From: Ilpo Järvinen ij@kernel.org
Accurate ECN negotiation parts based on the specification: https://tools.ietf.org/id/draft-ietf-tcpm-accurate-ecn-28.txt
Accurate ECN is negotiated using ECE, CWR and AE flags in the TCP header. TCP falls back into using RFC3168 ECN if one of the ends supports only RFC3168-style ECN.
The AccECN negotiation includes reflecting IP ECN field value seen in SYN and SYNACK back using the same bits as negotiation to allow responding to SYN CE marks and to detect ECN field mangling. CE marks should not occur currently because SYN=1 segments are sent with Non-ECT in IP ECN field (but proposal exists to remove this restriction).
Reflecting SYN IP ECN field in SYNACK is relatively simple. Reflecting SYNACK IP ECN field in the final/third ACK of the handshake is more challenging. Linux TCP code is not well prepared for using the final/third ACK a signalling channel which makes things somewhat complicated here.
tcp_ecn sysctl can be used to select the highest ECN variant (Accurate ECN, ECN, No ECN) that is attemped to be negotiated and requested for incoming connection and outgoing connection: TCP_ECN_IN_NOECN_OUT_NOECN, TCP_ECN_IN_ECN_OUT_ECN, TCP_ECN_IN_ECN_OUT_NOECN, TCP_ECN_IN_ACCECN_OUT_ACCECN, TCP_ECN_IN_ACCECN_OUT_ECN, and TCP_ECN_IN_ACCECN_OUT_NOECN.
After this patch, the size of tcp_request_sock remains unchanged and no new holes are added. Below are the pahole outcomes before and after this patch:
[BEFORE THIS PATCH] struct tcp_request_sock { [...] u32 rcv_nxt; /* 352 4 */ u8 syn_tos; /* 356 1 */
/* size: 360, cachelines: 6, members: 16 */ }
[AFTER THIS PATCH] struct tcp_request_sock { [...] u32 rcv_nxt; /* 352 4 */ u8 syn_tos; /* 356 1 */ bool accecn_ok; /* 357 1 */ u8 syn_ect_snt:2; /* 358: 0 1 */ u8 syn_ect_rcv:2; /* 358: 2 1 */ u8 accecn_fail_mode:4; /* 358: 4 1 */
/* size: 360, cachelines: 6, members: 20 */ }
After this patch, the size of tcp_sock remains unchanged and no new holes are added. Also, 4 bits of the existing 2-byte hole are exploited. Below are the pahole outcomes before and after this patch:
[BEFORE THIS PATCH] struct tcp_sock { [...] u8 dup_ack_counter:2; /* 2825: 0 1 */ u8 tlp_retrans:1; /* 2825: 2 1 */ u8 unused:5; /* 2825: 3 1 */ u8 thin_lto:1; /* 2826: 0 1 */ u8 fastopen_connect:1; /* 2826: 1 1 */ u8 fastopen_no_cookie:1; /* 2826: 2 1 */ u8 fastopen_client_fail:2; /* 2826: 3 1 */ u8 frto:1; /* 2826: 5 1 */ /* XXX 2 bits hole, try to pack */
[...] u8 keepalive_probes; /* 2829 1 */ /* XXX 2 bytes hole, try to pack */
[...] /* size: 3264, cachelines: 51, members: 166 */ }
[AFTER THIS PATCH] struct tcp_sock { [...] u8 dup_ack_counter:2; /* 2825: 0 1 */ u8 tlp_retrans:1; /* 2825: 2 1 */ u8 syn_ect_snt:2; /* 2825: 3 1 */ u8 syn_ect_rcv:2; /* 2825: 5 1 */ /* XXX 1 bit hole, try to pack */
u8 thin_lto:1; /* 2826: 0 1 */ u8 fastopen_connect:1; /* 2826: 1 1 */ u8 fastopen_no_cookie:1; /* 2826: 2 1 */ u8 fastopen_client_fail:2; /* 2826: 3 1 */ u8 frto:1; /* 2826: 5 1 */ /* XXX 2 bits hole, try to pack */
[...] u8 keepalive_probes; /* 2829 1 */ u8 accecn_fail_mode:4; /* 2830: 0 1 */ /* XXX 4 bits hole, try to pack */ /* XXX 1 byte hole, try to pack */
[...] /* size: 3264, cachelines: 51, members: 168 */ }
Signed-off-by: Ilpo Järvinen ij@kernel.org Co-developed-by: Olivier Tilmans olivier.tilmans@nokia.com Signed-off-by: Olivier Tilmans olivier.tilmans@nokia.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
--- v10 - Add documentation of tcp_ecn in ip-sysctl.rst to this patch - Move wait third ACK functionality into a later patch - Add comments on the AccECN helper functions in tcp_ecn.h
--- --- Documentation/networking/ip-sysctl.rst | 36 +- .../networking/net_cachelines/tcp_sock.rst | 3 + include/linux/tcp.h | 8 +- include/net/tcp.h | 1 + include/net/tcp_ecn.h | 327 ++++++++++++++++-- net/ipv4/syncookies.c | 3 + net/ipv4/sysctl_net_ipv4.c | 3 +- net/ipv4/tcp.c | 1 + net/ipv4/tcp_input.c | 50 ++- net/ipv4/tcp_ipv4.c | 6 +- net/ipv4/tcp_minisocks.c | 24 +- net/ipv4/tcp_output.c | 10 +- net/ipv6/syncookies.c | 1 + net/ipv6/tcp_ipv6.c | 1 + 14 files changed, 415 insertions(+), 59 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 9af5a8935d57..ebd391a1a3af 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -443,20 +443,28 @@ tcp_early_retrans - INTEGER
