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-rw-r--r--net/batman-adv/fragmentation.c370
1 files changed, 370 insertions, 0 deletions
diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
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+/* 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;
+}

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