diff --git a/Documentation/networking/dctcp.txt b/Documentation/networking/dctcp.txt new file mode 100644 index 0000000000000000000000000000000000000000..0d5dfbc89ec9e37e27b53a610594dd112d3c6e37 --- /dev/null +++ b/Documentation/networking/dctcp.txt @@ -0,0 +1,43 @@ +DCTCP (DataCenter TCP) +---------------------- + +DCTCP is an enhancement to the TCP congestion control algorithm for data +center networks and leverages Explicit Congestion Notification (ECN) in +the data center network to provide multi-bit feedback to the end hosts. + +To enable it on end hosts: + + sysctl -w net.ipv4.tcp_congestion_control=dctcp + +All switches in the data center network running DCTCP must support ECN +marking and be configured for marking when reaching defined switch buffer +thresholds. The default ECN marking threshold heuristic for DCTCP on +switches is 20 packets (30KB) at 1Gbps, and 65 packets (~100KB) at 10Gbps, +but might need further careful tweaking. + +For more details, see below documents: + +Paper: + +The algorithm is further described in detail in the following two +SIGCOMM/SIGMETRICS papers: + + i) Mohammad Alizadeh, Albert Greenberg, David A. Maltz, Jitendra Padhye, + Parveen Patel, Balaji Prabhakar, Sudipta Sengupta, and Murari Sridharan: + "Data Center TCP (DCTCP)", Data Center Networks session + Proc. ACM SIGCOMM, New Delhi, 2010. + http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf + http://www.sigcomm.org/ccr/papers/2010/October/1851275.1851192 + +ii) Mohammad Alizadeh, Adel Javanmard, and Balaji Prabhakar: + "Analysis of DCTCP: Stability, Convergence, and Fairness" + Proc. ACM SIGMETRICS, San Jose, 2011. + http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp_analysis-full.pdf + +IETF informational draft: + + http://tools.ietf.org/html/draft-bensley-tcpm-dctcp-00 + +DCTCP site: + + http://simula.stanford.edu/~alizade/Site/DCTCP.html diff --git a/include/net/tcp.h b/include/net/tcp.h index 02a9a2c366bfe6937a0228cee8c21efb1373cada..1f57c536349251f5e0cf1847a9518c0b51ccaeb1 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -733,23 +733,6 @@ struct tcp_skb_cb { #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0])) -/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set - * - * If we receive a SYN packet with these bits set, it means a network is - * playing bad games with TOS bits. In order to avoid possible false congestion - * notifications, we disable TCP ECN negociation. - */ -static inline void -TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb, - struct net *net) -{ - const struct tcphdr *th = tcp_hdr(skb); - - if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr && - INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield)) - inet_rsk(req)->ecn_ok = 1; -} - /* Due to TSO, an SKB can be composed of multiple actual * packets. To keep these tracked properly, we use this. */ @@ -780,8 +763,17 @@ enum tcp_ca_event { CA_EVENT_CWND_RESTART, /* congestion window restart */ CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */ CA_EVENT_LOSS, /* loss timeout */ - CA_EVENT_FAST_ACK, /* in sequence ack */ - CA_EVENT_SLOW_ACK, /* other ack */ + CA_EVENT_ECN_NO_CE, /* ECT set, but not CE marked */ + CA_EVENT_ECN_IS_CE, /* received CE marked IP packet */ + CA_EVENT_DELAYED_ACK, /* Delayed ack is sent */ + CA_EVENT_NON_DELAYED_ACK, +}; + +/* Information about inbound ACK, passed to cong_ops->in_ack_event() */ +enum tcp_ca_ack_event_flags { + CA_ACK_SLOWPATH = (1 << 0), /* In slow path processing */ + CA_ACK_WIN_UPDATE = (1 << 1), /* ACK updated