It might be possible that 2 threads access the same data in the same rcu grace period. The first thread calls call_rcu() to decrement the refcount and free the data while the second thread increases the refcount to use the data. To avoid this race condition all refcount operations have to be atomic. Reported-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
358 lines
9.1 KiB
C
358 lines
9.1 KiB
C
/*
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* Copyright (C) 2010-2011 B.A.T.M.A.N. contributors:
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*
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* Andreas Langer
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA
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*
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*/
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#include "main.h"
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#include "unicast.h"
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#include "send.h"
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#include "soft-interface.h"
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#include "gateway_client.h"
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#include "originator.h"
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#include "hash.h"
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#include "translation-table.h"
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#include "routing.h"
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#include "hard-interface.h"
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static struct sk_buff *frag_merge_packet(struct list_head *head,
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struct frag_packet_list_entry *tfp,
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struct sk_buff *skb)
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{
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struct unicast_frag_packet *up =
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(struct unicast_frag_packet *)skb->data;
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struct sk_buff *tmp_skb;
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struct unicast_packet *unicast_packet;
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int hdr_len = sizeof(struct unicast_packet);
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int uni_diff = sizeof(struct unicast_frag_packet) - hdr_len;
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/* set skb to the first part and tmp_skb to the second part */
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if (up->flags & UNI_FRAG_HEAD) {
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tmp_skb = tfp->skb;
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} else {
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tmp_skb = skb;
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skb = tfp->skb;
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}
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skb_pull(tmp_skb, sizeof(struct unicast_frag_packet));
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if (pskb_expand_head(skb, 0, tmp_skb->len, GFP_ATOMIC) < 0) {
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/* free buffered skb, skb will be freed later */
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kfree_skb(tfp->skb);
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return NULL;
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}
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/* move free entry to end */
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tfp->skb = NULL;
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tfp->seqno = 0;
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list_move_tail(&tfp->list, head);
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memcpy(skb_put(skb, tmp_skb->len), tmp_skb->data, tmp_skb->len);
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kfree_skb(tmp_skb);
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memmove(skb->data + uni_diff, skb->data, hdr_len);
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unicast_packet = (struct unicast_packet *) skb_pull(skb, uni_diff);
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unicast_packet->packet_type = BAT_UNICAST;
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return skb;
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}
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static void frag_create_entry(struct list_head *head, struct sk_buff *skb)
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{
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struct frag_packet_list_entry *tfp;
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struct unicast_frag_packet *up =
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(struct unicast_frag_packet *)skb->data;
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/* free and oldest packets stand at the end */
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tfp = list_entry((head)->prev, typeof(*tfp), list);
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kfree_skb(tfp->skb);
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tfp->seqno = ntohs(up->seqno);
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tfp->skb = skb;
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list_move(&tfp->list, head);
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return;
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}
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static int frag_create_buffer(struct list_head *head)
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{
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int i;
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struct frag_packet_list_entry *tfp;
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for (i = 0; i < FRAG_BUFFER_SIZE; i++) {
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tfp = kmalloc(sizeof(struct frag_packet_list_entry),
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GFP_ATOMIC);
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if (!tfp) {
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frag_list_free(head);
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return -ENOMEM;
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}
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tfp->skb = NULL;
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tfp->seqno = 0;
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INIT_LIST_HEAD(&tfp->list);
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list_add(&tfp->list, head);
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}
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return 0;
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}
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static struct frag_packet_list_entry *frag_search_packet(struct list_head *head,
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struct unicast_frag_packet *up)
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{
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struct frag_packet_list_entry *tfp;
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struct unicast_frag_packet *tmp_up = NULL;
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uint16_t search_seqno;
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if (up->flags & UNI_FRAG_HEAD)
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search_seqno = ntohs(up->seqno)+1;
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else
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search_seqno = ntohs(up->seqno)-1;
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list_for_each_entry(tfp, head, list) {
