add IPv6 default route interface auto-detection for permanent/temporary IPv6 without netif

- get_default_route_netif_index(): UDP connect trick + getifaddrs to find default route iface
- etcp_socket_add(): auto-detect netif_index when not specified in config
- queue_new() API: explicit index_offset/index_size params instead of implicit from hash_size
- radix: cleanup types (uint8_t*), replace bzero/bcmp with memset/memcmp, remove kernel ifdefs
- route6_lib: new IPv6 routing library + get_node_v6_routes()

lib/platform_compat.c

@@ -105,6 +105,80 @@ int get_interface_ipv6_by_index(uint32_t netif_index, int temporary, uint8_t* ad
     freeifaddrs(ifaddr);
     return found ? 0 : -1;
 }
+
+uint32_t get_default_route_netif_index(int family) {
+    if (family != AF_INET && family != AF_INET6) return 0;
+
+    int sock = socket(family, SOCK_DGRAM, IPPROTO_UDP);
+    if (sock < 0) return 0;
+
+    struct sockaddr_storage bind_addr;
+    memset(&bind_addr, 0, sizeof(bind_addr));
+    if (family == AF_INET) {
+        struct sockaddr_in* sin = (struct sockaddr_in*)&bind_addr;
+        sin->sin_family = AF_INET;
+        sin->sin_addr.s_addr = INADDR_ANY;
+    } else {
+        struct sockaddr_in6* sin6 = (struct sockaddr_in6*)&bind_addr;
+        sin6->sin6_family = AF_INET6;
+        sin6->sin6_addr = in6addr_any;
+    }
+
+    socklen_t bind_len = (family == AF_INET) ? sizeof(struct sockaddr_in) : sizeof(struct sockaddr_in6);
+    if (bind(sock, (struct sockaddr*)&bind_addr, bind_len) != 0) { close(sock); return 0; }
+
+    struct sockaddr_storage remote;
+    memset(&remote, 0, sizeof(remote));
+    socklen_t remote_len;
+    if (family == AF_INET) {
+        struct sockaddr_in* sin = (struct sockaddr_in*)&remote;
+        sin->sin_family = AF_INET;
+        sin->sin_port = htons(53);
+        inet_pton(AF_INET, "8.8.8.8", &sin->sin_addr);
+        remote_len = sizeof(struct sockaddr_in);
+    } else {
+        struct sockaddr_in6* sin6 = (struct sockaddr_in6*)&remote;
+        sin6->sin6_family = AF_INET6;
+        sin6->sin6_port = htons(53);
+        inet_pton(AF_INET6, "2001:4860:4860::8888", &sin6->sin6_addr);
+        remote_len = sizeof(struct sockaddr_in6);
+    }
+
+    if (connect(sock, (struct sockaddr*)&remote, remote_len) != 0) { close(sock); return 0; }
+
+    struct sockaddr_storage src;
+    socklen_t src_len = sizeof(src);
+    if (getsockname(sock, (struct sockaddr*)&src, &src_len) != 0) { close(sock); return 0; }
+
+    close(sock);
+
+    struct ifaddrs *ifaddr, *ifa;
+    if (getifaddrs(&ifaddr) == -1) return 0;
+
+    uint32_t result = 0;
+    for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
+        if (ifa->ifa_addr == NULL) continue;
+        if (ifa->ifa_addr->sa_family != family) continue;
+        if (family == AF_INET) {
+            struct sockaddr_in* src_sin = (struct sockaddr_in*)&src;
+            struct sockaddr_in* ifa_sin = (struct sockaddr_in*)ifa->ifa_addr;
+            if (src_sin->sin_addr.s_addr == ifa_sin->sin_addr.s_addr) {
+                if (ifa->ifa_name) result = if_nametoindex(ifa->ifa_name);
+                break;
+            }
+        } else {
+            struct sockaddr_in6* src_sin6 = (struct sockaddr_in6*)&src;
+            struct sockaddr_in6* ifa_sin6 = (struct sockaddr_in6*)ifa->ifa_addr;
+            if (memcmp(&src_sin6->sin6_addr, &ifa_sin6->sin6_addr, 16) == 0) {
+                if (ifa->ifa_name) result = if_nametoindex(ifa->ifa_name);
+                break;
+            }
+        }
+    }
+
+    freeifaddrs(ifaddr);
+    return result;
+}
 #else
 uint32_t get_interface_ip_by_index(uint32_t netif_index) {
     (void)netif_index;
@@ -116,4 +190,9 @@ int get_interface_ipv6_by_index(uint32_t netif_index, int temporary, uint8_t* ad
     if (addr_out) memset(addr_out, 0, 16);
     return -1;
 }
+
+uint32_t get_default_route_netif_index(int family) {
+    (void)family;
+    return 0;
+}
 #endif