netfilter: nfnetlink: add RCU in nfnetlink_rcv_msg()

Goal of this patch is to permit nfnetlink providers not mandate
nfnl_mutex being held while nfnetlink_rcv_msg() calls them.

If struct nfnl_callback contains a non NULL call_rcu(), then
nfnetlink_rcv_msg() will use it instead of call() field, holding
rcu_read_lock instead of nfnl_mutex

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Florian Westphal <fw@strlen.de>
CC: Eric Leblond <eric@regit.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index 2b11fc1a86be..74d33861473c 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -60,6 +60,9 @@ struct nfnl_callback {
         int (*call)(struct sock *nl, struct sk_buff *skb, 
                     const struct nlmsghdr *nlh,
                     const struct nlattr * const cda[]);
+        int (*call_rcu)(struct sock *nl, struct sk_buff *skb, 
+                    const struct nlmsghdr *nlh,
+                    const struct nlattr * const cda[]);
         const struct nla_policy *policy;        /* netlink attribute policy */
         const u_int16_t attr_count;             /* number of nlattr's */
 };