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

#include "main.h"

#include <linux/byteorder/generic.h>
#include <linux/container_of.h>
#include <linux/etherdevice.h>
#include <linux/gfp.h>
#include <linux/if_ether.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/lockdep.h>
#include <linux/netdevice.h>
#include <linux/pkt_sched.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/string.h>
#include <linux/types.h>
#include <uapi/linux/batadv_packet.h>

#include "originator.h"
#include "send.h"
#include "tvlv.h"

/**
 * batadv_tvlv_handler_release() - release tvlv handler from lists and queue for
 *  free after rcu grace period
 * @ref: kref pointer of the tvlv
 */
static void batadv_tvlv_handler_release(struct kref *ref)
{
        struct batadv_tvlv_handler *tvlv_handler;

        tvlv_handler = container_of(ref, struct batadv_tvlv_handler, refcount);
        kfree_rcu(tvlv_handler, rcu);
}

/**
 * batadv_tvlv_handler_put() - decrement the tvlv container refcounter and
 *  possibly release it
 * @tvlv_handler: the tvlv handler to free
 */
static void batadv_tvlv_handler_put(struct batadv_tvlv_handler *tvlv_handler)
{
        if (!tvlv_handler)
                return;

        kref_put(&tvlv_handler->refcount, batadv_tvlv_handler_release);
}

/**
 * batadv_tvlv_handler_get() - retrieve tvlv handler from the tvlv handler list
 *  based on the provided type and version (both need to match)
 * @bat_priv: the bat priv with all the mesh interface information
 * @type: tvlv handler type to look for
 * @version: tvlv handler version to look for
 *
 * Return: tvlv handler if found or NULL otherwise.
 */
static struct batadv_tvlv_handler *
batadv_tvlv_handler_get(struct batadv_priv *bat_priv, u8 type, u8 version)
{
        struct batadv_tvlv_handler *tvlv_handler_tmp, *tvlv_handler = NULL;

        rcu_read_lock();
        hlist_for_each_entry_rcu(tvlv_handler_tmp,
                                 &bat_priv->tvlv.handler_list, list) {
                if (tvlv_handler_tmp->type != type)
                        continue;

                if (tvlv_handler_tmp->version != version)
                        continue;

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

                tvlv_handler = tvlv_handler_tmp;
                break;
        }
        rcu_read_unlock();

        return tvlv_handler;
}

/**
 * batadv_tvlv_container_release() - release tvlv from lists and free
 * @ref: kref pointer of the tvlv
 */
static void batadv_tvlv_container_release(struct kref *ref)
{
        struct batadv_tvlv_container *tvlv;

        tvlv = container_of(ref, struct batadv_tvlv_container, refcount);
        kfree(tvlv);
}

/**
 * batadv_tvlv_container_put() - decrement the tvlv container refcounter and
 *  possibly release it
 * @tvlv: the tvlv container to free
 */
static void batadv_tvlv_container_put(struct batadv_tvlv_container *tvlv)
{
        if (!tvlv)
                return;

        kref_put(&tvlv->refcount, batadv_tvlv_container_release);
}

/**
 * batadv_tvlv_container_get() - retrieve tvlv container from the tvlv container
 *  list based on the provided type and version (both need to match)
 * @bat_priv: the bat priv with all the mesh interface information
 * @type: tvlv container type to look for
 * @version: tvlv container version to look for
 *
 * Has to be called with the appropriate locks being acquired
 * (tvlv.container_list_lock).
 *
 * Return: tvlv container if found or NULL otherwise.
 */
static struct batadv_tvlv_container *
batadv_tvlv_container_get(struct batadv_priv *bat_priv, u8 type, u8 version)
{
        struct batadv_tvlv_container *tvlv_tmp, *tvlv = NULL;

        lockdep_assert_held(&bat_priv->tvlv.container_list_lock);

        hlist_for_each_entry(tvlv_tmp, &bat_priv->tvlv.container_list, list) {
                if (tvlv_tmp->tvlv_hdr.type != type)
                        continue;

                if (tvlv_tmp->tvlv_hdr.version != version)
                        continue;

