UDP packets can be built as:
val p = ether / ipv6 / udp / data
val p2 = ether / ipv4 / udp / data
val p3 = ether / ipv4 / udp / ipv4 / udp / data
This also gets rid of Icmp6Pkt in favor of a function call that
calculates the checksum over an L4 packet.
This does add a bit of duplication: the build() function for RA and NA
packets is identical, and UdpPkt#build() is not far off. However, subtle
differences in L4 packet format (namely the checksum and length
positions) make generalizing this code difficult. This is possible by
passing the checksum position, proto byte, and adding an abstract
function that fills in the L4 length field before performing checksum
calculation. However, this complexity is likely not worth it. If the
repetition becomes obvious once more protocols (such as ICMPv4/6 echo,
etc.) are added, this decision will be revisited.
Test: TH
Flag: EXEMPT mainline
Bug: 1000001
Change-Id: Ia78792418f29a3be091ebdc9bb2c26e45da9f2b1
328cfb5051