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

[Laine Stump]

On 03/11/2011 05:15 AM, Paolo Bonzini wrote:
> 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. :)

Not only does this fix the problem, the other uses of socketpair() in 
libvirt also use SOCKET_STREAM instead of SOCKET_DGRAM.

So I'd say this is an acceptable fix.