                kref_get(&tvlv_tmp->refcount);
                tvlv = tvlv_tmp;
                break;
        }

        return tvlv;
}

/**
 * batadv_tvlv_container_list_size() - calculate the size of the tvlv container
 *  list entries
 * @bat_priv: the bat priv with all the mesh interface information
 *
 * Has to be called with the appropriate locks being acquired
 * (tvlv.container_list_lock).
 *
 * Return: size of all currently registered tvlv containers in bytes.
 */
static u16 batadv_tvlv_container_list_size(struct batadv_priv *bat_priv)
{
        struct batadv_tvlv_container *tvlv;
        u16 tvlv_len = 0;

        lockdep_assert_held(&bat_priv->tvlv.container_list_lock);

        hlist_for_each_entry(tvlv, &bat_priv->tvlv.container_list, list) {
                tvlv_len += sizeof(struct batadv_tvlv_hdr);
                tvlv_len += ntohs(tvlv->tvlv_hdr.len);
        }

        return tvlv_len;
}

/**
 * batadv_tvlv_container_remove() - remove tvlv container from the tvlv
 *  container list
 * @bat_priv: the bat priv with all the mesh interface information
 * @tvlv: the to be removed tvlv container
 *
 * Has to be called with the appropriate locks being acquired
 * (tvlv.container_list_lock).
 */
static void batadv_tvlv_container_remove(struct batadv_priv *bat_priv,
                                         struct batadv_tvlv_container *tvlv)
{
        lockdep_assert_held(&bat_priv->tvlv.container_list_lock);

        if (!tvlv)
                return;

        hlist_del(&tvlv->list);

        /* first call to decrement the counter, second call to free */
        batadv_tvlv_container_put(tvlv);
        batadv_tvlv_container_put(tvlv);
}

/**
 * batadv_tvlv_container_unregister() - unregister tvlv container based on the
 *  provided type and version (both need to match)
 * @bat_priv: the bat priv with all the mesh interface information
 * @type: tvlv container type to unregister
 * @version: tvlv container type to unregister
 */
void batadv_tvlv_container_unregister(struct batadv_priv *bat_priv,
                                      u8 type, u8 version)
{
        struct batadv_tvlv_container *tvlv;

        spin_lock_bh(&bat_priv->tvlv.container_list_lock);
        tvlv = batadv_tvlv_container_get(bat_priv, type, version);
        batadv_tvlv_container_remove(bat_priv, tvlv);
        spin_unlock_bh(&bat_priv->tvlv.container_list_lock);
}

/**
 * batadv_tvlv_container_register() - register tvlv type, version and content
 *  to be propagated with each (primary interface) OGM
 * @bat_priv: the bat priv with all the mesh interface information
 * @type: tvlv container type
 * @version: tvlv container version
 * @tvlv_value: tvlv container content
 * @tvlv_value_len: tvlv container content length
 *
 * If a container of the same type and version was already registered the new
 * content is going to replace the old one.
 */
void batadv_tvlv_container_register(struct batadv_priv *bat_priv,
                                    u8 type, u8 version,
                                    void *tvlv_value, u16 tvlv_value_len)
{
        struct batadv_tvlv_container *tvlv_old, *tvlv_new;

        if (!tvlv_value)
                tvlv_value_len = 0;

        tvlv_new = kzalloc(sizeof(*tvlv_new) + tvlv_value_len, GFP_ATOMIC);
        if (!tvlv_new)
                return;

        tvlv_new->tvlv_hdr.version = version;
        tvlv_new->tvlv_hdr.type = type;
        tvlv_new->tvlv_hdr.len = htons(tvlv_value_len);

        memcpy(tvlv_new + 1, tvlv_value, ntohs(tvlv_new->tvlv_hdr.len));
        INIT_HLIST_NODE(&tvlv_new->list);
        kref_init(&tvlv_new->refcount);

        spin_lock_bh(&bat_priv->tvlv.container_list_lock);
        tvlv_old = batadv_tvlv_container_get(bat_priv, type, version);
        batadv_tvlv_container_remove(bat_priv, tvlv_old);

        kref_get(&tvlv_new->refcount);
        hlist_add_head(&tvlv_new->list, &bat_priv->tvlv.container_list);
        spin_unlock_bh(&bat_priv->tvlv.container_list_lock);

