new function: aws_socket_get_bound_address() (#491)

Enable users to bind on port 0, which has the OS assign a port, and then query which port it ended up with.

The socket stores this address during `aws_socket_bind()` call, which allows `aws_socket_get_bound_address()` to be const and avoid any tricky threading issues where the socked closes on another thread.

Also fix a few subtle bugs in Windows socket code.

Co-authored-by: Vitaly Khalmansky <vkhalmansky@klika-tech.com>

Author: graebm

include/aws/io/socket.h

@@ -176,6 +176,12 @@ AWS_IO_API int aws_socket_connect(
  */
 AWS_IO_API int aws_socket_bind(struct aws_socket *socket, const struct aws_socket_endpoint *local_endpoint);
 
+/**
+ * Get the local address which the socket is bound to.
+ * Raises an error if no address is bound.
+ */
+AWS_IO_API int aws_socket_get_bound_address(const struct aws_socket *socket, struct aws_socket_endpoint *out_address);
+
 /**
  * TCP, LOCAL and VSOCK only. Sets up the socket to listen on the address bound to in `aws_socket_bind()`.
  */

source/posix/socket.c

@@ -263,6 +263,98 @@ void aws_socket_clean_up(struct aws_socket *socket) {
     socket->io_handle.data.fd = -1;
 }
 
+/* Update socket->local_endpoint based on the results of getsockname() */
+static int s_update_local_endpoint(struct aws_socket *socket) {
+    struct aws_socket_endpoint tmp_endpoint;
+    AWS_ZERO_STRUCT(tmp_endpoint);
+
+    struct sockaddr_storage address;
+    AWS_ZERO_STRUCT(address);
+    socklen_t address_size = sizeof(address);
+
+    if (getsockname(socket->io_handle.data.fd, (struct sockaddr *)&address, &address_size) != 0) {
+        AWS_LOGF_ERROR(
+            AWS_LS_IO_SOCKET,
+            "id=%p fd=%d: getsockname() failed with error %d",
+            (void *)socket,
+            socket->io_handle.data.fd,
+            errno);
+        int aws_error = s_determine_socket_error(errno);
+        return aws_raise_error(aws_error);
+    }
+
+    if (address.ss_family == AF_INET) {
+        struct sockaddr_in *s = (struct sockaddr_in *)&address;
+        tmp_endpoint.port = ntohs(s->sin_port);
+        if (inet_ntop(AF_INET, &s->sin_addr, tmp_endpoint.address, sizeof(tmp_endpoint.address)) == NULL) {
+            AWS_LOGF_ERROR(
+                AWS_LS_IO_SOCKET,
+                "id=%p fd=%d: inet_ntop() failed with error %d",
+                (void *)socket,
+                socket->io_handle.data.fd,
+                errno);
+            int aws_error = s_determine_socket_error(errno);
+            return aws_raise_error(aws_error);
+        }
+    } else if (address.ss_family == AF_INET6) {
+        struct sockaddr_in6 *s = (struct sockaddr_in6 *)&address;
+        tmp_endpoint.port = ntohs(s->sin6_port);
+        if (inet_ntop(AF_INET6, &s->sin6_addr, tmp_endpoint.address, sizeof(tmp_endpoint.address)) == NULL) {
+            AWS_LOGF_ERROR(
+                AWS_LS_IO_SOCKET,
+                "id=%p fd=%d: inet_ntop() failed with error %d",
+                (void *)socket,
+                socket->io_handle.data.fd,
+                errno);
+            int aws_error = s_determine_socket_error(errno);
+            return aws_raise_error(aws_error);
+        }
+    } else if (address.ss_family == AF_UNIX) {
+        struct sockaddr_un *s = (struct sockaddr_un *)&address;
+
+        /* Ensure there's a null-terminator.
+         * On some platforms it may be missing when the path gets very long. See:
+         * https://man7.org/linux/man-pages/man7/unix.7.html#BUGS
+         * But let's keep it simple, and not deal with that madness until someone demands it. */
+        size_t sun_len;
+        if (aws_secure_strlen(s->sun_path, sizeof(tmp_endpoint.address), &sun_len)) {
+            AWS_LOGF_ERROR(
+                AWS_LS_IO_SOCKET,
+                "id=%p fd=%d: UNIX domain socket name is too long",
+                (void *)socket,
+                socket->io_handle.data.fd);
+            return aws_raise_error(AWS_IO_SOCKET_INVALID_ADDRESS);
+        }
+        memcpy(tmp_endpoint.address, s->sun_path, sun_len);
+#if USE_VSOCK
+    } else if (address.ss_family == AF_VSOCK) {
+        struct sockaddr_vm *s = (struct sockaddr_vm *)&address;
+
+        /* VSOCK port is 32bit, but aws_socket_endpoint.port is only 16bit.
+         * Hopefully this isn't an issue, since users can only pass in 16bit values.
+         * But if it becomes an issue, we'll need to make aws_socket_endpoint more flexible */
+        if (s->svm_port > UINT16_MAX) {
+            AWS_LOGF_ERROR(
+                AWS_LS_IO_SOCKET,
+                "id=%p fd=%d: aws_socket_endpoint can't deal with VSOCK port > UINT16_MAX",
+                (void *)socket,
+                socket->io_handle.data.fd);
+            return aws_raise_error(AWS_IO_SOCKET_INVALID_ADDRESS);
+        }
+        tmp_endpoint.port = (uint16_t)s->svm_port;
+
+        snprintf(tmp_endpoint.address, sizeof(tmp_endpoint.address), "%" PRIu32, s->svm_cid);
+        return AWS_OP_SUCCESS;
+#endif /* USE_VSOCK */
+    } else {
+        AWS_ASSERT(0);
+        return aws_raise_error(AWS_IO_SOCKET_UNSUPPORTED_ADDRESS_FAMILY);
+    }
+
+    socket->local_endpoint = tmp_endpoint;
+    return AWS_OP_SUCCESS;
+}
+
 static void s_on_connection_error(struct aws_socket *socket, int error);
 
