Handle stdin pipe closing on us

If xiogen is flooding requests across qarsh and
xdoio decides to stop, we need to handle that gracefully.
Also, making the pipe non-blocking was not a good idea, xdoio
gets the read error EAGAIN and stops there.

3 files changed, 15 insertions, 3 deletions

diff --git a/qarsh.c b/qarsh.c
index 51a876b..2683591 100644
--- a/qarsh.c
+++ b/qarsh.c
@@ -395,6 +395,12 @@ run_remote_cmd(char *cmdline)
 						fprintf(stderr, "ERROR: Received data allow for fd %d\n",
 								qp->qp_dallow.qp_remfd);
 					}
+				} else if (qp->qp_type == QP_RETURNCODE) { /* qarshd hit an error while writing to stdin */
+					fprintf(stderr, "Remote command hit I/O error: %s\n", qp->qp_returncode.qp_strerror);
+					close(fileno(stdin));
+					allowed_in = -1;
+				} else {
+					fprintf(stderr, "Unexpected packet type %s\n", qp_packet_type(qp->qp_type));
 				}
 				qpfree(qp);
 				nset--;
diff --git a/qarshd.c b/qarshd.c
index b911ef7..d686078 100644
--- a/qarshd.c
+++ b/qarshd.c
@@ -117,7 +117,7 @@ run_cmd(const char *cmd)
 	pid_t pid;
 	int pipefds[2], parentfds[3];
 
-	pipe2(pipefds, O_NONBLOCK);
+	pipe(pipefds);
 	childfds[0] = pipefds[1]; parentfds[0] = pipefds[0]; /* stdin */
 	pipe(pipefds);
 	childfds[1] = pipefds[0]; parentfds[1] = pipefds[1]; /* stdout */
@@ -310,6 +310,7 @@ handle_qarsh()
 	sa.sa_mask = sigmask;
 	sa.sa_flags = SA_RESTART;
 	sigaction(SIGCHLD, &sa, NULL);
+	signal(SIGPIPE, SIG_IGN);
 
 	qp = make_qp_data_allow(0, QARSHD_BUFSIZE);
 	send_packet(qoutfd, qp);
@@ -416,7 +417,13 @@ handle_qarsh()
 			if (nfd && FD_ISSET(childfds[0], &wfds)) {
 				/* Child is ready for data on stdin */
 				nbytes = write(childfds[0], buf_in, z_in);
-				if (nbytes == z_in) {
+				if (nbytes == -1) {  /* Don't try writing to the child again */
+					close(childfds[0]);
+					childfds[0] = -1;
+					qp = make_qp_returncode(-1, errno, strerror(errno));
+					send_packet(qoutfd, qp);
+					qpfree(qp);
+				} else if (nbytes == z_in) {
 					z_in = 0;
 					if (eof_in) {
 						close(childfds[0]);
diff --git a/qarshd@.service b/qarshd@.service
index 875f924..408a6f5 100644
--- a/qarshd@.service
+++ b/qarshd@.service
@@ -5,4 +5,3 @@ Description=qarsh Per-Connection Server
 ExecStart=/usr/sbin/qarshd
 StandardInput=socket
 StandardError=journal
-IgnoreSIGPIPE=no