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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/ip.h

···
 	flow->control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
 }
 
-static inline void inet_set_txhash(struct sock *sk)
-{
-	struct inet_sock *inet = inet_sk(sk);
-	struct flow_keys keys;
-
-	memset(&keys, 0, sizeof(keys));
-
-	keys.addrs.v4addrs.src = inet->inet_saddr;
-	keys.addrs.v4addrs.dst = inet->inet_daddr;
-	keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
-	keys.ports.src = inet->inet_sport;
-	keys.ports.dst = inet->inet_dport;
-
-	sk->sk_txhash = flow_hash_from_keys(&keys);
-}
-
 static inline __wsum inet_gro_compute_pseudo(struct sk_buff *skb, int proto)
 {
 	const struct iphdr *iph = skb_gro_network_header(skb);

include/net/ipv6.h

···
 }
 
 #if IS_ENABLED(CONFIG_IPV6)
-static inline void ip6_set_txhash(struct sock *sk)
-{
-	struct inet_sock *inet = inet_sk(sk);
-	struct ipv6_pinfo *np = inet6_sk(sk);
-	struct flow_keys keys;
-
-	memset(&keys, 0, sizeof(keys));
-
-	memcpy(&keys.addrs.v6addrs.src, &np->saddr,
-	       sizeof(keys.addrs.v6addrs.src));
-	memcpy(&keys.addrs.v6addrs.dst, &sk->sk_v6_daddr,
-	       sizeof(keys.addrs.v6addrs.dst));
-	keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
-	keys.ports.src = inet->inet_sport;
-	keys.ports.dst = inet->inet_dport;
-
-	sk->sk_txhash = flow_hash_from_keys(&keys);
-}
-
 static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
 					__be32 flowlabel, bool autolabel)
 {

include/net/sock.h

···
 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)
 {

net/ipv4/datagram.c

···
 	inet->inet_daddr = fl4->daddr;
 	inet->inet_dport = usin->sin_port;
 	sk->sk_state = TCP_ESTABLISHED;
-	inet_set_txhash(sk);
+	sk_set_txhash(sk);
 	inet->inet_id = jiffies;
 
 	sk_dst_set(sk, &rt->dst);

net/ipv4/tcp_ipv4.c

···
 	if (err)
 		goto failure;
 
-	inet_set_txhash(sk);
+	sk_set_txhash(sk);
 
 	rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
 			       inet->inet_sport, inet->inet_dport, sk);
···
 	newinet->mc_ttl	      = ip_hdr(skb)->ttl;
 	newinet->rcv_tos      = ip_hdr(skb)->tos;
 	inet_csk(newsk)->icsk_ext_hdr_len = 0;
-	inet_set_txhash(newsk);
+	sk_set_txhash(newsk);
 	if (inet_opt)
 		inet_csk(newsk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
 	newinet->inet_id = newtp->write_seq ^ jiffies;

net/ipv6/datagram.c

···
 		      NULL);
 
 	sk->sk_state = TCP_ESTABLISHED;
-	ip6_set_txhash(sk);
+	sk_set_txhash(sk);
 out:
 	fl6_sock_release(flowlabel);
 	return err;

net/ipv6/tcp_ipv6.c

···
 	if (err)
 		goto late_failure;
 
-	ip6_set_txhash(sk);
+	sk_set_txhash(sk);
 
 	if (!tp->write_seq && likely(!tp->repair))
 		tp->write_seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
···
 	newsk->sk_v6_rcv_saddr = ireq->ir_v6_loc_addr;
 	newsk->sk_bound_dev_if = ireq->ir_iif;
 
-	ip6_set_txhash(newsk);
+	sk_set_txhash(newsk);
 
 	/* Now IPv6 options...