netdev - Re: [PATCH net] ipv6: rpl: fix full address compression

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Message-Id: <20200418.150448.1291076574525454160.davem@davemloft.net>
Date:   Sat, 18 Apr 2020 15:04:48 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     alex.aring@...il.com
Cc:     kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org, kuba@...nel.org,
        mcr@...delman.ca, stefan@...enfreihafen.org, netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv6: rpl: fix full address compression

From: Alexander Aring <alex.aring@...il.com>
Date: Wed, 15 Apr 2020 09:06:53 -0400

> This patch makes it impossible that cmpri or cmpre values are set to the
> value 16 which is not possible, because these are 4 bit values. We
> currently run in an overflow when assigning the value 16 to it.
> 
> According to the standard a value of 16 can be interpreted as a full
> elided address which isn't possible to set as compression value. A reason
> why this cannot be set is that the current ipv6 header destination address
> should never show up inside the segments of the rpl header. In this case we
> run in a overflow and the address will have no compression at all. Means
> cmpri or compre is set to 0.
> 
> As we handle cmpri and cmpre sometimes as unsigned char or 4 bit value
> inside the rpl header the current behaviour ends in an invalid header
> format. This patch simple use the best compression method if we ever run
> into the case that the destination address is showed up inside the rpl
> segments. We avoid the overflow handling and the rpl header is still valid,
> even when we have the destination address inside the rpl segments.
> 
> Signed-off-by: Alexander Aring <alex.aring@...il.com>

Applied, thank you.