ipv6: datagram: Refactor flowi6 init codes to a new function

Move flowi6 init codes for connected datagram sk to a newly created
function ip6_datagram_flow_key_init().

Notes:
1. fl6_flowlabel is used instead of fl6.flowlabel in __ip6_datagram_connect
2. ipv6_addr_is_multicast(&fl6->daddr) is used instead of
   (addr_type & IPV6_ADDR_MULTICAST) in ip6_datagram_flow_key_init()

This new function will be reused during pmtu update in the later patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Wei Wang <weiwan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/datagram.c

@@ -40,6 +40,30 @@ static bool ipv6_mapped_addr_any(const struct in6_addr *a)
 	return ipv6_addr_v4mapped(a) && (a->s6_addr32[3] == 0);
 }
 
+static void ip6_datagram_flow_key_init(struct flowi6 *fl6, struct sock *sk)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct ipv6_pinfo *np = inet6_sk(sk);
+
+	memset(fl6, 0, sizeof(*fl6));
+	fl6->flowi6_proto = sk->sk_protocol;
+	fl6->daddr = sk->sk_v6_daddr;
+	fl6->saddr = np->saddr;
+	fl6->flowi6_oif = sk->sk_bound_dev_if;
+	fl6->flowi6_mark = sk->sk_mark;
+	fl6->fl6_dport = inet->inet_dport;
+	fl6->fl6_sport = inet->inet_sport;
+	fl6->flowlabel = np->flow_label;
+
+	if (!fl6->flowi6_oif)
+		fl6->flowi6_oif = np->sticky_pktinfo.ipi6_ifindex;
+
+	if (!fl6->flowi6_oif && ipv6_addr_is_multicast(&fl6->daddr))
+		fl6->flowi6_oif = np->mcast_oif;
+
+	security_sk_classify_flow(sk, flowi6_to_flowi(fl6));
+}
+
 static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {
 	struct sockaddr_in6	*usin = (struct sockaddr_in6 *) uaddr;
@@ -52,6 +76,7 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
 	struct ipv6_txoptions	*opt;
 	int			addr_type;
 	int			err;
+	__be32			fl6_flowlabel = 0;
 
 	if (usin->sin6_family == AF_INET) {
 		if (__ipv6_only_sock(sk))
@@ -66,11 +91,10 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
 	if (usin->sin6_family != AF_INET6)
 		return -EAFNOSUPPORT;
 
-	memset(&fl6, 0, sizeof(fl6));
 	if (np->sndflow) {
-		fl6.flowlabel = usin->sin6_flowinfo&IPV6_FLOWINFO_MASK;
-		if (fl6.flowlabel&IPV6_FLOWLABEL_MASK) {
-			flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
+		fl6_flowlabel = usin->sin6_flowinfo & IPV6_FLOWINFO_MASK;
+		if (fl6_flowlabel & IPV6_FLOWLABEL_MASK) {
+			flowlabel = fl6_sock_lookup(sk, fl6_flowlabel);
 			if (!flowlabel)
 				return -EINVAL;
 		}
@@ -145,7 +169,7 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
 	}
 
 	sk->sk_v6_daddr = *daddr;
-	np->flow_label = fl6.flowlabel;
+	np->flow_label = fl6_flowlabel;
 
 	inet->inet_dport = usin->sin6_port;
 
@@ -154,21 +178,7 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
 	 *	destination cache for it.
 	 */
 
-	fl6.flowi6_proto = sk->sk_protocol;
-	fl6.daddr = sk->sk_v6_daddr;
-	fl6.saddr = np->saddr;
-	fl6.flowi6_oif = sk->sk_bound_dev_if;
-	fl6.flowi6_mark = sk->sk_mark;
-	fl6.fl6_dport = inet->inet_dport;
-	fl6.fl6_sport = inet->inet_sport;
-
-	if (!fl6.flowi6_oif)
-		fl6.flowi6_oif = np->sticky_pktinfo.ipi6_ifindex;
-
-	if (!fl6.flowi6_oif && (addr_type&IPV6_ADDR_MULTICAST))
-		fl6.flowi6_oif = np->mcast_oif;
-
-	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));
+	ip6_datagram_flow_key_init(&fl6, sk);
 
 	rcu_read_lock();
 	opt = flowlabel ? flowlabel->opt : rcu_dereference(np->opt);