ipv6: allow to cache dst for a connected sk in ip6_sk_dst_lookup_flow()

Add 'connected' parameter to ip6_sk_dst_lookup_flow() and update
the cache only if ip6_sk_dst_check() returns NULL and a socket
is connected.

The function is used as before, the new behavior for UDP sockets
in udpv6_sendmsg() will be enabled in the next patch.
Signed-off-by: NAlexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -965,7 +965,8 @@ int ip6_dst_lookup(struct net *net, struct sock *sk, struct dst_entry **dst,
 struct dst_entry *ip6_dst_lookup_flow(const struct sock *sk, struct flowi6 *fl6,
 				      const struct in6_addr *final_dst);
 struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
-					 const struct in6_addr *final_dst);
+					 const struct in6_addr *final_dst,
+					 bool connected);
 struct dst_entry *ip6_blackhole_route(struct net *net,
 				      struct dst_entry *orig_dst);
 

net/ipv6/ip6_output.c

@@ -1105,23 +1105,32 @@ EXPORT_SYMBOL_GPL(ip6_dst_lookup_flow);
  *	@sk: socket which provides the dst cache and route info
  *	@fl6: flow to lookup
  *	@final_dst: final destination address for ipsec lookup
+ *	@connected: whether @sk is connected or not
  *
  *	This function performs a route lookup on the given flow with the
  *	possibility of using the cached route in the socket if it is valid.
  *	It will take the socket dst lock when operating on the dst cache.
  *	As a result, this function can only be used in process context.
  *
+ *	In addition, for a connected socket, cache the dst in the socket
+ *	if the current cache is not valid.
+ *
  *	It returns a valid dst pointer on success, or a pointer encoded
  *	error code.
  */
 struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
-					 const struct in6_addr *final_dst)
+					 const struct in6_addr *final_dst,
+					 bool connected)
 {
 	struct dst_entry *dst = sk_dst_check(sk, inet6_sk(sk)->dst_cookie);
 
 	dst = ip6_sk_dst_check(sk, dst, fl6);
-	if (!dst)
-		dst = ip6_dst_lookup_flow(sk, fl6, final_dst);
+	if (dst)
+		return dst;
+
+	dst = ip6_dst_lookup_flow(sk, fl6, final_dst);
+	if (connected && !IS_ERR(dst))
+		ip6_sk_dst_store_flow(sk, dst_clone(dst), fl6);
 
 	return dst;
 }

net/ipv6/ping.c

@@ -121,7 +121,7 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	ipc6.tclass = np->tclass;
 	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);
 
-	dst = ip6_sk_dst_lookup_flow(sk, &fl6,  daddr);
+	dst = ip6_sk_dst_lookup_flow(sk, &fl6, daddr, false);
 	if (IS_ERR(dst))
 		return PTR_ERR(dst);
 	rt = (struct rt6_info *) dst;

net/ipv6/udp.c

@@ -1308,7 +1308,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);
 
-	dst = ip6_sk_dst_lookup_flow(sk, &fl6, final_p);
+	dst = ip6_sk_dst_lookup_flow(sk, &fl6, final_p, false);
 	if (IS_ERR(dst)) {
 		err = PTR_ERR(dst);
 		dst = NULL;