        /* don't return reference to new tvlv_container */
        batadv_tvlv_container_put(tvlv_new);
}

/**
 * batadv_tvlv_realloc_packet_buff() - reallocate packet buffer to accommodate
 *  requested packet size
 * @packet_buff: packet buffer
 * @packet_buff_len: packet buffer size
 * @min_packet_len: requested packet minimum size
 * @additional_packet_len: requested additional packet size on top of minimum
 *  size
 *
 * Return: true of the packet buffer could be changed to the requested size,
 * false otherwise.
 */
static bool batadv_tvlv_realloc_packet_buff(unsigned char **packet_buff,
                                            int *packet_buff_len,
                                            int min_packet_len,
                                            int additional_packet_len)
{
        unsigned char *new_buff;

        new_buff = kmalloc(min_packet_len + additional_packet_len, GFP_ATOMIC);

        /* keep old buffer if kmalloc should fail */
        if (!new_buff)
                return false;

        memcpy(new_buff, *packet_buff, min_packet_len);
        kfree(*packet_buff);
        *packet_buff = new_buff;
        *packet_buff_len = min_packet_len + additional_packet_len;

        return true;
}

/**
 * batadv_tvlv_container_ogm_append() - append tvlv container content to given
 *  OGM packet buffer
 * @bat_priv: the bat priv with all the mesh interface information
 * @packet_buff: ogm packet buffer
 * @packet_buff_len: ogm packet buffer size including ogm header and tvlv
 *  content
 * @packet_min_len: ogm header size to be preserved for the OGM itself
 *
 * The ogm packet might be enlarged or shrunk depending on the current size
 * and the size of the to-be-appended tvlv containers.
 *
 * Return: size of all appended tvlv containers in bytes.
 */
u16 batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
                                     unsigned char **packet_buff,
                                     int *packet_buff_len, int packet_min_len)
{
        struct batadv_tvlv_container *tvlv;
        struct batadv_tvlv_hdr *tvlv_hdr;
        u16 tvlv_value_len;
        void *tvlv_value;
        bool ret;

        spin_lock_bh(&bat_priv->tvlv.container_list_lock);
        tvlv_value_len = batadv_tvlv_container_list_size(bat_priv);

        ret = batadv_tvlv_realloc_packet_buff(packet_buff, packet_buff_len,
                                              packet_min_len, tvlv_value_len);

        if (!ret)
                goto end;

        if (!tvlv_value_len)
                goto end;

        tvlv_value = (*packet_buff) + packet_min_len;

        hlist_for_each_entry(tvlv, &bat_priv->tvlv.container_list, list) {
                tvlv_hdr = tvlv_value;
                tvlv_hdr->type = tvlv->tvlv_hdr.type;
                tvlv_hdr->version = tvlv->tvlv_hdr.version;
                tvlv_hdr->len = tvlv->tvlv_hdr.len;
                tvlv_value = tvlv_hdr + 1;
                memcpy(tvlv_value, tvlv + 1, ntohs(tvlv->tvlv_hdr.len));
                tvlv_value = (u8 *)tvlv_value + ntohs(tvlv->tvlv_hdr.len);
        }

end:
        spin_unlock_bh(&bat_priv->tvlv.container_list_lock);
        return tvlv_value_len;
}

