net/batman-adv/gateway_client.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (C) B.A.T.M.A.N. contributors:
  *
  * Marek Lindner
  */

 #include "gateway_client.h"
 #include "main.h"

 #include <linux/atomic.h>
 #include <linux/byteorder/generic.h>
 #include <linux/errno.h>
 #include <linux/etherdevice.h>
 #include <linux/gfp.h>
 #include <linux/if_ether.h>
 #include <linux/if_vlan.h>
 #include <linux/in.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/kernel.h>
 #include <linux/kref.h>
 #include <linux/list.h>
 #include <linux/lockdep.h>
 #include <linux/netdevice.h>
 #include <linux/netlink.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
 #include <linux/skbuff.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/stddef.h>
 #include <linux/udp.h>
 #include <net/sock.h>
 #include <uapi/linux/batadv_packet.h>
 #include <uapi/linux/batman_adv.h>

 #include "hard-interface.h"
 #include "log.h"
 #include "netlink.h"
 #include "originator.h"
 #include "routing.h"
 #include "soft-interface.h"
 #include "translation-table.h"

 /* These are the offsets of the "hw type" and "hw address length" in the dhcp
  * packet starting at the beginning of the dhcp header
  */
 #define BATADV_DHCP_HTYPE_OFFSET	1
 #define BATADV_DHCP_HLEN_OFFSET		2
 /* Value of htype representing Ethernet */
 #define BATADV_DHCP_HTYPE_ETHERNET	0x01
 /* This is the offset of the "chaddr" field in the dhcp packet starting at the
  * beginning of the dhcp header
  */
 #define BATADV_DHCP_CHADDR_OFFSET	28

 /**
  * batadv_gw_node_release() - release gw_node from lists and queue for free
  *  after rcu grace period
  * @ref: kref pointer of the gw_node
  */
 void batadv_gw_node_release(struct kref *ref)
 {
 	struct batadv_gw_node *gw_node;

 	gw_node = container_of(ref, struct batadv_gw_node, refcount);

 	batadv_orig_node_put(gw_node->orig_node);
 	kfree_rcu(gw_node, rcu);
 }

 /**
  * batadv_gw_get_selected_gw_node() - Get currently selected gateway
  * @bat_priv: the bat priv with all the soft interface information
  *
  * Return: selected gateway (with increased refcnt), NULL on errors
  */
 struct batadv_gw_node *
 batadv_gw_get_selected_gw_node(struct batadv_priv *bat_priv)
 {
 	struct batadv_gw_node *gw_node;

 	rcu_read_lock();
 	gw_node = rcu_dereference(bat_priv->gw.curr_gw);
 	if (!gw_node)
 		goto out;

 	if (!kref_get_unless_zero(&gw_node->refcount))
 		gw_node = NULL;

 out:
 	rcu_read_unlock();
 	return gw_node;
 }

 /**
  * batadv_gw_get_selected_orig() - Get originator of currently selected gateway
  * @bat_priv: the bat priv with all the soft interface information
  *
  * Return: orig_node of selected gateway (with increased refcnt), NULL on errors
  */
 struct batadv_orig_node *
 batadv_gw_get_selected_orig(struct batadv_priv *bat_priv)
 {
 	struct batadv_gw_node *gw_node;
 	struct batadv_orig_node *orig_node = NULL;

 	gw_node = batadv_gw_get_selected_gw_node(bat_priv);
 	if (!gw_node)
 		goto out;

 	rcu_read_lock();
 	orig_node = gw_node->orig_node;
 	if (!orig_node)
 		goto unlock;

 	if (!kref_get_unless_zero(&orig_node->refcount))
 		orig_node = NULL;

 unlock:
 	rcu_read_unlock();
 out:
 	batadv_gw_node_put(gw_node);
 	return orig_node;
 }

 static void batadv_gw_select(struct batadv_priv *bat_priv,
 			     struct batadv_gw_node *new_gw_node)
 {
 	struct batadv_gw_node *curr_gw_node;

 	spin_lock_bh(&bat_priv->gw.list_lock);

 	if (new_gw_node)
 		kref_get(&new_gw_node->refcount);

 	curr_gw_node = rcu_replace_pointer(bat_priv->gw.curr_gw, new_gw_node,
 					   true);

 	batadv_gw_node_put(curr_gw_node);

 	spin_unlock_bh(&bat_priv->gw.list_lock);
 }

 /**
  * batadv_gw_reselect() - force a gateway reselection
  * @bat_priv: the bat priv with all the soft interface information
  *
  * Set a flag to remind the GW component to perform a new gateway reselection.
  * However this function does not ensure that the current gateway is going to be
  * deselected. The reselection mechanism may elect the same gateway once again.
  *
  * This means that invoking batadv_gw_reselect() does not guarantee a gateway
  * change and therefore a uevent is not necessarily expected.
  */
 void batadv_gw_reselect(struct batadv_priv *bat_priv)
 {
 	atomic_set(&bat_priv->gw.reselect, 1);
 }

 /**
  * batadv_gw_check_client_stop() - check if client mode has been switched off
  * @bat_priv: the bat priv with all the soft interface information
  *
  * This function assumes the caller has checked that the gw state *is actually
  * changing*. This function is not supposed to be called when there is no state
  * change.
  */
 void batadv_gw_check_client_stop(struct batadv_priv *bat_priv)
 {
 	struct batadv_gw_node *curr_gw;

 	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
 		return;

 	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 	if (!curr_gw)
 		return;

 	/* deselect the current gateway so that next time that client mode is
 	 * enabled a proper GW_ADD event can be sent
 	 */
 	batadv_gw_select(bat_priv, NULL);

 	/* if batman-adv is switching the gw client mode off and a gateway was
 	 * already selected, send a DEL uevent
 	 */
 	batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL, NULL);

 	batadv_gw_node_put(curr_gw);
 }

 /**
  * batadv_gw_election() - Elect the best gateway
  * @bat_priv: the bat priv with all the soft interface information
  */
 void batadv_gw_election(struct batadv_priv *bat_priv)
 {
 	struct batadv_gw_node *curr_gw = NULL;
 	struct batadv_gw_node *next_gw = NULL;
 	struct batadv_neigh_node *router = NULL;
 	struct batadv_neigh_ifinfo *router_ifinfo = NULL;
 	char gw_addr[18] = { '\0' };

 	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
 		goto out;

 	if (!bat_priv->algo_ops->gw.get_best_gw_node)
 		goto out;

