From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.zx2c4.com (lists.zx2c4.com [165.227.139.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 45AE5C61DA4 for ; Sun, 19 Feb 2023 18:39:55 +0000 (UTC) Received: by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 4a7e15f1; Sun, 19 Feb 2023 18:38:07 +0000 (UTC) Received: from mail-lf1-f53.google.com (mail-lf1-f53.google.com [209.85.167.53]) by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTPS id 6668cc51 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO) for ; Sun, 19 Feb 2023 18:38:04 +0000 (UTC) Received: by mail-lf1-f53.google.com with SMTP id c2so1290475lfp.6 for ; Sun, 19 Feb 2023 10:38:04 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=to:subject:message-id:date:from:in-reply-to:references:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=LB93YBVA5j2JQzH9KFzG2WCvP+JNgfjvNSZqsxBVcFY=; b=PWYp4hGq0vlWPVfI/XcKqAMZWTzDOvn4jvbGXX9dP5ss4EX9ZAUvG0N9T9QZCZhuiu KsXSaYvvpx/7xHibOjssXgOdKHEDpShtwSj7cWUrVNz3++8Vb9Lx7sevJ/VxTzUZWuLo OVf9N2k4WsOS2bOiQ+g/mlrn/xfn+6u07m0iHJyhAQf70eUmTSH4tvC3X7q3F24E+C+r vHCTRr+sTSZz1t3aQNp9iSshuYQwMJJ1HXeUSrr6wNfVUXlKIML22g35mwQXfCXNsoPC 0EQNgKjUSQTnWLMmOPgJsNsNQA0uIgEugYk94e0gDpanLs1egn6UhNYohXIsp3q11K0o fI8Q== X-Gm-Message-State: AO0yUKVluf8t7mSpbu/6qwoSgp0Oykq81f6BdjcvrIzbiCN5s7Rz+46J Ha2b2oxkHTLHiAP5XgMkCaSg3SkeNJ1N1/9JB7qj0bD/006ip2YiRwA= X-Google-Smtp-Source: AK7set/yr76Z9tDOSRpeoSikZuLd1WISiVQ1UFAgFKcAMKIiGu5dyhHPYcP1Eb/mu/9Yd5HwD/Ye8u+mXnQTIEFt9JI= X-Received: by 2002:ac2:43d5:0:b0:4d5:ca32:697f with SMTP id u21-20020ac243d5000000b004d5ca32697fmr642391lfl.9.1676831883447; Sun, 19 Feb 2023 10:38:03 -0800 (PST) MIME-Version: 1.0 References: <875yby83n2.fsf@ungleich.ch> <2ed829aaed9fec59ac2a9b32c4ce0a9005b8d8b850be81c81a226791855fe4eb@mu.id> <87ttzhc0jt.fsf@ungleich.ch> <7d7bc930-65d9-f13e-cedc-e0451407be85@chil.at> In-Reply-To: From: David Kerr Date: Sun, 19 Feb 2023 13:37:52 -0500 Message-ID: Subject: Re: Source IP incorrect on multi homed systems To: wireguard@lists.zx2c4.com Content-Type: text/plain; charset="UTF-8" X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" My proposed workaround specifically stated to match on both the interface and destination address, and to set a route with both interface and [source] address. This allows for multiple IP addresses on the same interface -- which you can do with both IPv4 and IPv6. But yes, it is a nasty hack. You really need to understand what is going on between the firewall and routing tables/rules and it is easy to get confused. On Sun, Feb 19, 2023 at 12:10 PM tlhackque wrote: > > FWIW, while clever, I don't think that iptables mark solves all cases. > E.g., consider an interface with multiple addresses, where a packet > comes in on a secondary address. The proposed rule would send it out > the right interface, but still with the wrong (primary) address picked > from the interface... > > With IPv6 it's common to assign an address to a service rather than a > host so services can move easily. So multiple addresses per interface > are the rule, not the exception. > > I do the same with IPv4 inside addresses, though these days public IPv4 > addresses are scarce enough that it's not common for public IPs. It > amounts to the same issue - the NAT tracking is stateful. > > Trying to work around this with routing seems like a maze of twisty > passages - so I agree that the right solution is for WG to respond from > the address that receives a packet. > > On 19-Feb-23 11:32, David Kerr wrote: > > Without getting into the debate of whether wireguard is acting > > correctly or not, I think there is a possible workaround. > > > > 1. In the iptables mangle table PREROUTING, match the incoming > > interface and destination address and --set-xmark a firewall MARK > > unique to this interface/destination > > 2. Create a new ip route table that sets the default route to go out > > on the interface with the source address you want (same as destination > > address in iptables) > > 3. Create a new ip rule that sends all packets with firewall mark set > > in iptables to the routing table you just created > > > > Repeat above for each interface/address you need to mangle, with a > > unique firewall mark and routing table for each. > > > > It may be necessary to use CONNMARK in PREROUTING and OUTPUT to > > --restore_mark. I can't remember if this is needed or not, its been a > > while since I configured iptables with this. > > > > This should ensure that any packet that comes into an > > interface/address is replied to from the same interface/address. > > > > David > > > > > > On Sun, Feb 19, 2023 at 9:44 AM Christoph Loesch wrote: > >> Hi, > >> > >> I don't think no one wants to fix it, there are several users having this issue. I rather guess no one could find a suitable solution to fix it. > >> > >> @Nico: did you try to delete the affected route and add it again with the correct source IP ? > >> > >> as I mentioned it inhttps://lists.zx2c4.com/pipermail/wireguard/2021-November/007324.html > >> > >> ip route del > >> ip route add dev src > >> > >> This way I was able to (at least temporary) fix this issue on multi homed systems. > >> > >> Kind regards, > >> Christoph > >> > >> Am 19.02.2023 um 13:13 schrieb Nico Schottelius: > >>> Hey Sebastian, > >>> > >>> Sebastian Hyrwall writes: > >>> > >>>> It is kinda. It's been mentioned multiple times over the years but no one seems to want to fix it. Atleast you should be able to specify bind/src ip in the > >>>> config. I gave up WG because of it. Wasn't accepted by my projects security policy since src ip could not be configured. > >>>> > >>>> There is an unofficial patch however, > >>>> > >>>> https://github.com/torvalds/linux/commit/5fa98082093344c86345f9f63305cae9d5f9f281 > >>> the binding is somewhat related to this issue and I was looking for that > >>> feature some time ago, too. While it is correlated and I would really > >>> appreciate binding support, I am not sure whether the linked patch does > >>> actually fix the problem I am seeing in multi homed devices. > >>> > >>> As long as wireguard does not reply with the same IP address it was > >>> contacted with, packets will get dropped on stateful firewalls, because > >>> the returning packet does not match the state session database. > >>> > >>> Best regards, > >>> > >>> Nico > >>> > >>> -- > >>> Sustainable and modern Infrastructures by ungleich.ch >