[NET] Generalise tcp_listen_opt

This chunks out the accept_queue and tcp_listen_opt code and moves
them to net/core/request_sock.c and include/net/request_sock.h, to
make it useful for other transport protocols, DCCP being the first one
to use it.

Next patches will rename tcp_listen_opt to accept_sock and remove the
inline tcp functions that just call a reqsk_queue_ function.

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

2 files changed, 186 insertions, 38 deletions

diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 08a8fd1d1610..38943ed04e73 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -16,7 +16,9 @@
 #define _REQUEST_SOCK_H
 
 #include <linux/slab.h>
+#include <linux/spinlock.h>
 #include <linux/types.h>
+
 #include <net/sock.h>
 
 struct request_sock;
@@ -74,4 +76,180 @@ static inline void reqsk_free(struct request_sock *req)
         __reqsk_free(req);
 }
 
+extern int sysctl_max_syn_backlog;
+
+/** struct tcp_listen_opt - listen state
+ *
+ * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
+ */
+struct tcp_listen_opt {
+        u8                      max_qlen_log;
+        /* 3 bytes hole, try to use */
+        int                     qlen;
+        int                     qlen_young;
+        int                     clock_hand;
+        u32                     hash_rnd;
+        struct request_sock     *syn_table[0];
+};
+
+/** struct request_sock_queue - queue of request_socks
+ *
+ * @rskq_accept_head - FIFO head of established children
+ * @rskq_accept_tail - FIFO tail of established children
+ * @syn_wait_lock - serializer
+ *
+ * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
+ * lock sock while browsing the listening hash (otherwise it's deadlock prone).
+ *
+ * This lock is acquired in read mode only from listening_get_next() seq_file
+ * op and it's acquired in write mode _only_ from code that is actively
+ * changing rskq_accept_head. All readers that are holding the master sock lock
+ * don't need to grab this lock in read mode too as rskq_accept_head. writes
+ * are always protected from the main sock lock.
+ */
+struct request_sock_queue {
+        struct request_sock     *rskq_accept_head;
+        struct request_sock     *rskq_accept_tail;
+        rwlock_t                syn_wait_lock;
+        struct tcp_listen_opt   *listen_opt;
+};
+
+extern int reqsk_queue_alloc(struct request_sock_queue *queue,
+                             const int nr_table_entries);
+
+static inline struct tcp_listen_opt *reqsk_queue_yank_listen_sk(struct request_sock_queue *queue)
+{
+        struct tcp_listen_opt *lopt;
+
+        write_lock_bh(&queue->syn_wait_lock);
+        lopt = queue->listen_opt;
+        queue->listen_opt = NULL;
+        write_unlock_bh(&queue->syn_wait_lock);
+
+        return lopt;
+}
+
+static inline void reqsk_queue_destroy(struct request_sock_queue *queue)
+{
+        kfree(reqsk_queue_yank_listen_sk(queue));
+}
+
+static inline struct request_sock *
+        reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
+{
+        struct request_sock *req = queue->rskq_accept_head;
+
+        queue->rskq_accept_head = queue->rskq_accept_head = NULL;
+        return req;
+}
+
+static inline int reqsk_queue_empty(struct request_sock_queue *queue)
+{
+        return queue->rskq_accept_head == NULL;
+}
+
+static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
+                                      struct request_sock *req,
+                                      struct request_sock **prev_req)
+{
+        write_lock(&queue->syn_wait_lock);
+        *prev_req = req->dl_next;
+        write_unlock(&queue->syn_wait_lock);
+}
+
+static inline void reqsk_queue_add(struct request_sock_queue *queue,
+                                   struct request_sock *req,
+                                   struct sock *parent,
+                                   struct sock *child)
+{
+        req->sk = child;
+        sk_acceptq_added(parent);
+
+        if (queue->rskq_accept_head == NULL)
+                queue->rskq_accept_head = req;
+        else
+                queue->rskq_accept_tail->dl_next = req;
+
+        queue->rskq_accept_tail = req;
+        req->dl_next = NULL;
+}
+
+static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
+{
+        struct request_sock *req = queue->rskq_accept_head;
+
+        BUG_TRAP(req != NULL);
+
+        queue->rskq_accept_head = req->dl_next;
+        if (queue->rskq_accept_head == NULL)
+                queue->rskq_accept_tail = NULL;
+
+        return req;
+}
+
+static inline struct sock *reqsk_queue_get_child(struct request_sock_queue *queue,
+                                                 struct sock *parent)
+{
+        struct request_sock *req = reqsk_queue_remove(queue);
+        struct sock *child = req->sk;
+
+        BUG_TRAP(child != NULL);
+
+        sk_acceptq_removed(parent);
+        __reqsk_free(req);
+        return child;
+}
+
+static inline int reqsk_queue_removed(struct request_sock_queue *queue,
+                                      struct request_sock *req)
+{
+        struct tcp_listen_opt *lopt = queue->listen_opt;
+
+        if (req->retrans == 0)
+                --lopt->qlen_young;
+
+        return --lopt->qlen;
+}
+
+static inline int reqsk_queue_added(struct request_sock_queue *queue)
+{
+        struct tcp_listen_opt *lopt = queue->listen_opt;
+        const int prev_qlen = lopt->qlen;
+
+        lopt->qlen_young++;
+        lopt->qlen++;
+        return prev_qlen;
+}
+
+static inline int reqsk_queue_len(struct request_sock_queue *queue)
+{
+        return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
+}
+
+static inline int reqsk_queue_len_young(struct request_sock_queue *queue)
+{
+        return queue->listen_opt->qlen_young;
+}
+
+static inline int reqsk_queue_is_full(struct request_sock_queue *queue)
+{
+        return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
+}
+
+static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
+                                        u32 hash, struct request_sock *req,
+                                        unsigned timeout)
+{
+        struct tcp_listen_opt *lopt = queue->listen_opt;
+
+        req->expires = jiffies + timeout;
+        req->retrans = 0;
+        req->sk = NULL;
+        req->dl_next = lopt->syn_table[hash];
+
+        write_lock(&queue->syn_wait_lock);
+        lopt->syn_table[hash] = req;
+        write_unlock(&queue->syn_wait_lock);
+}
+
 #endif /* _REQUEST_SOCK_H */
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 6663086a5e35..a2e323c54457 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1686,71 +1686,41 @@ static inline int tcp_full_space(const struct sock *sk)
 static inline void tcp_acceptq_queue(struct sock *sk, struct request_sock *req,
                                          struct sock *child)
 {
-        struct tcp_sock *tp = tcp_sk(sk);
-
-        req->sk = child;
-        sk_acceptq_added(sk);
-
-        if (!tp->accept_queue_tail) {
-                tp->accept_queue = req;
-        } else {
-                tp->accept_queue_tail->dl_next = req;
-        }
-        tp->accept_queue_tail = req;
-        req->dl_next = NULL;
+        reqsk_queue_add(&tcp_sk(sk)->accept_queue, req, sk, child);
 }
 
