/*
   * gw.c - CAN frame Gateway/Router/Bridge with netlink interface
   *
   * Copyright (c) 2011 Volkswagen Group Electronic Research
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of Volkswagen nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * Alternatively, provided that this notice is retained in full, this
   * software may be distributed under the terms of the GNU General
   * Public License ("GPL") version 2, in which case the provisions of the
   * GPL apply INSTEAD OF those given above.
   *
   * The provided data structures and external interfaces from this code
   * are not restricted to be used by modules with a GPL compatible license.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
   * DAMAGE.
   *

   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/types.h>

  #include <linux/kernel.h>

  #include <linux/list.h>
  #include <linux/spinlock.h>
  #include <linux/rcupdate.h>
  #include <linux/rculist.h>
  #include <linux/net.h>
  #include <linux/netdevice.h>
  #include <linux/if_arp.h>
  #include <linux/skbuff.h>
  #include <linux/can.h>
  #include <linux/can/core.h>

  #include <linux/can/skb.h>

  #include <linux/can/gw.h>
  #include <net/rtnetlink.h>
  #include <net/net_namespace.h>
  #include <net/sock.h>

  #define CAN_GW_VERSION "20130117"
  #define CAN_GW_NAME "can-gw"

  
  MODULE_DESCRIPTION("PF_CAN netlink gateway");
  MODULE_LICENSE("Dual BSD/GPL");
  MODULE_AUTHOR("Oliver Hartkopp <oliver.hartkopp@volkswagen.de>");

  MODULE_ALIAS(CAN_GW_NAME);
  
  #define CGW_MIN_HOPS 1
  #define CGW_MAX_HOPS 6
  #define CGW_DEFAULT_HOPS 1
  
  static unsigned int max_hops __read_mostly = CGW_DEFAULT_HOPS;
  module_param(max_hops, uint, S_IRUGO);
  MODULE_PARM_DESC(max_hops,
  		 "maximum " CAN_GW_NAME " routing hops for CAN frames "
  		 "(valid values: " __stringify(CGW_MIN_HOPS) "-"
  		 __stringify(CGW_MAX_HOPS) " hops, "
  		 "default: " __stringify(CGW_DEFAULT_HOPS) ")");

  static HLIST_HEAD(cgw_list);

  static struct notifier_block notifier;
  
  static struct kmem_cache *cgw_cache __read_mostly;
  
  /* structure that contains the (on-the-fly) CAN frame modifications */
  struct cf_mod {
  	struct {
  		struct can_frame and;
  		struct can_frame or;
  		struct can_frame xor;
  		struct can_frame set;
  	} modframe;
  	struct {
  		u8 and;
  		u8 or;
  		u8 xor;
  		u8 set;
  	} modtype;
  	void (*modfunc[MAX_MODFUNCTIONS])(struct can_frame *cf,
  					  struct cf_mod *mod);
  
  	/* CAN frame checksum calculation after CAN frame modifications */
  	struct {
  		struct cgw_csum_xor xor;
  		struct cgw_csum_crc8 crc8;
  	} csum;
  	struct {
  		void (*xor)(struct can_frame *cf, struct cgw_csum_xor *xor);
  		void (*crc8)(struct can_frame *cf, struct cgw_csum_crc8 *crc8);
  	} csumfunc;

  	u32 uid;

  };
  
  
  /*
   * So far we just support CAN -> CAN routing and frame modifications.
   *
   * The internal can_can_gw structure contains data and attributes for
   * a CAN -> CAN gateway job.
   */
  struct can_can_gw {
  	struct can_filter filter;
  	int src_idx;
  	int dst_idx;
  };
  
  /* list entry for CAN gateways jobs */
  struct cgw_job {
  	struct hlist_node list;
  	struct rcu_head rcu;
  	u32 handled_frames;
  	u32 dropped_frames;

  	u32 deleted_frames;

  	struct cf_mod mod;
  	union {
  		/* CAN frame data source */
  		struct net_device *dev;
  	} src;
  	union {
  		/* CAN frame data destination */
  		struct net_device *dev;
  	} dst;
  	union {
  		struct can_can_gw ccgw;
  		/* tbc */
  	};
  	u8 gwtype;

  	u8 limit_hops;

  	u16 flags;
  };
  
  /* modification functions that are invoked in the hot path in can_can_gw_rcv */
  
  #define MODFUNC(func, op) static void func(struct can_frame *cf, \
  					   struct cf_mod *mod) { op ; }
  
