lwtunnel: support dst output redirect function

This patch introduces lwtunnel_output function to call corresponding
lwtunnels output function to xmit the packet.

It adds two variants lwtunnel_output and lwtunnel_output6 for ipv4 and
ipv6 respectively today. But this is subject to change when lwtstate will
reside in dst or dst_metadata (as per upstream discussions).
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/lwtunnel.h

@@ -69,6 +69,8 @@ int lwtunnel_fill_encap(struct sk_buff *skb,
 int lwtunnel_get_encap_size(struct lwtunnel_state *lwtstate);
 struct lwtunnel_state *lwtunnel_state_alloc(int hdr_len);
 int lwtunnel_cmp_encap(struct lwtunnel_state *a, struct lwtunnel_state *b);
+int lwtunnel_output(struct sock *sk, struct sk_buff *skb);
+int lwtunnel_output6(struct sock *sk, struct sk_buff *skb);
 
 #else
 
@@ -127,6 +129,16 @@ static inline int lwtunnel_cmp_encap(struct lwtunnel_state *a,
 	return 0;
 }
 
+static inline int lwtunnel_output(struct sock *sk, struct sk_buff *skb)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int lwtunnel_output6(struct sock *sk, struct sk_buff *skb)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif
 
 #endif /* __NET_LWTUNNEL_H */

net/core/lwtunnel.c

@@ -25,6 +25,7 @@
 
 #include <net/lwtunnel.h>
 #include <net/rtnetlink.h>
+#include <net/ip6_fib.h>
 
 struct lwtunnel_state *lwtunnel_state_alloc(int encap_len)
 {
@@ -177,3 +178,58 @@ int lwtunnel_cmp_encap(struct lwtunnel_state *a, struct lwtunnel_state *b)
 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_cmp_encap);
+
+int __lwtunnel_output(struct sock *sk, struct sk_buff *skb,
+		      struct lwtunnel_state *lwtstate)
+{
+	const struct lwtunnel_encap_ops *ops;
+	int ret = -EINVAL;
+
+	if (!lwtstate)
+		goto drop;
+
+	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
+	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
+		return 0;
+
+	ret = -EOPNOTSUPP;
+	rcu_read_lock();
+	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
+	if (likely(ops && ops->output))
+		ret = ops->output(sk, skb);
+	rcu_read_unlock();
+
+	if (ret == -EOPNOTSUPP)
+		goto drop;
+
+	return ret;
+
+drop:
+	kfree(skb);
+
+	return ret;
+}
+
+int lwtunnel_output6(struct sock *sk, struct sk_buff *skb)
+{
+	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
+	struct lwtunnel_state *lwtstate = NULL;
+
+	if (rt)
+		lwtstate = rt->rt6i_lwtstate;
+
+	return __lwtunnel_output(sk, skb, lwtstate);
+}
+EXPORT_SYMBOL(lwtunnel_output6);
+
+int lwtunnel_output(struct sock *sk, struct sk_buff *skb)
+{
+	struct rtable *rt = (struct rtable *)skb_dst(skb);
+	struct lwtunnel_state *lwtstate = NULL;
+
+	if (rt)
+		lwtstate = rt->rt_lwtstate;
+
+	return __lwtunnel_output(sk, skb, lwtstate);
+}
+EXPORT_SYMBOL(lwtunnel_output);