netdev - Re: [PATCH] ipv4: Fix non-initialized TTL when CONFIG

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Date:	Mon, 23 May 2016 14:33:18 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ezequiel@...guardiasur.com.ar
Cc:	netdev@...r.kernel.org, kernel@...p.com, kuznet@....inr.ac.ru,
	jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net
Subject: Re: [PATCH] ipv4: Fix non-initialized TTL when CONFIG_SYSCTL=n

From: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Date: Fri, 20 May 2016 13:21:10 -0300

> Commit fa50d974d104 ("ipv4: Namespaceify ip_default_ttl sysctl knob")
> moves the default TTL assignment, and as side-effect IPv4 TTL now
> has a default value only if sysctl support is enabled (CONFIG_SYSCTL=y).
> 
> The sysctl_ip_default_ttl is fundamental for IP to work properly,
> as it provides the TTL to be used as default. The defautl TTL may be
> used in ip_selected_ttl, through the following flow:
> 
>   ip_select_ttl
>     ip4_dst_hoplimit
>       net->ipv4.sysctl_ip_default_ttl
> 
> This commit fixes the issue by assigning net->ipv4.sysctl_ip_default_ttl
> in net_init_net, called during ipv4's initialization.
> 
> Without this commit, a kernel built without sysctl support will send
> all IP packets with zero TTL (unless a TTL is explicitly set, e.g.
> with setsockopt).
> 
> Given a similar issue might appear on the other knobs that were
> namespaceify, this commit also moves them.
> 
> Fixes: fa50d974d104 ("ipv4: Namespaceify ip_default_ttl sysctl knob")
> Signed-off-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>

Applied and queued up for -stable, thanks.