/* Local endpoint object management
 *
 * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/udp.h>
#include <linux/ip.h>
#include <linux/hashtable.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"

static void rxrpc_local_processor(struct work_struct *);
static void rxrpc_local_rcu(struct rcu_head *);

/*
 * Compare a local to an address.  Return -ve, 0 or +ve to indicate less than,
 * same or greater than.
 *
 * We explicitly don't compare the RxRPC service ID as we want to reject
 * conflicting uses by differing services.  Further, we don't want to share
 * addresses with different options (IPv6), so we don't compare those bits
 * either.
 */
static long rxrpc_local_cmp_key(const struct rxrpc_local *local,
                                const struct sockaddr_rxrpc *srx)
{
        long diff;

        diff = ((local->srx.transport_type - srx->transport_type) ?:
                (local->srx.transport_len - srx->transport_len) ?:
                (local->srx.transport.family - srx->transport.family));
        if (diff != 0)
                return diff;

        switch (srx->transport.family) {
        case AF_INET:
                /* If the choice of UDP port is left up to the transport, then
                 * the endpoint record doesn't match.
                 */
                return ((u16 __force)local->srx.transport.sin.sin_port -
                        (u16 __force)srx->transport.sin.sin_port) ?:
                        memcmp(&local->srx.transport.sin.sin_addr,
                               &srx->transport.sin.sin_addr,
                               sizeof(struct in_addr));
#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                /* If the choice of UDP6 port is left up to the transport, then
                 * the endpoint record doesn't match.
                 */
                return ((u16 __force)local->srx.transport.sin6.sin6_port -
                        (u16 __force)srx->transport.sin6.sin6_port) ?:
                        memcmp(&local->srx.transport.sin6.sin6_addr,
                               &srx->transport.sin6.sin6_addr,
                               sizeof(struct in6_addr));
#endif
        default:
                BUG();
        }
}

/*
 * Allocate a new local endpoint.
 */
static struct rxrpc_local *rxrpc_alloc_local(struct rxrpc_net *rxnet,
                                             const struct sockaddr_rxrpc *srx)
{
        struct rxrpc_local *local;

        local = kzalloc(sizeof(struct rxrpc_local), GFP_KERNEL);
        if (local) {
                atomic_set(&local->usage, 1);
                local->rxnet = rxnet;
                INIT_LIST_HEAD(&local->link);
                INIT_WORK(&local->processor, rxrpc_local_processor);
                init_rwsem(&local->defrag_sem);
                skb_queue_head_init(&local->reject_queue);
                skb_queue_head_init(&local->event_queue);
                local->client_conns = RB_ROOT;
                spin_lock_init(&local->client_conns_lock);
                spin_lock_init(&local->lock);
                rwlock_init(&local->services_lock);
                local->debug_id = atomic_inc_return(&rxrpc_debug_id);
                memcpy(&local->srx, srx, sizeof(*srx));
                local->srx.srx_service = 0;
                trace_rxrpc_local(local, rxrpc_local_new, 1, NULL);
        }

        _leave(" = %p", local);
        return local;
}

/*
 * create the local socket
 * - must be called with rxrpc_local_mutex locked
 */
static int rxrpc_open_socket(struct rxrpc_local *local, struct net *net)
{
        struct sock *sock;
        int ret, opt;

        _enter("%p{%d,%d}",
               local, local->srx.transport_type, local->srx.transport.family);

        /* create a socket to represent the local endpoint */
        ret = sock_create_kern(net, local->srx.transport.family,
                               local->srx.transport_type, 0, &local->socket);
        if (ret < 0) {
                _leave(" = %d [socket]", ret);
                return ret;
        }

        /* if a local address was supplied then bind it */
        if (local->srx.transport_len > sizeof(sa_family_t)) {
                _debug("bind");
                ret = kernel_bind(local->socket,
                                  (struct sockaddr *)&local->srx.transport,
                                  local->srx.transport_len);
                if (ret < 0) {
                        _debug("bind failed %d", ret);
                        goto error;
                }
        }

        switch (local->srx.transport.family) {
        case AF_INET:
                /* we want to receive ICMP errors */
                opt = 1;
                ret = kernel_setsockopt(local->socket, SOL_IP, IP_RECVERR,
                                        (char *) &opt, sizeof(opt));
                if (ret < 0) {
                        _debug("setsockopt failed");
                        goto error;
                }

