/* Peer event handling, typically ICMP messages.
 *
 * Copyright (C) 2007 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.
 */

#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/errqueue.h>
#include <linux/udp.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/icmp.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <net/ip.h>
#include "ar-internal.h"

static void rxrpc_store_error(struct rxrpc_peer *, struct sock_exterr_skb *);

/*
 * Find the peer associated with an ICMP packet.
 */
static struct rxrpc_peer *rxrpc_lookup_peer_icmp_rcu(struct rxrpc_local *local,
                                                     const struct sk_buff *skb,
                                                     struct sockaddr_rxrpc *srx)
{
        struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);

        _enter("");

        memset(srx, 0, sizeof(*srx));
        srx->transport_type = local->srx.transport_type;
        srx->transport_len = local->srx.transport_len;
        srx->transport.family = local->srx.transport.family;

        /* Can we see an ICMP4 packet on an ICMP6 listening socket?  and vice
         * versa?
         */
        switch (srx->transport.family) {
        case AF_INET:
                srx->transport.sin.sin_port = serr->port;
                switch (serr->ee.ee_origin) {
                case SO_EE_ORIGIN_ICMP:
                        _net("Rx ICMP");
                        memcpy(&srx->transport.sin.sin_addr,
                               skb_network_header(skb) + serr->addr_offset,
                               sizeof(struct in_addr));
                        break;
                case SO_EE_ORIGIN_ICMP6:
                        _net("Rx ICMP6 on v4 sock");
                        memcpy(&srx->transport.sin.sin_addr,
                               skb_network_header(skb) + serr->addr_offset + 12,
                               sizeof(struct in_addr));
                        break;
                default:
                        memcpy(&srx->transport.sin.sin_addr, &ip_hdr(skb)->saddr,
                               sizeof(struct in_addr));
                        break;
                }
                break;

#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                srx->transport.sin6.sin6_port = serr->port;
                switch (serr->ee.ee_origin) {
                case SO_EE_ORIGIN_ICMP6:
                        _net("Rx ICMP6");
                        memcpy(&srx->transport.sin6.sin6_addr,
                               skb_network_header(skb) + serr->addr_offset,
                               sizeof(struct in6_addr));
                        break;
                case SO_EE_ORIGIN_ICMP:
                        _net("Rx ICMP on v6 sock");
                        srx->transport.sin6.sin6_addr.s6_addr32[0] = 0;
                        srx->transport.sin6.sin6_addr.s6_addr32[1] = 0;
                        srx->transport.sin6.sin6_addr.s6_addr32[2] = htonl(0xffff);
                        memcpy(srx->transport.sin6.sin6_addr.s6_addr + 12,
                               skb_network_header(skb) + serr->addr_offset,
                               sizeof(struct in_addr));
                        break;
                default:
                        memcpy(&srx->transport.sin6.sin6_addr,
                               &ipv6_hdr(skb)->saddr,
                               sizeof(struct in6_addr));
                        break;
                }
                break;
#endif

        default:
                BUG();
        }

        return rxrpc_lookup_peer_rcu(local, srx);
}

/*
 * Handle an MTU/fragmentation problem.
 */
static void rxrpc_adjust_mtu(struct rxrpc_peer *peer, struct sock_exterr_skb *serr)
{
        u32 mtu = serr->ee.ee_info;

        _net("Rx ICMP Fragmentation Needed (%d)", mtu);

        /* wind down the local interface MTU */
        if (mtu > 0 && peer->if_mtu == 65535 && mtu < peer->if_mtu) {
                peer->if_mtu = mtu;
                _net("I/F MTU %u", mtu);
        }

        if (mtu == 0) {
                /* they didn't give us a size, estimate one */
                mtu = peer->if_mtu;
                if (mtu > 1500) {
                        mtu >>= 1;
                        if (mtu < 1500)
                                mtu = 1500;
                } else {
                        mtu -= 100;
                        if (mtu < peer->hdrsize)
                                mtu = peer->hdrsize + 4;
                }
        }

        if (mtu < peer->mtu) {
                spin_lock_bh(&peer->lock);
                peer->mtu = mtu;
                peer->maxdata = peer->mtu - peer->hdrsize;
                spin_unlock_bh(&peer->lock);
                _net("Net MTU %u (maxdata %u)",
                     peer->mtu, peer->maxdata);
        }
}

/*
 * Handle an error received on the local endpoint.
 */
void rxrpc_error_report(struct sock *sk)
{
        struct sock_exterr_skb *serr;
        struct sockaddr_rxrpc srx;
        struct rxrpc_local *local = sk->sk_user_data;
        struct rxrpc_peer *peer;
        struct sk_buff *skb;

