1 files changed, 565 insertions, 0 deletions

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
new file mode 100644
index 000000000..895d834d4
--- /dev/null
+++ b/net/batman-adv/fragmentation.c
@@ -0,0 +1,565 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2013-2020  B.A.T.M.A.N. contributors:
+ *
+ * Martin Hundebøll <martin@hundeboll.net>
+ */
+
+#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/kernel.h>
+#include <linux/lockdep.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 "routing.h"
+#include "send.h"
+#include "soft-interface.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_orig_node *orig_node_dst;
+	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;
+	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->ttl--;
+		batadv_send_unicast_skb(skb, neigh_node);
+		ret = true;
+	}
+
+out:
+	if (orig_node_dst)
+		batadv_orig_node_put(orig_node_dst);
+	if (neigh_node)
+		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;
+}