/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/in.h>
#include <linux/module.h>
#include <net/tcp.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

#include "rds.h"
#include "tcp.h"

/* only for info exporting */
static DEFINE_SPINLOCK(rds_tcp_tc_list_lock);
static LIST_HEAD(rds_tcp_tc_list);
static unsigned int rds_tcp_tc_count;

/* Track rds_tcp_connection structs so they can be cleaned up */
static DEFINE_SPINLOCK(rds_tcp_conn_lock);
static LIST_HEAD(rds_tcp_conn_list);

static struct kmem_cache *rds_tcp_conn_slab;

static int rds_tcp_skbuf_handler(struct ctl_table *ctl, int write,
                                 void __user *buffer, size_t *lenp,
                                 loff_t *fpos);

int rds_tcp_min_sndbuf = SOCK_MIN_SNDBUF;
int rds_tcp_min_rcvbuf = SOCK_MIN_RCVBUF;

static struct ctl_table rds_tcp_sysctl_table[] = {
#define RDS_TCP_SNDBUF  0
        {
                .procname       = "rds_tcp_sndbuf",
                /* data is per-net pointer */
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = rds_tcp_skbuf_handler,
                .extra1         = &rds_tcp_min_sndbuf,
        },
#define RDS_TCP_RCVBUF  1
        {
                .procname       = "rds_tcp_rcvbuf",
                /* data is per-net pointer */
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = rds_tcp_skbuf_handler,
                .extra1         = &rds_tcp_min_rcvbuf,
        },
        { }
};

/* doing it this way avoids calling tcp_sk() */
void rds_tcp_nonagle(struct socket *sock)
{
        mm_segment_t oldfs = get_fs();
        int val = 1;

        set_fs(KERNEL_DS);
        sock->ops->setsockopt(sock, SOL_TCP, TCP_NODELAY, (char __user *)&val,
                              sizeof(val));
        set_fs(oldfs);
}

u32 rds_tcp_snd_nxt(struct rds_tcp_connection *tc)
{
        return tcp_sk(tc->t_sock->sk)->snd_nxt;
}

u32 rds_tcp_snd_una(struct rds_tcp_connection *tc)
{
        return tcp_sk(tc->t_sock->sk)->snd_una;
}

void rds_tcp_restore_callbacks(struct socket *sock,
                               struct rds_tcp_connection *tc)
{
        rdsdebug("restoring sock %p callbacks from tc %p\n", sock, tc);
        write_lock_bh(&sock->sk->sk_callback_lock);

        /* done under the callback_lock to serialize with write_space */
        spin_lock(&rds_tcp_tc_list_lock);
        list_del_init(&tc->t_list_item);
        rds_tcp_tc_count--;
        spin_unlock(&rds_tcp_tc_list_lock);

        tc->t_sock = NULL;

        sock->sk->sk_write_space = tc->t_orig_write_space;
        sock->sk->sk_data_ready = tc->t_orig_data_ready;
        sock->sk->sk_state_change = tc->t_orig_state_change;
        sock->sk->sk_user_data = NULL;

        write_unlock_bh(&sock->sk->sk_callback_lock);
}

/*
 * rds_tcp_reset_callbacks() switches the to the new sock and
 * returns the existing tc->t_sock.
 *
 * The only functions that set tc->t_sock are rds_tcp_set_callbacks
 * and rds_tcp_reset_callbacks.  Send and receive trust that
 * it is set.  The absence of RDS_CONN_UP bit protects those paths
 * from being called while it isn't set.
 */
void rds_tcp_reset_callbacks(struct socket *sock,
                             struct rds_connection *conn)
{
        struct rds_tcp_connection *tc = conn->c_transport_data;
        struct socket *osock = tc->t_sock;

        if (!osock)
                goto newsock;

