diff options
Diffstat (limited to 'net/batman-adv/fragmentation.c')
| -rw-r--r-- | net/batman-adv/fragmentation.c | 491 |
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 00000000000..271d321b3a0 --- /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; +} |