/*
 * Copyright (c) 2006, 2018 Oracle and/or its affiliates. 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 <net/addrconf.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);

/* rds_tcp_tc_count counts only IPv4 connections.
 * rds6_tcp_tc_count counts both IPv4 and IPv6 connections.
 */
static unsigned int rds_tcp_tc_count;
#if IS_ENABLED(CONFIG_IPV6)
static unsigned int rds6_tcp_tc_count;
#endif

/* 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 atomic_t rds_tcp_unloading = ATOMIC_INIT(0);

static struct kmem_cache *rds_tcp_conn_slab;

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

static int rds_tcp_min_sndbuf = SOCK_MIN_SNDBUF;
static 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,
        },
        { }
};

u32 rds_tcp_write_seq(struct rds_tcp_connection *tc)
{
        /* seq# of the last byte of data in tcp send buffer */
        return tcp_sk(tc->t_sock->sk)->write_seq;
}

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);
#if IS_ENABLED(CONFIG_IPV6)
        rds6_tcp_tc_count--;
#endif
        if (!tc->t_cpath->cp_conn->c_isv6)
                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_conn_path *cp)
{
        struct rds_tcp_connection *tc = cp->cp_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
         * cp_transport_data. We quiesce these threads by setting
         * cp_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(&cp->cp_state, RDS_CONN_RESETTING);
        wait_event(cp->cp_waitq, !test_bit(RDS_IN_XMIT, &cp->cp_flags));
        lock_sock(osock->sk);
        /* reset receive side state for rds_tcp_data_recv() for osock  */
        cancel_delayed_work_sync(&cp->cp_send_w);
        cancel_delayed_work_sync(&cp->cp_recv_w);
        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;
        rds_tcp_restore_callbacks(osock, tc);
        release_sock(osock->sk);
        sock_release(osock);
newsock:
        rds_send_path_reset(cp);
        lock_sock(sock->sk);
        rds_tcp_set_callbacks(sock, cp);
        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_conn_path *cp)
{
        struct rds_tcp_connection *tc = cp->cp_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);
#if IS_ENABLED(CONFIG_IPV6)
        rds6_tcp_tc_count++;
#endif
        if (!tc->t_cpath->cp_conn->c_isv6)
                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->t_cpath = cp;
        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 = cp;
        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);
}

/* Handle RDS_INFO_TCP_SOCKETS socket option.  It only returns IPv4
 * connections for backward compatibility.
 */
static void rds_tcp_tc_info(struct socket *rds_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;

        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) {
                struct inet_sock *inet = inet_sk(tc->t_sock->sk);

                if (tc->t_cpath->cp_conn->c_isv6)
                        continue;

                tsinfo.local_addr = inet->inet_saddr;
                tsinfo.local_port = inet->inet_sport;
                tsinfo.peer_addr = inet->inet_daddr;
                tsinfo.peer_port = inet->inet_dport;

                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;
                tsinfo.tos = tc->t_cpath->cp_conn->c_tos;

                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);
}

#if IS_ENABLED(CONFIG_IPV6)
/* Handle RDS6_INFO_TCP_SOCKETS socket option. It returns both IPv4 and
 * IPv6 connections. IPv4 connection address is returned in an IPv4 mapped
 * address.
 */
static void rds6_tcp_tc_info(struct socket *sock, unsigned int len,
                             struct rds_info_iterator *iter,
                             struct rds_info_lengths *lens)
{
        struct rds6_info_tcp_socket tsinfo6;
        struct rds_tcp_connection *tc;
        unsigned long flags;

        spin_lock_irqsave(&rds_tcp_tc_list_lock, flags);

        if (len / sizeof(tsinfo6) < rds6_tcp_tc_count)
                goto out;

        list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {
                struct sock *sk = tc->t_sock->sk;
                struct inet_sock *inet = inet_sk(sk);

                tsinfo6.local_addr = sk->sk_v6_rcv_saddr;
                tsinfo6.local_port = inet->inet_sport;
                tsinfo6.peer_addr = sk->sk_v6_daddr;
                tsinfo6.peer_port = inet->inet_dport;