        /* Need to resolve a duelling SYN between peers.
         * We have an outstanding SYN to this peer, which may
         * potentially have transitioned to the RDS_CONN_UP state,
         * so we must quiesce any send threads before resetting
         * c_transport_data. We quiesce these threads by setting
         * c_state to something other than RDS_CONN_UP, and then
         * waiting for any existing threads in rds_send_xmit to
         * complete release_in_xmit(). (Subsequent threads entering
         * rds_send_xmit() will bail on !rds_conn_up().
         *
         * However an incoming syn-ack at this point would end up
         * marking the conn as RDS_CONN_UP, and would again permit
         * rds_send_xmi() threads through, so ideally we would
         * synchronize on RDS_CONN_UP after lock_sock(), but cannot
         * do that: waiting on !RDS_IN_XMIT after lock_sock() may
         * end up deadlocking with tcp_sendmsg(), and the RDS_IN_XMIT
         * would not get set. As a result, we set c_state to
         * RDS_CONN_RESETTTING, to ensure that rds_tcp_state_change
         * cannot mark rds_conn_path_up() in the window before lock_sock()
         */
        atomic_set(&conn->c_state, RDS_CONN_RESETTING);
        wait_event(conn->c_waitq, !test_bit(RDS_IN_XMIT, &conn->c_flags));
        lock_sock(osock->sk);
        /* reset receive side state for rds_tcp_data_recv() for osock  */
        if (tc->t_tinc) {
                rds_inc_put(&tc->t_tinc->ti_inc);
                tc->t_tinc = NULL;
        }
        tc->t_tinc_hdr_rem = sizeof(struct rds_header);
        tc->t_tinc_data_rem = 0;
        tc->t_sock = NULL;

        write_lock_bh(&osock->sk->sk_callback_lock);

        osock->sk->sk_user_data = NULL;
        osock->sk->sk_data_ready = tc->t_orig_data_ready;
        osock->sk->sk_write_space = tc->t_orig_write_space;
        osock->sk->sk_state_change = tc->t_orig_state_change;
        write_unlock_bh(&osock->sk->sk_callback_lock);
        release_sock(osock->sk);
        sock_release(osock);
newsock:
        rds_send_reset(conn);
        lock_sock(sock->sk);
        write_lock_bh(&sock->sk->sk_callback_lock);
        tc->t_sock = sock;
        sock->sk->sk_user_data = conn;
        sock->sk->sk_data_ready = rds_tcp_data_ready;
        sock->sk->sk_write_space = rds_tcp_write_space;
        sock->sk->sk_state_change = rds_tcp_state_change;

        write_unlock_bh(&sock->sk->sk_callback_lock);
        release_sock(sock->sk);
}

/* Add tc to rds_tcp_tc_list and set tc->t_sock. See comments
 * above rds_tcp_reset_callbacks for notes about synchronization
 * with data path
 */
void rds_tcp_set_callbacks(struct socket *sock, struct rds_connection *conn)
{
        struct rds_tcp_connection *tc = conn->c_transport_data;

        rdsdebug("setting sock %p callbacks to tc %p\n", sock, tc);
        write_lock_bh(&sock->sk->sk_callback_lock);

        /* done under the callback_lock to serialize with write_space */
        spin_lock(&rds_tcp_tc_list_lock);
        list_add_tail(&tc->t_list_item, &rds_tcp_tc_list);
        rds_tcp_tc_count++;
        spin_unlock(&rds_tcp_tc_list_lock);

        /* accepted sockets need our listen data ready undone */
        if (sock->sk->sk_data_ready == rds_tcp_listen_data_ready)
                sock->sk->sk_data_ready = sock->sk->sk_user_data;

        tc->t_sock = sock;
        tc->conn = conn;
        tc->t_orig_data_ready = sock->sk->sk_data_ready;
        tc->t_orig_write_space = sock->sk->sk_write_space;
        tc->t_orig_state_change = sock->sk->sk_state_change;

        sock->sk->sk_user_data = conn;
        sock->sk->sk_data_ready = rds_tcp_data_ready;
        sock->sk->sk_write_space = rds_tcp_write_space;
        sock->sk->sk_state_change = rds_tcp_state_change;

        write_unlock_bh(&sock->sk->sk_callback_lock);
}

static void rds_tcp_tc_info(struct socket *sock, unsigned int len,
                            struct rds_info_iterator *iter,
                            struct rds_info_lengths *lens)
{
        struct rds_info_tcp_socket tsinfo;
        struct rds_tcp_connection *tc;
        unsigned long flags;
        struct sockaddr_in sin;
        int sinlen;

        spin_lock_irqsave(&rds_tcp_tc_list_lock, flags);

        if (len / sizeof(tsinfo) < rds_tcp_tc_count)
                goto out;

        list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {

                sock->ops->getname(sock, (struct sockaddr *)&sin, &sinlen, 0);
                tsinfo.local_addr = sin.sin_addr.s_addr;
                tsinfo.local_port = sin.sin_port;
                sock->ops->getname(sock, (struct sockaddr *)&sin, &sinlen, 1);
                tsinfo.peer_addr = sin.sin_addr.s_addr;
                tsinfo.peer_port = sin.sin_port;

