[ICSK]: Move generalised functions from tcp to inet_connection_sock

This also improves reqsk_queue_prune and renames it to
inet_csk_reqsk_queue_prune, as it deals with both inet_connection_sock
and inet_request_sock objects, not just with request_sock ones thus
belonging to inet_request_sock.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 214 insertions, 0 deletions

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 136ada050b63..026630a15ea0 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -23,6 +23,7 @@
 #include <net/ip.h>
 #include <net/route.h>
 #include <net/tcp_states.h>
+#include <net/xfrm.h>
 
 #ifdef INET_CSK_DEBUG
 const char inet_csk_timer_bug_msg[] = "inet_csk BUG: unknown timer value\n";
@@ -398,8 +399,100 @@ void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
         inet_csk_reqsk_queue_added(sk, timeout);
 }
 
+/* Only thing we need from tcp.h */
+extern int sysctl_tcp_synack_retries;
+
 EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_hash_add);
 
+void inet_csk_reqsk_queue_prune(struct sock *parent,
+                                const unsigned long interval,
+                                const unsigned long timeout,
+                                const unsigned long max_rto)
+{
+        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;
+        unsigned long now = jiffies;
+        struct request_sock **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 (queue->rskq_defer_accept)
+                max_retries = queue->rskq_defer_accept;
+
+        budget = 2 * (lopt->nr_table_entries / (timeout / 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 ||
+                                     (inet_rsk(req)->acked && req->retrans < max_retries))
+                                    && !req->rsk_ops->rtx_syn_ack(parent, req, NULL)) {
+                                        unsigned long timeo;
+
+                                        if (req->retrans++ == 0)
+                                                lopt->qlen_young--;
+                                        timeo = min((timeout << req->retrans), max_rto);
+                                        req->expires = now + timeo;
+                                        reqp = &req->dl_next;
+                                        continue;
+                                }
+
+                                /* Drop this request */
+                                inet_csk_reqsk_queue_unlink(parent, req, reqp);
+                                reqsk_queue_removed(queue, req);
+                                reqsk_free(req);
+                                continue;
+                        }
+                        reqp = &req->dl_next;
+                }
+
+                i = (i + 1) & (lopt->nr_table_entries - 1);
+
+        } while (--budget > 0);
+
+        lopt->clock_hand = i;
+
+        if (lopt->qlen)
+                inet_csk_reset_keepalive_timer(parent, interval);
+}
+
+EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_prune);
+
 struct sock *inet_csk_clone(struct sock *sk, const struct request_sock *req,
                             const unsigned int __nocast priority)
 {
@@ -424,3 +517,124 @@ struct sock *inet_csk_clone(struct sock *sk, const struct request_sock *req,
 }
 
 EXPORT_SYMBOL_GPL(inet_csk_clone);
+
+/*
+ * At this point, there should be no process reference to this
+ * socket, and thus no user references at all.  Therefore we
+ * can assume the socket waitqueue is inactive and nobody will
+ * try to jump onto it.
+ */
+void inet_csk_destroy_sock(struct sock *sk)
+{
+        BUG_TRAP(sk->sk_state == TCP_CLOSE);
+        BUG_TRAP(sock_flag(sk, SOCK_DEAD));
+
+        /* It cannot be in hash table! */
+        BUG_TRAP(sk_unhashed(sk));
+
+        /* If it has not 0 inet_sk(sk)->num, it must be bound */
+        BUG_TRAP(!inet_sk(sk)->num || inet_csk(sk)->icsk_bind_hash);
+
+        sk->sk_prot->destroy(sk);
+
+        sk_stream_kill_queues(sk);
+
+        xfrm_sk_free_policy(sk);
+
+        sk_refcnt_debug_release(sk);
+
+        atomic_dec(sk->sk_prot->orphan_count);
+        sock_put(sk);
+}
+
+EXPORT_SYMBOL(inet_csk_destroy_sock);
+
+int inet_csk_listen_start(struct sock *sk, const int nr_table_entries)
+{
+        struct inet_sock *inet = inet_sk(sk);
+        struct inet_connection_sock *icsk = inet_csk(sk);
+        int rc = reqsk_queue_alloc(&icsk->icsk_accept_queue, nr_table_entries);
+
+        if (rc != 0)
+                return rc;
+
+        sk->sk_max_ack_backlog = 0;
+        sk->sk_ack_backlog = 0;
+        inet_csk_delack_init(sk);
+
+        /* There is race window here: we announce ourselves listening,
+         * but this transition is still not validated by get_port().
+         * It is OK, because this socket enters to hash table only
+         * after validation is complete.
+         */
+        sk->sk_state = TCP_LISTEN;
+        if (!sk->sk_prot->get_port(sk, inet->num)) {
+                inet->sport = htons(inet->num);
+
+                sk_dst_reset(sk);
+                sk->sk_prot->hash(sk);
+
+                return 0;
+        }
+
+        sk->sk_state = TCP_CLOSE;
+        __reqsk_queue_destroy(&icsk->icsk_accept_queue);
+        return -EADDRINUSE;
+}
+
+EXPORT_SYMBOL_GPL(inet_csk_listen_start);
+
+/*
+ *      This routine closes sockets which have been at least partially
+ *      opened, but not yet accepted.
+ */
+void inet_csk_listen_stop(struct sock *sk)
+{
+        struct inet_connection_sock *icsk = inet_csk(sk);
+        struct request_sock *acc_req;
+        struct request_sock *req;
+
+        inet_csk_delete_keepalive_timer(sk);
+
+        /* make all the listen_opt local to us */
+        acc_req = reqsk_queue_yank_acceptq(&icsk->icsk_accept_queue);
+
+        /* Following specs, it would be better either to send FIN
+         * (and enter FIN-WAIT-1, it is normal close)
+         * or to send active reset (abort).
+         * Certainly, it is pretty dangerous while synflood, but it is
+         * bad justification for our negligence 8)
+         * To be honest, we are not able to make either
+         * of the variants now.                 --ANK
+         */
+        reqsk_queue_destroy(&icsk->icsk_accept_queue);
+
+        while ((req = acc_req) != NULL) {
+                struct sock *child = req->sk;
+
+                acc_req = req->dl_next;
+
+                local_bh_disable();
+                bh_lock_sock(child);
+                BUG_TRAP(!sock_owned_by_user(child));
+                sock_hold(child);
+
+                sk->sk_prot->disconnect(child, O_NONBLOCK);
+
+                sock_orphan(child);
+
+                atomic_inc(sk->sk_prot->orphan_count);
+
+                inet_csk_destroy_sock(child);
+
+                bh_unlock_sock(child);
+                local_bh_enable();
+                sock_put(child);
+
+                sk_acceptq_removed(sk);
+                __reqsk_free(req);
+        }
+        BUG_TRAP(!sk->sk_ack_backlog);
+}
+
+EXPORT_SYMBOL_GPL(inet_csk_listen_stop);