From: Ilpo Järvinen ij@kernel.org
The Accurate ECN allows echoing back the sum of bytes for each IP ECN field value in the received packets using AccECN option. This change implements AccECN option tx & rx side processing without option send control related features that are added by a later change.
Based on specification: https://tools.ietf.org/id/draft-ietf-tcpm-accurate-ecn-28.txt (Some features of the spec will be added in the later changes rather than in this one).
A full-length AccECN option is always attempted but if it does not fit, the minimum length is selected based on the counters that have changed since the last update. The AccECN option (with 24-bit fields) often ends in odd sizes so the option write code tries to take advantage of some nop used to pad the other TCP options.
The delivered_ecn_bytes pairs with received_ecn_bytes similar to how delivered_ce pairs with received_ce. In contrast to ACE field, however, the option is not always available to update delivered_ecn_bytes. For ACK w/o AccECN option, the delivered bytes calculated based on the cumulative ACK+SACK information are assigned to one of the counters using an estimation heuristic to select the most likely ECN byte counter. Any estimation error is corrected when the next AccECN option arrives. It may occur that the heuristic gets too confused when there are enough different byte counter deltas between ACKs with the AccECN option in which case the heuristic just gives up on updating the counters for a while.
tcp_ecn_option sysctl can be used to select option sending mode for AccECN: TCP_ECN_OPTION_DISABLED, TCP_ECN_OPTION_MINIMUM, and TCP_ECN_OPTION_FULL.
This patch increases the size of tcp_info struct, as there is no existing holes for new u32 variables. Below are the pahole outcomes before and after this patch:
[BEFORE THIS PATCH] struct tcp_info { [...] __u32 tcpi_total_rto_time; /* 244 4 */
/* size: 248, cachelines: 4, members: 61 */ }
[AFTER THIS PATCH] struct tcp_info { [...] __u32 tcpi_total_rto_time; /* 244 4 */ __u32 tcpi_received_ce; /* 248 4 */ __u32 tcpi_delivered_e1_bytes; /* 252 4 */ __u32 tcpi_delivered_e0_bytes; /* 256 4 */ __u32 tcpi_delivered_ce_bytes; /* 260 4 */ __u32 tcpi_received_e1_bytes; /* 264 4 */ __u32 tcpi_received_e0_bytes; /* 268 4 */ __u32 tcpi_received_ce_bytes; /* 272 4 */
/* size: 280, cachelines: 5, members: 68 */ }
This patch uses the existing 1-byte holes in the tcp_sock_write_txrx group for new u8 members, but adds a 4-byte hole in tcp_sock_write_rx group after the new u32 delivered_ecn_bytes[3] member. Therefore, the group size of tcp_sock_write_rx is increased from 96 to 112. Below are the pahole outcomes before and after this patch:
[BEFORE THIS PATCH] struct tcp_sock { [...] u8 received_ce_pending:4; /* 2586: 0 1 */ u8 unused2:4; /* 2586: 4 1 */ /* XXX 1 byte hole, try to pack */
[...] u32 rcv_rtt_last_tsecr; /* 2732 4 */
[...] __cacheline_group_end__tcp_sock_write_rx[0]; /* 2792 0 */
[...] /* size: 3264, cachelines: 51, members: 170 */ }
[AFTER THIS PATCH] struct tcp_sock { [...] u8 received_ce_pending:4;/* 2586: 0 1 */ u8 unused2:4; /* 2586: 4 1 */ u8 accecn_minlen:2; /* 2587: 0 1 */ u8 est_ecnfield:2; /* 2587: 2 1 */ u8 unused3:4; /* 2587: 4 1 */
[...] u32 rcv_rtt_last_tsecr; /* 2732 4 */ u32 delivered_ecn_bytes[3];/* 2736 12 */ /* XXX 4 bytes hole, try to pack */
[...] __cacheline_group_end__tcp_sock_write_rx[0]; /* 2808 0 */
[...] /* size: 3264, cachelines: 51, members: 174 */ }
Signed-off-by: Ilpo Järvinen ij@kernel.org Signed-off-by: Neal Cardwell ncardwell@google.com Co-developed-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com Signed-off-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
--- v13 - Move TCP_ACCECN_E1B_INIT_OFFSET, TCP_ACCECN_E0B_INIT_OFFSET, and TCP_ACCECN_CEB_INIT_OFFSET to this patch - Use static array lookup in tcp_accecn_optfield_to_ecnfield() - Return false when WARN_ON_ONCE() is true in tcp_accecn_process_option() - Make synack_ecn_bytes as static const array and use const u32 pointer in tcp_options_write() - Use ALIGN() and ALIGN_DOWN() in tcp_options_fit_accecn() to pad TCP AccECN option to dword