                tsinfo.hdr_rem = tc->t_tinc_hdr_rem;
                tsinfo.data_rem = tc->t_tinc_data_rem;
                tsinfo.last_sent_nxt = tc->t_last_sent_nxt;
                tsinfo.last_expected_una = tc->t_last_expected_una;
                tsinfo.last_seen_una = tc->t_last_seen_una;

                rds_info_copy(iter, &tsinfo, sizeof(tsinfo));
        }

out:
        lens->nr = rds_tcp_tc_count;
        lens->each = sizeof(tsinfo);

        spin_unlock_irqrestore(&rds_tcp_tc_list_lock, flags);
}

static int rds_tcp_laddr_check(struct net *net, __be32 addr)
{
        if (inet_addr_type(net, addr) == RTN_LOCAL)
                return 0;
        return -EADDRNOTAVAIL;
}

static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp)
{
        struct rds_tcp_connection *tc;

        tc = kmem_cache_alloc(rds_tcp_conn_slab, gfp);
        if (!tc)
                return -ENOMEM;

        mutex_init(&tc->t_conn_lock);
        tc->t_sock = NULL;
        tc->t_tinc = NULL;
        tc->t_tinc_hdr_rem = sizeof(struct rds_header);
        tc->t_tinc_data_rem = 0;

        conn->c_transport_data = tc;

        spin_lock_irq(&rds_tcp_conn_lock);
        list_add_tail(&tc->t_tcp_node, &rds_tcp_conn_list);
        spin_unlock_irq(&rds_tcp_conn_lock);

        rdsdebug("alloced tc %p\n", conn->c_transport_data);
        return 0;
}

static void rds_tcp_conn_free(void *arg)
{
        struct rds_tcp_connection *tc = arg;
        unsigned long flags;
        rdsdebug("freeing tc %p\n", tc);

        spin_lock_irqsave(&rds_tcp_conn_lock, flags);
        list_del(&tc->t_tcp_node);
        spin_unlock_irqrestore(&rds_tcp_conn_lock, flags);

        kmem_cache_free(rds_tcp_conn_slab, tc);
}

static void rds_tcp_destroy_conns(void)
{
        struct rds_tcp_connection *tc, *_tc;
        LIST_HEAD(tmp_list);

        /* avoid calling conn_destroy with irqs off */
        spin_lock_irq(&rds_tcp_conn_lock);
        list_splice(&rds_tcp_conn_list, &tmp_list);
        INIT_LIST_HEAD(&rds_tcp_conn_list);
        spin_unlock_irq(&rds_tcp_conn_lock);

        list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node) {
                if (tc->conn->c_passive)
                        rds_conn_destroy(tc->conn->c_passive);
                rds_conn_destroy(tc->conn);
        }
}

static void rds_tcp_exit(void);

struct rds_transport rds_tcp_transport = {
        .laddr_check            = rds_tcp_laddr_check,
        .xmit_prepare           = rds_tcp_xmit_prepare,
        .xmit_complete          = rds_tcp_xmit_complete,
        .xmit                   = rds_tcp_xmit,
        .recv                   = rds_tcp_recv,
        .conn_alloc             = rds_tcp_conn_alloc,
        .conn_free              = rds_tcp_conn_free,
        .conn_connect           = rds_tcp_conn_connect,
        .conn_shutdown          = rds_tcp_conn_shutdown,
        .inc_copy_to_user       = rds_tcp_inc_copy_to_user,
        .inc_free               = rds_tcp_inc_free,
        .stats_info_copy        = rds_tcp_stats_info_copy,
        .exit                   = rds_tcp_exit,
        .t_owner                = THIS_MODULE,
        .t_name                 = "tcp",
        .t_type                 = RDS_TRANS_TCP,
        .t_prefer_loopback      = 1,
};

static int rds_tcp_netid;

/* per-network namespace private data for this module */
struct rds_tcp_net {
        struct socket *rds_tcp_listen_sock;
        struct work_struct rds_tcp_accept_w;
        struct ctl_table_header *rds_tcp_sysctl;
        struct ctl_table *ctl_table;
        int sndbuf_size;
        int rcvbuf_size;
};

