Fix the handling of IPv6 On-Link Redirects.

On receipt of a redirect message, install an interface route for the
redirected destination.  On removal of the corresponding Neighbor Cache
entry, remove the interface route.

This requires changes in rtredirect_fib() to cope with an AF_LINK
address for the gateway and with the absence of RTF_GATEWAY.

This fixes the "Redirected On-Link" test cases in the Tahi IPv6 Ready Logo
Phase 2 test suite.

Unrelated to the above, fix a recursion on the radix node head lock
triggered by the Tahi Redirected to Alternate Router test cases.

When I first wrote this patch in October 2012, all Section 2
(Neighbor Discovery) test cases passed on 10-CURRENT, 9-STABLE,
and 8-STABLE.  cem@ recently rebased the 10.x patch onto head and reported
that it passes Tahi.  (Thanks!)

These other test cases also passed in 2012:

* the RTF_MODIFIED case, with IPv4 and IPv6 (using a
  RTF_HOST|RTF_GATEWAY route for the destination)

* the redirected-to-self case, with IPv4 and IPv6

* a valid IPv4 redirect

All testing in 2012 was done with WITNESS and INVARIANTS.

Tested by:    EMC / Isilon Storage Division via Conrad Meyer (cem) in 2015,
              Mark Kelley <mark_kelley@dell.com> in 2012,
              TC Telkamp <terence_telkamp@dell.com> in 2012
PR:           152791
Reviewed by:  melifaro (current rev), bz (earlier rev)
Approved by:  kib (mentor)
MFC after:    1 month
Relnotes:     yes
Sponsored by: Dell Inc.
Differential Revision: https://reviews.freebsd.org/D3602

sys/net/if_llatbl.h

@@ -183,6 +183,7 @@ MALLOC_DECLARE(M_LLTABLE);
 #define	LLE_STATIC	0x0002	/* entry is static */
 #define	LLE_IFADDR	0x0004	/* entry is interface addr */
 #define	LLE_VALID	0x0008	/* ll_addr is valid */
+#define	LLE_REDIRECT	0x0010	/* installed by redirect; has host rtentry */
 #define	LLE_PUB		0x0020	/* publish entry ??? */
 #define	LLE_LINKED	0x0040	/* linked to lookup structure */
 /* LLE request flags */

sys/net/route.c

@@ -584,13 +584,20 @@ rtredirect_fib(struct sockaddr *dst,
 	 * we have a routing loop, perhaps as a result of an interface
 	 * going down recently.
 	 */
-	if (!(flags & RTF_DONE) && rt &&
-	     (!sa_equal(src, rt->rt_gateway) || rt->rt_ifa != ifa))
+	if (!(flags & RTF_DONE) && rt) {
+		if (!sa_equal(src, rt->rt_gateway)) {
 			error = EINVAL;
-	else if (ifa_ifwithaddr_check(gateway))
-		error = EHOSTUNREACH;
-	if (error)
 			goto done;
+		}
+		if (rt->rt_ifa != ifa && ifa->ifa_addr->sa_family != AF_LINK) {
+			error = EINVAL;
+			goto done;
+		}
+	}
+	if ((flags & RTF_GATEWAY) && ifa_ifwithaddr_check(gateway)) {
+		error = EHOSTUNREACH;
+		goto done;
+	}
 	/*
 	 * Create a new entry if we just got back a wildcard entry
 	 * or the lookup failed.  This is necessary for hosts
@@ -613,7 +620,7 @@ rtredirect_fib(struct sockaddr *dst,
 			rt0 = rt;
 			rt = NULL;
 		
-			flags |=  RTF_GATEWAY | RTF_DYNAMIC;
+			flags |= RTF_DYNAMIC;
 			bzero((caddr_t)&info, sizeof(info));
 			info.rti_info[RTAX_DST] = dst;
 			info.rti_info[RTAX_GATEWAY] = gateway;
@@ -640,6 +647,8 @@ rtredirect_fib(struct sockaddr *dst,
 			 * Smash the current notion of the gateway to
 			 * this destination.  Should check about netmask!!!
 			 */
+			if ((flags & RTF_GATEWAY) == 0)
+				rt->rt_flags &= ~RTF_GATEWAY;
 			rt->rt_flags |= RTF_MODIFIED;
 			flags |= RTF_MODIFIED;
 			stat = &V_rtstat.rts_newgateway;
@@ -653,6 +662,7 @@ rtredirect_fib(struct sockaddr *dst,
 			gwrt = rtalloc1(gateway, 1, RTF_RNH_LOCKED);
 			RADIX_NODE_HEAD_UNLOCK(rnh);
 			EVENTHANDLER_INVOKE(route_redirect_event, rt, gwrt, dst);
+			if (gwrt)
 				RTFREE_LOCKED(gwrt);
 		}
 	} else

sys/netinet6/icmp6.c

@@ -2434,27 +2434,39 @@ icmp6_redirect_input(struct mbuf *m, int off)
 	nd6_cache_lladdr(ifp, &redtgt6, lladdr, lladdrlen, ND_REDIRECT,
 	    is_onlink ? ND_REDIRECT_ONLINK : ND_REDIRECT_ROUTER);
 
