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batman-adv: forward late OGMs from best next hop
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When a packet is received from another node first and later from the
best next hop, this packet is dropped. However the first OGM was sent
with the BATADV_NOT_BEST_NEXT_HOP flag and thus dropped by neighbors.
The late OGM from the best neighbor is then dropped because it is a
duplicate.

If this situation happens constantly, a node might end up not forwarding
the "valid" OGMs anymore, and nodes behind will starve from not getting
valid OGMs.

Fix this by refining the duplicate checking behaviour: The actions
should depend on whether it was a duplicate for a neighbor only or for
the originator. OGMs which are not duplicates for a specific neighbor
will now be considered in batadv_iv_ogm_forward(), but only actually
forwarded for the best next hop. Therefore, late OGMs from the best
next hop are forwarded now and not dropped as duplicates anymore.

Signed-off-by: Simon Wunderlich <simon@open-mesh.com>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
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Simon Wunderlich authored and Antonio Quartulli committed Jun 10, 2013
1 parent ac16d14 commit 7c24bbb
Showing 1 changed file with 55 additions and 31 deletions.
86 changes: 55 additions & 31 deletions net/batman-adv/bat_iv_ogm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,21 @@
#include "bat_algo.h"
#include "network-coding.h"

/**
* batadv_dup_status - duplicate status
* @BATADV_NO_DUP: the packet is a duplicate
* @BATADV_ORIG_DUP: OGM is a duplicate in the originator (but not for the
* neighbor)
* @BATADV_NEIGH_DUP: OGM is a duplicate for the neighbor
* @BATADV_PROTECTED: originator is currently protected (after reboot)
*/
enum batadv_dup_status {
BATADV_NO_DUP = 0,
BATADV_ORIG_DUP,
BATADV_NEIGH_DUP,
BATADV_PROTECTED,
};

static struct batadv_neigh_node *
batadv_iv_ogm_neigh_new(struct batadv_hard_iface *hard_iface,
const uint8_t *neigh_addr,
Expand Down Expand Up @@ -650,7 +665,7 @@ batadv_iv_ogm_orig_update(struct batadv_priv *bat_priv,
const struct batadv_ogm_packet *batadv_ogm_packet,
struct batadv_hard_iface *if_incoming,
const unsigned char *tt_buff,
int is_duplicate)
enum batadv_dup_status dup_status)
{
struct batadv_neigh_node *neigh_node = NULL, *tmp_neigh_node = NULL;
struct batadv_neigh_node *router = NULL;
Expand All @@ -676,7 +691,7 @@ batadv_iv_ogm_orig_update(struct batadv_priv *bat_priv,
continue;
}

if (is_duplicate)
if (dup_status != BATADV_NO_DUP)
continue;

spin_lock_bh(&tmp_neigh_node->lq_update_lock);
Expand Down Expand Up @@ -718,7 +733,7 @@ batadv_iv_ogm_orig_update(struct batadv_priv *bat_priv,
neigh_node->tq_avg = batadv_ring_buffer_avg(neigh_node->tq_recv);
spin_unlock_bh(&neigh_node->lq_update_lock);

if (!is_duplicate) {
if (dup_status == BATADV_NO_DUP) {
orig_node->last_ttl = batadv_ogm_packet->header.ttl;
neigh_node->last_ttl = batadv_ogm_packet->header.ttl;
}
Expand Down Expand Up @@ -902,56 +917,65 @@ static int batadv_iv_ogm_calc_tq(struct batadv_orig_node *orig_node,
return ret;
}

/* processes a batman packet for all interfaces, adjusts the sequence number and
* finds out whether it is a duplicate.
* returns:
* 1 the packet is a duplicate
* 0 the packet has not yet been received
* -1 the packet is old and has been received while the seqno window
* was protected. Caller should drop it.
/**
* batadv_iv_ogm_update_seqnos - process a batman packet for all interfaces,
* adjust the sequence number and find out whether it is a duplicate
* @ethhdr: ethernet header of the packet
* @batadv_ogm_packet: OGM packet to be considered
* @if_incoming: interface on which the OGM packet was received
*
* Returns duplicate status as enum batadv_dup_status
*/
static int
static enum batadv_dup_status
batadv_iv_ogm_update_seqnos(const struct ethhdr *ethhdr,
const struct batadv_ogm_packet *batadv_ogm_packet,
const struct batadv_hard_iface *if_incoming)
{
struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
struct batadv_orig_node *orig_node;
struct batadv_neigh_node *tmp_neigh_node;
int is_duplicate = 0;
int is_dup;
int32_t seq_diff;
int need_update = 0;
int set_mark, ret = -1;
int set_mark;
enum batadv_dup_status ret = BATADV_NO_DUP;
uint32_t seqno = ntohl(batadv_ogm_packet->seqno);
uint8_t *neigh_addr;
uint8_t packet_count;

orig_node = batadv_get_orig_node(bat_priv, batadv_ogm_packet->orig);
if (!orig_node)
return 0;
return BATADV_NO_DUP;

spin_lock_bh(&orig_node->ogm_cnt_lock);
seq_diff = seqno - orig_node->last_real_seqno;

