linux-kernel - Re: [PATCH net 2/3] net: tls: Cancel RX async resync request on rdc

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Message-ID: <24a5c1af-f00f-4df0-b9f6-47dcb8d1947e@nvidia.com>
Date: Mon, 20 Oct 2025 11:02:08 +0300
From: Shahar Shitrit <shshitrit@...dia.com>
To: Sabrina Dubroca <sd@...asysnail.net>, Jakub Kicinski <kuba@...nel.org>
Cc: Tariq Toukan <tariqt@...dia.com>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Saeed Mahameed <saeedm@...dia.com>,
 Leon Romanovsky <leon@...nel.org>, Mark Bloch <mbloch@...dia.com>,
 John Fastabend <john.fastabend@...il.com>, netdev@...r.kernel.org,
 linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
 Gal Pressman <gal@...dia.com>, Boris Pismenny <borisp@...dia.com>
Subject: Re: [PATCH net 2/3] net: tls: Cancel RX async resync request on
 rdc_delta overflow



On 23/09/2025 22:16, Sabrina Dubroca wrote:
> 2025-09-22, 10:16:21 +0300, Shahar Shitrit wrote:
>>
>>
>> On 12/09/2025 18:14, Sabrina Dubroca wrote:
>>> 2025-09-10, 09:47:40 +0300, Tariq Toukan wrote:
>>>> From: Shahar Shitrit <shshitrit@...dia.com>
>>>>
>>>> When a netdev issues an RX async resync request, the TLS module
>>>> increments rcd_delta for each new record that arrives. This tracks
>>>> how far the current record is from the point where synchronization
>>>> was lost.
>>>>
>>>> When rcd_delta reaches its threshold, it indicates that the device
>>>> response is either excessively delayed or unlikely to arrive at all
>>>> (at that point, tcp_sn may have wrapped around, so a match would no
>>>> longer be valid anyway).
>>>>
>>>> Previous patch introduced tls_offload_rx_resync_async_request_cancel()
>>>> to explicitly cancel resync requests when a device response failure
>>>> is detected.
>>>>
>>>> This patch adds a final safeguard: cancel the async resync request when
>>>> rcd_delta crosses its threshold, as reaching this point implies that
>>>> earlier cancellation did not occur.
>>>>
>>>> Signed-off-by: Shahar Shitrit <shshitrit@...dia.com>
>>>> Signed-off-by: Tariq Toukan <tariqt@...dia.com>
>>>> ---
>>>>  net/tls/tls_device.c | 5 ++++-
>>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
>>>> index f672a62a9a52..56c14f1647a4 100644
>>>> --- a/net/tls/tls_device.c
>>>> +++ b/net/tls/tls_device.c
>>>> @@ -721,8 +721,11 @@ tls_device_rx_resync_async(struct tls_offload_resync_async *resync_async,
>>>>  		/* shouldn't get to wraparound:
>>>>  		 * too long in async stage, something bad happened
>>>>  		 */
>>>> -		if (WARN_ON_ONCE(resync_async->rcd_delta == USHRT_MAX))
>>>> +		if (WARN_ON_ONCE(resync_async->rcd_delta == USHRT_MAX)) {
>>>
>>> Do we still need to WARN here? It's a condition that can actually
>>> happen (even if it's rare), and that the stack can handle, so maybe
>>> not?
>>>
>> You are right that now the stack handles this, but removing the WARN
>> without any alternative, will remove any indication that something went
>> wrong and will prevent us from improving by searching the error flow
>> where we didn't cancel the request before reaching here. We can maybe
>> replace the WARN with a counter. what do you think?
> 
> Do you use CONFIG_DEBUG_NET in your devel/test kernels? If so,
> DEBUG_NET_WARN_ONCE would be an option. Or is it more so that
> users/customers can report the problem (ie on production kernels
> without CONFIG_DEBUG_NET) - in that case, the counter would work
> better.
> But if you really think that this condition indicates a driver bug,
> maybe the WARN is still appropriate. Jakub, what do you think?
> 
> 
> BTW, I was also thinking that the documentation
> (Documentation/networking/tls-offload.rst) could maybe be improved a
> bit with a description of how async resync works and how the driver is
> expected to use the tls_offload_rx_resync_async_request_{start,end}
> (and now _cancel) helpers. The section on "Stream scan
> resynchronization" is pretty abstract.

> 
We will submit documentation enhancement in a separate patch to net-next.