Re: [PATCH net V2 2/3] net: tls: Cancel RX async resync request on rdc_delta overflow

[Sabrina Dubroca <sd@queasysnail.net>]

2025-10-22, 14:38:17 +0300, Shahar Shitrit wrote:
> 
> 
> On 21/10/2025 18:28, Sabrina Dubroca wrote:
> > nit if you end up respinning, there's a typo in the subject:
> > s/rdc_delta/rcd_delta/
> > 
> > 
> > 2025-10-20, 10:05:53 +0300, Tariq Toukan wrote:
> >> From: Shahar Shitrit <shshitrit@nvidia.com>
> >>
> >> When a netdev issues a RX async resync request for a TLS connection,
> >> the TLS module handles it by logging record headers and attempting to
> >> match them to the tcp_sn provided by the device. If a match is found,
> >> the TLS module approves the tcp_sn for resynchronization.
> >>
> >> While waiting for a device response, the TLS module also increments
> >> rcd_delta each time a new TLS record is received, tracking the distance
> >> from the original resync request.
> >>
> >> However, if the device response is delayed or fails (e.g due to
> >> unstable connection and device getting out of tracking, hardware
> >> errors, resource exhaustion etc.), the TLS module keeps logging and
> >> incrementing, which can lead to a WARN() when rcd_delta exceeds the
> >> threshold.
> >>
> >> To address this, introduce tls_offload_rx_resync_async_request_cancel()
> >> to explicitly cancel resync requests when a device response failure is
> >> detected. Call this helper also as a final safeguard when rcd_delta
> >> crosses its threshold, as reaching this point implies that earlier
> >> cancellation did not occur.
> >>
> >> Fixes: 138559b9f99d ("net/tls: Fix wrong record sn in async mode of device resync")
> > 
> > The patch itself looks good, but what issue is fixed within this
> > patch? The helper will be useful in the next patch, but right now
> > we're only resetting the resync_async status. The only change I see
> > (without patch 3) is that we won't call tls_device_rx_resync_async()
> > next time we decrypt a record in SW, but it wouldn't have done
> > anything.
> > 
> > Actually, also in patch 1/3, there is no "fix" is in that patch.
> > 
> 
> I agree about patch 1/3 so I'll remove the fixes tag.
> 
> For this patch, indeed at this point the WARN() was already fired,
> however, the bug being addressed is the unnecessary work the TLS module
> continues to do. For my liking, the wasted CPU cycles and resources
> alone justify the fix, even if we've already issued a warning.
> What do you think?

Is there any work being done/avoided other than calling
tls_device_rx_resync_async and returning immediately?

With or without the patch, tls_device_rx_resync_new_rec will be called
during stream parsing.

Currently, resync_async->req doesn't get reset so we'll call
tls_device_rx_resync_async. We're still in async phase, rcd_delta is
still USHRT_MAX, and we're done, tls_device_rx_resync_new_rec returns.

With the patch, we'll see that resync_async->req is 0 and avoid
calling tls_device_rx_resync_async.

Did I miss something else?

-- 
Sabrina