenting with SNAT on.
> I've hit a
> situation where local ping processes are forced to stop
> transmitting (get
> caught in a loop on sendmsg() ) until the box receives
> packets from some
> external source (ping it from another machine on the
> network for example),
> and then it wakes right up without missing a beat.
> Experamentally, I've
> had ping waiting for several minutes this way. Typically
> it's able to fire
> off say 10 packets (and get replies) before it starts
> hanging. Using
> larger packets - say, 3000 bytes, results in only being
> able to fire off 3
> before stopping. I'm running tcpdump to verify that it's
> not emitting
> packets and strace to verify it's stuck looping on
> sendmsg(). Very weird.
>