 static int s_on_connection_success(struct aws_socket *socket) {
@@ -308,67 +400,8 @@ static int s_on_connection_success(struct aws_socket *socket) {
 
     AWS_LOGF_INFO(AWS_LS_IO_SOCKET, "id=%p fd=%d: connection success", (void *)socket, socket->io_handle.data.fd);
 
-    struct sockaddr_storage address;
-    AWS_ZERO_STRUCT(address);
-    socklen_t address_size = sizeof(address);
-    if (!getsockname(socket->io_handle.data.fd, (struct sockaddr *)&address, &address_size)) {
-        uint16_t port = 0;
-
-        if (address.ss_family == AF_INET) {
-            struct sockaddr_in *s = (struct sockaddr_in *)&address;
-            port = ntohs(s->sin_port);
-            /* this comes straight from the kernal. a.) they won't fail. b.) even if they do, it's not fatal
-             * once we add logging, we can log this if it fails. */
-            if (inet_ntop(
-                    AF_INET, &s->sin_addr, socket->local_endpoint.address, sizeof(socket->local_endpoint.address))) {
-                AWS_LOGF_DEBUG(
-                    AWS_LS_IO_SOCKET,
-                    "id=%p fd=%d: local endpoint %s:%d",
-                    (void *)socket,
-                    socket->io_handle.data.fd,
-                    socket->local_endpoint.address,
-                    port);
-            } else {
-                AWS_LOGF_WARN(
-                    AWS_LS_IO_SOCKET,
-                    "id=%p fd=%d: determining local endpoint failed",
-                    (void *)socket,
-                    socket->io_handle.data.fd);
-            }
-        } else if (address.ss_family == AF_INET6) {
-            struct sockaddr_in6 *s = (struct sockaddr_in6 *)&address;
-            port = ntohs(s->sin6_port);
-            /* this comes straight from the kernal. a.) they won't fail. b.) even if they do, it's not fatal
-             * once we add logging, we can log this if it fails. */
-            if (inet_ntop(
-                    AF_INET6, &s->sin6_addr, socket->local_endpoint.address, sizeof(socket->local_endpoint.address))) {
-                AWS_LOGF_DEBUG(
-                    AWS_LS_IO_SOCKET,
-                    "id=%p fd %d: local endpoint %s:%d",
-                    (void *)socket,
-                    socket->io_handle.data.fd,
-                    socket->local_endpoint.address,
-                    port);
-            } else {
-                AWS_LOGF_WARN(
-                    AWS_LS_IO_SOCKET,
-                    "id=%p fd=%d: determining local endpoint failed",
-                    (void *)socket,
-                    socket->io_handle.data.fd);
-            }
-        }
-
-        socket->local_endpoint.port = port;
-    } else {
-        AWS_LOGF_ERROR(
-            AWS_LS_IO_SOCKET,
-            "id=%p fd=%d: getsockname() failed with error %d",
-            (void *)socket,
-            socket->io_handle.data.fd,
-            errno);
-        int aws_error = s_determine_socket_error(errno);
-        aws_raise_error(aws_error);
-        s_on_connection_error(socket, aws_error);
+    if (s_update_local_endpoint(socket)) {
+        s_on_connection_error(socket, aws_last_error());
         return AWS_OP_ERR;
     }
 
