IPFW V2 dynamic keepalives broken

[Gregory Neil Shapiro]

> i imagine the following happens:
>  + the client does not properly close the connection;

I tend to agree.

>  + when a keepalive is sent (every 5 minutes),

But wouldn't a dyn_fin_lifetime of 1 mean it wouldn't reach 5 minutes?

>    the the server's TCP responds (thus refreshing the rule), and the

Interestingly enough, the client can't respond.  An upstream Nokia
Checkpoint FW-1 firewall is rejecting the packets from the client to
the server with "Unknown established connection".  You are correct
though, the server may be responding.  

>    TCP timeout is reset so it stays in the FIN_WAIT[2] state for
>    another cycle, whereas the client does not bother to send back a
>    RST (which would cause the timeout for the dynamic rule go down to
>    very low values).

> Maybe i should change the logic in the dynamic rules so that further
> keepalives are not sent unless a reply has been received from both
> sides.

That does sound like a good solution.

> > # sysctl net.inet.ip.fw.dyn_keepalive=0
> > net.inet.ip.fw.dyn_keepalive: 1 -> 0
> > (wait a few seconds)
> 
> how "few" seconds ? I suppose in the order of 300 or so, enough
> to let the local session expire ?

Yes, sorry, that should have been "few minutes", not "few seconds".

By the way, since sending the mail yesterday, 149 have collected in
FIN_WAIT_2 on the server.  I repeated the process and timed it.
It started dropping them after about 6 minutes.