net/rxrpc/peer_object.c - arm/linux - Git at Google

 /* RxRPC remote transport endpoint record management
  *
  * Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version
  * 2 of the License, or (at your option) any later version.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/net.h>
 #include <linux/skbuff.h>
 #include <linux/udp.h>
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <linux/slab.h>
 #include <linux/hashtable.h>
 #include <net/sock.h>
 #include <net/af_rxrpc.h>
 #include <net/ip.h>
 #include <net/route.h>
 #include <net/ip6_route.h>
 #include "ar-internal.h"

 /*
  * Hash a peer key.
  */
 static unsigned long rxrpc_peer_hash_key(struct rxrpc_local *local,
 					 const struct sockaddr_rxrpc *srx)
 {
 	const u16 *p;
 	unsigned int i, size;
 	unsigned long hash_key;

 	_enter("");

 	hash_key = (unsigned long)local / __alignof__(*local);
 	hash_key += srx->transport_type;
 	hash_key += srx->transport_len;
 	hash_key += srx->transport.family;

 	switch (srx->transport.family) {
 	case AF_INET:
 		hash_key += (u16 __force)srx->transport.sin.sin_port;
 		size = sizeof(srx->transport.sin.sin_addr);
 		p = (u16 *)&srx->transport.sin.sin_addr;
 		break;
 #ifdef CONFIG_AF_RXRPC_IPV6
 	case AF_INET6:
 		hash_key += (u16 __force)srx->transport.sin.sin_port;
 		size = sizeof(srx->transport.sin6.sin6_addr);
 		p = (u16 *)&srx->transport.sin6.sin6_addr;
 		break;
 #endif
 	default:
 		WARN(1, "AF_RXRPC: Unsupported transport address family\n");
 		return 0;
 	}

 	/* Step through the peer address in 16-bit portions for speed */
 	for (i = 0; i < size; i += sizeof(*p), p++)
 		hash_key += *p;

 	_leave(" 0x%lx", hash_key);
 	return hash_key;
 }

 /*
  * Compare a peer to a key.  Return -ve, 0 or +ve to indicate less than, same
  * or greater than.
  *
  * Unfortunately, the primitives in linux/hashtable.h don't allow for sorted
  * buckets and mid-bucket insertion, so we don't make full use of this
  * information at this point.
  */
 static long rxrpc_peer_cmp_key(const struct rxrpc_peer *peer,
 			       struct rxrpc_local *local,
 			       const struct sockaddr_rxrpc *srx,
 			       unsigned long hash_key)
 {
 	long diff;

 	diff = ((peer->hash_key - hash_key) ?:
 		((unsigned long)peer->local - (unsigned long)local) ?:
 		(peer->srx.transport_type - srx->transport_type) ?:
 		(peer->srx.transport_len - srx->transport_len) ?:
 		(peer->srx.transport.family - srx->transport.family));
 	if (diff != 0)
 		return diff;

 	switch (srx->transport.family) {
 	case AF_INET:
 		return ((u16 __force)peer->srx.transport.sin.sin_port -
 			(u16 __force)srx->transport.sin.sin_port) ?:
 			memcmp(&peer->srx.transport.sin.sin_addr,
 			       &srx->transport.sin.sin_addr,
 			       sizeof(struct in_addr));
 #ifdef CONFIG_AF_RXRPC_IPV6
 	case AF_INET6:
 		return ((u16 __force)peer->srx.transport.sin6.sin6_port -
 			(u16 __force)srx->transport.sin6.sin6_port) ?:
 			memcmp(&peer->srx.transport.sin6.sin6_addr,
 			       &srx->transport.sin6.sin6_addr,
 			       sizeof(struct in6_addr));
 #endif
 	default:
 		BUG();
 	}
 }

 /*
  * Look up a remote transport endpoint for the specified address using RCU.
  */
 static struct rxrpc_peer *__rxrpc_lookup_peer_rcu(
 	struct rxrpc_local *local,
 	const struct sockaddr_rxrpc *srx,
 	unsigned long hash_key)
 {
 	struct rxrpc_peer *peer;
 	struct rxrpc_net *rxnet = local->rxnet;

 	hash_for_each_possible_rcu(rxnet->peer_hash, peer, hash_link, hash_key) {
 		if (rxrpc_peer_cmp_key(peer, local, srx, hash_key) == 0) {
 			if (atomic_read(&peer->usage) == 0)
 				return NULL;
 			return peer;
 		}
 	}

 	return NULL;
 }

 /*
  * Look up a remote transport endpoint for the specified address using RCU.
  */
 struct rxrpc_peer *rxrpc_lookup_peer_rcu(struct rxrpc_local *local,
 					 const struct sockaddr_rxrpc *srx)
 {
 	struct rxrpc_peer *peer;
 	unsigned long hash_key = rxrpc_peer_hash_key(local, srx);

 	peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
 	if (peer) {
 		_net("PEER %d {%pISp}", peer->debug_id, &peer->srx.transport);
 		_leave(" = %p {u=%d}", peer, atomic_read(&peer->usage));
 	}
 	return peer;
 }

