/*
 * 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/gfp.h>
#include <linux/in.h>
#include <net/tcp.h>
#include <trace/events/sock.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

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

void rds_tcp_keepalive(struct socket *sock)
{
        /* values below based on xs_udp_default_timeout */
        int keepidle = 5; /* send a probe 'keepidle' secs after last data */
        int keepcnt = 5; /* number of unack'ed probes before declaring dead */

        sock_set_keepalive(sock->sk);
        tcp_sock_set_keepcnt(sock->sk, keepcnt);
        tcp_sock_set_keepidle(sock->sk, keepidle);
        /* KEEPINTVL is the interval between successive probes. We follow
         * the model in xs_tcp_finish_connecting() and re-use keepidle.
         */
        tcp_sock_set_keepintvl(sock->sk, keepidle);
}

static int
rds_tcp_get_peer_sport(struct socket *sock)
{
        struct sock *sk = sock->sk;

        if (!sk)
                return -1;

        return ntohs(READ_ONCE(inet_sk(sk)->inet_dport));
}

/* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the
 * client's ipaddr < server's ipaddr. Otherwise, close the accepted
 * socket and force a reconneect from smaller -> larger ip addr. The reason
 * we special case cp_index 0 is to allow the rds probe ping itself to itself
 * get through efficiently.
 */
static struct rds_tcp_connection *
rds_tcp_accept_one_path(struct rds_connection *conn, struct socket *sock)
{
        int sport, npaths, i_min, i_max, i;

        if (conn->c_with_sport_idx)
                /* cp->cp_index is encoded in lowest bits of source-port */
                sport = rds_tcp_get_peer_sport(sock);
        else
                sport = -1;

        npaths = max_t(int, 1, conn->c_npaths);

        if (sport >= 0) {
                i_min = sport % npaths;
                i_max = i_min;
        } else {
                i_min = 0;
                i_max = npaths - 1;
        }

        for (i = i_min; i <= i_max; i++) {
                struct rds_conn_path *cp = &conn->c_path[i];

                if (rds_conn_path_transition(cp, RDS_CONN_DOWN,
                                             RDS_CONN_CONNECTING))
                        return cp->cp_transport_data;
        }

        return NULL;
}

void rds_tcp_conn_slots_available(struct rds_connection *conn, bool fan_out)
{
        struct rds_tcp_connection *tc;
        struct rds_tcp_net *rtn;
        struct socket *sock;
        int sport, npaths;

        if (rds_destroy_pending(conn))
                return;

        tc = conn->c_path->cp_transport_data;
        rtn = tc->t_rtn;
        if (!rtn)
                return;

        sock = tc->t_sock;

        /* During fan-out, check that the connection we already
         * accepted in slot#0 carried the proper source port modulo.
         */
        if (fan_out && conn->c_with_sport_idx && sock &&
            rds_addr_cmp(&conn->c_laddr, &conn->c_faddr) > 0) {
                /* cp->cp_index is encoded in lowest bits of source-port */
                sport = rds_tcp_get_peer_sport(sock);
                npaths = max_t(int, 1, conn->c_npaths);
                if (sport >= 0 && sport % npaths != 0)
                        /* peer initiated with a non-#0 lane first */
                        rds_conn_path_drop(conn->c_path, 0);
        }

        /* As soon as a connection went down,
         * it is safe to schedule a "rds_tcp_accept_one"
         * attempt even if there are no connections pending:
         * Function "rds_tcp_accept_one" won't block
         * but simply return -EAGAIN in that case.
         *
         * Doing so is necessary to address the case where an
         * incoming connection on "rds_tcp_listen_sock" is ready
         * to be acccepted prior to a free slot being available:
         * the -ENOBUFS case in "rds_tcp_accept_one".
         */
        rds_tcp_accept_work(rtn);
}

int rds_tcp_accept_one(struct rds_tcp_net *rtn)
{
        struct socket *listen_sock = rtn->rds_tcp_listen_sock;
        struct socket *new_sock = NULL;
        struct rds_connection *conn;
        int ret;
        struct inet_sock *inet;
        struct rds_tcp_connection *rs_tcp = NULL;
        int conn_state;
        struct rds_conn_path *cp;
        struct sock *sk;
        struct in6_addr *my_addr, *peer_addr;
#if !IS_ENABLED(CONFIG_IPV6)
        struct in6_addr saddr, daddr;
#endif
        int dev_if = 0;

        if (!listen_sock) /* module unload or netns delete in progress */
                return -ENETUNREACH;

        mutex_lock(&rtn->rds_tcp_accept_lock);
        new_sock = rtn->rds_tcp_accepted_sock;
        rtn->rds_tcp_accepted_sock = NULL;

        if (!new_sock) {
                ret = kernel_accept(listen_sock, &new_sock, O_NONBLOCK);
                if (ret)
                        goto out;

                rds_tcp_keepalive(new_sock);
                if (!rds_tcp_tune(new_sock)) {
                        ret = -EINVAL;
                        goto out;
                }
        }

        inet = inet_sk(new_sock->sk);

