Patch "netlink: add a start callback for starting a netlink dump" has been added to the 4.4-stable tree

Patch "netlink: add a start callback for starting a netlink dump" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    netlink: add a start callback for starting a netlink dump

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     netlink-add-a-start-callback-for-starting-a-netlink-dump.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From fc9e50f5a5a4e1fa9ba2756f745a13e693cf6a06 Mon Sep 17 00:00:00 2001
From: Tom Herbert <tom@herbertland.com>
Date: Tue, 15 Dec 2015 15:41:37 -0800
Subject: netlink: add a start callback for starting a netlink dump

From: Tom Herbert <tom@herbertland.com>

commit fc9e50f5a5a4e1fa9ba2756f745a13e693cf6a06 upstream.

The start callback allows the caller to set up a context for the
dump callbacks. Presumably, the context can then be destroyed in
the done callback.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/linux/netlink.h  |    2 ++
 include/net/genetlink.h  |    2 ++
 net/netlink/af_netlink.c |    4 ++++
 net/netlink/genetlink.c  |   16 ++++++++++++++++
 4 files changed, 24 insertions(+)

--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -131,6 +131,7 @@ netlink_skb_clone(struct sk_buff *skb, g
 struct netlink_callback {
 	struct sk_buff		*skb;
 	const struct nlmsghdr	*nlh;
+	int			(*start)(struct netlink_callback *);
 	int			(*dump)(struct sk_buff * skb,
 					struct netlink_callback *cb);
 	int			(*done)(struct netlink_callback *cb);
@@ -153,6 +154,7 @@ struct nlmsghdr *
 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 
 struct netlink_dump_control {
+	int (*start)(struct netlink_callback *);
 	int (*dump)(struct sk_buff *skb, struct netlink_callback *);
 	int (*done)(struct netlink_callback *);
 	void *data;
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -114,6 +114,7 @@ static inline void genl_info_net_set(str
  * @flags: flags
  * @policy: attribute validation policy
  * @doit: standard command callback
+ * @start: start callback for dumps
  * @dumpit: callback for dumpers
  * @done: completion callback for dumps
  * @ops_list: operations list
@@ -122,6 +123,7 @@ struct genl_ops {
 	const struct nla_policy	*policy;
 	int		       (*doit)(struct sk_buff *skb,
 				       struct genl_info *info);
+	int		       (*start)(struct netlink_callback *cb);
 	int		       (*dumpit)(struct sk_buff *skb,
 					 struct netlink_callback *cb);
 	int		       (*done)(struct netlink_callback *cb);
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2203,6 +2203,7 @@ int __netlink_dump_start(struct sock *ss
 
 	cb = &nlk->cb;
 	memset(cb, 0, sizeof(*cb));
+	cb->start = control->start;
 	cb->dump = control->dump;
 	cb->done = control->done;
 	cb->nlh = nlh;
@@ -2216,6 +2217,9 @@ int __netlink_dump_start(struct sock *ss
 
 	mutex_unlock(nlk->cb_mutex);
 
+	if (cb->start)
+		cb->start(cb);
+
 	ret = netlink_dump(sk);
 	sock_put(sk);
 
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -513,6 +513,20 @@ void *genlmsg_put(struct sk_buff *skb, u
 }
 EXPORT_SYMBOL(genlmsg_put);
 
+static int genl_lock_start(struct netlink_callback *cb)
+{
+	/* our ops are always const - netlink API doesn't propagate that */
+	const struct genl_ops *ops = cb->data;
+	int rc = 0;
+
+	if (ops->start) {
+		genl_lock();
+		rc = ops->start(cb);
+		genl_unlock();
+	}
+	return rc;
+}
+
 static int genl_lock_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	/* our ops are always const - netlink API doesn't propagate that */
@@ -577,6 +591,7 @@ static int genl_family_rcv_msg(struct ge
 				.module = family->module,
 				/* we have const, but the netlink API doesn't */
 				.data = (void *)ops,
+				.start = genl_lock_start,
 				.dump = genl_lock_dumpit,
 				.done = genl_lock_done,
 			};
@@ -588,6 +603,7 @@ static int genl_family_rcv_msg(struct ge
 		} else {
 			struct netlink_dump_control c = {
 				.module = family->module,
+				.start = ops->start,
 				.dump = ops->dumpit,
 				.done = ops->done,
 			};


Patches currently in stable-queue which might be from tom@herbertland.com are

queue-4.4/netlink-add-a-start-callback-for-starting-a-netlink-dump.patch