diff mbox series

[maint,v3] batman-adv: prevent TT request storms by not sending inconsistent TT TLVLs

Message ID 20180511162307.12255-1-mareklindner@neomailbox.ch (mailing list archive)
State Accepted, archived
Delegated to: Simon Wunderlich
Headers
Series [maint,v3] batman-adv: prevent TT request storms by not sending inconsistent TT TLVLs |

Commit Message

Marek Lindner May 11, 2018, 4:23 p.m. UTC 
  A translation table TVLV changset sent with an OGM consists
of a number of headers (one per VLAN) plus the changeset
itself (addition and/or deletion of entries).

The per-VLAN headers are used by OGM recipients for consistency
checks. Said consistency check might determine that a full
translation table request is needed to restore consistency. If
the TT sender adds per-VLAN headers of empty VLANs into the OGM,
recipients are led to believe to have reached an inconsistent
state and thus request a full table update. The full table does
not contain empty VLANs (due to missing entries) the cycle
restarts when the next OGM is issued.

Consequently, when the translation table TVLV headers are
composed, empty VLANs are to be excluded.

Fixes: 21a57f6e7a3b ("batman-adv: make the TT CRC logic VLAN specific")

Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
---

v3:
 * rebased on top of maint

v2:
 * moved changes into batadv_tt_prepare_tvlv_local_data()
 * updated 'fixes' commit id

 net/batman-adv/translation-table.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Comments

Sven Eckelmann May 11, 2018, 4:41 p.m. UTC | #1 
On Freitag, 11. Mai 2018 18:23:07 CEST Marek Lindner wrote:
> A translation table TVLV changset sent with an OGM consists
> of a number of headers (one per VLAN) plus the changeset
> itself (addition and/or deletion of entries).
> 
> The per-VLAN headers are used by OGM recipients for consistency
> checks. Said consistency check might determine that a full
> translation table request is needed to restore consistency. If
> the TT sender adds per-VLAN headers of empty VLANs into the OGM,
> recipients are led to believe to have reached an inconsistent
> state and thus request a full table update. The full table does
> not contain empty VLANs (due to missing entries) the cycle
> restarts when the next OGM is issued.
> 
> Consequently, when the translation table TVLV headers are
> composed, empty VLANs are to be excluded.
> 
> Fixes: 21a57f6e7a3b ("batman-adv: make the TT CRC logic VLAN specific")
> 
> Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
> ---
> 
> v3:
>  * rebased on top of maint
> 
> v2:
>  * moved changes into batadv_tt_prepare_tvlv_local_data()
>  * updated 'fixes' commit id


Added as e4687b4be274 [1]

Thanks,
	Sven


[1] https://git.open-mesh.org/batman-adv.git/commit/e4687b4be274da6180fc15b327419851fb681ec9
diff mbox series

Patch

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 23f9c212..39865513 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -931,15 +931,20 @@  batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	struct batadv_softif_vlan *vlan;
 	u16 num_vlan = 0;
-	u16 num_entries = 0;
+	u16 vlan_entries = 0;
+	u16 total_entries = 0;
 	u16 tvlv_len;
 	u8 *tt_change_ptr;
 	int change_offset;
 
 	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
 	hlist_for_each_entry_rcu(vlan, &bat_priv->softif_vlan_list, list) {
+		vlan_entries = atomic_read(&vlan->tt.num_entries);
+		if (vlan_entries < 1)
+			continue;
+
 		num_vlan++;
-		num_entries += atomic_read(&vlan->tt.num_entries);
+		total_entries += vlan_entries;
 	}
 
 	change_offset = sizeof(**tt_data);
@@ -947,7 +952,7 @@  batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 
 	/* if tt_len is negative, allocate the space needed by the full table */
 	if (*tt_len < 0)
-		*tt_len = batadv_tt_len(num_entries);
+		*tt_len = batadv_tt_len(total_entries);
 
 	tvlv_len = *tt_len;
 	tvlv_len += change_offset;
@@ -964,6 +969,10 @@  batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 
 	tt_vlan = (struct batadv_tvlv_tt_vlan_data *)(*tt_data + 1);
 	hlist_for_each_entry_rcu(vlan, &bat_priv->softif_vlan_list, list) {
+		vlan_entries = atomic_read(&vlan->tt.num_entries);
+		if (vlan_entries < 1)
+			continue;
+
 		tt_vlan->vid = htons(vlan->vid);
 		tt_vlan->crc = htonl(vlan->tt.crc);