From ffd177dea5c1ee5b717961d041df0778d58f50c0 Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Mon, 8 Oct 2018 15:32:20 -0700 Subject: [PATCH] tcp: refactor DCTCP ECN ACK handling DCTCP has two parts - a new ECN signalling mechanism and the response function to it. The first part can be used by other congestion control for DCTCP-ECN deployed networks. This patch moves that part into a separate tcp_dctcp.h to be used by other congestion control module (like how Yeah uses Vegas algorithmas). For example, BBR is experimenting such ECN signal currently https://tinyurl.com/ietf-102-iccrg-bbr2 Signed-off-by: Yuchung Cheng Signed-off-by: Yousuk Seung Signed-off-by: Neal Cardwell Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_dctcp.c | 55 ++++---------------------------------------- net/ipv4/tcp_dctcp.h | 40 ++++++++++++++++++++++++++++++++ 2 files changed, 44 insertions(+), 51 deletions(-) create mode 100644 net/ipv4/tcp_dctcp.h diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c index ca61e2a659e7..cd4814f7e962 100644 --- a/net/ipv4/tcp_dctcp.c +++ b/net/ipv4/tcp_dctcp.c @@ -44,6 +44,7 @@ #include #include #include +#include "tcp_dctcp.h" #define DCTCP_MAX_ALPHA 1024U @@ -118,54 +119,6 @@ static u32 dctcp_ssthresh(struct sock *sk) return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->dctcp_alpha) >> 11U), 2U); } -/* Minimal DCTP CE state machine: - * - * S: 0 <- last pkt was non-CE - * 1 <- last pkt was CE - */ - -static void dctcp_ce_state_0_to_1(struct sock *sk) -{ - struct dctcp *ca = inet_csk_ca(sk); - struct tcp_sock *tp = tcp_sk(sk); - - if (!ca->ce_state) { - /* State has changed from CE=0 to CE=1, force an immediate - * ACK to reflect the new CE state. If an ACK was delayed, - * send that first to reflect the prior CE state. - */ - if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) - __tcp_send_ack(sk, ca->prior_rcv_nxt); - inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; - } - - ca->prior_rcv_nxt = tp->rcv_nxt; - ca->ce_state = 1; - - tp->ecn_flags |= TCP_ECN_DEMAND_CWR; -} - -static void dctcp_ce_state_1_to_0(struct sock *sk) -{ - struct dctcp *ca = inet_csk_ca(sk); - struct tcp_sock *tp = tcp_sk(sk); - - if (ca->ce_state) { - /* State has changed from CE=1 to CE=0, force an immediate - * ACK to reflect the new CE state. If an ACK was delayed, - * send that first to reflect the prior CE state. - */ - if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) - __tcp_send_ack(sk, ca->prior_rcv_nxt); - inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; - } - - ca->prior_rcv_nxt = tp->rcv_nxt; - ca->ce_state = 0; - - tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; -} - static void dctcp_update_alpha(struct sock *sk, u32 flags) { const struct tcp_sock *tp = tcp_sk(sk); @@ -230,12 +183,12 @@ static void dctcp_state(struct sock *sk, u8 new_state) static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev) { + struct dctcp *ca = inet_csk_ca(sk); + switch (ev) { case CA_EVENT_ECN_IS_CE: - dctcp_ce_state_0_to_1(sk); - break; case CA_EVENT_ECN_NO_CE: - dctcp_ce_state_1_to_0(sk); + dctcp_ece_ack_update(sk, ev, &ca->prior_rcv_nxt, &ca->ce_state); break; default: /* Don't care for the rest. */ diff --git a/net/ipv4/tcp_dctcp.h b/net/ipv4/tcp_dctcp.h new file mode 100644 index 000000000000..d69a77cbd0c7 --- /dev/null +++ b/net/ipv4/tcp_dctcp.h @@ -0,0 +1,40 @@ +#ifndef _TCP_DCTCP_H +#define _TCP_DCTCP_H + +static inline void dctcp_ece_ack_cwr(struct sock *sk, u32 ce_state) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (ce_state == 1) + tp->ecn_flags |= TCP_ECN_DEMAND_CWR; + else + tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; +} + +/* Minimal DCTP CE state machine: + * + * S: 0 <- last pkt was non-CE + * 1 <- last pkt was CE + */ +static inline void dctcp_ece_ack_update(struct sock *sk, enum tcp_ca_event evt, + u32 *prior_rcv_nxt, u32 *ce_state) +{ + u32 new_ce_state = (evt == CA_EVENT_ECN_IS_CE) ? 1 : 0; + + if (*ce_state != new_ce_state) { + /* CE state has changed, force an immediate ACK to + * reflect the new CE state. If an ACK was delayed, + * send that first to reflect the prior CE state. + */ + if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) { + dctcp_ece_ack_cwr(sk, *ce_state); + __tcp_send_ack(sk, *prior_rcv_nxt); + } + inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; + } + *prior_rcv_nxt = tcp_sk(sk)->rcv_nxt; + *ce_state = new_ce_state; + dctcp_ece_ack_cwr(sk, new_ce_state); +} + +#endif