Enhance sock_addr_local syscall (#1320)

Slightly change the __wasi_sock_addr_local interface - since we already have
a `__wasi_addr_t` structure which is an union, there's no need for passing the
length around - the address buffer will always have the right length (i.e. max
of all address families).

samples/socket-api/wasm-src/tcp_client.c

@@ -19,7 +19,10 @@ main(int argc, char *argv[])
 {
     int socket_fd, ret, total_size = 0;
     char buffer[1024] = { 0 };
+    char ip_string[16] = { 0 };
     struct sockaddr_in server_address = { 0 };
+    struct sockaddr_in local_address = { 0 };
+    socklen_t len;
 
     printf("[Client] Create socket\n");
     socket_fd = socket(AF_INET, SOCK_STREAM, 0);
@@ -42,6 +45,20 @@ main(int argc, char *argv[])
         return EXIT_FAILURE;
     }
 
+    len = sizeof(local_address);
+    ret = getsockname(socket_fd, (struct sockaddr *)&local_address, &len);
+    if (ret == -1) {
+        perror("Failed to retrieve socket address");
+        close(socket_fd);
+        return EXIT_FAILURE;
+    }
+
+    inet_ntop(AF_INET, &local_address.sin_addr, ip_string,
+              sizeof(ip_string) / sizeof(ip_string[0]));
+
+    printf("[Client] Local address is: %s:%d\n", ip_string,
+           ntohs(local_address.sin_port));
+
     printf("[Client] Client receive\n");
     while (1) {
         ret = recv(socket_fd, buffer + total_size, sizeof(buffer) - total_size,