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IPv4 specific issue with USB tethering between my Debian laptop and my phone

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  IPv4 specific issue with USB tethering between my Debian laptop and  my phone Vincent Lefevre <vincent@vinc17.net> - 2021-12-15 01:20 +0100
    Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Dan Ritter <dsr@randomstring.org> - 2021-12-15 01:40 +0100
      Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Tim Woodall <debianuser@woodall.me.uk> - 2021-12-15 07:10 +0100
        Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Vincent Lefevre <vincent@vinc17.net> - 2021-12-15 18:00 +0100
          Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Tim Woodall <debianuser@woodall.me.uk> - 2021-12-15 18:10 +0100
            Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Vincent Lefevre <vincent@vinc17.net> - 2021-12-16 23:50 +0100
          Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Dan Ritter <dsr@randomstring.org> - 2021-12-15 19:40 +0100
            Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Vincent Lefevre <vincent@vinc17.net> - 2021-12-17 01:10 +0100
              Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Tim Woodall <debianuser@woodall.me.uk> - 2021-12-17 08:20 +0100
                Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Vincent Lefevre <vincent@vinc17.net> - 2021-12-19 00:00 +0100
                  Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone didier gaumet <didier.gaumet@gmail.com> - 2021-12-19 09:10 +0100
                    Re: IPv4 specific issue with USB tethering between my Debian laptop  and my phone Tim Woodall <debianuser@woodall.me.uk> - 2021-12-19 10:20 +0100

#243122 — IPv4 specific issue with USB tethering between my Debian laptop and my phone

Hi,

When I use USB tethering between my Debian/unstable laptop and my
Samsung Galaxy Note10+ phone (Android 11), everything is OK with
IPv6 connections (e.g. "wget -6"), but IPv4 connections freeze
(e.g. "wget -4" or "ssh -4"). I can notice this in particular when
testing with the same remote server. For instance, with "wget -4",
a few dozens of KB are downloaded, then the connection is completely
frozen.

I don't have any issue with the mobile hotspot (thus wifi between the
laptop and the phone) or with a Cosmo under Android 9 (instead of the
Samsung Galaxy Note10+), but in both cases, this is much slower, and
I sometimes get wifi disconnections.

On my Debian laptop, I'm using NetworkManager (nmcli).

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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#243123 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

Vincent Lefevre wrote: 
> Hi,
> 
> When I use USB tethering between my Debian/unstable laptop and my
> Samsung Galaxy Note10+ phone (Android 11), everything is OK with
> IPv6 connections (e.g. "wget -6"), but IPv4 connections freeze
> (e.g. "wget -4" or "ssh -4"). I can notice this in particular when
> testing with the same remote server. For instance, with "wget -4",
> a few dozens of KB are downloaded, then the connection is completely
> frozen.
> 
> I don't have any issue with the mobile hotspot (thus wifi between the
> laptop and the phone) or with a Cosmo under Android 9 (instead of the
> Samsung Galaxy Note10+), but in both cases, this is much slower, and
> I sometimes get wifi disconnections.
> 
> On my Debian laptop, I'm using NetworkManager (nmcli).

Have you investigated the MTU? This sounds like a mismatch
between what your laptop and phone are using.

Diagnosis (besides looking at connection details on both sides):
ping with increasingly large packet sizes. If it works at small
IPv4 packet sizes and then stops, that's the problem.

-dsr-

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#243128 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

On Tue, 14 Dec 2021, Dan Ritter wrote:

> Vincent Lefevre wrote:
>> Hi,
>>
>> When I use USB tethering between my Debian/unstable laptop and my
>> Samsung Galaxy Note10+ phone (Android 11), everything is OK with
>> IPv6 connections (e.g. "wget -6"), but IPv4 connections freeze
>> (e.g. "wget -4" or "ssh -4"). I can notice this in particular when
>> testing with the same remote server. For instance, with "wget -4",
>> a few dozens of KB are downloaded, then the connection is completely
>> frozen.
>>
>> I don't have any issue with the mobile hotspot (thus wifi between the
>> laptop and the phone) or with a Cosmo under Android 9 (instead of the
>> Samsung Galaxy Note10+), but in both cases, this is much slower, and
>> I sometimes get wifi disconnections.
>>
>> On my Debian laptop, I'm using NetworkManager (nmcli).
>
> Have you investigated the MTU? This sounds like a mismatch
> between what your laptop and phone are using.
>
> Diagnosis (besides looking at connection details on both sides):
> ping with increasingly large packet sizes. If it works at small
> IPv4 packet sizes and then stops, that's the problem.
>

Yes, probably - --clamp-mss-to-ptmu in iptables might be what is needed.

The other thing I thought of was dodgy natting somewhere. Especially if
there's a firewall somewhere that drops 'middle of stream' packets where
no SYN has been seen first.

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#243143 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

On 2021-12-15 06:09:12 +0000, Tim Woodall wrote:
> On Tue, 14 Dec 2021, Dan Ritter wrote:
> 
> > Vincent Lefevre wrote:
> > > Hi,
> > > 
> > > When I use USB tethering between my Debian/unstable laptop and my
> > > Samsung Galaxy Note10+ phone (Android 11), everything is OK with
> > > IPv6 connections (e.g. "wget -6"), but IPv4 connections freeze
> > > (e.g. "wget -4" or "ssh -4"). I can notice this in particular when
> > > testing with the same remote server. For instance, with "wget -4",
> > > a few dozens of KB are downloaded, then the connection is completely
> > > frozen.
> > > 
> > > I don't have any issue with the mobile hotspot (thus wifi between the
> > > laptop and the phone) or with a Cosmo under Android 9 (instead of the
> > > Samsung Galaxy Note10+), but in both cases, this is much slower, and
> > > I sometimes get wifi disconnections.
> > > 
> > > On my Debian laptop, I'm using NetworkManager (nmcli).
> > 
> > Have you investigated the MTU? This sounds like a mismatch
> > between what your laptop and phone are using.
> > 
> > Diagnosis (besides looking at connection details on both sides):
> > ping with increasingly large packet sizes. If it works at small
> > IPv4 packet sizes and then stops, that's the problem.

Indeed, this works up to
  ping -4 -s 1472 joooj.vinc17.net
  ping -6 -s 1452 joooj.vinc17.net

> Yes, probably - --clamp-mss-to-ptmu in iptables might be what is needed.

Thanks, but taking the rules from

  https://tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.cookbook.mtu-mss.html

I've tried

  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

and

  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1024

and none of them have any effect. Or did I need something else?

Any other suggestion?

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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#243146 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

On Wed, 15 Dec 2021, Vincent Lefevre wrote:

> On 2021-12-15 06:09:12 +0000, Tim Woodall wrote:
>> On Tue, 14 Dec 2021, Dan Ritter wrote:
>>
>>> Vincent Lefevre wrote:
>>>> Hi,
>>>>
>>>> When I use USB tethering between my Debian/unstable laptop and my
>>>> Samsung Galaxy Note10+ phone (Android 11), everything is OK with
>>>> IPv6 connections (e.g. "wget -6"), but IPv4 connections freeze
>>>> (e.g. "wget -4" or "ssh -4"). I can notice this in particular when
>>>> testing with the same remote server. For instance, with "wget -4",
>>>> a few dozens of KB are downloaded, then the connection is completely
>>>> frozen.
>>>>
>>>> I don't have any issue with the mobile hotspot (thus wifi between the
>>>> laptop and the phone) or with a Cosmo under Android 9 (instead of the
>>>> Samsung Galaxy Note10+), but in both cases, this is much slower, and
>>>> I sometimes get wifi disconnections.
>>>>
>>>> On my Debian laptop, I'm using NetworkManager (nmcli).
>>>
>>> Have you investigated the MTU? This sounds like a mismatch
>>> between what your laptop and phone are using.
>>>
>>> Diagnosis (besides looking at connection details on both sides):
>>> ping with increasingly large packet sizes. If it works at small
>>> IPv4 packet sizes and then stops, that's the problem.
>
> Indeed, this works up to
>  ping -4 -s 1472 joooj.vinc17.net
>  ping -6 -s 1452 joooj.vinc17.net
>
>> Yes, probably - --clamp-mss-to-ptmu in iptables might be what is needed.
>
> Thanks, but taking the rules from
>
>  https://tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.cookbook.mtu-mss.html
>
> I've tried
>
>  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
>
> and
>
>  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1024
>
I think you possibly want -A OUTPUT rules too. And also ip6tables rules.

