From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- net/ipv4/tcp_dctcp.c | 306 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 306 insertions(+) create mode 100644 net/ipv4/tcp_dctcp.c (limited to 'net/ipv4/tcp_dctcp.c') diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c new file mode 100644 index 000000000..bb23bb5b3 --- /dev/null +++ b/net/ipv4/tcp_dctcp.c @@ -0,0 +1,306 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* 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 + */ + +#include +#include +#include +#include +#include +#include +#include "tcp_dctcp.h" + +#define DCTCP_MAX_ALPHA 1024U + +struct dctcp { + u32 old_delivered; + u32 old_delivered_ce; + u32 prior_rcv_nxt; + u32 dctcp_alpha; + u32 next_seq; + u32 ce_state; + u32 loss_cwnd; + struct tcp_plb_state plb; +}; + +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 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->old_delivered = tp->delivered; + ca->old_delivered_ce = tp->delivered_ce; +} + +__bpf_kfunc 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_rcv_nxt = tp->rcv_nxt; + + ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA); + + ca->loss_cwnd = 0; + ca->ce_state = 0; + + dctcp_reset(tp, ca); + tcp_plb_init(sk, &ca->plb); + + 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); +} + +__bpf_kfunc static u32 dctcp_ssthresh(struct sock *sk) +{ + struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); + + ca->loss_cwnd = tcp_snd_cwnd(tp); + return max(tcp_snd_cwnd(tp) - ((tcp_snd_cwnd(tp) * ca->dctcp_alpha) >> 11U), 2U); +} + +__bpf_kfunc 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); + + /* Expired RTT */ + if (!before(tp->snd_una, ca->next_seq)) { + u32 delivered = tp->delivered - ca->old_delivered; + u32 delivered_ce = tp->delivered_ce - ca->old_delivered_ce; + u32 alpha = ca->dctcp_alpha; + u32 ce_ratio = 0; + + if (delivered > 0) { + /* dctcp_alpha keeps EWMA of fraction of ECN marked + * packets. Because of EWMA smoothing, PLB reaction can + * be slow so we use ce_ratio which is an instantaneous + * measure of congestion. ce_ratio is the fraction of + * ECN marked packets in the previous RTT. + */ + if (delivered_ce > 0) + ce_ratio = (delivered_ce << TCP_PLB_SCALE) / delivered; + tcp_plb_update_state(sk, &ca->plb, (int)ce_ratio); + tcp_plb_check_rehash(sk, &ca->plb); + } + + /* alpha = (1 - g) * alpha + g * F */ + + alpha -= min_not_zero(alpha, alpha >> dctcp_shift_g); + if (delivered_ce) { + + /* If dctcp_shift_g == 1, a 32bit value would overflow + * after 8 M packets. + */ + delivered_ce <<= (10 - dctcp_shift_g); + delivered_ce /= max(1U, delivered); + + alpha = min(alpha + delivered_ce, DCTCP_MAX_ALPHA); + } + /* dctcp_alpha can be read from dctcp_get_info() without + * synchro, so we ask compiler to not use dctcp_alpha + * as a temporary variable in prior operations. + */ + WRITE_ONCE(ca->dctcp_alpha, alpha); + dctcp_reset(tp, ca); + } +} + +static void dctcp_react_to_loss(struct sock *sk) +{ + struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); + + ca->loss_cwnd = tcp_snd_cwnd(tp); + tp->snd_ssthresh = max(tcp_snd_cwnd(tp) >> 1U, 2U); +} + +__bpf_kfunc static void dctcp_state(struct sock *sk, u8 new_state) +{ + if (new_state == TCP_CA_Recovery && + new_state != inet_csk(sk)->icsk_ca_state) + dctcp_react_to_loss(sk); + /* We handle RTO in dctcp_cwnd_event to ensure that we perform only + * one loss-adjustment per RTT. + */ +} + +__bpf_kfunc 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: + case CA_EVENT_ECN_NO_CE: + dctcp_ece_ack_update(sk, ev, &ca->prior_rcv_nxt, &ca->ce_state); + break; + case CA_EVENT_LOSS: + tcp_plb_update_state_upon_rto(sk, &ca->plb); + dctcp_react_to_loss(sk); + break; + case CA_EVENT_TX_START: + tcp_plb_check_rehash(sk, &ca->plb); /* Maybe rehash when inflight is 0 */ + break; + default: + /* Don't care for the rest. */ + break; + } +} + +static size_t dctcp_get_info(struct sock *sk, u32 ext, int *attr, + union tcp_cc_info *info) +{ + const struct dctcp *ca = inet_csk_ca(sk); + const struct tcp_sock *tp = tcp_sk(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))) { + memset(&info->dctcp, 0, sizeof(info->dctcp)); + if (inet_csk(sk)->icsk_ca_ops != &dctcp_reno) { + info->dctcp.dctcp_enabled = 1; + info->dctcp.dctcp_ce_state = (u16) ca->ce_state; + info->dctcp.dctcp_alpha = ca->dctcp_alpha; + info->dctcp.dctcp_ab_ecn = tp->mss_cache * + (tp->delivered_ce - ca->old_delivered_ce); + info->dctcp.dctcp_ab_tot = tp->mss_cache * + (tp->delivered - ca->old_delivered); + } + + *attr = INET_DIAG_DCTCPINFO; + return sizeof(info->dctcp); + } + return 0; +} + +__bpf_kfunc static u32 dctcp_cwnd_undo(struct sock *sk) +{ + const struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); + + return max(tcp_snd_cwnd(tp), ca->loss_cwnd); +} + +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, + .undo_cwnd = dctcp_cwnd_undo, + .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, + .undo_cwnd = tcp_reno_undo_cwnd, + .get_info = dctcp_get_info, + .owner = THIS_MODULE, + .name = "dctcp-reno", +}; + +BTF_SET8_START(tcp_dctcp_check_kfunc_ids) +#ifdef CONFIG_X86 +#ifdef CONFIG_DYNAMIC_FTRACE +BTF_ID_FLAGS(func, dctcp_init) +BTF_ID_FLAGS(func, dctcp_update_alpha) +BTF_ID_FLAGS(func, dctcp_cwnd_event) +BTF_ID_FLAGS(func, dctcp_ssthresh) +BTF_ID_FLAGS(func, dctcp_cwnd_undo) +BTF_ID_FLAGS(func, dctcp_state) +#endif +#endif +BTF_SET8_END(tcp_dctcp_check_kfunc_ids) + +static const struct btf_kfunc_id_set tcp_dctcp_kfunc_set = { + .owner = THIS_MODULE, + .set = &tcp_dctcp_check_kfunc_ids, +}; + +static int __init dctcp_register(void) +{ + int ret; + + BUILD_BUG_ON(sizeof(struct dctcp) > ICSK_CA_PRIV_SIZE); + + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &tcp_dctcp_kfunc_set); + if (ret < 0) + return ret; + 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)"); -- cgit v1.2.3