MFC:

- Use VLAN_TAG_VALUE() not only to read a dot1q tag
    value from an m_tag, but also to set it.  This reduces
    complex code duplication and improves its readability.
  - Fix VLAN_INPUT_TAG() macro, so that it doesn't touch mtag in
    case if memory allocation failed.
  - Remove fourth argument from VLAN_INPUT_TAG(), that was used
    incorrectly in almost all drivers. Indicate failure with
    mbuf value of NULL.

sys/dev/bge/if_bge.c

@@ -2861,8 +2861,11 @@ bge_rxeof(sc)
 		 * If we received a packet with a vlan tag,
 		 * attach that information to the packet.
 		 */
-		if (have_tag)
-			VLAN_INPUT_TAG(ifp, m, vlan_tag, continue);
+		if (have_tag) {
+			VLAN_INPUT_TAG(ifp, m, vlan_tag);
+			if (m == NULL)
+				continue;
+		}
 
 		BGE_UNLOCK(sc);
 		(*ifp->if_input)(ifp, m);

sys/dev/em/if_em.c

@@ -3017,9 +3017,7 @@ em_process_receive_interrupts(struct adapter * adapter, int count)
                                 if (current_desc->status & E1000_RXD_STAT_VP)
 					VLAN_INPUT_TAG(ifp, adapter->fmp,
 					    (le16toh(current_desc->special) &
-					    E1000_RXD_SPC_VLAN_MASK),
-					    adapter->fmp = NULL);
-
+					    E1000_RXD_SPC_VLAN_MASK));
 				m = adapter->fmp;
 				adapter->fmp = NULL;
 				adapter->lmp = NULL;

sys/dev/ixgb/if_ixgb.c

@@ -2152,8 +2152,7 @@ ixgb_process_receive_interrupts(struct adapter * adapter, int count)
 						      adapter->fmp);
 				if (current_desc->status & IXGB_RX_DESC_STATUS_VP)
 					VLAN_INPUT_TAG(ifp, adapter->fmp,
-						       current_desc->special,
-						       adapter->fmp = NULL);
+						       current_desc->special);
 
 				if (adapter->fmp != NULL) {
 					IXGB_UNLOCK(adapter);

sys/dev/nge/if_nge.c

@@ -1229,7 +1229,9 @@ nge_rxeof(sc)
 		 */
 		if (extsts & NGE_RXEXTSTS_VLANPKT) {
 			VLAN_INPUT_TAG(ifp, m,
-			    ntohs(extsts & NGE_RXEXTSTS_VTCI), continue);
+			    ntohs(extsts & NGE_RXEXTSTS_VTCI));
+			if (m == NULL)
+				continue;
 		}
 		NGE_UNLOCK(sc);
 		(*ifp->if_input)(ifp, m);

sys/dev/re/if_re.c

@@ -1670,9 +1670,12 @@ re_rxeof(sc)
 			}
 		}
 
-		if (rxvlan & RL_RDESC_VLANCTL_TAG)
+		if (rxvlan & RL_RDESC_VLANCTL_TAG) {
 			VLAN_INPUT_TAG(ifp, m,
-			    ntohs((rxvlan & RL_RDESC_VLANCTL_DATA)), continue);
+			    ntohs((rxvlan & RL_RDESC_VLANCTL_DATA)));
+			if (m == NULL)
+				continue;
+		}
 		RL_UNLOCK(sc);
 		(*ifp->if_input)(ifp, m);
 		RL_LOCK(sc);

sys/dev/txp/if_txp.c

@@ -766,8 +766,9 @@ txp_rx_reclaim(sc, r)
 		}
 
 		if (rxd->rx_stat & RX_STAT_VLAN) {
-			VLAN_INPUT_TAG(ifp,
-				m, htons(rxd->rx_vlan >> 16), goto next);
+			VLAN_INPUT_TAG(ifp, m, htons(rxd->rx_vlan >> 16));
+			if (m == NULL)
+				goto next;
 		}
 