/**
 * batadv_tvlv_call_handler() - parse the given tvlv buffer to call the
 *  appropriate handlers
 * @bat_priv: the bat priv with all the mesh interface information
 * @tvlv_handler: tvlv callback function handling the tvlv content
 * @packet_type: indicates for which packet type the TVLV handler is called
 * @orig_node: orig node emitting the ogm packet
 * @skb: the skb the TVLV handler is called for
 * @tvlv_value: tvlv content
 * @tvlv_value_len: tvlv content length
 *
 * Return: success if the handler was not found or the return value of the
 * handler callback.
 */
static int batadv_tvlv_call_handler(struct batadv_priv *bat_priv,
                                    struct batadv_tvlv_handler *tvlv_handler,
                                    u8 packet_type,
                                    struct batadv_orig_node *orig_node,
                                    struct sk_buff *skb, void *tvlv_value,
                                    u16 tvlv_value_len)
{
        unsigned int tvlv_offset;
        u8 *src, *dst;

        if (!tvlv_handler)
                return NET_RX_SUCCESS;

        switch (packet_type) {
        case BATADV_IV_OGM:
        case BATADV_OGM2:
                if (!tvlv_handler->ogm_handler)
                        return NET_RX_SUCCESS;

                if (!orig_node)
                        return NET_RX_SUCCESS;

                tvlv_handler->ogm_handler(bat_priv, orig_node,
                                          BATADV_NO_FLAGS,
                                          tvlv_value, tvlv_value_len);
                tvlv_handler->flags |= BATADV_TVLV_HANDLER_OGM_CALLED;
                break;
        case BATADV_UNICAST_TVLV:
                if (!skb)
                        return NET_RX_SUCCESS;

                if (!tvlv_handler->unicast_handler)
                        return NET_RX_SUCCESS;

                src = ((struct batadv_unicast_tvlv_packet *)skb->data)->src;
                dst = ((struct batadv_unicast_tvlv_packet *)skb->data)->dst;

                return tvlv_handler->unicast_handler(bat_priv, src,
                                                     dst, tvlv_value,
                                                     tvlv_value_len);
        case BATADV_MCAST:
                if (!skb)
                        return NET_RX_SUCCESS;

                if (!tvlv_handler->mcast_handler)
                        return NET_RX_SUCCESS;

                tvlv_offset = (unsigned char *)tvlv_value - skb->data;
                skb_set_network_header(skb, tvlv_offset);
                skb_set_transport_header(skb, tvlv_offset + tvlv_value_len);

                return tvlv_handler->mcast_handler(bat_priv, skb);
        }

        return NET_RX_SUCCESS;
}

/**
 * batadv_tvlv_containers_process() - parse the given tvlv buffer to call the
 *  appropriate handlers
 * @bat_priv: the bat priv with all the mesh interface information
 * @packet_type: indicates for which packet type the TVLV handler is called
 * @orig_node: orig node emitting the ogm packet
 * @skb: the skb the TVLV handler is called for
 * @tvlv_value: tvlv content
 * @tvlv_value_len: tvlv content length
 *
 * Return: success when processing an OGM or the return value of all called
 * handler callbacks.
 */
int batadv_tvlv_containers_process(struct batadv_priv *bat_priv,
                                   u8 packet_type,
                                   struct batadv_orig_node *orig_node,
                                   struct sk_buff *skb, void *tvlv_value,
                                   u16 tvlv_value_len)
{
        struct batadv_tvlv_handler *tvlv_handler;
        struct batadv_tvlv_hdr *tvlv_hdr;
        u16 tvlv_value_cont_len;
        u8 cifnotfound = BATADV_TVLV_HANDLER_OGM_CIFNOTFND;
        int ret = NET_RX_SUCCESS;

        while (tvlv_value_len >= sizeof(*tvlv_hdr)) {
                tvlv_hdr = tvlv_value;
                tvlv_value_cont_len = ntohs(tvlv_hdr->len);
                tvlv_value = tvlv_hdr + 1;
                tvlv_value_len -= sizeof(*tvlv_hdr);

                if (tvlv_value_cont_len > tvlv_value_len)
                        break;

                tvlv_handler = batadv_tvlv_handler_get(bat_priv,
                                                       tvlv_hdr->type,
                                                       tvlv_hdr->version);

                ret |= batadv_tvlv_call_handler(bat_priv, tvlv_handler,
                                                packet_type, orig_node, skb,
                                                tvlv_value,
                                                tvlv_value_cont_len);
                batadv_tvlv_handler_put(tvlv_handler);
                tvlv_value = (u8 *)tvlv_value + tvlv_value_cont_len;
                tvlv_value_len -= tvlv_value_cont_len;
        }

        if (packet_type != BATADV_IV_OGM &&
            packet_type != BATADV_OGM2)
                return ret;

        rcu_read_lock();
        hlist_for_each_entry_rcu(tvlv_handler,
                                 &bat_priv->tvlv.handler_list, list) {
                if (!tvlv_handler->ogm_handler)
                        continue;

                if ((tvlv_handler->flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND) &&
                    !(tvlv_handler->flags & BATADV_TVLV_HANDLER_OGM_CALLED))
                        tvlv_handler->ogm_handler(bat_priv, orig_node,
                                                  cifnotfound, NULL, 0);

                tvlv_handler->flags &= ~BATADV_TVLV_HANDLER_OGM_CALLED;
        }
        rcu_read_unlock();

        return NET_RX_SUCCESS;
}

/**
 * batadv_tvlv_ogm_receive() - process an incoming ogm and call the appropriate
 *  handlers
 * @bat_priv: the bat priv with all the mesh interface information
 * @batadv_ogm_packet: ogm packet containing the tvlv containers
 * @orig_node: orig node emitting the ogm packet
 */
void batadv_tvlv_ogm_receive(struct batadv_priv *bat_priv,
                             struct batadv_ogm_packet *batadv_ogm_packet,
                             struct batadv_orig_node *orig_node)
{
        void *tvlv_value;
        u16 tvlv_value_len;

        if (!batadv_ogm_packet)
                return;

        tvlv_value_len = ntohs(batadv_ogm_packet->tvlv_len);
        if (!tvlv_value_len)
                return;

        tvlv_value = batadv_ogm_packet + 1;

        batadv_tvlv_containers_process(bat_priv, BATADV_IV_OGM, orig_node, NULL,
                                       tvlv_value, tvlv_value_len);
}

/**
 * batadv_tvlv_handler_register() - register tvlv handler based on the provided
 *  type and version (both need to match) for ogm tvlv payload and/or unicast
 *  payload
 * @bat_priv: the bat priv with all the mesh interface information
 * @optr: ogm tvlv handler callback function. This function receives the orig
 *  node, flags and the tvlv content as argument to process.
 * @uptr: unicast tvlv handler callback function. This function receives the
 *  source & destination of the unicast packet as well as the tvlv content
 *  to process.
 * @mptr: multicast packet tvlv handler callback function. This function
 *  receives the full skb to process, with the skb network header pointing
 *  to the current tvlv and the skb transport header pointing to the first
 *  byte after the current tvlv.
 * @type: tvlv handler type to be registered
 * @version: tvlv handler version to be registered
 * @flags: flags to enable or disable TVLV API behavior
 */
void batadv_tvlv_handler_register(struct batadv_priv *bat_priv,
                                  void (*optr)(struct batadv_priv *bat_priv,
                                               struct batadv_orig_node *orig,
                                               u8 flags,
                                               void *tvlv_value,
                                               u16 tvlv_value_len),
                                  int (*uptr)(struct batadv_priv *bat_priv,
                                              u8 *src, u8 *dst,
                                              void *tvlv_value,
                                              u16 tvlv_value_len),
                                  int (*mptr)(struct batadv_priv *bat_priv,
                                              struct sk_buff *skb),
                                  u8 type, u8 version, u8 flags)
{
        struct batadv_tvlv_handler *tvlv_handler;

        spin_lock_bh(&bat_priv->tvlv.handler_list_lock);

        tvlv_handler = batadv_tvlv_handler_get(bat_priv, type, version);
        if (tvlv_handler) {
                spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
                batadv_tvlv_handler_put(tvlv_handler);
                return;
        }

        tvlv_handler = kzalloc_obj(*tvlv_handler, GFP_ATOMIC);
        if (!tvlv_handler) {
                spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
                return;
        }

        tvlv_handler->ogm_handler = optr;
        tvlv_handler->unicast_handler = uptr;
        tvlv_handler->mcast_handler = mptr;
        tvlv_handler->type = type;
        tvlv_handler->version = version;
        tvlv_handler->flags = flags;
        kref_init(&tvlv_handler->refcount);
        INIT_HLIST_NODE(&tvlv_handler->list);

        kref_get(&tvlv_handler->refcount);
        hlist_add_head_rcu(&tvlv_handler->list, &bat_priv->tvlv.handler_list);
        spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);