window */ + CA_ACK_ECE = (1 << 2), /* ECE bit is set on ack */ }; /* @@ -791,7 +783,10 @@ enum tcp_ca_event { #define TCP_CA_MAX 128 #define TCP_CA_BUF_MAX (TCP_CA_NAME_MAX*TCP_CA_MAX) +/* Algorithm can be set on socket without CAP_NET_ADMIN privileges */ #define TCP_CONG_NON_RESTRICTED 0x1 +/* Requires ECN/ECT set on all packets */ +#define TCP_CONG_NEEDS_ECN 0x2 struct tcp_congestion_ops { struct list_head list; @@ -810,6 +805,8 @@ struct tcp_congestion_ops { void (*set_state)(struct sock *sk, u8 new_state); /* call when cwnd event occurs (optional) */ void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev); + /* call when ack arrives (optional) */ + void (*in_ack_event)(struct sock *sk, u32 flags); /* new value of cwnd after loss (optional) */ u32 (*undo_cwnd)(struct sock *sk); /* hook for packet ack accounting (optional) */ @@ -824,6 +821,7 @@ struct tcp_congestion_ops { int tcp_register_congestion_control(struct tcp_congestion_ops *type); void tcp_unregister_congestion_control(struct tcp_congestion_ops *type); +void tcp_assign_congestion_control(struct sock *sk); void tcp_init_congestion_control(struct sock *sk); void tcp_cleanup_congestion_control(struct sock *sk); int tcp_set_default_congestion_control(const char *name); @@ -835,11 +833,17 @@ int tcp_set_congestion_control(struct sock *sk, const char *name); int tcp_slow_start(struct tcp_sock *tp, u32 acked); void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w); -extern struct tcp_congestion_ops tcp_init_congestion_ops; u32 tcp_reno_ssthresh(struct sock *sk); void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked); extern struct tcp_congestion_ops tcp_reno; +static inline bool tcp_ca_needs_ecn(const struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + + return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN; +} + static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state) { struct inet_connection_sock *icsk = inet_csk(sk); @@ -857,6 +861,40 @@ static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event) icsk->icsk_ca_ops->cwnd_event(sk, event); } +/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set + * + * If we receive a SYN packet with these bits set, it means a + * network is playing bad games with TOS bits. In order to + * avoid possible false congestion notifications, we disable + * TCP ECN negociation. + * + * Exception: tcp_ca wants ECN. This is required for DCTCP + * congestion control; it requires setting ECT on all packets, + * including SYN. We inverse the test in this case: If our + * local socket wants ECN, but peer only set ece/cwr (but not + * ECT in IP header) its probably a non-DCTCP aware sender. + */ +static inline void +TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb, + const struct sock *listen_sk) +{ + const struct tcphdr *th = tcp_hdr(skb); + const struct net *net = sock_net(listen_sk); + bool th_ecn = th->ece && th->cwr; + bool ect, need_ecn; + + if (!th_ecn) + return; + + ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield); + need_ecn = tcp_ca_needs_ecn(listen_sk); + + if (!ect && !need_ecn && net->ipv4.sysctl_tcp_ecn) + inet_rsk(req)->ecn_ok = 1; + else if (ect && need_ecn) + inet_rsk(req)->ecn_ok = 1; +} + /* These functions determine how the current flow behaves in respect of SACK * handling. SACK is negotiated with the peer, and therefore it can vary * between different flows. diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h index bbde90fa58380bb6d6940d9ec7454af7a4d55608..d65c0a09efd32041e3dd07ff80d0a421f0de6ae8 100644 --- a/include/uapi/linux/inet_diag.h +++ b/include/uapi/linux/inet_diag.h @@ -110,10 +110,10 @@ enum { INET_DIAG_TCLASS, INET_DIAG_SKMEMINFO, INET_DIAG_SHUTDOWN, + INET_DIAG_DCTCPINFO, }; -#define INET_DIAG_MAX INET_DIAG_SHUTDOWN - +#define INET_DIAG_MAX INET_DIAG_DCTCPINFO /* INET_DIAG_MEM */ @@ -133,5 +133,14 @@ struct tcpvegas_info { __u32 tcpv_minrtt; }; +/* INET_DIAG_DCTCPINFO */ + +struct tcp_dctcp_info { + __u16 dctcp_enabled; + __u16 dctcp_ce_state; + __u32 dctcp_alpha; + __u32 dctcp_ab_ecn; + __u32 dctcp_ab_tot; +}; #endif /* _UAPI_INET_DIAG_H_ */ diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig index 84f710b7472a922c74b51ef3a33d8711ee618d9a..69fb37854449b002076d1de2cf66f9b18e2eac9a 100644 --- a/net/ipv4/Kconfig +++ b/net/ipv4/Kconfig @@ -570,6 +570,27 @@ config TCP_CONG_ILLINOIS For further details see: http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html +config TCP_CONG_DCTCP + tristate "DataCenter TCP (DCTCP)" + default n + ---help--- + DCTCP leverages Explicit Congestion Notification (ECN) in the network to + provide multi-bit feedback to the end hosts. It is designed to provide: + + - High burst tolerance (incast due to partition/aggregate), + - Low latency (short flows, queries), + - High throughput (continuous data updates, large file transfers) with + commodity, shallow-buffered switches. + + All switches in the data center network running DCTCP must support + ECN marking and be configured for marking when reaching defined switch + buffer thresholds. The default ECN marking threshold heuristic for + DCTCP on switches is 20 packets (30KB) at 1Gbps, and 65 packets + (~100KB) at 10Gbps, but might need further careful tweaking. + + For further details see: + http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf + choice prompt "Default TCP congestion control" default DEFAULT_CUBIC @@ -598,9 +619,11 @@ choice config DEFAULT_WESTWOOD bool "Westwood" if TCP_CONG_WESTWOOD=y + config DEFAULT_DCTCP + bool "DCTCP" if TCP_CONG_DCTCP=y + config DEFAULT_RENO bool "Reno" - endchoice endif @@ -620,6 +643,7 @@ config DEFAULT_TCP_CONG default "westwood" if DEFAULT_WESTWOOD default "veno" if DEFAULT_VENO default "reno" if DEFAULT_RENO + default "dctcp" if DEFAULT_DCTCP default "cubic" config TCP_MD5SIG diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile index d78d404c596f4a64d80a184108ead5111cdf3e4c..d8105787c199e857795657a6769dcedeaf49994d 100644 --- a/net/ipv4/Makefile +++ b/net/ipv4/Makefile @@ -43,6 +43,7 @@ obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o obj-$(CONFIG_NET_TCPPROBE) += tcp_probe.o obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o +obj-$(CONFIG_TCP_CONG_DCTCP) += tcp_dctcp.o obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 87289e51be00ba8274d298241c04ec30368776d6..cf5e508e1ef55cdeafe308d59774850957debf3b 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -405,7 +405,7 @@ void tcp_init_sock(struct sock *sk) tp->reordering = sysctl_tcp_reordering; tcp_enable_early_retrans(tp); - icsk->icsk_ca_ops = &tcp_init_congestion_ops; + tcp_assign_congestion_control(sk); tp->tsoffset = 0; @@ -3258,8 +3258,6 @@ void __init tcp_init(void) tcp_hashinfo.ehash_mask + 1, tcp_hashinfo.bhash_size); tcp_metrics_init(); - - tcp_register_congestion_control(&tcp_reno); - + BUG_ON(tcp_register_congestion_control(&tcp_reno) != 0); tcp_tasklet_init(); } diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 80248f56c89f0b3dc8481aea2212fac819924772..a6c8a5775624ca844a9bb819c5a329dc1da22be4 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -74,24 +74,34 @@ void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); /* Assign choice of congestion control. */ -void tcp_init_congestion_control(struct sock *sk) +void tcp_assign_congestion_control(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_congestion_ops *ca; - /* if no choice made yet assign the current value set as default */ - if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) { - rcu_read_lock(); - list_for_each_entry_rcu(ca, &tcp_cong_list, list) { - if (try_module_get(ca->owner)) { - icsk->icsk_ca_ops = ca; - break; - } - - /* fallback to next available */ + rcu_read_lock(); + list_for_each_entry_rcu(ca, &tcp_cong_list, list) { + if (likely(try_module_get(ca->owner))) { + icsk->icsk_ca_ops = ca; + goto out; } - rcu_read_unlock(); + /* Fallback to next available. The last really + * guaranteed fallback is Reno from this list. + */ } +out: + rcu_read_unlock(); + + /* Clear out private data before diag gets it and + * the ca has not been initialized. + */ + if (ca->get_info) + memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); +} + +void tcp_init_congestion_control(struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); if (icsk->icsk_ca_ops->init) icsk->icsk_ca_ops->init(sk); @@ -345,15 +355,3 @@ struct tcp_congestion_ops tcp_reno = { .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, }; - -/* Initial congestion control used (until SYN) - * really reno under another name so we can tell difference - * during tcp_set_default_congestion_control - */ -struct tcp_congestion_ops tcp_init_congestion_ops = { - .name = "", - .owner = THIS_MODULE, - .ssthresh = tcp_reno_ssthresh, - .cong_avoid = tcp_reno_cong_avoid, -}; -EXPORT_SYMBOL_GPL(tcp_init_congestion_ops); diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c new file mode 100644 index 0000000000000000000000000000000000000000..b504371af74209362e03bbae0770bcbafc3e9340 --- /dev/null +++ b/net/ipv4/tcp_dctcp.c @@ -0,0 +1,344 @@ +/* DataCenter TCP (DCTCP) congestion control. + * + * http://simula.stanford.edu/~alizade/Site/DCTCP.html + * + * This is an implementation of DCTCP over Reno, an enhancement to the + * TCP congestion control algorithm designed for data centers. DCTCP + * leverages Explicit Congestion Notification (ECN) in the network to + * provide multi-bit feedback to the end hosts. DCTCP's goal is to meet + * the following three data center transport requirements: + * + * - High burst tolerance (incast due to partition/aggregate) + * - Low latency (short flows, queries) + * - High throughput (continuous data updates, large file transfers) + * with commodity shallow buffered switches + * + * The algorithm is described in detail in the following two papers: + * + * 1) Mohammad Alizadeh, Albert Greenberg, David A. Maltz, Jitendra Padhye, + * Parveen Patel, Balaji Prabhakar, Sudipta Sengupta, and Murari Sridharan: + * "Data Center TCP (DCTCP)", Data Center Networks session + * Proc. ACM SIGCOMM, New Delhi, 2010. + * http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf + * + * 2) Mohammad Alizadeh, Adel Javanmard, and Balaji Prabhakar: + * "Analysis of DCTCP: Stability, Convergence, and Fairness" + * Proc. ACM SIGMETRICS, San Jose, 2011. + * http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp_analysis-full.pdf + * + * Initial prototype from Abdul Kabbani, Masato Yasuda and Mohammad Alizadeh. + * + * Authors: + * + * Daniel Borkmann + * Florian Westphal + * Glenn Judd + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or (at + * your option) any