v10 - Add documentation of tcp_ecn_option in ip-sysctl.rst to this patch - Remove the global variable u32 synack_ecn_bytes[3] - Add READ_ONCE() over every reads of sysctl
v9: - Restruct the code in the for loop of tcp_accecn_process_option() - Remove ecn_bytes and add use_synack_ecn_bytes flag in tcp_out_options struct to identify whether syn_ack_bytes or received_ecn_bytes is used - Replace leftover_bytes and leftover_size with leftover_highbyte and leftover_lowbyte and add comments in tcp_options_write()
v8: - Reset leftover_size to 2 once leftover_bytes is used --- Documentation/networking/ip-sysctl.rst | 19 ++ .../networking/net_cachelines/tcp_sock.rst | 3 + include/linux/tcp.h | 9 +- include/net/netns/ipv4.h | 1 + include/net/tcp.h | 13 ++ include/net/tcp_ecn.h | 89 +++++++++- include/uapi/linux/tcp.h | 7 + net/ipv4/sysctl_net_ipv4.c | 9 + net/ipv4/tcp.c | 15 +- net/ipv4/tcp_input.c | 94 +++++++++- net/ipv4/tcp_ipv4.c | 1 + net/ipv4/tcp_output.c | 165 +++++++++++++++++- 12 files changed, 412 insertions(+), 13 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 8495a59683d2..b9da5c96eb2d 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -468,6 +468,25 @@ tcp_ecn - INTEGER
Default: 2
+tcp_ecn_option - INTEGER + Control Accurate ECN (AccECN) option sending when AccECN has been + successfully negotiated during handshake. Send logic inhibits + sending AccECN options regarless of this setting when no AccECN + option has been seen for the reverse direction. + + Possible values are: + + = ============================================================ + 0 Never send AccECN option. This also disables sending AccECN + option in SYN/ACK during handshake. + 1 Send AccECN option sparingly according to the minimum option + rules outlined in draft-ietf-tcpm-accurate-ecn. + 2 Send AccECN option on every packet whenever it fits into TCP + option space. + = ============================================================ + + Default: 2 + tcp_ecn_fallback - BOOLEAN If the kernel detects that ECN connection misbehaves, enable fall back to non-ECN. Currently, this knob implements the fallback diff --git a/Documentation/networking/net_cachelines/tcp_sock.rst b/Documentation/networking/net_cachelines/tcp_sock.rst index 5a2b0af57364..b941151f8c0a 100644 --- a/Documentation/networking/net_cachelines/tcp_sock.rst +++ b/Documentation/networking/net_cachelines/tcp_sock.rst @@ -104,8 +104,11 @@ u32 delivered_ce read_mostly read_w u32 received_ce read_mostly read_write u32[3] received_ecn_bytes read_mostly read_write u8:4 received_ce_pending read_mostly read_write +u32[3] delivered_ecn_bytes read_write u8:2 syn_ect_snt write_mostly read_write u8:2 syn_ect_rcv read_mostly read_write +u8:2 accecn_minlen write_mostly read_write +u8:2 est_ecnfield read_write u8:4 accecn_fail_mode u32 lost read_mostly tcp_ack u32 app_limited read_write read_mostly tcp_rate_check_app_limited,tcp_rate_skb_sent(tx);tcp_rate_gen(rx) diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 012d01347b3c..73557656cb2d 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -122,8 +122,9 @@ struct tcp_options_received { smc_ok : 1, /* SMC seen on SYN packet */ snd_wscale : 4, /* Window scaling received from sender */ rcv_wscale : 4; /* Window scaling to send to receiver */ - u8 saw_unknown:1, /* Received unknown option */ - unused:7; + u8 accecn:6, /* AccECN index in header, 0=no options */ + saw_unknown:1, /* Received unknown option */ + unused:1; u8 num_sacks; /* Number of SACK blocks */ u16 user_mss; /* mss requested by user in ioctl */ u16 mss_clamp; /* Maximal mss, negotiated at connection setup */ @@ -293,6 +294,9 @@ struct tcp_sock { rate_app_limited:1; /* rate_{delivered,interval_us} limited? */ u8 received_ce_pending:4, /* Not yet transmit cnt of received_ce */ unused2:4; + u8 accecn_minlen:2,/* Minimum length of AccECN option sent */ + est_ecnfield:2,/* ECN field for AccECN delivered estimates */ + unused3:4; __be32 pred_flags; u64 tcp_clock_cache; /* cache last tcp_clock_ns() (see tcp_mstamp_refresh()) */ u64 tcp_mstamp; /* most recent packet received/sent */ @@ -337,6 +341,7 @@ struct tcp_sock { u32 rate_delivered; /* saved rate sample: packets delivered */ u32 rate_interval_us; /* saved rate sample: time elapsed */ u32 rcv_rtt_last_tsecr; + u32 delivered_ecn_bytes[3]; u64 first_tx_mstamp; /* start of window send phase */ u64 delivered_mstamp; /* time we reached "delivered" */ u64 bytes_acked; /* RFC4898 tcpEStatsAppHCThruOctetsAcked diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 6373e3f17da8..4569a9ef4fb8 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -148,6 +148,7 @@ struct netns_ipv4 { struct local_ports ip_local_ports;
u8 sysctl_tcp_ecn; + u8 sysctl_tcp_ecn_option; u8 sysctl_tcp_ecn_fallback;
u8 sysctl_ip_default_ttl; diff --git a/include/net/tcp.h b/include/net/tcp.h index 916696515873..bdffe7b7f042 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -203,6 +203,8 @@ static_assert((1 << ATO_BITS) > TCP_DELACK_MAX); #define TCPOPT_AO 29 /* Authentication Option (RFC5925) */ #define TCPOPT_MPTCP 30 /* Multipath TCP (RFC6824) */ #define TCPOPT_FASTOPEN 34 /* Fast open (RFC7413) */ +#define TCPOPT_ACCECN0 172 /* 0xAC: Accurate ECN Order 0 */ +#define TCPOPT_ACCECN1 174 /* 0xAE: Accurate ECN Order 1 */ #define TCPOPT_EXP 254 /* Experimental */ /* Magic number to be after the option value for sharing TCP * experimental options. See draft-ietf-tcpm-experimental-options-00.txt @@ -220,6 +222,7 @@ static_assert((1 << ATO_BITS) > TCP_DELACK_MAX); #define TCPOLEN_TIMESTAMP 10 #define TCPOLEN_MD5SIG 18 #define TCPOLEN_FASTOPEN_BASE 2 +#define TCPOLEN_ACCECN_BASE 2 #define TCPOLEN_EXP_FASTOPEN_BASE 4 #define TCPOLEN_EXP_SMC_BASE 6
@@ -233,6 +236,13 @@ static_assert((1 << ATO_BITS) > TCP_DELACK_MAX); #define TCPOLEN_MD5SIG_ALIGNED 20 #define TCPOLEN_MSS_ALIGNED 4 #define TCPOLEN_EXP_SMC_BASE_ALIGNED 8 +#define TCPOLEN_ACCECN_PERFIELD 3 + +/* Maximum number of byte counters in AccECN option + size */ +#define TCP_ACCECN_NUMFIELDS 3 +#define TCP_ACCECN_MAXSIZE (TCPOLEN_ACCECN_BASE + \ + TCPOLEN_ACCECN_PERFIELD * \ + TCP_ACCECN_NUMFIELDS)
/* Flags in tp->nonagle */ #define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */ @@ -971,6 +981,9 @@ static inline u32 tcp_rsk_tsval(const struct tcp_request_sock *treq) * See draft-ietf-tcpm-accurate-ecn for the latest values. */ #define TCP_ACCECN_CEP_INIT_OFFSET 5 +#define TCP_ACCECN_E1B_INIT_OFFSET 1 +#define TCP_ACCECN_E0B_INIT_OFFSET 1 +#define TCP_ACCECN_CEB_INIT_OFFSET 0
/* State flags for sacked in struct tcp_skb_cb */ enum tcp_skb_cb_sacked_flags { diff --git a/include/net/tcp_ecn.h b/include/net/tcp_ecn.h index 97b2dd79c883..6bf5b3b7c648 100644 --- a/include/net/tcp_ecn.h +++ b/include/net/tcp_ecn.h @@ -24,6 +24,13 @@ enum tcp_ecn_mode { TCP_ECN_IN_ACCECN_OUT_NOECN = 5, };
+/* AccECN option sending when AccECN has been successfully negotiated */ +enum tcp_accecn_option { + TCP_ACCECN_OPTION_DISABLED = 0, + TCP_ACCECN_OPTION_MINIMUM = 1, + TCP_ACCECN_OPTION_FULL = 2, +}; + static inline void tcp_ecn_queue_cwr(struct tcp_sock *tp) { /* Do not set CWR if in AccECN mode! */ @@ -169,6 +176,79 @@ static inline void tcp_accecn_third_ack(struct sock *sk, } }