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if (!tfp->skb)
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continue;
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if (tfp->seqno == ntohs(up->seqno))
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goto mov_tail;
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tmp_up = (struct unicast_frag_packet *)tfp->skb->data;
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if (tfp->seqno == search_seqno) {
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if ((tmp_up->flags & UNI_FRAG_HEAD) !=
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(up->flags & UNI_FRAG_HEAD))
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return tfp;
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else
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goto mov_tail;
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}
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}
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return NULL;
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mov_tail:
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list_move_tail(&tfp->list, head);
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return NULL;
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}
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void frag_list_free(struct list_head *head)
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{
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struct frag_packet_list_entry *pf, *tmp_pf;
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if (!list_empty(head)) {
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list_for_each_entry_safe(pf, tmp_pf, head, list) {
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kfree_skb(pf->skb);
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list_del(&pf->list);
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kfree(pf);
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}
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}
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return;
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}
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/* frag_reassemble_skb():
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* returns NET_RX_DROP if the operation failed - skb is left intact
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* returns NET_RX_SUCCESS if the fragment was buffered (skb_new will be NULL)
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* or the skb could be reassembled (skb_new will point to the new packet and
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* skb was freed)
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*/
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int frag_reassemble_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
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struct sk_buff **new_skb)
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{
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struct orig_node *orig_node;
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struct frag_packet_list_entry *tmp_frag_entry;
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int ret = NET_RX_DROP;
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struct unicast_frag_packet *unicast_packet =
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(struct unicast_frag_packet *)skb->data;
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*new_skb = NULL;
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spin_lock_bh(&bat_priv->orig_hash_lock);
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rcu_read_lock();
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orig_node = ((struct orig_node *)
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hash_find(bat_priv->orig_hash, compare_orig, choose_orig,
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unicast_packet->orig));
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rcu_read_unlock();
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if (!orig_node) {
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pr_debug("couldn't find originator in orig_hash\n");
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goto out;
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}
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orig_node->last_frag_packet = jiffies;
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if (list_empty(&orig_node->frag_list) &&
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frag_create_buffer(&orig_node->frag_list)) {
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pr_debug("couldn't create frag buffer\n");
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goto out;
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}
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tmp_frag_entry = frag_search_packet(&orig_node->frag_list,
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unicast_packet);
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if (!tmp_frag_entry) {
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frag_create_entry(&orig_node->frag_list, skb);
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ret = NET_RX_SUCCESS;
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goto out;
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}
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*new_skb = frag_merge_packet(&orig_node->frag_list, tmp_frag_entry,
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skb);
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/* if not, merge failed */
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if (*new_skb)
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ret = NET_RX_SUCCESS;
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out:
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spin_unlock_bh(&bat_priv->orig_hash_lock);
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return ret;
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}
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int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
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struct batman_if *batman_if, uint8_t dstaddr[])
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{
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struct unicast_packet tmp_uc, *unicast_packet;
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struct sk_buff *frag_skb;
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struct unicast_frag_packet *frag1, *frag2;
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int uc_hdr_len = sizeof(struct unicast_packet);
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int ucf_hdr_len = sizeof(struct unicast_frag_packet);
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int data_len = skb->len - uc_hdr_len;
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int large_tail = 0;
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uint16_t seqno;
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if (!bat_priv->primary_if)
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goto dropped;
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frag_skb = dev_alloc_skb(data_len - (data_len / 2) + ucf_hdr_len);
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if (!frag_skb)
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goto dropped;
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skb_reserve(frag_skb, ucf_hdr_len);
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unicast_packet = (struct unicast_packet *) skb->data;
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memcpy(&tmp_uc, unicast_packet, uc_hdr_len);
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skb_split(skb, frag_skb, data_len / 2 + uc_hdr_len);
