[Users] vz 7 network capability and openVPN forward/masquerade

Wed Feb 26 00:11:21 MSK 2020

1) I meant you don't need any special capabilities to run openvpn.
Just the tun device should be available.

2) Sorry for the confusion, I meant the openvz networking. routed (venet
device) or bridged (veth). 

2.1) I don't use firewalld and not familiar with its syntax.
2.2) it really depends on how you wish the packets to travel.
if they are supposed to go through eth0 then you need to use
eth0 in all the configurations.
2.3) I honestly don't know if a name like eth0 at if248 is going to
be accepted by the tools.
2.4) I am not sure but probably in case of bridged networking
you will need to disable rp_filter. Not necessarily, depends on
your configuration. Set the sysctl variable to zero.

Example:

In my particular case openvpn is used to access private network at
remote location. I've got two addresses configured on venet0 device,
 let's say 123.124.125.126 and 192.168.192.168.
Private network is 192.168.192.0/24
openvpn uses 192.168.10.0/28 internal subnet with 192.168.10.1 being
assigned to tun0

openvpn config:
--
topology        subnet
ifconfig        192.168.10.1 255.255.255.240
mode            server

server	        192.168.10.0 255.255.255.240
push		"route 192.168.192.0 255.255.255.0"
--

sysctl.conf:
net.ipv4.ip_forward = 1

iptables:
:POSTROUTING ACCEPT [0:0]
[0:0] -A POSTROUTING -s 192.168.10.0/28 -j SNAT --to-source
192.168.192.168
COMMIT

That's all

now let's say I know for sure 192.168.192.100 is up and running in
the private network. I have an established connection to the vpn
from my local machine and try to ping it but there's no response.
I'd probably check things in the following order:

1) ip a l; ip r l on local machine to check that I have the connectiom
established and the route active

2) tcpdump on local tun device to check that the packets do leave

3) tcpdump on vpn's tun device to check that the packets do arrive

4) tcpdump on vpn's eth/venet device to check if the packets are routed
between interfaces and have the source address changed.

5) ping from vpn container - you might have weird filtering on the
server that hosts the container.

On Tue, 25 Feb 2020 16:32:43 +0100
Jehan Procaccia <Jehan.Procaccia at imtbs-tsp.eu> wrote:

> OK for 1) , then I don't need any capability (net_admin, sys_time), I 
> was wondering because I read that on lots of docs as in :
> https://github.com/OpenVZ/vz-docs/blob/master/virtuozzo_7_users_guide.asc
> perhaps deprecated ?
> 
> for 2) I use routed openvpn (tun0)
> yes I mess a lot between iptables and firewalld while debungin my pb
> 2.1) I would prefere to use firewalld , can you confirm me the rule
> you use ?
> POSTROUTING with masquerade or have you an iptable SNAT exemple ?
> 2.2) if I use a eth0 interface do you confirm that venet0 (that is
> Down on my CT) is not concerned at all ?
> 2.3) my eth0 appears as eth0 at if248 (ip addr) , is it important for
> the firewall-cmd command arguments => "-o eth0" ? should I use -o
> eth0 at if248 ! 2.4) what do you mean by |rp_filter| (reverse path
> filtering), should I disable it , how ?
> 
> Thanks .
> 
> 
> Le 25/02/2020 à 14:54, Dmitry Konstantinov a écrit :
> > openvpn does work. dev/tun:rw and full netfilter is all the
> > 'extras' I have in the container's config
> >
> > 1) not sure if it's still works but probably not useful in
> > this particular case, never used any capabilities for openvpn.
> >
> > 2) I use a single postrouting rule. Like the last one in your list.
> >
> >
> > I don't quite understand your setup. Do you use routed or bridged
> > networking? with firewalld you configure eth0 but I see venet0 in
> > iptables. I don't have much experience with eth devices inside
> > container, perhaps you might need to configure rp_filter for it
> > to work with openvpn.
> >
> >
> >
> >
> >
> > On Tue, 25 Feb 2020 10:21:33 +0100
> > Jehan Procaccia <Jehan.Procaccia at imtbs-tsp.eu> wrote:
> >  
> >> Hello
> >>
> >> I have running VPNs that works perfectly on openvz6 , now I move to
> >> openvz7 and I cannot make it forward or masquerade between
> >> interfaces .
> >>
> >> I am questionning about different concepts:
> >>
> >> 1) is enabling capablities still enable/usefull ?
> >>
> >> ie: prlctl set ctvpn --capability net_admin:on => doesn't save
> >> anything in the CT conf ...
> >>
> >> I did set
> >>
> >> prlctl set ctvpn --netfilter full  => in order to have nat and
> >> mangle chains
> >>
> >> 2) is using iptables or firewalld determinent ? masquerade or
> >> SNAT ?
> >>
> >> neither of those works
> >>
> >> for Masquerade I did
> >>
> >> firewall-cmd --permanent --direct --passthrough ipv4 -t nat -A
> >> POSTROUTING -s 10.91.10.0/22 -o eth0 -j MASQUERADE
> >>
> >> for iptables I tried with
> >>
> >> *nat
> >> :PREROUTING ACCEPT [0:0]
> >> :POSTROUTING ACCEPT [0:0]
> >> :OUTPUT ACCEPT [0:0]
> >> -A POSTROUTING -o venet0 -j SNAT --to-source 157.109.2.13
> >> -A POSTROUTING -s 10.91.10.0/22 -j SNAT --to-source 157.109.2.13
> >>
> >> by the way is venet0 important as it appears down in the CT !?
> >>
> >> 2: venet0: <BROADCAST,POINTOPOINT,NOARP> mtu 1500 qdisc noop state
> >> DOWN group default
> >>       link/void
> >> 3: eth0 at if248: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
> >> noqueue state UP group default qlen 1000
> >>
> >> dev/tun is working correctly
> >>
> >> I set it with: vzctl set ctvpn --devnodes net/tun:rw --save
> >>
> >> CT-ABC /# ls -l /dev/net/tun
> >> crw-rw-rw- 1 root root 10, 200 Feb 25 10:07 /dev/net/tun
> >> CT-ABC /# cat /dev/net/tun
> >> cat: /dev/net/tun: File descriptor in bad state  
> >> => message that means it is operational !  
> >>
> >> openvpn uses tun interface, connecting clients to openvpn server
> >> works fine, but routing between interfaces (tun0 and eth0 ) doesn't
> >> work .
> >>
> >> of course ip_forward is enabled
> >>
> >> CT-ABC /# cat /proc/sys/net/ipv4/ip_forward
> >> 1
> >>
> >> Thanks for your help .
> >>
> >> _______________________________________________
> >> Users mailing list
> >> Users at openvz.org
> >> https://lists.openvz.org/mailman/listinfo/users  
> >
> > _______________________________________________
> > Users mailing list
> > Users at openvz.org
> > https://lists.openvz.org/mailman/listinfo/users  
> 
> 