Xen devel - Oct 2005 - patch: event channel fixups

Hello all,

Here''s a suggested patch for xen/common/event_channel.c

Summary:
Allows interdomain channels to bind DOMID_SELF to DOMID_SELF.  A couple
of quick fixes made this work, since support for loopback channels is
already there.
 
Stops a local port leak when an interdomain channel is rejected at the
remote end.
 
Thanks,
-steve

Signed-off-by: Steve King <steven.r.king@intel.com>


diff -r 446aa56ca4fe xen/common/event_channel.c
--- a/xen/common/event_channel.c	Mon Oct 17 12:50:28 2005
+++ b/xen/common/event_channel.c	Mon Oct 17 16:12:21 2005
@@ -89,7 +89,10 @@
     chn = evtchn_from_port(d, port);
 
     chn->state = ECS_UNBOUND;
-    chn->u.unbound.remote_domid = alloc->remote_dom;
+    if( alloc->remote_dom == DOMID_SELF )
+        chn->u.unbound.remote_domid = current->domain->domain_id;
+    else
+        chn->u.unbound.remote_domid = alloc->remote_dom;
 
     alloc->port = port;
 
@@ -108,8 +111,14 @@
     struct domain *ld = current->domain, *rd;
     int            lport, rport = bind->remote_port;
     long           rc = 0;
-
-    if ( (rd = find_domain_by_id(bind->remote_dom)) == NULL )
+    domid_t        rdom;    
+
+    if( bind->remote_dom == DOMID_SELF )
+        rdom = current->domain->domain_id;
+    else
+        rdom = bind->remote_dom;
+
+    if ( (rd = find_domain_by_id(rdom)) == NULL )
         return -ESRCH;
 
     /* Avoid deadlock by first acquiring lock of domain with smaller
id. */
@@ -125,16 +134,21 @@
         spin_lock(&ld->evtchn_lock);
     }
 
-    if ( (lport = get_free_port(ld)) < 0 )
-        ERROR_EXIT(lport);
-    lchn = evtchn_from_port(ld, lport);
-
+    /*
+     * Failure paths do not deallocate the local port,
+     * so validate before allocating.
+     */
     if ( !port_is_valid(rd, rport) )
         ERROR_EXIT(-EINVAL);
     rchn = evtchn_from_port(rd, rport);
     if ( (rchn->state != ECS_UNBOUND) ||
          (rchn->u.unbound.remote_domid != ld->domain_id) )
         ERROR_EXIT(-EINVAL);
+
+    if ( (lport = get_free_port(ld)) < 0 )
+        ERROR_EXIT(lport);
+
+    lchn = evtchn_from_port(ld, lport);
 
     lchn->u.interdomain.remote_dom  = rd;
     lchn->u.interdomain.remote_port = (u16)rport;



 

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On 18 Oct 2005, at 00:39, King, Steven R wrote:
> Summary:
> Allows interdomain channels to bind DOMID_SELF to DOMID_SELF.  A couple
> of quick fixes made this work, since support for loopback channels is
> already there.
>
> Stops a local port leak when an interdomain channel is rejected at the
> remote end.
I took all except the fix for the port leak, since the leak doesn''t 
exist (get_free_port() doesn''t actually allocate a port, it just 
returns a free port that is allocated later by the caller changing 
chn->state).

  -- Keir


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