- After adding tunnel headers, but before segmentation, packet length can be
more than 65535. So, pkt_len() should return an integer rather than a short.
Once segmentation happens, we anyway update the outer ip header length. So,
whatever is updated in between (during the course of ip header addition),
really doesn't matter.

- Mirror bug: If the mirrored packet is TCP and is marked for GSO, we carry
that gso type to mirror packet which is in-fact a UDP packet. So, correct the
gso type, if the type is not what is expected for UDP packets