[net-next PATCH 01/02] net/ipv4: VTI support rx-path hook in xfrm4_mode_tunnel.

[Saurabh <saurabh.mohan@vyatta.com>]

Add hook for rx-path xfmr4_mode_tunnel for VTI tunnel module.

Signed-off-by: Saurabh Mohan <saurabh.mohan@vyatta.com>
Reviewed-by: Stephen Hemminger <shemminger@vyatta.com>

---
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index e0a55df..04214c0 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1475,6 +1475,8 @@ extern int xfrm4_output(struct sk_buff *skb);
 extern int xfrm4_output_finish(struct sk_buff *skb);
 extern int xfrm4_tunnel_register(struct xfrm_tunnel *handler, unsigned short family);
 extern int xfrm4_tunnel_deregister(struct xfrm_tunnel *handler, unsigned short family);
+extern int xfrm4_mode_tunnel_input_register(struct xfrm_tunnel *handler);
+extern int xfrm4_mode_tunnel_input_deregister(struct xfrm_tunnel *handler);
 extern int xfrm6_extract_header(struct sk_buff *skb);
 extern int xfrm6_extract_input(struct xfrm_state *x, struct sk_buff *skb);
 extern int xfrm6_rcv_spi(struct sk_buff *skb, int nexthdr, __be32 spi);
diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
index ed4bf11..4fc2944 100644
--- a/net/ipv4/xfrm4_mode_tunnel.c
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -15,6 +15,68 @@
 #include <net/ip.h>
 #include <net/xfrm.h>
 
+/*
+ * Informational hook. The decap is still done here.
+ */
+static struct xfrm_tunnel __rcu *rcv_notify_handlers __read_mostly;
+static DEFINE_MUTEX(xfrm4_mode_tunnel_input_mutex);
+
+int xfrm4_mode_tunnel_input_register(struct xfrm_tunnel *handler)
+{
+	struct xfrm_tunnel __rcu **pprev;
+	struct xfrm_tunnel *t;
+
+	int ret = -EEXIST;
+	int priority = handler->priority;
+
+	mutex_lock(&xfrm4_mode_tunnel_input_mutex);
+
+	for (pprev = &rcv_notify_handlers;
+		(t = rcu_dereference_protected(*pprev,
+		lockdep_is_held(&xfrm4_mode_tunnel_input_mutex))) != NULL;
+		pprev = &t->next) {
+		if (t->priority > priority)
+			break;
+		if (t->priority == priority)
+			goto err;
+
+	}
+
+	handler->next = *pprev;
+	rcu_assign_pointer(*pprev, handler);
+
+	ret = 0;
+
+err:
+	mutex_unlock(&xfrm4_mode_tunnel_input_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xfrm4_mode_tunnel_input_register);
+
+int xfrm4_mode_tunnel_input_deregister(struct xfrm_tunnel *handler)
+{
+	struct xfrm_tunnel __rcu **pprev;
+	struct xfrm_tunnel *t;
+	int ret = -ENOENT;
+
+	mutex_lock(&xfrm4_mode_tunnel_input_mutex);
+	for (pprev = &rcv_notify_handlers;
+		(t = rcu_dereference_protected(*pprev,
+		lockdep_is_held(&xfrm4_mode_tunnel_input_mutex))) != NULL;
+		pprev = &t->next) {
+		if (t == handler) {
+			*pprev = handler->next;
+			ret = 0;
+			break;
+		}
+	}
+	mutex_unlock(&xfrm4_mode_tunnel_input_mutex);
+	synchronize_net();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xfrm4_mode_tunnel_input_deregister);
+
 static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
 {
 	struct iphdr *inner_iph = ipip_hdr(skb);
@@ -64,8 +126,14 @@ static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
 	return 0;
 }
 
+#define for_each_input_rcu(head, handler)	\
+	for (handler = rcu_dereference(head);	\
+		handler != NULL;		\
+		handler = rcu_dereference(handler->next))  \
+
 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 {
+	struct xfrm_tunnel *handler;
 	int err = -EINVAL;
 
 	if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
@@ -74,6 +142,10 @@ static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 		goto out;
 
+	/* The handlers do not consume the skb. */
+	for_each_input_rcu(rcv_notify_handlers, handler)
+		handler->handler(skb);
+
 	if (skb_cloned(skb) &&
 	    (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 		goto out;