net: use indirect call helpers for dst_output

This patch avoids the indirect call for the common case:
ip6_output and ip_output
Signed-off-by: Brian Vazquez <brianvv@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/dst.h

@@ -436,10 +436,16 @@ static inline void dst_set_expires(struct dst_entry *dst, int timeout)
 		dst->expires = expires;
 }
 
+INDIRECT_CALLABLE_DECLARE(int ip6_output(struct net *, struct sock *,
+					 struct sk_buff *));
+INDIRECT_CALLABLE_DECLARE(int ip_output(struct net *, struct sock *,
+					 struct sk_buff *));
 /* Output packet to network from transport.  */
 static inline int dst_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
-	return skb_dst(skb)->output(net, sk, skb);
+	return INDIRECT_CALL_INET(skb_dst(skb)->output,
+				  ip6_output, ip_output,
+				  net, sk, skb);
 }
 
 INDIRECT_CALLABLE_DECLARE(int ip6_input(struct sk_buff *));

net/ipv4/ip_output.c

@@ -434,6 +434,7 @@ int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 			    ip_finish_output,
 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
 }
+EXPORT_SYMBOL(ip_output);
 
 /*
  * copy saddr and daddr, possibly using 64bit load/stores

net/ipv6/ip6_output.c

@@ -217,6 +217,7 @@ int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 			    ip6_finish_output,
 			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));
 }
+EXPORT_SYMBOL(ip6_output);
 
 bool ip6_autoflowlabel(struct net *net, const struct ipv6_pinfo *np)
 {