Commit ce7bc3bf authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
Browse files

[TCP]: Restrict congestion control choices. 



Allow normal users to only choose among a restricted set of congestion
control choices.  The default is reno and what ever has been configured
as default. But the policy can be changed by administrator at any time.

For example, to allow any choice:
    cp /proc/sys/net/ipv4/tcp_available_congestion_control \
       /proc/sys/net/ipv4/tcp_allowed_congestion_control

Signed-off-by: default avatarStephen Hemminger <shemminger@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3ff825b2

Documentation/networking/ip-sysctl.txt

+6 −0
Original line number Diff line number Diff line
@@ -351,6 +351,12 @@ tcp_frto - BOOLEAN 
	where packet loss is typically due to random radio interference

	rather than intermediate router congestion.



tcp_allowed_congestion_control - STRING

	Show/set the congestion control choices available to non-privileged

	processes. The list is a subset of those listed in

	tcp_available_congestion_control.

	Default is "reno" and the default setting (tcp_congestion_control).



tcp_available_congestion_control - STRING

	Shows the available congestion control choices that are registered.

	More congestion control algorithms may be available as modules,

include/linux/sysctl.h

+1 −0
Original line number Diff line number Diff line
@@ -427,6 +427,7 @@ enum 
	NET_CIPSOV4_RBM_OPTFMT=120,

	NET_CIPSOV4_RBM_STRICTVALID=121,

	NET_TCP_AVAIL_CONG_CONTROL=122,

	NET_TCP_ALLOWED_CONG_CONTROL=123,

};



enum {

include/net/tcp.h

+3 −0
Original line number Diff line number Diff line
@@ -625,6 +625,7 @@ enum tcp_ca_event { 


struct tcp_congestion_ops {

	struct list_head	list;

	int	non_restricted;



	/* initialize private data (optional) */

	void (*init)(struct sock *sk);
@@ -663,6 +664,8 @@ extern void tcp_cleanup_congestion_control(struct sock *sk); 
extern int tcp_set_default_congestion_control(const char *name);

extern void tcp_get_default_congestion_control(char *name);

extern void tcp_get_available_congestion_control(char *buf, size_t len);

extern void tcp_get_allowed_congestion_control(char *buf, size_t len);

extern int tcp_set_allowed_congestion_control(char *allowed);

extern int tcp_set_congestion_control(struct sock *sk, const char *name);

extern void tcp_slow_start(struct tcp_sock *tp);

net/ipv4/sysctl_net_ipv4.c

+52 −0
Original line number Diff line number Diff line
@@ -146,6 +146,50 @@ static int proc_tcp_available_congestion_control(ctl_table *ctl, 
	return ret;

}



static int proc_allowed_congestion_control(ctl_table *ctl,

					   int write, struct file * filp,

					   void __user *buffer, size_t *lenp,

					   loff_t *ppos)

{

	ctl_table tbl = { .maxlen = TCP_CA_BUF_MAX };

	int ret;



	tbl.data = kmalloc(tbl.maxlen, GFP_USER);

	if (!tbl.data)

		return -ENOMEM;



	tcp_get_allowed_congestion_control(tbl.data, tbl.maxlen);

	ret = proc_dostring(&tbl, write, filp, buffer, lenp, ppos);

	if (write && ret == 0)

		ret = tcp_set_allowed_congestion_control(tbl.data);

	kfree(tbl.data);

	return ret;

}



static int strategy_allowed_congestion_control(ctl_table *table, int __user *name,

					       int nlen, void __user *oldval,

					       size_t __user *oldlenp,

					       void __user *newval, size_t newlen,

					       void **context)

{

	ctl_table tbl = { .maxlen = TCP_CA_BUF_MAX };

	int ret;



	tbl.data = kmalloc(tbl.maxlen, GFP_USER);

	if (!tbl.data)

		return -ENOMEM;



	tcp_get_available_congestion_control(tbl.data, tbl.maxlen);

	ret = sysctl_string(&tbl, name, nlen, oldval, oldlenp, newval, newlen,

			    context);

	if (ret == 0 && newval && newlen)

		ret = tcp_set_allowed_congestion_control(tbl.data);

	kfree(tbl.data);



	return ret;



}



ctl_table ipv4_table[] = {

        {

		.ctl_name	= NET_IPV4_TCP_TIMESTAMPS,
@@ -755,6 +799,14 @@ ctl_table ipv4_table[] = { 
		.mode		= 0444,

		.proc_handler   = &proc_tcp_available_congestion_control,

	},

	{

		.ctl_name	= NET_TCP_ALLOWED_CONG_CONTROL,

		.procname	= "tcp_allowed_congestion_control",

		.maxlen		= TCP_CA_BUF_MAX,

		.mode		= 0644,

		.proc_handler   = &proc_allowed_congestion_control,

		.strategy	= &strategy_allowed_congestion_control,

	},

	{ .ctl_name = 0 }

};

net/ipv4/tcp_cong.c

+63 −0
Original line number Diff line number Diff line
@@ -123,6 +123,7 @@ int tcp_set_default_congestion_control(const char *name) 
#endif



	if (ca) {

		ca->non_restricted = 1;	/* default is always allowed */

		list_move(&ca->list, &tcp_cong_list);

		ret = 0;

	}
@@ -168,6 +169,64 @@ void tcp_get_default_congestion_control(char *name) 
	rcu_read_unlock();

}



/* Built list of non-restricted congestion control values */

void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)

{

	struct tcp_congestion_ops *ca;

	size_t offs = 0;



	*buf = '\0';

	rcu_read_lock();

	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {

		if (!ca->non_restricted)

			continue;

		offs += snprintf(buf + offs, maxlen - offs,

				 "%s%s",

				 offs == 0 ? "" : " ", ca->name);



	}

	rcu_read_unlock();

}



/* Change list of non-restricted congestion control */

int tcp_set_allowed_congestion_control(char *val)

{

	struct tcp_congestion_ops *ca;

	char *clone, *name;

	int ret = 0;



	clone = kstrdup(val, GFP_USER);

	if (!clone)

		return -ENOMEM;



	spin_lock(&tcp_cong_list_lock);

	/* pass 1 check for bad entries */

	while ((name = strsep(&clone, " ")) && *name) {

		ca = tcp_ca_find(name);

		if (!ca) {

			ret = -ENOENT;

			goto out;

		}

	}



	/* pass 2 clear */

	list_for_each_entry_rcu(ca, &tcp_cong_list, list)

		ca->non_restricted = 0;



	/* pass 3 mark as allowed */

	while ((name = strsep(&val, " ")) && *name) {

		ca = tcp_ca_find(name);

		WARN_ON(!ca);

		if (ca)

			ca->non_restricted = 1;

	}

out:

	spin_unlock(&tcp_cong_list_lock);



	return ret;

}





/* Change congestion control for socket */

int tcp_set_congestion_control(struct sock *sk, const char *name)

{
@@ -183,6 +242,9 @@ int tcp_set_congestion_control(struct sock *sk, const char *name) 
	if (!ca)

		err = -ENOENT;



	else if (!(ca->non_restricted || capable(CAP_NET_ADMIN)))

		err = -EPERM;



	else if (!try_module_get(ca->owner))

		err = -EBUSY;
@@ -284,6 +346,7 @@ EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd); 


struct tcp_congestion_ops tcp_reno = {

	.name		= "reno",

	.non_restricted = 1,

	.owner		= THIS_MODULE,

	.ssthresh	= tcp_reno_ssthresh,

	.cong_avoid	= tcp_reno_cong_avoid,

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