/* Copyright (C) 2013 B.A.T.M.A.N. contributors:
*
* Martin Hundebøll <martin@hundeboll.net>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA
*/
#include "main.h"
#include "fragmentation.h"
#include "send.h"
#include "originator.h"
#include "routing.h"
#include "hard-interface.h"
#include "soft-interface.h"
/**
* batadv_frag_clear_chain - delete entries in the fragment buffer chain
* @head: head of chain with entries.
*
* Free fragments in the passed hlist. Should be called with appropriate lock.
*/
static void batadv_frag_clear_chain(struct hlist_head *head)
{
struct batadv_frag_list_entry *entry;
struct hlist_node *node;
hlist_for_each_entry_safe(entry, node, head, list) {
hlist_del(&entry->list);
kfree_skb(entry->skb);
kfree(entry);
}
}
/**
* batadv_frag_purge_orig - free fragments associated to an orig
* @orig_node: originator to free fragments from
* @check_cb: optional function to tell if an entry should be purged
*/
void batadv_frag_purge_orig(struct batadv_orig_node *orig_node,
bool (*check_cb)(struct batadv_frag_table_entry *))
{
struct batadv_frag_table_entry *chain;
uint8_t i;
for (i = 0; i < BATADV_FRAG_BUFFER_COUNT; i++) {
chain = &orig_node->fragments[i];
spin_lock_bh(&orig_node->fragments[i].lock);
if (!check_cb || check_cb(chain)) {
batadv_frag_clear_chain(&orig_node->fragments[i].head);
orig_node->fragments[i].size = 0;
}
spin_unlock_bh(&orig_node->fragments[i].lock);
}
}
/**
* batadv_frag_size_limit - maximum possible size of packet to be fragmented
*
* Returns the maximum size of payload that can be fragmented.
*/
static int batadv_frag_size_limit(void)
{
int limit = BATADV_FRAG_MAX_FRAG_SIZE;
limit -= sizeof(struct batadv_frag_packet);
limit *= BATADV_FRAG_MAX_FRAGMENTS;
return limit;
}
/**
* batadv_frag_init_chain - check and prepare fragment chain for new fragment
* @chain: chain in fragments table to init
* @seqno: sequence number of the received fragment
*
* Make chain ready for a fragment with sequence number "seqno". Delete existing
* entries if they have an "old" sequence number.
*
* Caller must hold chain->lock.
*
* Returns true if chain is empty and caller can just insert the new fragment
* without searching for the right position.
*/
static bool batadv_frag_init_chain(struct batadv_frag_table_entry *chain,
uint16_t seqno)
{
if (chain->seqno == seqno)
return false;
if (!hlist_empty(&chain->head))
batadv_frag_clear_chain(&chain->head);
chain->size = 0;
chain->seqno = seqno;
return true;
}
/**
* batadv_frag_insert_packet - insert a fragment into a fragment chain
* @orig_node: originator that the fragment was received from
* @skb: skb to insert
* @chain_out: list head to attach complete chains of fragments to
*
* Insert a new fragment into the reverse ordered chain in the right table
* entry. The hash table entry is cleared if "old" fragments exist in it.
*
* Returns true if skb is buffered, false on error. If the chain has all the
* fragments needed to merge the packet, the chain is moved to the passed head
* to avoid locking the chain in the table.
*/
static bool batadv_frag_insert_packet(struct batadv_orig_node *orig_node,
struct sk_buff *skb,
struct hlist_head *chain_out)
{
struct batadv_frag_table_entry *chain;
struct batadv_frag_list_entry *frag_entry_new = NULL, *frag_entry_curr;
struct batadv_frag_packet *frag_packet;
uint8_t bucket;
uint16_t seqno, hdr_size = sizeof(struct batadv_frag_packet);
bool ret = false;
/* Linearize packet to avoid linearizing 16 packets in a row when doing
* the later merge. Non-linear merge should be added to remove this
* linearization.
