From: Nico Schottelius <nico.schottelius@ungleich.ch>
To: Omkhar Arasaratnam <omkhar@gmail.com>
Cc: Nico Schottelius <nico.schottelius@ungleich.ch>,
WireGuard mailing list <wireguard@lists.zx2c4.com>
Subject: Re: Source IP incorrect on multi homed systems
Date: Sat, 18 Feb 2023 23:34:59 +0100 [thread overview]
Message-ID: <877cwed218.fsf@ungleich.ch> (raw)
In-Reply-To: <CAHx9msc1cNV80YU7HRmQ9gsjSEiVZ=pb31aYqfP62hy8DeuGZA@mail.gmail.com>
Hello Omkhar,
I tend to disagree. The problem is not the routing, but the selected
source address, which is independent of routing. To be more specific: as
there is BGP routing on all all interfaces, 147.78.195.254 is an
accepted IP address on any interface.
Best regards,
Nico
Omkhar Arasaratnam <omkhar@gmail.com> writes:
> This looks like an asymmetric routing issue from what you’re describing, not a wireguard issue.
>
> You may want to look into policy based routing to address it.
>
> On Sat, Feb 18, 2023 at 15:54 Nico Schottelius <nico.schottelius@ungleich.ch> wrote:
>
> Dear group,
>
> I was wondering how wireguard [Linux kernel] or wireguard-go [FreeBSD]
> are supposed to decide which IP address to use for replying?
>
> I have seen both on FreeBSD and Linux that wireguard seems to use the IP
> address of the outgoing interface, i.e. the one with the route returning
> to the sender. However in multi homed situations, this can be wrong,
> let's take this example:
>
> 19:57:24.607526 net1 In IP 194.5.220.43.60770 > 147.78.195.254.51820: UDP, length 148
> 19:57:24.608358 net2 Out IP 195.141.200.73.51820 > 194.5.220.43.60770: UDP, length 92
>
> The initiator sends from 194.5.220.43 to the receiver 147.78.195.254.
> Wireguard then replies with the source IP of 195.141.200.73 instead of
> 147.78.195.254.
>
> As the node is multi homed, the packet might leave through any of its
> uplinks and thus return with a random (unexpected) IP address and will
> not pass NAT rules on firewalls and finally be dropped. F.i. in above
> example the firewall drops the packet from 195.141.200.73, because there
> is no session entry for that.
>
> I have observed this behaviour both on Linux 6.1.11 as well as
> wireguard-go 0.0.20220316_8,1 on FreeBSD and in both cases the
> connection will break depending on which active interface is taken as
> exit.
>
> I would argue that wireguard should by default invert the IP
> addresses, i.e. switch dst=src, src=dst and then reply with that,
> instead of adapting an interface specific address, or is there a good
> reason for the current behaviour?
>
> Best regards,
>
> Nico
>
> --
> Sustainable and modern Infrastructures by ungleich.ch
--
Sustainable and modern Infrastructures by ungleich.ch
next prev parent reply other threads:[~2023-02-18 22:50 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-18 20:14 Nico Schottelius
[not found] ` <CAHx9msc1cNV80YU7HRmQ9gsjSEiVZ=pb31aYqfP62hy8DeuGZA@mail.gmail.com>
2023-02-18 22:34 ` Nico Schottelius [this message]
2023-02-19 0:45 ` Mike O'Connor
2023-02-19 8:01 ` Nico Schottelius
2023-02-19 9:19 ` Mikma
2023-02-19 12:04 ` Nico Schottelius
2023-02-19 12:10 ` Nico Schottelius
2023-02-19 18:59 ` Peter Linder
[not found] ` <2ed829aaed9fec59ac2a9b32c4ce0a9005b8d8b850be81c81a226791855fe4eb@mu.id>
2023-02-19 12:13 ` Nico Schottelius
2023-02-19 14:39 ` Christoph Loesch
2023-02-19 16:32 ` David Kerr
2023-02-19 16:54 ` Sebastian Hyrvall
2023-02-19 18:04 ` Janne Johansson
2023-02-19 18:08 ` Sebastian Hyrvall
2023-02-19 20:11 ` Nico Schottelius
2023-02-19 17:05 ` tlhackque
[not found] ` <CADGd2DoE6TCtCxxWL7JWyNW5+yy_Pe+9MNzHznbudMWLTXQreA@mail.gmail.com>
2023-02-19 18:30 ` Fwd: " John Lauro
2023-02-19 22:28 ` tlhackque
2023-02-20 0:58 ` Luiz Angelo Daros de Luca
2023-02-19 18:37 ` David Kerr
2023-02-19 18:52 ` tlhackque
2023-02-19 18:42 ` tlhackque
2023-02-19 20:18 ` Nico Schottelius
2023-02-19 20:42 ` Roman Mamedov
2023-02-19 21:19 ` Nico Schottelius
2023-02-19 22:06 ` tlhackque
2023-02-19 22:42 ` Src addr code review (Was: Source IP incorrect on multi homed systems) Daniel Gröber
2023-02-20 0:28 ` 曹煜
2023-02-20 10:40 ` Nico Schottelius
2023-02-20 11:21 ` 曹煜
2023-02-20 9:47 ` Nico Schottelius
2023-02-20 20:43 ` dxld
2023-02-19 21:39 ` Source IP incorrect on multi homed systems tlhackque
2023-02-19 20:02 ` Nico Schottelius
2023-02-20 11:09 Janne Johansson
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