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 <[email protected]> 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<[email protected]> > > 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 <NET> > >> ip route add <NET> dev <ALIAS_DEV> src <SRC_IP> > >> > >> 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<[email protected]> 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 >
