linux-kernel - Re: [PATCH v2 net-next] net/tls: allow MSG_CMSG

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Message-ID: <20200806114657.42f1ce8c@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 6 Aug 2020 11:46:57 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Rouven Czerwinski <r.czerwinski@...gutronix.de>
Cc:     Boris Pismenny <borisp@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>, kernel@...gutronix.de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next] net/tls: allow MSG_CMSG_COMPAT in sendmsg

On Thu,  6 Aug 2020 08:49:06 +0200 Rouven Czerwinski wrote:
> Trying to use ktls on a system with 32-bit userspace and 64-bit kernel
> results in a EOPNOTSUPP message during sendmsg:
> 
>   setsockopt(3, SOL_TLS, TLS_TX, …, 40) = 0
>   sendmsg(3, …, msg_flags=0}, 0) = -1 EOPNOTSUPP (Operation not supported)
> 
> The tls_sw implementation does strict flag checking and does not allow
> the MSG_CMSG_COMPAT flag, which is set if the message comes in through
> the compat syscall.
> 
> This patch adds MSG_CMSG_COMPAT to the flag check to allow the usage of
> the TLS SW implementation on systems using the compat syscall path.
> 
> Note that the same check is present in the sendmsg path for the TLS
> device implementation, however the flag hasn't been added there for lack
> of testing hardware.
> 
> Signed-off-by: Rouven Czerwinski <r.czerwinski@...gutronix.de>

I don't know much about the compat stuff, I trust our cmsg handling is
fine?

Just to be sure - did you run tools/testing/selftests/net/tls ?