From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: Simon Schneider <simon-schneider@gmx.net>
Cc: netdev@vger.kernel.org
Subject: Re: Re: IPv4 / IPv6 over IPv4 IPsec tunnel: setting the DF bit
Date: Thu, 30 Jan 2014 16:59:45 +0100 [thread overview]
Message-ID: <20140130155945.GF25336@order.stressinduktion.org> (raw)
In-Reply-To: <trinity-a9289159-8d0c-4ad1-8586-e8987e008643-1391095583899@3capp-gmx-bs16>
On Thu, Jan 30, 2014 at 04:26:24PM +0100, Simon Schneider wrote:
> Hi Hannes,
> thanks once again for the quick reply.
>
> Quickly checked the ip manpage. I'm clear about the case where pmtudisc is in effect (default) - the DF bit must be TRUE in this case, for PMTUD to work.
>
> Not sure what you meant by:
>
> "but DF bit should get copied from inner packet up to tunnel header in every
> case"
>
> Do you mean the nopmtudisc case?
Exactly. In nopmtudisc mode the flag is set based on the inner protocols df
bit, default cleared. In pmtudisc mode the DF-flag is always set.
> Also, IPv6 must be different then - there's no DF bit to be copied.
If packet cannot traverse a router frag_needed is returned, tunnel
endpoint relays the icmp info to the original sender and it should update
its pmtu. There is no way to fragment the packet mid-path.
Also IPv6 tunnel endpoint do not fragment the tunnel packets while
encapsulating.
ipsec mode tunnel is allowed to fragment the packets while encapsulation.
> Could you please clarify?
Hope I did. ;)
Greetings,
Hannes
next prev parent reply other threads:[~2014-01-30 15:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-30 12:25 IPv4 / IPv6 over IPv4 IPsec tunnel: setting the DF bit Simon Schneider
2014-01-30 14:21 ` Hannes Frederic Sowa
2014-01-30 15:26 ` Aw: " Simon Schneider
2014-01-30 15:59 ` Hannes Frederic Sowa [this message]
2014-01-31 8:27 ` Aw: " Simon Schneider
2014-01-31 15:01 ` Hannes Frederic Sowa
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