*/
if (skb_linearize(skb) < 0)
goto err;
frag_packet = (struct batadv_frag_packet *)skb->data;
seqno = ntohs(frag_packet->seqno);
bucket = seqno % BATADV_FRAG_BUFFER_COUNT;
frag_entry_new = kmalloc(sizeof(*frag_entry_new), GFP_ATOMIC);
if (!frag_entry_new)
goto err;
frag_entry_new->skb = skb;
frag_entry_new->no = frag_packet->no;
/* Select entry in the "chain table" and delete any prior fragments
* with another sequence number. batadv_frag_init_chain() returns true,
* if the list is empty at return.
*/
chain = &orig_node->fragments[bucket];
spin_lock_bh(&chain->lock);
if (batadv_frag_init_chain(chain, seqno)) {
hlist_add_head(&frag_entry_new->list, &chain->head);
chain->size = skb->len - hdr_size;
chain->timestamp = jiffies;
ret = true;
goto out;
}
/* Find the position for the new fragment. */
hlist_for_each_entry(frag_entry_curr, &chain->head, list) {
/* Drop packet if fragment already exists. */
if (frag_entry_curr->no == frag_entry_new->no)
goto err_unlock;
/* Order fragments from highest to lowest. */
if (frag_entry_curr->no < frag_entry_new->no) {
hlist_add_before(&frag_entry_new->list,
&frag_entry_curr->list);
chain->size += skb->len - hdr_size;
chain->timestamp = jiffies;
ret = true;
goto out;
}
}
/* Reached the end of the list, so insert after 'frag_entry_curr'. */
if (likely(frag_entry_curr)) {
hlist_add_after(&frag_entry_curr->list, &frag_entry_new->list);
chain->size += skb->len - hdr_size;
chain->timestamp = jiffies;
ret = true;
}
out:
if (chain->size > batadv_frag_size_limit() ||
ntohs(frag_packet->total_size) > batadv_frag_size_limit()) {
/* Clear chain if total size of either the list or the packet
* exceeds the maximum size of one merged packet.
*/
batadv_frag_clear_chain(&chain->head);
chain->size = 0;
} else if (ntohs(frag_packet->total_size) == chain->size) {
/* All fragments received. Hand over chain to caller. */
hlist_move_list(&chain->head, chain_out);
chain->size = 0;
}
err_unlock:
spin_unlock_bh(&chain->lock);
err:
if (!ret)
kfree(frag_entry_new);
return ret;
}
/**
* batadv_frag_merge_packets - merge a chain of fragments
* @chain: head of chain with fragments
* @skb: packet with total size of skb after merging
*
* Expand the first skb in the chain and copy the content of the remaining
* skb's into the expanded one. After doing so, clear the chain.
*
* Returns the merged skb or NULL on error.
*/
static struct sk_buff *
batadv_frag_merge_packets(struct hlist_head *chain, struct sk_buff *skb)
{
struct batadv_frag_packet *packet;
struct batadv_frag_list_entry *entry;
struct sk_buff *skb_out = NULL;
int size, hdr_size = sizeof(struct batadv_frag_packet);
/* Make sure incoming skb has non-bogus data. */
packet = (struct batadv_frag_packet *)skb->data;
size = ntohs(packet->total_size);
if (size > batadv_frag_size_limit())
goto free;
/* Remove first entry, as this is the destination for the rest of the
* fragments.
*/
entry = hlist_entry(chain->first, struct batadv_frag_list_entry, list);
hlist_del(&entry->list);
skb_out = entry->skb;
kfree(entry);
/* Make room for the rest of the fragments. */
if (pskb_expand_head(skb_out, 0, size - skb->len, GFP_ATOMIC) < 0) {
kfree_skb(skb_out);
skb_out = NULL;
goto free;
}
/* Move the existing MAC header to just before the payload. (Override
* the fragment header.)
