Use getifaddrs to get the interface-id when not specified

Reimplementing this section also fixes two potential bugs:

1. Only link-local addresses should be used for automatic interface-id
   selection, as it should always be assigned by the kernel and is always based
   on the EUI-64 unless an administrator is doing strange things (while other
   addresses might be chosen according to the privacy extensions or by an
   administrator)
2. When no address is available (because of a race condition or because an
   administrator removed it), RA packets should just be ignored; otherwise
   an address with a zero interface-id might be assigned

diff --git a/src/ra.c b/src/ra.c
index ceded54ab9340c90be76b19b3802c0bad576bfa9..d048e85d0419b67205c8203a4e10fff3f4f8da10 100644 (file)
--- a/src/ra.c
+++ b/src/ra.c
@@ -13,6 +13,7 @@
  */
 
 #include <fcntl.h>
+#include <ifaddrs.h>
 #include <stdio.h>
 #include <signal.h>
 #include <string.h>
@@ -24,6 +25,7 @@
 #include <net/if.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>
+#include <sys/types.h>
 #include <netinet/in.h>
 #include <netinet/icmp6.h>
 
@@ -225,23 +227,36 @@ bool ra_process(void)
 {
        bool found = false;
        bool changed = false;
+       bool has_lladdr = !IN6_IS_ADDR_UNSPECIFIED(&lladdr);
        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, 0, 0};
        const struct in6_addr any = IN6ADDR_ANY_INIT;
 
-       if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
+       if (!has_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);
+               struct ifaddrs *ifaddr, *ifa;
+
+               if (getifaddrs(&ifaddr) == 0) {
+                       for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
+                               struct sockaddr_in6 *addr;
+
+                               if (ifa->ifa_addr == NULL || ifa->ifa_addr->sa_family != AF_INET6)
+                                       continue;
+
+                               addr = (struct sockaddr_in6*)ifa->ifa_addr;
+
+                               if (!IN6_IS_ADDR_LINKLOCAL(&addr->sin6_addr))
+                                       continue;
+
+                               if (!strcmp(ifa->ifa_name, if_name)) {
+                                       lladdr = addr->sin6_addr;
+                                       has_lladdr = true;
                                        break;
                                }
                        }
-                       fclose(fp);
+
+                       freeifaddrs(ifaddr);
                }
        }
 
@@ -255,6 +270,9 @@ bool ra_process(void)
                if (len <= 0)
                        break;
 
+               if (!has_lladdr)
+                       continue;
+
                int hlim = 0;
                for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
                                ch = CMSG_NXTHDR(&msg, ch))