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Date:      Sun, 02 Jul 2017 18:57:54 +0200
From:      "Herbert J. Skuhra" <herbert@mailbox.org>
To:        Eugene Grosbein <eugen@grosbein.net>
Cc:        freebsd-net@FreeBSD.org
Subject:   Re: [Bug 220351] Path MTU discovery works only after resetting an internal interface MTU (mpd5, ng_nat, ipfw)
Message-ID:  <878tk6ydwt.wl-herbert@mailbox.org>
In-Reply-To: <59590FE6.7030109@grosbein.net>
References:  <bug-220351-2472@https.bugs.freebsd.org/bugzilla/> <bug-220351-2472-lCDWr8PCgb@https.bugs.freebsd.org/bugzilla/> <87r2xzaw30.wl-herbert@mailbox.org> <87bmp3x7eu.wl-herbert@mailbox.org> <59590064.1040700@grosbein.net> <87a84myitf.wl-herbert@mailbox.org> <59590FE6.7030109@grosbein.net>

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Eugene Grosbein skrev:
> =

> 02.07.2017 22:11, Herbert J. Skuhra =D0=C9=DB=C5=D4:
>> Eugene Grosbein skrev:
>>> =

>>> 02.07.2017 21:03, Herbert J. Skuhra wrote:
>>>> Skype for Business (S4B) on Mac OS X 10.12.6 (Beta5) is actually
>>>> trying to connect over IPv4. The connection fails until I lower MT=
U to
>>>> 1440. After resetting MTU to 1500 and restarting S4B it connects f=
ine
>>>> for a while ('route -n get' default shows 1500). I use 'set iface
>>>> enable tcpmssfix' in mpd5.conf and I've tried:
>>>> =

>>>> - set iface mtu and set link mtu/mru/mrru in mpd5.conf
>>>> - set scrub ... max-mss in pf.conf
>>> =

>>> Please show output of ifconfig command for external ng interface.
>> =

>> ng0: flags=3D88d1<UP,POINTOPOINT,RUNNING,NOARP,SIMPLEX,MULTICAST> me=
tric 0 mtu 1440
>> inet6 fe80::XXX:XXXX:XXXX:XXXX%ng0 prefixlen 64 scopeid 0x7 =

>> inet XX.XX.XX.XX --> XX.XX.XX.YY netmask 0xffffffff =

>> nd6 options=3D21<PERFORMNUD,AUTO_LINKLOCAL>
> =

> 'set iface enable tcpmssfix' in mpd.conf should be enough for you.
> =

> Are you sure you have it in right point of the config?
> This is critical for it to take effect. Please see mpd.conf.sample fo=
r example.
> =

> Doesn't mpd complain of this command to its log?

No.

> Make sure you have 'log +iface +iface2' command in your mpd.conf,
> restart mpd5 and scan its log for 'tcpmssfix'.

mpd: [B1] IFACE: Connecting tcpmssfix

But when I disable IPv6 on my network everything is working... even
without tcpmssfix enabled.

Instead of enabling ipv6cp in mpd5 I've also tested with an IPv6 tunnel=

from HE... same issue. :-(

--
Herbert



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