From ec3c0982a2dd1e671bad8e9d26c28dcba0039d87 Mon Sep 17 00:00:00 2001 From: Patrick McManus Date: Fri, 21 Mar 2008 16:33:01 -0700 Subject: [PATCH] [TCP]: TCP_DEFER_ACCEPT updates - process as established Change TCP_DEFER_ACCEPT implementation so that it transitions a connection to ESTABLISHED after handshake is complete instead of leaving it in SYN-RECV until some data arrvies. Place connection in accept queue when first data packet arrives from slow path. Benefits: - established connection is now reset if it never makes it to the accept queue - diagnostic state of established matches with the packet traces showing completed handshake - TCP_DEFER_ACCEPT timeouts are expressed in seconds and can now be enforced with reasonable accuracy instead of rounding up to next exponential back-off of syn-ack retry. Signed-off-by: Patrick McManus Signed-off-by: David S. Miller --- include/linux/tcp.h | 7 +++++ include/net/request_sock.h | 4 +-- include/net/tcp.h | 1 + net/ipv4/inet_connection_sock.c | 11 +++----- net/ipv4/tcp.c | 18 +++++-------- net/ipv4/tcp_input.c | 46 +++++++++++++++++++++++++++++++++ net/ipv4/tcp_ipv4.c | 8 ++++++ net/ipv4/tcp_minisocks.c | 32 ++++++++++++++--------- net/ipv4/tcp_timer.c | 5 ++++ 9 files changed, 99 insertions(+), 33 deletions(-) diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 08027f1d7f..d96d9b1223 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -239,6 +239,11 @@ static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req) return (struct tcp_request_sock *)req; } +struct tcp_deferred_accept_info { + struct sock *listen_sk; + struct request_sock *request; +}; + struct tcp_sock { /* inet_connection_sock has to be the first member of tcp_sock */ struct inet_connection_sock inet_conn; @@ -374,6 +379,8 @@ struct tcp_sock { unsigned int keepalive_intvl; /* time interval between keep alive probes */ int linger2; + struct tcp_deferred_accept_info defer_tcp_accept; + unsigned long last_synq_overflow; u32 tso_deferred; diff --git a/include/net/request_sock.h b/include/net/request_sock.h index 040780add3..0369f98e9f 100644 --- a/include/net/request_sock.h +++ b/include/net/request_sock.h @@ -115,8 +115,8 @@ struct request_sock_queue { struct request_sock *rskq_accept_head; struct request_sock *rskq_accept_tail; rwlock_t syn_wait_lock; - u8 rskq_defer_accept; - /* 3 bytes hole, try to pack */ + u16 rskq_defer_accept; + /* 2 bytes hole, try to pack */ struct listen_sock *listen_opt; }; diff --git a/include/net/tcp.h b/include/net/tcp.h index 847e1634e1..67cc3956d2 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -139,6 +139,7 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo); #define MAX_TCP_KEEPINTVL 32767 #define MAX_TCP_KEEPCNT 127 #define MAX_TCP_SYNCNT 127 +#define MAX_TCP_ACCEPT_DEFERRED 65535 #define TCP_SYNQ_INTERVAL (HZ/5) /* Period of SYNACK timer */ diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 8a45be9887..cc1a1859a6 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -414,8 +414,7 @@ void inet_csk_reqsk_queue_prune(struct sock *parent, struct inet_connection_sock *icsk = inet_csk(parent); struct request_sock_queue *queue = &icsk->icsk_accept_queue; struct listen_sock *lopt = queue->listen_opt; - int max_retries = icsk->icsk_syn_retries ? : sysctl_tcp_synack_retries; - int thresh = max_retries; + int thresh = icsk->icsk_syn_retries ? : sysctl_tcp_synack_retries; unsigned long now = jiffies; struct request_sock **reqp, *req; int i, budget; @@ -451,9 +450,6 @@ void inet_csk_reqsk_queue_prune(struct sock *parent, } } - if (queue->rskq_defer_accept) - max_retries = queue->rskq_defer_accept; - budget = 2 * (lopt->nr_table_entries / (timeout / interval)); i = lopt->clock_hand; @@ -461,9 +457,8 @@ void inet_csk_reqsk_queue_prune(struct sock *parent, reqp=&lopt->syn_table[i]; while ((req = *reqp) != NULL) { if (time_after_eq(now, req->expires)) { - if ((req->retrans < (inet_rsk(req)->acked ? max_retries : thresh)) && - (inet_rsk(req)->acked || - !req->rsk_ops->rtx_syn_ack(parent, req))) { + if (req->retrans < thresh && + !req->rsk_ops->rtx_syn_ack(parent, req)) { unsigned long timeo; if (req->retrans++ == 0) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 071e83a894..e0fbc25ca8 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2105,15 +2105,12 @@ static int do_tcp_setsockopt(struct sock *sk, int level, break; case TCP_DEFER_ACCEPT: - icsk->icsk_accept_queue.rskq_defer_accept = 0; - if (val > 0) { - /* Translate value in seconds to number of - * retransmits */ - while (icsk->icsk_accept_queue.rskq_defer_accept < 32 && - val > ((TCP_TIMEOUT_INIT / HZ) << - icsk->icsk_accept_queue.rskq_defer_accept)) - icsk->icsk_accept_queue.rskq_defer_accept++; - icsk->icsk_accept_queue.rskq_defer_accept++; + if (val < 0) { + err = -EINVAL; + } else { + if (val > MAX_TCP_ACCEPT_DEFERRED) + val = MAX_TCP_ACCEPT_DEFERRED; + icsk->icsk_accept_queue.rskq_defer_accept = val; } break; @@ -2295,8 +2292,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level, val = (val ? : sysctl_tcp_fin_timeout) / HZ; break; case TCP_DEFER_ACCEPT: - val = !icsk->icsk_accept_queue.rskq_defer_accept ? 