odhcp6c: improve server selection

[odhcp6c.git] / src / ra.c

diff --git a/src/ra.c b/src/ra.c
index 9c1ed74d4ee4e89b90702ae8f33554ff34706bff..83f17584cbe93f9a4587a0e095432fa295b91de1 100644 (file)
--- a/src/ra.c
+++ b/src/ra.c
@@ -67,6 +67,10 @@ int ra_init(const char *ifname, const struct in6_addr *ifid)
        val = 255;
        setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 
+       // Receive multicast hops
+       val = 1;
+       setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
+
        // Bind to one device
        setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 
@@ -75,21 +79,6 @@ int ra_init(const char *ifname, const struct in6_addr *ifid)
        fcntl(sock, F_SETOWN, ourpid);
        fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 
-       if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
-               // Autodetect interface-id if not specified
-               FILE *fp = fopen("/proc/net/if_inet6", "r");
-               if (fp) {
-                       char addrbuf[33], ifbuf[16];
-                       while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
-                               if (!strcmp(ifbuf, if_name)) {
-                                       script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
-                                       break;
-                               }
-                       }
-                       fclose(fp);
-               }
-       }
-
        // Send RS
        signal(SIGALRM, ra_send_rs);
        ra_send_rs(SIGALRM);
@@ -131,20 +120,48 @@ static void update_proc(const char *sect, const char *opt, uint32_t value)
 bool ra_process(void)
 {
        bool found = false;
-       uint8_t buf[1500];
+       uint8_t buf[1500], cmsg_buf[128];
        struct nd_router_advert *adv = (struct nd_router_advert*)buf;
        struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0};
        const struct in6_addr any = IN6ADDR_ANY_INIT;
 
+       if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
+               // Autodetect interface-id if not specified
+               FILE *fp = fopen("/proc/net/if_inet6", "r");
+               if (fp) {
+                       char addrbuf[33], ifbuf[16];
+                       while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
+                               if (!strcmp(ifbuf, if_name)) {
+                                       script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
+                                       break;
+                               }
+                       }
+                       fclose(fp);
+               }
+       }
+
        while (true) {
                struct sockaddr_in6 from;
-               socklen_t from_len = sizeof(from);
-               ssize_t len = recvfrom(sock, buf, sizeof(buf), MSG_DONTWAIT, &from, &from_len);
+               struct iovec iov = {buf, sizeof(buf)};
+               struct msghdr msg = {&from, sizeof(from), &iov, 1,
+                               cmsg_buf, sizeof(cmsg_buf), 0};
+
+               ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
                if (len < 0)
                        break;
                else if (len < (ssize_t)sizeof(*adv))
                        continue;
 
+               int hlim = 0;
+               for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
+                               ch = CMSG_NXTHDR(&msg, ch))
+                       if (ch->cmsg_level == IPPROTO_IPV6 &&
+                                       ch->cmsg_type == IPV6_HOPLIMIT)
+                               memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
+
+               if (hlim != 255)
+                       continue;
+
                // Stop sending solicits
                if (rs_attempt > 0) {
                        alarm(0);