This value gets clobbered after the netlink recvmsg. It was giving me a
bogus address family (234), which caused the call to getInterfaceByName
to fail:
Could not find interface wlan0 which was specified by -e
This seems to have been exposed by r29754. Specifying a source address
that is not on any actual route seems to result in a netlink query
result with 0 entries, and the changed value of rtm_family. (The fact
that there are no routes returned is not a problem, because we bail out
early when -e is given, now that getInterfaceByName works again.)