        _enter("%p{%d}", sk, local->debug_id);

        skb = sock_dequeue_err_skb(sk);
        if (!skb) {
                _leave("UDP socket errqueue empty");
                return;
        }
        rxrpc_new_skb(skb, rxrpc_skb_rx_received);
        serr = SKB_EXT_ERR(skb);
        if (!skb->len && serr->ee.ee_origin == SO_EE_ORIGIN_TIMESTAMPING) {
                _leave("UDP empty message");
                rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
                return;
        }

        rcu_read_lock();
        peer = rxrpc_lookup_peer_icmp_rcu(local, skb, &srx);
        if (peer && !rxrpc_get_peer_maybe(peer))
                peer = NULL;
        if (!peer) {
                rcu_read_unlock();
                rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
                _leave(" [no peer]");
                return;
        }

        trace_rxrpc_rx_icmp(peer, &serr->ee, &srx);

        if ((serr->ee.ee_origin == SO_EE_ORIGIN_ICMP &&
             serr->ee.ee_type == ICMP_DEST_UNREACH &&
             serr->ee.ee_code == ICMP_FRAG_NEEDED)) {
                rxrpc_adjust_mtu(peer, serr);
                rcu_read_unlock();
                rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
                rxrpc_put_peer(peer);
                _leave(" [MTU update]");
                return;
        }

        rxrpc_store_error(peer, serr);
        rcu_read_unlock();
        rxrpc_free_skb(skb, rxrpc_skb_rx_freed);

        /* The ref we obtained is passed off to the work item */
        __rxrpc_queue_peer_error(peer);
        _leave("");
}

/*
 * Map an error report to error codes on the peer record.
 */
static void rxrpc_store_error(struct rxrpc_peer *peer,
                              struct sock_exterr_skb *serr)
{
        struct sock_extended_err *ee;
        int err;

        _enter("");

        ee = &serr->ee;

        err = ee->ee_errno;

        switch (ee->ee_origin) {
        case SO_EE_ORIGIN_ICMP:
                switch (ee->ee_type) {
                case ICMP_DEST_UNREACH:
                        switch (ee->ee_code) {
                        case ICMP_NET_UNREACH:
                                _net("Rx Received ICMP Network Unreachable");
                                break;
                        case ICMP_HOST_UNREACH:
                                _net("Rx Received ICMP Host Unreachable");
                                break;
                        case ICMP_PORT_UNREACH:
                                _net("Rx Received ICMP Port Unreachable");
                                break;
                        case ICMP_NET_UNKNOWN:
                                _net("Rx Received ICMP Unknown Network");
                                break;
                        case ICMP_HOST_UNKNOWN:
                                _net("Rx Received ICMP Unknown Host");
                                break;
                        default:
                                _net("Rx Received ICMP DestUnreach code=%u",
                                     ee->ee_code);
                                break;
                        }
                        break;

                case ICMP_TIME_EXCEEDED:
                        _net("Rx Received ICMP TTL Exceeded");
                        break;

                default:
                        _proto("Rx Received ICMP error { type=%u code=%u }",
                               ee->ee_type, ee->ee_code);
                        break;
                }
                break;

        case SO_EE_ORIGIN_NONE:
        case SO_EE_ORIGIN_LOCAL:
                _proto("Rx Received local error { error=%d }", err);
                err += RXRPC_LOCAL_ERROR_OFFSET;
                break;

        case SO_EE_ORIGIN_ICMP6:
        default:
                _proto("Rx Received error report { orig=%u }", ee->ee_origin);
                break;
        }

        peer->error_report = err;
}

/*
 * Distribute an error that occurred on a peer
 */
void rxrpc_peer_error_distributor(struct work_struct *work)
{
        struct rxrpc_peer *peer =
                container_of(work, struct rxrpc_peer, error_distributor);
        struct rxrpc_call *call;
        enum rxrpc_call_completion compl;
        int error;

        _enter("");

        error = READ_ONCE(peer->error_report);
        if (error < RXRPC_LOCAL_ERROR_OFFSET) {
                compl = RXRPC_CALL_NETWORK_ERROR;
        } else {
                compl = RXRPC_CALL_LOCAL_ERROR;
                error -= RXRPC_LOCAL_ERROR_OFFSET;
        }

        _debug("ISSUE ERROR %s %d", rxrpc_call_completions[compl], error);

        spin_lock_bh(&peer->lock);

        while (!hlist_empty(&peer->error_targets)) {
                call = hlist_entry(peer->error_targets.first,
                                   struct rxrpc_call, error_link);
                hlist_del_init(&call->error_link);
                rxrpc_see_call(call);

                if (rxrpc_set_call_completion(call, compl, 0, -error))
                        rxrpc_notify_socket(call);
        }

        spin_unlock_bh(&peer->lock);

        rxrpc_put_peer(peer);
        _leave("");
}

/*
 * Add RTT information to cache.  This is called in softirq mode and has
 * exclusive access to the peer RTT data.
 */
void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
                        rxrpc_serial_t send_serial, rxrpc_serial_t resp_serial,
                        ktime_t send_time, ktime_t resp_time)
{
        struct rxrpc_peer *peer = call->peer;
        s64 rtt;
        u64 sum = peer->rtt_sum, avg;
        u8 cursor = peer->rtt_cursor, usage = peer->rtt_usage;

        rtt = ktime_to_ns(ktime_sub(resp_time, send_time));
        if (rtt < 0)
                return;