tcp_ecn - INTEGER Control use of Explicit Congestion Notification (ECN) by TCP. - ECN is used only when both ends of the TCP connection indicate - support for it. This feature is useful in avoiding losses due - to congestion by allowing supporting routers to signal - congestion before having to drop packets. - - Possible values are: - - = ===================================================== - 0 Disable ECN. Neither initiate nor accept ECN. - 1 Enable ECN when requested by incoming connections and - also request ECN on outgoing connection attempts. - 2 Enable ECN when requested by incoming connections - but do not request ECN on outgoing connections. - = ===================================================== + ECN is used only when both ends of the TCP connection indicate support + for it. This feature is useful in avoiding losses due to congestion by + allowing supporting routers to signal congestion before having to drop + packets. A host that supports ECN both sends ECN at the IP layer and + feeds back ECN at the TCP layer. The highest variant of ECN feedback + that both peers support is chosen by the ECN negotiation (Accurate ECN, + ECN, or no ECN). + + The highest negotiated variant for incoming connection requests + and the highest variant requested by outgoing connection + attempts: + + ===== ==================== ==================== + Value Incoming connections Outgoing connections + ===== ==================== ==================== + 0 No ECN No ECN + 1 ECN ECN + 2 ECN No ECN + 3 AccECN AccECN + 4 AccECN ECN + 5 AccECN No ECN + ===== ==================== ====================
Default: 2
diff --git a/Documentation/networking/net_cachelines/tcp_sock.rst b/Documentation/networking/net_cachelines/tcp_sock.rst index 31313a9adccc..4f71ece7c655 100644 --- a/Documentation/networking/net_cachelines/tcp_sock.rst +++ b/Documentation/networking/net_cachelines/tcp_sock.rst @@ -103,6 +103,9 @@ u32 delivered read_mostly read_w u32 delivered_ce read_mostly read_write tcp_rate_skb_sent(tx);tcp_rate_gen(rx) u32 received_ce read_mostly read_write u8:4 received_ce_pending read_mostly read_write +u8:2 syn_ect_snt write_mostly read_write +u8:2 syn_ect_rcv read_mostly 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) u64 first_tx_mstamp read_write tcp_rate_skb_sent diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 874e0e45dfad..994a6e7256e1 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -168,6 +168,10 @@ struct tcp_request_sock { * after data-in-SYN. */ u8 syn_tos; + bool accecn_ok; + u8 syn_ect_snt: 2, + syn_ect_rcv: 2, + accecn_fail_mode:4; #ifdef CONFIG_TCP_AO u8 ao_keyid; u8 ao_rcv_next; @@ -375,7 +379,8 @@ struct tcp_sock { u8 compressed_ack; u8 dup_ack_counter:2, tlp_retrans:1, /* TLP is a retransmission */ - unused:5; + syn_ect_snt:2, /* AccECN ECT memory, only */ + syn_ect_rcv:2; /* ... needed durign 3WHS + first seqno */ u8 thin_lto : 1,/* Use linear timeouts for thin streams */ fastopen_connect:1, /* FASTOPEN_CONNECT sockopt */ fastopen_no_cookie:1, /* Allow send/recv SYN+data without a cookie */ @@ -391,6 +396,7 @@ struct tcp_sock { syn_fastopen_child:1; /* created TFO passive child socket */
u8 keepalive_probes; /* num of allowed keep alive probes */ + u8 accecn_fail_mode:4; /* AccECN failure handling */ u32 tcp_tx_delay; /* delay (in usec) added to TX packets */
/* RTT measurement */ diff --git a/include/net/tcp.h b/include/net/tcp.h index 30b04cd8df60..61b103633da4 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -962,6 +962,7 @@ static inline u32 tcp_rsk_tsval(const struct tcp_request_sock *treq)
#define TCPHDR_ACE (TCPHDR_ECE | TCPHDR_CWR | TCPHDR_AE) #define TCPHDR_SYN_ECN (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR) +#define TCPHDR_SYNACK_ACCECN (TCPHDR_SYN | TCPHDR_ACK | TCPHDR_CWR)
