netdev - "ping6 -M do" fragments packets

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Date:	Fri, 12 Oct 2007 11:18:41 -0400
From:	Chuck Anderson <cra@....EDU>
To:	netdev@...r.kernel.org
Subject: "ping6 -M do" fragments packets

I'm not subscribed, so please Cc: me on any responses.  Thanks.

According to the man page, ping6 should support the "-M do" option so 
never fragment packets, which I'd like to use for testing the MTU of a 
path.  This option works fine for IPv4 ping, but doesn't work with 
IPv6 ping6.  I can guarantee that I don't have an MTU of 63356 :-)

>ping6 -M do -s 65527 www.kame.net
PING www.kame.net(orange.kame.net) 65527 data bytes
65535 bytes from orange.kame.net: icmp_seq=1 ttl=49 time=224 ms
65535 bytes from orange.kame.net: icmp_seq=2 ttl=49 time=226 ms
65535 bytes from orange.kame.net: icmp_seq=3 ttl=49 time=224 ms

--- www.kame.net ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 224.118/225.270/226.909/1.251 ms

Sure enough, wireshark reports fragments:

No.     Time        Source                Destination           Protocol Info
      1 0.000000    2001:468:616:8c9:213:72ff:fe74:da15 2001:200:0:8002:203:47ff:fea5:3085 IPv6     IPv6 fragment (nxt=ICMPv6 (0x3a) off=0 id=0x79)
      2 0.000007    2001:468:616:8c9:213:72ff:fe74:da15 2001:200:0:8002:203:47ff:fea5:3085 IPv6     IPv6 fragment (nxt=ICMPv6 (0x3a) off=1448 id=0x79)
      3 0.000010    2001:468:616:8c9:213:72ff:fe74:da15 2001:200:0:8002:203:47ff:fea5:3085 IPv6     IPv6 fragment (nxt=ICMPv6 (0x3a) off=2896 id=0x79)
      4 0.000013    2001:468:616:8c9:213:72ff:fe74:da15 2001:200:0:8002:203:47ff:fea5:3085 IPv6     IPv6 fragment (nxt=ICMPv6 (0x3a) off=4344 id=0x79)
      5 0.000015    2001:468:616:8c9:213:72ff:fe74:da15 2001:200:0:8002:203:47ff:fea5:3085 IPv6     IPv6 fragment (nxt=ICMPv6 (0x3a) off=5792 id=0x79)
      6 0.000018    2001:468:616:8c9:213:72ff:fe74:da15 2001:200:0:8002:203:47ff:fea5:3085 IPv6     IPv6 fragment (nxt=ICMPv6 (0x3a) off=7240 id=0x79)


Is this a known issue, or some issue with the Fedora build I'm using?

iputils-20070202-3.fc7

Thanks.
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