Misalignment, MIPS, and ip_hdr(skb)->version

[Dave Taht]

The openwrt tree has long contained a set of patches that correct for
unaligned issues throughout the linux network stack.

https://git.lede-project.org/?p=openwrt/source.git;a=blob;f=target/linux/ar71xx/patches-4.4/910-unaligned_access_hacks.patch;h=b4b749e4b9c02a74a9f712a2740d63e554de5c64;hb=ee53a240ac902dc83209008a2671e7fdcf55957a

unaligned access traps in the packet processing path on certain versions of
the mips architecture is horrifically bad. I had kind of hoped these
patches in some form would have made it upstream by now. (or the
arches that have the issue retired, I think it's mostly just mips24k)