When I look at where I've configured this in the past I've also done it
on the mangle chain:

iptables -t mangle -A FORWARD -p tcp -o $NET_IF --tcp-flags SYN,RST SYN
-j TCPMSS --clamp-mss-to-pmtu

ip6tables -t mangle -A FORWARD -p tcp -o $NETv6_IF --tcp-flags SYN,RST
SYN -j TCPMSS --clamp-mss-to-pmtu

etc. (you may or may not want to bother writing explicit rules for each
interface)

If you're going via a firewall then you (usually) only need -A FORWARD
But if you're trying to configure it on your laptop itself you probably
need -A OUTPUT (and possibly -A INPUT).

> and none of them have any effect. Or did I need something else?
>
> Any other suggestion?
>
>

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#243203 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

On 2021-12-15 17:01:54 +0000, Tim Woodall wrote:
> On Wed, 15 Dec 2021, Vincent Lefevre wrote:
> > I've tried
> > 
> >  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
> > 
> > and
> > 
> >  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1024
> > 
> I think you possibly want -A OUTPUT rules too.

This doesn't change anything.

> And also ip6tables rules.

There are no issues with IPv6.

> If you're going via a firewall then you (usually) only need -A FORWARD
> But if you're trying to configure it on your laptop itself you probably
> need -A OUTPUT (and possibly -A INPUT).

I can't use -A INPUT:

# iptables -A INPUT -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
iptables v1.8.7 (nf_tables):  RULE_APPEND failed (Invalid argument): rule in chain INPUT

And similar error with "-I INPUT":

iptables v1.8.7 (nf_tables):  RULE_INSERT failed (Invalid argument): rule in chain INPUT

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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#243148 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

Vincent Lefevre wrote: 
> On 2021-12-15 06:09:12 +0000, Tim Woodall wrote:
> > On Tue, 14 Dec 2021, Dan Ritter wrote:
> > 
> > > Vincent Lefevre wrote:
> > > > I don't have any issue with the mobile hotspot (thus wifi between the
> > > > laptop and the phone) or with a Cosmo under Android 9 (instead of the
> > > > Samsung Galaxy Note10+), but in both cases, this is much slower, and
> > > > I sometimes get wifi disconnections.
> > > > 
> > > > On my Debian laptop, I'm using NetworkManager (nmcli).
> > > 
> > > Have you investigated the MTU? This sounds like a mismatch
> > > between what your laptop and phone are using.
> > > 
> > > Diagnosis (besides looking at connection details on both sides):
> > > ping with increasingly large packet sizes. If it works at small
> > > IPv4 packet sizes and then stops, that's the problem.
> 
> Indeed, this works up to
>   ping -4 -s 1472 joooj.vinc17.net
>   ping -6 -s 1452 joooj.vinc17.net

ip link set USBNET0 mtu 1450, or something like that. I don't
know NetworkManager's syntax for that; random googling suggests
that they at least had a historical problem with not being able
to set MTU on anything other than a pure ethernet or wifi link,
but perhaps they've solved that?

-dsr-

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#243210 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

Dan Ritter wrote:
> ip link set USBNET0 mtu 1450, or something like that. I don't
> know NetworkManager's syntax for that; random googling suggests
> that they at least had a historical problem with not being able
> to set MTU on anything other than a pure ethernet or wifi link,
> but perhaps they've solved that?

"ip link" works on its side. I can see with wireshark that something
like "ip link set usb0 mtu 1300" is honored, but this doesn't solve
the problem (I've tried various values from 1000 to 1450).

Note that I could also see with wireshark that the iptables rules
with --clamp-mss-to-pmtu did not change the packet lengths.