 	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);

 	if (!batadv_atomic_dec_not_zero(&bat_priv->gw.reselect) && curr_gw)
 		goto out;

 	/* if gw.reselect is set to 1 it means that a previous call to
 	 * gw.is_eligible() said that we have a new best GW, therefore it can
 	 * now be picked from the list and selected
 	 */
 	next_gw = bat_priv->algo_ops->gw.get_best_gw_node(bat_priv);

 	if (curr_gw == next_gw)
 		goto out;

 	if (next_gw) {
 		sprintf(gw_addr, "%pM", next_gw->orig_node->orig);

 		router = batadv_orig_router_get(next_gw->orig_node,
 						BATADV_IF_DEFAULT);
 		if (!router) {
 			batadv_gw_reselect(bat_priv);
 			goto out;
 		}

 		router_ifinfo = batadv_neigh_ifinfo_get(router,
 							BATADV_IF_DEFAULT);
 		if (!router_ifinfo) {
 			batadv_gw_reselect(bat_priv);
 			goto out;
 		}
 	}

 	if (curr_gw && !next_gw) {
 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 			   "Removing selected gateway - no gateway in range\n");
 		batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL,
 				    NULL);
 	} else if (!curr_gw && next_gw) {
 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 			   "Adding route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
 			   next_gw->orig_node->orig,
 			   next_gw->bandwidth_down / 10,
 			   next_gw->bandwidth_down % 10,
 			   next_gw->bandwidth_up / 10,
 			   next_gw->bandwidth_up % 10,
 			   router_ifinfo->bat_iv.tq_avg);
 		batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_ADD,
 				    gw_addr);
 	} else {
 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 			   "Changing route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
 			   next_gw->orig_node->orig,
 			   next_gw->bandwidth_down / 10,
 			   next_gw->bandwidth_down % 10,
 			   next_gw->bandwidth_up / 10,
 			   next_gw->bandwidth_up % 10,
 			   router_ifinfo->bat_iv.tq_avg);
 		batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_CHANGE,
 				    gw_addr);
 	}

 	batadv_gw_select(bat_priv, next_gw);

 out:
 	batadv_gw_node_put(curr_gw);
 	batadv_gw_node_put(next_gw);
 	batadv_neigh_node_put(router);
 	batadv_neigh_ifinfo_put(router_ifinfo);
 }

 /**
  * batadv_gw_check_election() - Elect orig node as best gateway when eligible
  * @bat_priv: the bat priv with all the soft interface information
  * @orig_node: orig node which is to be checked
  */
 void batadv_gw_check_election(struct batadv_priv *bat_priv,
 			      struct batadv_orig_node *orig_node)
 {
 	struct batadv_orig_node *curr_gw_orig;

 	/* abort immediately if the routing algorithm does not support gateway
 	 * election
 	 */
 	if (!bat_priv->algo_ops->gw.is_eligible)
 		return;

 	curr_gw_orig = batadv_gw_get_selected_orig(bat_priv);
 	if (!curr_gw_orig)
 		goto reselect;

 	/* this node already is the gateway */
 	if (curr_gw_orig == orig_node)
 		goto out;

 	if (!bat_priv->algo_ops->gw.is_eligible(bat_priv, curr_gw_orig,
 						orig_node))
 		goto out;

 reselect:
 	batadv_gw_reselect(bat_priv);
 out:
 	batadv_orig_node_put(curr_gw_orig);
 }

 /**
  * batadv_gw_node_add() - add gateway node to list of available gateways
  * @bat_priv: the bat priv with all the soft interface information
  * @orig_node: originator announcing gateway capabilities
  * @gateway: announced bandwidth information
  *
  * Has to be called with the appropriate locks being acquired
  * (gw.list_lock).
  */
 static void batadv_gw_node_add(struct batadv_priv *bat_priv,
 			       struct batadv_orig_node *orig_node,
 			       struct batadv_tvlv_gateway_data *gateway)
 {
 	struct batadv_gw_node *gw_node;

 	lockdep_assert_held(&bat_priv->gw.list_lock);

 	if (gateway->bandwidth_down == 0)
 		return;

 	gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
 	if (!gw_node)
 		return;

 	kref_init(&gw_node->refcount);
 	INIT_HLIST_NODE(&gw_node->list);
 	kref_get(&orig_node->refcount);
 	gw_node->orig_node = orig_node;
 	gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
 	gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);

 	kref_get(&gw_node->refcount);
 	hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.gateway_list);
 	bat_priv->gw.generation++;

 	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 		   "Found new gateway %pM -> gw bandwidth: %u.%u/%u.%u MBit\n",
 		   orig_node->orig,
 		   ntohl(gateway->bandwidth_down) / 10,
 		   ntohl(gateway->bandwidth_down) % 10,
 		   ntohl(gateway->bandwidth_up) / 10,
 		   ntohl(gateway->bandwidth_up) % 10);

 	/* don't return reference to new gw_node */
 	batadv_gw_node_put(gw_node);
 }

 /**
  * batadv_gw_node_get() - retrieve gateway node from list of available gateways
  * @bat_priv: the bat priv with all the soft interface information
  * @orig_node: originator announcing gateway capabilities
  *
  * Return: gateway node if found or NULL otherwise.
  */
 struct batadv_gw_node *batadv_gw_node_get(struct batadv_priv *bat_priv,
 					  struct batadv_orig_node *orig_node)
 {
 	struct batadv_gw_node *gw_node_tmp, *gw_node = NULL;

 	rcu_read_lock();
 	hlist_for_each_entry_rcu(gw_node_tmp, &bat_priv->gw.gateway_list,
 				 list) {
 		if (gw_node_tmp->orig_node != orig_node)
 			continue;

 		if (!kref_get_unless_zero(&gw_node_tmp->refcount))
 			continue;

 		gw_node = gw_node_tmp;
 		break;
 	}
 	rcu_read_unlock();

 	return gw_node;
 }

 /**
  * batadv_gw_node_update() - update list of available gateways with changed
  *  bandwidth information
  * @bat_priv: the bat priv with all the soft interface information
  * @orig_node: originator announcing gateway capabilities
  * @gateway: announced bandwidth information
  */
 void batadv_gw_node_update(struct batadv_priv *bat_priv,
 			   struct batadv_orig_node *orig_node,
 			   struct batadv_tvlv_gateway_data *gateway)
 {
 	struct batadv_gw_node *gw_node, *curr_gw = NULL;

 	spin_lock_bh(&bat_priv->gw.list_lock);
 	gw_node = batadv_gw_node_get(bat_priv, orig_node);
 	if (!gw_node) {
 		batadv_gw_node_add(bat_priv, orig_node, gateway);
 		spin_unlock_bh(&bat_priv->gw.list_lock);
 		goto out;
 	}
 	spin_unlock_bh(&bat_priv->gw.list_lock);

 	if (gw_node->bandwidth_down == ntohl(gateway->bandwidth_down) &&
 	    gw_node->bandwidth_up == ntohl(gateway->bandwidth_up))
 		goto out;

 	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 		   "Gateway bandwidth of originator %pM changed from %u.%u/%u.%u MBit to %u.%u/%u.%u MBit\n",
 		   orig_node->orig,
 		   gw_node->bandwidth_down / 10,
 		   gw_node->bandwidth_down % 10,
 		   gw_node->bandwidth_up / 10,
 		   gw_node->bandwidth_up % 10,
 		   ntohl(gateway->bandwidth_down) / 10,
 		   ntohl(gateway->bandwidth_down) % 10,
 		   ntohl(gateway->bandwidth_up) / 10,
 		   ntohl(gateway->bandwidth_up) % 10);

 	gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
 	gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);

 	if (ntohl(gateway->bandwidth_down) == 0) {
 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 			   "Gateway %pM removed from gateway list\n",
 			   orig_node->orig);

 		/* Note: We don't need a NULL check here, since curr_gw never
 		 * gets dereferenced.
 		 */
 		spin_lock_bh(&bat_priv->gw.list_lock);
 		if (!hlist_unhashed(&gw_node->list)) {
 			hlist_del_init_rcu(&gw_node->list);
 			batadv_gw_node_put(gw_node);
 			bat_priv->gw.generation++;
 		}
 		spin_unlock_bh(&bat_priv->gw.list_lock);

 		curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 		if (gw_node == curr_gw)
 			batadv_gw_reselect(bat_priv);

 		batadv_gw_node_put(curr_gw);
 	}

 out:
 	batadv_gw_node_put(gw_node);
 }

 /**
  * batadv_gw_node_delete() - Remove orig_node from gateway list
  * @bat_priv: the bat priv with all the soft interface information
  * @orig_node: orig node which is currently in process of being removed
  */
 void batadv_gw_node_delete(struct batadv_priv *bat_priv,
 			   struct batadv_orig_node *orig_node)
 {
 	struct batadv_tvlv_gateway_data gateway;

 	gateway.bandwidth_down = 0;
 	gateway.bandwidth_up = 0;

 	batadv_gw_node_update(bat_priv, orig_node, &gateway);
 }

 /**
  * batadv_gw_node_free() - Free gateway information from soft interface
  * @bat_priv: the bat priv with all the soft interface information
  */
 void batadv_gw_node_free(struct batadv_priv *bat_priv)
 {
 	struct batadv_gw_node *gw_node;
 	struct hlist_node *node_tmp;

 	spin_lock_bh(&bat_priv->gw.list_lock);
 	hlist_for_each_entry_safe(gw_node, node_tmp,
 				  &bat_priv->gw.gateway_list, list) {
 		hlist_del_init_rcu(&gw_node->list);
 		batadv_gw_node_put(gw_node);
 		bat_priv->gw.generation++;
 	}
 	spin_unlock_bh(&bat_priv->gw.list_lock);
 }

 /**
  * batadv_gw_dump() - Dump gateways into a message
  * @msg: Netlink message to dump into
  * @cb: Control block containing additional options
  *
  * Return: Error code, or length of message
  */
 int batadv_gw_dump(struct sk_buff *msg, struct netlink_callback *cb)
 {
 	struct batadv_hard_iface *primary_if = NULL;
 	struct net *net = sock_net(cb->skb->sk);
 	struct net_device *soft_iface;
 	struct batadv_priv *bat_priv;
 	int ifindex;
 	int ret;

 	ifindex = batadv_netlink_get_ifindex(cb->nlh,
 					     BATADV_ATTR_MESH_IFINDEX);
 	if (!ifindex)
 		return -EINVAL;

 	soft_iface = dev_get_by_index(net, ifindex);
 	if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
 		ret = -ENODEV;
 		goto out;
 	}

 	bat_priv = netdev_priv(soft_iface);

 	primary_if = batadv_primary_if_get_selected(bat_priv);
 	if (!primary_if || primary_if->if_status != BATADV_IF_ACTIVE) {
 		ret = -ENOENT;
 		goto out;
 	}

 	if (!bat_priv->algo_ops->gw.dump) {
 		ret = -EOPNOTSUPP;
 		goto out;
 	}

 	bat_priv->algo_ops->gw.dump(msg, cb, bat_priv);

 	ret = msg->len;

 out:
 	batadv_hardif_put(primary_if);
 	dev_put(soft_iface);

 	return ret;
 }

 /**
  * batadv_gw_dhcp_recipient_get() - check if a packet is a DHCP message
  * @skb: the packet to check
  * @header_len: a pointer to the batman-adv header size
  * @chaddr: buffer where the client address will be stored. Valid
  *  only if the function returns BATADV_DHCP_TO_CLIENT
  *
  * This function may re-allocate the data buffer of the skb passed as argument.
  *
  * Return:
  * - BATADV_DHCP_NO if the packet is not a dhcp message or if there was an error
  *   while parsing it
  * - BATADV_DHCP_TO_SERVER if this is a message going to the DHCP server
  * - BATADV_DHCP_TO_CLIENT if this is a message going to a DHCP client
  */
 enum batadv_dhcp_recipient
 batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len,
 			     u8 *chaddr)
 {
 	enum batadv_dhcp_recipient ret = BATADV_DHCP_NO;
 	struct ethhdr *ethhdr;
 	struct iphdr *iphdr;
 	struct ipv6hdr *ipv6hdr;
 	struct udphdr *udphdr;
 	struct vlan_ethhdr *vhdr;
 	int chaddr_offset;
 	__be16 proto;
 	u8 *p;

 	/* check for ethernet header */
 	if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
 		return BATADV_DHCP_NO;

 	ethhdr = eth_hdr(skb);
 	proto = ethhdr->h_proto;
 	*header_len += ETH_HLEN;

 	/* check for initial vlan header */
 	if (proto == htons(ETH_P_8021Q)) {
 		if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
 			return BATADV_DHCP_NO;

 		vhdr = vlan_eth_hdr(skb);
 		proto = vhdr->h_vlan_encapsulated_proto;
 		*header_len += VLAN_HLEN;
 	}

 	/* check for ip header */
 	switch (proto) {
 	case htons(ETH_P_IP):
 		if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr)))
 			return BATADV_DHCP_NO;

 		iphdr = (struct iphdr *)(skb->data + *header_len);
 		*header_len += iphdr->ihl * 4;

 		/* check for udp header */
 		if (iphdr->protocol != IPPROTO_UDP)
 			return BATADV_DHCP_NO;

 		break;
 	case htons(ETH_P_IPV6):
 		if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr)))
 			return BATADV_DHCP_NO;

 		ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len);
 		*header_len += sizeof(*ipv6hdr);

 		/* check for udp header */
 		if (ipv6hdr->nexthdr != IPPROTO_UDP)
 			return BATADV_DHCP_NO;

 		break;
 	default:
 		return BATADV_DHCP_NO;
 	}

 	if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr)))
 		return BATADV_DHCP_NO;

 	udphdr = (struct udphdr *)(skb->data + *header_len);
 	*header_len += sizeof(*udphdr);

 	/* check for bootp port */
 	switch (proto) {
 	case htons(ETH_P_IP):
 		if (udphdr->dest == htons(67))
 			ret = BATADV_DHCP_TO_SERVER;
 		else if (udphdr->source == htons(67))
 			ret = BATADV_DHCP_TO_CLIENT;
 		break;
 	case htons(ETH_P_IPV6):
 		if (udphdr->dest == htons(547))
 			ret = BATADV_DHCP_TO_SERVER;
 		else if (udphdr->source == htons(547))
 			ret = BATADV_DHCP_TO_CLIENT;
 		break;
 	}

 	chaddr_offset = *header_len + BATADV_DHCP_CHADDR_OFFSET;
 	/* store the client address if the message is going to a client */
 	if (ret == BATADV_DHCP_TO_CLIENT) {
 		if (!pskb_may_pull(skb, chaddr_offset + ETH_ALEN))
 			return BATADV_DHCP_NO;

 		/* check if the DHCP packet carries an Ethernet DHCP */
 		p = skb->data + *header_len + BATADV_DHCP_HTYPE_OFFSET;
 		if (*p != BATADV_DHCP_HTYPE_ETHERNET)
 			return BATADV_DHCP_NO;

 		/* check if the DHCP packet carries a valid Ethernet address */
 		p = skb->data + *header_len + BATADV_DHCP_HLEN_OFFSET;
 		if (*p != ETH_ALEN)
 			return BATADV_DHCP_NO;

 		ether_addr_copy(chaddr, skb->data + chaddr_offset);
 	}

 	return ret;
 }

 /**
  * batadv_gw_out_of_range() - check if the dhcp request destination is the best
  *  gateway
  * @bat_priv: the bat priv with all the soft interface information
  * @skb: the outgoing packet
  *
  * Check if the skb is a DHCP request and if it is sent to the current best GW
  * server. Due to topology changes it may be the case that the GW server
  * previously selected is not the best one anymore.
  *
  * This call might reallocate skb data.
  * Must be invoked only when the DHCP packet is going TO a DHCP SERVER.
  *
  * Return: true if the packet destination is unicast and it is not the best gw,
  * false otherwise.
  */
 bool batadv_gw_out_of_range(struct batadv_priv *bat_priv,
 			    struct sk_buff *skb)
 {
 	struct batadv_neigh_node *neigh_curr = NULL;
 	struct batadv_neigh_node *neigh_old = NULL;
 	struct batadv_orig_node *orig_dst_node = NULL;
 	struct batadv_gw_node *gw_node = NULL;
 	struct batadv_gw_node *curr_gw = NULL;
 	struct batadv_neigh_ifinfo *curr_ifinfo, *old_ifinfo;
 	struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
 	bool out_of_range = false;
 	u8 curr_tq_avg;
 	unsigned short vid;

 	vid = batadv_get_vid(skb, 0);

 	if (is_multicast_ether_addr(ethhdr->h_dest))
 		goto out;

 	orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
 						 ethhdr->h_dest, vid);
 	if (!orig_dst_node)
 		goto out;

 	gw_node = batadv_gw_node_get(bat_priv, orig_dst_node);
 	if (!gw_node)
 		goto out;

 	switch (atomic_read(&bat_priv->gw.mode)) {
 	case BATADV_GW_MODE_SERVER:
 		/* If we are a GW then we are our best GW. We can artificially
 		 * set the tq towards ourself as the maximum value
 		 */
 		curr_tq_avg = BATADV_TQ_MAX_VALUE;
 		break;
 	case BATADV_GW_MODE_CLIENT:
 		curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 		if (!curr_gw)
 			goto out;

 		/* packet is going to our gateway */
 		if (curr_gw->orig_node == orig_dst_node)
 			goto out;

 		/* If the dhcp packet has been sent to a different gw,
 		 * we have to evaluate whether the old gw is still
 		 * reliable enough
 		 */
 		neigh_curr = batadv_find_router(bat_priv, curr_gw->orig_node,
 						NULL);
 		if (!neigh_curr)
 			goto out;

 		curr_ifinfo = batadv_neigh_ifinfo_get(neigh_curr,
 						      BATADV_IF_DEFAULT);
 		if (!curr_ifinfo)
 			goto out;

 		curr_tq_avg = curr_ifinfo->bat_iv.tq_avg;
 		batadv_neigh_ifinfo_put(curr_ifinfo);

 		break;
 	case BATADV_GW_MODE_OFF:
 	default:
 		goto out;
 	}

 	neigh_old = batadv_find_router(bat_priv, orig_dst_node, NULL);
 	if (!neigh_old)
 		goto out;

 	old_ifinfo = batadv_neigh_ifinfo_get(neigh_old, BATADV_IF_DEFAULT);
 	if (!old_ifinfo)
 		goto out;

 	if ((curr_tq_avg - old_ifinfo->bat_iv.tq_avg) > BATADV_GW_THRESHOLD)
 		out_of_range = true;
 	batadv_neigh_ifinfo_put(old_ifinfo);

 out:
 	batadv_orig_node_put(orig_dst_node);
 	batadv_gw_node_put(curr_gw);
 	batadv_gw_node_put(gw_node);
 	batadv_neigh_node_put(neigh_old);
 	batadv_neigh_node_put(neigh_curr);
 	return out_of_range;
 }
	// SPDX-License-Identifier: GPL-2.0
	/* Copyright (C) B.A.T.M.A.N. contributors:
	*
	* Marek Lindner
	*/

	#include "gateway_client.h"
	#include "main.h"

	#include <linux/atomic.h>
	#include <linux/byteorder/generic.h>
	#include <linux/errno.h>
	#include <linux/etherdevice.h>
	#include <linux/gfp.h>
	#include <linux/if_ether.h>
	#include <linux/if_vlan.h>
	#include <linux/in.h>
	#include <linux/ip.h>
	#include <linux/ipv6.h>
	#include <linux/kernel.h>
	#include <linux/kref.h>
	#include <linux/list.h>
	#include <linux/lockdep.h>
	#include <linux/netdevice.h>
	#include <linux/netlink.h>
	#include <linux/rculist.h>
	#include <linux/rcupdate.h>
	#include <linux/skbuff.h>
	#include <linux/slab.h>
	#include <linux/spinlock.h>
	#include <linux/stddef.h>
	#include <linux/udp.h>
	#include <net/sock.h>
	#include <uapi/linux/batadv_packet.h>
	#include <uapi/linux/batman_adv.h>

	#include "hard-interface.h"
	#include "log.h"
	#include "netlink.h"
	#include "originator.h"
	#include "routing.h"
	#include "soft-interface.h"
	#include "translation-table.h"

	/* These are the offsets of the "hw type" and "hw address length" in the dhcp
	* packet starting at the beginning of the dhcp header
	*/
	#define BATADV_DHCP_HTYPE_OFFSET 1
	#define BATADV_DHCP_HLEN_OFFSET 2
	/* Value of htype representing Ethernet */
	#define BATADV_DHCP_HTYPE_ETHERNET 0x01
	/* This is the offset of the "chaddr" field in the dhcp packet starting at the
	* beginning of the dhcp header
	*/
	#define BATADV_DHCP_CHADDR_OFFSET 28

	/**
	* batadv_gw_node_release() - release gw_node from lists and queue for free
	* after rcu grace period
	* @ref: kref pointer of the gw_node
	*/
	void batadv_gw_node_release(struct kref *ref)
	{
	struct batadv_gw_node *gw_node;

	gw_node = container_of(ref, struct batadv_gw_node, refcount);

	batadv_orig_node_put(gw_node->orig_node);
	kfree_rcu(gw_node, rcu);
	}

	/**
	* batadv_gw_get_selected_gw_node() - Get currently selected gateway
	* @bat_priv: the bat priv with all the soft interface information
	*
	* Return: selected gateway (with increased refcnt), NULL on errors
	*/
	struct batadv_gw_node *
	batadv_gw_get_selected_gw_node(struct batadv_priv *bat_priv)
	{
	struct batadv_gw_node *gw_node;

	rcu_read_lock();
	gw_node = rcu_dereference(bat_priv->gw.curr_gw);
	if (!gw_node)
	goto out;

	if (!kref_get_unless_zero(&gw_node->refcount))
	gw_node = NULL;

	out:
	rcu_read_unlock();
	return gw_node;
	}

	/**
	* batadv_gw_get_selected_orig() - Get originator of currently selected gateway
	* @bat_priv: the bat priv with all the soft interface information
	*
	* Return: orig_node of selected gateway (with increased refcnt), NULL on errors
	*/
	struct batadv_orig_node *
	batadv_gw_get_selected_orig(struct batadv_priv *bat_priv)
	{
	struct batadv_gw_node *gw_node;
	struct batadv_orig_node *orig_node = NULL;

	gw_node = batadv_gw_get_selected_gw_node(bat_priv);
	if (!gw_node)
	goto out;

	rcu_read_lock();
	orig_node = gw_node->orig_node;
	if (!orig_node)
	goto unlock;

	if (!kref_get_unless_zero(&orig_node->refcount))
	orig_node = NULL;

	unlock:
	rcu_read_unlock();
	out:
	batadv_gw_node_put(gw_node);
	return orig_node;
	}

	static void batadv_gw_select(struct batadv_priv *bat_priv,
	struct batadv_gw_node *new_gw_node)
	{
	struct batadv_gw_node *curr_gw_node;

	spin_lock_bh(&bat_priv->gw.list_lock);

	if (new_gw_node)
	kref_get(&new_gw_node->refcount);

	curr_gw_node = rcu_replace_pointer(bat_priv->gw.curr_gw, new_gw_node,
	true);

	batadv_gw_node_put(curr_gw_node);

	spin_unlock_bh(&bat_priv->gw.list_lock);
	}

	/**
	* batadv_gw_reselect() - force a gateway reselection
	* @bat_priv: the bat priv with all the soft interface information
	*
	* Set a flag to remind the GW component to perform a new gateway reselection.
	* However this function does not ensure that the current gateway is going to be
	* deselected. The reselection mechanism may elect the same gateway once again.
	*
	* This means that invoking batadv_gw_reselect() does not guarantee a gateway
	* change and therefore a uevent is not necessarily expected.
	*/
	void batadv_gw_reselect(struct batadv_priv *bat_priv)
	{
	atomic_set(&bat_priv->gw.reselect, 1);
	}

	/**
	* batadv_gw_check_client_stop() - check if client mode has been switched off
	* @bat_priv: the bat priv with all the soft interface information
	*
	* This function assumes the caller has checked that the gw state *is actually
	* changing*. This function is not supposed to be called when there is no state
	* change.
	*/
	void batadv_gw_check_client_stop(struct batadv_priv *bat_priv)
	{
	struct batadv_gw_node *curr_gw;

	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
	return;

	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
	if (!curr_gw)
	return;

	/* deselect the current gateway so that next time that client mode is
	* enabled a proper GW_ADD event can be sent
	*/
	batadv_gw_select(bat_priv, NULL);

	/* if batman-adv is switching the gw client mode off and a gateway was
	* already selected, send a DEL uevent
	*/
	batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL, NULL);

	batadv_gw_node_put(curr_gw);
	}

	/**
	* batadv_gw_election() - Elect the best gateway
	* @bat_priv: the bat priv with all the soft interface information
	*/
	void batadv_gw_election(struct batadv_priv *bat_priv)
	{
	struct batadv_gw_node *curr_gw = NULL;
	struct batadv_gw_node *next_gw = NULL;
	struct batadv_neigh_node *router = NULL;
	struct batadv_neigh_ifinfo *router_ifinfo = NULL;
	char gw_addr[18] = { '\0' };

	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
	goto out;

	if (!bat_priv->algo_ops->gw.get_best_gw_node)
	goto out;

	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);

	if (!batadv_atomic_dec_not_zero(&bat_priv->gw.reselect) && curr_gw)
	goto out;

	/* if gw.reselect is set to 1 it means that a previous call to
	* gw.is_eligible() said that we have a new best GW, therefore it can
	* now be picked from the list and selected
	*/
	next_gw = bat_priv->algo_ops->gw.get_best_gw_node(bat_priv);

	if (curr_gw == next_gw)
	goto out;

	if (next_gw) {
	sprintf(gw_addr, "%pM", next_gw->orig_node->orig);

	router = batadv_orig_router_get(next_gw->orig_node,
	BATADV_IF_DEFAULT);
	if (!router) {
	batadv_gw_reselect(bat_priv);
	goto out;
	}

	router_ifinfo = batadv_neigh_ifinfo_get(router,
	BATADV_IF_DEFAULT);
	if (!router_ifinfo) {
	batadv_gw_reselect(bat_priv);
	goto out;
	}
	}

	if (curr_gw && !next_gw) {
	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
	"Removing selected gateway - no gateway in range\n");
	batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL,
	NULL);
	} else if (!curr_gw && next_gw) {
	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
	"Adding route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
	next_gw->orig_node->orig,
	next_gw->bandwidth_down / 10,
	next_gw->bandwidth_down % 10,
	next_gw->bandwidth_up / 10,
	next_gw->bandwidth_up % 10,
	router_ifinfo->bat_iv.tq_avg);
	batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_ADD,
	gw_addr);
	} else {
	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
	"Changing route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
	next_gw->orig_node->orig,
	next_gw->bandwidth_down / 10,
	next_gw->bandwidth_down % 10,
	next_gw->bandwidth_up / 10,
	next_gw->bandwidth_up % 10,
	router_ifinfo->bat_iv.tq_avg);
	batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_CHANGE,
	gw_addr);
	}

	batadv_gw_select(bat_priv, next_gw);

	out:
	batadv_gw_node_put(curr_gw);
	batadv_gw_node_put(next_gw);
	batadv_neigh_node_put(router);
	batadv_neigh_ifinfo_put(router_ifinfo);
	}

	/**
	* batadv_gw_check_election() - Elect orig node as best gateway when eligible
	* @bat_priv: the bat priv with all the soft interface information
	* @orig_node: orig node which is to be checked
	*/
	void batadv_gw_check_election(struct batadv_priv *bat_priv,
	struct batadv_orig_node *orig_node)
	{
	struct batadv_orig_node *curr_gw_orig;

	/* abort immediately if the routing algorithm does not support gateway
	* election
	*/
	if (!bat_priv->algo_ops->gw.is_eligible)
	return;

	curr_gw_orig = batadv_gw_get_selected_orig(bat_priv);
	if (!curr_gw_orig)
	goto reselect;

	/* this node already is the gateway */
	if (curr_gw_orig == orig_node)
	goto out;

	if (!bat_priv->algo_ops->gw.is_eligible(bat_priv, curr_gw_orig,
	orig_node))
	goto out;

	reselect:
	batadv_gw_reselect(bat_priv);
	out:
	batadv_orig_node_put(curr_gw_orig);
	}

	/**
	* batadv_gw_node_add() - add gateway node to list of available gateways
	* @bat_priv: the bat priv with all the soft interface information
	* @orig_node: originator announcing gateway capabilities
	* @gateway: announced bandwidth information
	*
	* Has to be called with the appropriate locks being acquired
	* (gw.list_lock).
	*/
	static void batadv_gw_node_add(struct batadv_priv *bat_priv,
	struct batadv_orig_node *orig_node,
	struct batadv_tvlv_gateway_data *gateway)
	{
	struct batadv_gw_node *gw_node;

	lockdep_assert_held(&bat_priv->gw.list_lock);

	if (gateway->bandwidth_down == 0)
	return;

	gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
	if (!gw_node)
	return;

	kref_init(&gw_node->refcount);
	INIT_HLIST_NODE(&gw_node->list);
	kref_get(&orig_node->refcount);
	gw_node->orig_node = orig_node;
	gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
	gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);

	kref_get(&gw_node->refcount);
	hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.gateway_list);
	bat_priv->gw.generation++;

	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
	"Found new gateway %pM -> gw bandwidth: %u.%u/%u.%u MBit\n",
	orig_node->orig,
	ntohl(gateway->bandwidth_down) / 10,
	ntohl(gateway->bandwidth_down) % 10,
	ntohl(gateway->bandwidth_up) / 10,
	ntohl(gateway->bandwidth_up) % 10);

	/* don't return reference to new gw_node */
	batadv_gw_node_put(gw_node);
	}

	/**
	* batadv_gw_node_get() - retrieve gateway node from list of available gateways
	* @bat_priv: the bat priv with all the soft interface information
	* @orig_node: originator announcing gateway capabilities
	*
	* Return: gateway node if found or NULL otherwise.
	*/
	struct batadv_gw_node batadv_gw_node_get(struct batadv_priv bat_priv,
	struct batadv_orig_node *orig_node)
	{
	struct batadv_gw_node gw_node_tmp, gw_node = NULL;

	rcu_read_lock();
	hlist_for_each_entry_rcu(gw_node_tmp, &bat_priv->gw.gateway_list,
	list) {
	if (gw_node_tmp->orig_node != orig_node)
	continue;

	if (!kref_get_unless_zero(&gw_node_tmp->refcount))
	continue;

	gw_node = gw_node_tmp;
	break;
	}
	rcu_read_unlock();

	return gw_node;
	}

	/**
	* batadv_gw_node_update() - update list of available gateways with changed
	* bandwidth information
	* @bat_priv: the bat priv with all the soft interface information
	* @orig_node: originator announcing gateway capabilities
	* @gateway: announced bandwidth information
	*/
	void batadv_gw_node_update(struct batadv_priv *bat_priv,
	struct batadv_orig_node *orig_node,
	struct batadv_tvlv_gateway_data *gateway)
	{
	struct batadv_gw_node gw_node, curr_gw = NULL;

	spin_lock_bh(&bat_priv->gw.list_lock);
	gw_node = batadv_gw_node_get(bat_priv, orig_node);
	if (!gw_node) {
	batadv_gw_node_add(bat_priv, orig_node, gateway);
	spin_unlock_bh(&bat_priv->gw.list_lock);
	goto out;
	}
	spin_unlock_bh(&bat_priv->gw.list_lock);

	if (gw_node->bandwidth_down == ntohl(gateway->bandwidth_down) &&
	gw_node->bandwidth_up == ntohl(gateway->bandwidth_up))
	goto out;

	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
	"Gateway bandwidth of originator %pM changed from %u.%u/%u.%u MBit to %u.%u/%u.%u MBit\n",
	orig_node->orig,
	gw_node->bandwidth_down / 10,
	gw_node->bandwidth_down % 10,
	gw_node->bandwidth_up / 10,
	gw_node->bandwidth_up % 10,
	ntohl(gateway->bandwidth_down) / 10,
	ntohl(gateway->bandwidth_down) % 10,
	ntohl(gateway->bandwidth_up) / 10,
	ntohl(gateway->bandwidth_up) % 10);

	gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
	gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);

	if (ntohl(gateway->bandwidth_down) == 0) {
	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
	"Gateway %pM removed from gateway list\n",
	orig_node->orig);

	/* Note: We don't need a NULL check here, since curr_gw never
	* gets dereferenced.
	*/
	spin_lock_bh(&bat_priv->gw.list_lock);
	if (!hlist_unhashed(&gw_node->list)) {
	hlist_del_init_rcu(&gw_node->list);
	batadv_gw_node_put(gw_node);
	bat_priv->gw.generation++;
	}
	spin_unlock_bh(&bat_priv->gw.list_lock);

	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
	if (gw_node == curr_gw)
	batadv_gw_reselect(bat_priv);

	batadv_gw_node_put(curr_gw);
	}

	out:
	batadv_gw_node_put(gw_node);
	}

	/**
	* batadv_gw_node_delete() - Remove orig_node from gateway list
	* @bat_priv: the bat priv with all the soft interface information
	* @orig_node: orig node which is currently in process of being removed
	*/
	void batadv_gw_node_delete(struct batadv_priv *bat_priv,
	struct batadv_orig_node *orig_node)
	{
	struct batadv_tvlv_gateway_data gateway;

	gateway.bandwidth_down = 0;
	gateway.bandwidth_up = 0;

	batadv_gw_node_update(bat_priv, orig_node, &gateway);
	}

	/**
	* batadv_gw_node_free() - Free gateway information from soft interface
	* @bat_priv: the bat priv with all the soft interface information
	*/
	void batadv_gw_node_free(struct batadv_priv *bat_priv)
	{
	struct batadv_gw_node *gw_node;
	struct hlist_node *node_tmp;

	spin_lock_bh(&bat_priv->gw.list_lock);
	hlist_for_each_entry_safe(gw_node, node_tmp,
	&bat_priv->gw.gateway_list, list) {
	hlist_del_init_rcu(&gw_node->list);
	batadv_gw_node_put(gw_node);
	bat_priv->gw.generation++;
	}
	spin_unlock_bh(&bat_priv->gw.list_lock);
	}

	/**
	* batadv_gw_dump() - Dump gateways into a message
	* @msg: Netlink message to dump into
	* @cb: Control block containing additional options
	*
	* Return: Error code, or length of message
	*/
	int batadv_gw_dump(struct sk_buff msg, struct netlink_callback cb)
	{
	struct batadv_hard_iface *primary_if = NULL;
	struct net *net = sock_net(cb->skb->sk);
	struct net_device *soft_iface;
	struct batadv_priv *bat_priv;
	int ifindex;
	int ret;

	ifindex = batadv_netlink_get_ifindex(cb->nlh,
	BATADV_ATTR_MESH_IFINDEX);
	if (!ifindex)
	return -EINVAL;

	soft_iface = dev_get_by_index(net, ifindex);
	if (!soft_iface \|\| !batadv_softif_is_valid(soft_iface)) {
	ret = -ENODEV;
	goto out;
	}

	bat_priv = netdev_priv(soft_iface);

	primary_if = batadv_primary_if_get_selected(bat_priv);
	if (!primary_if \|\| primary_if->if_status != BATADV_IF_ACTIVE) {
	ret = -ENOENT;
	goto out;
	}

	if (!bat_priv->algo_ops->gw.dump) {
	ret = -EOPNOTSUPP;
	goto out;
	}

	bat_priv->algo_ops->gw.dump(msg, cb, bat_priv);

	ret = msg->len;

	out:
	batadv_hardif_put(primary_if);
	dev_put(soft_iface);

	return ret;
	}

	/**
	* batadv_gw_dhcp_recipient_get() - check if a packet is a DHCP message
	* @skb: the packet to check
	* @header_len: a pointer to the batman-adv header size
	* @chaddr: buffer where the client address will be stored. Valid
	* only if the function returns BATADV_DHCP_TO_CLIENT
	*
	* This function may re-allocate the data buffer of the skb passed as argument.
	*
	* Return:
	* - BATADV_DHCP_NO if the packet is not a dhcp message or if there was an error
	* while parsing it
	* - BATADV_DHCP_TO_SERVER if this is a message going to the DHCP server
	* - BATADV_DHCP_TO_CLIENT if this is a message going to a DHCP client
	*/
	enum batadv_dhcp_recipient
	batadv_gw_dhcp_recipient_get(struct sk_buff skb, unsigned int header_len,
	u8 *chaddr)
	{
	enum batadv_dhcp_recipient ret = BATADV_DHCP_NO;
	struct ethhdr *ethhdr;
	struct iphdr *iphdr;
	struct ipv6hdr *ipv6hdr;
	struct udphdr *udphdr;
	struct vlan_ethhdr *vhdr;
	int chaddr_offset;
	__be16 proto;
	u8 *p;

	/* check for ethernet header */
	if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
	return BATADV_DHCP_NO;

	ethhdr = eth_hdr(skb);
	proto = ethhdr->h_proto;
	*header_len += ETH_HLEN;

	/* check for initial vlan header */
	if (proto == htons(ETH_P_8021Q)) {
	if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
	return BATADV_DHCP_NO;

	vhdr = vlan_eth_hdr(skb);
	proto = vhdr->h_vlan_encapsulated_proto;
	*header_len += VLAN_HLEN;
	}

