IPSecv6 tunnel mode beahviour
From: Joy Latten <hidden>
Date: 2004-11-01 19:14:50
I am using 2.6.9 + 2.6.10-rc1 + 2.6.10-rc1-bk5 kernel. I also recall seeing this before 2.6.9... I am running IPSecv6 in tunnelmode and am noticing what I think is odd behaviour. First, I have a simple config where packets go from one subnet to another through my ipsec tunnel. I noticed TCPv6 packets are being fragmented at the tunnel. I did not see this using similar configuration with ipv4. Although the packets are received ok, sniffer output looks odd to me, it appears Fragment header was not removed at tunnel endpoint because I still see it after packet was forwarded on subnet to receiving machine. Sniffer on receiving machine's interface shows... Frame 15... Ethernet II... Internet Protocol Version 6 Fragmentation Header Next Header TCP Offset: 0 More fragments: No Identification: 0x00000000 Transmission Protocol.. I see odd behaviour in ICMPv6 too if I send packet larger than mtu of sender. Packet is fragmented twice, once at sender and then again at tunnel entry point. My ping works fine, but, what is odd, is that again Fragment Header is not removed, such that after packet is forwarded onto receiving subnet and reaches receiving machine, there are 2 fragment headers. sniffer output on receiver... Frame 1... Ethernet II... Internet Protocol Version 6 Fragment Header Next header: IPv6 fragment(0x2c) Offset: 0 More fragments: No Identification: 0x00000000 Fragment Header Next header: ICMPv6 (0x3a) Offset: 0 More fragments: Yes Identification: 0x1300000 Internet Control Message Protocol v6 What is the correct behaviour? Who should be removing Fragment Header... tunnel endpoint... or should it even be there in TCPv6 case? Joy Latten