Hi Patrick: On Mon, Apr 02, 2007 at 04:10:25PM +0200, Patrick McHardy wrote: > I noticed a problem with PMTUD between two IPsec tunnel endpoints. > When sending a packet larger than the PMTU with IP_DF from one > tunnel endpoint to the other, xfrm4_output sends an ICMP frag. > required with the IPsec MTU. Since the addresses match the tunnel > endpoints, this updates the MTU for the XFRM route with the value > that was calculated for the entire bundle, which in turn causes > a decrease for the bundle, resulting in further ICMP frag. required > messages until the minimum is reached.
I presume you're using the same pair of addresses inside and outside the tunnel? If so the problem is that the kernel doesn't distinguish between internal ICMP errors and external ones. So when an MTU update occurs for the internal pair the external pair is also affected. We'd need some field in the routing cache to distinguish the two pairs. Of course the easy work-around is to use distinct addresses within IPsec tunnels. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
