[libvirt] [PATCH v3 3/9] rpc: set listen backlog on FDs as well as on other sockets

[Daniel P. Berrange]

On Wed, Aug 13, 2014 at 05:05:26PM +0200, Martin Kletzander wrote:
> On Wed, Aug 13, 2014 at 03:54:02PM +0100, Daniel P. Berrange wrote:
> >On Wed, Jul 23, 2014 at 04:27:07PM +0200, Martin Kletzander wrote:
> >>Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> >>---
> >> src/locking/lock_daemon.c     | 2 +-
> >> src/rpc/virnetserverservice.c | 5 +++++
> >> src/rpc/virnetserverservice.h | 1 +
> >> 3 files changed, 7 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/src/locking/lock_daemon.c b/src/locking/lock_daemon.c
> >>index e9219d5..02d77e3 100644
> >>--- a/src/locking/lock_daemon.c
> >>+++ b/src/locking/lock_daemon.c
> >>@@ -614,7 +614,7 @@ virLockDaemonSetupNetworkingSystemD(virNetServerPtr srv)
> >> #if WITH_GNUTLS
> >>                                          NULL,
> >> #endif
> >>-                                         false, 1)))
> >>+                                         false, 0, 1)))
> >>         return -1;
> >>
> >>     if (virNetServerAddService(srv, svc, NULL) < 0) {
> >>diff --git a/src/rpc/virnetserverservice.c b/src/rpc/virnetserverservice.c
> >>index e85889b..fea05c3 100644
> >>--- a/src/rpc/virnetserverservice.c
> >>+++ b/src/rpc/virnetserverservice.c
> >>@@ -133,6 +133,7 @@ virNetServerServiceNewFDOrUNIX(const char *path,
> >>                                         tls,
> >> #endif
> >>                                         readonly,
> >>+                                        max_queued_clients,
> >>                                         nrequests_client_max);
> >>     }
> >> }
> >>@@ -265,6 +266,7 @@ virNetServerServicePtr virNetServerServiceNewFD(int fd,
> >>                                                 virNetTLSContextPtr tls,
> >> #endif
> >>                                                 bool readonly,
> >>+                                                size_t max_queued_clients,
> >>                                                 size_t nrequests_client_max)
> >> {
> >>     virNetServerServicePtr svc;
> >>@@ -292,6 +294,9 @@ virNetServerServicePtr virNetServerServiceNewFD(int fd,
> >>         goto error;
> >>
> >>     for (i = 0; i < svc->nsocks; i++) {
> >>+        if (virNetSocketListen(svc->socks[i], max_queued_clients) < 0)
> >>+            goto error;
> >
> >Hmm, systemd should have already called listen() on the socket FD it
> >passes to us. I wonder if it is better than we do the same when
> >auto-spawning libvirtd passing it a listening socket. You kind of
> >need to listen() to avoid a race condition I believe when spawning
> >libvirtd twice. eg if libvirt.so calls listen() and it fails then
> >we know there's another libvirtd in the process of being started
> >on that socket, so we can go back to trying to connect() until it
> >succeeeds.
> >
> 
> Yes, it does, but we call listen() here to adjust the backlog value.
> It still works, no clients get disconnected, but kernel knows what
> backlog we want from now on.  Because of this and other settings that
> must be done by systemd (or virsh), there is a new comment in the
> configuration file saying that systemd should be set the same way
> libvirt is (socket permissions, backlog, etc.)

ACK, and it was actually 'bind' I was getting confused with which
fails if already previously invoked.



Regards,
Daniel
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