// SPDX-License-Identifier: GPL-2.0-or-later
/* Peer event handling, typically ICMP messages.
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#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 sk_buff *);
static void rxrpc_distribute_error(struct rxrpc_peer *, struct sk_buff *,
                                   enum rxrpc_call_completion, int);

/*
 * Find the peer associated with a local error.
 */
static struct rxrpc_peer *rxrpc_lookup_peer_local_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_len = sizeof(srx->transport.sin);
                srx->transport.family = AF_INET;
                srx->transport.sin.sin_port = serr->port;
                switch (serr->ee.ee_origin) {
                case SO_EE_ORIGIN_ICMP:
                        memcpy(&srx->transport.sin.sin_addr,
                               skb_network_header(skb) + serr->addr_offset,
                               sizeof(struct in_addr));
                        break;
                case SO_EE_ORIGIN_ICMP6:
                        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:
                switch (serr->ee.ee_origin) {
                case SO_EE_ORIGIN_ICMP6:
                        srx->transport.sin6.sin6_port = serr->port;
                        memcpy(&srx->transport.sin6.sin6_addr,
                               skb_network_header(skb) + serr->addr_offset,
                               sizeof(struct in6_addr));
                        break;
                case SO_EE_ORIGIN_ICMP:
                        srx->transport_len = sizeof(srx->transport.sin);
                        srx->transport.family = AF_INET;
                        srx->transport.sin.sin_port = serr->port;
                        memcpy(&srx->transport.sin.sin_addr,
                               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, unsigned int mtu)
{
        unsigned int max_data;

        /* wind down the local interface MTU */
        if (mtu > 0 && peer->if_mtu == 65535 && mtu < peer->if_mtu)
                peer->if_mtu = 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;
                }
        }

        max_data = max_t(int, mtu - peer->hdrsize, 500);
        if (max_data < peer->max_data) {
                if (peer->pmtud_good > max_data)
                        peer->pmtud_good = max_data;
                if (peer->pmtud_bad > max_data + 1)
                        peer->pmtud_bad = max_data + 1;

                trace_rxrpc_pmtud_reduce(peer, 0, max_data, rxrpc_pmtud_reduce_icmp);
                peer->max_data = max_data;
        }
}

/*
 * Handle an error received on the local endpoint.
 */
void rxrpc_input_error(struct rxrpc_local *local, struct sk_buff *skb)
{
        struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
        struct sockaddr_rxrpc srx;
        struct rxrpc_peer *peer = NULL;

        _enter("L=%x", local->debug_id);

        if (!skb->len && serr->ee.ee_origin == SO_EE_ORIGIN_TIMESTAMPING) {
                _leave("UDP empty message");
                return;
        }

        rcu_read_lock();
        peer = rxrpc_lookup_peer_local_rcu(local, skb, &srx);
        if (peer && !rxrpc_get_peer_maybe(peer, rxrpc_peer_get_input_error))
                peer = NULL;
        rcu_read_unlock();
        if (!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->ee.ee_info);
                goto out;
        }

        if ((serr->ee.ee_origin == SO_EE_ORIGIN_ICMP6 &&
             serr->ee.ee_type == ICMPV6_PKT_TOOBIG &&
             serr->ee.ee_code == 0)) {
                rxrpc_adjust_mtu(peer, serr->ee.ee_info);
                goto out;
        }

        rxrpc_store_error(peer, skb);
out:
        rxrpc_put_peer(peer, rxrpc_peer_put_input_error);
}

/*
 * Map an error report to error codes on the peer record.
 */
static void rxrpc_store_error(struct rxrpc_peer *peer, struct sk_buff *skb)
{
        enum rxrpc_call_completion compl = RXRPC_CALL_NETWORK_ERROR;
        struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
        struct sock_extended_err *ee = &serr->ee;
        int err = ee->ee_errno;

        _enter("");

        switch (ee->ee_origin) {
        case SO_EE_ORIGIN_NONE:
        case SO_EE_ORIGIN_LOCAL:
                compl = RXRPC_CALL_LOCAL_ERROR;
                break;

        case SO_EE_ORIGIN_ICMP6:
                if (err == EACCES)
                        err = EHOSTUNREACH;
                fallthrough;
        case SO_EE_ORIGIN_ICMP:
        default:
                break;
        }

        rxrpc_distribute_error(peer, skb, compl, err);
}

/*
 * Distribute an error that occurred on a peer.
 */
static void rxrpc_distribute_error(struct rxrpc_peer *peer, struct sk_buff *skb,
                                   enum rxrpc_call_completion compl, int err)
{
        struct rxrpc_call *call;
        HLIST_HEAD(error_targets);

        spin_lock_irq(&peer->lock);
        hlist_move_list(&peer->error_targets, &error_targets);

