ra: fix sending router solicitations

Only stop sending router solicitations when a RA is received with a
valid router lifetime as specified in RFC4861 §6.3.7

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

diff --git a/src/ra.c b/src/ra.c
index 898f449168e29bae08e48e9395f420d13b2ec899..337c0bddc9377e5b427246ee85094d91625aace7 100644 (file)
--- a/src/ra.c
+++ b/src/ra.c
@@ -377,6 +377,9 @@ bool ra_process(void)
                        .msg_controllen = sizeof(cmsg_buf),
                        .msg_flags = 0
                };
+               struct icmpv6_opt *opt;
+               uint32_t router_valid;
+               int hlim = 0;
 
                ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
                if (len <= 0)
@@ -385,7 +388,6 @@ bool ra_process(void)
                if (IN6_IS_ADDR_UNSPECIFIED(&lladdr))
                        continue;
 
-               int hlim = 0;
                for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
                                ch = CMSG_NXTHDR(&msg, ch))
                        if (ch->cmsg_level == IPPROTO_IPV6 &&
@@ -395,17 +397,24 @@ bool ra_process(void)
                if (!ra_icmpv6_valid(&from, hlim, buf, len))
                        continue;
 
-               // Stop sending solicits
-               if (rs_attempt > 0) {
-                       alarm(0);
-                       rs_attempt = 0;
-               }
-
                if (!found) {
                        odhcp6c_expire();
                        found = true;
                }
-               uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
+
+               router_valid = ntohs(adv->nd_ra_router_lifetime);
+
+               /* RFC4861 §6.3.7
+                * Once the host sends a Router Solicitation, and receives a valid
+                * Router Advertisement with a non-zero Router Lifetime, the host MUST
+                * desist from sending additional solicitations on that interface
+                * Moreover, a host SHOULD send at least one solicitation in the case
+                * where an advertisement is received prior to having sent a solicitation.
+                */
+               if (rs_attempt > 0 && router_valid > 0) {
+                       alarm(0);
+                       rs_attempt = 0;
+               }
 
                // Parse default route
                entry->target = any;
@@ -428,7 +437,6 @@ bool ra_process(void)
                changed |= ra_set_retransmit(ntohl(adv->nd_ra_retransmit));
 
                // Evaluate options
-               struct icmpv6_opt *opt;
                icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
                        if (opt->type == ND_OPT_MTU) {
                                uint32_t *mtu = (uint32_t*)&opt->data[2];