From: Tycho Andersen <tycho.andersen@canonical.com>
Date: Fri, 18 Mar 2016 19:13:17 +0000 (-0600)
Subject: c/r: print criu's stdout when it fails
X-Git-Tag: lxc-2.0.0.rc12~1^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F902%2Fhead;p=thirdparty%2Flxc.git

c/r: print criu's stdout when it fails

In particular, when CRIU fails before it has its log completely initialized
(e.g. if the log directory doesn't exist, or if the argument parser fails),
it prints this to stdout. Let's log that.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
---

diff --git a/src/lxc/criu.c b/src/lxc/criu.c
index a0c671894..7b72c6ec8 100644
--- a/src/lxc/criu.c
+++ b/src/lxc/criu.c
@@ -530,12 +530,12 @@ out_unlock:
 
 // do_restore never returns, the calling process is used as the
 // monitor process. do_restore calls exit() if it fails.
-void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose)
+void do_restore(struct lxc_container *c, int status_pipe, char *directory, bool verbose)
 {
 	pid_t pid;
 	char pidfile[L_tmpnam];
 	struct lxc_handler *handler;
-	int status;
+	int status, pipes[2] = {-1, -1};
 
 	if (!tmpnam(pidfile))
 		goto out;
@@ -561,6 +561,11 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
 
 	resolve_clone_flags(handler);
 
+	if (pipe(pipes) < 0) {
+		SYSERROR("pipe() failed");
+		goto out_fini_handler;
+	}
+
 	pid = fork();
 	if (pid < 0)
 		goto out_fini_handler;
@@ -570,8 +575,20 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
 		struct lxc_rootfs *rootfs;
 		int flags;
 
-		close(pipe);
-		pipe = -1;
+		close(status_pipe);
+		status_pipe = -1;
+
+		close(pipes[0]);
+		pipes[0] = -1;
+		if (dup2(pipes[1], STDERR_FILENO) < 0) {
+			SYSERROR("dup2 failed");
+			goto out_fini_handler;
+		}
+
+		if (dup2(pipes[1], STDOUT_FILENO) < 0) {
+			SYSERROR("dup2 failed");
+			goto out_fini_handler;
+		}
 
 		if (unshare(CLONE_NEWNS))
 			goto out_fini_handler;
@@ -632,15 +649,18 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
 		int ret;
 		char title[2048];
 
+		close(pipes[1]);
+		pipes[1] = -1;
+
 		pid_t w = waitpid(pid, &status, 0);
 		if (w == -1) {
 			SYSERROR("waitpid");
 			goto out_fini_handler;
 		}
 
-		ret = write(pipe, &status, sizeof(status));
-		close(pipe);
-		pipe = -1;
+		ret = write(status_pipe, &status, sizeof(status));
+		close(status_pipe);
+		status_pipe = -1;
 
 		if (sizeof(status) != ret) {
 			SYSERROR("failed to write all of status");
@@ -649,7 +669,18 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
 
 		if (WIFEXITED(status)) {
 			if (WEXITSTATUS(status)) {
-				ERROR("criu process exited %d\n", WEXITSTATUS(status));
+				char buf[4096];
+				int n;
+
+				n = read(pipes[0], buf, sizeof(buf));
+				if (n < 0) {
+					SYSERROR("failed reading from criu stderr");
+					goto out_fini_handler;
+				}
+
+				buf[n] = 0;
+
+				ERROR("criu process exited %d, output:\n%s\n", WEXITSTATUS(status), buf);
 				goto out_fini_handler;
 			} else {
 				int ret;
@@ -679,6 +710,8 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
 			goto out_fini_handler;
 		}
 
+		close(pipes[0]);
+
 		/*
 		 * See comment in lxcapi_start; we don't care if these
 		 * fail because it's just a beauty thing. We just
@@ -695,17 +728,22 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
 	}
 
 out_fini_handler:
+	if (pipes[0] >= 0)
+		close(pipes[0]);
+	if (pipes[1] >= 0)
+		close(pipes[1]);
+
 	lxc_fini(c->name, handler);
 	if (unlink(pidfile) < 0 && errno != ENOENT)
 		SYSERROR("unlinking pidfile failed");
 
 out:
-	if (pipe >= 0) {
+	if (status_pipe >= 0) {
 		status = 1;
-		if (write(pipe, &status, sizeof(status)) != sizeof(status)) {
+		if (write(status_pipe, &status, sizeof(status)) != sizeof(status)) {
 			SYSERROR("writing status failed");
 		}
-		close(pipe);
+		close(status_pipe);
 	}
 
 	exit(1);