*/
skb_pull_rcsum(skb_out, hdr_size);
memmove(skb_out->data - ETH_HLEN, skb_mac_header(skb_out), ETH_HLEN);
skb_set_mac_header(skb_out, -ETH_HLEN);
skb_reset_network_header(skb_out);
skb_reset_transport_header(skb_out);
/* Copy the payload of the each fragment into the last skb */
hlist_for_each_entry(entry, chain, list) {
size = entry->skb->len - hdr_size;
memcpy(skb_put(skb_out, size), entry->skb->data + hdr_size,
size);
}
free:
/* Locking is not needed, because 'chain' is not part of any orig. */
batadv_frag_clear_chain(chain);
return skb_out;
}
/**
* batadv_frag_skb_buffer - buffer fragment for later merge
* @skb: skb to buffer
* @orig_node_src: originator that the skb is received from
*
* Add fragment to buffer and merge fragments if possible.
*
* There are three possible outcomes: 1) Packet is merged: Return true and
* set *skb to merged packet; 2) Packet is buffered: Return true and set *skb
* to NULL; 3) Error: Return false and leave skb as is.
*/
bool batadv_frag_skb_buffer(struct sk_buff **skb,
struct batadv_orig_node *orig_node_src)
{
struct sk_buff *skb_out = NULL;
struct hlist_head head = HLIST_HEAD_INIT;
bool ret = false;
/* Add packet to buffer and table entry if merge is possible. */
if (!batadv_frag_insert_packet(orig_node_src, *skb, &head))
goto out_err;
/* Leave if more fragments are needed to merge. */
if (hlist_empty(&head))
goto out;
skb_out = batadv_frag_merge_packets(&head, *skb);
if (!skb_out)
goto out_err;
out:
*skb = skb_out;
ret = true;
out_err:
return ret;
}
/**
* batadv_frag_skb_fwd - forward fragments that would exceed MTU when merged
* @skb: skb to forward
* @recv_if: interface that the skb is received on
* @orig_node_src: originator that the skb is received from
*
* Look up the next-hop of the fragments payload and check if the merged packet
* will exceed the MTU towards the next-hop. If so, the fragment is forwarded
* without merging it.
*
* Returns true if the fragment is consumed/forwarded, false otherwise.
*/
bool batadv_frag_skb_fwd(struct sk_buff *skb,
struct batadv_hard_iface *recv_if,
struct batadv_orig_node *orig_node_src)
{
struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
struct batadv_orig_node *orig_node_dst = NULL;
struct batadv_neigh_node *neigh_node = NULL;
struct batadv_frag_packet *packet;
uint16_t total_size;
bool ret = false;
packet = (struct batadv_frag_packet *)skb->data;
orig_node_dst = batadv_orig_hash_find(bat_priv, packet->dest);
if (!orig_node_dst)
goto out;
neigh_node = batadv_find_router(bat_priv, orig_node_dst, recv_if);
if (!neigh_node)
goto out;
/* Forward the fragment, if the merged packet would be too big to
* be assembled.
*/
total_size = ntohs(packet->total_size);
if (total_size > neigh_node->if_incoming->net_dev->mtu) {
batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_FWD);
batadv_add_counter(bat_priv, BATADV_CNT_FRAG_FWD_BYTES,
skb->len + ETH_HLEN);
packet->header.ttl--;
batadv_send_skb_packet(skb, neigh_node->if_incoming,
neigh_node->addr);
ret = true;
}
out:
if (orig_node_dst)
batadv_orig_node_free_ref(orig_node_dst);
if (neigh_node)
batadv_neigh_node_free_ref(neigh_node);
return ret;
}
/**
* batadv_frag_create - create a fragment from skb
* @skb: skb to create fragment from
* @frag_head: header to use in new fragment
* @mtu: size of new fragment
*
* Split the passed skb into two fragments: A new one with size matching the
* passed mtu and the old one with the rest. The new skb contains data from the
* tail of the old skb.