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if (my_skb_head_push(skb, ucf_hdr_len - uc_hdr_len) < 0 ||
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my_skb_head_push(frag_skb, ucf_hdr_len) < 0)
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goto drop_frag;
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frag1 = (struct unicast_frag_packet *)skb->data;
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frag2 = (struct unicast_frag_packet *)frag_skb->data;
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memcpy(frag1, &tmp_uc, sizeof(struct unicast_packet));
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frag1->ttl--;
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frag1->version = COMPAT_VERSION;
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frag1->packet_type = BAT_UNICAST_FRAG;
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memcpy(frag1->orig, bat_priv->primary_if->net_dev->dev_addr, ETH_ALEN);
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memcpy(frag2, frag1, sizeof(struct unicast_frag_packet));
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if (data_len & 1)
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large_tail = UNI_FRAG_LARGETAIL;
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frag1->flags = UNI_FRAG_HEAD | large_tail;
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frag2->flags = large_tail;
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seqno = atomic_add_return(2, &batman_if->frag_seqno);
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frag1->seqno = htons(seqno - 1);
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frag2->seqno = htons(seqno);
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send_skb_packet(skb, batman_if, dstaddr);
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send_skb_packet(frag_skb, batman_if, dstaddr);
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return NET_RX_SUCCESS;
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drop_frag:
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kfree_skb(frag_skb);
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dropped:
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kfree_skb(skb);
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return NET_RX_DROP;
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}
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int unicast_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv)
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{
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struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
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struct unicast_packet *unicast_packet;
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struct orig_node *orig_node = NULL;
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struct batman_if *batman_if;
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struct neigh_node *neigh_node;
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int data_len = skb->len;
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uint8_t dstaddr[6];
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int ret = 1;
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spin_lock_bh(&bat_priv->orig_hash_lock);
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/* get routing information */
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if (is_multicast_ether_addr(ethhdr->h_dest))
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orig_node = (struct orig_node *)gw_get_selected(bat_priv);
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if (orig_node) {
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kref_get(&orig_node->refcount);
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goto find_router;
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}
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/* check for hna host - increases orig_node refcount */
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orig_node = transtable_search(bat_priv, ethhdr->h_dest);
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find_router:
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/* find_router() increases neigh_nodes refcount if found. */
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neigh_node = find_router(bat_priv, orig_node, NULL);
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if (!neigh_node)
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goto unlock;
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if (neigh_node->if_incoming->if_status != IF_ACTIVE)
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goto unlock;
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if (my_skb_head_push(skb, sizeof(struct unicast_packet)) < 0)
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goto unlock;
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/* don't lock while sending the packets ... we therefore
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* copy the required data before sending */
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batman_if = neigh_node->if_incoming;
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memcpy(dstaddr, neigh_node->addr, ETH_ALEN);
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spin_unlock_bh(&bat_priv->orig_hash_lock);
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unicast_packet = (struct unicast_packet *)skb->data;
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unicast_packet->version = COMPAT_VERSION;
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/* batman packet type: unicast */
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unicast_packet->packet_type = BAT_UNICAST;
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/* set unicast ttl */
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unicast_packet->ttl = TTL;
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/* copy the destination for faster routing */
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memcpy(unicast_packet->dest, orig_node->orig, ETH_ALEN);
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if (atomic_read(&bat_priv->fragmentation) &&
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data_len + sizeof(struct unicast_packet) >
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batman_if->net_dev->mtu) {
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/* send frag skb decreases ttl */
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unicast_packet->ttl++;
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ret = frag_send_skb(skb, bat_priv, batman_if, dstaddr);
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goto out;
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}
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send_skb_packet(skb, batman_if, dstaddr);
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ret = 0;
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goto out;
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unlock:
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spin_unlock_bh(&bat_priv->orig_hash_lock);
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out:
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if (neigh_node)
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neigh_node_free_ref(neigh_node);
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if (orig_node)
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kref_put(&orig_node->refcount, orig_node_free_ref);
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if (ret == 1)
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kfree_skb(skb);
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return ret;
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}
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