tcp: minor optimization around tcp_hdr() usage in receive path

This is additional to the
commit ea1627c2 ("tcp: minor optimizations around tcp_hdr() usage").
At this point, skb->data is same with tcp_hdr() as tcp header has not
been pulled yet. So use the less expensive one to get the tcp header.

Remove the third parameter of tcp_rcv_established() and put it into
the function body.

Furthermore, the local variables are listed as a reverse christmas tree :)

Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -334,8 +334,7 @@ void tcp_write_timer_handler(struct sock *sk);
 void tcp_delack_timer_handler(struct sock *sk);
 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
-void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
-			 const struct tcphdr *th);
+void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
 void tcp_rcv_space_adjust(struct sock *sk);
 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
 void tcp_twsk_destructor(struct sock *sk);

include/trace/events/tcp.h

@@ -248,8 +248,9 @@ TRACE_EVENT(tcp_probe,
 	),
 
 	TP_fast_assign(
-		const struct tcp_sock *tp = tcp_sk(sk);
+		const struct tcphdr *th = (const struct tcphdr *)skb->data;
 		const struct inet_sock *inet = inet_sk(sk);
+		const struct tcp_sock *tp = tcp_sk(sk);
 
 		memset(__entry->saddr, 0, sizeof(struct sockaddr_in6));
 		memset(__entry->daddr, 0, sizeof(struct sockaddr_in6));
@@ -261,7 +262,7 @@ TRACE_EVENT(tcp_probe,
 		__entry->dport = ntohs(inet->inet_dport);
 		__entry->mark = skb->mark;
 
-		__entry->data_len = skb->len - tcp_hdrlen(skb);
+		__entry->data_len = skb->len - __tcp_hdrlen(th);
 		__entry->snd_nxt = tp->snd_nxt;
 		__entry->snd_una = tp->snd_una;
 		__entry->snd_cwnd = tp->snd_cwnd;

net/ipv4/tcp_input.c

@@ -5390,11 +5390,11 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
  *	the rest is checked inline. Fast processing is turned on in
  *	tcp_data_queue when everything is OK.
  */
-void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
-			 const struct tcphdr *th)
+void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 {
-	unsigned int len = skb->len;
+	const struct tcphdr *th = (const struct tcphdr *)skb->data;
 	struct tcp_sock *tp = tcp_sk(sk);
+	unsigned int len = skb->len;
 
 	/* TCP congestion window tracking */
 	trace_tcp_probe(sk, skb);

net/ipv4/tcp_ipv4.c

@@ -1486,7 +1486,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 				sk->sk_rx_dst = NULL;
 			}
 		}
-		tcp_rcv_established(sk, skb, tcp_hdr(skb));
+		tcp_rcv_established(sk, skb);
 		return 0;
 	}
 

net/ipv6/tcp_ipv6.c

@@ -1322,7 +1322,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 			}
 		}
 
-		tcp_rcv_established(sk, skb, tcp_hdr(skb));
+		tcp_rcv_established(sk, skb);
 		if (opt_skb)
 			goto ipv6_pktoptions;
 		return 0;