ip: factor out protocol delivery helper

So that we can re-use it at the UDP level in a later patch

rfc v3 -> v1
 - add the helper declaration into the ip header
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip.h

@@ -155,6 +155,7 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
 void ip_list_rcv(struct list_head *head, struct packet_type *pt,
 		 struct net_device *orig_dev);
 int ip_local_deliver(struct sk_buff *skb);
+void ip_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int proto);
 int ip_mr_input(struct sk_buff *skb);
 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb);
 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb);

net/ipv4/ip_input.c

@@ -188,51 +188,50 @@ bool ip_call_ra_chain(struct sk_buff *skb)
 	return false;
 }
 
-static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
+void ip_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int protocol)
 {
-	__skb_pull(skb, skb_network_header_len(skb));
-
-	rcu_read_lock();
-	{
-		int protocol = ip_hdr(skb)->protocol;
-		const struct net_protocol *ipprot;
-		int raw;
+	const struct net_protocol *ipprot;
+	int raw, ret;
 
-	resubmit:
-		raw = raw_local_deliver(skb, protocol);
+resubmit:
+	raw = raw_local_deliver(skb, protocol);
 
-		ipprot = rcu_dereference(inet_protos[protocol]);
-		if (ipprot) {
-			int ret;
-
-			if (!ipprot->no_policy) {
-				if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
-					kfree_skb(skb);
-					goto out;
-				}
-				nf_reset(skb);
+	ipprot = rcu_dereference(inet_protos[protocol]);
+	if (ipprot) {
+		if (!ipprot->no_policy) {
+			if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
+				kfree_skb(skb);
+				return;
 			}
-			ret = ipprot->handler(skb);
-			if (ret < 0) {
-				protocol = -ret;
-				goto resubmit;
+			nf_reset(skb);
+		}
+		ret = ipprot->handler(skb);
+		if (ret < 0) {
+			protocol = -ret;
+			goto resubmit;
+		}
+		__IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
+	} else {
+		if (!raw) {
+			if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
+				__IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS);
+				icmp_send(skb, ICMP_DEST_UNREACH,
+					  ICMP_PROT_UNREACH, 0);
 			}
-			__IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
+			kfree_skb(skb);
 		} else {
-			if (!raw) {
-				if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
-					__IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS);
-					icmp_send(skb, ICMP_DEST_UNREACH,
-						  ICMP_PROT_UNREACH, 0);
-				}
-				kfree_skb(skb);
-			} else {
-				__IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
-				consume_skb(skb);
-			}
+			__IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
+			consume_skb(skb);
 		}
 	}
- out:
+}
+
+static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	__skb_pull(skb, skb_network_header_len(skb));
+
+	rcu_read_lock();
+	ip_protocol_deliver_rcu(net, skb, ip_hdr(skb)->protocol);
 	rcu_read_unlock();
 
 	return 0;