netdev - Re: [PATCH] Set DF bit for IPv4 GRE tunnels with fixed TTL

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Message-ID: <CALnjE+rSw8b5m6Z3nWr2QaHBu-rMM2Ly7Q27=9v3w6nnodtxQQ@mail.gmail.com>
Date:	Sat, 5 Dec 2015 13:48:42 -0800
From:	Pravin Shelar <pshelar@...ira.com>
To:	Konstantin Shemyak <konstantin@...myak.com>
Cc:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH] Set DF bit for IPv4 GRE tunnels with fixed TTL

On Sat, Dec 5, 2015 at 12:55 PM, Konstantin Shemyak
<konstantin@...myak.com> wrote:
> The DF bit on IPv4 GRE tunnels with fixed TTL is enforced in order
> to prevent networking loops. This was the original behavior of GRE
> tunnels, lost in the refactoring.
>
> Signed-off-by: Konstantin Shemyak <konstantin@...myak.com>
> ---
>  net/ipv4/ip_gre.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
> index 6145214..485bf27 100644
> --- a/net/ipv4/ip_gre.c
> +++ b/net/ipv4/ip_gre.c
> @@ -679,6 +679,10 @@ static int ipgre_tunnel_ioctl(struct net_device *dev,
>                     ((p.i_flags|p.o_flags)&(GRE_VERSION|GRE_ROUTING)))
>                         return -EINVAL;
>         }
> +
> +        if (p.iph.ttl)
> +                p.iph.frag_off |= htons(IP_DF);
> +

Same code already exist in ip_tunnel_ioctl() which is common function
for IP based tunnel modules. Why does that not work?


>         p.i_flags = gre_flags_to_tnl_flags(p.i_flags);
>         p.o_flags = gre_flags_to_tnl_flags(p.o_flags);
>
> --
> 1.9.1
>
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