How to specify the MTU of ocserv adapters

[David Woodhouse]

On Wed, 2016-05-11 at 09:23 +0200, Nikos Mavrogiannopoulos wrote:
> On Tue, May 10, 2016 at 7:53 PM, Yick Xie <yick.xie at gmail.com> wrote:
> > Hello,
> > As the title indicated, ocserv just dynamically and frequently adjust
> > the MTU value of virtual adapters according to peer-endings, which
> > sometimes even was set to 576. But actually the network is still
> > stable, only with certain kind of packet loss, yet totally acceptable.
> 
> That's a nice observation. I've reviewed the code, and as it is now,
> the MTU is being lowered when the kernel thinks that the MTU is too
> big (typically when some router sends an ICMP notification for that).
> However there is only logic to account lowering the MTU, but not
> raising it when the user's connection is no longer bounded. That is
> most likely you see clients (probably on mobile networks) drop to 576
> and never increase their MTU.

Note also that when it goes below 1280 you lose IPv6 connectivity. If
you really have got an MTU that low on a tunnel with IPv6 configured,
then perhaps we should either give up and *allow* fragmentation (over a
Legacy IP network), or fall back to sending (the larger frames?) over
the TCP connection?

-- 
dwmw2

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/x-pkcs7-signature
Size: 5760 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/openconnect-devel/attachments/20160511/12d0fac1/attachment.bin>