From: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
AccECN option may fail in various way, handle these: - Attempt to negotiate the use of AccECN on the 1st retransmitted SYN - From the 2nd retransmitted SYN, stop AccECN negotiation - Remove option from SYN/ACK rexmits to handle blackholes - If no option arrives in SYN/ACK, assume Option is not usable - If an option arrives later, re-enabled - If option is zeroed, disable AccECN option processing
This patch use existing padding bits in tcp_request_sock and holes in tcp_sock without increasing the size.
Signed-off-by: Ilpo Järvinen ij@kernel.org Signed-off-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
--- v13: - Return TCP_ACCECN_OPT_FAIL_SEEN if WARN_ON_ONCE() is true in tcp_accecn_option_init()
v9: - Add comments about the 1st retx SYN still attempt AccECN negotiation
v8: - Add new helper function tcp_accecn_saw_opt_fail_recv() --- include/linux/tcp.h | 4 +++- include/net/tcp_ecn.h | 51 +++++++++++++++++++++++++++++++++++++--- net/ipv4/tcp.c | 1 + net/ipv4/tcp_input.c | 35 +++++++++++++++++++++++++-- net/ipv4/tcp_minisocks.c | 14 +++++++++++ net/ipv4/tcp_output.c | 11 ++++++--- 6 files changed, 107 insertions(+), 9 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index f637b659b35a..3ca5ed02de6d 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -173,6 +173,7 @@ struct tcp_request_sock { u8 syn_ect_snt: 2, syn_ect_rcv: 2, accecn_fail_mode:4; + u8 saw_accecn_opt :2; #ifdef CONFIG_TCP_AO u8 ao_keyid; u8 ao_rcv_next; @@ -407,7 +408,8 @@ 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 */ + u8 accecn_fail_mode:4, /* AccECN failure handling */ + saw_accecn_opt:2; /* An AccECN option was seen */ u32 tcp_tx_delay; /* delay (in usec) added to TX packets */
/* RTT measurement */ diff --git a/include/net/tcp_ecn.h b/include/net/tcp_ecn.h index 89a01bc99233..d591c4ce1b9a 100644 --- a/include/net/tcp_ecn.h +++ b/include/net/tcp_ecn.h @@ -91,6 +91,11 @@ static inline void tcp_accecn_fail_mode_set(struct tcp_sock *tp, u8 mode) tp->accecn_fail_mode |= mode; }
+#define TCP_ACCECN_OPT_NOT_SEEN 0x0 +#define TCP_ACCECN_OPT_EMPTY_SEEN 0x1 +#define TCP_ACCECN_OPT_COUNTER_SEEN 0x2 +#define TCP_ACCECN_OPT_FAIL_SEEN 0x3 + static inline u8 tcp_accecn_ace(const struct tcphdr *th) { return (th->ae << 2) | (th->cwr << 1) | th->ece; @@ -146,6 +151,14 @@ static inline bool tcp_accecn_validate_syn_feedback(struct sock *sk, u8 ace, return true; }
+static inline void tcp_accecn_saw_opt_fail_recv(struct tcp_sock *tp, + u8 saw_opt) +{ + tp->saw_accecn_opt = saw_opt; + if (tp->saw_accecn_opt == TCP_ACCECN_OPT_FAIL_SEEN) + tcp_accecn_fail_mode_set(tp, TCP_ACCECN_OPT_FAIL_RECV); +} + /* 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) @@ -428,9 +441,35 @@ static inline void tcp_accecn_set_ace(struct tcp_sock *tp, struct sk_buff *skb, } }
+static inline u8 tcp_accecn_option_init(const struct sk_buff *skb, + u8 opt_offset) +{ + u8 *ptr = skb_transport_header(skb) + opt_offset; + unsigned int optlen = ptr[1] - 2; + + if (WARN_ON_ONCE(ptr[0] != TCPOPT_ACCECN0 && ptr[0] != TCPOPT_ACCECN1)) + return TCP_ACCECN_OPT_FAIL_SEEN; + ptr += 2; + + /* Detect option zeroing: an AccECN connection "MAY check that the + * initial value of the EE0B field or the EE1B field is non-zero" + */ + if (optlen < TCPOLEN_ACCECN_PERFIELD) + return