IP_PKTINFO needs to be sent, not just recieved

[wbl]

One of the common uses of IP_PKTINFO is with a UDP port that receives packets from many addresses to know which port to send the the result to. Sadly IP_PKTINFO is only a ControlMessageOwned, not a ControlMessage and the same is true for IPv6. Every ControlMessageOwned should probably be a ControlMessage as well if it can be used on transmit.

[asomers]

I didn't realize that message could be used for transmitting to. Patches welcome!