linux-kernel - [PATCH net v2 2/2] bonding: 802.3ad: fix no transmission of LACPDUs

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Date:   Tue,  9 Aug 2022 22:33:22 -0400
From:   Jonathan Toppins <jtoppins@...hat.com>
To:     netdev@...r.kernel.org
Cc:     liuhangbin@...il.com, Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH net v2 2/2] bonding: 802.3ad: fix no transmission of LACPDUs

This is caused by the global variable ad_ticks_per_sec being zero as
demonstrated by the reproducer script discussed below. This causes
all timer values in __ad_timer_to_ticks to be zero, resulting
in the periodic timer to never fire.

To reproduce:
Run the script in
`tools/testing/selftests/drivers/net/bonding/bond-break-lacpdu-tx.sh` which
puts bonding into a state where it never transmits LACPDUs.

line 44: ip link add fbond type bond mode 4 miimon 200 \
            xmit_hash_policy 1 ad_actor_sys_prio 65535 lacp_rate fast
setting bond param: ad_actor_sys_prio
given:
    params.ad_actor_system = 0
call stack:
    bond_option_ad_actor_sys_prio()
    -> bond_3ad_update_ad_actor_settings()
       -> set ad.system.sys_priority = bond->params.ad_actor_sys_prio
       -> ad.system.sys_mac_addr = bond->dev->dev_addr; because
            params.ad_actor_system == 0
results:
     ad.system.sys_mac_addr = bond->dev->dev_addr

line 48: ip link set fbond address 52:54:00:3B:7C:A6
setting bond MAC addr
call stack:
    bond->dev->dev_addr = new_mac

line 52: ip link set fbond type bond ad_actor_sys_prio 65535
setting bond param: ad_actor_sys_prio
given:
    params.ad_actor_system = 0
call stack:
    bond_option_ad_actor_sys_prio()
    -> bond_3ad_update_ad_actor_settings()
       -> set ad.system.sys_priority = bond->params.ad_actor_sys_prio
       -> ad.system.sys_mac_addr = bond->dev->dev_addr; because
            params.ad_actor_system == 0
results:
     ad.system.sys_mac_addr = bond->dev->dev_addr

line 60: ip link set veth1-bond down master fbond
given:
    params.ad_actor_system = 0
    params.mode = BOND_MODE_8023AD
    ad.system.sys_mac_addr == bond->dev->dev_addr
call stack:
    bond_enslave
    -> bond_3ad_initialize(); because first slave
       -> if ad.system.sys_mac_addr != bond->dev->dev_addr
          return
results:
     Nothing is run in bond_3ad_initialize() because dev_add equals
     sys_mac_addr leaving the global ad_ticks_per_sec zero as it is
     never initialized anywhere else.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jonathan Toppins <jtoppins@...hat.com>
---

Notes:
    v2:
     * split this fix from the reproducer

 drivers/net/bonding/bond_3ad.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index d7fb33c078e8..957d30db6f95 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -84,7 +84,8 @@ enum ad_link_speed_type {
 static const u8 null_mac_addr[ETH_ALEN + 2] __long_aligned = {
 	0, 0, 0, 0, 0, 0
 };
-static u16 ad_ticks_per_sec;
+
+static u16 ad_ticks_per_sec = 1000 / AD_TIMER_INTERVAL;
 static const int ad_delta_in_ticks = (AD_TIMER_INTERVAL * HZ) / 1000;
 
 static const u8 lacpdu_mcast_addr[ETH_ALEN + 2] __long_aligned =
-- 
2.31.1