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 <[email protected]> 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 <[email protected]> > 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
