/* 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
  ");
  		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);