  MODFUNC(mod_and_id, cf->can_id &= mod->modframe.and.can_id)
  MODFUNC(mod_and_dlc, cf->can_dlc &= mod->modframe.and.can_dlc)
  MODFUNC(mod_and_data, *(u64 *)cf->data &= *(u64 *)mod->modframe.and.data)
  MODFUNC(mod_or_id, cf->can_id |= mod->modframe.or.can_id)
  MODFUNC(mod_or_dlc, cf->can_dlc |= mod->modframe.or.can_dlc)
  MODFUNC(mod_or_data, *(u64 *)cf->data |= *(u64 *)mod->modframe.or.data)
  MODFUNC(mod_xor_id, cf->can_id ^= mod->modframe.xor.can_id)
  MODFUNC(mod_xor_dlc, cf->can_dlc ^= mod->modframe.xor.can_dlc)
  MODFUNC(mod_xor_data, *(u64 *)cf->data ^= *(u64 *)mod->modframe.xor.data)
  MODFUNC(mod_set_id, cf->can_id = mod->modframe.set.can_id)
  MODFUNC(mod_set_dlc, cf->can_dlc = mod->modframe.set.can_dlc)
  MODFUNC(mod_set_data, *(u64 *)cf->data = *(u64 *)mod->modframe.set.data)
  
  static inline void canframecpy(struct can_frame *dst, struct can_frame *src)
  {
  	/*
  	 * Copy the struct members separately to ensure that no uninitialized
  	 * data are copied in the 3 bytes hole of the struct. This is needed
  	 * to make easy compares of the data in the struct cf_mod.
  	 */
  
  	dst->can_id = src->can_id;
  	dst->can_dlc = src->can_dlc;
  	*(u64 *)dst->data = *(u64 *)src->data;
  }
  
  static int cgw_chk_csum_parms(s8 fr, s8 to, s8 re)
  {
  	/*
  	 * absolute dlc values 0 .. 7 => 0 .. 7, e.g. data [0]
  	 * relative to received dlc -1 .. -8 :
  	 * e.g. for received dlc = 8
  	 * -1 => index = 7 (data[7])
  	 * -3 => index = 5 (data[5])
  	 * -8 => index = 0 (data[0])
  	 */
  
  	if (fr > -9 && fr < 8 &&
  	    to > -9 && to < 8 &&
  	    re > -9 && re < 8)
  		return 0;
  	else
  		return -EINVAL;
  }
  
  static inline int calc_idx(int idx, int rx_dlc)
  {
  	if (idx < 0)
  		return rx_dlc + idx;
  	else
  		return idx;
  }
  
  static void cgw_csum_xor_rel(struct can_frame *cf, struct cgw_csum_xor *xor)
  {
  	int from = calc_idx(xor->from_idx, cf->can_dlc);
  	int to = calc_idx(xor->to_idx, cf->can_dlc);
  	int res = calc_idx(xor->result_idx, cf->can_dlc);
  	u8 val = xor->init_xor_val;
  	int i;
  
  	if (from < 0 || to < 0 || res < 0)
  		return;
  
  	if (from <= to) {
  		for (i = from; i <= to; i++)
  			val ^= cf->data[i];
  	} else {
  		for (i = from; i >= to; i--)
  			val ^= cf->data[i];
  	}
  
  	cf->data[res] = val;
  }
  
  static void cgw_csum_xor_pos(struct can_frame *cf, struct cgw_csum_xor *xor)
  {
  	u8 val = xor->init_xor_val;
  	int i;
  
  	for (i = xor->from_idx; i <= xor->to_idx; i++)
  		val ^= cf->data[i];
  
  	cf->data[xor->result_idx] = val;
  }
  
  static void cgw_csum_xor_neg(struct can_frame *cf, struct cgw_csum_xor *xor)
  {
  	u8 val = xor->init_xor_val;
  	int i;
  
  	for (i = xor->from_idx; i >= xor->to_idx; i--)
  		val ^= cf->data[i];
  
  	cf->data[xor->result_idx] = val;
  }
  
  static void cgw_csum_crc8_rel(struct can_frame *cf, struct cgw_csum_crc8 *crc8)
  {
  	int from = calc_idx(crc8->from_idx, cf->can_dlc);
  	int to = calc_idx(crc8->to_idx, cf->can_dlc);
  	int res = calc_idx(crc8->result_idx, cf->can_dlc);
  	u8 crc = crc8->init_crc_val;
  	int i;
  
  	if (from < 0 || to < 0 || res < 0)
  		return;
  
  	if (from <= to) {
  		for (i = crc8->from_idx; i <= crc8->to_idx; i++)
  			crc = crc8->crctab[crc^cf->data[i]];
  	} else {
  		for (i = crc8->from_idx; i >= crc8->to_idx; i--)
  			crc = crc8->crctab[crc^cf->data[i]];
  	}
  
  	switch (crc8->profile) {
  
  	case CGW_CRC8PRF_1U8:
  		crc = crc8->crctab[crc^crc8->profile_data[0]];
  		break;
  
  	case  CGW_CRC8PRF_16U8:
  		crc = crc8->crctab[crc^crc8->profile_data[cf->data[1] & 0xF]];
  		break;
  
  	case CGW_CRC8PRF_SFFID_XOR:
  		crc = crc8->crctab[crc^(cf->can_id & 0xFF)^
  				   (cf->can_id >> 8 & 0xFF)];
  		break;
  
