Inbound portion of RFC9131. Routers can create new neighbor cache entries

when receiving a valid Neighbor Advertisement.

OK florian@ kn@

diff --git a/sys/netinet6/nd6_nbr.c b/sys/netinet6/nd6_nbr.c
index f78e232..ab3c122 100644 (file)
--- a/sys/netinet6/nd6_nbr.c
+++ b/sys/netinet6/nd6_nbr.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: nd6_nbr.c,v 1.145 2023/04/25 15:41:17 phessler Exp $  */
+/*     $OpenBSD: nd6_nbr.c,v 1.146 2023/04/28 14:09:06 phessler Exp $  */
 /*     $KAME: nd6_nbr.c,v 1.61 2001/02/10 16:06:14 jinmei Exp $        */
 
 /*
@@ -678,11 +678,40 @@ nd6_na_input(struct mbuf *m, int off, int icmp6len)
                goto bad;
        }
 
+       /* Check if we already have this neighbor in our cache. */
+       rt = nd6_lookup(&taddr6, 0, ifp, ifp->if_rdomain);
+
        /*
+        * If we are a router, we may create new stale cache entries upon
+        * receiving Unsolicited Neighbor Advertisements.
+        */
+       if (rt == NULL && ip6_forwarding == 1) {
+               rt = nd6_lookup(&taddr6, 1, ifp, ifp->if_rdomain);
+               if (rt == NULL || lladdr == NULL ||
+                   ((sdl = satosdl(rt->rt_gateway)) == NULL))
+                       goto freeit;
+
+               ln = (struct llinfo_nd6 *)rt->rt_llinfo;
+               sdl->sdl_alen = ifp->if_addrlen;
+               bcopy(lladdr, LLADDR(sdl), ifp->if_addrlen);
+
+               /*
+                * RFC9131 6.1.1
+                *
+                * Routers SHOULD create a new entry for the target address
+                * with the reachability state set to STALE.
+                */
+               ln->ln_state = ND6_LLINFO_STALE;
+               nd6_llinfo_settimer(ln, nd6_gctimer);
+
+               goto freeit;
+       }
+
+       /*
+        * Host:
         * If no neighbor cache entry is found, NA SHOULD silently be
         * discarded.
         */
-       rt = nd6_lookup(&taddr6, 0, ifp, ifp->if_rdomain);
        if ((rt == NULL) ||
           ((ln = (struct llinfo_nd6 *)rt->rt_llinfo) == NULL) ||
           ((sdl = satosdl(rt->rt_gateway)) == NULL))