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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#243216 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

On Fri, 17 Dec 2021, Vincent Lefevre wrote:

> Dan Ritter wrote:
>> ip link set USBNET0 mtu 1450, or something like that. I don't
>> know NetworkManager's syntax for that; random googling suggests
>> that they at least had a historical problem with not being able
>> to set MTU on anything other than a pure ethernet or wifi link,
>> but perhaps they've solved that?
>
> "ip link" works on its side. I can see with wireshark that something
> like "ip link set usb0 mtu 1300" is honored, but this doesn't solve
> the problem (I've tried various values from 1000 to 1450).
>
> Note that I could also see with wireshark that the iptables rules
> with --clamp-mss-to-pmtu did not change the packet lengths.
>

Does this happen on any connection or just some?

You said you could reproduce using ssh? Does that mean you can run
wireshark on both ends and see which packet is getting lost?

Did you try setting both mtu on the interface to something smallish plus
--clamp-mss-to-pmtu?


I'm pretty sure all ipv4 over mobile (which I think is what you are
testing) depends on NAT. So my other guess of a dodgy NAT device isn't
impossible. IIRC your ping tests suggested that ipv4 is being tunnelled
in ipv6

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#243249 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

On 2021-12-17 07:09:52 +0000, Tim Woodall wrote:
> On Fri, 17 Dec 2021, Vincent Lefevre wrote:
> 
> > Dan Ritter wrote:
> > > ip link set USBNET0 mtu 1450, or something like that. I don't
> > > know NetworkManager's syntax for that; random googling suggests
> > > that they at least had a historical problem with not being able
> > > to set MTU on anything other than a pure ethernet or wifi link,
> > > but perhaps they've solved that?
> > 
> > "ip link" works on its side. I can see with wireshark that something
> > like "ip link set usb0 mtu 1300" is honored, but this doesn't solve
> > the problem (I've tried various values from 1000 to 1450).
> > 
> > Note that I could also see with wireshark that the iptables rules
> > with --clamp-mss-to-pmtu did not change the packet lengths.
> > 
> 
> Does this happen on any connection or just some?

On any IPv4 connection (tested with ssh to 2 remote machines, and
with https on various web servers). IPv6 connections seem fine.

> You said you could reproduce using ssh? Does that mean you can run
> wireshark on both ends and see which packet is getting lost?

I haven't tried wireshark on the other end. I wonder whether there
is a replacement tool that doesn't need an X11 connection, to just
do the capture of the packets.

> Did you try setting both mtu on the interface to something smallish
> plus --clamp-mss-to-pmtu?

I've just tried, and this doesn't solve the problem.

> I'm pretty sure all ipv4 over mobile (which I think is what you are
> testing) depends on NAT. So my other guess of a dodgy NAT device isn't
> impossible. IIRC your ping tests suggested that ipv4 is being tunnelled
> in ipv6

Where would be the issue?

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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#243258 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

Le samedi 18 décembre 2021 à 23:52 +0100, Vincent Lefevre a écrit :
[...]
> I haven't tried wireshark on the other end. I wonder whether there
> is a replacement tool that doesn't need an X11 connection, to just
> do the capture of the packets.
[...]

Hello Vincent,

perhaps tshark (tshark package) would do?
https://www.wireshark.org/docs/wsug_html_chunked/AppToolstshark.html

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#243262 — Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

On Sun, 19 Dec 2021, didier gaumet wrote:

>
>
> Le samedi 18 d?cembre 2021 ? 23:52 +0100, Vincent Lefevre a ?crit?:
> [...]
>> I haven't tried wireshark on the other end. I wonder whether there
>> is a replacement tool that doesn't need an X11 connection, to just
>> do the capture of the packets.
> [...]
>
> Hello Vincent,
>
> perhaps tshark (tshark package) would do?
> https://www.wireshark.org/docs/wsug_html_chunked/AppToolstshark.html
>
>
>
>
Missed this.

tcpdump is my tool of choice for this. I don't even use wireshark for
capture when I'll be capturing packets on the host I'll be viewing them
on.

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