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Message-ID: <20250714164142.341e37a2@kernel.org>
Date: Mon, 14 Jul 2025 16:41:42 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
<horms@...nel.org>, kernel@...gutronix.de, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, Maxime Chevallier <maxime.chevallier@...tlin.com>
Subject: Re: [PATCH net-next v2 1/1] net: selftests: add PHY-loopback test
for bad TCP checksums
On Fri, 11 Jul 2025 09:24:49 +0200 Oleksij Rempel wrote:
> + /* To avoid sparse warnings about operating on
> + * restricted __sum16/__be16 types, explicitly cast the
> + * checksum to a plain u16, perform the manipulation,
> + * and then cast the result back.
> + */
> + csum = (__force u16)thdr->check;
> +
> + /* Mangle the checksum by flipping the LSB. */
> + csum ^= 1;
> + /* If mangling resulted in 0, use the raw value for a
> + * mangled-zero checksum. We use the literal 0xffff
> + * because CSUM_MANGLED_0 has a restricted type.
> + */
> + if (!csum)
> + csum = 0xffff;
> +
> + /* Cast the final integer value back to the restricted
> + * type
> + */
> + thdr->check = (__force __sum16)csum;
Way to manny lines of code for something this simple.
Can csum_add() help you get rid of all these casts and comments?
--
pw-bot: cr
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