nefilter: nfnetlink: add nfnetlink_set_err and use it in ctnetlink

This patch adds nfnetlink_set_err() to propagate the error to netlink
broadcast listener in case of memory allocation errors in the
message building.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/netfilter/nfnetlink.c

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 9c0ba17..2785d66 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -113,6 +113,12 @@
 }
 EXPORT_SYMBOL_GPL(nfnetlink_send);
 
+void nfnetlink_set_err(u32 pid, u32 group, int error)
+{
+	netlink_set_err(nfnl, pid, group, error);
+}
+EXPORT_SYMBOL_GPL(nfnetlink_set_err);
+
 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 {
 	return netlink_unicast(nfnl, skb, pid, flags);