How to share linux shrew soft vpn tap device with local QEMU VMs

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host (Ubuntu 16.04) has QEMU guest:



host-guest NAT network 192.168.100.0/24 IFs:



  • virbr2: host

  • virbr2-nic: guest

Host also has:



  • eno1: connecting to public internet router. Subnet 192.168.1.0/24

  • tap0: shrew soft vpn subnet 192.168.200.0/24 with fixed ip 192.168.200.20

host /proc/sys/net/ipv4/ip_forward is 1.



  • Pings from guest to public internet router are answered just fine, NAT works.

  • Pings from host to some vpn-peer also work out fine.

  • Pings from guest to some vpn-peer miss the final telegram back to the guest:
    Wireshark shows the ping-reply from the vpn-peer to the host's tap0 but the ping-reply is not relayed back to the guest.

There is no special handling for the tap0 in iptables.



Whats wrong, how do I fix this?



Update:



Found a thread describing a similar problem (no solution yet):



http://www.spinics.net/lists/netfilter/msg54779.html



Do iptables need to know some ipsec details do succeed SNATing back to the guest?




networking iptables virtual-machine vpn ipsec




share|improve this question






















  • Did you find a solution to this problem?
    – Donbhupi
    Aug 26 at 13:24














up vote
0
down vote

favorite












host (Ubuntu 16.04) has QEMU guest:



host-guest NAT network 192.168.100.0/24 IFs:



  • virbr2: host

  • virbr2-nic: guest

Host also has:



  • eno1: connecting to public internet router. Subnet 192.168.1.0/24

  • tap0: shrew soft vpn subnet 192.168.200.0/24 with fixed ip 192.168.200.20

host /proc/sys/net/ipv4/ip_forward is 1.



  • Pings from guest to public internet router are answered just fine, NAT works.

  • Pings from host to some vpn-peer also work out fine.

  • Pings from guest to some vpn-peer miss the final telegram back to the guest:
    Wireshark shows the ping-reply from the vpn-peer to the host's tap0 but the ping-reply is not relayed back to the guest.

There is no special handling for the tap0 in iptables.



Whats wrong, how do I fix this?



Update:



Found a thread describing a similar problem (no solution yet):



http://www.spinics.net/lists/netfilter/msg54779.html



Do iptables need to know some ipsec details do succeed SNATing back to the guest?




networking iptables virtual-machine vpn ipsec




share|improve this question






















  • Did you find a solution to this problem?
    – Donbhupi
    Aug 26 at 13:24












up vote
0
down vote

favorite









up vote
0
down vote

favorite











host (Ubuntu 16.04) has QEMU guest:



host-guest NAT network 192.168.100.0/24 IFs:



  • virbr2: host

  • virbr2-nic: guest

Host also has:



  • eno1: connecting to public internet router. Subnet 192.168.1.0/24

  • tap0: shrew soft vpn subnet 192.168.200.0/24 with fixed ip 192.168.200.20

host /proc/sys/net/ipv4/ip_forward is 1.



  • Pings from guest to public internet router are answered just fine, NAT works.

  • Pings from host to some vpn-peer also work out fine.

  • Pings from guest to some vpn-peer miss the final telegram back to the guest:
    Wireshark shows the ping-reply from the vpn-peer to the host's tap0 but the ping-reply is not relayed back to the guest.

There is no special handling for the tap0 in iptables.



Whats wrong, how do I fix this?



Update:



Found a thread describing a similar problem (no solution yet):



http://www.spinics.net/lists/netfilter/msg54779.html



Do iptables need to know some ipsec details do succeed SNATing back to the guest?




networking iptables virtual-machine vpn ipsec




share|improve this question














host (Ubuntu 16.04) has QEMU guest:



host-guest NAT network 192.168.100.0/24 IFs:



  • virbr2: host

  • virbr2-nic: guest

Host also has:



  • eno1: connecting to public internet router. Subnet 192.168.1.0/24

  • tap0: shrew soft vpn subnet 192.168.200.0/24 with fixed ip 192.168.200.20

host /proc/sys/net/ipv4/ip_forward is 1.



  • Pings from guest to public internet router are answered just fine, NAT works.

  • Pings from host to some vpn-peer also work out fine.

  • Pings from guest to some vpn-peer miss the final telegram back to the guest:
    Wireshark shows the ping-reply from the vpn-peer to the host's tap0 but the ping-reply is not relayed back to the guest.

There is no special handling for the tap0 in iptables.



Whats wrong, how do I fix this?



Update:



Found a thread describing a similar problem (no solution yet):



http://www.spinics.net/lists/netfilter/msg54779.html



Do iptables need to know some ipsec details do succeed SNATing back to the guest?





networking iptables virtual-machine vpn ipsec





share|improve this question













share|improve this question




share|improve this question








edited Dec 15 '17 at 11:34

























asked Dec 15 '17 at 0:03









user771723

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  • Did you find a solution to this problem?
    – Donbhupi
    Aug 26 at 13:24
















  • Did you find a solution to this problem?
    – Donbhupi
    Aug 26 at 13:24















Did you find a solution to this problem?
– Donbhupi
Aug 26 at 13:24




Did you find a solution to this problem?
– Donbhupi
Aug 26 at 13:24















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