net/rxrpc/peer_event.c - third_party/kernel - Git at Google

 // 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);
 	}
 }

 /*
  * 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("");
 }
	// 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);
	}
	}

	/*
	* 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("");
	}