+/* Maps IP ECN field ECT/CE code point to AccECN option field number, given + * we are sending fields with Accurate ECN Order 1: ECT(1), CE, ECT(0). + */ +static inline u8 tcp_ecnfield_to_accecn_optfield(u8 ecnfield) +{ + switch (ecnfield & INET_ECN_MASK) { + case INET_ECN_NOT_ECT: + return 0; /* AccECN does not send counts of NOT_ECT */ + case INET_ECN_ECT_1: + return 1; + case INET_ECN_CE: + return 2; + case INET_ECN_ECT_0: + return 3; + } + return 0; +} + +/* Maps IP ECN field ECT/CE code point to AccECN option field value offset. + * Some fields do not start from zero, to detect zeroing by middleboxes. + */ +static inline u32 tcp_accecn_field_init_offset(u8 ecnfield) +{ + switch (ecnfield & INET_ECN_MASK) { + case INET_ECN_NOT_ECT: + return 0; /* AccECN does not send counts of NOT_ECT */ + case INET_ECN_ECT_1: + return TCP_ACCECN_E1B_INIT_OFFSET; + case INET_ECN_CE: + return TCP_ACCECN_CEB_INIT_OFFSET; + case INET_ECN_ECT_0: + return TCP_ACCECN_E0B_INIT_OFFSET; + } + return 0; +} + +/* Maps AccECN option field #nr to IP ECN field ECT/CE bits */ +static inline unsigned int tcp_accecn_optfield_to_ecnfield(unsigned int option, + bool order) +{ + /* Based on Table 5 of the AccECN spec to map (option, order) to + * the corresponding ECN conuters (ECT-1, ECT-0, or CE). + */ + static const u8 optfield_lookup[2][3] = { + /* order = 0: 1st field ECT-0, 2nd field CE, 3rd field ECT-1 */ + { INET_ECN_ECT_0, INET_ECN_CE, INET_ECN_ECT_1 }, + /* order = 1: 1st field ECT-1, 2nd field CE, 3rd field ECT-0 */ + { INET_ECN_ECT_1, INET_ECN_CE, INET_ECN_ECT_0 } + }; + + return optfield_lookup[order][option % 3]; +} + +/* Handles AccECN option ECT and CE 24-bit byte counters update into + * the u32 value in tcp_sock. As we're processing TCP options, it is + * safe to access from - 1. + */ +static inline s32 tcp_update_ecn_bytes(u32 *cnt, const char *from, + u32 init_offset) +{ + u32 truncated = (get_unaligned_be32(from - 1) - init_offset) & + 0xFFFFFFU; + u32 delta = (truncated - *cnt) & 0xFFFFFFU; + + /* If delta has the highest bit set (24th bit) indicating + * negative, sign extend to correct an estimation using + * sign_extend32(delta, 24 - 1) + */ + delta = sign_extend32(delta, 23); + *cnt += delta; + return (s32)delta; +} + /* Updates Accurate ECN received counters from the received IP ECN field */ static inline void tcp_ecn_received_counters(struct sock *sk, const struct sk_buff *skb, u32 len) @@ -192,8 +272,12 @@ static inline void tcp_ecn_received_counters(struct sock *sk, tp->received_ce_pending = min(tp->received_ce_pending + pcount, 0xfU);
- if (len > 0) + if (len > 0) { + u8 minlen = tcp_ecnfield_to_accecn_optfield(ecnfield); tp->received_ecn_bytes[ecnfield - 1] += len; + tp->accecn_minlen = max_t(u8, tp->accecn_minlen, + minlen); + } } }
@@ -263,6 +347,9 @@ static inline void tcp_accecn_init_counters(struct tcp_sock *tp) tp->received_ce = 0; tp->received_ce_pending = 0; __tcp_accecn_init_bytes_counters(tp->received_ecn_bytes); + __tcp_accecn_init_bytes_counters(tp->delivered_ecn_bytes); + tp->accecn_minlen = 0; + tp->est_ecnfield = 0; }
/* Used for make_synack to form the ACE flags */ diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index bdac8c42fa82..53e0e85b52be 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -316,6 +316,13 @@ struct tcp_info { * in milliseconds, including any * unfinished recovery. */ + __u32 tcpi_received_ce; /* # of CE marks received */ + __u32 tcpi_delivered_e1_bytes; /* Accurate ECN byte counters */ + __u32 tcpi_delivered_e0_bytes; + __u32 tcpi_delivered_ce_bytes; + __u32 tcpi_received_e1_bytes; + __u32 tcpi_received_e0_bytes; + __u32 tcpi_received_ce_bytes; };
/* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */ diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 75ec1a599b52..1d7fd86ca7b9 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -731,6 +731,15 @@ static struct ctl_table ipv4_net_table[] = { .extra1 = SYSCTL_ZERO, .extra2 = &tcp_ecn_mode_max, }, + { + .procname = "tcp_ecn_option", + .data = &init_net.ipv4.sysctl_tcp_ecn_option, + .maxlen = sizeof(u8), + .mode = 0644, + .proc_handler = proc_dou8vec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_TWO, + }, { .procname = "tcp_ecn_fallback", .data = &init_net.ipv4.sysctl_tcp_ecn_fallback, diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 6255b2d4c6c5..5cc5b9a906a1 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -270,6 +270,7 @@
