+ if (cmsg->cmsg_level != SOL_SOCKET) {
+ fprintf(stderr, "Error: The socket needs to be of type SOL_SOCKET\n");
+ ret = -1;
+ goto end;
+ }
+ if (cmsg->cmsg_type == SCM_RIGHTS) {
+ /*
+ * We found the controle message for file descriptors,
+ * now copy the fds to the fds ptr and return success.
+ */
+ if (cmsg->cmsg_len != CMSG_LEN(sizeof_fds)) {
+ fprintf(stderr, "Error: Received %zu bytes of"
+ "ancillary data for FDs, expected %zu\n",
+ (size_t) cmsg->cmsg_len,
+ (size_t) CMSG_LEN(sizeof_fds));
+ ret = -1;
+ goto end;
+ }
+ memcpy(fds, CMSG_DATA(cmsg), sizeof_fds);
+ ret = sizeof_fds;
+ goto end;
+ }
+#ifdef __linux__
+ if (cmsg->cmsg_type == SCM_CREDENTIALS) {
+ /*
+ * Expect credentials to be sent when expecting fds even
+ * if no credential were include in the send(). The
+ * kernel adds them...
+ */
+ ret = -1;
+ }
+#endif /* __linux__ */
+ }
+end:
+ return ret;
+}
+
+static
+void close_raw_fd(void *ptr)
+{
+ const int raw_fd = *((const int *) ptr);
+
+ if (raw_fd >= 0) {
+ const int ret = close(raw_fd);
+
+ if (ret) {
+ PERROR("Failed to close file descriptor %d", raw_fd);
+ }
+ }
+}
+
+static
+enum lttng_error_code add_fds_to_payload(struct lttng_dynamic_array *raw_fds,
+ struct lttng_payload *payload)
+{
+ int i;
+ enum lttng_error_code ret_code = LTTNG_OK;
+ const int fd_count = lttng_dynamic_array_get_count(raw_fds);
+
+ for (i = 0; i < fd_count; i++) {
+ int ret;
+ struct fd_handle *handle;
+ int *raw_fd = (int *) lttng_dynamic_array_get_element(
+ raw_fds, i);
+
+ assert(*raw_fd != -1);
+
+ handle = fd_handle_create(*raw_fd);
+ if (!handle) {
+ ret_code = LTTNG_ERR_NOMEM;
+ goto end;
+ }
+
+ /* FD ownership transferred to the handle. */
+ *raw_fd = -1;
+
+ ret = lttng_payload_push_fd_handle(payload, handle);
+ fd_handle_put(handle);
+ if (ret) {
+ ret_code = LTTNG_ERR_NOMEM;
+ goto end;
+ }
+ }
+
+end:
+ return ret_code;
+}
+
+static
+ssize_t _lttcomm_recv_payload_fds_unix_sock(int sock, size_t nb_fd,
+ struct lttng_payload *payload, bool blocking)
+{
+ int i = 0;
+ enum lttng_error_code add_ret;
+ ssize_t ret;
+ int default_value = -1;
+ struct lttng_dynamic_array raw_fds;
+
+ assert(sock);
+ assert(payload);
+ assert(nb_fd > 0);
+
+ lttng_dynamic_array_init(&raw_fds, sizeof(int), close_raw_fd);
+
+ for (i = 0; i < nb_fd; i++) {
+ if (lttng_dynamic_array_add_element(&raw_fds, &default_value)) {
+ ret = -LTTNG_ERR_NOMEM;
+ goto end;
+ }
+ }
+
+ if (blocking) {
+ ret = lttcomm_recv_fds_unix_sock(
+ sock, (int *) raw_fds.buffer.data, nb_fd);
+ } else {
+ ret = lttcomm_recv_fds_unix_sock_non_block(
+ sock, (int *) raw_fds.buffer.data, nb_fd);
+ }
+
+ if (ret <= 0) {
+ goto end;
+ }
+
+ add_ret = add_fds_to_payload(&raw_fds, payload);
+ if (add_ret != LTTNG_OK) {
+ ret = - (int) add_ret;
+ goto end;
+ }
+
+end:
+ lttng_dynamic_array_reset(&raw_fds);
+ return ret;
+}
+
+LTTNG_HIDDEN
+ssize_t lttcomm_recv_payload_fds_unix_sock(int sock, size_t nb_fd,
+ struct lttng_payload *payload)
+{
+ return _lttcomm_recv_payload_fds_unix_sock(sock, nb_fd, payload, true);
+}
+
+LTTNG_HIDDEN
+ssize_t lttcomm_recv_payload_fds_unix_sock_non_block(int sock, size_t nb_fd,
+ struct lttng_payload *payload)
+{
+ return _lttcomm_recv_payload_fds_unix_sock(sock, nb_fd, payload, false);
+}
+
+/*
+ * Recv a message accompanied by fd(s) from a non-blocking unix socket.
+ * Only use with non-blocking sockets.
+ *
+ * Returns the size of received data, or negative error value.
+ *
+ * Expect at most "nb_fd" file descriptors.
+ *
+ * Note that based on our comprehension, partial reception of fds is not
+ * possible since the FDs are actually in the control message. It is all or
+ * nothing, still the sender side can send the wrong number of fds.
+ */
+LTTNG_HIDDEN
+ssize_t lttcomm_recv_fds_unix_sock_non_block(int sock, int *fds, size_t nb_fd)
+{
+ struct iovec iov[1];
+ ssize_t ret = 0;
+ struct cmsghdr *cmsg;
+ size_t sizeof_fds = nb_fd * sizeof(int);
+
+ assert(sock);
+ assert(fds);
+ assert(nb_fd > 0);
+
+#ifdef __linux__
+/* Account for the struct ucred cmsg in the buffer size */
+#define LTTNG_SOCK_RECV_FDS_BUF_SIZE CMSG_SPACE(sizeof_fds) + CMSG_SPACE(sizeof(struct ucred))
+#else
+#define LTTNG_SOCK_RECV_FDS_BUF_SIZE CMSG_SPACE(sizeof_fds)
+#endif /* __linux__ */
+
+ char recv_buf[LTTNG_SOCK_RECV_FDS_BUF_SIZE];
+ struct msghdr msg;
+ char dummy;
+
+ memset(&msg, 0, sizeof(msg));
+
+ /* Prepare to receive the structures */
+ iov[0].iov_base = &dummy;
+ iov[0].iov_len = 1;
+ msg.msg_iov = iov;
+ msg.msg_iovlen = 1;
+
+ cmsg = (struct cmsghdr *) recv_buf;
+ cmsg->cmsg_len = CMSG_LEN(sizeof_fds);
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+
+ msg.msg_control = cmsg;
+ msg.msg_controllen = CMSG_LEN(sizeof(recv_buf));
+ msg.msg_flags = 0;
+
+retry:
+ ret = lttng_recvmsg_nosigpipe(sock, &msg);
+ if (ret < 0) {
+ if (errno == EINTR) {
+ goto retry;
+ } else {
+ /*
+ * We consider EPIPE and EAGAIN/EWOULDBLOCK as expected.
+ */
+ if (errno == EAGAIN || errno == EWOULDBLOCK) {
+ /*
+ * This can happen in non blocking mode.
+ * Nothing was recv.
+ */
+ ret = 0;
+ goto end;
+ }
+
+ if (errno == EPIPE) {
+ /* Expected error, pass error to caller */
+ DBG3("EPIPE on recvmsg");
+ ret = -1;
+ goto end;
+ }
+
+ /* Unexpected error */
+ PERROR("recvmsg");