From 691430206f1104b752b0e52386f317e639137788 Mon Sep 17 00:00:00 2001

From: Jan Chaloupka <jchaloup@redhat.com>

Date: Mon, 15 Sep 2014 13:29:39 +0200

Subject: [PATCH] api.c: support for setting multiline values in control files

As of now, libcgroup does not support multiline values setting from configuration files. i.e. values in a form:

net_prio.ifpriomap="lo 7

eth0 66

eth1 5

eth2 4

eth3 3";

Thus, setting of more network interfaces can not be done from configuration file. Or

devices.allow="a *:* w

c 8:* r";

thus setting list of allow devices can not be set as well. The only way is to set it from userspace, e.g.:

# echo "lo 7" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap

# echo "eth 0" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap

# echo "eth 1" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap

# echo "eth 2" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap

# echo "eth 3" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap

This patch allows setting of multiline variables.

How this support works:

Multiline value is broken in lines and each line is set by write (man 2 write) syscall (without bufferring).

This implies change of fopen with open, fclose with close.

There is no control on multiline value, thus "eth0\n  \t\n" can be set. However, setting

of "  \t" will fail as write command returns -1. Thus administrator has to set correct

multiline values.

Tested on virtual machine with fedora and rhel with network interface lo, eth0-eth3. Configuration file:

# cat /etc/cgconfig.conf

group testGroup {

        net_prio {

                net_prio.ifpriomap="lo 7

eth0    66

eth1 5

eth2 4

eth3 3";

        }

}

net_prio has to be created before:

# modprobe netprio_cgroup

# mkdir /sys/fs/cgroup/net_prio

# mount -t cgroup -onet_prio none /sys/fs/cgroup/net_prio

Changelog:

	test of success of strdup call

	free str_val before return (str_val is changing in while cycle,

		thus str_start_val points to the start of str_val before while)

Signed-off-by: Jan Chaloupka <jchaloup@redhat.com>

---

 src/api.c | 50 ++++++++++++++++++++++++++++++++++++++++++++------

 1 file changed, 44 insertions(+), 6 deletions(-)

diff --git a/src/api.c b/src/api.c

index 5751b8f..d6c9d3a 100644

--- a/src/api.c

+++ b/src/api.c

@@ -1495,13 +1495,18 @@ static int cg_create_control_group(const char *path)

  */

 static int cg_set_control_value(char *path, const char *val)

 {

-	FILE *control_file = NULL;

+	int ctl_file;

+	char *str_val;

+	char *str_val_start;

+	char *pos;

+	size_t len;

+

 	if (!cg_test_mounted_fs())

 		return ECGROUPNOTMOUNTED;

-	control_file = fopen(path, "r+e");

+	ctl_file = open(path, O_RDWR | O_CLOEXEC);

-	if (!control_file) {

+	if (ctl_file == -1) {

 		if (errno == EPERM) {

 			/*

 			 * We need to set the correct error value, does the

@@ -1512,6 +1517,7 @@ static int cg_set_control_value(char *path, const char *val)

 			 */

 			char *path_dir_end;

 			char *tasks_path;

+			FILE *control_file;

 			path_dir_end = strrchr(path, '/');

 			if (path_dir_end == NULL)

@@ -1543,15 +1549,47 @@ static int cg_set_control_value(char *path, const char *val)

 		return ECGROUPVALUENOTEXIST;

 	}

-	if (fprintf(control_file, "%s", val) < 0) {

+	/* Split the multiline value into lines. */

+	/* One line is a special case of multiline value. */

+	str_val = strdup(val);

+	if (str_val == NULL) {

 		last_errno = errno;

-		fclose(control_file);

+		close(ctl_file);

 		return ECGOTHER;

 	}

-	if (fclose(control_file) < 0) {

+

+	str_val_start = str_val;

+	pos = str_val;

+

+	do {

+		str_val = pos;

+		pos = strchr(str_val, '\n');

+

+		if (pos) {

+			*pos = '\0';

+			++pos;

+		}

+

+		len = strlen(str_val);

+		if (len > 0) {

+			if (write(ctl_file, str_val, len) == -1) {

+				last_errno = errno;

+				free(str_val_start);

+				close(ctl_file);

+				return ECGOTHER;

+			}

+		} else

+			cgroup_warn("Warning: skipping empty line for %s\n",

+				path);

+	} while(pos);

+

+	if (close(ctl_file)) {

 		last_errno = errno;

+		free(str_val_start);

 		return ECGOTHER;

 	}

+

+	free(str_val_start);

 	return 0;

 }

-- 

1.9.3