Re: [PATCH 1/1] bonding: crypto offload enabled, non-offload slave failover, rekey failed

[Hangbin Liu <hangbin.liu@linux.dev>]

On Fri, Sep 04, 2026 at 02:11:57PM +0800, Hangbin Liu wrote:
> On Thu, Sep 03, 2026 at 05:01:23PM -0500, David Dai wrote:
> > Create a bonding device (i.e. bond0) in active-backup mode, 2 slaves.
> > Active slave: offload capable interface (i.e. eth1), primary interface.
> > Backup slave: non-offload capable interface(i.e. eth2).
> > Configure strongswan service swantl.conf child SA "hw_offload = crypto"
> > Start strongswan service
> > IPSec Crytpo Offload is enabled on top of bond0. i.e. 
> > ip xfrm state |grep offload
> >         crypto offload parameters: dev bond0 dir out mode crypto
> > 	crypto offload parameters: dev bond0 dir in mode crypto
> > 
> > Active slave eth1 takes adavantage of IPSec Crypto Offload capability. 
> > 
> > If active slave eth1 is down for any reason (i.e. eth1 link down):
> > ip link set down dev eth1
> > non-offload capable interface eth2 failover to becomes active slave. 
> > The existing SAs can continue use software IPsec after failover.
> > Traffic still keeps going properly.
> > 
> > However if eth1 link had not recovered yet, strongswan service does
> > new child SA rekey, or uses swanctl command to do new child SA rekey, 
> > it will fail because active slave eth2 doesn't support crypto offload.
> > In bond_ipsec_add_sa routine, it returns -EINVAL now, which is 
> > treated as fatal error by xfrm_dev_state_add routine in kernel xfrm.
> > 
> > To make the non-offload active slave survive the child SA rekey, need 
> > to make bond_ipsec_add_sa routine returns -EOPNOTSUPP instead when 
> > active slave doesn't support IPsec Crypto offload, the xfrm will 
> > gracefully fallback to create new SA using Software IPsec. 
> > Network traffic can keep going.
> > 
> > After offload capable interface eth1 link is up, becomes active slave,
> > next time strongswan child SA rekey will create a new SA which enables
> > crypto offload again.
> > 
> > This way, network traffic is never interrupted, always keeps going.
> > 
> > Signed-off-by: David Dai <zdai@linux.ibm.com>
> > Tested-by: David Dai <zdai@linux.ibm.com>
> > ---
> >  drivers/net/bonding/bond_main.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> > index ef9eb0c53c66..79fc892dab07 100644
> > --- a/drivers/net/bonding/bond_main.c
> > +++ b/drivers/net/bonding/bond_main.c
> > @@ -490,7 +490,7 @@ static int bond_ipsec_add_sa(struct net_device *bond_dev,
> >  	    !real_dev->xfrmdev_ops->xdo_dev_state_add ||
> >  	    netif_is_bond_master(real_dev)) {
> >  		NL_SET_ERR_MSG_MOD(extack, "Slave does not support ipsec offload");
> > -		err = -EINVAL;
> > +		err = -EOPNOTSUPP;
> >  		goto out;
> >  	}
> >  
> > -- 
> > 2.55.0
> > 
> 
> The patch looks good to me. I am just not sure whether we should shorten
> the description. Let's wait for others' opinions.
> 

BTW, please add

Fixes: 18cb261afd7b ("bonding: support hardware encryption offload to slaves")

if there is a next version.