netdev - Re: [net-next PATCH] net: ipv6: restrict hop_limit sysctl setting to range [1;255]

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Message-Id: <20151203.144237.978887160176558314.davem@davemloft.net>
Date:	Thu, 03 Dec 2015 14:42:37 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	phil@....cc
Cc:	netdev@...r.kernel.org
Subject: Re: [net-next PATCH] net: ipv6: restrict hop_limit sysctl setting
 to range [1;255]

From: Phil Sutter <phil@....cc>
Date: Tue,  1 Dec 2015 22:45:15 +0100

> Setting a value bigger than 255 resulted in using only the lower eight
> bits of that value as it is assigned to the u8 header field. To avoid
> this unexpected result, reject such values.
> 
> Setting a value of zero is technically possible, but hosts receiving
> such a packet have to treat it like hop_limit was set to one, according
> to RFC2460. Therefore I don't see a use-case for that.
> 
> Setting a route's hop_limit to zero in iproute2 means to use the sysctl
> default, which is not the case here: Setting e.g.
> net.conf.eth0.hop_limit=0 will not make the kernel use
> net.conf.all.hop_limit for outgoing packets on eth0. To avoid these
> kinds of confusion, reject zero.
> 
> Signed-off-by: Phil Sutter <phil@....cc>

Applied, thanks Phil.
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