#include <net/icmp.h> #include <net/inet_common.h> +#include <net/inet_ecn.h> #include <net/tcp.h> #include <net/tcp_ecn.h> #include <net/mptcp.h> @@ -4140,6 +4141,9 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) { const struct tcp_sock *tp = tcp_sk(sk); /* iff sk_type == SOCK_STREAM */ const struct inet_connection_sock *icsk = inet_csk(sk); + const u8 ect1_idx = INET_ECN_ECT_1 - 1; + const u8 ect0_idx = INET_ECN_ECT_0 - 1; + const u8 ce_idx = INET_ECN_CE - 1; unsigned long rate; u32 now; u64 rate64; @@ -4266,6 +4270,14 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) if (tp->rto_stamp) info->tcpi_total_rto_time += tcp_clock_ms() - tp->rto_stamp;
+ info->tcpi_received_ce = tp->received_ce; + info->tcpi_delivered_e1_bytes = tp->delivered_ecn_bytes[ect1_idx]; + info->tcpi_delivered_e0_bytes = tp->delivered_ecn_bytes[ect0_idx]; + info->tcpi_delivered_ce_bytes = tp->delivered_ecn_bytes[ce_idx]; + info->tcpi_received_e1_bytes = tp->received_ecn_bytes[ect1_idx]; + info->tcpi_received_e0_bytes = tp->received_ecn_bytes[ect0_idx]; + info->tcpi_received_ce_bytes = tp->received_ecn_bytes[ce_idx]; + unlock_sock_fast(sk, slow); } EXPORT_SYMBOL_GPL(tcp_get_info); @@ -5144,12 +5156,13 @@ static void __init tcp_struct_check(void) CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, rate_delivered); CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, rate_interval_us); CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, rcv_rtt_last_tsecr); + CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, delivered_ecn_bytes); CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, first_tx_mstamp); CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, delivered_mstamp); CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, bytes_acked); CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, rcv_rtt_est); CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_rx, rcvq_space); - CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_rx, 96); + CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_rx, 112); }
void __init tcp_init(void) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 3d4bc2770749..41798c7ecde2 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -70,6 +70,7 @@ #include <linux/sysctl.h> #include <linux/kernel.h> #include <linux/prefetch.h> +#include <linux/bitops.h> #include <net/dst.h> #include <net/tcp.h> #include <net/tcp_ecn.h> @@ -384,6 +385,73 @@ static void tcp_data_ecn_check(struct sock *sk, const struct sk_buff *skb) } }
+/* Returns true if the byte counters can be used */ +static bool tcp_accecn_process_option(struct tcp_sock *tp, + const struct sk_buff *skb, + u32 delivered_bytes, int flag) +{ + u8 estimate_ecnfield = tp->est_ecnfield; + bool ambiguous_ecn_bytes_incr = false; + bool first_changed = false; + unsigned int optlen; + bool order1, res; + unsigned int i; + u8 *ptr; + + if (!(flag & FLAG_SLOWPATH) || !tp->rx_opt.accecn) { + if (estimate_ecnfield) { + u8 ecnfield = estimate_ecnfield - 1; + + tp->delivered_ecn_bytes[ecnfield] += delivered_bytes; + return true; + } + return false; + } + + ptr = skb_transport_header(skb) + tp->rx_opt.accecn; + optlen = ptr[1] - 2; + if (WARN_ON_ONCE(ptr[0] != TCPOPT_ACCECN0 && ptr[0] != TCPOPT_ACCECN1)) + return false; + order1 = (ptr[0] == TCPOPT_ACCECN1); + ptr += 2; + + res = !!estimate_ecnfield; + for (i = 0; i < 3; i++) { + u32 init_offset; + u8 ecnfield; + s32 delta; + u32 *cnt; + + if (optlen < TCPOLEN_ACCECN_PERFIELD) + break; + + ecnfield = tcp_accecn_optfield_to_ecnfield(i, order1); + init_offset = tcp_accecn_field_init_offset(ecnfield); + cnt = &tp->delivered_ecn_bytes[ecnfield - 1]; + delta = tcp_update_ecn_bytes(cnt, ptr, init_offset); + if (delta && delta < 0) { + res = false; + ambiguous_ecn_bytes_incr = true; + } + if (delta && ecnfield != estimate_ecnfield) { + if (!first_changed) { + tp->est_ecnfield = ecnfield; + first_changed = true; + } else { + res = false; + ambiguous_ecn_bytes_incr = true; + } + } + + optlen -= TCPOLEN_ACCECN_PERFIELD; + ptr += TCPOLEN_ACCECN_PERFIELD; + } + if (ambiguous_ecn_bytes_incr) + tp->est_ecnfield = 0; + + return res; +} + static void tcp_count_delivered_ce(struct tcp_sock *tp, u32 ecn_count) { tp->delivered_ce += ecn_count; @@ -400,7 +468,8 @@ static void tcp_count_delivered(struct tcp_sock *tp, u32 delivered,
