INET6: Sort routers when reachability changes

If unreachable, try and install a better default router.

diff --git a/src/ipv6nd.c b/src/ipv6nd.c
index 5a007ab283406aa534bc417306ad990419df2ee3..783ceaedc6bebe4c164ee1cd59ddb02550a03ce4 100644 (file)
--- a/src/ipv6nd.c
+++ b/src/ipv6nd.c
@@ -556,6 +556,60 @@ ipv6nd_startexpire(struct interface *ifp)
            ipv6nd_expire, ifp);
 }
 
+static int
+ipv6nd_rtpref(struct ra *rap)
+{
+
+       switch (rap->flags & ND_RA_FLAG_RTPREF_MASK) {
+       case ND_RA_FLAG_RTPREF_HIGH:
+               return RTPREF_HIGH;
+       case ND_RA_FLAG_RTPREF_MEDIUM:
+       case ND_RA_FLAG_RTPREF_RSV:
+               return RTPREF_MEDIUM;
+       case ND_RA_FLAG_RTPREF_LOW:
+               return RTPREF_LOW;
+       default:
+               logerrx("%s: impossible RA flag %x", __func__, rap->flags);
+               return RTPREF_INVALID;
+       }
+       /* NOTREACHED */
+}
+
+static void
+ipv6nd_sortrouters(struct dhcpcd_ctx *ctx)
+{
+       struct ra_head sorted_routers = TAILQ_HEAD_INITIALIZER(sorted_routers);
+       struct ra *ra1, *ra2;
+
+       /* Pop the first router off */
+       ra1 = TAILQ_FIRST(ctx->ra_routers);
+       TAILQ_REMOVE(ctx->ra_routers, ra1, next);
+       while ((ra1 = TAILQ_FIRST(ctx->ra_routers)) != NULL) {
+               TAILQ_REMOVE(ctx->ra_routers, ra1, next);
+               TAILQ_FOREACH(ra2, &sorted_routers, next) {
+                       if (ra1->iface->metric < ra2->iface->metric)
+                               continue;
+                       if (ra1->expired && !ra2->expired)
+                               continue;
+                       if (ra1->lifetime == 0 && ra2->lifetime != 0)
+                               continue;
+                       if (!ra1->isreachable && ra2->reachable)
+                               continue;
+                       if (ipv6nd_rtpref(ra1) < ipv6nd_rtpref(ra2))
+                               continue;
+                       /* All things being equal, prefer older routers. */
+                       if (timespeccmp(&ra1->acquired, &ra2->acquired, >=))
+                               continue;
+                       TAILQ_INSERT_BEFORE(ra2, ra1, next);
+                       break;
+               }
+               if (ra2 == NULL)
+                       TAILQ_INSERT_TAIL(&sorted_routers, ra1, next);
+       }
+
+       TAILQ_CONCAT(ctx->ra_routers, &sorted_routers, next);
+}
+
 /*
  * Neighbour reachability.
  *
@@ -582,23 +636,16 @@ ipv6nd_neighbour(struct dhcpcd_ctx *ctx, struct in6_addr *addr, bool reachable)
                        break;
        }
 
-       if (rap == NULL || rap->expired)
+       if (rap == NULL || rap->expired || rap->reachable == reachable)
                return;
 
-       if (reachable) {
-               if (rap->isreachable)
-                       return;
-               loginfox("%s: %s is reachable again",
-                   rap->iface->name, rap->sfrom);
-               rap->isreachable = true;
-               return;
-       } else {
-               if (!rap->isreachable)
-                       return;
-               logwarnx("%s: %s is unreachable",
-                   rap->iface->name, rap->sfrom);
-               rap->isreachable = false;
-       }
+       rap->isreachable = reachable;
+       loginfox("%s: %s is %s", rap->iface->name, rap->sfrom,
+           reachable ? "reachable again" : "unreachable");
+
+       /* See if we can install a reachable default router. */
+       ipv6nd_sortrouters(ctx);
+       rt_build(ctx, AF_INET6);
 
        /* If we have no reachable default routers, try and solicit one. */
        TAILQ_FOREACH(rapr, ctx->ra_routers, next) {
@@ -719,42 +766,6 @@ ipv6nd_free(struct interface *ifp)
        return n;
 }
 
-static int
-rtpref(struct ra *rap)
-{
-
-       switch (rap->flags & ND_RA_FLAG_RTPREF_MASK) {
-       case ND_RA_FLAG_RTPREF_HIGH:
-               return (RTPREF_HIGH);
-       case ND_RA_FLAG_RTPREF_MEDIUM:
-       case ND_RA_FLAG_RTPREF_RSV:
-               return (RTPREF_MEDIUM);
-       case ND_RA_FLAG_RTPREF_LOW:
-               return (RTPREF_LOW);
-       default:
-               logerrx("rtpref: impossible RA flag %x", rap->flags);
-               return (RTPREF_INVALID);
-       }
-       /* NOTREACHED */
-}
-
-static void
-add_router(struct dhcpcd_ctx *ctx, struct ra *router)
-{
-       struct ra *rap;
-
-       TAILQ_FOREACH(rap, ctx->ra_routers, next) {
-               if (router->iface->metric < rap->iface->metric ||
-                   (router->iface->metric == rap->iface->metric &&
-                   rtpref(router) > rtpref(rap)))
-               {
-                       TAILQ_INSERT_BEFORE(rap, router, next);
-                       return;
-               }
-       }
-       TAILQ_INSERT_TAIL(ctx->ra_routers, router, next);
-}
-
 static int
 ipv6nd_scriptrun(struct ra *rap)
 {
@@ -1292,7 +1303,9 @@ ipv6nd_handlera(struct dhcpcd_ctx *ctx,
                    ifp->name);
 
        if (new_rap)
-               add_router(ifp->ctx, rap);
+               TAILQ_INSERT_TAIL(ctx->ra_routers, rap, next);
+       if (new_data)
+               ipv6nd_sortrouters(ifp->ctx);
 
        if (ifp->ctx->options & DHCPCD_TEST) {
                script_runreason(ifp, "TEST");