Fall back to getifaddrs() to get an interface address if there is no default route.

[meshlink] / src / meshlink.c

diff --git a/src/meshlink.c b/src/meshlink.c
index a93bdd674ac32579adc39ddf337645599f0bd913..5b01ad2c1fda7b12abb823baa9c80da391177fb7 100644 (file)
--- a/src/meshlink.c
+++ b/src/meshlink.c
@@ -287,6 +287,21 @@ char *meshlink_get_external_address_for_family(meshlink_handle_t *mesh, int fami
        return hostname;
 }
 
+static bool is_localaddr(sockaddr_t *sa) {
+       switch(sa->sa.sa_family) {
+       case AF_INET:
+               return *(uint8_t *)(&sa->in.sin_addr.s_addr) == 127;
+
+       case AF_INET6: {
+               uint16_t first = sa->in6.sin6_addr.s6_addr[0] << 8 | sa->in6.sin6_addr.s6_addr[1];
+               return first == 0 || (first & 0xffc0) == 0xfe80;
+       }
+
+       default:
+               return false;
+       }
+}
+
 char *meshlink_get_local_address_for_family(meshlink_handle_t *mesh, int family) {
        (void)mesh;
 
@@ -300,6 +315,34 @@ char *meshlink_get_local_address_for_family(meshlink_handle_t *mesh, int family)
                success = getlocaladdrname("2606:2800:220:1:248:1893:25c8:1946", localaddr, sizeof(localaddr), mesh->netns);
        }
 
+#ifdef HAVE_GETIFADDRS
+
+       if(!success) {
+               struct ifaddrs *ifa = NULL;
+               getifaddrs(&ifa);
+
+               for(struct ifaddrs *ifap = ifa; ifap; ifap = ifap->ifa_next) {
+                       sockaddr_t *sa = (sockaddr_t *)ifap->ifa_addr;
+
+                       if(sa->sa.sa_family != family) {
+                               continue;
+                       }
+
+                       if(is_localaddr(sa)) {
+                               continue;
+                       }
+
+                       if(!getnameinfo(&sa->sa, SALEN(sa->sa), localaddr, sizeof(localaddr), NULL, 0, NI_NUMERICHOST | NI_NUMERICSERV)) {
+                               success = true;
+                               break;
+                       }
+               }
+
+               freeifaddrs(ifa);
+       }
+
+#endif
+
        if(!success) {
                meshlink_errno = MESHLINK_ENETWORK;
                return NULL;