 /*
  * assess the MTU size for the network interface through which this peer is
  * reached
  */
 static void rxrpc_assess_MTU_size(struct rxrpc_peer *peer)
 {
 	struct dst_entry *dst;
 	struct rtable *rt;
 	struct flowi fl;
 	struct flowi4 *fl4 = &fl.u.ip4;
 #ifdef CONFIG_AF_RXRPC_IPV6
 	struct flowi6 *fl6 = &fl.u.ip6;
 #endif

 	peer->if_mtu = 1500;

 	memset(&fl, 0, sizeof(fl));
 	switch (peer->srx.transport.family) {
 	case AF_INET:
 		rt = ip_route_output_ports(
 			&init_net, fl4, NULL,
 			peer->srx.transport.sin.sin_addr.s_addr, 0,
 			htons(7000), htons(7001), IPPROTO_UDP, 0, 0);
 		if (IS_ERR(rt)) {
 			_leave(" [route err %ld]", PTR_ERR(rt));
 			return;
 		}
 		dst = &rt->dst;
 		break;

 #ifdef CONFIG_AF_RXRPC_IPV6
 	case AF_INET6:
 		fl6->flowi6_iif = LOOPBACK_IFINDEX;
 		fl6->flowi6_scope = RT_SCOPE_UNIVERSE;
 		fl6->flowi6_proto = IPPROTO_UDP;
 		memcpy(&fl6->daddr, &peer->srx.transport.sin6.sin6_addr,
 		       sizeof(struct in6_addr));
 		fl6->fl6_dport = htons(7001);
 		fl6->fl6_sport = htons(7000);
 		dst = ip6_route_output(&init_net, NULL, fl6);
 		if (dst->error) {
 			_leave(" [route err %d]", dst->error);
 			return;
 		}
 		break;
 #endif

 	default:
 		BUG();
 	}

 	peer->if_mtu = dst_mtu(dst);
 	dst_release(dst);

 	_leave(" [if_mtu %u]", peer->if_mtu);
 }

 /*
  * Allocate a peer.
  */
 struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp)
 {
 	struct rxrpc_peer *peer;

 	_enter("");

 	peer = kzalloc(sizeof(struct rxrpc_peer), gfp);
 	if (peer) {
 		atomic_set(&peer->usage, 1);
 		peer->local = local;
 		INIT_HLIST_HEAD(&peer->error_targets);
 		INIT_WORK(&peer->error_distributor,
 			  &rxrpc_peer_error_distributor);
 		peer->service_conns = RB_ROOT;
 		seqlock_init(&peer->service_conn_lock);
 		spin_lock_init(&peer->lock);
 		peer->debug_id = atomic_inc_return(&rxrpc_debug_id);

 		if (RXRPC_TX_SMSS > 2190)
 			peer->cong_cwnd = 2;
 		else if (RXRPC_TX_SMSS > 1095)
 			peer->cong_cwnd = 3;
 		else
 			peer->cong_cwnd = 4;
 	}

 	_leave(" = %p", peer);
 	return peer;
 }

 /*
  * Initialise peer record.
  */
 static void rxrpc_init_peer(struct rxrpc_peer *peer, unsigned long hash_key)
 {
 	peer->hash_key = hash_key;
 	rxrpc_assess_MTU_size(peer);
 	peer->mtu = peer->if_mtu;
 	peer->rtt_last_req = ktime_get_real();

 	switch (peer->srx.transport.family) {
 	case AF_INET:
 		peer->hdrsize = sizeof(struct iphdr);
 		break;
 #ifdef CONFIG_AF_RXRPC_IPV6
 	case AF_INET6:
 		peer->hdrsize = sizeof(struct ipv6hdr);
 		break;
 #endif
 	default:
 		BUG();
 	}

 	switch (peer->srx.transport_type) {
 	case SOCK_DGRAM:
 		peer->hdrsize += sizeof(struct udphdr);
 		break;
 	default:
 		BUG();
 	}

 	peer->hdrsize += sizeof(struct rxrpc_wire_header);
 	peer->maxdata = peer->mtu - peer->hdrsize;
 }

