1 files changed, 491 insertions, 0 deletions
diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
new file mode 100644
index 000000000000..271d321b3a04
--- /dev/null
+++ b/net/batman-adv/fragmentation.c
@@ -0,0 +1,491 @@
+/* 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;
+}