// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) B.A.T.M.A.N. contributors:
*
* Martin Hundebøll <[email protected]>
*/
#include "fragmentation.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/jiffies.h>
#include <linux/lockdep.h>
#include <linux/minmax.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <uapi/linux/batadv_packet.h>
#include "hard-interface.h"
#include "originator.h"
#include "send.h"
/**
* batadv_frag_clear_chain() - delete entries in the fragment buffer chain
* @head: head of chain with entries.
* @dropped: whether the chain is cleared because all fragments are dropped
*
* Free fragments in the passed hlist. Should be called with appropriate lock.
*/
static void batadv_frag_clear_chain(struct hlist_head *head, bool dropped)
{
struct batadv_frag_list_entry *entry;
struct hlist_node *node;
hlist_for_each_entry_safe(entry, node, head, list) {
hlist_del(&entry->list);
if (dropped)
kfree_skb(entry->skb);
else
consume_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;
u8 i;
for (i = 0; i < BATADV_FRAG_BUFFER_COUNT; i++) {
chain = &orig_node->fragments[i];
spin_lock_bh(&chain->lock);
if (!check_cb || check_cb(chain)) {
batadv_frag_clear_chain(&chain->fragment_list, true);
chain->size = 0;
}
spin_unlock_bh(&chain->lock);
}
}
/**
* batadv_frag_size_limit() - maximum possible size of packet to be fragmented
*
* Return: 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.
*
* Return: true if chain is empty and the 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,
u16 seqno)
{
lockdep_assert_held(&chain->lock);
if (chain->seqno == seqno)
return false;
if (!hlist_empty(&chain->fragment_list))
batadv_frag_clear_chain(&chain->fragment_list, true);
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.
*
* Return: 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_list_entry *frag_entry_last = NULL;
struct batadv_frag_packet *frag_packet;
u8 bucket;
u16 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->fragment_list);
chain->size = skb->len - hdr_size;
chain->timestamp = jiffies;
chain->total_size = ntohs(frag_packet->total_size);
ret = true;
goto out;
}
/* Find the position for the new fragment. */
hlist_for_each_entry(frag_entry_curr, &chain->fragment_list, 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;
}
/* store current entry because it could be the last in list */
frag_entry_last = frag_entry_curr;
}
/* Reached the end of the list, so insert after 'frag_entry_last'. */
if (likely(frag_entry_last)) {
hlist_add_behind(&frag_entry_new->list, &frag_entry_last->list);
chain->size += skb->len - hdr_size;
chain->timestamp = jiffies;
ret = true;
}
out:
if (chain->size > batadv_frag_size_limit() ||
chain->total_size != ntohs(frag_packet->total_size) ||
chain->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. Don't allow
* packets to have different total_size.
*/
batadv_frag_clear_chain(&chain->fragment_list, true);
chain->size = 0;
} else if (ntohs(frag_packet->total_size) == chain->size) {
/* All fragments received. Hand over chain to caller. */
hlist_move_list(&chain->fragment_list, chain_out);
chain->size = 0;
}
err_unlock:
spin_unlock_bh(&chain->lock);
err:
if (!ret) {
kfree(frag_entry_new);
kfree_skb(skb);
}
return ret;
}
/**
* batadv_frag_merge_packets() - merge a chain of fragments
* @chain: head of chain with fragments
*
* 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.
*
* Return: the merged skb or NULL on error.
*/
static struct sk_buff *
batadv_frag_merge_packets(struct hlist_head *chain)
{
struct batadv_frag_packet *packet;
struct batadv_frag_list_entry *entry;
struct sk_buff *skb_out;
int size, hdr_size = sizeof(struct batadv_frag_packet);
bool dropped = false;
/* 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);
packet = (struct batadv_frag_packet *)skb_out->data;
size = ntohs(packet->total_size) + hdr_size;
/* Make room for the rest of the fragments. */
if (pskb_expand_head(skb_out, 0, size - skb_out->len, GFP_ATOMIC) < 0) {
kfree_skb(skb_out);
skb_out = NULL;
dropped = true;
goto free;
}
/* Move the existing MAC header to just before the payload. (Override
* the fragment header.)
*/
skb_pull(skb_out, hdr_size);
skb_out->ip_summed = CHECKSUM_NONE;
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;
skb_put_data(skb_out, entry->skb->data + hdr_size, size);
}
free:
/* Locking is not needed, because 'chain' is not part of any orig. */
batadv_frag_clear_chain(chain, dropped);
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 free skb.
*
* Return: true when the packet is merged or buffered, false when skb is not
* used.
*/
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);
if (!skb_out)
goto out_err;
out:
ret = true;
out_err:
*skb = skb_out;
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.
*
* Return: 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_neigh_node *neigh_node = NULL;
struct batadv_frag_packet *packet;
u16 total_size;
bool ret = false;
packet = (struct batadv_frag_packet *)skb->data;
neigh_node = batadv_orig_to_router(bat_priv, packet->dest, 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->ttl--;
batadv_send_unicast_skb(skb, neigh_node);
ret = true;
}
out:
batadv_neigh_node_put(neigh_node);
return ret;
}
/**
* batadv_frag_create() - create a fragment from skb
* @net_dev: outgoing device for fragment
* @skb: skb to create fragment from
* @frag_head: header to use in new fragment
* @fragment_size: 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.