-struct tcp_listen_opt
-{
-        u8                      max_qlen_log;   /* log_2 of maximal queued SYNs */
-        int                     qlen;
-        int                     qlen_young;
-        int                     clock_hand;
-        u32                     hash_rnd;
-        struct request_sock     *syn_table[TCP_SYNQ_HSIZE];
-};
-
 static inline void
 tcp_synq_removed(struct sock *sk, struct request_sock *req)
 {
-        struct tcp_listen_opt *lopt = tcp_sk(sk)->listen_opt;
-
-        if (--lopt->qlen == 0)
+        if (reqsk_queue_removed(&tcp_sk(sk)->accept_queue, req) == 0)
                 tcp_delete_keepalive_timer(sk);
-        if (req->retrans == 0)
-                lopt->qlen_young--;
 }
 
 static inline void tcp_synq_added(struct sock *sk)
 {
-        struct tcp_listen_opt *lopt = tcp_sk(sk)->listen_opt;
-
-        if (lopt->qlen++ == 0)
+        if (reqsk_queue_added(&tcp_sk(sk)->accept_queue) == 0)
                 tcp_reset_keepalive_timer(sk, TCP_TIMEOUT_INIT);
-        lopt->qlen_young++;
 }
 
 static inline int tcp_synq_len(struct sock *sk)
 {
-        return tcp_sk(sk)->listen_opt->qlen;
+        return reqsk_queue_len(&tcp_sk(sk)->accept_queue);
 }
 
 static inline int tcp_synq_young(struct sock *sk)
 {
-        return tcp_sk(sk)->listen_opt->qlen_young;
+        return reqsk_queue_len_young(&tcp_sk(sk)->accept_queue);
 }
 
 static inline int tcp_synq_is_full(struct sock *sk)
 {
-        return tcp_synq_len(sk) >> tcp_sk(sk)->listen_opt->max_qlen_log;
+        return reqsk_queue_is_full(&tcp_sk(sk)->accept_queue);
 }
 
 static inline void tcp_synq_unlink(struct tcp_sock *tp, struct request_sock *req,
-                                       struct request_sock **prev)
+                                   struct request_sock **prev)
 {
-        write_lock(&tp->syn_wait_lock);
-        *prev = req->dl_next;
-        write_unlock(&tp->syn_wait_lock);
+        reqsk_queue_unlink(&tp->accept_queue, req, prev);
 }
 
 static inline void tcp_synq_drop(struct sock *sk, struct request_sock *req,