conmon: Add control fifo for terminal resize handling

Signed-off-by: Mrunal Patel <mpatel@redhat.com>

conmon/conmon.c

@@ -12,10 +12,12 @@
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <sys/un.h>
+#include <sys/stat.h>
 #include <sys/wait.h>
 #include <sys/eventfd.h>
 #include <sys/stat.h>
 #include <sys/uio.h>
+#include <sys/ioctl.h>
 #include <syslog.h>
 #include <unistd.h>
 
@@ -439,6 +441,7 @@ int main(int argc, char *argv[])
 	char cwd[PATH_MAX];
 	char default_pid_file[PATH_MAX];
 	char attach_sock_path[PATH_MAX];
+	char ctl_fifo_path[PATH_MAX];
 	GError *err = NULL;
 	_cleanup_free_ char *contents;
 	int cpid = -1;
@@ -798,6 +801,40 @@ int main(int argc, char *argv[])
 			pexit("Failed to listen on attach socket: %s", attach_sock_path);
 	}
 
+	/* Setup fifo for reading in terminal resize and other stdio control messages */
+	_cleanup_close_ int ctlfd = -1;
+	_cleanup_close_ int dummyfd = -1;
+	int ctl_msg_type = -1;
+	int height = -1;
+	int width = -1;
+	struct winsize ws;
+	#define CTLBUFSZ 200
+	char ctlbuf[CTLBUFSZ];
+	char *readptr = ctlbuf;
+	int readsz = CTLBUFSZ - 1;
+	int cp_rem = 0;
+	if (!exec) {
+		snprintf(ctl_fifo_path, PATH_MAX, "%s/ctl", bundle_path);
+		ninfo("ctl fifo path: %s", ctl_fifo_path);
+
+		if (mkfifo(ctl_fifo_path, 0666) == -1)
+			pexit("Failed to mkfifo at %s", ctl_fifo_path);
+
+		ctlfd = open(ctl_fifo_path, O_RDONLY|O_NONBLOCK|O_CLOEXEC);
+		if (ctlfd == -1)
+			pexit("Failed to open control fifo");
+
+		/*
+		 * Open a dummy writer to prevent getting flood of POLLHUPs when
+		 * last writer closes.
+		 */
+		dummyfd = open(ctl_fifo_path, O_WRONLY|O_CLOEXEC);
+		if (dummyfd == -1)
+			pexit("Failed to open dummy writer for fifo");
+
+		ninfo("ctlfd: %d", ctlfd);
+	}
+
 	/* Send the container pid back to parent */
 	if (sync_pipe_fd > 0 && !exec) {
 		len = snprintf(buf, BUF_SIZE, "{\"pid\": %d}\n", cpid);
@@ -870,6 +907,13 @@ int main(int argc, char *argv[])
 			pexit("Failed to add attach socket fd to epoll");
 	}
 
+	/* Add control fifo fd to epoll */
+	if (ctlfd > 0) {
+		ev.data.fd = ctlfd;
+		if (epoll_ctl(epfd, EPOLL_CTL_ADD, ev.data.fd, &ev) < 0)
+			pexit("Failed to add control fifo fd to epoll");
+	}
+
 	/* Log all of the container's output. */
 	while (num_stdio_fds > 0) {
 		int ready = epoll_wait(epfd, evlist, MAX_EVENTS, -1);
@@ -903,6 +947,59 @@ int main(int argc, char *argv[])
 						pexit("Failed to add client socket fd to epoll");
 					}
 					ninfo("Accepted connection");
+				} else if (!exec && evlist[i].data.fd == ctlfd) {
+					num_read = read(ctlfd, readptr, readsz);
+					if (num_read <= 0) {
+						nwarn("Failed to read from control fd");
+						continue;
+					}
+					readptr[num_read] = '\0';
+					ninfo("Got ctl message: %s\n", ctlbuf);
+
+					char *beg = ctlbuf;
+					char *newline = strchrnul(beg, '\n');
+					/* Process each message which ends with a line */
+					while (*newline != '\0') {
+						ret = sscanf(ctlbuf, "%d %d %d\n", &ctl_msg_type, &height, &width);
+						if (ret != 3) {
+							nwarn("Failed to sscanf message");
+							continue;
+						}
+						ninfo("Message type: %d, Height: %d, Width: %d", ctl_msg_type, height, width);
+						ret = ioctl(masterfd_stdout, TIOCGWINSZ, &ws);
+						ninfo("Existing size: %d %d", ws.ws_row, ws.ws_col);
+						ws.ws_row = height;
+						ws.ws_col = width;
+						ret = ioctl(masterfd_stdout, TIOCSWINSZ, &ws);
+						if (ret == -1) {
+							nwarn("Failed to set process pty terminal size");
+						}
+						beg = newline + 1;
+						newline = strchrnul(beg, '\n');
+					}
+					if (num_read == (CTLBUFSZ - 1) && beg == ctlbuf) {
+						/*
+						 * We did not find a newline in the entire buffer.
+						 * This shouldn't happen as our buffer is larger than
+						 * the message that we expect to receive.
+						 */
+						nwarn("Could not find newline in entire buffer\n");
+					} else if (*beg == '\0') {
+						/* We exhausted all messages that were complete */
+						readptr = ctlbuf;
+						readsz = CTLBUFSZ - 1;
+					} else {
+						/*
+						 * We copy remaining data to beginning of buffer
+						 * and advance readptr after that.
+						 */
+						cp_rem = 0;
+						do {
+							ctlbuf[cp_rem++] = *beg++;
+						} while (*beg != '\0');
+						readptr = ctlbuf + cp_rem;
+						readsz = CTLBUFSZ - 1 - cp_rem;
+					}
 				} else {
 					num_read = read(masterfd, buf, BUF_SIZE);
 					if (num_read <= 0)
@@ -932,6 +1029,10 @@ int main(int argc, char *argv[])
 					}
 				}
 			} else if (evlist[i].events & (EPOLLHUP | EPOLLERR)) {
+				if (!exec && evlist[i].data.fd == ctlfd) {
+					ninfo("Remote writer to control fd closed");
+					continue;
+				}
 				printf("closing fd %d\n", evlist[i].data.fd);
 				if (close(evlist[i].data.fd) < 0)
 					pexit("close");