Merge branch 'dctcp'

Daniel Borkmann says:

====================
net: tcp: DCTCP congestion control algorithm

This patch series adds support for the DataCenter TCP (DCTCP) congestion
control algorithm. Please see individual patches for the details.

The last patch adds DCTCP as a congestion control module, and previous
ones add needed infrastructure to extend the congestion control framework.

Joint work between Florian Westphal, Daniel Borkmann and Glenn Judd.

v3 -> v2:
 - No changes anywhere, just a resend as requested by Dave
 - Added Stephen's ACK
v1 -> v2:
 - Rebased to latest net-next
 - Addressed Eric's feedback, thanks!
  - Update stale comment wrt. DCTCP ECN usage
  - Don't call INET_ECN_xmit for every packet
 - Add dctcp ss/inetdiag support to expose internal stats to userspace
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 7 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 4d92703df4c..86a0216fcaa 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -318,11 +318,15 @@ static u16 tcp_select_window(struct sock *sk)
 }
 
 /* Packet ECN state for a SYN-ACK */
-static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
+static inline void TCP_ECN_send_synack(struct sock *sk, struct sk_buff *skb)
 {
+	const struct tcp_sock *tp = tcp_sk(sk);
+
 	TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
 	if (!(tp->ecn_flags & TCP_ECN_OK))
 		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
+	else if (tcp_ca_needs_ecn(sk))
+		INET_ECN_xmit(sk);
 }
 
 /* Packet ECN state for a SYN.  */
@@ -331,17 +335,24 @@ static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
 	struct tcp_sock *tp = tcp_sk(sk);
 
 	tp->ecn_flags = 0;
-	if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) {
+	if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
+	    tcp_ca_needs_ecn(sk)) {
 		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
 		tp->ecn_flags = TCP_ECN_OK;
+		if (tcp_ca_needs_ecn(sk))
+			INET_ECN_xmit(sk);
 	}
 }
 
 static __inline__ void
-TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
+TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th,
+		    struct sock *sk)
 {
-	if (inet_rsk(req)->ecn_ok)
+	if (inet_rsk(req)->ecn_ok) {
 		th->ece = 1;
+		if (tcp_ca_needs_ecn(sk))
+			INET_ECN_xmit(sk);
+	}
 }
 
 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
@@ -362,7 +373,7 @@ static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
 				tcp_hdr(skb)->cwr = 1;
 				skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 			}
-		} else {
+		} else if (!tcp_ca_needs_ecn(sk)) {
 			/* ACK or retransmitted segment: clear ECT|CE */
 			INET_ECN_dontxmit(sk);
 		}
@@ -2789,7 +2800,7 @@ int tcp_send_synack(struct sock *sk)
 		}
 
 		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
-		TCP_ECN_send_synack(tcp_sk(sk), skb);
+		TCP_ECN_send_synack(sk, skb);
 	}
 	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
 }
@@ -2848,7 +2859,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 	memset(th, 0, sizeof(struct tcphdr));
 	th->syn = 1;
 	th->ack = 1;
-	TCP_ECN_make_synack(req, th);
+	TCP_ECN_make_synack(req, th, sk);
 	th->source = htons(ireq->ir_num);
 	th->dest = ireq->ir_rmt_port;
 	/* Setting of flags are superfluous here for callers (and ECE is
@@ -3119,6 +3130,8 @@ void tcp_send_delayed_ack(struct sock *sk)
 	int ato = icsk->icsk_ack.ato;
 	unsigned long timeout;
 
+	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);
+
 	if (ato > TCP_DELACK_MIN) {
 		const struct tcp_sock *tp = tcp_sk(sk);
 		int max_ato = HZ / 2;
@@ -3175,6 +3188,8 @@ void tcp_send_ack(struct sock *sk)
 	if (sk->sk_state == TCP_CLOSE)
 		return;
 
+	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);
+
 	/* We are not putting this on the write queue, so
 	 * tcp_transmit_skb() will set the ownership to this
 	 * sock.
@@ -3196,6 +3211,7 @@ void tcp_send_ack(struct sock *sk)
 	skb_mstamp_get(&buff->skb_mstamp);
 	tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
 }
+EXPORT_SYMBOL_GPL(tcp_send_ack);
 
 /* This routine sends a packet with an out of date sequence
  * number. It assumes the other end will try to ack it.