netdev - [PATCH] netlink: allocate group bitmaps dynamically

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Date:	Tue, 03 Jul 2007 12:08:49 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	hadi@...erus.ca, Zhang Rui <rui.zhang@...el.com>,
	netdev@...r.kernel.org,
	"linux-acpi@...r" <linux-acpi@...r.kernel.org>, lenb@...nel.org,
	Thomas Graf <tgraf@...g.ch>
Subject: [PATCH] netlink: allocate group bitmaps dynamically

Allow changing the number of groups for a netlink family
after it has been created.

Signed-off-by: Johannes Berg <johannes@...solutions.net>

---
 include/linux/netlink.h  |    1 
 net/netlink/af_netlink.c |   61 +++++++++++++++++++++++++++++++++++------------
 2 files changed, 47 insertions(+), 15 deletions(-)

--- wireless-dev.orig/net/netlink/af_netlink.c	2007-07-03 00:10:31.617889695 +0200
+++ wireless-dev/net/netlink/af_netlink.c	2007-07-03 00:31:30.267889695 +0200
@@ -316,8 +316,11 @@ netlink_update_listeners(struct sock *sk
 
 	for (i = 0; i < NLGRPSZ(tbl->groups)/sizeof(unsigned long); 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 (nlk_sk(sk)->ngroups >=
+			    (i + 1) * sizeof(unsigned long))
+				mask |= nlk_sk(sk)->groups[i];
+		}
 		tbl->listeners[i] = mask;
 	}
 	/* this function is only called with the netlink table "grabbed", which
@@ -555,10 +558,11 @@ 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();
@@ -570,9 +574,15 @@ static int netlink_alloc_groups(struct s
 	if (err)
 		return err;
 
-	nlk->groups = kzalloc(NLGRPSZ(groups), GFP_KERNEL);
-	if (nlk->groups == NULL)
+	if (nlk->ngroups >= groups)
+		return 0;
+
+	new_groups = krealloc(nlk->groups, NLGRPSZ(groups), GFP_KERNEL);
+	if (new_groups == NULL)
 		return -ENOMEM;
+	memset((char*)new_groups + NLGRPSZ(nlk->ngroups), 0,
+	       NLGRPSZ(groups) - NLGRPSZ(nlk->ngroups));
+	nlk->groups = new_groups;
 	nlk->ngroups = groups;
 	return 0;
 }
@@ -591,11 +601,9 @@ 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) {
@@ -1041,11 +1049,9 @@ 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();
@@ -1332,6 +1338,31 @@ out_sock_release:
 	return NULL;
 }
 
+int netlink_change_ngroups(int unit, unsigned int groups)
+{
+	unsigned long *listeners;
+	int err = 0;
+
+	netlink_table_grab();
+	if (NLGRPSZ(nl_table[unit].groups) < NLGRPSZ(groups)) {
+		listeners = krealloc(nl_table[unit].listeners,
+				     NLGRPSZ(groups), GFP_KERNEL);
+		if (!listeners) {
+			err = -ENOMEM;
+			goto out_ungrab;
+		}
+		memset((char*) listeners + NLGRPSZ(nl_table[unit].groups),
+		       0, NLGRPSZ(groups) - NLGRPSZ(nl_table[unit].groups));
+		nl_table[unit].listeners = listeners;
+	}
+	nl_table[unit].groups = groups;
+
+ out_ungrab:
+	netlink_table_ungrab();
+	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	2007-07-03 00:09:13.047889695 +0200
+++ wireless-dev/include/linux/netlink.h	2007-07-03 00:31:30.267889695 +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(int unit, 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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