netdev - Re: [RFC 1/1] net/tls(TLS_SW): Handle -ENOSPC error return from device/AES-NI

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Date:   Thu, 8 Oct 2020 16:35:34 +1100
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     poojatrivedi@...il.com, linux-crypto@...r.kernel.org,
        mallesh537@...il.com, josh.tway@...ckpath.com,
        netdev@...r.kernel.org
Subject: Re: [RFC 1/1] net/tls(TLS_SW): Handle -ENOSPC error return from
 device/AES-NI

Jakub Kicinski <kuba@...nel.org> wrote:
>
> Why would the driver return EBUSY from an async API? What's the caller
> supposed to do with that?

The Crypto API offers two modes for callers to deal with congestion.
If the request can be safely dropped (e.g., IPsec) then ENOSPC will
be returned and should be dealt with accordingly.

If the request cannot be dropped then EBUSY is returned to indicate
congestion, and the caller must refrain from issuing any more
requests until the Crypto API signals that there is space for them.

The request flag CRYPTO_TFM_REQ_MAY_BACKLOG is used to indicate
which mode you wish to use.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt