From 530a258376cebea6400348e4e343316199230357 Mon Sep 17 00:00:00 2001
From: Mrunal Patel <mrunalp@gmail.com>
Date: Fri, 26 Aug 2016 14:00:30 -0700
Subject: [PATCH] Add a container monitor process

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>
---
 conmon/conmon.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 conmon/conmon.c

diff --git a/conmon/conmon.c b/conmon/conmon.c
new file mode 100644
index 00000000..1a5eacd6
--- /dev/null
+++ b/conmon/conmon.c
@@ -0,0 +1,98 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <errno.h>
+
+#include <glib.h>
+
+#define pexit(fmt, ...)                                                \
+	do {                                                           \
+		fprintf(stderr, "conmon: " fmt " %m\n", ##__VA_ARGS__); \
+		exit(EXIT_FAILURE);                                    \
+	} while (0)                                                   
+
+#define nexit(fmt, ...)                                                \
+	do {                                                           \
+		fprintf(stderr, "conmon: " fmt "\n", ##__VA_ARGS__); \
+		exit(EXIT_FAILURE);                                    \
+	} while (0)                                                   
+
+#define nexit(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) {
+	free(*(void**) p);
+}
+
+#define _cleanup_free_ _cleanup_(freep)
+
+int main(int argc, char *argv[])
+{
+	int ret;
+	const char *cid;
+	char cmd[128];
+	GError *err = NULL;
+	gchar *contents;
+	int cpid = -1;
+	int status;
+	pid_t pid;
+
+	if (argc < 2) {
+		nexit("Run as: conmon <id>");
+	}
+
+	// Get the container id
+	cid = argv[1];
+
+	// 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);
+	ret = system(cmd);
+	if (ret != 0) {
+		nexit("Failed to create container");
+	}
+
+	// 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);
+		g_error_free(err);
+		exit(1);
+	} 
+
+	cpid = atoi(contents);
+	printf("container PID: %d\n", cpid);
+
+	while ((pid = waitpid(-1, &status, 0)) > 0) {
+		printf("PID %d exited\n", pid);
+		if (pid == cpid) {
+			_cleanup_free_ char *status_str = NULL;
+			ret = asprintf(&status_str, "%d", status);
+			if (ret < 0) {
+				pexit("Failed to allocate memory for status");
+			}
+			g_file_set_contents("exit", status_str, strlen(status_str), &err);
+			if (err) {
+				fprintf(stderr, "Failed to write %s to exit file: %s\n", status_str, err->message);
+				g_error_free(err);
+				exit(1);
+			}
+			break;
+		}
+	}
+
+	return EXIT_SUCCESS;
+}