Matthew Sullivan wrote: > I'm going to post this back to the list as Marko was also helping me get > to the bottom of it... > > David Malone wrote: > >> On Tue, Apr 19, 2005 at 07:29:18AM +1000, Matthew Sullivan wrote: >> >> >>> Any reason why FreeBSD 5.2.1+ and 5.3-p9 set DF on all packets? >>> >> >> >> It is usual to do this to do path MTU discovery with TCP. I don't >> know what the situation with the packets that the VPN sends is. > Ok well thanks to Andrew _at_ Supernews and a lot of debugging it appears there is a bug.... sys/netinet/ip_icmp.c: line 440 if (!mtu) mtu = ip_next_mtu(mtu, 1); Problem is ip_next_mtu will always return 0 when called with (0, 1) ... so following that with: if (mtu >= max(296, (tcp_minmss + sizeof(struct tcpiphdr)))) tcp_hc_updatemtu(&inc, mtu); and nothing gets changed.... hence why it fails. Apparently the gateway should be suggesting a MTU value for use.... the gateway is also FreeBSD 5.3 so something needs fixing .. :-/ Regards, -- Matthew Sullivan Specialist Systems Programmer Information Technology Services The University of Queensland
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