*
* Returns the new fragment, NULL on error.
*/
static struct sk_buff *batadv_frag_create(struct sk_buff *skb,
struct batadv_frag_packet *frag_head,
unsigned int mtu)
{
struct sk_buff *skb_fragment;
unsigned header_size = sizeof(*frag_head);
unsigned fragment_size = mtu - header_size;
skb_fragment = netdev_alloc_skb(NULL, mtu + ETH_HLEN);
if (!skb_fragment)
goto err;
skb->priority = TC_PRIO_CONTROL;
/* Eat the last mtu-bytes of the skb */
skb_reserve(skb_fragment, header_size + ETH_HLEN);
skb_split(skb, skb_fragment, skb->len - fragment_size);
/* Add the header */
skb_push(skb_fragment, header_size);
memcpy(skb_fragment->data, frag_head, header_size);
err:
return skb_fragment;
}
/**
* batadv_frag_send_packet - create up to 16 fragments from the passed skb
* @skb: skb to create fragments from
* @orig_node: final destination of the created fragments
* @neigh_node: next-hop of the created fragments
*
* Returns true on success, false otherwise.
*/
bool batadv_frag_send_packet(struct sk_buff *skb,
struct batadv_orig_node *orig_node,
struct batadv_neigh_node *neigh_node)
{
struct batadv_priv *bat_priv;
struct batadv_hard_iface *primary_if;
struct batadv_frag_packet frag_header;
struct sk_buff *skb_fragment;
unsigned mtu = neigh_node->if_incoming->net_dev->mtu;
unsigned header_size = sizeof(frag_header);
unsigned max_fragment_size, max_packet_size;
/* To avoid merge and refragmentation at next-hops we never send
* fragments larger than BATADV_FRAG_MAX_FRAG_SIZE
*/
mtu = min_t(unsigned, mtu, BATADV_FRAG_MAX_FRAG_SIZE);
max_fragment_size = (mtu - header_size - ETH_HLEN);
max_packet_size = max_fragment_size * BATADV_FRAG_MAX_FRAGMENTS;
/* Don't even try to fragment, if we need more than 16 fragments */
if (skb->len > max_packet_size)
goto out_err;
bat_priv = orig_node->bat_priv;
primary_if = batadv_primary_if_get_selected(bat_priv);
if (!primary_if)
goto out_err;
/* Create one header to be copied to all fragments */
frag_header.header.packet_type = BATADV_UNICAST_FRAG;
frag_header.header.version = BATADV_COMPAT_VERSION;
frag_header.header.ttl = BATADV_TTL;
frag_header.seqno = htons(atomic_inc_return(&bat_priv->frag_seqno));
frag_header.reserved = 0;
frag_header.no = 0;
frag_header.total_size = htons(skb->len);
memcpy(frag_header.orig, primary_if->net_dev->dev_addr, ETH_ALEN);
memcpy(frag_header.dest, orig_node->orig, ETH_ALEN);
/* Eat and send fragments from the tail of skb */
while (skb->len > max_fragment_size) {
skb_fragment = batadv_frag_create(skb, &frag_header, mtu);
if (!skb_fragment)
goto out_err;
batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX);
batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES,
skb_fragment->len + ETH_HLEN);
batadv_send_skb_packet(skb_fragment, neigh_node->if_incoming,
neigh_node->addr);
frag_header.no++;
/* The initial check in this function should cover this case */
if (frag_header.no == BATADV_FRAG_MAX_FRAGMENTS - 1)
goto out_err;
}
/* Make room for the fragment header. */
if (batadv_skb_head_push(skb, header_size) < 0 ||
pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0)
goto out_err;
memcpy(skb->data, &frag_header, header_size);
/* Send the last fragment */
batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX);
batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES,
skb->len + ETH_HLEN);
batadv_send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr);
return true;
out_err:
return false;
}