  	}
  
  	cf->data[crc8->result_idx] = crc^crc8->final_xor_val;
  }
  
  static void cgw_csum_crc8_pos(struct can_frame *cf, struct cgw_csum_crc8 *crc8)
  {
  	u8 crc = crc8->init_crc_val;
  	int i;
  
  	for (i = crc8->from_idx; i <= crc8->to_idx; i++)
  		crc = crc8->crctab[crc^cf->data[i]];
  
  	switch (crc8->profile) {
  
  	case CGW_CRC8PRF_1U8:
  		crc = crc8->crctab[crc^crc8->profile_data[0]];
  		break;
  
  	case  CGW_CRC8PRF_16U8:
  		crc = crc8->crctab[crc^crc8->profile_data[cf->data[1] & 0xF]];
  		break;
  
  	case CGW_CRC8PRF_SFFID_XOR:
  		crc = crc8->crctab[crc^(cf->can_id & 0xFF)^
  				   (cf->can_id >> 8 & 0xFF)];
  		break;
  	}
  
  	cf->data[crc8->result_idx] = crc^crc8->final_xor_val;
  }
  
  static void cgw_csum_crc8_neg(struct can_frame *cf, struct cgw_csum_crc8 *crc8)
  {
  	u8 crc = crc8->init_crc_val;
  	int i;
  
  	for (i = crc8->from_idx; i >= crc8->to_idx; i--)
  		crc = crc8->crctab[crc^cf->data[i]];
  
  	switch (crc8->profile) {
  
  	case CGW_CRC8PRF_1U8:
  		crc = crc8->crctab[crc^crc8->profile_data[0]];
  		break;
  
  	case  CGW_CRC8PRF_16U8:
  		crc = crc8->crctab[crc^crc8->profile_data[cf->data[1] & 0xF]];
  		break;
  
  	case CGW_CRC8PRF_SFFID_XOR:
  		crc = crc8->crctab[crc^(cf->can_id & 0xFF)^
  				   (cf->can_id >> 8 & 0xFF)];
  		break;
  	}
  
  	cf->data[crc8->result_idx] = crc^crc8->final_xor_val;
  }
  
  /* the receive & process & send function */
  static void can_can_gw_rcv(struct sk_buff *skb, void *data)
  {
  	struct cgw_job *gwj = (struct cgw_job *)data;
  	struct can_frame *cf;
  	struct sk_buff *nskb;
  	int modidx = 0;

  	/*
  	 * Do not handle CAN frames routed more than 'max_hops' times.
  	 * In general we should never catch this delimiter which is intended
  	 * to cover a misconfiguration protection (e.g. circular CAN routes).
  	 *
  	 * The Controller Area Network controllers only accept CAN frames with
  	 * correct CRCs - which are not visible in the controller registers.
  	 * According to skbuff.h documentation the csum_start element for IP

  	 * checksums is undefined/unused when ip_summed == CHECKSUM_UNNECESSARY.

  	 * Only CAN skbs can be processed here which already have this property.
  	 */
  
  #define cgw_hops(skb) ((skb)->csum_start)
  
  	BUG_ON(skb->ip_summed != CHECKSUM_UNNECESSARY);

  	if (cgw_hops(skb) >= max_hops) {
  		/* indicate deleted frames due to misconfiguration */
  		gwj->deleted_frames++;

  		return;

  	}

  
  	if (!(gwj->dst.dev->flags & IFF_UP)) {
  		gwj->dropped_frames++;
  		return;
  	}

  	/* is sending the skb back to the incoming interface not allowed? */
  	if (!(gwj->flags & CGW_FLAGS_CAN_IIF_TX_OK) &&

  	    can_skb_prv(skb)->ifindex == gwj->dst.dev->ifindex)

  		return;

  	/*
  	 * clone the given skb, which has not been done in can_rcv()
  	 *
  	 * When there is at least one modification function activated,
  	 * we need to copy the skb as we want to modify skb->data.
  	 */
  	if (gwj->mod.modfunc[0])
  		nskb = skb_copy(skb, GFP_ATOMIC);
  	else
  		nskb = skb_clone(skb, GFP_ATOMIC);
  
  	if (!nskb) {
  		gwj->dropped_frames++;
  		return;
  	}

  	/* put the incremented hop counter in the cloned skb */
  	cgw_hops(nskb) = cgw_hops(skb) + 1;