@@ -761,9 +794,6 @@ int aws_socket_bind(struct aws_socket *socket, const struct aws_socket_endpoint
         return AWS_OP_ERR;
     }
 
-    int error_code = -1;
-
-    socket->local_endpoint = *local_endpoint;
     AWS_LOGF_INFO(
         AWS_LS_IO_SOCKET,
         "id=%p fd=%d: binding to %s:%d.",
@@ -813,31 +843,55 @@ int aws_socket_bind(struct aws_socket *socket, const struct aws_socket_endpoint
         return aws_raise_error(s_convert_pton_error(pton_err));
     }
 
-    error_code = bind(socket->io_handle.data.fd, (struct sockaddr *)&address.sock_addr_types, sock_size);
+    if (bind(socket->io_handle.data.fd, (struct sockaddr *)&address.sock_addr_types, sock_size) != 0) {
+        AWS_LOGF_ERROR(
+            AWS_LS_IO_SOCKET,
+            "id=%p fd=%d: bind failed with error code %d",
+            (void *)socket,
+            socket->io_handle.data.fd,
+            errno);
 
-    if (!error_code) {
-        if (socket->options.type == AWS_SOCKET_STREAM) {
-            socket->state = BOUND;
-        } else {
-            /* e.g. UDP is now readable */
-            socket->state = CONNECTED_READ;
-        }
-        AWS_LOGF_DEBUG(AWS_LS_IO_SOCKET, "id=%p fd=%d: successfully bound", (void *)socket, socket->io_handle.data.fd);
+        aws_raise_error(s_determine_socket_error(errno));
+        goto error;
+    }
 
-        return AWS_OP_SUCCESS;
+    if (s_update_local_endpoint(socket)) {
+        goto error;
     }
 
-    socket->state = ERROR;
-    error_code = errno;
-    AWS_LOGF_ERROR(
+    if (socket->options.type == AWS_SOCKET_STREAM) {
+        socket->state = BOUND;
+    } else {
+        /* e.g. UDP is now readable */
+        socket->state = CONNECTED_READ;
+    }
+
+    AWS_LOGF_DEBUG(
         AWS_LS_IO_SOCKET,
-        "id=%p fd=%d: bind failed with error code %d",
+        "id=%p fd=%d: successfully bound to %s:%d",
         (void *)socket,
         socket->io_handle.data.fd,
-        error_code);
+        socket->local_endpoint.address,
+        socket->local_endpoint.port);
 
-    int aws_error = s_determine_socket_error(error_code);
-    return aws_raise_error(aws_error);
+    return AWS_OP_SUCCESS;
+
+error:
+    socket->state = ERROR;
+    return AWS_OP_ERR;
+}
+
+int aws_socket_get_bound_address(const struct aws_socket *socket, struct aws_socket_endpoint *out_address) {
+    if (socket->local_endpoint.address[0] == 0) {
+        AWS_LOGF_ERROR(
+            AWS_LS_IO_SOCKET,
+            "id=%p fd=%d: Socket has no local address. Socket must be bound first.",
+            (void *)socket,
+            socket->io_handle.data.fd);
+        return aws_raise_error(AWS_IO_SOCKET_ILLEGAL_OPERATION_FOR_STATE);
+    }
+    *out_address = socket->local_endpoint;
+    return AWS_OP_SUCCESS;
 }
 
 int aws_socket_listen(struct aws_socket *socket, int backlog_size) {