Add support for console handling

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>

conmon/conmon.c

@@ -1,10 +1,15 @@
 #define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/epoll.h>
 #include <sys/prctl.h>
 #include <sys/wait.h>
-#include <errno.h>
+#include <termios.h>
+#include <unistd.h>
 
 #include <glib.h>
 
@@ -20,52 +25,99 @@
 		exit(EXIT_FAILURE);                                            \
 	} while (0)
 
-#define nexit(fmt, ...)                                                \
+#define nwarn(fmt, ...)                                                        \
 	do {                                                                   \
 		fprintf(stderr, "conmon: " fmt "\n", ##__VA_ARGS__);           \
-		exit(EXIT_FAILURE);                                    \
 	} while (0)
 
 #define _cleanup_(x) __attribute__((cleanup(x)))
 
-static inline void freep(void *p) {
+static inline void freep(void *p) { free(*(void **)p); }
-	free(*(void**) p);
+
+static inline void closep(int *fd) {
+	if (*fd >= 0)
+		close(*fd);
+	*fd = -1;
 }
 
 #define _cleanup_free_ _cleanup_(freep)
+#define _cleanup_close_ _cleanup_(closep)
+
+struct termios tty_orig;
+
+static void tty_restore(void)
+{
+	if (tcsetattr(STDIN_FILENO, TCSANOW, &tty_orig) == -1)
+		pexit("tcsetattr");
+}
+
+#define BUF_SIZE 256
+#define CMD_SIZE 1024
+#define MAX_EVENTS 10
 
 int main(int argc, char *argv[])
 {
 	int ret;
 	const char *cid;
-	char cmd[128];
+	char cmd[CMD_SIZE];
 	GError *err = NULL;
-	gchar *contents;
+	_cleanup_free_ char *contents;
 	int cpid = -1;
 	int status;
 	pid_t pid;
+	_cleanup_close_ int mfd = -1;
+	_cleanup_close_ int epfd = -1;
+	char slname[BUF_SIZE];
+	char buf[BUF_SIZE];
+	int num_read;
+	struct termios t;
+	struct epoll_event ev;
+	struct epoll_event evlist[MAX_EVENTS];
 
 	if (argc < 2) {
 		nexit("Run as: conmon <id>");
 	}
 
-	// Get the container id
+	/* Get the container id */
 	cid = argv[1];
 
-	// Set self as subreaper so we can wait for container process
+	/*
-	// and return its exit code.
+	 * Set self as subreaper so we can wait for container process
+	 * and return its exit code.
+	 */
 	ret = prctl(PR_SET_CHILD_SUBREAPER, 1, 0, 0, 0);
 	if (ret != 0) {
 		pexit("Failed to set as subreaper");
 	}
 
-	snprintf(cmd, 128, "runc create %s --pid-file pidfile", cid);
+	/* Open the master pty */
+	mfd = open("/dev/ptmx", O_RDWR | O_NOCTTY);
+	if (mfd < 0)
+		pexit("Failed to open console master pty");
+
+	/* Grant access to the slave pty */
+	if (grantpt(mfd) == -1)
+		pexit("Failed to grant access to slave pty");
+
+	/* Unlock the slave pty */
+	if (unlockpt(mfd) == -1) {             /* Unlock slave pty */
+		pexit("Failed to unlock the slave pty");
+	}
+
+	/* Get the slave pty name */
+	ret = ptsname_r(mfd, slname, BUF_SIZE);
+	if (ret != 0) {
+		pexit("Failed to get the slave pty name");
+	}
+
+	/* Create the container */
+	snprintf(cmd, CMD_SIZE, "runc create %s --pid-file pidfile --console %s", cid, slname);
 	ret = system(cmd);
 	if (ret != 0) {
 		nexit("Failed to create container");
 	}
 
-	// Read the pid so we can wait for the process to exit
+	/* Read the pid so we can wait for the process to exit */
 	g_file_get_contents("pidfile", &contents, NULL, &err);
 	if (err) {
 		fprintf(stderr, "Failed to read pidfile: %s\n", err->message);
@@ -76,6 +128,75 @@ int main(int argc, char *argv[])
 	cpid = atoi(contents);
 	printf("container PID: %d\n", cpid);
 
+	/* Save exiting termios settings */
+	if (tcgetattr(STDIN_FILENO, &tty_orig) == -1)
+		pexit("tcegetattr");
+
+	/* Settings for raw mode */
+	t.c_lflag &= ~(ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHONL | IEXTEN);
+	t.c_iflag &= ~(BRKINT | ICRNL | IGNBRK | IGNCR | INLCR | INPCK |
+		       ISTRIP | IXON | IXOFF | IGNPAR | PARMRK);
+	t.c_oflag &= ~OPOST;
+	t.c_cc[VMIN] = 1;
+	t.c_cc[VTIME] = 0;
+
+	/* Set terminal to raw mode */
+	if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &t) == -1)
+		pexit("tcsetattr");
+
+	/* Setup terminal restore on exit */
+	if (atexit(tty_restore) != 0)
+		pexit("atexit");
+
+	epfd = epoll_create(5);
+	if (epfd < 0)
+		pexit("epoll_create");
+	ev.events = EPOLLIN;
+	ev.data.fd = STDIN_FILENO;
+	if (epoll_ctl(epfd, EPOLL_CTL_ADD, STDIN_FILENO, &ev) < 0) {
+		pexit("Failed to add stdin to epoll");
+	}
+	ev.data.fd = mfd;
+	if (epoll_ctl(epfd, EPOLL_CTL_ADD, mfd, &ev) < 0) {
+		pexit("Failed to add console master fd to epoll");
+	}
+
+	/* Copy data back and forth between STDIN and master fd */
+	while (true) {
+		int ready = epoll_wait(epfd, evlist, MAX_EVENTS, -1);
+		for (int i = 0; i < ready; i++) {
+			if (evlist[i].events & EPOLLIN) {
+				if (evlist[i].data.fd == STDIN_FILENO) {
+					num_read = read(STDIN_FILENO, buf, BUF_SIZE);
+					if (num_read <= 0)
+						goto out;
+
+					if (write(mfd, buf, num_read) != num_read) {
+						nwarn("partial/failed write (masterFd)");
+						goto out;
+					}
+				} else if (evlist[i].data.fd == mfd) {
+					num_read = read(mfd, buf, BUF_SIZE);
+					if (num_read <= 0)
+						goto out;
+
+					if (write(STDOUT_FILENO, buf, num_read) != num_read) {
+						nwarn("partial/failed write (STDOUT_FILENO)");
+						goto out;
+					}
+				}
+			} else if (evlist[i].events & (EPOLLHUP | EPOLLERR)) {
+				printf("closing fd %d\n", evlist[i].data.fd);
+				if (close(evlist[i].data.fd) < 0)
+					pexit("close");
+				goto out;
+			}
+		}
+	}
+out:
+	tty_restore();
+
+	/* Wait for the container process and record its exit code */
 	while ((pid = waitpid(-1, &status, 0)) > 0) {
 		printf("PID %d exited\n", pid);
 		if (pid == cpid) {