// 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 sock_exterr_skb *);
static void rxrpc_distribute_error(struct rxrpc_peer *, int,
                                   enum rxrpc_call_completion);

/*
 * 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_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:
                        _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:
                switch (serr->ee.ee_origin) {
                case SO_EE_ORIGIN_ICMP6:
                        _net("Rx 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:
                        _net("Rx ICMP on v6 sock");
                        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, 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;
        struct rxrpc_peer *peer;
        struct sk_buff *skb;

        rcu_read_lock();
        local = rcu_dereference_sk_user_data(sk);
        if (unlikely(!local)) {
                rcu_read_unlock();
                return;
        }
        _enter("%p{%d}", sk, local->debug_id);

        /* Clear the outstanding error value on the socket so that it doesn't
         * cause kernel_sendmsg() to return it later.
         */
        sock_error(sk);

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

        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_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_freed);
                rxrpc_put_peer(peer);
                _leave(" [MTU update]");
                return;
        }

        rxrpc_store_error(peer, serr);
        rcu_read_unlock();
        rxrpc_free_skb(skb, rxrpc_skb_freed);
        rxrpc_put_peer(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)
{
        enum rxrpc_call_completion compl = RXRPC_CALL_NETWORK_ERROR;
        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);
                compl = RXRPC_CALL_LOCAL_ERROR;
                break;

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

        rxrpc_distribute_error(peer, err, compl);
}

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

        hlist_for_each_entry_rcu(call, &peer->error_targets, error_link) {
                rxrpc_see_call(call);
                rxrpc_set_call_completion(call, compl, 0, -error);
        }
}

/*
 * 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;
        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))
                        continue;

                if (__rxrpc_use_local(peer->local)) {
                        spin_unlock_bh(&rxnet->peer_hash_lock);

                        keepalive_at = peer->last_tx_at + 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]);
                        rxrpc_unuse_local(peer->local);
                }
                rxrpc_put_peer_locked(peer);
        }

        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("");
}