        /* Replace the oldest datum in the RTT buffer */
        sum -= peer->rtt_cache[cursor];
        sum += rtt;
        peer->rtt_cache[cursor] = rtt;
        peer->rtt_cursor = (cursor + 1) & (RXRPC_RTT_CACHE_SIZE - 1);
        peer->rtt_sum = sum;
        if (usage < RXRPC_RTT_CACHE_SIZE) {
                usage++;
                peer->rtt_usage = usage;
        }

        /* Now recalculate the average */
        if (usage == RXRPC_RTT_CACHE_SIZE) {
                avg = sum / RXRPC_RTT_CACHE_SIZE;
        } else {
                avg = sum;
                do_div(avg, usage);
        }

        peer->rtt = avg;
        trace_rxrpc_rtt_rx(call, why, send_serial, resp_serial, rtt,
                           usage, avg);
}

/*
 * Perform keep-alive pings with VERSION packets to keep any NAT alive.
 */
void rxrpc_peer_keepalive_worker(struct work_struct *work)
{
        struct rxrpc_net *rxnet =
                container_of(work, struct rxrpc_net, peer_keepalive_work);
        struct rxrpc_peer *peer;
        unsigned long delay;
        ktime_t base, now = ktime_get_real();
        s64 diff;
        u8 cursor, slot;

        base = rxnet->peer_keepalive_base;
        cursor = rxnet->peer_keepalive_cursor;

        _enter("%u,%lld", cursor, ktime_sub(now, base));

next_bucket:
        diff = ktime_to_ns(ktime_sub(now, base));
        if (diff < 0)
                goto resched;

        _debug("at %u", cursor);
        spin_lock_bh(&rxnet->peer_hash_lock);
next_peer:
        if (!rxnet->live) {
                spin_unlock_bh(&rxnet->peer_hash_lock);
                goto out;
        }

        /* Everything in the bucket at the cursor is processed this second; the
         * bucket at cursor + 1 goes now + 1s and so on...
         */
        if (hlist_empty(&rxnet->peer_keepalive[cursor])) {
                if (hlist_empty(&rxnet->peer_keepalive_new)) {
                        spin_unlock_bh(&rxnet->peer_hash_lock);
                        goto emptied_bucket;
                }

                hlist_move_list(&rxnet->peer_keepalive_new,
                                &rxnet->peer_keepalive[cursor]);
        }

        peer = hlist_entry(rxnet->peer_keepalive[cursor].first,
                           struct rxrpc_peer, keepalive_link);
        hlist_del_init(&peer->keepalive_link);
        if (!rxrpc_get_peer_maybe(peer))
                goto next_peer;

        spin_unlock_bh(&rxnet->peer_hash_lock);

        _debug("peer %u {%pISp}", peer->debug_id, &peer->srx.transport);

recalc:
        diff = ktime_divns(ktime_sub(peer->last_tx_at, base), NSEC_PER_SEC);
        if (diff < -30 || diff > 30)
                goto send; /* LSW of 64-bit time probably wrapped on 32-bit */
        diff += RXRPC_KEEPALIVE_TIME - 1;
        if (diff < 0)
                goto send;

        slot = (diff > RXRPC_KEEPALIVE_TIME - 1) ? RXRPC_KEEPALIVE_TIME - 1 : diff;
        if (slot == 0)
                goto send;

        /* A transmission to this peer occurred since last we examined it so
         * put it into the appropriate future bucket.
         */
        slot = (slot + cursor) % ARRAY_SIZE(rxnet->peer_keepalive);
        spin_lock_bh(&rxnet->peer_hash_lock);
        hlist_add_head(&peer->keepalive_link, &rxnet->peer_keepalive[slot]);
        rxrpc_put_peer(peer);
        goto next_peer;

send:
        rxrpc_send_keepalive(peer);
        now = ktime_get_real();
        goto recalc;

emptied_bucket:
        cursor++;
        if (cursor >= ARRAY_SIZE(rxnet->peer_keepalive))
                cursor = 0;
        base = ktime_add_ns(base, NSEC_PER_SEC);
        goto next_bucket;

resched:
        rxnet->peer_keepalive_base = base;
        rxnet->peer_keepalive_cursor = cursor;
        delay = nsecs_to_jiffies(-diff) + 1;
        timer_reduce(&rxnet->peer_keepalive_timer, jiffies + delay);
out:
        _leave("");
}