                tsinfo6.hdr_rem = tc->t_tinc_hdr_rem;
                tsinfo6.data_rem = tc->t_tinc_data_rem;
                tsinfo6.last_sent_nxt = tc->t_last_sent_nxt;
                tsinfo6.last_expected_una = tc->t_last_expected_una;
                tsinfo6.last_seen_una = tc->t_last_seen_una;

                rds_info_copy(iter, &tsinfo6, sizeof(tsinfo6));
        }

out:
        lens->nr = rds6_tcp_tc_count;
        lens->each = sizeof(tsinfo6);

        spin_unlock_irqrestore(&rds_tcp_tc_list_lock, flags);
}
#endif

int rds_tcp_laddr_check(struct net *net, const struct in6_addr *addr,
                        __u32 scope_id)
{
        struct net_device *dev = NULL;
#if IS_ENABLED(CONFIG_IPV6)
        int ret;
#endif

        if (ipv6_addr_v4mapped(addr)) {
                if (inet_addr_type(net, addr->s6_addr32[3]) == RTN_LOCAL)
                        return 0;
                return -EADDRNOTAVAIL;
        }

        /* If the scope_id is specified, check only those addresses
         * hosted on the specified interface.
         */
        if (scope_id != 0) {
                rcu_read_lock();
                dev = dev_get_by_index_rcu(net, scope_id);
                /* scope_id is not valid... */
                if (!dev) {
                        rcu_read_unlock();
                        return -EADDRNOTAVAIL;
                }
                rcu_read_unlock();
        }
#if IS_ENABLED(CONFIG_IPV6)
        ret = ipv6_chk_addr(net, addr, dev, 0);
        if (ret)
                return 0;
#endif
        return -EADDRNOTAVAIL;
}

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);
        if (!tc->t_tcp_node_detached)
                list_del(&tc->t_tcp_node);
        spin_unlock_irqrestore(&rds_tcp_conn_lock, flags);

        kmem_cache_free(rds_tcp_conn_slab, tc);
}

static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp)
{
        struct rds_tcp_connection *tc;
        int i, j;
        int ret = 0;

        for (i = 0; i < RDS_MPATH_WORKERS; i++) {
                tc = kmem_cache_alloc(rds_tcp_conn_slab, gfp);
                if (!tc) {
                        ret = -ENOMEM;
                        goto fail;
                }
                mutex_init(&tc->t_conn_path_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_path[i].cp_transport_data = tc;
                tc->t_cpath = &conn->c_path[i];
                tc->t_tcp_node_detached = true;

                rdsdebug("rds_conn_path [%d] tc %p\n", i,
                         conn->c_path[i].cp_transport_data);
        }
        spin_lock_irq(&rds_tcp_conn_lock);
        for (i = 0; i < RDS_MPATH_WORKERS; i++) {
                tc = conn->c_path[i].cp_transport_data;
                tc->t_tcp_node_detached = false;
                list_add_tail(&tc->t_tcp_node, &rds_tcp_conn_list);
        }
        spin_unlock_irq(&rds_tcp_conn_lock);
fail:
        if (ret) {
                for (j = 0; j < i; j++)
                        rds_tcp_conn_free(conn->c_path[j].cp_transport_data);
        }
        return ret;
}

static bool list_has_conn(struct list_head *list, struct rds_connection *conn)
{
        struct rds_tcp_connection *tc, *_tc;

        list_for_each_entry_safe(tc, _tc, list, t_tcp_node) {
                if (tc->t_cpath->cp_conn == conn)
                        return true;
        }
        return false;
}

static void rds_tcp_set_unloading(void)
{
        atomic_set(&rds_tcp_unloading, 1);
}

static bool rds_tcp_is_unloading(struct rds_connection *conn)
{
        return atomic_read(&rds_tcp_unloading) != 0;
}