  
  	/* first processing of this CAN frame -> adjust to private hop limit */
  	if (gwj->limit_hops && cgw_hops(nskb) == 1)
  		cgw_hops(nskb) = max_hops - gwj->limit_hops + 1;

  	nskb->dev = gwj->dst.dev;
  
  	/* pointer to modifiable CAN frame */
  	cf = (struct can_frame *)nskb->data;
  
  	/* perform preprocessed modification functions if there are any */
  	while (modidx < MAX_MODFUNCTIONS && gwj->mod.modfunc[modidx])
  		(*gwj->mod.modfunc[modidx++])(cf, &gwj->mod);
  
  	/* check for checksum updates when the CAN frame has been modified */
  	if (modidx) {
  		if (gwj->mod.csumfunc.crc8)
  			(*gwj->mod.csumfunc.crc8)(cf, &gwj->mod.csum.crc8);
  
  		if (gwj->mod.csumfunc.xor)
  			(*gwj->mod.csumfunc.xor)(cf, &gwj->mod.csum.xor);
  	}
  
  	/* clear the skb timestamp if not configured the other way */
  	if (!(gwj->flags & CGW_FLAGS_CAN_SRC_TSTAMP))
  		nskb->tstamp.tv64 = 0;
  
  	/* send to netdevice */
  	if (can_send(nskb, gwj->flags & CGW_FLAGS_CAN_ECHO))
  		gwj->dropped_frames++;
  	else
  		gwj->handled_frames++;
  }
  
  static inline int cgw_register_filter(struct cgw_job *gwj)
  {
  	return can_rx_register(gwj->src.dev, gwj->ccgw.filter.can_id,
  			       gwj->ccgw.filter.can_mask, can_can_gw_rcv,

  			       gwj, "gw", NULL);

  }
  
  static inline void cgw_unregister_filter(struct cgw_job *gwj)
  {
  	can_rx_unregister(gwj->src.dev, gwj->ccgw.filter.can_id,
  			  gwj->ccgw.filter.can_mask, can_can_gw_rcv, gwj);
  }
  
  static int cgw_notifier(struct notifier_block *nb,

  			unsigned long msg, void *ptr)

  {

  	struct net_device *dev = netdev_notifier_info_to_dev(ptr);

  
  	if (!net_eq(dev_net(dev), &init_net))
  		return NOTIFY_DONE;
  	if (dev->type != ARPHRD_CAN)
  		return NOTIFY_DONE;
  
  	if (msg == NETDEV_UNREGISTER) {
  
  		struct cgw_job *gwj = NULL;

  		struct hlist_node *nx;

  
  		ASSERT_RTNL();

  		hlist_for_each_entry_safe(gwj, nx, &cgw_list, list) {

  
  			if (gwj->src.dev == dev || gwj->dst.dev == dev) {
  				hlist_del(&gwj->list);
  				cgw_unregister_filter(gwj);

  				kmem_cache_free(cgw_cache, gwj);

  			}
  		}
  	}
  
  	return NOTIFY_DONE;
  }

  static int cgw_put_job(struct sk_buff *skb, struct cgw_job *gwj, int type,
  		       u32 pid, u32 seq, int flags)

  {
  	struct cgw_frame_mod mb;
  	struct rtcanmsg *rtcan;

  	struct nlmsghdr *nlh;
  
  	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*rtcan), flags);

  	if (!nlh)
  		return -EMSGSIZE;
  
  	rtcan = nlmsg_data(nlh);
  	rtcan->can_family = AF_CAN;
  	rtcan->gwtype = gwj->gwtype;
  	rtcan->flags = gwj->flags;
  
  	/* add statistics if available */
  
  	if (gwj->handled_frames) {
  		if (nla_put_u32(skb, CGW_HANDLED, gwj->handled_frames) < 0)
  			goto cancel;

  	}
  
  	if (gwj->dropped_frames) {
  		if (nla_put_u32(skb, CGW_DROPPED, gwj->dropped_frames) < 0)
  			goto cancel;

  	}

  	if (gwj->deleted_frames) {
  		if (nla_put_u32(skb, CGW_DELETED, gwj->deleted_frames) < 0)
  			goto cancel;
  	}

  	/* check non default settings of attributes */

  	if (gwj->limit_hops) {
  		if (nla_put_u8(skb, CGW_LIM_HOPS, gwj->limit_hops) < 0)
  			goto cancel;
  	}

  	if (gwj->mod.modtype.and) {
  		memcpy(&mb.cf, &gwj->mod.modframe.and, sizeof(mb.cf));
  		mb.modtype = gwj->mod.modtype.and;
  		if (nla_put(skb, CGW_MOD_AND, sizeof(mb), &mb) < 0)
  			goto cancel;

