Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b4ff4f04 authored by Johannes Berg's avatar Johannes Berg Committed by David S. Miller
Browse files

[NETLINK]: allocate group bitmaps dynamically 



Allow changing the number of groups for a netlink family
after it has been created, use RCU to protect the listeners
bitmap keeping netlink_has_listeners() lock-free.

Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Acked-by: default avatarPatrick McHardy <kaber@trash.net>
Acked-by: default avatarJamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c81de6ad

include/linux/netlink.h

+1 −0
Original line number Diff line number Diff line
@@ -161,6 +161,7 @@ extern struct sock *netlink_kernel_create(int unit, unsigned int groups, 
					  void (*input)(struct sock *sk, int len),

					  struct mutex *cb_mutex,

					  struct module *module);

extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);

extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);

extern int netlink_has_listeners(struct sock *sk, unsigned int group);

extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 pid, int nonblock);

net/netlink/af_netlink.c

+82 −24
Original line number Diff line number Diff line
@@ -62,6 +62,7 @@ 
#include <net/netlink.h>



#define NLGRPSZ(x)	(ALIGN(x, sizeof(unsigned long) * 8) / 8)

#define NLGRPLONGS(x)	(NLGRPSZ(x)/sizeof(unsigned long))



struct netlink_sock {

	/* struct sock has to be the first member of netlink_sock */
@@ -314,10 +315,12 @@ netlink_update_listeners(struct sock *sk) 
	unsigned long mask;

	unsigned int i;



	for (i = 0; i < NLGRPSZ(tbl->groups)/sizeof(unsigned long); i++) {

	for (i = 0; i < NLGRPLONGS(tbl->groups); i++) {

		mask = 0;

		sk_for_each_bound(sk, node, &tbl->mc_list)

		sk_for_each_bound(sk, node, &tbl->mc_list) {

			if (i < NLGRPLONGS(nlk_sk(sk)->ngroups))

				mask |= nlk_sk(sk)->groups[i];

		}

		tbl->listeners[i] = mask;

	}

	/* this function is only called with the netlink table "grabbed", which
@@ -555,26 +558,37 @@ netlink_update_subscriptions(struct sock *sk, unsigned int subscriptions) 
	nlk->subscriptions = subscriptions;

}



static int netlink_alloc_groups(struct sock *sk)

static int netlink_realloc_groups(struct sock *sk)

{

	struct netlink_sock *nlk = nlk_sk(sk);

	unsigned int groups;

	unsigned long *new_groups;

	int err = 0;



	netlink_lock_table();

	netlink_table_grab();



	groups = nl_table[sk->sk_protocol].groups;

	if (!nl_table[sk->sk_protocol].registered)

	if (!nl_table[sk->sk_protocol].registered) {

		err = -ENOENT;

	netlink_unlock_table();

		goto out_unlock;

	}



	if (err)

		return err;

	if (nlk->ngroups >= groups)

		goto out_unlock;



	nlk->groups = kzalloc(NLGRPSZ(groups), GFP_KERNEL);

	if (nlk->groups == NULL)

		return -ENOMEM;

	new_groups = krealloc(nlk->groups, NLGRPSZ(groups), GFP_ATOMIC);

	if (new_groups == NULL) {

		err = -ENOMEM;

		goto out_unlock;

	}

	memset((char*)new_groups + NLGRPSZ(nlk->ngroups), 0,

	       NLGRPSZ(groups) - NLGRPSZ(nlk->ngroups));



	nlk->groups = new_groups;

	nlk->ngroups = groups;

	return 0;

 out_unlock:

	netlink_table_ungrab();

	return err;

}



static int netlink_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
@@ -591,12 +605,10 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, int addr_len 
	if (nladdr->nl_groups) {

		if (!netlink_capable(sock, NL_NONROOT_RECV))

			return -EPERM;

		if (nlk->groups == NULL) {

			err = netlink_alloc_groups(sk);

		err = netlink_realloc_groups(sk);

		if (err)

			return err;

	}

	}



	if (nlk->pid) {

		if (nladdr->nl_pid != nlk->pid)
@@ -839,10 +851,18 @@ int netlink_unicast(struct sock *ssk, struct sk_buff *skb, u32 pid, int nonblock 
int netlink_has_listeners(struct sock *sk, unsigned int group)

{

	int res = 0;

	unsigned long *listeners;



	BUG_ON(!(nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET));



	rcu_read_lock();

	listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);



	if (group - 1 < nl_table[sk->sk_protocol].groups)

		res = test_bit(group - 1, nl_table[sk->sk_protocol].listeners);

		res = test_bit(group - 1, listeners);



	rcu_read_unlock();



	return res;

}

EXPORT_SYMBOL_GPL(netlink_has_listeners);
@@ -1037,11 +1057,9 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname, 


		if (!netlink_capable(sock, NL_NONROOT_RECV))

			return -EPERM;

		if (nlk->groups == NULL) {

			err = netlink_alloc_groups(sk);

		err = netlink_realloc_groups(sk);

		if (err)

			return err;

		}

		if (!val || val - 1 >= nlk->ngroups)

			return -EINVAL;

		netlink_table_grab();
@@ -1328,6 +1346,46 @@ netlink_kernel_create(int unit, unsigned int groups, 
	return NULL;

}



/**

 * netlink_change_ngroups - change number of multicast groups

 *

 * This changes the number of multicast groups that are available

 * on a certain netlink family. Note that it is not possible to

 * change the number of groups to below 32.

 *

 * @sk: The kernel netlink socket, as returned by netlink_kernel_create().

 * @groups: The new number of groups.

 */

int netlink_change_ngroups(struct sock *sk, unsigned int groups)

{

	unsigned long *listeners, *old = NULL;

	struct netlink_table *tbl = &nl_table[sk->sk_protocol];

	int err = 0;



	if (groups < 32)

		groups = 32;



	netlink_table_grab();

	if (NLGRPSZ(tbl->groups) < NLGRPSZ(groups)) {

		listeners = kzalloc(NLGRPSZ(groups), GFP_ATOMIC);

		if (!listeners) {

			err = -ENOMEM;

			goto out_ungrab;

		}

		old = tbl->listeners;

		memcpy(listeners, old, NLGRPSZ(tbl->groups));

		rcu_assign_pointer(tbl->listeners, listeners);

	}

	tbl->groups = groups;



 out_ungrab:

	netlink_table_ungrab();

	synchronize_rcu();

	kfree(old);

	return err;

}

EXPORT_SYMBOL(netlink_change_ngroups);



void netlink_set_nonroot(int protocol, unsigned int flags)

{

	if ((unsigned int)protocol < MAX_LINKS)