We don't handle defragmentation of IP packets
coming from the tap side,
and we're unlikely to any time soon (with our large MTU, it's not useful
for practical use cases). Currently, however, we simply ignore the
fragmentation flags and treat fragments as though they were whole IP
packets. This isn't ideal and can lead to rather cryptic behaviour if we
do receive IP fragments.
Change the code to explicitly drop fragmented packets, and print a rate
limited warning if we do encounter them.
Link:
https://bugs.passt.top/show_bug.cgi?id=62
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>