From: Jan Klemkow <jan@openbsd.org>
Subject: vport(4): Use VLAN HW Tagging
To: tech@openbsd.org
Date: Mon, 23 Jun 2025 17:35:48 +0200

Hi,

the following diff introduces VLAN offload to vport(4).  veb(4) just
calls vlan_inject() if the underlying send interface it not capable of
hw tagging.  So, we don't call it in most cases and avoid an mget() for
every packet.

ok?

bye,
Jan

Index: net/if_veb.c
===================================================================
RCS file: /cvs/src/sys/net/if_veb.c,v
diff -u -p -r1.37 if_veb.c
--- net/if_veb.c	2 Mar 2025 21:28:32 -0000	1.37
+++ net/if_veb.c	23 Jun 2025 15:06:54 -0000
@@ -927,6 +927,27 @@ veb_ipsec_out(struct ifnet *ifp0, struct
 }
 #endif /* IPSEC */
 
+static struct mbuf *
+veb_offload(struct ifnet *ifp, struct mbuf *m)
+{
+#if NVLAN > 0
+	if (ISSET(m->m_flags, M_VLANTAG) &&
+	    !ISSET(ifp->if_capabilities, IFCAP_VLAN_HWTAGGING)) {
+		/*
+		 * If the underlying interface has no VLAN hardware tagging
+		 * support, inject one in software.
+		 */
+		m = vlan_inject(m, ETHERTYPE_VLAN, m->m_pkthdr.ether_vtag);
+		if (m == NULL) {
+			counters_inc(ifp->if_counters, ifc_ierrors);
+			return NULL;
+		}
+	}
+#endif
+
+	return m;
+}
+
 static void
 veb_broadcast(struct veb_softc *sc, struct veb_port *rp, struct mbuf *m0,
     uint64_t src, uint64_t dst, struct netstack *ns)
@@ -996,6 +1017,9 @@ veb_broadcast(struct veb_softc *sc, stru
 		if (veb_rule_filter(tp, VEB_RULE_LIST_OUT, m0, src, dst))
 			continue;
 
+		if ((m0 = veb_offload(ifp0, m0)) == NULL)
+			goto done;
+
 		m = m_dup_pkt(m0, max_linkhdr + ETHER_ALIGN, M_NOWAIT);
 		if (m == NULL) {
 			/* XXX count error? */
@@ -1048,6 +1072,9 @@ veb_transmit(struct veb_softc *sc, struc
 	counters_pkt(ifp->if_counters, ifc_opackets, ifc_obytes,
 	    m->m_pkthdr.len);
 
+	if ((m = veb_offload(ifp0, m)) == NULL)
+		goto drop;
+
 	(*tp->p_enqueue)(ifp0, m); /* XXX count error */
 
 	return (NULL);
@@ -1105,20 +1132,6 @@ veb_port_input(struct ifnet *ifp0, struc
 		}
 	}
 
-#if NVLAN > 0
-	/*
-	 * If the underlying interface removed the VLAN header itself,
-	 * add it back.
-	 */
-	if (ISSET(m->m_flags, M_VLANTAG)) {
-		m = vlan_inject(m, ETHERTYPE_VLAN, m->m_pkthdr.ether_vtag);
-		if (m == NULL) {
-			counters_inc(ifp->if_counters, ifc_ierrors);
-			goto drop;
-		}
-	}
-#endif
-
 	counters_pkt(ifp->if_counters, ifc_ipackets, ifc_ibytes,
 	    m->m_pkthdr.len);
 
@@ -2349,6 +2362,7 @@ vport_clone_create(struct if_clone *ifc,
 	ifp->if_qstart = vport_start;
 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
 	ifp->if_xflags = IFXF_CLONED | IFXF_MPSAFE;
+	ifp->if_capabilities = IFCAP_VLAN_HWTAGGING;
 	ether_fakeaddr(ifp);
 
 	if_counters_alloc(ifp);