// 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 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)
{
	/* 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;
		}
	}

	if (mtu < peer->mtu) {
		spin_lock_bh(&peer->lock);
		peer->mtu = mtu;
		peer->maxdata = peer->mtu - peer->hdrsize;
		spin_unlock_bh(&peer->lock);
	}
}

/*
 * 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 = NULL;
	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_local_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->ee.ee_info);
		goto out;
	}

	rxrpc_store_error(peer, serr);
out:
	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_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, 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, rxrpc_local_use_peer_keepalive)) {
			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_local_unuse_peer_keepalive);
		}
		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("");
}