netdev - [PATCH] bonding: check if clients MAC addr has changed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1277822481-25175-1-git-send-email-fleitner@redhat.com>
Date:	Tue, 29 Jun 2010 11:41:21 -0300
From:	Flavio Leitner <fleitner@...hat.com>
To:	bonding-devel@...ts.sourceforge.net,
	Jay Vosburgh <fubar@...ibm.com>, netdev@...r.kernel.org,
	Andy Gospodarek <gospo@...hat.com>
Cc:	Flavio Leitner <fleitner@...hat.com>
Subject: [PATCH] bonding: check if clients MAC addr has changed

When two systems using bonding devices in adaptive load
balancing (ALB) communicates with each other, an endless
ping-pong of ARP replies starts between these two systems.

What happens? In the ALB mode, bonding driver keeps track
of each client connected in a hash table, so it can do the
receive load balancing (RLB). This hash table is updated
when an ARP reply is received, then it scans for the client
entry, updates its MAC address and flag it to be announced
later. Therefore, two seconds later, the alb monitor runs
and send for each updated client entry two ARP replies
updating this specific client. The same process happens on
the receiving system, causing the endless ping-pong of arp
replies.

See more information including the relevant functions below:

   System 1                          System 2
    bond0                             bond0

   ping <system2>
    ARP request  --------->
                           <--------- ARP reply

+->rlb_arp_recv  <---------------------+   <--- loop begins
|  rlb_update_entry_from_arp           |
|  client_info->ntt = 1;               |
|  bond_info->rx_ntt = 1;              |
|                                      |
|         <communication succeed>      |
|                                      |
|  bond_alb_monitor                    |
|  rlb_update_rx_clients               |
|  rlb_update_client                   |
|  arp_create(ARPOP_REPLY)             |
|   send ARP reply -------------->     V
|   send ARP reply -------------->
|                               rlb_arp_recv
|                               rlb_update_entry_from_arp
|                               client_info->ntt = 1;
|                               bond_info->rx_ntt = 1;
|                           < snipped, same as in system 1>
+-------           <-------------- send ARP reply
                   <-------------- send ARP reply

Besides the unneeded networking traffic, this loop breaks
a cluster because a backup system can't take over the IP
address. There is always one system sending an ARP reply
poisoning the network.

This patch fixes the problem adding a check for the MAC
address before updating it. Thus, if the MAC address didn't
change, there is no need to update neither to announce it later.

Signed-off-by: Flavio Leitner <fleitner@...hat.com>
---
 drivers/net/bonding/bond_alb.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 40fdc41..67154bb 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -340,7 +340,8 @@ static void rlb_update_entry_from_arp(struct bonding *bond, struct arp_pkt *arp)

 	if ((client_info->assigned) &&
 	    (client_info->ip_src == arp->ip_dst) &&
-	    (client_info->ip_dst == arp->ip_src)) {
+	    (client_info->ip_dst == arp->ip_src) &&
+	    (memcmp(client_info->mac_dst, arp->mac_src, ETH_ALEN))) {
 		/* update the clients MAC address */
 		memcpy(client_info->mac_dst, arp->mac_src, ETH_ALEN);
 		client_info->ntt = 1;
-- 
1.7.0.1

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html