I'm having same issues. Did you find a fix?
echo "0" > /proc/sys/net/ipv4/conf/all/rp_filter
for the actual device you're transmitting on also, not only in the "all" directory. i.e. If your device your using fragroute on is eth1....
echo "0" > /proc/sys/net/ipv4/conf/eth1/rp_filter