0 : - ((TCP_TIMEOUT_INIT / HZ) << (icsk->icsk_accept_queue.rskq_defer_accept - 1)); + val = icsk->icsk_accept_queue.rskq_defer_accept; break; case TCP_WINDOW_CLAMP: val = tp->window_clamp; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 9cf446427c..6e46b4c0f2 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4451,6 +4451,49 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) } } +static int tcp_defer_accept_check(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (tp->defer_tcp_accept.request) { + int queued_data = tp->rcv_nxt - tp->copied_seq; + int hasfin = !skb_queue_empty(&sk->sk_receive_queue) ? + tcp_hdr((struct sk_buff *) + sk->sk_receive_queue.prev)->fin : 0; + + if (queued_data && hasfin) + queued_data--; + + if (queued_data && + tp->defer_tcp_accept.listen_sk->sk_state == TCP_LISTEN) { + if (sock_flag(sk, SOCK_KEEPOPEN)) { + inet_csk_reset_keepalive_timer(sk, + keepalive_time_when(tp)); + } else { + inet_csk_delete_keepalive_timer(sk); + } + + inet_csk_reqsk_queue_add( + tp->defer_tcp_accept.listen_sk, + tp->defer_tcp_accept.request, + sk); + + tp->defer_tcp_accept.listen_sk->sk_data_ready( + tp->defer_tcp_accept.listen_sk, 0); + + sock_put(tp->defer_tcp_accept.listen_sk); + sock_put(sk); + tp->defer_tcp_accept.listen_sk = NULL; + tp->defer_tcp_accept.request = NULL; + } else if (hasfin || + tp->defer_tcp_accept.listen_sk->sk_state != TCP_LISTEN) { + tcp_reset(sk); + return -1; + } + } + return 0; +} + static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) { struct tcp_sock *tp = tcp_sk(sk); @@ -4811,6 +4854,9 @@ step5: tcp_data_snd_check(sk); tcp_ack_snd_check(sk); + + if (tcp_defer_accept_check(sk)) + return -1; return 0; csum_error: diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 0ba6e911c9..167a0f5575 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1920,6 +1920,14 @@ int tcp_v4_destroy_sock(struct sock *sk) sk->sk_sndmsg_page = NULL; } + if (tp->defer_tcp_accept.request) { + reqsk_free(tp->defer_tcp_accept.request); + sock_put(tp->defer_tcp_accept.listen_sk); + sock_put(sk); + tp->defer_tcp_accept.listen_sk = NULL; + tp->defer_tcp_accept.request = NULL; + } + atomic_dec(&tcp_sockets_allocated); return 0; diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 8245247a6c..019c8c16e5 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -571,10 +571,8 @@ struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb, does sequence test, SYN is truncated, and thus we consider it a bare ACK. - If icsk->icsk_accept_queue.rskq_defer_accept, we silently drop this - bare ACK. Otherwise, we create an established connection. Both - ends (listening sockets) accept the new incoming connection and try - to talk to each other. 8-) + Both ends (listening sockets) accept the new incoming + connection and try to talk to each other. 8-) Note: This case is both harmless, and rare. Possibility is about the same as us discovering intelligent life on another plant tomorrow. @@ -642,13 +640,6 @@ struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb, if (!(flg & TCP_FLAG_ACK)) return NULL; - /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */ - if (inet_csk(sk)->icsk_accept_queue.rskq_defer_accept && - TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) { - inet_rsk(req)->acked = 1; - return NULL; - } - /* OK, ACK is valid, create big socket and * feed this segment to it. It will repeat all * the tests. THIS SEGMENT MUST MOVE SOCKET TO @@ -687,7 +678,24 @@ struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb, inet_csk_reqsk_queue_unlink(sk, req, prev); inet_csk_reqsk_queue_removed(sk, req); - inet_csk_reqsk_queue_add(sk, req, child); + if (inet_csk(sk)->icsk_accept_queue.rskq_defer_accept && + TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) { + + /* the accept queue handling is done is est recv slow + * path so lets make sure to start there + */ + tcp_sk(child)->pred_flags = 0; + sock_hold(sk); + sock_hold(child); + tcp_sk(child)->defer_tcp_accept.listen_sk = sk; + tcp_sk(child)->defer_tcp_accept.request = req; + + inet_csk_reset_keepalive_timer(child, + inet_csk(sk)->icsk_accept_queue.rskq_defer_accept * HZ); + } else { + inet_csk_reqsk_queue_add(sk, req, child); + } + return child; listen_overflow: diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 803d758a2b..160d16f9f4 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -481,6 +481,11 @@ static void tcp_keepalive_timer (unsigned long data) goto death; } + if (tp->defer_tcp_accept.request && sk->sk_state == TCP_ESTABLISHED) { + tcp_send_active_reset(sk, GFP_ATOMIC); + goto death; + } + if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE) goto out; -- 2.39.5