On 23/11/2020 20:20, Jakub Kicinski wrote:

On Sun, 22 Nov 2020 14:48:04 +0200 Tariq Toukan wrote:

quoted

As I understand it, best if we can even generalize this to apply to all 
kinds of traffic: bond driver won't do the xmit itself anymore, it just 
picks an egress dev and returns it. The core infrastructure will call 
the xmit function for the egress dev.

I think you went way further than I was intending :) I was only
considering the control path. Leave the datapath unchanged.

AFAIK you're making 3 changes:
 - forwarding tls ops
 - pinning flows
 - handling features

Pinning of the TLS device to a leg of the bond looks like ~15LoC.
I think we can live with that.

It's the 150 LoC of forwarding TLS ops and duplicating dev selection
logic in bond_sk_hash_l34() that I'd rather avoid.

Handling features is probably fine, too, I haven't thought about that
much.

Sorry for jumping in late, but I'd like to present an argument in favor of the approach in the original patch-set, as it may have been overlooked.

The forwarding of TLS ops approach is very flexible, and it will enable support for per-SKB hashing in the future (high-availability): This will require taking ooo_okay into consideration and offloading the context to more than one NIC. But, I think its doable. Even though this approach requires more lines of code, it is already used by other offloads. For instance, XFRM offload in bond_main.c.

quoted

I like the idea, it can generalize code structures for all kinds of 
upper-devices and sockets, taking them into a common place in core, 
which reduces code duplications.

If we go only half the way, i.e. keep xmit logic in bond for 
non-TLS-offloaded traffic, then we have to let TLS module (and others in 
the future) act deferentially for different kinds of devs (upper/lower) 
which IMHO reduces generality.

How so? I was expecting TLS to just do something like:

	netdev = sk_get_xmit_dev_lowest(sk);

which would recursively call get_xmit_slave(CONST) until it reaches
a device which doesn't resolve further.

BTW is the flow pinning to bond legs actually a must-do? I don't know
much about bonding but wouldn't that mean that if the selected leg goes
down we'd lose connectivity, rather than falling back to SW crypto?

It is definitely not a must, and I think we should remove it in the future, once the use-case presents itself.

quoted

What if the egress dev is detached form the bond? We must then be 
notified somehow.

Do we notify TLS when routing changes? I think it's a separate topic. 

If we have the code to "un-offload" a flow we could handle clearing
features better and notify from sk_validate_xmit_skb that the flow
started hitting unexpected dev, hence it should be re-offloaded.

I don't think we need an explicit invalidation from the particular
drivers here.

Even though re-offload is not exercised, it is possible:
if packets are not using offload by the old netdev, then remove offload from it, and add offload to the new netdev.
A resync, will likely follow, after which offload continue on the new netdev.

The question is who identifies/decides when to re-offload. One option is that the bond driver will trigger it.