/* RxRPC remote transport endpoint record management
 *
 * Copyright (C) 2007, 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 License
 * as published by the Free Software Foundation; either version
 * 2 of the License, 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/udp.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/slab.h>
#include <linux/hashtable.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/ip6_route.h>
#include "ar-internal.h"

/*
 * Hash a peer key.
 */
static unsigned long rxrpc_peer_hash_key(struct rxrpc_local *local,
                                         const struct sockaddr_rxrpc *srx)
{
        const u16 *p;
        unsigned int i, size;
        unsigned long hash_key;

        _enter("");

        hash_key = (unsigned long)local / __alignof__(*local);
        hash_key += srx->transport_type;
        hash_key += srx->transport_len;
        hash_key += srx->transport.family;

        switch (srx->transport.family) {
        case AF_INET:
                hash_key += (u16 __force)srx->transport.sin.sin_port;
                size = sizeof(srx->transport.sin.sin_addr);
                p = (u16 *)&srx->transport.sin.sin_addr;
                break;
#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                hash_key += (u16 __force)srx->transport.sin.sin_port;
                size = sizeof(srx->transport.sin6.sin6_addr);
                p = (u16 *)&srx->transport.sin6.sin6_addr;
                break;
#endif
        default:
                WARN(1, "AF_RXRPC: Unsupported transport address family\n");
                return 0;
        }

        /* Step through the peer address in 16-bit portions for speed */
        for (i = 0; i < size; i += sizeof(*p), p++)
                hash_key += *p;

        _leave(" 0x%lx", hash_key);
        return hash_key;
}

/*
 * Compare a peer to a key.  Return -ve, 0 or +ve to indicate less than, same
 * or greater than.
 *
 * Unfortunately, the primitives in linux/hashtable.h don't allow for sorted
 * buckets and mid-bucket insertion, so we don't make full use of this
 * information at this point.
 */
static long rxrpc_peer_cmp_key(const struct rxrpc_peer *peer,
                               struct rxrpc_local *local,
                               const struct sockaddr_rxrpc *srx,
                               unsigned long hash_key)
{
        long diff;

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

        switch (srx->transport.family) {
        case AF_INET:
                return ((u16 __force)peer->srx.transport.sin.sin_port -
                        (u16 __force)srx->transport.sin.sin_port) ?:
                        memcmp(&peer->srx.transport.sin.sin_addr,
                               &srx->transport.sin.sin_addr,
                               sizeof(struct in_addr));
#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                return ((u16 __force)peer->srx.transport.sin6.sin6_port -
                        (u16 __force)srx->transport.sin6.sin6_port) ?:
                        memcmp(&peer->srx.transport.sin6.sin6_addr,
                               &srx->transport.sin6.sin6_addr,
                               sizeof(struct in6_addr));
#endif
        default:
                BUG();
        }
}

/*
 * Look up a remote transport endpoint for the specified address using RCU.
 */
static struct rxrpc_peer *__rxrpc_lookup_peer_rcu(
        struct rxrpc_local *local,
        const struct sockaddr_rxrpc *srx,
        unsigned long hash_key)
{
        struct rxrpc_peer *peer;
        struct rxrpc_net *rxnet = local->rxnet;

        hash_for_each_possible_rcu(rxnet->peer_hash, peer, hash_link, hash_key) {
                if (rxrpc_peer_cmp_key(peer, local, srx, hash_key) == 0) {
                        if (atomic_read(&peer->usage) == 0)
                                return NULL;
                        return peer;
                }
        }

        return NULL;
}

/*
 * Look up a remote transport endpoint for the specified address using RCU.
 */
struct rxrpc_peer *rxrpc_lookup_peer_rcu(struct rxrpc_local *local,
                                         const struct sockaddr_rxrpc *srx)
{
        struct rxrpc_peer *peer;
        unsigned long hash_key = rxrpc_peer_hash_key(local, srx);

        peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
        if (peer) {
                _net("PEER %d {%pISp}", peer->debug_id, &peer->srx.transport);
                _leave(" = %p {u=%d}", peer, atomic_read(&peer->usage));
        }
        return peer;
}

/*
 * assess the MTU size for the network interface through which this peer is
 * reached
 */
static void rxrpc_assess_MTU_size(struct rxrpc_peer *peer)
{
        struct dst_entry *dst;
        struct rtable *rt;
        struct flowi fl;
        struct flowi4 *fl4 = &fl.u.ip4;
#ifdef CONFIG_AF_RXRPC_IPV6
        struct flowi6 *fl6 = &fl.u.ip6;
#endif

        peer->if_mtu = 1500;

        memset(&fl, 0, sizeof(fl));
        switch (peer->srx.transport.family) {
        case AF_INET:
                rt = ip_route_output_ports(
                        &init_net, fl4, NULL,
                        peer->srx.transport.sin.sin_addr.s_addr, 0,
                        htons(7000), htons(7001), IPPROTO_UDP, 0, 0);
                if (IS_ERR(rt)) {
                        _leave(" [route err %ld]", PTR_ERR(rt));
                        return;
                }
                dst = &rt->dst;
                break;

