net: Set sk_txhash from a random number

This patch creates sk_set_txhash and eliminates protocol specific
inet_set_txhash and ip6_set_txhash. sk_set_txhash simply sets a
random number instead of performing flow dissection. sk_set_txash
is also allowed to be called multiple times for the same socket,
we'll need this when redoing the hash for negative routing advice.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index 4353ef7..fe735c4 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1687,6 +1687,14 @@
 kuid_t sock_i_uid(struct sock *sk);
 unsigned long sock_i_ino(struct sock *sk);
 
+static inline void sk_set_txhash(struct sock *sk)
+{
+	sk->sk_txhash = prandom_u32();
+
+	if (unlikely(!sk->sk_txhash))
+		sk->sk_txhash = 1;
+}
+
 static inline struct dst_entry *
 __sk_dst_get(struct sock *sk)
 {