#define TCP_ACCECN_CEP_ACE_MASK 0x7 #define TCP_ACCECN_ACE_MAX_DELTA 6 diff --git a/include/net/tcp_ecn.h b/include/net/tcp_ecn.h index b0ed89dbad41..7ac68cb70ef3 100644 --- a/include/net/tcp_ecn.h +++ b/include/net/tcp_ecn.h @@ -4,12 +4,26 @@
#include <linux/tcp.h> #include <linux/skbuff.h> +#include <linux/bitfield.h>
#include <net/inet_connection_sock.h> #include <net/sock.h> #include <net/tcp.h> #include <net/inet_ecn.h>
+/* The highest ECN variant (Accurate ECN, ECN, or no ECN) that is + * attemped to be negotiated and requested for incoming connection + * and outgoing connection, respectively. + */ +enum tcp_ecn_mode { + TCP_ECN_IN_NOECN_OUT_NOECN = 0, + TCP_ECN_IN_ECN_OUT_ECN = 1, + TCP_ECN_IN_ECN_OUT_NOECN = 2, + TCP_ECN_IN_ACCECN_OUT_ACCECN = 3, + TCP_ECN_IN_ACCECN_OUT_ECN = 4, + TCP_ECN_IN_ACCECN_OUT_NOECN = 5, +}; + static inline void tcp_ecn_queue_cwr(struct tcp_sock *tp) { /* Do not set CWR if in AccECN mode! */ @@ -39,19 +53,130 @@ static inline void tcp_ecn_withdraw_cwr(struct tcp_sock *tp) tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; }
+/* tp->accecn_fail_mode */ +#define TCP_ACCECN_ACE_FAIL_SEND BIT(0) +#define TCP_ACCECN_ACE_FAIL_RECV BIT(1) +#define TCP_ACCECN_OPT_FAIL_SEND BIT(2) +#define TCP_ACCECN_OPT_FAIL_RECV BIT(3) + +static inline bool tcp_accecn_ace_fail_send(const struct tcp_sock *tp) +{ + return tp->accecn_fail_mode & TCP_ACCECN_ACE_FAIL_SEND; +} + +static inline bool tcp_accecn_ace_fail_recv(const struct tcp_sock *tp) +{ + return tp->accecn_fail_mode & TCP_ACCECN_ACE_FAIL_RECV; +} + +static inline bool tcp_accecn_opt_fail_send(const struct tcp_sock *tp) +{ + return tp->accecn_fail_mode & TCP_ACCECN_OPT_FAIL_SEND; +} + +static inline bool tcp_accecn_opt_fail_recv(const struct tcp_sock *tp) +{ + return tp->accecn_fail_mode & TCP_ACCECN_OPT_FAIL_RECV; +} + +static inline void tcp_accecn_fail_mode_set(struct tcp_sock *tp, u8 mode) +{ + tp->accecn_fail_mode |= mode; +} + static inline u8 tcp_accecn_ace(const struct tcphdr *th) { return (th->ae << 2) | (th->cwr << 1) | th->ece; }
-static inline void tcp_accecn_init_counters(struct tcp_sock *tp) +/* Infer the ECT value our SYN arrived with from the echoed ACE field */ +static inline int tcp_accecn_extract_syn_ect(u8 ace) { - tp->received_ce = 0; - tp->received_ce_pending = 0; + /* Below is an excerpt from Tables 2 of the AccECN spec: + * +================================+========================+ + * | Echoed ACE field | Received ECT values of | + * | AE CWR ECE | our SYN arrived with | + * +================================+========================+ + * | 0 1 0 | Not-ECT | + * | 0 1 1 | ECT(1) | + * | 1 0 0 | ECT(0) | + * | 1 1 0 | CE | + * +================================+========================+ + */ + if (ace & 0x1) + return INET_ECN_ECT_1; + if (!(ace & 0x2)) + return INET_ECN_ECT_0; + if (ace & 0x4) + return INET_ECN_CE; + return INET_ECN_NOT_ECT; +} + +/* Check ECN field transition to detect invalid transitions */ +static inline bool tcp_ect_transition_valid(u8 snt, u8 rcv) +{ + if (rcv == snt) + return true; + + /* Non-ECT altered to something or something became non-ECT */ + if (snt == INET_ECN_NOT_ECT || rcv == INET_ECN_NOT_ECT) + return false; + /* CE -> ECT(0/1)? */ + if (snt == INET_ECN_CE) + return false; + return true; +} + +static inline bool tcp_accecn_validate_syn_feedback(struct sock *sk, u8 ace, + u8 sent_ect) +{ + u8 ect = tcp_accecn_extract_syn_ect(ace); + struct tcp_sock *tp = tcp_sk(sk); + + if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)) + return true; + + if (!tcp_ect_transition_valid(sent_ect, ect)) { + tcp_accecn_fail_mode_set(tp, TCP_ACCECN_ACE_FAIL_RECV); + return false; + } + + return true; +} + +/* Validate the 3rd ACK based on the ACE field, see Table 4 of AccECN spec */ +static inline void tcp_accecn_third_ack(struct sock *sk, + const struct sk_buff *skb, u8 sent_ect) +{ + u8 ace = tcp_accecn_ace(tcp_hdr(skb)); + struct tcp_sock *tp = tcp_sk(sk); + + switch (ace) { + case 0x0: + /* Invalid value */ + tcp_accecn_fail_mode_set(tp, TCP_ACCECN_ACE_FAIL_RECV); + break; + case 0x7: + case 0x5: + case 0x1: + /* Unused but legal values */ + break; + default: + /* Validation only applies to first non-data packet */ + if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq && + !TCP_SKB_CB(skb)->sacked && + tcp_accecn_validate_syn_feedback(sk, ace, sent_ect)) { + if ((tcp_accecn_extract_syn_ect(ace) == INET_ECN_CE) && + !tp->delivered_ce) + tp->delivered_ce++; + } + break; + } }
