message ``sendto failed: Invalid argument''

[Peter Koch]

Not sure whether this is a bug report or an RFE, so I'll give it a try here.
In my NSD 2.3.3's logs there are quite a couple of entries like

[1138286782] nsd[42]: error: sendto failed: Invalid argument

They originate from server.c and the reason usually is an attempt to send
a response to UDP port 0. Source port 0 is legal but it means something
like "I do not care what the response is", so it doesn't make much sense
for DNS queries. I could filter those packets, of course.
Then, the log message is not too instructive due to lack of detail.
It could be something else but a dst port 0 sendto() attempt and if
a particular querier appears too often it might be intersting as well.
So, nsd could (silently) ignore DNS packets with src port 0 or log the
error with more detail or both. Opinions?

-Peter