#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                fl6->flowi6_iif = LOOPBACK_IFINDEX;
                fl6->flowi6_scope = RT_SCOPE_UNIVERSE;
                fl6->flowi6_proto = IPPROTO_UDP;
                memcpy(&fl6->daddr, &peer->srx.transport.sin6.sin6_addr,
                       sizeof(struct in6_addr));
                fl6->fl6_dport = htons(7001);
                fl6->fl6_sport = htons(7000);
                dst = ip6_route_output(&init_net, NULL, fl6);
                if (dst->error) {
                        _leave(" [route err %d]", dst->error);
                        return;
                }
                break;
#endif

        default:
                BUG();
        }

        peer->if_mtu = dst_mtu(dst);
        dst_release(dst);

        _leave(" [if_mtu %u]", peer->if_mtu);
}

/*
 * Allocate a peer.
 */
struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp)
{
        struct rxrpc_peer *peer;

        _enter("");

        peer = kzalloc(sizeof(struct rxrpc_peer), gfp);
        if (peer) {
                atomic_set(&peer->usage, 1);
                peer->local = local;
                INIT_HLIST_HEAD(&peer->error_targets);
                INIT_WORK(&peer->error_distributor,
                          &rxrpc_peer_error_distributor);
                peer->service_conns = RB_ROOT;
                seqlock_init(&peer->service_conn_lock);
                spin_lock_init(&peer->lock);
                peer->debug_id = atomic_inc_return(&rxrpc_debug_id);

                if (RXRPC_TX_SMSS > 2190)
                        peer->cong_cwnd = 2;
                else if (RXRPC_TX_SMSS > 1095)
                        peer->cong_cwnd = 3;
                else
                        peer->cong_cwnd = 4;
        }

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

/*
 * Initialise peer record.
 */
static void rxrpc_init_peer(struct rxrpc_peer *peer, unsigned long hash_key)
{
        peer->hash_key = hash_key;
        rxrpc_assess_MTU_size(peer);
        peer->mtu = peer->if_mtu;
        peer->rtt_last_req = ktime_get_real();

        switch (peer->srx.transport.family) {
        case AF_INET:
                peer->hdrsize = sizeof(struct iphdr);
                break;
#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                peer->hdrsize = sizeof(struct ipv6hdr);
                break;
#endif
        default:
                BUG();
        }

        switch (peer->srx.transport_type) {
        case SOCK_DGRAM:
                peer->hdrsize += sizeof(struct udphdr);
                break;
        default:
                BUG();
        }

        peer->hdrsize += sizeof(struct rxrpc_wire_header);
        peer->maxdata = peer->mtu - peer->hdrsize;
}

/*
 * Set up a new peer.
 */
static struct rxrpc_peer *rxrpc_create_peer(struct rxrpc_local *local,
                                            struct sockaddr_rxrpc *srx,
                                            unsigned long hash_key,
                                            gfp_t gfp)
{
        struct rxrpc_peer *peer;

        _enter("");

        peer = rxrpc_alloc_peer(local, gfp);
        if (peer) {
                memcpy(&peer->srx, srx, sizeof(*srx));
                rxrpc_init_peer(peer, hash_key);
        }

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

/*
 * Set up a new incoming peer.  The address is prestored in the preallocated
 * peer.
 */
struct rxrpc_peer *rxrpc_lookup_incoming_peer(struct rxrpc_local *local,
                                              struct rxrpc_peer *prealloc)
{
        struct rxrpc_peer *peer;
        struct rxrpc_net *rxnet = local->rxnet;
        unsigned long hash_key;

        hash_key = rxrpc_peer_hash_key(local, &prealloc->srx);
        prealloc->local = local;
        rxrpc_init_peer(prealloc, hash_key);

        spin_lock(&rxnet->peer_hash_lock);

        /* Need to check that we aren't racing with someone else */
        peer = __rxrpc_lookup_peer_rcu(local, &prealloc->srx, hash_key);
        if (peer && !rxrpc_get_peer_maybe(peer))
                peer = NULL;
        if (!peer) {
                peer = prealloc;
                hash_add_rcu(rxnet->peer_hash, &peer->hash_link, hash_key);
                hlist_add_head(&peer->keepalive_link, &rxnet->peer_keepalive_new);
        }

        spin_unlock(&rxnet->peer_hash_lock);
        return peer;
}

/*
 * obtain a remote transport endpoint for the specified address
 */
struct rxrpc_peer *rxrpc_lookup_peer(struct rxrpc_local *local,
                                     struct sockaddr_rxrpc *srx, gfp_t gfp)
{
        struct rxrpc_peer *peer, *candidate;
        struct rxrpc_net *rxnet = local->rxnet;
        unsigned long hash_key = rxrpc_peer_hash_key(local, srx);

        _enter("{%pISp}", &srx->transport);