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_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
                if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn))
                        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)
                rds_conn_destroy(tc->t_cpath->cp_conn);
}

static void rds_tcp_exit(void);

static u8 rds_tcp_get_tos_map(u8 tos)
{
        /* all user tos mapped to default 0 for TCP transport */
        return 0;
}

struct rds_transport rds_tcp_transport = {
        .laddr_check            = rds_tcp_laddr_check,
        .xmit_path_prepare      = rds_tcp_xmit_path_prepare,
        .xmit_path_complete     = rds_tcp_xmit_path_complete,
        .xmit                   = rds_tcp_xmit,
        .recv_path              = rds_tcp_recv_path,
        .conn_alloc             = rds_tcp_conn_alloc,
        .conn_free              = rds_tcp_conn_free,
        .conn_path_connect      = rds_tcp_conn_path_connect,
        .conn_path_shutdown     = rds_tcp_conn_path_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,
        .get_tos_map            = rds_tcp_get_tos_map,
        .t_owner                = THIS_MODULE,
        .t_name                 = "tcp",
        .t_type                 = RDS_TRANS_TCP,
        .t_prefer_loopback      = 1,
        .t_mp_capable           = 1,
        .t_unloading            = rds_tcp_is_unloading,
};

static unsigned 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);

        tcp_sock_set_nodelay(sock->sk);
        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 sysctl 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;
        }

#if IS_ENABLED(CONFIG_IPV6)
        rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, true);
#else
        rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, false);
#endif
        if (!rtn->rds_tcp_listen_sock) {
                pr_warn("could not set up IPv6 listen sock\n");

#if IS_ENABLED(CONFIG_IPV6)
                /* Try IPv4 as some systems disable IPv6 */
                rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, false);
                if (!rtn->rds_tcp_listen_sock) {
#endif
                        unregister_net_sysctl_table(rtn->rds_tcp_sysctl);
                        rtn->rds_tcp_sysctl = NULL;
                        err = -EAFNOSUPPORT;
                        goto fail;
#if IS_ENABLED(CONFIG_IPV6)
                }
#endif
        }
        INIT_WORK(&rtn->rds_tcp_accept_w, rds_tcp_accept_worker);
        return 0;

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

static void rds_tcp_kill_sock(struct net *net)
{
        struct rds_tcp_connection *tc, *_tc;
        LIST_HEAD(tmp_list);
        struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
        struct socket *lsock = rtn->rds_tcp_listen_sock;

        rtn->rds_tcp_listen_sock = NULL;
        rds_tcp_listen_stop(lsock, &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->t_cpath->cp_conn->c_net);

                if (net != c_net)
                        continue;
                if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn)) {
                        list_move_tail(&tc->t_tcp_node, &tmp_list);
                } else {
                        list_del(&tc->t_tcp_node);
                        tc->t_tcp_node_detached = true;
                }
        }
        spin_unlock_irq(&rds_tcp_conn_lock);
        list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)
                rds_conn_destroy(tc->t_cpath->cp_conn);
}

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

        rds_tcp_kill_sock(net);

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

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

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),
};

void *rds_tcp_listen_sock_def_readable(struct net *net)
{
        struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
        struct socket *lsock = rtn->rds_tcp_listen_sock;

        if (!lsock)
                return NULL;

        return lsock->sk->sk_user_data;
}

/* 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->t_cpath->cp_conn->c_net);

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

                /* reconnect with new parameters */
                rds_conn_path_drop(tc->t_cpath, false);
        }
        spin_unlock_irq(&rds_tcp_conn_lock);
}

static int rds_tcp_skbuf_handler(struct ctl_table *ctl, int write,
                                 void *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_tcp_set_unloading();
        synchronize_rcu();
        rds_info_deregister_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);
#if IS_ENABLED(CONFIG_IPV6)
        rds_info_deregister_func(RDS6_INFO_TCP_SOCKETS, rds6_tcp_tc_info);
#endif
        unregister_pernet_device(&rds_tcp_net_ops);
        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 = rds_tcp_recv_init();
        if (ret)
                goto out_slab;

        ret = register_pernet_device(&rds_tcp_net_ops);
        if (ret)
                goto out_recv;

        rds_trans_register(&rds_tcp_transport);

        rds_info_register_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);
#if IS_ENABLED(CONFIG_IPV6)
        rds_info_register_func(RDS6_INFO_TCP_SOCKETS, rds6_tcp_tc_info);
#endif

        goto out;
out_recv:
        rds_tcp_recv_exit();
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");