 		TXP_UNLOCK(sc);

sys/dev/vge/if_vge.c

@@ -1490,9 +1490,12 @@ vge_rxeof(sc)
 			}
 		}
 
-		if (rxstat & VGE_RDSTS_VTAG)
+		if (rxstat & VGE_RDSTS_VTAG) {
 			VLAN_INPUT_TAG(ifp, m,
-			    ntohs((rxctl & VGE_RDCTL_VLANID)), continue);
+			    ntohs((rxctl & VGE_RDCTL_VLANID)));
+			if (m == NULL)
+				continue;
+		}
 
 		VGE_UNLOCK(sc);
 		(*ifp->if_input)(ifp, m);

sys/net/if_vlan.c

@@ -509,7 +509,7 @@ vlan_start(struct ifnet *ifp)
 				m_freem(m);
 				continue;
 			}
-			*(u_int*)(mtag + 1) = ifv->ifv_tag;
+			VLAN_TAG_VALUE(mtag) = ifv->ifv_tag;
 			m_tag_prepend(m, mtag);
 			m->m_flags |= M_VLANTAG;
 		} else {

sys/net/if_vlan_var.h

@@ -96,24 +96,30 @@ struct	vlanreq {
 #define	MTAG_VLAN	1035328035
 #define	MTAG_VLAN_TAG	0		/* tag of VLAN interface */
 
-#define	VLAN_INPUT_TAG(_ifp, _m, _t, _errcase) do {		\
+/*
+ * This macro must expand to a lvalue so that it can be used
+ * to set a tag with a simple assignment.
+ */
+#define	VLAN_TAG_VALUE(_mt)	(*(u_int *)((_mt) + 1))
+
+#define	VLAN_INPUT_TAG(_ifp, _m, _t) do {			\
 	struct m_tag *mtag;					\
 	mtag = m_tag_alloc(MTAG_VLAN, MTAG_VLAN_TAG,		\
 			   sizeof (u_int), M_NOWAIT);		\
-	if (mtag == NULL) {					\
+	if (mtag != NULL) {					\
+		VLAN_TAG_VALUE(mtag) = (_t);			\
+		m_tag_prepend((_m), mtag);			\
+		(_m)->m_flags |= M_VLANTAG;			\
+	} else {						\
 		(_ifp)->if_ierrors++;				\
 		m_freem(_m);					\
-		_errcase;					\
+		_m = NULL;					\
 	}							\
-	*(u_int *)(mtag+1) = (_t);				\
-	m_tag_prepend((_m), mtag);				\
-	(_m)->m_flags |= M_VLANTAG;				\
 } while (0)
 
 #define	VLAN_OUTPUT_TAG(_ifp, _m)				\
 	((_m)->m_flags & M_VLANTAG ?				\
 		m_tag_locate((_m), MTAG_VLAN, MTAG_VLAN_TAG, NULL) : NULL)
-#define	VLAN_TAG_VALUE(_mt)	(*(u_int *)((_mt)+1))
 #endif /* _KERNEL */
 
 #endif /* _NET_IF_VLAN_VAR_H_ */

sys/net80211/ieee80211_input.c

@@ -710,8 +710,9 @@ ieee80211_deliver_data(struct ieee80211com *ic,
 	if (m != NULL) {
 		if (ni->ni_vlan != 0) {
 			/* attach vlan tag */
-			/* XXX goto err? */
-			VLAN_INPUT_TAG(ifp, m, ni->ni_vlan, goto out);
+			VLAN_INPUT_TAG(ifp, m, ni->ni_vlan);
+			if (m == NULL)
+				goto out;	/* XXX goto err? */
 		}
 		(*ifp->if_input)(ifp, m);
 	}

sys/pci/if_ti.c

@@ -2532,8 +2532,11 @@ ti_rxeof(sc)
 		 * If we received a packet with a vlan tag,
 		 * tag it before passing the packet upward.
 		 */
-		if (have_tag)
-			VLAN_INPUT_TAG(ifp, m, vlan_tag, continue);
+		if (have_tag) {
+			VLAN_INPUT_TAG(ifp, m, vlan_tag);
+			if (m == NULL)
+				continue;
+		}
 		TI_UNLOCK(sc);
 		(*ifp->if_input)(ifp, m);
 		TI_LOCK(sc);