IPv6: Resolicit a router just before it expires naturally

It seems that some routers don't send out periodic advertisements
as they should. To work around this, re-solicit a router just before
it's about to expire.

Fixes #92.

diff --git a/src/ipv6nd.c b/src/ipv6nd.c
index 4b9c735df44d3442007665ed95732958e079b4b0..1cdddf21460a1d49b809d35fcd4c9d320a0685da 100644 (file)
--- a/src/ipv6nd.c
+++ b/src/ipv6nd.c
@@ -132,6 +132,7 @@ __CTASSERT(sizeof(struct nd_opt_rdnss) == 8);
 //
 
 static void ipv6nd_handledata(void *, unsigned short);
+static void ipv6nd_startrs1(void *);
 
 /*
  * Android ships buggy ICMP6 filter headers.
@@ -1748,7 +1749,8 @@ ipv6nd_handleifa(int cmd, struct ipv6_addr *addr, pid_t pid)
 void
 ipv6nd_expirera(void *arg)
 {
-       struct interface *ifp;
+       struct interface *ifp = arg;
+       struct dhcpcd_ctx *ctx = ifp->ctx;
        struct ra *rap, *ran;
        struct timespec now;
        uint32_t elapsed;
@@ -1762,14 +1764,13 @@ ipv6nd_expirera(void *arg)
 #endif
        struct nd_opt_dnssl dnssl;
        struct nd_opt_rdnss rdnss;
-       unsigned int next = 0, ltime;
+       unsigned int next = 0, nextrs = 0, ltime;
        size_t nexpired = 0;
 
-       ifp = arg;
        clock_gettime(CLOCK_MONOTONIC, &now);
        expired = false;
 
-       TAILQ_FOREACH_SAFE(rap, ifp->ctx->ra_routers, next, ran) {
+       TAILQ_FOREACH_SAFE(rap, ctx->ra_routers, next, ran) {
                if (rap->iface != ifp || rap->expired)
                        continue;
                valid = false;
@@ -1788,6 +1789,8 @@ ipv6nd_expirera(void *arg)
                                ltime = rap->lifetime - elapsed;
                                if (next == 0 || ltime < next)
                                        next = ltime;
+                               if (nextrs == 0 || ltime < nextrs)
+                                       nextrs = ltime;
                        }
                }
 
@@ -1906,15 +1909,27 @@ ipv6nd_expirera(void *arg)
                        ipv6nd_free_ra(rap);
        }
 
+       /* It seems that some routers fail to send periodic advertisements.
+        * As such, send a Router Solicition just before the advertisement
+        * expires. */
+       if (nextrs != 0) {
+               unsigned int rstime = nextrs -
+                   (MAX_RTR_SOLICITATIONS * RTR_SOLICITATION_INTERVAL) +
+                   (MAX_RTR_SOLICITATION_DELAY * 3);
+
+               if (rstime > nextrs)
+                       rstime = 0;
+               eloop_timeout_add_sec(ctx->eloop, rstime, ipv6nd_startrs1, ifp);
+       }
+
        if (next != 0)
-               eloop_timeout_add_sec(ifp->ctx->eloop,
-                   next, ipv6nd_expirera, ifp);
+               eloop_timeout_add_sec(ctx->eloop, next, ipv6nd_expirera, ifp);
        if (expired) {
                logwarnx("%s: part of a Router Advertisement expired",
                    ifp->name);
-               ipv6nd_sortrouters(ifp->ctx);
+               ipv6nd_sortrouters(ctx);
                ipv6nd_applyra(ifp);
-               rt_build(ifp->ctx, AF_INET6);
+               rt_build(ctx, AF_INET6);
                script_runreason(ifp, "ROUTERADVERT");
        }
 }