[libvirt] [RFC: PATCHv4 00/15] outgoing migration via fd: rather than exec:

[Paolo Bonzini]

On 03/11/2011 05:30 AM, Wen Congyang wrote:
>> >  Yep, makes sense.  I'm double checking whether I reliably closed the
>> >  write end of the socket in all paths, and it may boil down to changing
>> >  the child to_always_  sendmsg even if there is no fd to send.  I'm still
>> >  thinking about it.
>
> Using SOCK_STREAM instead of SOCK_DGRAM to create socketpair can resolve this
> problem. But I don't know why.

At least with AF_INET that would be obvious: with SOCK_STRAM exiting the 
child will close the connection.  With a datagram socket, the parent can 
still wait for other messages to the same UDP port.

I have no idea whether things work the same for AF_UNIX, but apparently 
they do. :)

Paolo