/* 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) +static inline void tcp_ecn_received_counters(struct sock *sk, + const struct sk_buff *skb) { u8 ecnfield = TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK; u8 is_ce = INET_ECN_is_ce(ecnfield); @@ -74,27 +199,157 @@ static inline void tcp_ecn_received_counters(struct sock *sk, const struct sk_bu } }
-static inline void tcp_accecn_set_ace(struct tcphdr *th, struct tcp_sock *tp) +/* AccECN specification, 5.1: [...] a server can determine that it + * negotiated AccECN as [...] if the ACK contains an ACE field with + * the value 0b010 to 0b111 (decimal 2 to 7). + */ +static inline bool cookie_accecn_ok(const struct tcphdr *th) { - u32 wire_ace; + return tcp_accecn_ace(th) > 0x1; +} + +/* Used to form the ACE flags for SYN/ACK */ +static inline u16 tcp_accecn_reflector_flags(u8 ect) +{ + /* TCP ACE flags of SYN/ACK are set based on IP-ECN codepoint received + * from SYN. Below is an excerpt from Table 2 of the AccECN spec: + * +====================+====================================+ + * | IP-ECN codepoint | Respective ACE falgs on SYN/ACK | + * | received on SYN | AE CWR ECE | + * +====================+====================================+ + * | Not-ECT | 0 1 0 | + * | ECT(1) | 0 1 1 | + * | ECT(0) | 1 0 0 | + * | CE | 1 1 0 | + * +====================+====================================+ + */ + u32 flags = ect + 2; + + if (ect == 3) + flags++; + return FIELD_PREP(TCPHDR_ACE, flags); +}
- wire_ace = tp->received_ce + TCP_ACCECN_CEP_INIT_OFFSET; - th->ece = !!(wire_ace & 0x1); - th->cwr = !!(wire_ace & 0x2); - th->ae = !!(wire_ace & 0x4); +/* AccECN specificaiton, 3.1.2: If a TCP server that implements AccECN + * receives a SYN with the three TCP header flags (AE, CWR and ECE) set + * to any combination other than 000, 011 or 111, it MUST negotiate the + * use of AccECN as if they had been set to 111. + */ +static inline bool tcp_accecn_syn_requested(const struct tcphdr *th) +{ + u8 ace = tcp_accecn_ace(th); + + return ace && ace != 0x3; +} + +static inline void tcp_accecn_init_counters(struct tcp_sock *tp) +{ + tp->received_ce = 0; tp->received_ce_pending = 0; }
-static inline void tcp_ecn_rcv_synack(struct tcp_sock *tp, - const struct tcphdr *th) +/* Used for make_synack to form the ACE flags */ +static inline void tcp_accecn_echo_syn_ect(struct tcphdr *th, u8 ect) +{ + /* TCP ACE flags of SYN/ACK are set based on IP-ECN codepoint received + * from SYN. Below is an excerpt from Table 2 of the AccECN spec: + * +====================+====================================+ + * | IP-ECN codepoint | Respective ACE falgs on SYN/ACK | + * | received on SYN | AE CWR ECE | + * +====================+====================================+ + * | Not-ECT | 0 1 0 | + * | ECT(1) | 0 1 1 | + * | ECT(0) | 1 0 0 | + * | CE | 1 1 0 | + * +====================+====================================+ + */ + th->ae = !!(ect & INET_ECN_ECT_0); + th->cwr = ect != INET_ECN_ECT_0; + th->ece = ect == INET_ECN_ECT_1; +} + +static inline void tcp_accecn_set_ace(struct tcp_sock *tp, struct sk_buff *skb, + struct tcphdr *th) { - if (tcp_ecn_mode_rfc3168(tp) && (!th->ece || th->cwr)) + u32 wire_ace; + + /* The final packet of the 3WHS or anything like it must reflect + * the SYN/ACK ECT instead of putting CEP into ACE field, such + * case show up in tcp_flags. + */ + if (likely(!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACE))) { + wire_ace = tp->received_ce + TCP_ACCECN_CEP_INIT_OFFSET; + th->ece = !!(wire_ace & 0x1); + th->cwr = !!(wire_ace & 0x2); + th->ae = !!