 /*
  * Set up a new peer.
  */
 static struct rxrpc_peer *rxrpc_create_peer(struct rxrpc_local *local,
 					    struct sockaddr_rxrpc *srx,
 					    unsigned long hash_key,
 					    gfp_t gfp)
 {
 	struct rxrpc_peer *peer;

 	_enter("");

 	peer = rxrpc_alloc_peer(local, gfp);
 	if (peer) {
 		memcpy(&peer->srx, srx, sizeof(*srx));
 		rxrpc_init_peer(peer, hash_key);
 	}

 	_leave(" = %p", peer);
 	return peer;
 }

 /*
  * Set up a new incoming peer.  The address is prestored in the preallocated
  * peer.
  */
 struct rxrpc_peer *rxrpc_lookup_incoming_peer(struct rxrpc_local *local,
 					      struct rxrpc_peer *prealloc)
 {
 	struct rxrpc_peer *peer;
 	struct rxrpc_net *rxnet = local->rxnet;
 	unsigned long hash_key;

 	hash_key = rxrpc_peer_hash_key(local, &prealloc->srx);
 	prealloc->local = local;
 	rxrpc_init_peer(prealloc, hash_key);

 	spin_lock(&rxnet->peer_hash_lock);

 	/* Need to check that we aren't racing with someone else */
 	peer = __rxrpc_lookup_peer_rcu(local, &prealloc->srx, hash_key);
 	if (peer && !rxrpc_get_peer_maybe(peer))
 		peer = NULL;
 	if (!peer) {
 		peer = prealloc;
 		hash_add_rcu(rxnet->peer_hash, &peer->hash_link, hash_key);
 	}

 	spin_unlock(&rxnet->peer_hash_lock);
 	return peer;
 }

 /*
  * obtain a remote transport endpoint for the specified address
  */
 struct rxrpc_peer *rxrpc_lookup_peer(struct rxrpc_local *local,
 				     struct sockaddr_rxrpc *srx, gfp_t gfp)
 {
 	struct rxrpc_peer *peer, *candidate;
 	struct rxrpc_net *rxnet = local->rxnet;
 	unsigned long hash_key = rxrpc_peer_hash_key(local, srx);

 	_enter("{%pISp}", &srx->transport);

 	/* search the peer list first */
 	rcu_read_lock();
 	peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
 	if (peer && !rxrpc_get_peer_maybe(peer))
 		peer = NULL;
 	rcu_read_unlock();

 	if (!peer) {
 		/* The peer is not yet present in hash - create a candidate
 		 * for a new record and then redo the search.
 		 */
 		candidate = rxrpc_create_peer(local, srx, hash_key, gfp);
 		if (!candidate) {
 			_leave(" = NULL [nomem]");
 			return NULL;
 		}

 		spin_lock_bh(&rxnet->peer_hash_lock);

 		/* Need to check that we aren't racing with someone else */
 		peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
 		if (peer && !rxrpc_get_peer_maybe(peer))
 			peer = NULL;
 		if (!peer)
 			hash_add_rcu(rxnet->peer_hash,
 				     &candidate->hash_link, hash_key);

 		spin_unlock_bh(&rxnet->peer_hash_lock);

 		if (peer)
 			kfree(candidate);
 		else
 			peer = candidate;
 	}

 	_net("PEER %d {%pISp}", peer->debug_id, &peer->srx.transport);

 	_leave(" = %p {u=%d}", peer, atomic_read(&peer->usage));
 	return peer;
 }

 /*
  * Discard a ref on a remote peer record.
  */
 void __rxrpc_put_peer(struct rxrpc_peer *peer)
 {
 	struct rxrpc_net *rxnet = peer->local->rxnet;