  	}
  
  	if (gwj->mod.modtype.or) {
  		memcpy(&mb.cf, &gwj->mod.modframe.or, sizeof(mb.cf));
  		mb.modtype = gwj->mod.modtype.or;
  		if (nla_put(skb, CGW_MOD_OR, sizeof(mb), &mb) < 0)
  			goto cancel;

  	}
  
  	if (gwj->mod.modtype.xor) {
  		memcpy(&mb.cf, &gwj->mod.modframe.xor, sizeof(mb.cf));
  		mb.modtype = gwj->mod.modtype.xor;
  		if (nla_put(skb, CGW_MOD_XOR, sizeof(mb), &mb) < 0)
  			goto cancel;

  	}
  
  	if (gwj->mod.modtype.set) {
  		memcpy(&mb.cf, &gwj->mod.modframe.set, sizeof(mb.cf));
  		mb.modtype = gwj->mod.modtype.set;
  		if (nla_put(skb, CGW_MOD_SET, sizeof(mb), &mb) < 0)
  			goto cancel;

  	}

  	if (gwj->mod.uid) {
  		if (nla_put_u32(skb, CGW_MOD_UID, gwj->mod.uid) < 0)
  			goto cancel;
  	}

  	if (gwj->mod.csumfunc.crc8) {
  		if (nla_put(skb, CGW_CS_CRC8, CGW_CS_CRC8_LEN,
  			    &gwj->mod.csum.crc8) < 0)
  			goto cancel;

  	}
  
  	if (gwj->mod.csumfunc.xor) {
  		if (nla_put(skb, CGW_CS_XOR, CGW_CS_XOR_LEN,
  			    &gwj->mod.csum.xor) < 0)
  			goto cancel;

  	}
  
  	if (gwj->gwtype == CGW_TYPE_CAN_CAN) {
  
  		if (gwj->ccgw.filter.can_id || gwj->ccgw.filter.can_mask) {
  			if (nla_put(skb, CGW_FILTER, sizeof(struct can_filter),
  				    &gwj->ccgw.filter) < 0)
  				goto cancel;

  		}
  
  		if (nla_put_u32(skb, CGW_SRC_IF, gwj->ccgw.src_idx) < 0)
  			goto cancel;

  
  		if (nla_put_u32(skb, CGW_DST_IF, gwj->ccgw.dst_idx) < 0)
  			goto cancel;

  	}

  	nlmsg_end(skb, nlh);
  	return 0;

  
  cancel:
  	nlmsg_cancel(skb, nlh);
  	return -EMSGSIZE;
  }
  
  /* Dump information about all CAN gateway jobs, in response to RTM_GETROUTE */
  static int cgw_dump_jobs(struct sk_buff *skb, struct netlink_callback *cb)
  {
  	struct cgw_job *gwj = NULL;

  	int idx = 0;
  	int s_idx = cb->args[0];
  
  	rcu_read_lock();

  	hlist_for_each_entry_rcu(gwj, &cgw_list, list) {

  		if (idx < s_idx)
  			goto cont;

  		if (cgw_put_job(skb, gwj, RTM_NEWROUTE, NETLINK_CB(cb->skb).portid,

  		    cb->nlh->nlmsg_seq, NLM_F_MULTI) < 0)

  			break;
  cont:
  		idx++;
  	}
  	rcu_read_unlock();
  
  	cb->args[0] = idx;
  
  	return skb->len;
  }

  static const struct nla_policy cgw_policy[CGW_MAX+1] = {
  	[CGW_MOD_AND]	= { .len = sizeof(struct cgw_frame_mod) },
  	[CGW_MOD_OR]	= { .len = sizeof(struct cgw_frame_mod) },
  	[CGW_MOD_XOR]	= { .len = sizeof(struct cgw_frame_mod) },
  	[CGW_MOD_SET]	= { .len = sizeof(struct cgw_frame_mod) },
  	[CGW_CS_XOR]	= { .len = sizeof(struct cgw_csum_xor) },
  	[CGW_CS_CRC8]	= { .len = sizeof(struct cgw_csum_crc8) },
  	[CGW_SRC_IF]	= { .type = NLA_U32 },
  	[CGW_DST_IF]	= { .type = NLA_U32 },
  	[CGW_FILTER]	= { .len = sizeof(struct can_filter) },

  	[CGW_LIM_HOPS]	= { .type = NLA_U8 },

  	[CGW_MOD_UID]	= { .type = NLA_U32 },

  };

  /* check for common and gwtype specific attributes */
  static int cgw_parse_attr(struct nlmsghdr *nlh, struct cf_mod *mod,

  			  u8 gwtype, void *gwtypeattr, u8 *limhops)

  {
  	struct nlattr *tb[CGW_MAX+1];
  	struct cgw_frame_mod mb;
  	int modidx = 0;
  	int err = 0;
  
