IPv6 packet creation tool

[Matthew Luckie]

> I need to create a single packet which has a fragmentation header
> and is not the first packet of this simulated fragmented IPv6
> packet, and set TTL on it, and send it out (basically I would like
> to do traceroute with it) to isolate a problem.

I found this mildly interesting so I added code to scamper to do this:
traceroute with IPv6 fragment offset != 0.

http://www.wand.net.nz/scamper/scamper-cvs-20110921.tar.gz

I have done a small amount of testing, it seems that some routers (e.g
hops 8 and 9 below) won't send TTL expired to these probes but will
forward them on.  The -o flag specifies the value to place in the
offset field.  At the moment scamper does not do anything with any
fragment reassembly timeout message so it will halt probing after five
unresponsive hops.  The two traces below are fragment and non-fragment
traceroute.

sudo scamper/scamper -I "trace -o 16 -P icmp-paris 2404:138:4002:4000:21e:4fff:fea5:fcfb"
traceroute from 2620:f:1:1301::1 to 2404:138:4002:4000:21e:4fff:fea5:fcfb
 1  2620:f:1:1301::2  0.545 ms
 2  2620:f:0:901::2  0.601 ms
 3  2620:f:0:701::2  3.863 ms
 4  2620:f:0:b01::3  18.063 ms
 5  2001:468:ff:204:8000::2  27.917 ms
 6  2001:468:ff:403::2  41.716 ms
 7  2001:468:ff:305::2  643.131 ms
 8  *
 9  *
10  2404:138:2000::e2  212.816 ms
11  2404:138:0:1::26  214.929 ms
12  2001:df0:4:2::1  214.553 ms
13  2001:df0:4:2::e  215.150 ms
14  *
15  *
16  *
17  *
18  *

sudo scamper/scamper -I "trace -P icmp-paris 2404:138:4002:4000:21e:4fff:fea5:fcfb"
traceroute from 2620:f:1:1301::1 to 2404:138:4002:4000:21e:4fff:fea5:fcfb
 1  2620:f:1:1301::2  0.452 ms
 2  2620:f:0:901::2  0.425 ms
 3  2620:f:0:701::2  3.695 ms
 4  2620:f:0:b01::3  17.594 ms
 5  2001:468:ff:204:8000::2  27.648 ms
 6  2001:468:ff:403::2  41.546 ms
 7  2001:468:ff:305::2  580.418 ms
 8  2001:504:b:20::154  73.698 ms
 9  2404:138:2000::b9  203.024 ms
10  2404:138:2000::e2  212.410 ms
11  2404:138:0:1::26  214.657 ms
12  2001:df0:4:2::1  214.405 ms
13  2001:df0:4:2::e  221.544 ms
14  2404:138:4002:4000:21e:4fff:fea5:fcfb  214.656 ms