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Message-Id: <1184769287.4200.1.camel@johannes.berg>
Date: Wed, 18 Jul 2007 16:34:47 +0200
From: Johannes Berg <johannes@...solutions.net>
To: David Miller <davem@...emloft.net>
Cc: netdev@...r.kernel.org, Patrick McHardy <kaber@...sh.net>,
Zhang Rui <rui.zhang@...el.com>, jamal <hadi@...erus.ca>
Subject: [PATCH v2 1/3] 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@...solutions.net>
---
Changes: incorporate Patrick's comments, add kernel-doc
include/linux/netlink.h | 1
net/netlink/af_netlink.c | 106 ++++++++++++++++++++++++++++++++++++-----------
2 files changed, 83 insertions(+), 24 deletions(-)
--- wireless-dev.orig/net/netlink/af_netlink.c 2007-07-18 15:09:02.952900849 +0200
+++ wireless-dev/net/netlink/af_netlink.c 2007-07-18 16:33:33.691236687 +0200
@@ -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)
- mask |= nlk_sk(sk)->groups[i];
+ 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
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)
@@ -591,11 +605,9 @@ static int netlink_bind(struct socket *s
if (nladdr->nl_groups) {
if (!netlink_capable(sock, NL_NONROOT_RECV))
return -EPERM;
- if (nlk->groups == NULL) {
- err = netlink_alloc_groups(sk);
- if (err)
- return err;
- }
+ err = netlink_realloc_groups(sk);
+ if (err)
+ return err;
}
if (nlk->pid) {
@@ -839,10 +851,18 @@ retry:
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 soc
if (!netlink_capable(sock, NL_NONROOT_RECV))
return -EPERM;
- if (nlk->groups == NULL) {
- err = netlink_alloc_groups(sk);
- if (err)
- return err;
- }
+ err = netlink_realloc_groups(sk);
+ if (err)
+ return err;
if (!val || val - 1 >= nlk->ngroups)
return -EINVAL;
netlink_table_grab();
@@ -1328,6 +1346,46 @@ out_sock_release:
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)
--- wireless-dev.orig/include/linux/netlink.h 2007-07-18 15:08:48.132900849 +0200
+++ wireless-dev/include/linux/netlink.h 2007-07-18 16:31:43.061236687 +0200
@@ -161,6 +161,7 @@ extern struct sock *netlink_kernel_creat
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);
-
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