unix: add missing tpacket block (sub)header
This adds the missing tpacket_hdr_v1 struct, which is needed to read
tpacket_block_desc (hdr member, which is a union and therfore defined as
[40]byte). This doesn't modify block_desc so existing implementations
keep working.
Caveat: Although TpacketBDTS has a usec member, this will contain nsec
in case of tpacket v2 or v3.
Change-Id: I772939fe56cf56fc09cf4acf4013b23beb6e03c7
Reviewed-on: https://go-review.googlesource.com/c/sys/+/174861
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>