[lltable] Add per-family lltable getters.

Introduce a new function, lltable_get(), to retrieve lltable pointer
 for the specified interface and family.
Use it to avoid all-iftable list traversal when adding or deleting
 ARP/ND records.

Differential Revision: https://reviews.freebsd.org/D33660
MFC after:	2 weeks

sys/net/if_llatbl.c

@@ -712,6 +712,22 @@ lltable_unlink(struct lltable *llt)
 
 }
 
+/*
+ * Gets interface @ifp lltable for the specified @family
+ */
+struct lltable *
+lltable_get(struct ifnet *ifp, int family)
+{
+	switch (family) {
+	case AF_INET:
+		return (in_lltable_get(ifp));
+	case AF_INET6:
+		return (in6_lltable_get(ifp));
+	}
+
+	return (NULL);
+}
+
 /*
  * External methods used by lltable consumers
  */
@@ -823,14 +839,8 @@ lla_rt_output(struct rt_msghdr *rtm, struct rt_addrinfo *info)
 		return EINVAL;
 	}
 
-	/* XXX linked list may be too expensive */
+	llt = lltable_get(ifp, dst->sa_family);
-	LLTABLE_LIST_RLOCK();
+
-	SLIST_FOREACH(llt, &V_lltables, llt_link) {
-		if (llt->llt_af == dst->sa_family &&
-		    llt->llt_ifp == ifp)
-			break;
-	}
-	LLTABLE_LIST_RUNLOCK();
 	if (llt == NULL)
 		return (ESRCH);
 

sys/net/if_llatbl.h

@@ -222,6 +222,10 @@ void		lltable_prefix_free(int, struct sockaddr *,
 		    struct sockaddr *, u_int);
 int		lltable_sysctl_dumparp(int, struct sysctl_req *);
 
+struct lltable *in_lltable_get(struct ifnet *ifp);
+struct lltable *in6_lltable_get(struct ifnet *ifp);
+struct lltable *lltable_get(struct ifnet *ifp, int family);
+
 size_t		llentry_free(struct llentry *);
 
 /* helper functions */

sys/netinet/in.c

@@ -1704,6 +1704,17 @@ in_lltattach(struct ifnet *ifp)
 	return (llt);
 }
 
+struct lltable *
+in_lltable_get(struct ifnet *ifp)
+{
+	struct lltable *llt = NULL;
+
+	void *afdata_ptr = ifp->if_afdata[AF_INET];
+	if (afdata_ptr != NULL)
+		llt = ((struct in_ifinfo *)afdata_ptr)->ii_llt;
+	return (llt);
+}
+
 void *
 in_domifattach(struct ifnet *ifp)
 {

sys/netinet6/in6.c

@@ -2483,6 +2483,17 @@ in6_lltattach(struct ifnet *ifp)
 	return (llt);
 }
 
+struct lltable *
+in6_lltable_get(struct ifnet *ifp)
+{
+	struct lltable *llt = NULL;
+
+	void *afdata_ptr = ifp->if_afdata[AF_INET6];
+	if (afdata_ptr != NULL)
+		llt = ((struct in6_ifextra *)afdata_ptr)->lltable;
+	return (llt);
+}
+
 void *
 in6_domifattach(struct ifnet *ifp)
 {