Route-Based Wireguard Site to Site

[Timmey22]

Hi,

i recently set up two opnsense 21.1.3 with wireguard site to site, the tunnel establishment works like a charm. Since i am currently just testing wireguard and already have a connection between those two sites, i use BGP for route exchange over all available paths.
I configured wireguard on both ends with "disable routes" enabled and 0.0.0.0/0 as allowed networks for the endpoint. Wireguard successfully establishes a tunnel, however via this tunnel both sites cannot reach each other (for example via ping) and also cannot establish a routing neighborship via this connection.
I configured both interfaces ip address on opnsense based on the wireguard configuration (in this case 172.31.32.1 & 2 /24). 
After studying the routing table, i noticed that the tunnel subnet was not installed at all and the ping to the remote tunnel ip was forwarded via the default route:

root@OPN-01:~ # netstat -rn4
Routing tables

Internet:
Destination        Gateway            Flags     Netif Expire
default            192.168.10.1       UGS         em0
10.54.112.0/24     10.54.112.1        UGS      ovpnc1
10.54.112.1        link#12            UH       ovpnc1
10.54.112.46       link#12            UHS         lo0
172.31.31.2        link#11            UH          lo1
172.31.31.2/32     127.0.0.1          UGSB        lo0
172.31.32.2        link#13            UH          wg0

root@OPN-01:~ # ping 172.31.32.1
PING 172.31.32.1 (172.31.32.1): 56 data bytes
92 bytes from 192.168.10.1: Redirect Host(New addr: 192.168.10.254)
Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst
4  5  00 0054 91d7   0 0000  3f  01 52f5 192.168.10.20  172.31.32.1

After adding the route to this tunnel subnet manually on both appliances, i could reach the remote tunnel ip via icmp and the BGP session was established:

root@OPN-01:~ # route add 172.31.32.0/24 -iface wg0
add net 172.31.32.0: gateway wg0

root@OPN-01:~ # ping 172.31.32.1
PING 172.31.32.1 (172.31.32.1): 56 data bytes
64 bytes from 172.31.32.1: icmp_seq=0 ttl=64 time=66.344 ms
64 bytes from 172.31.32.1: icmp_seq=1 ttl=64 time=39.939 ms
64 bytes from 172.31.32.1: icmp_seq=2 ttl=64 time=40.095 ms
^C
--- 172.31.32.1 ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 39.939/48.793/66.344/12.411 ms
root@OPN-01:~ # netstat -rn4
Routing tables

Internet:
Destination        Gateway            Flags     Netif Expire
default            192.168.10.1       UGS         em0
10.54.112.0/24     10.54.112.1        UGS      ovpnc1
10.54.112.1        link#12            UH       ovpnc1
10.54.112.46       link#12            UHS         lo0
10.255.10.0/24     172.31.32.1        UG1         wg0
10.255.11.0/24     172.31.32.1        UG1         wg0
10.255.255.24/30   172.31.32.1        UG1         wg0
10.255.255.26/32   172.31.32.1        UG1         wg0
10.255.255.28/30   172.31.32.1        UG1         wg0
100.64.100.0/30    172.31.32.1        UG1         wg0
100.64.255.0/30    172.31.32.1        UG1         wg0
100.64.255.4/30    172.31.32.1        UG1         wg0
100.64.255.8/30    172.31.32.1        UG1         wg0
100.64.255.12/30   172.31.32.1        UG1         wg0
100.65.100.0/30    link#3             U          vmx1
100.65.100.2       link#3             UHS         lo0
100.65.200.0/30    link#10            U      vmx1_vla
100.65.200.2       link#10            UHS         lo0
127.0.0.1          link#5             UH          lo0
172.31.31.2        link#11            UH          lo1
172.31.31.2/32     127.0.0.1          UGSB        lo0
172.31.32.0/24     wg0                US          wg0
172.31.32.2        link#13            UH          wg0
192.168.1.0/24     172.31.32.1        UG1         wg0
192.168.10.0/24    link#1             U           em0
192.168.10.20      link#1             UHS         lo0
192.168.11.0/24    172.31.32.1        UG1         wg0
192.168.20.0/24    link#9             U      vmx0_vla
192.168.20.253     link#9             UHS         lo0
192.168.21.0/24    172.31.32.1        UG1         wg0
192.168.30.0/24    link#8             U      vmx0_vla
192.168.30.253     link#8             UHS         lo0
192.168.79.0/24    172.31.32.1        UG1         wg0
192.168.80.0/24    172.31.32.1        UG1         wg0
192.168.81.0/27    172.31.32.1        UG1         wg0
192.168.81.0/24    172.31.32.1        UG1         wg0
192.168.90.0/24    172.31.32.1        UG1         wg0
192.168.168.0/24   172.31.32.1        UG1         wg0
192.168.169.0/24   172.31.32.1        UG1         wg0
192.168.170.0/24   172.31.32.1        UG1         wg0
192.168.222.1/32   172.31.32.1        UG1         wg0
192.168.222.128/25 172.31.32.1        UG1         wg0
192.168.255.0/30   172.31.32.1        UG1         wg0

Since i have not found any other topic regarding this problem i am curious if anyone has stumbled upon this problem too or if you are aware of this?

[mimugmail]

It can only work if you add the bgp peer as a gateway since you disable the adding of kernel routes, but after this it should be easy.

[Timmey22]

The BGP neighborship is established between the tunnel ips, so no eBGP multihop is used here. In comparison, for other ethernet networks with other BGP peers i do not need any gateway and still the whole network is listed in netstat.
I have defined a gateway with the BGP peer's address and used this in different rules and the interface configuration but have not seen any effect in the netstat -rn4 output so far.
A little hint would be much appreciated  ;)

Edit: I figured it out myself, did not display the advanced options in wireguard...