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

                rxrpc_see_call(call, rxrpc_call_see_distribute_error);
                rxrpc_set_call_completion(call, compl, 0, -err);
                rxrpc_input_call_event(call);

                spin_lock_irq(&peer->lock);
        }

        spin_unlock_irq(&peer->lock);
}

/*
 * Reconstruct the last transmission time.  The difference calculated should be
 * valid provided no more than ~68 years elapsed since the last transmission.
 */
static time64_t rxrpc_peer_get_tx_mark(const struct rxrpc_peer *peer, time64_t base)
{
        s32 last_tx_at = READ_ONCE(peer->last_tx_at);
        s32 base_lsw = base;
        s32 diff = last_tx_at - base_lsw;

        diff = clamp(diff, -RXRPC_KEEPALIVE_TIME, RXRPC_KEEPALIVE_TIME);

        return diff + base;
}

/*
 * Perform keep-alive pings.
 */
static void rxrpc_peer_keepalive_dispatch(struct rxrpc_net *rxnet,
                                          struct list_head *collector,
                                          time64_t base,
                                          u8 cursor)
{
        struct rxrpc_peer *peer;
        const u8 mask = ARRAY_SIZE(rxnet->peer_keepalive) - 1;
        time64_t keepalive_at;
        bool use;
        int slot;

        spin_lock_bh(&rxnet->peer_hash_lock);

        while (!list_empty(collector)) {
                peer = list_entry(collector->next,
                                  struct rxrpc_peer, keepalive_link);

                list_del_init(&peer->keepalive_link);
                if (!rxrpc_get_peer_maybe(peer, rxrpc_peer_get_keepalive))
                        continue;

                use = __rxrpc_use_local(peer->local, rxrpc_local_use_peer_keepalive);
                spin_unlock_bh(&rxnet->peer_hash_lock);

                if (use) {
                        keepalive_at = rxrpc_peer_get_tx_mark(peer, base) + RXRPC_KEEPALIVE_TIME;
                        slot = keepalive_at - base;
                        _debug("%02x peer %u t=%d {%pISp}",
                               cursor, peer->debug_id, slot, &peer->srx.transport);

                        if (keepalive_at <= base ||
                            keepalive_at > base + RXRPC_KEEPALIVE_TIME) {
                                rxrpc_send_keepalive(peer);
                                slot = RXRPC_KEEPALIVE_TIME;
                        }

                        /* A transmission to this peer occurred since last we
                         * examined it so put it into the appropriate future
                         * bucket.
                         */
                        slot += cursor;
                        slot &= mask;
                        spin_lock_bh(&rxnet->peer_hash_lock);
                        list_add_tail(&peer->keepalive_link,
                                      &rxnet->peer_keepalive[slot & mask]);
                        spin_unlock_bh(&rxnet->peer_hash_lock);
                        rxrpc_unuse_local(peer->local, rxrpc_local_unuse_peer_keepalive);
                }
                rxrpc_put_peer(peer, rxrpc_peer_put_keepalive);
                spin_lock_bh(&rxnet->peer_hash_lock);
        }

        spin_unlock_bh(&rxnet->peer_hash_lock);
}

/*
 * 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);
        const u8 mask = ARRAY_SIZE(rxnet->peer_keepalive) - 1;
        time64_t base, now, delay;
        u8 cursor, stop;
        LIST_HEAD(collector);

        now = ktime_get_seconds();
        base = rxnet->peer_keepalive_base;
        cursor = rxnet->peer_keepalive_cursor;
        _enter("%lld,%u", base - now, cursor);

        if (!rxnet->live)
                return;

