net: unable to specify network interface for IPv4 limited/directed broadcast listener.

[gopherbot]

by krolaw:

To listen for Broadcast packets using the net library one omits the interface IP:

l, err := net.ListenPacket("udp4", ":67") // Listen for DHCP Request
Packets

Unfortunately, this listens on all interfaces, rather than allowing the developer to
select the correct one.

Likewise, responses will travel over the main interface, which may differ from where the
client packets originate.

Being able to specify the interface would solve both problems.

Net already supports Multicast Interfaces (with special functions), maybe Broadcast
could be given similar treatment.

[mikioh]

Comment 1:

Sorry, but I have no clue on this issue, leave to others.

[rsc]

Comment 2:

Labels changed: added release-none.

Status changed to Accepted.

[griesemer]

Comment 3:

Labels changed: added repo-main.

[mikioh]

I will close this issue as "working as intended" because basically it's designed to behave like so inside the protocol stack, and we also have x/net/{ipv4,ipv6} packages that provide ancillary information handling including destination IP address on each inbound packet.

Binding an IP network interface to a connection endpoint might be useful if the behavior is consistent, if it's crystal clear how IP routing stuff treats inbound host delivery packets when the network interface has been brought down or there's no routable addresses assigned to the network interface, but that should be another issue.