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[TCP]: TCP_DEFER_ACCEPT updates - process as established

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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 <mcmanus@ducksong.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McManus 2008-03-21 16:33:01 -07:00 committed by David S. Miller
parent e4c7884028
commit ec3c0982a2
9 changed files with 99 additions and 33 deletions
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7
include/linux/tcp.h
View File

@ -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;

4
include/net/request_sock.h
View File

@ -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;
};

1
include/net/tcp.h
View File

@ -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 */

11
net/ipv4/inet_connection_sock.c
View File

@ -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)

18
net/ipv4/tcp.c
View File

@ -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;

46
net/ipv4/tcp_input.c
View File

@ -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 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
tcp_data_snd_check(sk);
tcp_ack_snd_check(sk);
if (tcp_defer_accept_check(sk))
return -1;
return 0;
csum_error:

8
net/ipv4/tcp_ipv4.c
View File

@ -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;

32
net/ipv4/tcp_minisocks.c
View File

@ -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:

5
net/ipv4/tcp_timer.c
View File

@ -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;