From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net-next v13 3/7] sch_cake: Add optional ACK filter
Date: Mon, 21 May 2018 10:18:32 -0700
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 <152691985736.4083.3416150561524698541.stgit@alrua-kau>
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On 05/21/2018 09:24 AM, Toke Høiland-Jørgensen wrote:

> +		while (oplen_tmp >= 8) {
> +			u32 right_b = get_unaligned_be32(sack_tmp + 4);
> +			u32 left_b = get_unaligned_be32(sack_tmp);
> +
> +			if (left_b >= right_b)
> +				continue;
> +
> +			if (first)
> +				bytes_b += right_b - left_b;
> +
> +			if (left_b <= left_a && right_a <= right_b) {
> +				found = true;
> +				if (!first)
> +					break;
> +			}
> +			oplen_tmp -= 8;
> +			sack_tmp += 8;
> +		}
>

This is obviously incorrect.

Please take a look at TCP stack, and how it handles sequence wrapping with following macros :

after(), before()

Quite frankly O wonder how this was really tested.