(wire_ace & 0x4); + tp->received_ce_pending = 0; + } +} + +/* See Table 2 of the AccECN draft */ +static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct tcphdr *th, + u8 ip_dsfield) +{ + struct tcp_sock *tp = tcp_sk(sk); + u8 ace = tcp_accecn_ace(th); + + switch (ace) { + case 0x0: + case 0x7: + /* +========+========+============+=============+ + * | A | B | SYN/ACK | Feedback | + * | | | B->A | Mode of A | + * | | | AE CWR ECE | | + * +========+========+============+=============+ + * | AccECN | No ECN | 0 0 0 | Not ECN | + * | AccECN | Broken | 1 1 1 | Not ECN | + * +========+========+============+=============+ + */ tcp_ecn_mode_set(tp, TCP_ECN_DISABLED); + break; + case 0x1: + case 0x5: + /* +========+========+============+=============+ + * | A | B | SYN/ACK | Feedback | + * | | | B->A | Mode of A | + * | | | AE CWR ECE | | + * +========+========+============+=============+ + * | AccECN | Nonce | 1 0 1 | (Reserved) | + * | AccECN | ECN | 0 0 1 | Classic ECN | + * | Nonce | AccECN | 0 0 1 | Classic ECN | + * | ECN | AccECN | 0 0 1 | Classic ECN | + * +========+========+============+=============+ + */ + if (tcp_ecn_mode_pending(tp)) + /* Downgrade from AccECN, or requested initially */ + tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); + break; + default: + tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN); + tp->syn_ect_rcv = ip_dsfield & INET_ECN_MASK; + if (INET_ECN_is_ce(ip_dsfield) && + tcp_accecn_validate_syn_feedback(sk, ace, + tp->syn_ect_snt)) { + tp->received_ce++; + tp->received_ce_pending++; + } + break; + } }
-static inline void tcp_ecn_rcv_syn(struct tcp_sock *tp, - const struct tcphdr *th) +static inline void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th, + const struct sk_buff *skb) { + if (tcp_ecn_mode_pending(tp)) { + if (!tcp_accecn_syn_requested(th)) { + /* Downgrade to classic ECN feedback */ + tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); + } else { + tp->syn_ect_rcv = TCP_SKB_CB(skb)->ip_dsfield & + INET_ECN_MASK; + tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN); + } + } if (tcp_ecn_mode_rfc3168(tp) && (!th->ece || !th->cwr)) tcp_ecn_mode_set(tp, TCP_ECN_DISABLED); } @@ -110,7 +365,7 @@ static inline bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, /* Packet ECN state for a SYN-ACK */ static inline void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb) { - const struct tcp_sock *tp = tcp_sk(sk); + struct tcp_sock *tp = tcp_sk(sk);
TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR; if (tcp_ecn_disabled(tp)) @@ -118,6 +373,13 @@ static inline void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb) else if (tcp_ca_needs_ecn(sk) || tcp_bpf_ca_needs_ecn(sk)) INET_ECN_xmit(sk); + + if (tp->ecn_flags & TCP_ECN_MODE_ACCECN) { + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ACE; + TCP_SKB_CB(skb)->tcp_flags |= + tcp_accecn_reflector_flags(tp->syn_ect_rcv); + tp->syn_ect_snt = inet_sk(sk)->tos & INET_ECN_MASK; + } }
/* Packet ECN state for a SYN. */ @@ -125,8 +387,20 @@ static inline void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk); - bool use_ecn = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn) == 1 || - tcp_ca_needs_ecn(sk) || bpf_needs_ecn; + bool use_ecn, use_accecn; + u8 tcp_ecn = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn); + + /* +================+===========================+ + * | tcp_ecn values | Outgoing connections | + * +================+===========================+ + * | 0,2,5 | Do not request ECN | + * | 1,4 | Request ECN connection | + * | 3 | Request AccECN connection | + * +================+===========================+ + */ + use_accecn = tcp_ecn == 3; + use_ecn = tcp_ecn == 1 || tcp_ecn == 4 || + tcp_ca_needs_ecn(sk) || bpf_needs_ecn || use_accecn;
if (!use_ecn) { const struct dst_entry *dst = __sk_dst_get(sk); @@ -142,23 +416,32 @@ static inline void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) INET_ECN_xmit(sk);
TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR; - tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); + if (use_accecn) { + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_AE; + tcp_ecn_mode_set(tp, TCP_ECN_MODE_PENDING); + tp->syn_ect_snt = inet_sk(sk)->tos & INET_ECN_MASK; + } else { + tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); + } } }