later version. + */ + +#include +#include +#include +#include + +#define DCTCP_MAX_ALPHA 1024U + +struct dctcp { + u32 acked_bytes_ecn; + u32 acked_bytes_total; + u32 prior_snd_una; + u32 prior_rcv_nxt; + u32 dctcp_alpha; + u32 next_seq; + u32 ce_state; + u32 delayed_ack_reserved; +}; + +static unsigned int dctcp_shift_g __read_mostly = 4; /* g = 1/2^4 */ +module_param(dctcp_shift_g, uint, 0644); +MODULE_PARM_DESC(dctcp_shift_g, "parameter g for updating dctcp_alpha"); + +static unsigned int dctcp_alpha_on_init __read_mostly = DCTCP_MAX_ALPHA; +module_param(dctcp_alpha_on_init, uint, 0644); +MODULE_PARM_DESC(dctcp_alpha_on_init, "parameter for initial alpha value"); + +static unsigned int dctcp_clamp_alpha_on_loss __read_mostly; +module_param(dctcp_clamp_alpha_on_loss, uint, 0644); +MODULE_PARM_DESC(dctcp_clamp_alpha_on_loss, + "parameter for clamping alpha on loss"); + +static struct tcp_congestion_ops dctcp_reno; + +static void dctcp_reset(const struct tcp_sock *tp, struct dctcp *ca) +{ + ca->next_seq = tp->snd_nxt; + + ca->acked_bytes_ecn = 0; + ca->acked_bytes_total = 0; +} + +static void dctcp_init(struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + if ((tp->ecn_flags & TCP_ECN_OK) || + (sk->sk_state == TCP_LISTEN || + sk->sk_state == TCP_CLOSE)) { + struct dctcp *ca = inet_csk_ca(sk); + + ca->prior_snd_una = tp->snd_una; + ca->prior_rcv_nxt = tp->rcv_nxt; + + ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA); + + ca->delayed_ack_reserved = 0; + ca->ce_state = 0; + + dctcp_reset(tp, ca); + return; + } + + /* No ECN support? Fall back to Reno. Also need to clear + * ECT from sk since it is set during 3WHS for DCTCP. + */ + inet_csk(sk)->icsk_ca_ops = &dctcp_reno; + INET_ECN_dontxmit(sk); +} + +static u32 dctcp_ssthresh(struct sock *sk) +{ + const struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(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); + + /* State has changed from CE=0 to CE=1 and delayed + * ACK has not sent yet. + */ + if (!ca->ce_state && ca->delayed_ack_reserved) { + u32 tmp_rcv_nxt; + + /* Save current rcv_nxt. */ + tmp_rcv_nxt = tp->rcv_nxt; + + /* Generate previous ack with CE=0. */ + tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; + tp->rcv_nxt = ca->prior_rcv_nxt; + + tcp_send_ack(sk); + + /* Recover current rcv_nxt. */ + tp->rcv_nxt = tmp_rcv_nxt; + } + + 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); + + /* State has changed from CE=1 to CE=0 and delayed + * ACK has not sent yet. + */ + if (ca->ce_state && ca->delayed_ack_reserved) { + u32 tmp_rcv_nxt; + + /* Save current rcv_nxt. */ + tmp_rcv_nxt = tp->rcv_nxt; + + /* Generate previous ack with CE=1. */ + tp->ecn_flags |= TCP_ECN_DEMAND_CWR; + tp->rcv_nxt = ca->prior_rcv_nxt; + + tcp_send_ack(sk); + + /* Recover current rcv_nxt. */ + tp->rcv_nxt = tmp_rcv_nxt; + } + + 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); + struct dctcp *ca = inet_csk_ca(sk); + u32 acked_bytes = tp->snd_una - ca->prior_snd_una; + + /* If ack did not advance snd_una, count dupack as MSS size. + * If ack did update window, do not count it at all. + */ + if (acked_bytes == 0 && !