net: tcp: more detailed ACK events and events for CE marked packets

DataCenter TCP (DCTCP) determines cwnd growth based on ECN information
and ACK properties, e.g. ACK that updates window is treated differently
than DUPACK.

Also DCTCP needs information whether ACK was delayed ACK. Furthermore,
DCTCP also implements a CE state machine that keeps track of CE markings
of incoming packets.

Therefore, extend the congestion control framework to provide these
event types, so that DCTCP can be properly implemented as a normal
congestion algorithm module outside of the core stack.

Joint work with Daniel Borkmann and Glenn Judd.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Glenn Judd <glenn.judd@morganstanley.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8a38774cc66e..fc133178c787 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -233,14 +233,21 @@ static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *s
                         tcp_enter_quickack_mode((struct sock *)tp);
                 break;
         case INET_ECN_CE:
+                if (tcp_ca_needs_ecn((struct sock *)tp))
+                        tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_IS_CE);
+
                 if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {
                         /* Better not delay acks, sender can have a very low cwnd */
                         tcp_enter_quickack_mode((struct sock *)tp);
                         tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
                 }
-                /* fallinto */
+                tp->ecn_flags |= TCP_ECN_SEEN;
+                break;
         default:
+                if (tcp_ca_needs_ecn((struct sock *)tp))
+                        tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_NO_CE);
                 tp->ecn_flags |= TCP_ECN_SEEN;
+                break;
         }
 }
 
@@ -3429,10 +3436,12 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
                 tp->snd_una = ack;
                 flag |= FLAG_WIN_UPDATE;
 
-                tcp_in_ack_event(sk, 0);
+                tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE);
 
                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS);
         } else {
+                u32 ack_ev_flags = CA_ACK_SLOWPATH;
+
                 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
                         flag |= FLAG_DATA;
                 else
@@ -3444,10 +3453,15 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
                         flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
                                                         &sack_rtt_us);
 
-                if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb)))
+                if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) {
                         flag |= FLAG_ECE;
+                        ack_ev_flags |= CA_ACK_ECE;
+                }
+
+                if (flag & FLAG_WIN_UPDATE)
+                        ack_ev_flags |= CA_ACK_WIN_UPDATE;
 
-                tcp_in_ack_event(sk, CA_ACK_SLOWPATH);
+                tcp_in_ack_event(sk, ack_ev_flags);
         }
 
         /* We passed data and got it acked, remove any soft error