- struct tcp_opt *tp = tcp_sk(sk);
- struct tcp_listen_opt *lopt = tp->listen_opt;
- int max_retries = tp->syn_retries ? : sysctl_tcp_synack_retries;
- int thresh = max_retries;
- unsigned long now = jiffies;
- struct open_request **reqp, *req;
- int i, budget;
-
- if (lopt == NULL || lopt->qlen == 0)
- return;
-
- /* Normally all the openreqs are young and become mature
- * (i.e. converted to established socket) for first timeout.
- * If synack was not acknowledged for 3 seconds, it means
- * one of the following things: synack was lost, ack was lost,
- * rtt is high or nobody planned to ack (i.e. synflood).
- * When server is a bit loaded, queue is populated with old
- * open requests, reducing effective size of queue.
- * When server is well loaded, queue size reduces to zero
- * after several minutes of work. It is not synflood,
- * it is normal operation. The solution is pruning
- * too old entries overriding normal timeout, when
- * situation becomes dangerous.
- *
- * Essentially, we reserve half of room for young
- * embrions; and abort old ones without pity, if old
- * ones are about to clog our table.
- */
- if (lopt->qlen>>(lopt->max_qlen_log-1)) {
- int young = (lopt->qlen_young<<1);
-
- while (thresh > 2) {
- if (lopt->qlen < young)
- break;
- thresh--;
- young <<= 1;
- }
- }
-
- if (tp->defer_accept)
- max_retries = tp->defer_accept;
-
- budget = 2*(TCP_SYNQ_HSIZE/(TCP_TIMEOUT_INIT/TCP_SYNQ_INTERVAL));
- i = lopt->clock_hand;
-
- do {
- reqp=&lopt->syn_table[i];
- while ((req = *reqp) != NULL) {
- if (time_after_eq(now, req->expires)) {
- if ((req->retrans < thresh ||
- (req->acked && req->retrans < max_retries))
- && !req->class->rtx_syn_ack(sk, req, NULL)) {
- unsigned long timeo;
-
- if (req->retrans++ == 0)
- lopt->qlen_young--;
- timeo = min((TCP_TIMEOUT_INIT << req->retrans),
- TCP_RTO_MAX);
- req->expires = now + timeo;
- reqp = &req->dl_next;
- continue;
- }
-
- /* Drop this request */
- write_lock(&tp->syn_wait_lock);
- *reqp = req->dl_next;
- write_unlock(&tp->syn_wait_lock);
- lopt->qlen--;
- if (req->retrans == 0)
- lopt->qlen_young--;
- tcp_openreq_free(req);
- continue;
- }
- reqp = &req->dl_next;
- }
-
- i = (i+1)&(TCP_SYNQ_HSIZE-1);
-
- } while (--budget > 0);
-
- lopt->clock_hand = i;
-
- if (lopt->qlen)
- tcp_reset_keepalive_timer(sk, TCP_SYNQ_INTERVAL);
-}
-
-void tcp_delete_keepalive_timer (struct sock *sk)
-{
- sk_stop_timer(sk, &sk->sk_timer);
-}
-
-void tcp_reset_keepalive_timer (struct sock *sk, unsigned long len)
-{
- sk_reset_timer(sk, &sk->sk_timer, jiffies + len);