 	ASSERT(hlist_empty(&peer->error_targets));

 	spin_lock_bh(&rxnet->peer_hash_lock);
 	hash_del_rcu(&peer->hash_link);
 	spin_unlock_bh(&rxnet->peer_hash_lock);

 	kfree_rcu(peer, rcu);
 }

 /**
  * rxrpc_kernel_get_peer - Get the peer address of a call
  * @sock: The socket on which the call is in progress.
  * @call: The call to query
  * @_srx: Where to place the result
  *
  * Get the address of the remote peer in a call.
  */
 void rxrpc_kernel_get_peer(struct socket *sock, struct rxrpc_call *call,
 			   struct sockaddr_rxrpc *_srx)
 {
 	*_srx = call->peer->srx;
 }
 EXPORT_SYMBOL(rxrpc_kernel_get_peer);
	/* RxRPC remote transport endpoint record management
	*
	* Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/net.h>
	#include <linux/skbuff.h>
	#include <linux/udp.h>
	#include <linux/in.h>
	#include <linux/in6.h>
	#include <linux/slab.h>
	#include <linux/hashtable.h>
	#include <net/sock.h>
	#include <net/af_rxrpc.h>
	#include <net/ip.h>
	#include <net/route.h>
	#include <net/ip6_route.h>
	#include "ar-internal.h"

	/*
	* Hash a peer key.
	*/
	static unsigned long rxrpc_peer_hash_key(struct rxrpc_local *local,
	const struct sockaddr_rxrpc *srx)
	{
	const u16 *p;
	unsigned int i, size;
	unsigned long hash_key;

	_enter("");

	hash_key = (unsigned long)local / __alignof__(*local);
	hash_key += srx->transport_type;
	hash_key += srx->transport_len;
	hash_key += srx->transport.family;

	switch (srx->transport.family) {
	case AF_INET:
	hash_key += (u16 __force)srx->transport.sin.sin_port;
	size = sizeof(srx->transport.sin.sin_addr);
	p = (u16 *)&srx->transport.sin.sin_addr;
	break;
	#ifdef CONFIG_AF_RXRPC_IPV6
	case AF_INET6:
	hash_key += (u16 __force)srx->transport.sin.sin_port;
	size = sizeof(srx->transport.sin6.sin6_addr);
	p = (u16 *)&srx->transport.sin6.sin6_addr;
	break;
	#endif
	default:
	WARN(1, "AF_RXRPC: Unsupported transport address family\n");
	return 0;
	}

	/* Step through the peer address in 16-bit portions for speed */
	for (i = 0; i < size; i += sizeof(*p), p++)
	hash_key += *p;

	_leave(" 0x%lx", hash_key);
	return hash_key;
	}

	/*
	* Compare a peer to a key. Return -ve, 0 or +ve to indicate less than, same
	* or greater than.
	*
	* Unfortunately, the primitives in linux/hashtable.h don't allow for sorted
	* buckets and mid-bucket insertion, so we don't make full use of this
	* information at this point.
	*/
	static long rxrpc_peer_cmp_key(const struct rxrpc_peer *peer,
	struct rxrpc_local *local,
	const struct sockaddr_rxrpc *srx,
	unsigned long hash_key)
	{
	long diff;

	diff = ((peer->hash_key - hash_key) ?:
	((unsigned long)peer->local - (unsigned long)local) ?:
	(peer->srx.transport_type - srx->transport_type) ?:
	(peer->srx.transport_len - srx->transport_len) ?:
	(peer->srx.transport.family - srx->transport.family));
	if (diff != 0)
	return diff;

	switch (srx->transport.family) {
	case AF_INET:
	return ((u16 __force)peer->srx.transport.sin.sin_port -
	(u16 __force)srx->transport.sin.sin_port) ?:
	memcmp(&peer->srx.transport.sin.sin_addr,
	&srx->transport.sin.sin_addr,
	sizeof(struct in_addr));
	#ifdef CONFIG_AF_RXRPC_IPV6
	case AF_INET6:
	return ((u16 __force)peer->srx.transport.sin6.sin6_port -
	(u16 __force)srx->transport.sin6.sin6_port) ?:
	memcmp(&peer->srx.transport.sin6.sin6_addr,
	&srx->transport.sin6.sin6_addr,
	sizeof(struct in6_addr));
	#endif
	default:
	BUG();
	}
	}

	/*
	* Look up a remote transport endpoint for the specified address using RCU.
	*/
	static struct rxrpc_peer *__rxrpc_lookup_peer_rcu(
	struct rxrpc_local *local,
	const struct sockaddr_rxrpc *srx,
	unsigned long hash_key)
	{
	struct rxrpc_peer *peer;
	struct rxrpc_net *rxnet = local->rxnet;

	hash_for_each_possible_rcu(rxnet->peer_hash, peer, hash_link, hash_key) {
	if (rxrpc_peer_cmp_key(peer, local, srx, hash_key) == 0) {
	if (atomic_read(&peer->usage) == 0)
	return NULL;
	return peer;
	}
	}

	return NULL;
	}

	/*
	* Look up a remote transport endpoint for the specified address using RCU.
	*/
	struct rxrpc_peer rxrpc_lookup_peer_rcu(struct rxrpc_local local,
	const struct sockaddr_rxrpc *srx)
	{
	struct rxrpc_peer *peer;
	unsigned long hash_key = rxrpc_peer_hash_key(local, srx);

	peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
	if (peer) {
	_net("PEER %d {%pISp}", peer->debug_id, &peer->srx.transport);
	_leave(" = %p {u=%d}", peer, atomic_read(&peer->usage));
	}
	return peer;
	}

