Multiple unreachable

[Kent Friis]

I have a pretty simple Wireguard setup between two machines. The power
supply in my brothers server died, so the tunnel is of course down. My
machine is running Linux 5.6.7 (from kernel.org, no patches or out of
tree drivers) with in-kernel Wireguard.

To see if he has gotten his server back up, I tried to ping it (via the
tunnel). That gave more unreachable responses than expected (note the
sequence number):

PING 172.16.1.1 (172.16.1.1) 56(84) bytes of data.
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
...
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
>From 172.24.0.1 icmp_seq=1 Destination Host Unreachable
ping: sendmsg: Destination address required
^C
--- 172.16.1.1 ping statistics ---
1 packets transmitted, 0 received, +50 errors, 100% packet loss, time 0ms

172.24.0.1 is my end.
172.16.1.1 is my brother (not online)

rc.wireguard:
ip link add dev wg0 type wireguard
wg setconf wg0 /etc/wireguard/wg0.conf
ip address add dev wg0 172.24.0.1
ip link set up dev wg0
ip route add 172.16.1.0/24 dev wg0

wg0.conf:
[Interface]
PrivateKey = removed
ListenPort = 51820

[Peer]
PublicKey = also removed
AllowedIPs = 172.16.1.0/24

My PC has been rebooted since the tunnel was last up, so Wireguard has no
ip address for the other end.

This is not causing any problems that I've noticed, but I assume there is
a bug somewhere to give this many errors. Pinging an unreachable host on the
LAN only gives one "Host Unreachable" message per sequence number.

-Kent