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, 10 insertions, 14 deletions

diff --git a/sys/dev/ppbus/if_plip.c b/sys/dev/ppbus/if_plip.c
index 2410afe..ee379fe 100644
--- a/sys/dev/ppbus/if_plip.c
+++ b/sys/dev/ppbus/if_plip.c
@@ -513,11 +513,6 @@ lp_intr (void *arg)
 
 	    sc->sc_iferrs = 0;
 
-	    if (IF_QFULL(&ipintrq)) {
-	        lprintf("DROP");
-	        IF_DROP(&ipintrq);
-		goto done;
-	    }
 	    len -= CLPIPHDRLEN;
 	    sc->sc_if.if_ipackets++;
 	    sc->sc_if.if_ibytes += len;
@@ -525,8 +520,11 @@ lp_intr (void *arg)
 	    if (top) {
 		if (sc->sc_if.if_bpf)
 		    lptap(&sc->sc_if, top);
-	        IF_ENQUEUE(&ipintrq, top);
-	        schednetisr(NETISR_IP);
+                if (! IF_HANDOFF(&ipintrq, top, NULL)) {
+	            lprintf("DROP");
+                } else {
+	            schednetisr(NETISR_IP);
+	        }
 	    }
 	    goto done;
 	}
@@ -564,11 +562,6 @@ lp_intr (void *arg)
 
 	    sc->sc_iferrs = 0;
 
-	    if (IF_QFULL(&ipintrq)) {
-		lprintf("DROP");
-		IF_DROP(&ipintrq);
-		goto done;
-	    }
 	    len -= LPIPHDRLEN;
 	    sc->sc_if.if_ipackets++;
 	    sc->sc_if.if_ibytes += len;
@@ -576,8 +569,11 @@ lp_intr (void *arg)
 	    if (top) {
 		if (sc->sc_if.if_bpf)
 		    lptap(&sc->sc_if, top);
-		IF_ENQUEUE(&ipintrq, top);
-		schednetisr(NETISR_IP);
+                if (! IF_HANDOFF(&ipintrq, top, NULL))  {
+		    lprintf("DROP");
+                } else {
+		    schednetisr(NETISR_IP);
+	        }
 	    }
 	}
 	goto done;