-	if (!is_onlink) {	/* better router case.  perform rtredirect. */
-		/* perform rtredirect */
+	/*
+	 * Install a gateway route in the better-router case or an interface
+	 * route in the on-link-destination case.
+	 */
+	{
 		struct sockaddr_in6 sdst;
 		struct sockaddr_in6 sgw;
 		struct sockaddr_in6 ssrc;
+		struct sockaddr *gw;
+		int rt_flags;
 		u_int fibnum;
 
 		bzero(&sdst, sizeof(sdst));
-		bzero(&sgw, sizeof(sgw));
 		bzero(&ssrc, sizeof(ssrc));
-		sdst.sin6_family = sgw.sin6_family = ssrc.sin6_family = AF_INET6;
-		sdst.sin6_len = sgw.sin6_len = ssrc.sin6_len =
-			sizeof(struct sockaddr_in6);
-		bcopy(&redtgt6, &sgw.sin6_addr, sizeof(struct in6_addr));
+		sdst.sin6_family = ssrc.sin6_family = AF_INET6;
+		sdst.sin6_len = ssrc.sin6_len = sizeof(struct sockaddr_in6);
 		bcopy(&reddst6, &sdst.sin6_addr, sizeof(struct in6_addr));
 		bcopy(&src6, &ssrc.sin6_addr, sizeof(struct in6_addr));
+		rt_flags = RTF_HOST;
+		if (is_router) {
+			bzero(&sgw, sizeof(sgw));
+			sgw.sin6_family = AF_INET6;
+			sgw.sin6_len = sizeof(struct sockaddr_in6);
+			bcopy(&redtgt6, &sgw.sin6_addr,
+				sizeof(struct in6_addr));
+			gw = (struct sockaddr *)&sgw;
+			rt_flags |= RTF_GATEWAY;
+		} else
+			gw = ifp->if_addr->ifa_addr;
 		for (fibnum = 0; fibnum < rt_numfibs; fibnum++)
-			in6_rtredirect((struct sockaddr *)&sdst,
-			    (struct sockaddr *)&sgw, (struct sockaddr *)NULL,
-			    RTF_GATEWAY | RTF_HOST, (struct sockaddr *)&ssrc,
-			    fibnum);
+			in6_rtredirect((struct sockaddr *)&sdst, gw,
+			    (struct sockaddr *)NULL, rt_flags,
+			    (struct sockaddr *)&ssrc, fibnum);
 	}
 	/* finally update cached route in each socket via pfctlinput */
     {

sys/netinet6/nd6.c

@@ -132,6 +132,7 @@ static void nd6_setmtu0(struct ifnet *, struct nd_ifinfo *);
 static void nd6_slowtimo(void *);
 static int regen_tmpaddr(struct in6_ifaddr *);
 static struct llentry *nd6_free(struct llentry *, int);
+static void nd6_free_redirect(const struct llentry *);
 static void nd6_llinfo_timer(void *);
 static void clear_llinfo_pqueue(struct llentry *);
 static void nd6_rtrequest(int, struct rtentry *, struct rt_addrinfo *);
@@ -1223,6 +1224,13 @@ nd6_free(struct llentry *ln, int gc)
 			defrouter_select();
 		}
 
+		/*
+		 * If this entry was added by an on-link redirect, remove the
+		 * corresponding host route.
+		 */
+		if (ln->la_flags & LLE_REDIRECT)
+			nd6_free_redirect(ln);
+
 		if (ln->ln_router || dr)
 			LLE_WLOCK(ln);
 	}
@@ -1255,6 +1263,36 @@ nd6_free(struct llentry *ln, int gc)
 	return (next);
 }
 
+/*
+ * Remove the rtentry for the given llentry,
+ * both of which were installed by a redirect.
+ */
+static void
+nd6_free_redirect(const struct llentry *ln)
+{
+	int fibnum;
+	struct rtentry *rt;
+	struct radix_node_head *rnh;
+	struct sockaddr_in6 sin6;
+
+	lltable_fill_sa_entry(ln, (struct sockaddr *)&sin6);
+	for (fibnum = 0; fibnum < rt_numfibs; fibnum++) {
+		rnh = rt_tables_get_rnh(fibnum, AF_INET6);
+		if (rnh == NULL)
+			continue;
+
+		RADIX_NODE_HEAD_LOCK(rnh);
+		rt = in6_rtalloc1((struct sockaddr *)&sin6, 0,
+		    RTF_RNH_LOCKED, fibnum);
+		if (rt) {
+			if (rt->rt_flags == (RTF_UP | RTF_HOST | RTF_DYNAMIC))
+				rt_expunge(rnh, rt);
+			RTFREE_LOCKED(rt);
+		}
+		RADIX_NODE_HEAD_UNLOCK(rnh);
+	}
+}
+
 /*
  * Upper-layer reachability hint for Neighbor Unreachability Detection.
  *
@@ -1746,8 +1784,11 @@ nd6_cache_lladdr(struct ifnet *ifp, struct in6_addr *from, char *lladdr,
 		 */
 		if (code == ND_REDIRECT_ROUTER)
 			ln->ln_router = 1;
-		else if (is_newentry) /* (6-7) */
+		else {
+			if (is_newentry) /* (6-7) */
 				ln->ln_router = 0;
+			ln->la_flags |= LLE_REDIRECT;
+		}
 		break;
 	case ND_ROUTER_SOLICIT:
 		/*

sys/netinet6/nd6_rtr.c

@@ -2105,7 +2105,7 @@ rt6_deleteroute(struct rtentry *rt, void *arg)
 		return (0);
 
 	return (in6_rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway,
-	    rt_mask(rt), rt->rt_flags, NULL, rt->rt_fibnum));
+	    rt_mask(rt), rt->rt_flags | RTF_RNH_LOCKED, NULL, rt->rt_fibnum));
 #undef SIN6
 }