*
* Return: the new fragment, NULL on error.
*/
static struct sk_buff *batadv_frag_create(struct net_device *net_dev,
struct sk_buff *skb,
struct batadv_frag_packet *frag_head,
unsigned int fragment_size)
{
unsigned int ll_reserved = LL_RESERVED_SPACE(net_dev);
unsigned int tailroom = net_dev->needed_tailroom;
struct sk_buff *skb_fragment;
unsigned int header_size = sizeof(*frag_head);
unsigned int mtu = fragment_size + header_size;
skb_fragment = dev_alloc_skb(ll_reserved + mtu + tailroom);
if (!skb_fragment)
goto err;
skb_fragment->priority = skb->priority;
/* Eat the last mtu-bytes of the skb */
skb_reserve(skb_fragment, ll_reserved + header_size);
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
*
* Return: the netdev tx status or a negative errno code on a failure
*/
int batadv_frag_send_packet(struct sk_buff *skb,
struct batadv_orig_node *orig_node,
struct batadv_neigh_node *neigh_node)
{
struct net_device *net_dev = neigh_node->if_incoming->net_dev;
struct batadv_priv *bat_priv;
struct batadv_hard_iface *primary_if = NULL;
struct batadv_frag_packet frag_header;
struct sk_buff *skb_fragment;
unsigned int mtu = net_dev->mtu;
unsigned int header_size = sizeof(frag_header);
unsigned int max_fragment_size, num_fragments;
int ret;
/* To avoid merge and refragmentation at next-hops we never send
* fragments larger than BATADV_FRAG_MAX_FRAG_SIZE
*/
mtu = min_t(unsigned int, mtu, BATADV_FRAG_MAX_FRAG_SIZE);
max_fragment_size = mtu - header_size;
if (skb->len == 0 || max_fragment_size == 0)
return -EINVAL;
num_fragments = (skb->len - 1) / max_fragment_size + 1;
max_fragment_size = (skb->len - 1) / num_fragments + 1;
/* Don't even try to fragment, if we need more than 16 fragments */
if (num_fragments > BATADV_FRAG_MAX_FRAGMENTS) {
ret = -EAGAIN;
goto free_skb;
}
bat_priv = orig_node->bat_priv;
primary_if = batadv_primary_if_get_selected(bat_priv);
if (!primary_if) {
ret = -EINVAL;
goto free_skb;
}
/* GRO might have added fragments to the fragment list instead of
* frags[]. But this is not handled by skb_split and must be
* linearized to avoid incorrect length information after all
* batman-adv fragments were created and submitted to the
* hard-interface
*/
if (skb_has_frag_list(skb) && __skb_linearize(skb)) {
ret = -ENOMEM;
goto free_skb;
}
/* Create one header to be copied to all fragments */
frag_header.packet_type = BATADV_UNICAST_FRAG;
frag_header.version = BATADV_COMPAT_VERSION;
frag_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);
/* skb->priority values from 256->263 are magic values to
* directly indicate a specific 802.1d priority. This is used
* to allow 802.1d priority to be passed directly in from VLAN
* tags, etc.
*/
if (skb->priority >= 256 && skb->priority <= 263)
frag_header.priority = skb->priority - 256;
else
frag_header.priority = 0;
ether_addr_copy(frag_header.orig, primary_if->net_dev->dev_addr);
ether_addr_copy(frag_header.dest, orig_node->orig);
/* Eat and send fragments from the tail of skb */
while (skb->len > max_fragment_size) {
/* The initial check in this function should cover this case */
if (unlikely(frag_header.no == BATADV_FRAG_MAX_FRAGMENTS - 1)) {
ret = -EINVAL;
goto put_primary_if;
}
skb_fragment = batadv_frag_create(net_dev, skb, &frag_header,
max_fragment_size);
if (!skb_fragment) {
ret = -ENOMEM;
goto put_primary_if;
}
batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_TX);
batadv_add_counter(bat_priv, BATADV_CNT_FRAG_TX_BYTES,
skb_fragment->len + ETH_HLEN);
ret = batadv_send_unicast_skb(skb_fragment, neigh_node);
if (ret != NET_XMIT_SUCCESS) {
ret = NET_XMIT_DROP;
goto put_primary_if;
}
frag_header.no++;
}
/* make sure that there is at least enough head for the fragmentation
* and ethernet headers
*/
ret = skb_cow_head(skb, ETH_HLEN + header_size);
if (ret < 0)
goto put_primary_if;
skb_push(skb, header_size);
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);
ret = batadv_send_unicast_skb(skb, neigh_node);
/* skb was consumed */
skb = NULL;
put_primary_if:
batadv_hardif_put(primary_if);
free_skb:
kfree_skb(skb);
return ret;
}
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