/* Returns the ECN CE delta */ static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb, - u32 delivered_pkts, int flag) + u32 delivered_pkts, u32 delivered_bytes, + int flag) { const struct tcphdr *th = tcp_hdr(skb); struct tcp_sock *tp = tcp_sk(sk); @@ -411,6 +480,8 @@ static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb, if (!(flag & (FLAG_FORWARD_PROGRESS | FLAG_TS_PROGRESS))) return 0;
+ tcp_accecn_process_option(tp, skb, delivered_bytes, flag); + if (!(flag & FLAG_SLOWPATH)) { /* AccECN counter might overflow on large ACKs */ if (delivered_pkts <= TCP_ACCECN_CEP_ACE_MASK) @@ -436,12 +507,14 @@ static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb, }
static u32 tcp_accecn_process(struct sock *sk, const struct sk_buff *skb, - u32 delivered_pkts, int *flag) + u32 delivered_pkts, u32 delivered_bytes, + int *flag) { struct tcp_sock *tp = tcp_sk(sk); u32 delta;
- delta = __tcp_accecn_process(sk, skb, delivered_pkts, *flag); + delta = __tcp_accecn_process(sk, skb, delivered_pkts, + delivered_bytes, *flag); if (delta > 0) { tcp_count_delivered_ce(tp, delta); *flag |= FLAG_ECE; @@ -3973,6 +4046,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) if (tcp_ecn_mode_accecn(tp)) ecn_count = tcp_accecn_process(sk, skb, tp->delivered - delivered, + sack_state.delivered_bytes, &flag);
tcp_in_ack_event(sk, flag); @@ -4012,6 +4086,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) if (tcp_ecn_mode_accecn(tp)) ecn_count = tcp_accecn_process(sk, skb, tp->delivered - delivered, + sack_state.delivered_bytes, &flag); tcp_in_ack_event(sk, flag); /* If data was DSACKed, see if we can undo a cwnd reduction. */ @@ -4139,6 +4214,7 @@ void tcp_parse_options(const struct net *net,
ptr = (const unsigned char *)(th + 1); opt_rx->saw_tstamp = 0; + opt_rx->accecn = 0; opt_rx->saw_unknown = 0;
while (length > 0) { @@ -4230,6 +4306,12 @@ void tcp_parse_options(const struct net *net, ptr, th->syn, foc, false); break;
+ case TCPOPT_ACCECN0: + case TCPOPT_ACCECN1: + /* Save offset of AccECN option in TCP header */ + opt_rx->accecn = (ptr - 2) - (__u8 *)th; + break; + case TCPOPT_EXP: /* Fast Open option shares code 254 using a * 16 bits magic number. @@ -4290,11 +4372,14 @@ static bool tcp_fast_parse_options(const struct net *net, */ if (th->doff == (sizeof(*th) / 4)) { tp->rx_opt.saw_tstamp = 0; + tp->rx_opt.accecn = 0; return false; } else if (tp->rx_opt.tstamp_ok && th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { - if (tcp_parse_aligned_timestamp(tp, th)) + if (tcp_parse_aligned_timestamp(tp, th)) { + tp->rx_opt.accecn = 0; return true; + } }
tcp_parse_options(net, skb, &tp->rx_opt, 1, NULL); @@ -6111,6 +6196,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb) */
tp->rx_opt.saw_tstamp = 0; + tp->rx_opt.accecn = 0;
/* pred_flags is 0xS?10 << 16 + snd_wnd * if header_prediction is to be made diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 99d1264d3d90..1629698ff91c 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -3586,6 +3586,7 @@ static void __net_init tcp_set_hashinfo(struct net *net) static int __net_init tcp_sk_init(struct net *net) { net->ipv4.sysctl_tcp_ecn = TCP_ECN_IN_ECN_OUT_NOECN; + net->ipv4.sysctl_tcp_ecn_option = TCP_ACCECN_OPTION_FULL; net->ipv4.sysctl_tcp_ecn_fallback = 1;
net->ipv4.sysctl_tcp_base_mss = TCP_BASE_MSS; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index d98a1a17eb52..bd59278062aa 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -385,6 +385,7 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp) #define OPTION_SMC BIT(9) #define OPTION_MPTCP BIT(10) #define OPTION_AO BIT(11) +#define OPTION_ACCECN BIT(12)