#if IS_ENABLED(CONFIG_IPV6)
        my_addr = &new_sock->sk->sk_v6_rcv_saddr;
        peer_addr = &new_sock->sk->sk_v6_daddr;
#else
        ipv6_addr_set_v4mapped(inet->inet_saddr, &saddr);
        ipv6_addr_set_v4mapped(inet->inet_daddr, &daddr);
        my_addr = &saddr;
        peer_addr = &daddr;
#endif
        rdsdebug("accepted family %d tcp %pI6c:%u -> %pI6c:%u\n",
                 listen_sock->sk->sk_family,
                 my_addr, ntohs(inet->inet_sport),
                 peer_addr, ntohs(inet->inet_dport));

#if IS_ENABLED(CONFIG_IPV6)
        /* sk_bound_dev_if is not set if the peer address is not link local
         * address.  In this case, it happens that mcast_oif is set.  So
         * just use it.
         */
        if ((ipv6_addr_type(my_addr) & IPV6_ADDR_LINKLOCAL) &&
            !(ipv6_addr_type(peer_addr) & IPV6_ADDR_LINKLOCAL)) {
                struct ipv6_pinfo *inet6;

                inet6 = inet6_sk(new_sock->sk);
                dev_if = READ_ONCE(inet6->mcast_oif);
        } else {
                dev_if = new_sock->sk->sk_bound_dev_if;
        }
#endif

        if (!rds_tcp_laddr_check(sock_net(listen_sock->sk), peer_addr, dev_if)) {
                /* local address connection is only allowed via loopback */
                ret = -EOPNOTSUPP;
                goto out;
        }

        conn = rds_conn_create(sock_net(listen_sock->sk),
                               my_addr, peer_addr,
                               &rds_tcp_transport, 0, GFP_KERNEL, dev_if);

        if (IS_ERR(conn)) {
                ret = PTR_ERR(conn);
                goto out;
        }
        /* An incoming SYN request came in, and TCP just accepted it.
         *
         * If the client reboots, this conn will need to be cleaned up.
         * rds_tcp_state_change() will do that cleanup
         */
        if (rds_addr_cmp(&conn->c_faddr, &conn->c_laddr) < 0) {
                /* Try to obtain a free connection slot.
                 * If unsuccessful, we need to preserve "new_sock"
                 * that we just accepted, since its "sk_receive_queue"
                 * may contain messages already that have been acknowledged
                 * to and discarded by the sender.
                 * We must not throw those away!
                 */
                rs_tcp = rds_tcp_accept_one_path(conn, new_sock);
                if (!rs_tcp) {
                        /* It's okay to stash "new_sock", since
                         * "rds_tcp_conn_slots_available" triggers
                         * "rds_tcp_accept_one" again as soon as one of the
                         * connection slots becomes available again
                         */
                        rtn->rds_tcp_accepted_sock = new_sock;
                        new_sock = NULL;
                        ret = -ENOBUFS;
                        goto out;
                }
        } else {
                /* This connection request came from a peer with
                 * a larger address.
                 * Function "rds_tcp_state_change" makes sure
                 * that the connection doesn't transition
                 * to state "RDS_CONN_UP", and therefore
                 * we should not have received any messages
                 * on this socket yet.
                 * This is the only case where it's okay to
                 * not dequeue messages from "sk_receive_queue".
                 */
                if (conn->c_npaths <= 1)
                        rds_conn_path_connect_if_down(&conn->c_path[0]);
                rs_tcp = NULL;
                goto rst_nsk;
        }

        mutex_lock(&rs_tcp->t_conn_path_lock);
        cp = rs_tcp->t_cpath;
        conn_state = rds_conn_path_state(cp);
        WARN_ON(conn_state == RDS_CONN_UP);
        if (conn_state != RDS_CONN_CONNECTING && conn_state != RDS_CONN_ERROR) {
                rds_conn_path_drop(cp, 0);
                goto rst_nsk;
        }
        /* Save a local pointer to sk and hold a reference before setting
         * callbacks. Once callbacks are set, a concurrent
         * rds_tcp_conn_path_shutdown() may call sock_release(), which
         * sets new_sock->sk to NULL and drops a reference on sk.
         * The local pointer lets us safely access sk_state below even
         * if new_sock->sk has been nulled, and sock_hold() keeps sk
         * itself valid until we are done.
         */
        sk = new_sock->sk;
        sock_hold(sk);

        if (rs_tcp->t_sock) {
                /* Duelling SYN has been handled in rds_tcp_accept_one() */
                rds_tcp_reset_callbacks(new_sock, cp);
                /* rds_connect_path_complete() marks RDS_CONN_UP */
                rds_connect_path_complete(cp, RDS_CONN_RESETTING);
        } else {
                rds_tcp_set_callbacks(new_sock, cp);
                rds_connect_path_complete(cp, RDS_CONN_CONNECTING);
        }