/* All module specific customizations to the RDS-TCP socket should be done in
 * rds_tcp_tune() and applied after socket creation.
 */
void rds_tcp_tune(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct net *net = sock_net(sk);
        struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

        rds_tcp_nonagle(sock);
        lock_sock(sk);
        if (rtn->sndbuf_size > 0) {
                sk->sk_sndbuf = rtn->sndbuf_size;
                sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
        }
        if (rtn->rcvbuf_size > 0) {
                sk->sk_sndbuf = rtn->rcvbuf_size;
                sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
        }
        release_sock(sk);
}

static void rds_tcp_accept_worker(struct work_struct *work)
{
        struct rds_tcp_net *rtn = container_of(work,
                                               struct rds_tcp_net,
                                               rds_tcp_accept_w);

        while (rds_tcp_accept_one(rtn->rds_tcp_listen_sock) == 0)
                cond_resched();
}

void rds_tcp_accept_work(struct sock *sk)
{
        struct net *net = sock_net(sk);
        struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

        queue_work(rds_wq, &rtn->rds_tcp_accept_w);
}

static __net_init int rds_tcp_init_net(struct net *net)
{
        struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
        struct ctl_table *tbl;
        int err = 0;

        memset(rtn, 0, sizeof(*rtn));

        /* {snd, rcv}buf_size default to 0, which implies we let the
         * stack pick the value, and permit auto-tuning of buffer size.
         */
        if (net == &init_net) {
                tbl = rds_tcp_sysctl_table;
        } else {
                tbl = kmemdup(rds_tcp_sysctl_table,
                              sizeof(rds_tcp_sysctl_table), GFP_KERNEL);
                if (!tbl) {
                        pr_warn("could not set allocate syctl table\n");
                        return -ENOMEM;
                }
                rtn->ctl_table = tbl;
        }
        tbl[RDS_TCP_SNDBUF].data = &rtn->sndbuf_size;
        tbl[RDS_TCP_RCVBUF].data = &rtn->rcvbuf_size;
        rtn->rds_tcp_sysctl = register_net_sysctl(net, "net/rds/tcp", tbl);
        if (!rtn->rds_tcp_sysctl) {
                pr_warn("could not register sysctl\n");
                err = -ENOMEM;
                goto fail;
        }
        rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net);
        if (!rtn->rds_tcp_listen_sock) {
                pr_warn("could not set up listen sock\n");
                unregister_net_sysctl_table(rtn->rds_tcp_sysctl);
                rtn->rds_tcp_sysctl = NULL;
                err = -EAFNOSUPPORT;
                goto fail;
        }
        INIT_WORK(&rtn->rds_tcp_accept_w, rds_tcp_accept_worker);
        return 0;

fail:
        if (net != &init_net)
                kfree(tbl);
        return err;
}

static void __net_exit rds_tcp_exit_net(struct net *net)
{
        struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

        if (rtn->rds_tcp_sysctl)
                unregister_net_sysctl_table(rtn->rds_tcp_sysctl);

        if (net != &init_net && rtn->ctl_table)
                kfree(rtn->ctl_table);

        /* If rds_tcp_exit_net() is called as a result of netns deletion,
         * the rds_tcp_kill_sock() device notifier would already have cleaned
         * up the listen socket, thus there is no work to do in this function.
         *
         * If rds_tcp_exit_net() is called as a result of module unload,
         * i.e., due to rds_tcp_exit() -> unregister_pernet_subsys(), then
         * we do need to clean up the listen socket here.
         */
        if (rtn->rds_tcp_listen_sock) {
                rds_tcp_listen_stop(rtn->rds_tcp_listen_sock);
                rtn->rds_tcp_listen_sock = NULL;
                flush_work(&rtn->rds_tcp_accept_w);
        }
}

static struct pernet_operations rds_tcp_net_ops = {
        .init = rds_tcp_init_net,
        .exit = rds_tcp_exit_net,
        .id = &rds_tcp_netid,
        .size = sizeof(struct rds_tcp_net),
};

static void rds_tcp_kill_sock(struct net *net)
{
        struct rds_tcp_connection *tc, *_tc;
        struct sock *sk;
        LIST_HEAD(tmp_list);
        struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

        rds_tcp_listen_stop(rtn->rds_tcp_listen_sock);
        rtn->rds_tcp_listen_sock = NULL;
        flush_work(&rtn->rds_tcp_accept_w);
        spin_lock_irq(&rds_tcp_conn_lock);
        list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
                struct net *c_net = read_pnet(&tc->conn->c_net);

                if (net != c_net || !tc->t_sock)
                        continue;
                list_move_tail(&tc->t_tcp_node, &tmp_list);
        }
        spin_unlock_irq(&rds_tcp_conn_lock);
        list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node) {
                sk = tc->t_sock->sk;
                sk->sk_prot->disconnect(sk, 0);
                tcp_done(sk);
                if (tc->conn->c_passive)
                        rds_conn_destroy(tc->conn->c_passive);
                rds_conn_destroy(tc->conn);
        }
}

static int rds_tcp_dev_event(struct notifier_block *this,
                             unsigned long event, void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);