(flags & CA_ACK_WIN_UPDATE)) + acked_bytes = inet_csk(sk)->icsk_ack.rcv_mss; + if (acked_bytes) { + ca->acked_bytes_total += acked_bytes; + ca->prior_snd_una = tp->snd_una; + + if (flags & CA_ACK_ECE) + ca->acked_bytes_ecn += acked_bytes; + } + + /* Expired RTT */ + if (!before(tp->snd_una, ca->next_seq)) { + /* For avoiding denominator == 1. */ + if (ca->acked_bytes_total == 0) + ca->acked_bytes_total = 1; + + /* alpha = (1 - g) * alpha + g * F */ + ca->dctcp_alpha = ca->dctcp_alpha - + (ca->dctcp_alpha >> dctcp_shift_g) + + (ca->acked_bytes_ecn << (10U - dctcp_shift_g)) / + ca->acked_bytes_total; + + if (ca->dctcp_alpha > DCTCP_MAX_ALPHA) + /* Clamp dctcp_alpha to max. */ + ca->dctcp_alpha = DCTCP_MAX_ALPHA; + + dctcp_reset(tp, ca); + } +} + +static void dctcp_state(struct sock *sk, u8 new_state) +{ + if (dctcp_clamp_alpha_on_loss && new_state == TCP_CA_Loss) { + struct dctcp *ca = inet_csk_ca(sk); + + /* If this extension is enabled, we clamp dctcp_alpha to + * max on packet loss; the motivation is that dctcp_alpha + * is an indicator to the extend of congestion and packet + * loss is an indicator of extreme congestion; setting + * this in practice turned out to be beneficial, and + * effectively assumes total congestion which reduces the + * window by half. + */ + ca->dctcp_alpha = DCTCP_MAX_ALPHA; + } +} + +static void dctcp_update_ack_reserved(struct sock *sk, enum tcp_ca_event ev) +{ + struct dctcp *ca = inet_csk_ca(sk); + + switch (ev) { + case CA_EVENT_DELAYED_ACK: + if (!ca->delayed_ack_reserved) + ca->delayed_ack_reserved = 1; + break; + case CA_EVENT_NON_DELAYED_ACK: + if (ca->delayed_ack_reserved) + ca->delayed_ack_reserved = 0; + break; + default: + /* Don't care for the rest. */ + break; + } +} + +static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev) +{ + 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); + break; + case CA_EVENT_DELAYED_ACK: + case CA_EVENT_NON_DELAYED_ACK: + dctcp_update_ack_reserved(sk, ev); + break; + default: + /* Don't care for the rest. */ + break; + } +} + +static void dctcp_get_info(struct sock *sk, u32 ext, struct sk_buff *skb) +{ + const struct dctcp *ca = inet_csk_ca(sk); + + /* Fill it also in case of VEGASINFO due to req struct limits. + * We can still correctly retrieve it later. + */ + if (ext & (1 << (INET_DIAG_DCTCPINFO - 1)) || + ext & (1 << (INET_DIAG_VEGASINFO - 1))) { + struct tcp_dctcp_info info; + + memset(&info, 0, sizeof(info)); + if (inet_csk(sk)->icsk_ca_ops != &dctcp_reno) { + info.dctcp_enabled = 1; + info.dctcp_ce_state = (u16) ca->ce_state; + info.dctcp_alpha = ca->dctcp_alpha; + info.dctcp_ab_ecn = ca->acked_bytes_ecn; + info.dctcp_ab_tot = ca->acked_bytes_total; + } + + nla_put(skb, INET_DIAG_DCTCPINFO, sizeof(info), &info); + } +} + +static struct tcp_congestion_ops dctcp __read_mostly = { + .init = dctcp_init, + .in_ack_event = dctcp_update_alpha, + .cwnd_event = dctcp_cwnd_event, + .ssthresh = dctcp_ssthresh, + .cong_avoid = tcp_reno_cong_avoid, + .set_state = dctcp_state, + .get_info = dctcp_get_info, + .flags = TCP_CONG_NEEDS_ECN, + .owner = THIS_MODULE, + .name = "dctcp", +}; + +static struct tcp_congestion_ops dctcp_reno __read_mostly = { + .ssthresh = tcp_reno_ssthresh, + .cong_avoid = tcp_reno_cong_avoid, + .get_info = dctcp_get_info, + .owner = THIS_MODULE, + .name = "dctcp-reno", +}; + +static int __init dctcp_register(void) +{ + BUILD_BUG_ON(sizeof(struct dctcp) > ICSK_CA_PRIV_SIZE); + return tcp_register_congestion_control(&dctcp); +} + +static void __exit dctcp_unregister(void) +{ + tcp_unregister_congestion_control(&dctcp); +} + +module_init(dctcp_register); +module_exit(dctcp_unregister); + +MODULE_AUTHOR("Daniel Borkmann "); +MODULE_AUTHOR("Florian Westphal "); +MODULE_AUTHOR("Glenn Judd "); + +MODULE_LICENSE("GPL v2"); +MODULE_DESCRIPTION("DataCenter TCP (DCTCP)"); diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 5073eefa6fae0caf4fd2bcd89c873279f77a2f36..fc133178c787484c5d58e0bf52036de7302efb10 