static inline void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb) { - if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)) + if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)) { /* tp->ecn_flags are cleared at a later point in time when * SYN ACK is ultimatively being received. */ - TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR); + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ACE; + } }
static inline void tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th) { - if (inet_rsk(req)->ecn_ok) + if (tcp_rsk(req)->accecn_ok) + tcp_accecn_echo_syn_ect(th, tcp_rsk(req)->syn_ect_rcv); + else if (inet_rsk(req)->ecn_ok) th->ece = 1; }
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index eb0819463fae..e0c1e951c53c 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -403,6 +403,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) struct tcp_sock *tp = tcp_sk(sk); struct inet_request_sock *ireq; struct net *net = sock_net(sk); + struct tcp_request_sock *treq; struct request_sock *req; struct sock *ret = sk; struct flowi4 fl4; @@ -428,6 +429,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) }
ireq = inet_rsk(req); + treq = tcp_rsk(req);
sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr); sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr); @@ -483,6 +485,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) if (!req->syncookie) ireq->rcv_wscale = rcv_wscale; ireq->ecn_ok &= cookie_ecn_ok(net, &rt->dst); + treq->accecn_ok = ireq->ecn_ok && cookie_accecn_ok(th);
ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst); /* ip_queue_xmit() depends on our flow being setup diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 3a43010d726f..75ec1a599b52 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -47,6 +47,7 @@ static unsigned int udp_child_hash_entries_max = UDP_HTABLE_SIZE_MAX; static int tcp_plb_max_rounds = 31; static int tcp_plb_max_cong_thresh = 256; static unsigned int tcp_tw_reuse_delay_max = TCP_PAWS_MSL * MSEC_PER_SEC; +static int tcp_ecn_mode_max = 5;
/* obsolete */ static int sysctl_tcp_low_latency __read_mostly; @@ -728,7 +729,7 @@ static struct ctl_table ipv4_net_table[] = { .mode = 0644, .proc_handler = proc_dou8vec_minmax, .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_TWO, + .extra2 = &tcp_ecn_mode_max, }, { .procname = "tcp_ecn_fallback", diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index c5e128d6ecc7..45c85c788def 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3391,6 +3391,7 @@ int tcp_disconnect(struct sock *sk, int flags) tp->window_clamp = 0; tp->delivered = 0; tp->delivered_ce = 0; + tp->accecn_fail_mode = 0; tcp_accecn_init_counters(tp); if (icsk->icsk_ca_initialized && icsk->icsk_ca_ops->release) icsk->icsk_ca_ops->release(sk); diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 56c8514ee139..ea5d47354978 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3665,8 +3665,18 @@ bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb, return __tcp_oow_rate_limited(net, mib_idx, last_oow_ack_time); }
+static void tcp_send_ack_reflect_ect(struct sock *sk, bool accecn_reflector) +{ + struct tcp_sock *tp = tcp_sk(sk); + u16 flags = 0; + + if (accecn_reflector) + flags = tcp_accecn_reflector_flags(tp->syn_ect_rcv); + __tcp_send_ack(sk, tp->rcv_nxt, flags); +} + /* RFC 5961 7 [ACK Throttling] */ -static void tcp_send_challenge_ack(struct sock *sk) +static void tcp_send_challenge_ack(struct sock *sk, bool accecn_reflector) { struct tcp_sock *tp = tcp_sk(sk); struct net *net = sock_net(sk); @@ -3696,7 +3706,7 @@ static void tcp_send_challenge_ack(struct sock *sk) WRITE_ONCE(net->ipv4.tcp_challenge_count, count - 1); send_ack: NET_INC_STATS(net, LINUX_MIB_TCPCHALLENGEACK); - tcp_send_ack(sk); + tcp_send_ack_reflect_ect(sk, accecn_reflector); } }
@@ -3863,7 +3873,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */ if (before(ack, prior_snd_una - max_window)) { if (!(flag & FLAG_NO_CHALLENGE_ACK)) - tcp_send_challenge_ack(sk); + tcp_send_challenge_ack(sk, false); return -SKB_DROP_REASON_TCP_TOO_OLD_ACK; } goto old_ack; @@ -5882,6 +5892,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th, int syn_inerr) { struct tcp_sock *tp = tcp_sk(sk); + bool accecn_reflector = false; SKB_DR(reason);
