James Tucker 146f51ce76 net/packet: fix filtering of short IPv4 fragments
The fragment offset is an 8 byte offset rather than a byte offset, so
the short packet limit is now in fragment block size in order to compare
with the offset value.

The packet flags are in the first 3 bits of the flags/frags byte, and
so after conversion to a uint16 little endian value they are at the
start, not the end of the value - the mask for extracting "more
fragments" is adjusted to match this byte.

Extremely short fragments less than 80 bytes are dropped, but fragments
over 80 bytes are now accepted.

Fixes #5727

Signed-off-by: James Tucker <james@tailscale.com>
2022-09-23 10:43:28 -07:00
..
2022-08-02 10:08:05 -07:00