Lock down the network interface queues. The queue mutex must be obtained

before adding/removing packets from the queue.  Also, the if_obytes and
if_omcasts fields should only be manipulated under protection of the mutex.

IF_ENQUEUE, IF_PREPEND, and IF_DEQUEUE perform all necessary locking on
the queue.  An IF_LOCK macro is provided, as well as the old (mutex-less)
versions of the macros in the form _IF_ENQUEUE, _IF_QFULL, for code which
needs them, but their use is discouraged.

Two new macros are introduced: IF_DRAIN() to drain a queue, and IF_HANDOFF,
which takes care of locking/enqueue, and also statistics updating/start
if necessary.

1 files changed, 3 insertions, 18 deletions

diff --git a/sys/net/if_atmsubr.c b/sys/net/if_atmsubr.c
index 3c04db5..4d71d57 100644
--- a/sys/net/if_atmsubr.c
+++ b/sys/net/if_atmsubr.c
@@ -203,17 +203,8 @@ atm_output(ifp, m0, dst, rt0)
 	 * Queue message on interface, and start output if interface
 	 * not yet active.
 	 */
-	s = splimp();
-	if (IF_QFULL(&ifp->if_snd)) {
-		IF_DROP(&ifp->if_snd);
-		splx(s);
-		senderr(ENOBUFS);
-	}
-	ifp->if_obytes += m->m_pkthdr.len;
-	IF_ENQUEUE(&ifp->if_snd, m);
-	if ((ifp->if_flags & IFF_OACTIVE) == 0)
-		(*ifp->if_start)(ifp);
-	splx(s);
+	if (! IF_HANDOFF(&ifp->if_snd, m, ifp))
+		return (ENOBUFS);
 	return (error);
 
 bad:
@@ -301,13 +292,7 @@ atm_input(ifp, ah, m, rxhand)
 		}
 	}
 
-	s = splimp();
-	if (IF_QFULL(inq)) {
-		IF_DROP(inq);
-		m_freem(m);
-	} else
-		IF_ENQUEUE(inq, m);
-	splx(s);
+	(void) IF_HANDOFF(inq, m, NULL);
 }
 
 /*