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; } } @@ -3362,6 +3369,14 @@ static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag) } } +static inline void tcp_in_ack_event(struct sock *sk, u32 flags) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + + if (icsk->icsk_ca_ops->in_ack_event) + icsk->icsk_ca_ops->in_ack_event(sk, flags); +} + /* This routine deals with incoming acks, but not outgoing ones. */ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) { @@ -3421,10 +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_ca_event(sk, CA_EVENT_FAST_ACK); + 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 @@ -3436,10 +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_ca_event(sk, CA_EVENT_SLOW_ACK); + tcp_in_ack_event(sk, ack_ev_flags); } /* We passed data and got it acked, remove any soft error @@ -5944,7 +5966,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, goto drop_and_free; if (!want_cookie || tmp_opt.tstamp_ok) - TCP_ECN_create_request(req, skb, sock_net(sk)); + TCP_ECN_create_request(req, skb, sk); if (want_cookie) { isn = cookie_init_sequence(af_ops, sk, skb, &req->mss); diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index a058f411d3a6bd1441282e39da5d34152435513e..47b73506b77e40ba43afa2fac0b7c943fb669acc 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -451,9 +451,8 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, newtp->snd_cwnd = TCP_INIT_CWND; newtp->snd_cwnd_cnt = 0; - if (newicsk->icsk_ca_ops != &tcp_init_congestion_ops && - !try_module_get(newicsk->icsk_ca_ops->owner)) - newicsk->icsk_ca_ops = &tcp_init_congestion_ops; + if (!try_module_get(newicsk->icsk_ca_ops->owner)) + tcp_assign_congestion_control(newsk); tcp_set_ca_state(newsk, TCP_CA_Open); tcp_init_xmit_timers(newsk); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 4d92703df4c62457a914dc2603c7a6018fb75876..86a0216fcaa1c54ed25a2a56bba2647e156a935c 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. diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c index 81911a92356c6a7a50b63800dc070d6943c280f3..bb63fba47d47837b615c6bc6b730e36eead6328f 100644 --- a/net/ipv4/tcp_westwood.c +++ b/net/ipv4/tcp_westwood.c @@ -220,32 +220,35 @@ static u32 tcp_westwood_bw_rttmin(const struct sock *sk) return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2); } +static void tcp_westwood_ack(struct sock *sk, u32 ack_flags) +{ + if (ack_flags & CA_ACK_SLOWPATH) { + struct westwood *w = inet_csk_ca(sk); + + westwood_update_window(sk); + w->bk += westwood_acked_count(sk); + + update_rtt_min(w); + return; + } + + westwood_fast_bw(sk); +} + static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event) { struct tcp_sock *tp = tcp_sk(sk); struct westwood *w = inet_csk_ca(sk); switch (event) { - case CA_EVENT_FAST_ACK: - westwood_fast_bw(sk); - break; - case CA_EVENT_COMPLETE_CWR: tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk); break; - case CA_EVENT_LOSS: tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk); /* Update RTT_min when next ack arrives */ w->reset_rtt_min = 1; break; - - case CA_EVENT_SLOW_ACK: - westwood_update_window(sk); - w->bk += westwood_acked_count(sk); - update_rtt_min(w); - break; - default: /* don't care */ break; @@ -274,6 +277,7 @@ static struct tcp_congestion_ops tcp_westwood __read_mostly = { .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, .cwnd_event = tcp_westwood_event, + .in_ack_event = tcp_westwood_ack, .get_info = tcp_westwood_info, .pkts_acked = tcp_westwood_pkts_acked,