/* RFC1323: H1. Apply PAWS check first. */ @@ -5974,7 +5985,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, if (tp->syn_fastopen && !tp->data_segs_in && sk->sk_state == TCP_ESTABLISHED) tcp_fastopen_active_disable(sk); - tcp_send_challenge_ack(sk); + tcp_send_challenge_ack(sk, false); SKB_DR_SET(reason, TCP_RESET); goto discard; } @@ -5985,6 +5996,8 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, * RFC 5961 4.2 : Send a challenge ack */ if (th->syn) { + if (tcp_ecn_mode_accecn(tp)) + accecn_reflector = true; if (sk->sk_state == TCP_SYN_RECV && sk->sk_socket && th->ack && TCP_SKB_CB(skb)->seq + 1 == TCP_SKB_CB(skb)->end_seq && TCP_SKB_CB(skb)->seq + 1 == tp->rcv_nxt && @@ -5994,7 +6007,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, if (syn_inerr) TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE); - tcp_send_challenge_ack(sk); + tcp_send_challenge_ack(sk, accecn_reflector); SKB_DR_SET(reason, TCP_INVALID_SYN); goto discard; } @@ -6459,7 +6472,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, * state to ESTABLISHED..." */
- tcp_ecn_rcv_synack(tp, th); + if (tcp_ecn_mode_any(tp)) + tcp_ecn_rcv_synack(sk, th, TCP_SKB_CB(skb)->ip_dsfield);
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); tcp_try_undo_spurious_syn(sk); @@ -6531,7 +6545,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, TCP_DELACK_MAX, false); goto consume; } - tcp_send_ack(sk); + tcp_send_ack_reflect_ect(sk, tcp_ecn_mode_accecn(tp)); return -1; }
@@ -6590,7 +6604,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, tp->snd_wl1 = TCP_SKB_CB(skb)->seq; tp->max_window = tp->snd_wnd;
- tcp_ecn_rcv_syn(tp, th); + tcp_ecn_rcv_syn(tp, th, skb);
tcp_mtup_init(sk); tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); @@ -6772,7 +6786,7 @@ tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) } /* accept old ack during closing */ if ((int)reason < 0) { - tcp_send_challenge_ack(sk); + tcp_send_challenge_ack(sk, false); reason = -reason; goto discard; } @@ -6819,9 +6833,12 @@ tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) tp->lsndtime = tcp_jiffies32;
tcp_initialize_rcv_mss(sk); + if (tcp_ecn_mode_accecn(tp)) + tcp_accecn_third_ack(sk, skb, tp->syn_ect_snt); tcp_fast_path_on(tp); if (sk->sk_shutdown & SEND_SHUTDOWN) tcp_shutdown(sk, SEND_SHUTDOWN); + break;
case TCP_FIN_WAIT1: { @@ -6991,6 +7008,15 @@ static void tcp_ecn_create_request(struct request_sock *req, bool ect, ecn_ok; u32 ecn_ok_dst;
+ if (tcp_accecn_syn_requested(th) && + READ_ONCE(net->ipv4.sysctl_tcp_ecn) >= 3) { + inet_rsk(req)->ecn_ok = 1; + tcp_rsk(req)->accecn_ok = 1; + tcp_rsk(req)->syn_ect_rcv = TCP_SKB_CB(skb)->ip_dsfield & + INET_ECN_MASK; + return; + } + if (!th_ecn) return;
@@ -6998,7 +7024,8 @@ static void tcp_ecn_create_request(struct request_sock *req, ecn_ok_dst = dst_feature(dst, DST_FEATURE_ECN_MASK); ecn_ok = READ_ONCE(net->ipv4.sysctl_tcp_ecn) || ecn_ok_dst;
- if (((!ect || th->res1) && ecn_ok) || tcp_ca_needs_ecn(listen_sk) || + if (((!ect || th->res1 || th->ae) && ecn_ok) || + tcp_ca_needs_ecn(listen_sk) || (ecn_ok_dst & DST_FEATURE_ECN_CA) || tcp_bpf_ca_needs_ecn((struct sock *)req)) inet_rsk(req)->ecn_ok = 1; @@ -7016,6 +7043,9 @@ static void tcp_openreq_init(struct request_sock *req, tcp_rsk(req)->snt_synack = 0; tcp_rsk(req)->snt_tsval_first = 0; tcp_rsk(req)->last_oow_ack_time = 0; + tcp_rsk(req)->accecn_ok = 0; + tcp_rsk(req)->syn_ect_rcv = 0; + tcp_rsk(req)->syn_ect_snt = 0; req->mss = rx_opt->mss_clamp; req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0; ireq->tstamp_ok = rx_opt->tstamp_ok; diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a847d894ace3..b95e4ed227cb 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -64,6 +64,7 @@ #include <net/icmp.h> #include <net/inet_hashtables.h> #include <net/tcp.h> +#include <net/tcp_ecn.h> #include <net/transp_v6.h> #include <net/ipv6.h> #include <net/inet_common.h> @@ -1190,7 +1191,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst, enum tcp_synack_type synack_type, struct sk_buff *syn_skb) { - const struct inet_request_sock *ireq = inet_rsk(req); + struct inet_request_sock *ireq = inet_rsk(req); struct flowi4 fl4; int err = -1; struct sk_buff *skb; @@ -1203,6 +1204,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst, skb = tcp_make_synack(sk, dst, req, foc, synack_type, syn_skb);