  	/* initialize modification & checksum data space */
  	memset(mod, 0, sizeof(*mod));

  	err = nlmsg_parse(nlh, sizeof(struct rtcanmsg), tb, CGW_MAX,
  			  cgw_policy);

  	if (err < 0)
  		return err;

  	if (tb[CGW_LIM_HOPS]) {
  		*limhops = nla_get_u8(tb[CGW_LIM_HOPS]);
  
  		if (*limhops < 1 || *limhops > max_hops)
  			return -EINVAL;
  	}

  	/* check for AND/OR/XOR/SET modifications */

  	if (tb[CGW_MOD_AND]) {

  		nla_memcpy(&mb, tb[CGW_MOD_AND], CGW_MODATTR_LEN);
  
  		canframecpy(&mod->modframe.and, &mb.cf);
  		mod->modtype.and = mb.modtype;
  
  		if (mb.modtype & CGW_MOD_ID)
  			mod->modfunc[modidx++] = mod_and_id;
  
  		if (mb.modtype & CGW_MOD_DLC)
  			mod->modfunc[modidx++] = mod_and_dlc;
  
  		if (mb.modtype & CGW_MOD_DATA)
  			mod->modfunc[modidx++] = mod_and_data;
  	}

  	if (tb[CGW_MOD_OR]) {

  		nla_memcpy(&mb, tb[CGW_MOD_OR], CGW_MODATTR_LEN);
  
  		canframecpy(&mod->modframe.or, &mb.cf);
  		mod->modtype.or = mb.modtype;
  
  		if (mb.modtype & CGW_MOD_ID)
  			mod->modfunc[modidx++] = mod_or_id;
  
  		if (mb.modtype & CGW_MOD_DLC)
  			mod->modfunc[modidx++] = mod_or_dlc;
  
  		if (mb.modtype & CGW_MOD_DATA)
  			mod->modfunc[modidx++] = mod_or_data;
  	}

  	if (tb[CGW_MOD_XOR]) {

  		nla_memcpy(&mb, tb[CGW_MOD_XOR], CGW_MODATTR_LEN);
  
  		canframecpy(&mod->modframe.xor, &mb.cf);
  		mod->modtype.xor = mb.modtype;
  
  		if (mb.modtype & CGW_MOD_ID)
  			mod->modfunc[modidx++] = mod_xor_id;
  
  		if (mb.modtype & CGW_MOD_DLC)
  			mod->modfunc[modidx++] = mod_xor_dlc;
  
  		if (mb.modtype & CGW_MOD_DATA)
  			mod->modfunc[modidx++] = mod_xor_data;
  	}

  	if (tb[CGW_MOD_SET]) {

  		nla_memcpy(&mb, tb[CGW_MOD_SET], CGW_MODATTR_LEN);
  
  		canframecpy(&mod->modframe.set, &mb.cf);
  		mod->modtype.set = mb.modtype;
  
  		if (mb.modtype & CGW_MOD_ID)
  			mod->modfunc[modidx++] = mod_set_id;
  
  		if (mb.modtype & CGW_MOD_DLC)
  			mod->modfunc[modidx++] = mod_set_dlc;
  
  		if (mb.modtype & CGW_MOD_DATA)
  			mod->modfunc[modidx++] = mod_set_data;
  	}
  
  	/* check for checksum operations after CAN frame modifications */
  	if (modidx) {

  		if (tb[CGW_CS_CRC8]) {

  			struct cgw_csum_crc8 *c = nla_data(tb[CGW_CS_CRC8]);

  
  			err = cgw_chk_csum_parms(c->from_idx, c->to_idx,
  						 c->result_idx);
  			if (err)
  				return err;
  
  			nla_memcpy(&mod->csum.crc8, tb[CGW_CS_CRC8],
  				   CGW_CS_CRC8_LEN);
  
  			/*
  			 * select dedicated processing function to reduce
  			 * runtime operations in receive hot path.
  			 */
  			if (c->from_idx < 0 || c->to_idx < 0 ||
  			    c->result_idx < 0)
  				mod->csumfunc.crc8 = cgw_csum_crc8_rel;
  			else if (c->from_idx <= c->to_idx)
  				mod->csumfunc.crc8 = cgw_csum_crc8_pos;
  			else
  				mod->csumfunc.crc8 = cgw_csum_crc8_neg;
  		}

  		if (tb[CGW_CS_XOR]) {

  			struct cgw_csum_xor *c = nla_data(tb[CGW_CS_XOR]);

  
  			err = cgw_chk_csum_parms(c->from_idx, c->to_idx,
  						 c->result_idx);
  			if (err)
  				return err;
  
  			nla_memcpy(&mod->csum.xor, tb[CGW_CS_XOR],
  				   CGW_CS_XOR_LEN);
  
  			/*
  			 * select dedicated processing function to reduce
  			 * runtime operations in receive hot path.
  			 */
  			if (c->from_idx < 0 || c->to_idx < 0 ||
  			    c->result_idx < 0)
  				mod->csumfunc.xor = cgw_csum_xor_rel;
  			else if (c->from_idx <= c->to_idx)
  				mod->csumfunc.xor = cgw_csum_xor_pos;
  			else
  				mod->csumfunc.xor = cgw_csum_xor_neg;
  		}

  
  		if (tb[CGW_MOD_UID]) {
  			nla_memcpy(&mod->uid, tb[CGW_MOD_UID], sizeof(u32));
  		}

  	}
  
  	if (gwtype == CGW_TYPE_CAN_CAN) {
  
  		/* check CGW_TYPE_CAN_CAN specific attributes */
  
  		struct can_can_gw *ccgw = (struct can_can_gw *)gwtypeattr;
  		memset(ccgw, 0, sizeof(*ccgw));
  
  		/* check for can_filter in attributes */

  		if (tb[CGW_FILTER])

  			nla_memcpy(&ccgw->filter, tb[CGW_FILTER],
  				   sizeof(struct can_filter));
  
  		err = -ENODEV;
  
  		/* specifying two interfaces is mandatory */
  		if (!tb[CGW_SRC_IF] || !tb[CGW_DST_IF])
  			return err;

  		ccgw->src_idx = nla_get_u32(tb[CGW_SRC_IF]);
  		ccgw->dst_idx = nla_get_u32(tb[CGW_DST_IF]);

  
  		/* both indices set to 0 for flushing all routing entries */
  		if (!ccgw->src_idx && !ccgw->dst_idx)
  			return 0;
  
  		/* only one index set to 0 is an error */
  		if (!ccgw->src_idx || !ccgw->dst_idx)
  			return err;
  	}
  
  	/* add the checks for other gwtypes here */
  
  	return 0;
  }

  static int cgw_create_job(struct sk_buff *skb,  struct nlmsghdr *nlh)

  {
  	struct rtcanmsg *r;
  	struct cgw_job *gwj;

  	struct cf_mod mod;
  	struct can_can_gw ccgw;

  	u8 limhops = 0;

  	int err = 0;

  	if (!netlink_capable(skb, CAP_NET_ADMIN))

  		return -EPERM;

  	if (nlmsg_len(nlh) < sizeof(*r))
  		return -EINVAL;
  
  	r = nlmsg_data(nlh);
  	if (r->can_family != AF_CAN)
  		return -EPFNOSUPPORT;
  
  	/* so far we only support CAN -> CAN routings */
  	if (r->gwtype != CGW_TYPE_CAN_CAN)
  		return -EINVAL;

  	err = cgw_parse_attr(nlh, &mod, CGW_TYPE_CAN_CAN, &ccgw, &limhops);
  	if (err < 0)
  		return err;
  
  	if (mod.uid) {
  
  		ASSERT_RTNL();
  
  		/* check for updating an existing job with identical uid */
  		hlist_for_each_entry(gwj, &cgw_list, list) {
  
  			if (gwj->mod.uid != mod.uid)
  				continue;
  
  			/* interfaces & filters must be identical */
  			if (memcmp(&gwj->ccgw, &ccgw, sizeof(ccgw)))
  				return -EINVAL;
  
  			/* update modifications with disabled softirq & quit */
  			local_bh_disable();
  			memcpy(&gwj->mod, &mod, sizeof(mod));
  			local_bh_enable();
  			return 0;
  		}
  	}
  
  	/* ifindex == 0 is not allowed for job creation */
  	if (!ccgw.src_idx || !ccgw.dst_idx)
  		return -ENODEV;

  	gwj = kmem_cache_alloc(cgw_cache, GFP_KERNEL);
  	if (!gwj)
  		return -ENOMEM;
  
  	gwj->handled_frames = 0;
  	gwj->dropped_frames = 0;

  	gwj->deleted_frames = 0;

  	gwj->flags = r->flags;
  	gwj->gwtype = r->gwtype;

  	gwj->limit_hops = limhops;

  	/* insert already parsed information */
  	memcpy(&gwj->mod, &mod, sizeof(mod));
  	memcpy(&gwj->ccgw, &ccgw, sizeof(ccgw));

  
  	err = -ENODEV;

  	gwj->src.dev = __dev_get_by_index(&init_net, gwj->ccgw.src_idx);

  
  	if (!gwj->src.dev)
  		goto out;

  	if (gwj->src.dev->type != ARPHRD_CAN)

  		goto out;

  	gwj->dst.dev = __dev_get_by_index(&init_net, gwj->ccgw.dst_idx);

  
  	if (!gwj->dst.dev)

  		goto out;

  	if (gwj->dst.dev->type != ARPHRD_CAN)

  		goto out;