static void smc_options_write(__be32 *ptr, u16 *options) { @@ -406,6 +407,8 @@ struct tcp_out_options { u16 mss; /* 0 to disable */ u8 ws; /* window scale, 0 to disable */ u8 num_sack_blocks; /* number of SACK blocks to include */ + u8 num_accecn_fields:7, /* number of AccECN fields needed */ + use_synack_ecn_bytes:1; /* Use synack_ecn_bytes or not */ u8 hash_size; /* bytes in hash_location */ u8 bpf_opt_len; /* length of BPF hdr option */ __u8 *hash_location; /* temporary pointer, overloaded */ @@ -603,6 +606,11 @@ static __be32 *process_tcp_ao_options(struct tcp_sock *tp, return ptr; }
+/* Initial values for AccECN option, ordered is based on ECN field bits + * similar to received_ecn_bytes. Used for SYN/ACK AccECN option. + */ +static const u32 synack_ecn_bytes[3] = { 0, 0, 0 }; + /* Write previously computed TCP options to the packet. * * Beware: Something in the Internet is very sensitive to the ordering of @@ -621,6 +629,8 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, struct tcp_out_options *opts, struct tcp_key *key) { + u8 leftover_highbyte = TCPOPT_NOP; /* replace 1st NOP if avail */ + u8 leftover_lowbyte = TCPOPT_NOP; /* replace 2nd NOP in succession */ __be32 *ptr = (__be32 *)(th + 1); u16 options = opts->options; /* mungable copy */
@@ -656,15 +666,71 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, *ptr++ = htonl(opts->tsecr); }
+ if (OPTION_ACCECN & options) { + const u32 *ecn_bytes = opts->use_synack_ecn_bytes ? + synack_ecn_bytes : + tp->received_ecn_bytes; + const u8 ect0_idx = INET_ECN_ECT_0 - 1; + const u8 ect1_idx = INET_ECN_ECT_1 - 1; + const u8 ce_idx = INET_ECN_CE - 1; + u32 e0b; + u32 e1b; + u32 ceb; + u8 len; + + e0b = ecn_bytes[ect0_idx] + TCP_ACCECN_E0B_INIT_OFFSET; + e1b = ecn_bytes[ect1_idx] + TCP_ACCECN_E1B_INIT_OFFSET; + ceb = ecn_bytes[ce_idx] + TCP_ACCECN_CEB_INIT_OFFSET; + len = TCPOLEN_ACCECN_BASE + + opts->num_accecn_fields * TCPOLEN_ACCECN_PERFIELD; + + if (opts->num_accecn_fields == 2) { + *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) | + ((e1b >> 8) & 0xffff)); + *ptr++ = htonl(((e1b & 0xff) << 24) | + (ceb & 0xffffff)); + } else if (opts->num_accecn_fields == 1) { + *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) | + ((e1b >> 8) & 0xffff)); + leftover_highbyte = e1b & 0xff; + leftover_lowbyte = TCPOPT_NOP; + } else if (opts->num_accecn_fields == 0) { + leftover_highbyte = TCPOPT_ACCECN1; + leftover_lowbyte = len; + } else if (opts->num_accecn_fields == 3) { + *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) | + ((e1b >> 8) & 0xffff)); + *ptr++ = htonl(((e1b & 0xff) << 24) | + (ceb & 0xffffff)); + *ptr++ = htonl(((e0b & 0xffffff) << 8) | + TCPOPT_NOP); + } + if (tp) + tp->accecn_minlen = 0; + } + if (unlikely(OPTION_SACK_ADVERTISE & options)) { - *ptr++ = htonl((TCPOPT_NOP << 24) | - (TCPOPT_NOP << 16) | + *ptr++ = htonl((leftover_highbyte << 24) | + (leftover_lowbyte << 16) | (TCPOPT_SACK_PERM << 8) | TCPOLEN_SACK_PERM); + leftover_highbyte = TCPOPT_NOP; + leftover_lowbyte = TCPOPT_NOP; }
if (unlikely(OPTION_WSCALE & options)) { - *ptr++ = htonl((TCPOPT_NOP << 24) | + u8 highbyte = TCPOPT_NOP; + + /* Do not split the leftover 2-byte to fit into a single + * NOP, i.e., replace this NOP only when 1 byte is leftover + * within leftover_highbyte. + */ + if (unlikely(leftover_highbyte != TCPOPT_NOP && + leftover_lowbyte == TCPOPT_NOP)) { + highbyte = leftover_highbyte; + leftover_highbyte = TCPOPT_NOP; + } + *ptr++ = htonl((highbyte << 24) | (TCPOPT_WINDOW << 16) | (TCPOLEN_WINDOW << 8) | opts->ws); @@ -675,11 +741,13 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, tp->duplicate_sack : tp->selective_acks; int this_sack;
- *ptr++ = htonl((TCPOPT_NOP << 24) | - (TCPOPT_NOP << 16) | + *ptr++ = htonl((leftover_highbyte << 24) | + (leftover_lowbyte << 16) | (TCPOPT_SACK << 8) | (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK))); + leftover_highbyte = TCPOPT_NOP; + leftover_lowbyte = TCPOPT_NOP;