        /* search the peer list first */
        rcu_read_lock();
        peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
        if (peer && !rxrpc_get_peer_maybe(peer))
                peer = NULL;
        rcu_read_unlock();

        if (!peer) {
                /* The peer is not yet present in hash - create a candidate
                 * for a new record and then redo the search.
                 */
                candidate = rxrpc_create_peer(local, srx, hash_key, gfp);
                if (!candidate) {
                        _leave(" = NULL [nomem]");
                        return NULL;
                }

                spin_lock_bh(&rxnet->peer_hash_lock);

                /* Need to check that we aren't racing with someone else */
                peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
                if (peer && !rxrpc_get_peer_maybe(peer))
                        peer = NULL;
                if (!peer) {
                        hash_add_rcu(rxnet->peer_hash,
                                     &candidate->hash_link, hash_key);
                        hlist_add_head(&candidate->keepalive_link,
                                       &rxnet->peer_keepalive_new);
                }

                spin_unlock_bh(&rxnet->peer_hash_lock);

                if (peer)
                        kfree(candidate);
                else
                        peer = candidate;
        }

        _net("PEER %d {%pISp}", peer->debug_id, &peer->srx.transport);

        _leave(" = %p {u=%d}", peer, atomic_read(&peer->usage));
        return peer;
}

/*
 * Get a ref on a peer record.
 */
struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *peer)
{
        const void *here = __builtin_return_address(0);
        int n;

        n = atomic_inc_return(&peer->usage);
        trace_rxrpc_peer(peer, rxrpc_peer_got, n, here);
        return peer;
}

/*
 * Get a ref on a peer record unless its usage has already reached 0.
 */
struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *peer)
{
        const void *here = __builtin_return_address(0);

        if (peer) {
                int n = __atomic_add_unless(&peer->usage, 1, 0);
                if (n > 0)
                        trace_rxrpc_peer(peer, rxrpc_peer_got, n + 1, here);
                else
                        peer = NULL;
        }
        return peer;
}

/*
 * Queue a peer record.  This passes the caller's ref to the workqueue.
 */
void __rxrpc_queue_peer_error(struct rxrpc_peer *peer)
{
        const void *here = __builtin_return_address(0);
        int n;

        n = atomic_read(&peer->usage);
        if (rxrpc_queue_work(&peer->error_distributor))
                trace_rxrpc_peer(peer, rxrpc_peer_queued_error, n, here);
        else
                rxrpc_put_peer(peer);
}

/*
 * Discard a peer record.
 */
static void __rxrpc_put_peer(struct rxrpc_peer *peer)
{
        struct rxrpc_net *rxnet = peer->local->rxnet;

        ASSERT(hlist_empty(&peer->error_targets));

        spin_lock_bh(&rxnet->peer_hash_lock);
        hash_del_rcu(&peer->hash_link);
        hlist_del_init(&peer->keepalive_link);
        spin_unlock_bh(&rxnet->peer_hash_lock);

        kfree_rcu(peer, rcu);
}

/*
 * Drop a ref on a peer record.
 */
void rxrpc_put_peer(struct rxrpc_peer *peer)
{
        const void *here = __builtin_return_address(0);
        int n;

        if (peer) {
                n = atomic_dec_return(&peer->usage);
                trace_rxrpc_peer(peer, rxrpc_peer_put, n, here);
                if (n == 0)
                        __rxrpc_put_peer(peer);
        }
}

/*
 * Make sure all peer records have been discarded.
 */
void rxrpc_destroy_all_peers(struct rxrpc_net *rxnet)
{
        struct rxrpc_peer *peer;
        int i;

        for (i = 0; i < HASH_SIZE(rxnet->peer_hash); i++) {
                if (hlist_empty(&rxnet->peer_hash[i]))
                        continue;

                hlist_for_each_entry(peer, &rxnet->peer_hash[i], hash_link) {
                        pr_err("Leaked peer %u {%u} %pISp\n",
                               peer->debug_id,
                               atomic_read(&peer->usage),
                               &peer->srx.transport);
                }
        }
}

/**
 * rxrpc_kernel_get_peer - Get the peer address of a call
 * @sock: The socket on which the call is in progress.
 * @call: The call to query
 * @_srx: Where to place the result
 *
 * Get the address of the remote peer in a call.
 */
void rxrpc_kernel_get_peer(struct socket *sock, struct rxrpc_call *call,
                           struct sockaddr_rxrpc *_srx)
{
        *_srx = call->peer->srx;
}
EXPORT_SYMBOL(rxrpc_kernel_get_peer);

/**
 * rxrpc_kernel_get_rtt - Get a call's peer RTT
 * @sock: The socket on which the call is in progress.
 * @call: The call to query
 *
 * Get the call's peer RTT.
 */
u64 rxrpc_kernel_get_rtt(struct socket *sock, struct rxrpc_call *call)
{
        return call->peer->rtt;
}
EXPORT_SYMBOL(rxrpc_kernel_get_rtt);