+/*
+ * Recv a message accompanied by fd(s) from a unix socket.
+ *
+ * Returns the size of received data, or negative error value.
+ *
+ * Expect at most "nb_fd" file descriptors. Returns the number of fd
+ * actually received in nb_fd.
+ */
+ssize_t lttcomm_recv_fds_unix_sock(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);
+ char recv_fd[CMSG_SPACE(sizeof_fds)];
+ struct msghdr msg = { 0 };
+ char dummy;
+
+ /* Prepare to receive the structures */
+ iov[0].iov_base = &dummy;
+ iov[0].iov_len = 1;
+ msg.msg_iov = iov;
+ msg.msg_iovlen = 1;
+ msg.msg_control = recv_fd;
+ msg.msg_controllen = sizeof(recv_fd);
+
+ ret = recvmsg(sock, &msg, 0);
+ if (ret < 0) {
+ perror("recvmsg fds");
+ goto end;
+ }
+ if (ret != 1) {
+ fprintf(stderr, "Error: Received %zd bytes, expected %d\n",
+ ret, 1);
+ goto end;
+ }
+ if (msg.msg_flags & MSG_CTRUNC) {
+ fprintf(stderr, "Error: Control message truncated.\n");
+ ret = -1;
+ goto end;
+ }
+ cmsg = CMSG_FIRSTHDR(&msg);
+ if (!cmsg) {
+ fprintf(stderr, "Error: Invalid control message header\n");
+ ret = -1;
+ goto end;
+ }
+ if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
+ fprintf(stderr, "Didn't received any fd\n");
+ ret = -1;
+ goto end;
+ }
+ if (cmsg->cmsg_len != CMSG_LEN(sizeof_fds)) {
+ fprintf(stderr, "Error: Received %zu bytes of ancillary data, expected %zu\n",
+ cmsg->cmsg_len, CMSG_LEN(sizeof_fds));
+ ret = -1;
+ goto end;
+ }
+ memcpy(fds, CMSG_DATA(cmsg), sizeof_fds);
+ ret = sizeof_fds;
+end: