Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 823 insertions, 0 deletions

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
new file mode 100644
index 000000000..62f6f13f8
--- /dev/null
+++ b/net/batman-adv/gateway_client.c
@@ -0,0 +1,823 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2009-2020  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/seq_file.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:
+	if (gw_node)
+		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);
+
+	if (curr_gw_node)
+		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:
+	if (curr_gw)
+		batadv_gw_node_put(curr_gw);
+	if (next_gw)
+		batadv_gw_node_put(next_gw);
+	if (router)
+		batadv_neigh_node_put(router);
+	if (router_ifinfo)
+		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:
+	if (curr_gw_orig)
+		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);
+
+		if (curr_gw)
+			batadv_gw_node_put(curr_gw);
+	}
+
+out:
+	if (gw_node)
+		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);
+}
+
+#ifdef CONFIG_BATMAN_ADV_DEBUGFS
+
+/**
+ * batadv_gw_client_seq_print_text() - Print the gateway table in a seq file
+ * @seq: seq file to print on
+ * @offset: not used
+ *
+ * Return: always 0
+ */
+int batadv_gw_client_seq_print_text(struct seq_file *seq, void *offset)
+{
+	struct net_device *net_dev = (struct net_device *)seq->private;
+	struct batadv_priv *bat_priv = netdev_priv(net_dev);
+	struct batadv_hard_iface *primary_if;
+
+	primary_if = batadv_seq_print_text_primary_if_get(seq);
+	if (!primary_if)
+		return 0;
+
+	seq_printf(seq, "[B.A.T.M.A.N. adv %s, MainIF/MAC: %s/%pM (%s %s)]\n",
+		   BATADV_SOURCE_VERSION, primary_if->net_dev->name,
+		   primary_if->net_dev->dev_addr, net_dev->name,
+		   bat_priv->algo_ops->name);
+
+	batadv_hardif_put(primary_if);
+
+	if (!bat_priv->algo_ops->gw.print) {
+		seq_puts(seq,
+			 "No printing function for this routing protocol\n");
+		return 0;
+	}
+
+	bat_priv->algo_ops->gw.print(bat_priv, seq);
+
+	return 0;
+}
+#endif
+
+/**
+ * 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:
+	if (primary_if)
+		batadv_hardif_put(primary_if);
+	if (soft_iface)
+		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:
+	if (orig_dst_node)
+		batadv_orig_node_put(orig_dst_node);
+	if (curr_gw)
+		batadv_gw_node_put(curr_gw);
+	if (gw_node)
+		batadv_gw_node_put(gw_node);
+	if (neigh_old)
+		batadv_neigh_node_put(neigh_old);
+	if (neigh_curr)
+		batadv_neigh_node_put(neigh_curr);
+	return out_of_range;
+}