	/*
	* assess the MTU size for the network interface through which this peer is
	* reached
	*/
	static void rxrpc_assess_MTU_size(struct rxrpc_peer *peer)
	{
	struct dst_entry *dst;
	struct rtable *rt;
	struct flowi fl;
	struct flowi4 *fl4 = &fl.u.ip4;
	#ifdef CONFIG_AF_RXRPC_IPV6
	struct flowi6 *fl6 = &fl.u.ip6;
	#endif

	peer->if_mtu = 1500;

	memset(&fl, 0, sizeof(fl));
	switch (peer->srx.transport.family) {
	case AF_INET:
	rt = ip_route_output_ports(
	&init_net, fl4, NULL,
	peer->srx.transport.sin.sin_addr.s_addr, 0,
	htons(7000), htons(7001), IPPROTO_UDP, 0, 0);
	if (IS_ERR(rt)) {
	_leave(" [route err %ld]", PTR_ERR(rt));
	return;
	}
	dst = &rt->dst;
	break;

	#ifdef CONFIG_AF_RXRPC_IPV6
	case AF_INET6:
	fl6->flowi6_iif = LOOPBACK_IFINDEX;
	fl6->flowi6_scope = RT_SCOPE_UNIVERSE;
	fl6->flowi6_proto = IPPROTO_UDP;
	memcpy(&fl6->daddr, &peer->srx.transport.sin6.sin6_addr,
	sizeof(struct in6_addr));
	fl6->fl6_dport = htons(7001);
	fl6->fl6_sport = htons(7000);
	dst = ip6_route_output(&init_net, NULL, fl6);
	if (dst->error) {
	_leave(" [route err %d]", dst->error);
	return;
	}
	break;
	#endif

	default:
	BUG();
	}

	peer->if_mtu = dst_mtu(dst);
	dst_release(dst);

	_leave(" [if_mtu %u]", peer->if_mtu);
	}

	/*
	* Allocate a peer.
	*/
	struct rxrpc_peer rxrpc_alloc_peer(struct rxrpc_local local, gfp_t gfp)
	{
	struct rxrpc_peer *peer;

	_enter("");

	peer = kzalloc(sizeof(struct rxrpc_peer), gfp);
	if (peer) {
	atomic_set(&peer->usage, 1);
	peer->local = local;
	INIT_HLIST_HEAD(&peer->error_targets);
	INIT_WORK(&peer->error_distributor,
	&rxrpc_peer_error_distributor);
	peer->service_conns = RB_ROOT;
	seqlock_init(&peer->service_conn_lock);
	spin_lock_init(&peer->lock);
	peer->debug_id = atomic_inc_return(&rxrpc_debug_id);

	if (RXRPC_TX_SMSS > 2190)
	peer->cong_cwnd = 2;
	else if (RXRPC_TX_SMSS > 1095)
	peer->cong_cwnd = 3;
	else
	peer->cong_cwnd = 4;
	}

	_leave(" = %p", peer);
	return peer;
	}

	/*
	* Initialise peer record.
	*/
	static void rxrpc_init_peer(struct rxrpc_peer *peer, unsigned long hash_key)
	{
	peer->hash_key = hash_key;
	rxrpc_assess_MTU_size(peer);
	peer->mtu = peer->if_mtu;
	peer->rtt_last_req = ktime_get_real();

	switch (peer->srx.transport.family) {
	case AF_INET:
	peer->hdrsize = sizeof(struct iphdr);
	break;
	#ifdef CONFIG_AF_RXRPC_IPV6
	case AF_INET6:
	peer->hdrsize = sizeof(struct ipv6hdr);
	break;
	#endif
	default:
	BUG();
	}

	switch (peer->srx.transport_type) {
	case SOCK_DGRAM:
	peer->hdrsize += sizeof(struct udphdr);
	break;
	default:
	BUG();
	}

	peer->hdrsize += sizeof(struct rxrpc_wire_header);
	peer->maxdata = peer->mtu - peer->hdrsize;
	}

