gnu_linux: MMAP cannot handle properly VLANs (including MTU)

[msune]

There seems to be two different issues with PF_PACKET TX/RX rings:

• There is no proper way to recover the ether_type of the original frame from the struct tpacket2_hdr, so only 0x8100 can be assumed
• TX ring does not handle properly MTU with VLANs; e.g. with an MTU of 1500, only up to 1514 packets are accepted instead of 1518.

[msune]

Marking as won't fix, as apparently there is no proper way of doing it in PACKET_MMAP. Leaving issue open for reference.

[msune]

More information here: http://pdos.csail.mit.edu/pipermail/click/2007-February/005675.html