to send datagrams from an unconnected socket, we used to first block
input, then connect the socket to the sendmsg/sendto destination,
send the datagram, and finally disconnect the socket and unblock
input.
We now use in_pcbconnect_setup() to check if a connect() would have
succeeded, but we never record the connection in the PCB (local
anonymous port allocation is still recorded, though). The result
from in_pcbconnect_setup() authorises the sending of the datagram
and selects the local address and port to use, so we just construct
the header and call ip_output().
Discussed on: -net
Approved by: re
f94a5e8a54