// 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:
  	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);

  		if (call->state < RXRPC_CALL_COMPLETE &&
  		    rxrpc_set_call_completion(call, compl, 0, -error))

  			rxrpc_notify_socket(call);

  	}

  }

  
  /*
   * 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;

  	spin_lock(&peer->rtt_input_lock);

  	/* 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;
  	}

  	spin_unlock(&peer->rtt_input_lock);

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

  	/* Don't need to update this under lock */

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

  
  /*

   * 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("");
  }