[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: Johannes Berg <johannes@sipsolutions.net> Acked-by: Patrick McHardy <kaber@trash.net> Acked-by: Jamal Hadi Salim <hadi@cyberus.ca> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -161,6 +161,7 @@ extern struct sock *netlink_kernel_create(int unit, unsigned int groups,
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void (*input)(struct sock *sk, int len),
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struct mutex *cb_mutex,
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struct module *module);
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extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);
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extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
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extern int netlink_has_listeners(struct sock *sk, unsigned int group);
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extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 pid, int nonblock);
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@ -62,6 +62,7 @@
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#include <net/netlink.h>
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#define NLGRPSZ(x) (ALIGN(x, sizeof(unsigned long) * 8) / 8)
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#define NLGRPLONGS(x) (NLGRPSZ(x)/sizeof(unsigned long))
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struct netlink_sock {
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/* struct sock has to be the first member of netlink_sock */
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@ -314,10 +315,12 @@ netlink_update_listeners(struct sock *sk)
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unsigned long mask;
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unsigned int i;
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for (i = 0; i < NLGRPSZ(tbl->groups)/sizeof(unsigned long); i++) {
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for (i = 0; i < NLGRPLONGS(tbl->groups); i++) {
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mask = 0;
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sk_for_each_bound(sk, node, &tbl->mc_list)
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mask |= nlk_sk(sk)->groups[i];
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sk_for_each_bound(sk, node, &tbl->mc_list) {
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if (i < NLGRPLONGS(nlk_sk(sk)->ngroups))
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mask |= nlk_sk(sk)->groups[i];
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}
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tbl->listeners[i] = mask;
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}
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/* this function is only called with the netlink table "grabbed", which
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@ -555,26 +558,37 @@ netlink_update_subscriptions(struct sock *sk, unsigned int subscriptions)
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nlk->subscriptions = subscriptions;
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}
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static int netlink_alloc_groups(struct sock *sk)
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static int netlink_realloc_groups(struct sock *sk)
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{
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struct netlink_sock *nlk = nlk_sk(sk);
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unsigned int groups;
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unsigned long *new_groups;
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int err = 0;
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netlink_lock_table();
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netlink_table_grab();
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groups = nl_table[sk->sk_protocol].groups;
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if (!nl_table[sk->sk_protocol].registered)
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if (!nl_table[sk->sk_protocol].registered) {
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err = -ENOENT;
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netlink_unlock_table();
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goto out_unlock;
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}
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if (err)
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return err;
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if (nlk->ngroups >= groups)
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goto out_unlock;
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nlk->groups = kzalloc(NLGRPSZ(groups), GFP_KERNEL);
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if (nlk->groups == NULL)
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return -ENOMEM;
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new_groups = krealloc(nlk->groups, NLGRPSZ(groups), GFP_ATOMIC);
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if (new_groups == NULL) {
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err = -ENOMEM;
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goto out_unlock;
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}
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memset((char*)new_groups + NLGRPSZ(nlk->ngroups), 0,
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NLGRPSZ(groups) - NLGRPSZ(nlk->ngroups));
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nlk->groups = new_groups;
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nlk->ngroups = groups;
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return 0;
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out_unlock:
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netlink_table_ungrab();
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return err;
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}
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static int netlink_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
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@ -591,11 +605,9 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, int addr_len
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if (nladdr->nl_groups) {
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if (!netlink_capable(sock, NL_NONROOT_RECV))
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return -EPERM;
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if (nlk->groups == NULL) {
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err = netlink_alloc_groups(sk);
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if (err)
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return err;
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}
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err = netlink_realloc_groups(sk);
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if (err)
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return err;
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}
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if (nlk->pid) {
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@ -839,10 +851,18 @@ retry:
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int netlink_has_listeners(struct sock *sk, unsigned int group)
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{
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int res = 0;
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unsigned long *listeners;
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BUG_ON(!(nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET));
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rcu_read_lock();
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listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);
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if (group - 1 < nl_table[sk->sk_protocol].groups)
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res = test_bit(group - 1, nl_table[sk->sk_protocol].listeners);
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res = test_bit(group - 1, listeners);
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rcu_read_unlock();
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return res;
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}
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EXPORT_SYMBOL_GPL(netlink_has_listeners);
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@ -1037,11 +1057,9 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
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if (!netlink_capable(sock, NL_NONROOT_RECV))
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return -EPERM;
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if (nlk->groups == NULL) {
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err = netlink_alloc_groups(sk);
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if (err)
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return err;
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}
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err = netlink_realloc_groups(sk);
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if (err)
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return err;
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if (!val || val - 1 >= nlk->ngroups)
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return -EINVAL;
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netlink_table_grab();
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@ -1328,6 +1346,46 @@ out_sock_release:
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return NULL;
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}
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/**
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* netlink_change_ngroups - change number of multicast groups
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*
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* This changes the number of multicast groups that are available
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* on a certain netlink family. Note that it is not possible to
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* change the number of groups to below 32.
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*
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* @sk: The kernel netlink socket, as returned by netlink_kernel_create().
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* @groups: The new number of groups.
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*/
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int netlink_change_ngroups(struct sock *sk, unsigned int groups)
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{
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unsigned long *listeners, *old = NULL;
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struct netlink_table *tbl = &nl_table[sk->sk_protocol];
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int err = 0;
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if (groups < 32)
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groups = 32;
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netlink_table_grab();
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if (NLGRPSZ(tbl->groups) < NLGRPSZ(groups)) {
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listeners = kzalloc(NLGRPSZ(groups), GFP_ATOMIC);
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if (!listeners) {
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err = -ENOMEM;
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goto out_ungrab;
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}
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old = tbl->listeners;
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memcpy(listeners, old, NLGRPSZ(tbl->groups));
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rcu_assign_pointer(tbl->listeners, listeners);
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}
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tbl->groups = groups;
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out_ungrab:
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netlink_table_ungrab();
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synchronize_rcu();
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kfree(old);
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return err;
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}
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EXPORT_SYMBOL(netlink_change_ngroups);
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void netlink_set_nonroot(int protocol, unsigned int flags)
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{
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if ((unsigned int)protocol < MAX_LINKS)
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