Ok, Well even if using another local IP in range 127.0.0.0/8 we can’t be certain we will clash with something else.

How about adding a directive for the remote interface address in wg.conf? Like this:

# cat /usr/local/etc/wireguard/wg0.conf
[Interface]
PrivateKey = <->
ListenPort = 7777
Address = 192.168.2.1/32
RemoteAddress = 192.168.2.2

[Peer]
PublicKey = <->
AllowedIPs = 192.168.2.0/24
Endpoint = 172.16.0.23:7777

# diff /usr/local/bin/wg-quick.org ./wg-quick
17a18
> REMOTE_ADDRESS=""
86a88
> RemoteAddress) REMOTEADDRESS="$value"; continue ;;
175c177,181
< cmd ifconfig "$INTERFACE" inet "$1" "${1%%/*}" alias
---
>     if [[ -n $REMOTEADDRESS ]]; then
> cmd ifconfig "$INTERFACE" inet "$1" "$REMOTEADDRESS" alias
>     else
>                 cmd ifconfig "$INTERFACE" inet "$1" "${1%%/*}" alias
>     fi

/Peter


23 feb. 2020 kl. 12:37 skrev Jason A. Donenfeld <Jason@zx2c4.com>:

We tried this already and it didn't work. See the below commit.
Perhaps you can update that bug report you filed?

commit 2c6cabd73dfb23990c245250ef2e502bdb33d189
Author: Jason A. Donenfeld <Jason@zx2c4.com>
Date:   Thu Feb 28 19:03:11 2019 +0100

  wg-quick: freebsd: rebreak interface loopback, while fixing localhost

  The commit 7c833642 ("wg-quick: freebsd: allow loopback to work") was
  supposed to make things better, but actually it just started sending
  legitimate localhost traffic over the WireGuard interface, which is
  really quite bad.

  This reverts commit 7c833642dfa342218602ab18e7091e86408d2982.

  Reported-by: Matt Smith <matt.xtaz@gmail.com>
  Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/wg-quick/freebsd.bash b/src/wg-quick/freebsd.bash
index 93f1a3b7..e83dbef0 100755
--- a/src/wg-quick/freebsd.bash
+++ b/src/wg-quick/freebsd.bash
@@ -158,7 +158,7 @@ add_addr() {
      if [[ $1 == *:* ]]; then
              cmd ifconfig "$INTERFACE" inet6 "$1" alias
      else
-               cmd ifconfig "$INTERFACE" inet "$1" 127.0.0.1 alias
+               cmd ifconfig "$INTERFACE" inet "$1" "${1%%/*}" alias
      fi
}