        /* Since "rds_tcp_set_callbacks" happens this late
         * the connection may already have been closed without
         * "rds_tcp_state_change" doing its due diligence.
         *
         * If that's the case, we simply drop the path,
         * knowing that "rds_tcp_conn_path_shutdown" will
         * dequeue pending messages.
         */
        if (READ_ONCE(sk->sk_state) == TCP_CLOSE_WAIT ||
            READ_ONCE(sk->sk_state) == TCP_LAST_ACK ||
            READ_ONCE(sk->sk_state) == TCP_CLOSE)
                rds_conn_path_drop(cp, 0);
        else
                queue_delayed_work(cp->cp_wq, &cp->cp_recv_w, 0);

        sock_put(sk);

        new_sock = NULL;
        ret = 0;
        if (conn->c_npaths == 0)
                rds_send_ping(cp->cp_conn, cp->cp_index);
        goto out;
rst_nsk:
        /* reset the newly returned accept sock and bail.
         * It is safe to set linger on new_sock because the RDS connection
         * has not been brought up on new_sock, so no RDS-level data could
         * be pending on it. By setting linger, we achieve the side-effect
         * of avoiding TIME_WAIT state on new_sock.
         */
        sock_no_linger(new_sock->sk);
        kernel_sock_shutdown(new_sock, SHUT_RDWR);
        ret = 0;
out:
        if (rs_tcp)
                mutex_unlock(&rs_tcp->t_conn_path_lock);
        if (new_sock)
                sock_release(new_sock);

        mutex_unlock(&rtn->rds_tcp_accept_lock);

        return ret;
}

void rds_tcp_listen_data_ready(struct sock *sk)
{
        void (*ready)(struct sock *sk);

        trace_sk_data_ready(sk);
        rdsdebug("listen data ready sk %p\n", sk);

        read_lock_bh(&sk->sk_callback_lock);
        ready = sk->sk_user_data;
        if (!ready) { /* check for teardown race */
                ready = sk->sk_data_ready;
                goto out;
        }

        /*
         * ->sk_data_ready is also called for a newly established child socket
         * before it has been accepted and the accepter has set up their
         * data_ready.. we only want to queue listen work for our listening
         * socket
         *
         * (*ready)() may be null if we are racing with netns delete, and
         * the listen socket is being torn down.
         */
        if (sk->sk_state == TCP_LISTEN)
                rds_tcp_accept_work(net_generic(sock_net(sk), rds_tcp_netid));
        else
                ready = rds_tcp_listen_sock_def_readable(sock_net(sk));

out:
        read_unlock_bh(&sk->sk_callback_lock);
        if (ready)
                ready(sk);
}

struct socket *rds_tcp_listen_init(struct net *net, bool isv6)
{
        struct socket *sock = NULL;
        struct sockaddr_storage ss;
        struct sockaddr_in6 *sin6;
        struct sockaddr_in *sin;
        int addr_len;
        int ret;

        ret = sock_create_kern(net, isv6 ? PF_INET6 : PF_INET, SOCK_STREAM,
                               IPPROTO_TCP, &sock);
        if (ret < 0) {
                rdsdebug("could not create %s listener socket: %d\n",
                         isv6 ? "IPv6" : "IPv4", ret);
                goto out;
        }

        sock->sk->sk_reuse = SK_CAN_REUSE;
        tcp_sock_set_nodelay(sock->sk);

        write_lock_bh(&sock->sk->sk_callback_lock);
        sock->sk->sk_user_data = sock->sk->sk_data_ready;
        sock->sk->sk_data_ready = rds_tcp_listen_data_ready;
        write_unlock_bh(&sock->sk->sk_callback_lock);

        if (isv6) {
                sin6 = (struct sockaddr_in6 *)&ss;
                sin6->sin6_family = PF_INET6;
                sin6->sin6_addr = in6addr_any;
                sin6->sin6_port = htons(RDS_TCP_PORT);
                sin6->sin6_scope_id = 0;
                sin6->sin6_flowinfo = 0;
                addr_len = sizeof(*sin6);
        } else {
                sin = (struct sockaddr_in *)&ss;
                sin->sin_family = PF_INET;
                sin->sin_addr.s_addr = htonl(INADDR_ANY);
                sin->sin_port = htons(RDS_TCP_PORT);
                addr_len = sizeof(*sin);
        }

        ret = kernel_bind(sock, (struct sockaddr_unsized *)&ss, addr_len);
        if (ret < 0) {
                rdsdebug("could not bind %s listener socket: %d\n",
                         isv6 ? "IPv6" : "IPv4", ret);
                goto out;
        }

        ret = sock->ops->listen(sock, 64);
        if (ret < 0)
                goto out;

        return sock;
out:
        if (sock)
                sock_release(sock);
        return NULL;
}

void rds_tcp_listen_stop(struct socket *sock, struct work_struct *acceptor)
{
        struct sock *sk;

        if (!sock)
                return;

        sk = sock->sk;

        /* serialize with and prevent further callbacks */
        lock_sock(sk);
        write_lock_bh(&sk->sk_callback_lock);
        if (sk->sk_user_data) {
                sk->sk_data_ready = sk->sk_user_data;
                sk->sk_user_data = NULL;
        }
        write_unlock_bh(&sk->sk_callback_lock);
        release_sock(sk);

        /* wait for accepts to stop and close the socket */
        flush_workqueue(rds_wq);
        flush_work(acceptor);
        sock_release(sock);
}