/* signalize caller that the packet is to be dropped. */
if (!hlist_empty(&orig_node->neigh_list) &&
batadv_window_protected(bat_priv, seq_diff,
&orig_node->batman_seqno_reset))
&orig_node->batman_seqno_reset)) {
ret = BATADV_PROTECTED;
goto out;
}

rcu_read_lock();
hlist_for_each_entry_rcu(tmp_neigh_node,
&orig_node->neigh_list, list) {
is_duplicate |= batadv_test_bit(tmp_neigh_node->real_bits,
orig_node->last_real_seqno,
seqno);

neigh_addr = tmp_neigh_node->addr;
is_dup = batadv_test_bit(tmp_neigh_node->real_bits,
orig_node->last_real_seqno,
seqno);

if (batadv_compare_eth(neigh_addr, ethhdr->h_source) &&
tmp_neigh_node->if_incoming == if_incoming)
tmp_neigh_node->if_incoming == if_incoming) {
set_mark = 1;
else
if (is_dup)
ret = BATADV_NEIGH_DUP;
} else {
set_mark = 0;
if (is_dup && (ret != BATADV_NEIGH_DUP))
ret = BATADV_ORIG_DUP;
}

/* if the window moved, set the update flag. */
need_update |= batadv_bit_get_packet(bat_priv,
Expand All @@ -971,8 +995,6 @@ batadv_iv_ogm_update_seqnos(const struct ethhdr *ethhdr,
orig_node->last_real_seqno = seqno;
}

ret = is_duplicate;

out:
spin_unlock_bh(&orig_node->ogm_cnt_lock);
batadv_orig_node_free_ref(orig_node);
Expand All @@ -994,7 +1016,8 @@ static void batadv_iv_ogm_process(const struct ethhdr *ethhdr,
int is_broadcast = 0, is_bidirect;
bool is_single_hop_neigh = false;
bool is_from_best_next_hop = false;
int is_duplicate, sameseq, simlar_ttl;
int sameseq, similar_ttl;
enum batadv_dup_status dup_status;
uint32_t if_incoming_seqno;
uint8_t *prev_sender;

Expand Down Expand Up @@ -1138,10 +1161,10 @@ static void batadv_iv_ogm_process(const struct ethhdr *ethhdr,
if (!orig_node)
return;

is_duplicate = batadv_iv_ogm_update_seqnos(ethhdr, batadv_ogm_packet,
if_incoming);
dup_status = batadv_iv_ogm_update_seqnos(ethhdr, batadv_ogm_packet,
if_incoming);

if (is_duplicate == -1) {
if (dup_status == BATADV_PROTECTED) {
batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
"Drop packet: packet within seqno protection time (sender: %pM)\n",
ethhdr->h_source);
Expand Down Expand Up @@ -1211,11 +1234,12 @@ static void batadv_iv_ogm_process(const struct ethhdr *ethhdr,
* seqno and similar ttl as the non-duplicate
*/
sameseq = orig_node->last_real_seqno == ntohl(batadv_ogm_packet->seqno);
simlar_ttl = orig_node->last_ttl - 3 <= batadv_ogm_packet->header.ttl;
if (is_bidirect && (!is_duplicate || (sameseq && simlar_ttl)))
similar_ttl = orig_node->last_ttl - 3 <= batadv_ogm_packet->header.ttl;
if (is_bidirect && ((dup_status == BATADV_NO_DUP) ||
(sameseq && similar_ttl)))
batadv_iv_ogm_orig_update(bat_priv, orig_node, ethhdr,
batadv_ogm_packet, if_incoming,
tt_buff, is_duplicate);
tt_buff, dup_status);

/* is single hop (direct) neighbor */
if (is_single_hop_neigh) {
Expand All @@ -1236,7 +1260,7 @@ static void batadv_iv_ogm_process(const struct ethhdr *ethhdr,
goto out_neigh;
}

if (is_duplicate) {
if (dup_status == BATADV_NEIGH_DUP) {
batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
"Drop packet: duplicate packet received\n");
goto out_neigh;
Expand Down

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