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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
Download patch file Download diff file Expand all files Collapse all files

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: