[Openswan Users] Unusual packet loss

Philip Burrow philburrow at blueyonder.co.uk
Mon Jan 24 13:39:59 CET 2005

Paul Wouters wrote:

> Can you try clamping it?
> iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS  
> --clamp-mss-to-pmtu

Tried this on both ends, no luck.

> Otherwise, try pinging with different size packets until it fails, and 
> then use
> the last successful packet size (eg 1440) to:
> iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1440

Worked this down to 1430 and tried the command you specified but again 
it did not seem to change anything.

> Also, perhaps that DSL router is blocking ICMP's neccessary for proper 
> PMTU to
> begin with?

If it was, would the tunnels come up with no errors to begin with? Each 
of my tunnels comes up with IPSec SA Established, as you would expect.

I will try replacing the router with one I know works. The "dodgy" 
router is a 2wire Homeportal 1800 if that helps. The name "Homeportal" 
makes me think it's probably doing things to cause this problem.

Would KLIPS help me? I built Openswan RPMs from the SRPM so I have a 
KLIPS one (which I have now installed). Is it a simple configuration 
edit to change it to KLIPS?

Thanks Paul.



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