  
  	ASSERT_RTNL();
  
  	err = cgw_register_filter(gwj);
  	if (!err)
  		hlist_add_head_rcu(&gwj->list, &cgw_list);

  out:
  	if (err)
  		kmem_cache_free(cgw_cache, gwj);
  
  	return err;
  }
  
  static void cgw_remove_all_jobs(void)
  {
  	struct cgw_job *gwj = NULL;

  	struct hlist_node *nx;

  
  	ASSERT_RTNL();

  	hlist_for_each_entry_safe(gwj, nx, &cgw_list, list) {

  		hlist_del(&gwj->list);
  		cgw_unregister_filter(gwj);

  		kmem_cache_free(cgw_cache, gwj);

  	}
  }

  static int cgw_remove_job(struct sk_buff *skb, struct nlmsghdr *nlh)

  {
  	struct cgw_job *gwj = NULL;

  	struct hlist_node *nx;

  	struct rtcanmsg *r;
  	struct cf_mod mod;
  	struct can_can_gw ccgw;

  	u8 limhops = 0;

  	int err = 0;

  	if (!netlink_capable(skb, CAP_NET_ADMIN))

  		return -EPERM;

  	if (nlmsg_len(nlh) < sizeof(*r))
  		return -EINVAL;
  
  	r = nlmsg_data(nlh);
  	if (r->can_family != AF_CAN)
  		return -EPFNOSUPPORT;
  
  	/* so far we only support CAN -> CAN routings */
  	if (r->gwtype != CGW_TYPE_CAN_CAN)
  		return -EINVAL;

  	err = cgw_parse_attr(nlh, &mod, CGW_TYPE_CAN_CAN, &ccgw, &limhops);

  	if (err < 0)
  		return err;
  
  	/* two interface indices both set to 0 => remove all entries */
  	if (!ccgw.src_idx && !ccgw.dst_idx) {
  		cgw_remove_all_jobs();
  		return 0;
  	}
  
  	err = -EINVAL;
  
  	ASSERT_RTNL();
  
  	/* remove only the first matching entry */

  	hlist_for_each_entry_safe(gwj, nx, &cgw_list, list) {

  
  		if (gwj->flags != r->flags)
  			continue;

  		if (gwj->limit_hops != limhops)
  			continue;

  		/* we have a match when uid is enabled and identical */
  		if (gwj->mod.uid || mod.uid) {
  			if (gwj->mod.uid != mod.uid)
  				continue;
  		} else {
  			/* no uid => check for identical modifications */
  			if (memcmp(&gwj->mod, &mod, sizeof(mod)))
  				continue;
  		}

  
  		/* if (r->gwtype == CGW_TYPE_CAN_CAN) - is made sure here */
  		if (memcmp(&gwj->ccgw, &ccgw, sizeof(ccgw)))
  			continue;
  
  		hlist_del(&gwj->list);
  		cgw_unregister_filter(gwj);

  		kmem_cache_free(cgw_cache, gwj);

  		err = 0;
  		break;
  	}
  
  	return err;
  }
  
  static __init int cgw_module_init(void)
  {

  	/* sanitize given module parameter */
  	max_hops = clamp_t(unsigned int, max_hops, CGW_MIN_HOPS, CGW_MAX_HOPS);
  
  	pr_info("can: netlink gateway (rev " CAN_GW_VERSION ") max_hops=%d
  ",
  		max_hops);

  
  	cgw_cache = kmem_cache_create("can_gw", sizeof(struct cgw_job),
  				      0, 0, NULL);
  
  	if (!cgw_cache)
  		return -ENOMEM;
  
  	/* set notifier */
  	notifier.notifier_call = cgw_notifier;
  	register_netdevice_notifier(&notifier);
  
  	if (__rtnl_register(PF_CAN, RTM_GETROUTE, NULL, cgw_dump_jobs, NULL)) {
  		unregister_netdevice_notifier(&notifier);
  		kmem_cache_destroy(cgw_cache);
  		return -ENOBUFS;
  	}
  
  	/* Only the first call to __rtnl_register can fail */
  	__rtnl_register(PF_CAN, RTM_NEWROUTE, cgw_create_job, NULL, NULL);
  	__rtnl_register(PF_CAN, RTM_DELROUTE, cgw_remove_job, NULL, NULL);
  
  	return 0;
  }
  
  static __exit void cgw_module_exit(void)
  {
  	rtnl_unregister_all(PF_CAN);
  
  	unregister_netdevice_notifier(&notifier);
  
  	rtnl_lock();
  	cgw_remove_all_jobs();
  	rtnl_unlock();
  
  	rcu_barrier(); /* Wait for completion of call_rcu()'s */
  
  	kmem_cache_destroy(cgw_cache);
  }
  
  module_init(cgw_module_init);
  module_exit(cgw_module_exit);