                /* we want to set the don't fragment bit */
                opt = IP_PMTUDISC_DO;
                ret = kernel_setsockopt(local->socket, SOL_IP, IP_MTU_DISCOVER,
                                        (char *) &opt, sizeof(opt));
                if (ret < 0) {
                        _debug("setsockopt failed");
                        goto error;
                }
                break;

        case AF_INET6:
                /* we want to receive ICMP errors */
                opt = 1;
                ret = kernel_setsockopt(local->socket, SOL_IPV6, IPV6_RECVERR,
                                        (char *) &opt, sizeof(opt));
                if (ret < 0) {
                        _debug("setsockopt failed");
                        goto error;
                }

                /* we want to set the don't fragment bit */
                opt = IPV6_PMTUDISC_DO;
                ret = kernel_setsockopt(local->socket, SOL_IPV6, IPV6_MTU_DISCOVER,
                                        (char *) &opt, sizeof(opt));
                if (ret < 0) {
                        _debug("setsockopt failed");
                        goto error;
                }
                break;

        default:
                BUG();
        }

        /* set the socket up */
        sock = local->socket->sk;
        sock->sk_user_data      = local;
        sock->sk_data_ready     = rxrpc_data_ready;
        sock->sk_error_report   = rxrpc_error_report;
        _leave(" = 0");
        return 0;

error:
        kernel_sock_shutdown(local->socket, SHUT_RDWR);
        local->socket->sk->sk_user_data = NULL;
        sock_release(local->socket);
        local->socket = NULL;

        _leave(" = %d", ret);
        return ret;
}

/*
 * Look up or create a new local endpoint using the specified local address.
 */
struct rxrpc_local *rxrpc_lookup_local(struct net *net,
                                       const struct sockaddr_rxrpc *srx)
{
        struct rxrpc_local *local;
        struct rxrpc_net *rxnet = rxrpc_net(net);
        struct list_head *cursor;
        const char *age;
        long diff;
        int ret;

        _enter("{%d,%d,%pISp}",
               srx->transport_type, srx->transport.family, &srx->transport);

        mutex_lock(&rxnet->local_mutex);

        for (cursor = rxnet->local_endpoints.next;
             cursor != &rxnet->local_endpoints;
             cursor = cursor->next) {
                local = list_entry(cursor, struct rxrpc_local, link);

                diff = rxrpc_local_cmp_key(local, srx);
                if (diff < 0)
                        continue;
                if (diff > 0)
                        break;

                /* Services aren't allowed to share transport sockets, so
                 * reject that here.  It is possible that the object is dying -
                 * but it may also still have the local transport address that
                 * we want bound.
                 */
                if (srx->srx_service) {
                        local = NULL;
                        goto addr_in_use;
                }

                /* Found a match.  We replace a dying object.  Attempting to
                 * bind the transport socket may still fail if we're attempting
                 * to use a local address that the dying object is still using.
                 */
                if (!rxrpc_get_local_maybe(local)) {
                        cursor = cursor->next;
                        list_del_init(&local->link);
                        break;
                }

                age = "old";
                goto found;
        }

        local = rxrpc_alloc_local(rxnet, srx);
        if (!local)
                goto nomem;

        ret = rxrpc_open_socket(local, net);
        if (ret < 0)
                goto sock_error;

        list_add_tail(&local->link, cursor);
        age = "new";

found:
        mutex_unlock(&rxnet->local_mutex);

        _net("LOCAL %s %d {%pISp}",
             age, local->debug_id, &local->srx.transport);

        _leave(" = %p", local);
        return local;

nomem:
        ret = -ENOMEM;
sock_error:
        mutex_unlock(&rxnet->local_mutex);
        kfree(local);
        _leave(" = %d", ret);
        return ERR_PTR(ret);

addr_in_use:
        mutex_unlock(&rxnet->local_mutex);
        _leave(" = -EADDRINUSE");
        return ERR_PTR(-EADDRINUSE);
}

/*
 * Get a ref on a local endpoint.
 */
struct rxrpc_local *rxrpc_get_local(struct rxrpc_local *local)
{
        const void *here = __builtin_return_address(0);
        int n;

        n = atomic_inc_return(&local->usage);
        trace_rxrpc_local(local, rxrpc_local_got, n, here);
        return local;
}