	/* check for ip header */
	switch (proto) {
	case htons(ETH_P_IP):
	if (!pskb_may_pull(skb, header_len + sizeof(iphdr)))
	return BATADV_DHCP_NO;

	iphdr = (struct iphdr )(skb->data + header_len);
	header_len += iphdr->ihl 4;

	/* check for udp header */
	if (iphdr->protocol != IPPROTO_UDP)
	return BATADV_DHCP_NO;

	break;
	case htons(ETH_P_IPV6):
	if (!pskb_may_pull(skb, header_len + sizeof(ipv6hdr)))
	return BATADV_DHCP_NO;

	ipv6hdr = (struct ipv6hdr )(skb->data + header_len);
	header_len += sizeof(ipv6hdr);

	/* check for udp header */
	if (ipv6hdr->nexthdr != IPPROTO_UDP)
	return BATADV_DHCP_NO;

	break;
	default:
	return BATADV_DHCP_NO;
	}

	if (!pskb_may_pull(skb, header_len + sizeof(udphdr)))
	return BATADV_DHCP_NO;

	udphdr = (struct udphdr )(skb->data + header_len);
	header_len += sizeof(udphdr);

	/* check for bootp port */
	switch (proto) {
	case htons(ETH_P_IP):
	if (udphdr->dest == htons(67))
	ret = BATADV_DHCP_TO_SERVER;
	else if (udphdr->source == htons(67))
	ret = BATADV_DHCP_TO_CLIENT;
	break;
	case htons(ETH_P_IPV6):
	if (udphdr->dest == htons(547))
	ret = BATADV_DHCP_TO_SERVER;
	else if (udphdr->source == htons(547))
	ret = BATADV_DHCP_TO_CLIENT;
	break;
	}

	chaddr_offset = *header_len + BATADV_DHCP_CHADDR_OFFSET;
	/* store the client address if the message is going to a client */
	if (ret == BATADV_DHCP_TO_CLIENT) {
	if (!pskb_may_pull(skb, chaddr_offset + ETH_ALEN))
	return BATADV_DHCP_NO;

	/* check if the DHCP packet carries an Ethernet DHCP */
	p = skb->data + *header_len + BATADV_DHCP_HTYPE_OFFSET;
	if (*p != BATADV_DHCP_HTYPE_ETHERNET)
	return BATADV_DHCP_NO;

	/* check if the DHCP packet carries a valid Ethernet address */
	p = skb->data + *header_len + BATADV_DHCP_HLEN_OFFSET;
	if (*p != ETH_ALEN)
	return BATADV_DHCP_NO;

	ether_addr_copy(chaddr, skb->data + chaddr_offset);
	}

	return ret;
	}

	/**
	* batadv_gw_out_of_range() - check if the dhcp request destination is the best
	* gateway
	* @bat_priv: the bat priv with all the soft interface information
	* @skb: the outgoing packet
	*
	* Check if the skb is a DHCP request and if it is sent to the current best GW
	* server. Due to topology changes it may be the case that the GW server
	* previously selected is not the best one anymore.
	*
	* This call might reallocate skb data.
	* Must be invoked only when the DHCP packet is going TO a DHCP SERVER.
	*
	* Return: true if the packet destination is unicast and it is not the best gw,
	* false otherwise.
	*/
	bool batadv_gw_out_of_range(struct batadv_priv *bat_priv,
	struct sk_buff *skb)
	{
	struct batadv_neigh_node *neigh_curr = NULL;
	struct batadv_neigh_node *neigh_old = NULL;
	struct batadv_orig_node *orig_dst_node = NULL;
	struct batadv_gw_node *gw_node = NULL;
	struct batadv_gw_node *curr_gw = NULL;
	struct batadv_neigh_ifinfo curr_ifinfo, old_ifinfo;
	struct ethhdr ethhdr = (struct ethhdr )skb->data;
	bool out_of_range = false;
	u8 curr_tq_avg;
	unsigned short vid;

	vid = batadv_get_vid(skb, 0);

	if (is_multicast_ether_addr(ethhdr->h_dest))
	goto out;

	orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
	ethhdr->h_dest, vid);
	if (!orig_dst_node)
	goto out;

	gw_node = batadv_gw_node_get(bat_priv, orig_dst_node);
	if (!gw_node)
	goto out;

	switch (atomic_read(&bat_priv->gw.mode)) {
	case BATADV_GW_MODE_SERVER:
	/* If we are a GW then we are our best GW. We can artificially
	* set the tq towards ourself as the maximum value
	*/
	curr_tq_avg = BATADV_TQ_MAX_VALUE;
	break;
	case BATADV_GW_MODE_CLIENT:
	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
	if (!curr_gw)
	goto out;

	/* packet is going to our gateway */
	if (curr_gw->orig_node == orig_dst_node)
	goto out;

	/* If the dhcp packet has been sent to a different gw,
	* we have to evaluate whether the old gw is still
	* reliable enough
	*/
	neigh_curr = batadv_find_router(bat_priv, curr_gw->orig_node,
	NULL);
	if (!neigh_curr)
	goto out;

	curr_ifinfo = batadv_neigh_ifinfo_get(neigh_curr,
	BATADV_IF_DEFAULT);
	if (!curr_ifinfo)
	goto out;

	curr_tq_avg = curr_ifinfo->bat_iv.tq_avg;
	batadv_neigh_ifinfo_put(curr_ifinfo);

	break;
	case BATADV_GW_MODE_OFF:
	default:
	goto out;
	}

	neigh_old = batadv_find_router(bat_priv, orig_dst_node, NULL);
	if (!neigh_old)
	goto out;

	old_ifinfo = batadv_neigh_ifinfo_get(neigh_old, BATADV_IF_DEFAULT);
	if (!old_ifinfo)
	goto out;

	if ((curr_tq_avg - old_ifinfo->bat_iv.tq_avg) > BATADV_GW_THRESHOLD)
	out_of_range = true;
	batadv_neigh_ifinfo_put(old_ifinfo);

	out:
	batadv_orig_node_put(orig_dst_node);
	batadv_gw_node_put(curr_gw);
	batadv_gw_node_put(gw_node);
	batadv_neigh_node_put(neigh_old);
	batadv_neigh_node_put(neigh_curr);
	return out_of_range;
	}