TCP_ACCECN_OPT_EMPTY_SEEN; + if (get_unaligned_be24(ptr) == 0) + return TCP_ACCECN_OPT_FAIL_SEEN; + if (optlen < TCPOLEN_ACCECN_PERFIELD * 3) + return TCP_ACCECN_OPT_COUNTER_SEEN; + ptr += TCPOLEN_ACCECN_PERFIELD * 2; + if (get_unaligned_be24(ptr) == 0) + return TCP_ACCECN_OPT_FAIL_SEEN; + + return TCP_ACCECN_OPT_COUNTER_SEEN; +} + /* See Table 2 of the AccECN draft */ -static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct tcphdr *th, - u8 ip_dsfield) +static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct sk_buff *skb, + const struct tcphdr *th, u8 ip_dsfield) { struct tcp_sock *tp = tcp_sk(sk); u8 ace = tcp_accecn_ace(th); @@ -469,7 +508,13 @@ static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct tcphdr *th, default: tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN); tp->syn_ect_rcv = ip_dsfield & INET_ECN_MASK; - tp->accecn_opt_demand = 2; + if (tp->rx_opt.accecn && + tp->saw_accecn_opt < TCP_ACCECN_OPT_COUNTER_SEEN) { + u8 saw_opt = tcp_accecn_option_init(skb, tp->rx_opt.accecn); + + tcp_accecn_saw_opt_fail_recv(tp, saw_opt); + tp->accecn_opt_demand = 2; + } if (INET_ECN_is_ce(ip_dsfield) && tcp_accecn_validate_syn_feedback(sk, ace, tp->syn_ect_snt)) { diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 7808666bafda..6add6959cc92 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3392,6 +3392,7 @@ int tcp_disconnect(struct sock *sk, int flags) tp->delivered = 0; tp->delivered_ce = 0; tp->accecn_fail_mode = 0; + tp->saw_accecn_opt = TCP_ACCECN_OPT_NOT_SEEN; tcp_accecn_init_counters(tp); tp->prev_ecnfield = 0; tp->accecn_opt_tstamp = 0; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 1a8c40b573e4..1098929a4246 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -398,7 +398,22 @@ static bool tcp_accecn_process_option(struct tcp_sock *tp, unsigned int i; u8 *ptr;
+ if (tcp_accecn_opt_fail_recv(tp)) + return false; + if (!(flag & FLAG_SLOWPATH) || !tp->rx_opt.accecn) { + if (!tp->saw_accecn_opt) { + /* Too late to enable after this point due to + * potential counter wraps + */ + if (tp->bytes_sent >= (1 << 23) - 1) { + u8 saw_opt = TCP_ACCECN_OPT_FAIL_SEEN; + + tcp_accecn_saw_opt_fail_recv(tp, saw_opt); + } + return false; + } + if (estimate_ecnfield) { u8 ecnfield = estimate_ecnfield - 1;
@@ -415,6 +430,13 @@ static bool tcp_accecn_process_option(struct tcp_sock *tp, order1 = (ptr[0] == TCPOPT_ACCECN1); ptr += 2;
+ if (tp->saw_accecn_opt < TCP_ACCECN_OPT_COUNTER_SEEN) { + tp->saw_accecn_opt = tcp_accecn_option_init(skb, + tp->rx_opt.accecn); + if (tp->saw_accecn_opt == TCP_ACCECN_OPT_FAIL_SEEN) + tcp_accecn_fail_mode_set(tp, TCP_ACCECN_OPT_FAIL_RECV); + } + res = !!estimate_ecnfield; for (i = 0; i < 3; i++) { u32 init_offset; @@ -6115,7 +6137,13 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, if (th->syn) { if (tcp_ecn_mode_accecn(tp)) { accecn_reflector = true; - tcp_accecn_opt_demand_min(sk, 1); + if (tp->rx_opt.accecn && + tp->saw_accecn_opt < TCP_ACCECN_OPT_COUNTER_SEEN) { + u8 saw_opt = tcp_accecn_option_init(skb, tp->rx_opt.accecn); + + tcp_accecn_saw_opt_fail_recv(tp, saw_opt); + tcp_accecn_opt_demand_min(sk, 1); + } } if (sk->sk_state == TCP_SYN_RECV && sk->sk_socket && th->ack && TCP_SKB_CB(skb)->seq + 1 == TCP_SKB_CB(skb)->end_seq && @@ -6598,7 +6626,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, */