        /* rds-tcp registers as a pernet subys, so the ->exit will only
         * get invoked after network acitivity has quiesced. We need to
         * clean up all sockets  to quiesce network activity, and use
         * the unregistration of the per-net loopback device as a trigger
         * to start that cleanup.
         */
        if (event == NETDEV_UNREGISTER_FINAL &&
            dev->ifindex == LOOPBACK_IFINDEX)
                rds_tcp_kill_sock(dev_net(dev));

        return NOTIFY_DONE;
}

static struct notifier_block rds_tcp_dev_notifier = {
        .notifier_call        = rds_tcp_dev_event,
        .priority = -10, /* must be called after other network notifiers */
};

/* when sysctl is used to modify some kernel socket parameters,this
 * function  resets the RDS connections in that netns  so that we can
 * restart with new parameters.  The assumption is that such reset
 * events are few and far-between.
 */
static void rds_tcp_sysctl_reset(struct net *net)
{
        struct rds_tcp_connection *tc, *_tc;

        spin_lock_irq(&rds_tcp_conn_lock);
        list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
                struct net *c_net = read_pnet(&tc->conn->c_net);

                if (net != c_net || !tc->t_sock)
                        continue;

                rds_conn_drop(tc->conn); /* reconnect with new parameters */
        }
        spin_unlock_irq(&rds_tcp_conn_lock);
}

static int rds_tcp_skbuf_handler(struct ctl_table *ctl, int write,
                                 void __user *buffer, size_t *lenp,
                                 loff_t *fpos)
{
        struct net *net = current->nsproxy->net_ns;
        int err;

        err = proc_dointvec_minmax(ctl, write, buffer, lenp, fpos);
        if (err < 0) {
                pr_warn("Invalid input. Must be >= %d\n",
                        *(int *)(ctl->extra1));
                return err;
        }
        if (write)
                rds_tcp_sysctl_reset(net);
        return 0;
}

static void rds_tcp_exit(void)
{
        rds_info_deregister_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);
        unregister_pernet_subsys(&rds_tcp_net_ops);
        if (unregister_netdevice_notifier(&rds_tcp_dev_notifier))
                pr_warn("could not unregister rds_tcp_dev_notifier\n");
        rds_tcp_destroy_conns();
        rds_trans_unregister(&rds_tcp_transport);
        rds_tcp_recv_exit();
        kmem_cache_destroy(rds_tcp_conn_slab);
}
module_exit(rds_tcp_exit);

static int rds_tcp_init(void)
{
        int ret;

        rds_tcp_conn_slab = kmem_cache_create("rds_tcp_connection",
                                              sizeof(struct rds_tcp_connection),
                                              0, 0, NULL);
        if (!rds_tcp_conn_slab) {
                ret = -ENOMEM;
                goto out;
        }

        ret = register_netdevice_notifier(&rds_tcp_dev_notifier);
        if (ret) {
                pr_warn("could not register rds_tcp_dev_notifier\n");
                goto out;
        }

        ret = register_pernet_subsys(&rds_tcp_net_ops);
        if (ret)
                goto out_slab;

        ret = rds_tcp_recv_init();
        if (ret)
                goto out_pernet;

        ret = rds_trans_register(&rds_tcp_transport);
        if (ret)
                goto out_recv;

        rds_info_register_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);

        goto out;

out_recv:
        rds_tcp_recv_exit();
out_pernet:
        unregister_pernet_subsys(&rds_tcp_net_ops);
out_slab:
        kmem_cache_destroy(rds_tcp_conn_slab);
out:
        return ret;
}
module_init(rds_tcp_init);

MODULE_AUTHOR("Oracle Corporation <rds-devel@oss.oracle.com>");
MODULE_DESCRIPTION("RDS: TCP transport");
MODULE_LICENSE("Dual BSD/GPL");