if (skb) { + tcp_rsk(req)->syn_ect_snt = inet_sk(sk)->tos & INET_ECN_MASK; __tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
tos = READ_ONCE(inet_sk(sk)->tos); @@ -3448,7 +3450,7 @@ 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 = 2; + net->ipv4.sysctl_tcp_ecn = TCP_ECN_IN_ECN_OUT_NOECN; net->ipv4.sysctl_tcp_ecn_fallback = 1;
net->ipv4.sysctl_tcp_base_mss = TCP_BASE_MSS; diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 2994c9222c9c..845b1c81b3b0 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -20,6 +20,7 @@ */
#include <net/tcp.h> +#include <net/tcp_ecn.h> #include <net/xfrm.h> #include <net/busy_poll.h> #include <net/rstreason.h> @@ -461,12 +462,23 @@ void tcp_openreq_init_rwin(struct request_sock *req, ireq->rcv_wscale = rcv_wscale; }
-static void tcp_ecn_openreq_child(struct tcp_sock *tp, - const struct request_sock *req) +static void tcp_ecn_openreq_child(struct sock *sk, + const struct request_sock *req, + const struct sk_buff *skb) { - tcp_ecn_mode_set(tp, inet_rsk(req)->ecn_ok ? - TCP_ECN_MODE_RFC3168 : - TCP_ECN_DISABLED); + const struct tcp_request_sock *treq = tcp_rsk(req); + struct tcp_sock *tp = tcp_sk(sk); + + if (treq->accecn_ok) { + tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN); + tp->syn_ect_snt = treq->syn_ect_snt; + tcp_accecn_third_ack(sk, skb, treq->syn_ect_snt); + tcp_ecn_received_counters(sk, skb); + } else { + tcp_ecn_mode_set(tp, inet_rsk(req)->ecn_ok ? + TCP_ECN_MODE_RFC3168 : + TCP_ECN_DISABLED); + } }
void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst) @@ -631,7 +643,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk, if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len) newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len; newtp->rx_opt.mss_clamp = req->mss; - tcp_ecn_openreq_child(newtp, req); + tcp_ecn_openreq_child(newsk, req, skb); newtp->fastopen_req = NULL; RCU_INIT_POINTER(newtp->fastopen_rsk, NULL);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 78018870a389..debcb1d431e6 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -332,8 +332,9 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb, return;
if (tcp_ecn_mode_accecn(tp)) { - INET_ECN_xmit(sk); - tcp_accecn_set_ace(th, tp); + if (!tcp_accecn_ace_fail_recv(tp)) + INET_ECN_xmit(sk); + tcp_accecn_set_ace(tp, skb, th); skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ACCECN; } else { /* Not-retransmitted data segment: set ECT and inject CWR. */ @@ -3343,7 +3344,10 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) tcp_retrans_try_collapse(sk, skb, avail_wnd); }
- /* RFC3168, section 6.1.1.1. ECN fallback */ + /* RFC3168, section 6.1.1.1. ECN fallback + * As AccECN uses the same SYN flags (+ AE), this check covers both + * cases. + */ if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN) tcp_ecn_clear_syn(sk, skb);
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c index f0ee1a909771..f0b87a3268ae 100644 --- a/net/ipv6/syncookies.c +++ b/net/ipv6/syncookies.c @@ -264,6 +264,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb) if (!req->syncookie) ireq->rcv_wscale = rcv_wscale; ireq->ecn_ok &= cookie_ecn_ok(net, dst); + tcp_rsk(req)->accecn_ok = ireq->ecn_ok && cookie_accecn_ok(th);
ret = tcp_get_cookie_sock(sk, skb, req, dst); if (!ret) { diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 8f2c3cba1f1f..1356fbc87fa2 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -545,6 +545,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst, skb = tcp_make_synack(sk, dst, req, foc, synack_type, syn_skb);
if (skb) { + tcp_rsk(req)->syn_ect_snt = np->tclass & INET_ECN_MASK; __tcp_v6_send_check(skb, &ireq->ir_v6_loc_addr, &ireq->ir_v6_rmt_addr);