I have an interface wg0, a WireGuard interface generated by a WireGuard client running on machineA which is connected to a server. Everything works as expected.
I route traffic from wg0 to eth3 - a LAN interface on machineA - using netfilter (iptables/ip6tables). Just about everything works as expected from machineB, a machine connected to eth3, minus connectivity to certain websites, for example duckduckgo.com.
From machineA I can do:
> wget https://duckduckgo.com
--2020-11-17 17:24:30-- https://duckduckgo.com/
Resolving duckduckgo.com (duckduckgo.com)... 52.142.124.215
Connecting to duckduckgo.com (duckduckgo.com)|52.142.124.215|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 5763 (5.6K) [text/html]
Saving to: ‘index.html’
But from machineB I get:
> wget https://duckduckgo.com
--2020-11-17 18:25:35-- https://duckduckgo.com/
Resolving duckduckgo.com (duckduckgo.com)... 52.142.124.215
Connecting to duckduckgo.com (duckduckgo.com)|52.142.124.215|:443... connected.
And nothing more. DNS doesn't seem to be the problem. The *filter policy in my netfilter has:
:OUTPUT ACCEPT [0:0]
So I don't think it's outbound traffic that's being stopped.
Another example is Jitsi - from machineA:
> wget https://meet.jit.si
--2020-11-17 17:39:49-- https://meet.jit.si/
Resolving meet.jit.si (meet.jit.si)... 2a05:d014:fc7:5402:5179:fc03:7ea9:eceb, 2a05:d014:fc7:5401:eb50:330e:f554:5477, 76.223.28.75, ...
Connecting to meet.jit.si (meet.jit.si)|2a05:d014:fc7:5402:5179:fc03:7ea9:eceb|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: ‘index.html’
index.html [ <=> ] 50.43K --.-KB/s in 0.04s
2020-11-17 17:39:49 (1.19 MB/s) - ‘index.html’ saved [51639]
And from machineB:
> wget https://meet.jit.si
--2020-11-17 18:40:07-- https://meet.jit.si/
Resolving meet.jit.si (meet.jit.si)... 13.248.156.98, 76.223.28.75, 2a05:d014:fc7:5401:eb50:330e:f554:5477, ...
Connecting to meet.jit.si (meet.jit.si)|13.248.156.98|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
index.html: Permission denied
Cannot write to ‘index.html’ (Success).
I don't understand why I should have 'Permission denied' on machineB.
I'm not looking for a definitive answer here, just help in identifying areas of research. Does anybody have any ideas on where else to look?