/*
 * Get a ref on a local endpoint unless its usage has already reached 0.
 */
struct rxrpc_local *rxrpc_get_local_maybe(struct rxrpc_local *local)
{
        const void *here = __builtin_return_address(0);

        if (local) {
                int n = __atomic_add_unless(&local->usage, 1, 0);
                if (n > 0)
                        trace_rxrpc_local(local, rxrpc_local_got, n + 1, here);
                else
                        local = NULL;
        }
        return local;
}

/*
 * Queue a local endpoint.
 */
void rxrpc_queue_local(struct rxrpc_local *local)
{
        const void *here = __builtin_return_address(0);

        if (rxrpc_queue_work(&local->processor))
                trace_rxrpc_local(local, rxrpc_local_queued,
                                  atomic_read(&local->usage), here);
}

/*
 * A local endpoint reached its end of life.
 */
static void __rxrpc_put_local(struct rxrpc_local *local)
{
        _enter("%d", local->debug_id);
        rxrpc_queue_work(&local->processor);
}

/*
 * Drop a ref on a local endpoint.
 */
void rxrpc_put_local(struct rxrpc_local *local)
{
        const void *here = __builtin_return_address(0);
        int n;

        if (local) {
                n = atomic_dec_return(&local->usage);
                trace_rxrpc_local(local, rxrpc_local_put, n, here);

                if (n == 0)
                        __rxrpc_put_local(local);
        }
}

/*
 * Destroy a local endpoint's socket and then hand the record to RCU to dispose
 * of.
 *
 * Closing the socket cannot be done from bottom half context or RCU callback
 * context because it might sleep.
 */
static void rxrpc_local_destroyer(struct rxrpc_local *local)
{
        struct socket *socket = local->socket;
        struct rxrpc_net *rxnet = local->rxnet;

        _enter("%d", local->debug_id);

        /* We can get a race between an incoming call packet queueing the
         * processor again and the work processor starting the destruction
         * process which will shut down the UDP socket.
         */
        if (local->dead) {
                _leave(" [already dead]");
                return;
        }
        local->dead = true;

        mutex_lock(&rxnet->local_mutex);
        list_del_init(&local->link);
        mutex_unlock(&rxnet->local_mutex);

        ASSERT(RB_EMPTY_ROOT(&local->client_conns));
        ASSERT(!local->service);

        if (socket) {
                local->socket = NULL;
                kernel_sock_shutdown(socket, SHUT_RDWR);
                socket->sk->sk_user_data = NULL;
                sock_release(socket);
        }

        /* At this point, there should be no more packets coming in to the
         * local endpoint.
         */
        rxrpc_purge_queue(&local->reject_queue);
        rxrpc_purge_queue(&local->event_queue);

        _debug("rcu local %d", local->debug_id);
        call_rcu(&local->rcu, rxrpc_local_rcu);
}

/*
 * Process events on an endpoint
 */
static void rxrpc_local_processor(struct work_struct *work)
{
        struct rxrpc_local *local =
                container_of(work, struct rxrpc_local, processor);
        bool again;

        trace_rxrpc_local(local, rxrpc_local_processing,
                          atomic_read(&local->usage), NULL);

        do {
                again = false;
                if (atomic_read(&local->usage) == 0)
                        return rxrpc_local_destroyer(local);

                if (!skb_queue_empty(&local->reject_queue)) {
                        rxrpc_reject_packets(local);
                        again = true;
                }

                if (!skb_queue_empty(&local->event_queue)) {
                        rxrpc_process_local_events(local);
                        again = true;
                }
        } while (again);
}

/*
 * Destroy a local endpoint after the RCU grace period expires.
 */
static void rxrpc_local_rcu(struct rcu_head *rcu)
{
        struct rxrpc_local *local = container_of(rcu, struct rxrpc_local, rcu);

        _enter("%d", local->debug_id);

        ASSERT(!work_pending(&local->processor));

        _net("DESTROY LOCAL %d", local->debug_id);
        kfree(local);
        _leave("");
}

/*
 * Verify the local endpoint list is empty by this point.
 */
void rxrpc_destroy_all_locals(struct rxrpc_net *rxnet)
{
        struct rxrpc_local *local;

        _enter("");

        flush_workqueue(rxrpc_workqueue);

        if (!list_empty(&rxnet->local_endpoints)) {
                mutex_lock(&rxnet->local_mutex);
                list_for_each_entry(local, &rxnet->local_endpoints, link) {
                        pr_err("AF_RXRPC: Leaked local %p {%d}\n",
                               local, atomic_read(&local->usage));
                }
                mutex_unlock(&rxnet->local_mutex);
                BUG();
        }
}