	/*
	* Set up a new peer.
	*/
	static struct rxrpc_peer rxrpc_create_peer(struct rxrpc_local local,
	struct sockaddr_rxrpc *srx,
	unsigned long hash_key,
	gfp_t gfp)
	{
	struct rxrpc_peer *peer;

	_enter("");

	peer = rxrpc_alloc_peer(local, gfp);
	if (peer) {
	memcpy(&peer->srx, srx, sizeof(*srx));
	rxrpc_init_peer(peer, hash_key);
	}

	_leave(" = %p", peer);
	return peer;
	}

	/*
	* Set up a new incoming peer. The address is prestored in the preallocated
	* peer.
	*/
	struct rxrpc_peer rxrpc_lookup_incoming_peer(struct rxrpc_local local,
	struct rxrpc_peer *prealloc)
	{
	struct rxrpc_peer *peer;
	struct rxrpc_net *rxnet = local->rxnet;
	unsigned long hash_key;

	hash_key = rxrpc_peer_hash_key(local, &prealloc->srx);
	prealloc->local = local;
	rxrpc_init_peer(prealloc, hash_key);

	spin_lock(&rxnet->peer_hash_lock);

	/* Need to check that we aren't racing with someone else */
	peer = __rxrpc_lookup_peer_rcu(local, &prealloc->srx, hash_key);
	if (peer && !rxrpc_get_peer_maybe(peer))
	peer = NULL;
	if (!peer) {
	peer = prealloc;
	hash_add_rcu(rxnet->peer_hash, &peer->hash_link, hash_key);
	}

	spin_unlock(&rxnet->peer_hash_lock);
	return peer;
	}

	/*
	* obtain a remote transport endpoint for the specified address
	*/
	struct rxrpc_peer rxrpc_lookup_peer(struct rxrpc_local local,
	struct sockaddr_rxrpc *srx, gfp_t gfp)
	{
	struct rxrpc_peer peer, candidate;
	struct rxrpc_net *rxnet = local->rxnet;
	unsigned long hash_key = rxrpc_peer_hash_key(local, srx);

	_enter("{%pISp}", &srx->transport);

	/* search the peer list first */
	rcu_read_lock();
	peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
	if (peer && !rxrpc_get_peer_maybe(peer))
	peer = NULL;
	rcu_read_unlock();

	if (!peer) {
	/* The peer is not yet present in hash - create a candidate
	* for a new record and then redo the search.
	*/
	candidate = rxrpc_create_peer(local, srx, hash_key, gfp);
	if (!candidate) {
	_leave(" = NULL [nomem]");
	return NULL;
	}

	spin_lock_bh(&rxnet->peer_hash_lock);

	/* Need to check that we aren't racing with someone else */
	peer = __rxrpc_lookup_peer_rcu(local, srx, hash_key);
	if (peer && !rxrpc_get_peer_maybe(peer))
	peer = NULL;
	if (!peer)
	hash_add_rcu(rxnet->peer_hash,
	&candidate->hash_link, hash_key);

	spin_unlock_bh(&rxnet->peer_hash_lock);

	if (peer)
	kfree(candidate);
	else
	peer = candidate;
	}

	_net("PEER %d {%pISp}", peer->debug_id, &peer->srx.transport);

	_leave(" = %p {u=%d}", peer, atomic_read(&peer->usage));
	return peer;
	}

	/*
	* Discard a ref on a remote peer record.
	*/
	void __rxrpc_put_peer(struct rxrpc_peer *peer)
	{
	struct rxrpc_net *rxnet = peer->local->rxnet;

	ASSERT(hlist_empty(&peer->error_targets));

	spin_lock_bh(&rxnet->peer_hash_lock);
	hash_del_rcu(&peer->hash_link);
	spin_unlock_bh(&rxnet->peer_hash_lock);

	kfree_rcu(peer, rcu);
	}

	/**
	* rxrpc_kernel_get_peer - Get the peer address of a call
	* @sock: The socket on which the call is in progress.
	* @call: The call to query
	* @_srx: Where to place the result
	*
	* Get the address of the remote peer in a call.
	*/
	void rxrpc_kernel_get_peer(struct socket sock, struct rxrpc_call call,
	struct sockaddr_rxrpc *_srx)
	{
	*_srx = call->peer->srx;
	}
	EXPORT_SYMBOL(rxrpc_kernel_get_peer);