RE: [Qemu-devel] Socket reconnection.

[Krumme, Chris]

Hello Ian,

Since you did not inline your source I will paste in a chunk:


@@ -2030,10 +2036,18 @@ static void tcp_chr_read(void *opaque)
         if (s->listen_fd >= 0) {
             qemu_set_fd_handler(s->listen_fd, tcp_chr_accept, NULL,
chr);
         }
-        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
+        if (!s->reconnect)
+            qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
         closesocket(s->fd);
         s->fd = -1;
-        qemu_chr_event(chr, CHR_EVENT_CLOSED);
+        if (!s->reconnect) {
+            qemu_chr_event(chr, CHR_EVENT_CLOSED);
+        } else {
+            do {
+                sleep(s->reconnect);
+            } while(!qemu_chr_connect_socket(s));
+            qemu_chr_event(chr, CHR_EVENT_RECONNECTED);
+        }
     } else if (size > 0) {
         if (s->do_telnetopt)
             tcp_chr_process_IAC_bytes(chr, s, buf, &size);


Should you be introducing a while sleep loop into Qemu here?

I would think you should be returning 'no data', maybe after trying
once.

Hope this helps.

Chris

 

> -----Original Message-----
> From: 
> address@hidden 
> [mailto:address@hidden
> rg] On Behalf Of Ian Molton
> Sent: Tuesday, December 01, 2009 5:54 AM
> To: Anthony Liguori
> Cc: address@hidden
> Subject: Re: [Qemu-devel] Socket reconnection.
> 
> Anthony Liguori wrote:
> > Ian Molton wrote:
> >> Hi folks,
> >>
> >> I need my source of data for virtio-rng to be reliable - 
> IOW. if the
> >> server dies and comes back up, I want qemu to reconnect 
> and suck down
> >> fresh entropy, rather than hand the rngd process on the guest.
> >>
> >> I'm using the chardev 'socket' type to make the connection 
> to the host.
> >>
> >> Would a patch adding (optional) auto-reconnect (with a 
> back-off delay)
> >> to the socket chardev be acceptable ?
> >>
> >> If not, I'll have to cook up a thread to handle EGD 
> requests, but that
> >> seems perverse...
> >>   
> > 
> > Hrm, I'm not sure.  What are the circumstances that this connection
> > would die?  What happens while the connection is dead?
> 
> The most common would be the entropy gathering daemon being restarted,
> perhaps due to an upgrade. Its hardly a good idea to require all the
> guest VMs to reboot on this occuring. Next most common I 
> guess would be
> the daemon crashing, but again, not something you'd want 
> taking out your
> guest VMs...
> 
> Whilst the connection is down, the guests will potentially starve of
> entropy - but that only means they'll block processes that try to use
> /dev/random if they run out altogether.
> 
> Here are two patches that implement socket reconnection. This first
> cleans up the APIs needed a little  and the second implements 
> the guts.
> 
> If these patches are acceptable, I will repost my 4-patch series which
> also includes the SIZE parameter patch and an updated virtio-rng patch
> that uses the reconnection infrastructure to enhance its reliability.
> 
> -Ian
>