        /* don't return reference to new tvlv_handler */
        batadv_tvlv_handler_put(tvlv_handler);
}

/**
 * batadv_tvlv_handler_unregister() - unregister tvlv handler based on the
 *  provided type and version (both need to match)
 * @bat_priv: the bat priv with all the mesh interface information
 * @type: tvlv handler type to be unregistered
 * @version: tvlv handler version to be unregistered
 */
void batadv_tvlv_handler_unregister(struct batadv_priv *bat_priv,
                                    u8 type, u8 version)
{
        struct batadv_tvlv_handler *tvlv_handler;

        tvlv_handler = batadv_tvlv_handler_get(bat_priv, type, version);
        if (!tvlv_handler)
                return;

        batadv_tvlv_handler_put(tvlv_handler);
        spin_lock_bh(&bat_priv->tvlv.handler_list_lock);
        hlist_del_rcu(&tvlv_handler->list);
        spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
        batadv_tvlv_handler_put(tvlv_handler);
}

/**
 * batadv_tvlv_unicast_send() - send a unicast packet with tvlv payload to the
 *  specified host
 * @bat_priv: the bat priv with all the mesh interface information
 * @src: source mac address of the unicast packet
 * @dst: destination mac address of the unicast packet
 * @type: tvlv type
 * @version: tvlv version
 * @tvlv_value: tvlv content
 * @tvlv_value_len: tvlv content length
 */
void batadv_tvlv_unicast_send(struct batadv_priv *bat_priv, const u8 *src,
                              const u8 *dst, u8 type, u8 version,
                              void *tvlv_value, u16 tvlv_value_len)
{
        struct batadv_unicast_tvlv_packet *unicast_tvlv_packet;
        struct batadv_tvlv_hdr *tvlv_hdr;
        struct batadv_orig_node *orig_node;
        struct sk_buff *skb;
        unsigned char *tvlv_buff;
        unsigned int tvlv_len;
        ssize_t hdr_len = sizeof(*unicast_tvlv_packet);

        orig_node = batadv_orig_hash_find(bat_priv, dst);
        if (!orig_node)
                return;

        tvlv_len = sizeof(*tvlv_hdr) + tvlv_value_len;

        skb = netdev_alloc_skb_ip_align(NULL, ETH_HLEN + hdr_len + tvlv_len);
        if (!skb)
                goto out;

        skb->priority = TC_PRIO_CONTROL;
        skb_reserve(skb, ETH_HLEN);
        tvlv_buff = skb_put(skb, sizeof(*unicast_tvlv_packet) + tvlv_len);
        unicast_tvlv_packet = (struct batadv_unicast_tvlv_packet *)tvlv_buff;
        unicast_tvlv_packet->packet_type = BATADV_UNICAST_TVLV;
        unicast_tvlv_packet->version = BATADV_COMPAT_VERSION;
        unicast_tvlv_packet->ttl = BATADV_TTL;
        unicast_tvlv_packet->reserved = 0;
        unicast_tvlv_packet->tvlv_len = htons(tvlv_len);
        unicast_tvlv_packet->align = 0;
        ether_addr_copy(unicast_tvlv_packet->src, src);
        ether_addr_copy(unicast_tvlv_packet->dst, dst);

        tvlv_buff = (unsigned char *)(unicast_tvlv_packet + 1);
        tvlv_hdr = (struct batadv_tvlv_hdr *)tvlv_buff;
        tvlv_hdr->version = version;
        tvlv_hdr->type = type;
        tvlv_hdr->len = htons(tvlv_value_len);
        tvlv_buff += sizeof(*tvlv_hdr);
        memcpy(tvlv_buff, tvlv_value, tvlv_value_len);

        batadv_send_skb_to_orig(skb, orig_node, NULL);
out:
        batadv_orig_node_put(orig_node);
}