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Subject: Re: [wireguard-android] 'roaming' from LTE to WiFi with version
 0.0.20180523
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On 2018-05-24 05:16, nnet wrote:
> So this is how it ends:
>
> 05-23 20:33:45.323  9600  9619 D WireGuard/GoBackend/wireguard: peer(AsMM…SeWg) - Sending handshake initiation                                    
> 05-23 20:33:45.326  9600  9619 E WireGuard/GoBackend/wireguard: peer(AsMM…SeWg) - Failed to send handshake initiation write udp6 [::]:46719->[]:41414: sendto: network is unreachable                                                                                      
> 05-23 20:33:45.326  9600  9619 D WireGuard/GoBackend/wireguard: peer(AsMM…SeWg) - Awaiting keypair                                                
> 05-23 20:33:50.367  9600  9678 D WireGuard/GoBackend/wireguard: peer(AsMM…SeWg) - Sending handshake initiation                                    
> 05-23 20:33:50.376  9600  9678 E WireGuard/GoBackend/wireguard: peer(AsMM…SeWg) - Failed to send handshake initiation write udp6 [::]:46719->[snip]:41414: sendto: network is unreachable
> 05-23 20:36:10.188  9600 11291 D WireGuard/GoBackend/wireguard: peer(AsMM…SeWg): Handshake did not complete after 20 attempts, giving up
> 05-23 20:39:12.258  9600  9677 D WireGuard/GoBackend/wireguard: :peer(AsMM…SeWg) Removing all keys, since we haven't received a new one in 540 seconds
>
> Interestingly it's trying to send out to an IPv6 address. The peer endpoint IP is IPv4 only (the LTE is IPv4-in-6).

In the wg command it resolves the domain once and picks the preferred protocol family of the system (which is ipv6 when its available).
Since this is only done once it will stick to ipv6 for ever until the VPN is reconfigured by wg.
This is an unsolved known problem.