for (this_sack = 0; this_sack < opts->num_sack_blocks; ++this_sack) { @@ -688,6 +756,14 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, }
tp->rx_opt.dsack = 0; + } else if (unlikely(leftover_highbyte != TCPOPT_NOP || + leftover_lowbyte != TCPOPT_NOP)) { + *ptr++ = htonl((leftover_highbyte << 24) | + (leftover_lowbyte << 16) | + (TCPOPT_NOP << 8) | + TCPOPT_NOP); + leftover_highbyte = TCPOPT_NOP; + leftover_lowbyte = TCPOPT_NOP; }
if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) { @@ -768,6 +844,61 @@ static void mptcp_set_option_cond(const struct request_sock *req, } }
+static u32 tcp_synack_options_combine_saving(struct tcp_out_options *opts) +{ + /* How much there's room for combining with the alignment padding? */ + if ((opts->options & (OPTION_SACK_ADVERTISE | OPTION_TS)) == + OPTION_SACK_ADVERTISE) + return 2; + else if (opts->options & OPTION_WSCALE) + return 1; + return 0; +} + +/* Calculates how long AccECN option will fit to @remaining option space. + * + * AccECN option can sometimes replace NOPs used for alignment of other + * TCP options (up to @max_combine_saving available). + * + * Only solutions with at least @required AccECN fields are accepted. + * + * Returns: The size of the AccECN option excluding space repurposed from + * the alignment of the other options. + */ +static int tcp_options_fit_accecn(struct tcp_out_options *opts, int required, + int remaining) +{ + int size = TCP_ACCECN_MAXSIZE; + int max_combine_saving; + int align_size; + + if (opts->use_synack_ecn_bytes) + max_combine_saving = tcp_synack_options_combine_saving(opts); + else + max_combine_saving = opts->num_sack_blocks > 0 ? 2 : 0; + opts->num_accecn_fields = TCP_ACCECN_NUMFIELDS; + while (opts->num_accecn_fields >= required) { + /* Pad to dword if cannot combine */ + if ((size & 0x3) > max_combine_saving) + align_size = ALIGN(size, 4); + else + align_size = ALIGN_DOWN(size, 4); + + if (remaining >= align_size) { + size = align_size; + break; + } + + opts->num_accecn_fields--; + size -= TCPOLEN_ACCECN_PERFIELD; + } + if (opts->num_accecn_fields < required) + return 0; + + opts->options |= OPTION_ACCECN; + return size; +} + /* Compute TCP options for SYN packets. This is not the final * network wire format yet. */ @@ -850,6 +981,15 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, } }
+ /* Simultaneous open SYN/ACK needs AccECN option but not SYN */ + if (unlikely((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) && + tcp_ecn_mode_accecn(tp) && + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) && + remaining >= TCPOLEN_ACCECN_BASE)) { + opts->use_synack_ecn_bytes = 1; + remaining -= tcp_options_fit_accecn(opts, 0, remaining); + } + bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
return MAX_TCP_OPTION_SPACE - remaining; @@ -867,6 +1007,7 @@ static unsigned int tcp_synack_options(const struct sock *sk, { struct inet_request_sock *ireq = inet_rsk(req); unsigned int remaining = MAX_TCP_OPTION_SPACE; + struct tcp_request_sock *treq = tcp_rsk(req);
if (tcp_key_is_md5(key)) { opts->options |= OPTION_MD5; @@ -929,6 +1070,13 @@ static unsigned int tcp_synack_options(const struct sock *sk,
smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
+ if (treq->accecn_ok && + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) && + remaining >= TCPOLEN_ACCECN_BASE) { + opts->use_synack_ecn_bytes = 1; + remaining -= tcp_options_fit_accecn(opts, 0, remaining); + } + bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb, synack_type, opts, &remaining);
@@ -1001,6 +1149,13 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb opts->num_sack_blocks = 0; }
+ if (tcp_ecn_mode_accecn(tp) && + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option)) { + opts->use_synack_ecn_bytes = 0; + size += tcp_options_fit_accecn(opts, tp->accecn_minlen, + MAX_TCP_OPTION_SPACE - size); + } + if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) { unsigned int remaining = MAX_TCP_OPTION_SPACE - size;