if (tcp_ecn_mode_any(tp)) - tcp_ecn_rcv_synack(sk, th, TCP_SKB_CB(skb)->ip_dsfield); + tcp_ecn_rcv_synack(sk, skb, th, + TCP_SKB_CB(skb)->ip_dsfield);
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); tcp_try_undo_spurious_syn(sk); @@ -7169,6 +7198,8 @@ static void tcp_openreq_init(struct request_sock *req, tcp_rsk(req)->snt_tsval_first = 0; tcp_rsk(req)->last_oow_ack_time = 0; tcp_rsk(req)->accecn_ok = 0; + tcp_rsk(req)->saw_accecn_opt = TCP_ACCECN_OPT_NOT_SEEN; + tcp_rsk(req)->accecn_fail_mode = 0; tcp_rsk(req)->syn_ect_rcv = 0; tcp_rsk(req)->syn_ect_snt = 0; req->mss = rx_opt->mss_clamp; diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 848c756a37b8..fd80e24ea30b 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -473,6 +473,7 @@ static void tcp_ecn_openreq_child(struct sock *sk, 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); + tp->saw_accecn_opt = treq->saw_accecn_opt; tp->prev_ecnfield = treq->syn_ect_rcv; tp->accecn_opt_demand = 1; tcp_ecn_received_counters_payload(sk, skb); @@ -688,6 +689,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, bool own_req;
tmp_opt.saw_tstamp = 0; + tmp_opt.accecn = 0; if (th->doff > (sizeof(struct tcphdr)>>2)) { tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0, NULL);
@@ -865,6 +867,18 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, if (!(flg & TCP_FLAG_ACK)) return NULL;
+ if (tcp_rsk(req)->accecn_ok && tmp_opt.accecn && + tcp_rsk(req)->saw_accecn_opt < TCP_ACCECN_OPT_COUNTER_SEEN) { + u8 saw_opt = tcp_accecn_option_init(skb, tmp_opt.accecn); + + tcp_rsk(req)->saw_accecn_opt = saw_opt; + if (tcp_rsk(req)->saw_accecn_opt == TCP_ACCECN_OPT_FAIL_SEEN) { + u8 fail_mode = TCP_ACCECN_OPT_FAIL_RECV; + + tcp_rsk(req)->accecn_fail_mode |= fail_mode; + } + } + /* For Fast Open no more processing is needed (sk is the * child socket). */ diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 3c755a6d0f9c..a309fb87bd49 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -985,9 +985,14 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, } }
- /* Simultaneous open SYN/ACK needs AccECN option but not SYN */ + /* Simultaneous open SYN/ACK needs AccECN option but not SYN. + * It is attempted to negotiate the use of AccECN also on the first + * retransmitted SYN, as mentioned in "3.1.4.1. Retransmitted SYNs" + * of AccECN draft. + */ if (unlikely((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) && tcp_ecn_mode_accecn(tp) && + inet_csk(sk)->icsk_retransmits < 2 && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) && remaining >= TCPOLEN_ACCECN_BASE)) { opts->use_synack_ecn_bytes = 1; @@ -1076,7 +1081,7 @@ static unsigned int tcp_synack_options(const struct sock *sk,
if (treq->accecn_ok && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) && - remaining >= TCPOLEN_ACCECN_BASE) { + req->num_timeout < 1 && remaining >= TCPOLEN_ACCECN_BASE) { opts->use_synack_ecn_bytes = 1; remaining -= tcp_options_fit_accecn(opts, 0, remaining); } @@ -1156,7 +1161,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb if (tcp_ecn_mode_accecn(tp)) { int ecn_opt = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option);
- if (ecn_opt && + if (ecn_opt && tp->saw_accecn_opt && !tcp_accecn_opt_fail_send(tp) && (ecn_opt >= TCP_ACCECN_OPTION_FULL || tp->accecn_opt_demand || tcp_accecn_option_beacon_check(sk))) { opts->use_synack_ecn_bytes = 0;