        /* Remove to a temporary list all the peers that are currently lodged
         * in expired buckets plus all new peers.
         *
         * Everything in the bucket at the cursor is processed this
         * second; the bucket at cursor + 1 goes at now + 1s and so
         * on...
         */
        spin_lock_bh(&rxnet->peer_hash_lock);
        list_splice_init(&rxnet->peer_keepalive_new, &collector);

        stop = cursor + ARRAY_SIZE(rxnet->peer_keepalive);
        while (base <= now && (s8)(cursor - stop) < 0) {
                list_splice_tail_init(&rxnet->peer_keepalive[cursor & mask],
                                      &collector);
                base++;
                cursor++;
        }

        base = now;
        spin_unlock_bh(&rxnet->peer_hash_lock);

        rxnet->peer_keepalive_base = base;
        rxnet->peer_keepalive_cursor = cursor;
        rxrpc_peer_keepalive_dispatch(rxnet, &collector, base, cursor);
        ASSERT(list_empty(&collector));

        /* Schedule the timer for the next occupied timeslot. */
        cursor = rxnet->peer_keepalive_cursor;
        stop = cursor + RXRPC_KEEPALIVE_TIME - 1;
        for (; (s8)(cursor - stop) < 0; cursor++) {
                if (!list_empty(&rxnet->peer_keepalive[cursor & mask]))
                        break;
                base++;
        }

        now = ktime_get_seconds();
        delay = base - now;
        if (delay < 1)
                delay = 1;
        delay *= HZ;
        if (rxnet->live)
                timer_reduce(&rxnet->peer_keepalive_timer, jiffies + delay);

        _leave("");
}

/*
 * Do path MTU probing.
 */
void rxrpc_input_probe_for_pmtud(struct rxrpc_connection *conn, rxrpc_serial_t acked_serial,
                                 bool sendmsg_fail)
{
        struct rxrpc_peer *peer = conn->peer;
        unsigned int max_data = peer->max_data;
        int good, trial, bad, jumbo;

        good  = peer->pmtud_good;
        trial = peer->pmtud_trial;
        bad   = peer->pmtud_bad;
        if (good >= bad - 1) {
                conn->pmtud_probe = 0;
                peer->pmtud_lost = false;
                return;
        }

        if (!peer->pmtud_probing)
                goto send_probe;

        if (sendmsg_fail || after(acked_serial, conn->pmtud_probe)) {
                /* Retry a lost probe. */
                if (!peer->pmtud_lost) {
                        trace_rxrpc_pmtud_lost(conn, acked_serial);
                        conn->pmtud_probe = 0;
                        peer->pmtud_lost = true;
                        goto send_probe;
                }

                /* The probed size didn't seem to get through. */
                bad = trial;
                peer->pmtud_bad = bad;
                if (bad <= max_data)
                        max_data = bad - 1;
        } else {
                /* It did get through. */
                good = trial;
                peer->pmtud_good = good;
                if (good > max_data)
                        max_data = good;
        }

        max_data = umin(max_data, peer->ackr_max_data);
        if (max_data != peer->max_data)
                peer->max_data = max_data;

        jumbo = max_data + sizeof(struct rxrpc_jumbo_header);
        jumbo /= RXRPC_JUMBO_SUBPKTLEN;
        peer->pmtud_jumbo = jumbo;

        trace_rxrpc_pmtud_rx(conn, acked_serial);
        conn->pmtud_probe = 0;
        peer->pmtud_lost = false;

        if (good < RXRPC_JUMBO(2) && bad > RXRPC_JUMBO(2))
                trial = RXRPC_JUMBO(2);
        else if (good < RXRPC_JUMBO(4) && bad > RXRPC_JUMBO(4))
                trial = RXRPC_JUMBO(4);
        else if (good < RXRPC_JUMBO(3) && bad > RXRPC_JUMBO(3))
                trial = RXRPC_JUMBO(3);
        else if (good < RXRPC_JUMBO(6) && bad > RXRPC_JUMBO(6))
                trial = RXRPC_JUMBO(6);
        else if (good < RXRPC_JUMBO(5) && bad > RXRPC_JUMBO(5))
                trial = RXRPC_JUMBO(5);
        else if (good < RXRPC_JUMBO(8) && bad > RXRPC_JUMBO(8))
                trial = RXRPC_JUMBO(8);
        else if (good < RXRPC_JUMBO(7) && bad > RXRPC_JUMBO(7))
                trial = RXRPC_JUMBO(7);
        else
                trial = (good + bad) / 2;
        peer->pmtud_trial = trial;

        if (good >= bad)
                return;

send_probe:
        peer->pmtud_pending = true;
}