linux-kernel - Re: [PATCH net v3 2/2] bonding: 802.3ad: fix no transmission of LACPDUs

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Date:   Tue, 16 Aug 2022 06:11:41 -0700
From:   Jay Vosburgh <jay.vosburgh@...onical.com>
To:     Jonathan Toppins <jtoppins@...hat.com>
cc:     netdev@...r.kernel.org, liuhangbin@...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: Re: [PATCH net v3 2/2] bonding: 802.3ad: fix no transmission of LACPDUs

Jonathan Toppins <jtoppins@...hat.com> wrote:

>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
>    v3:
>     * rebased to latest net/master
>
> 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;

	I still feel like this is kind of a hack, as it's not really
fixing bond_3ad_initialize to actually work (which is the real problem
as I understand it).  If it's ok to skip all that for this case, then
why do we ever need to call bond_3ad_initialize?

	-J

> static const u8 lacpdu_mcast_addr[ETH_ALEN + 2] __long_aligned =
>-- 
>2.31.1
>

---
	-Jay Vosburgh, jay.vosburgh@...onical.com