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Installing microk8s breaks existing workload e.g. mysql on LXD due to br_netfilter + kubenet SNAT #62

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nobuto-m opened this issue Jul 4, 2018 · 2 comments
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Installing microk8s breaks existing workload e.g. mysql on LXD due to br_netfilter + kubenet SNAT #62

nobuto-m opened this issue Jul 4, 2018 · 2 comments
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@nobuto-m
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nobuto-m commented Jul 4, 2018 •
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I have "lxdbr0" as a LXD network bridge for my Juju test bed. After installing microk8s, mysql / percona-cluster charm deployments failed because those charms relies on peers' source IP addresses.

br_netfilter and kubenet SNAT iptables will be applied unconditionally after installing microk8s, so LXD private network communication is also affected by the MASQUERADE rule. For example, a packet of 10.0.8.102 -> 10.0.8.2, will be modified as 10.0.8.1 -> 10.0.8.22 on lxdbr0 which will be blocked by MySQL source IP address ACLs.

Although the iptables rule is enabled by kubelet and kubenet, if microk8s could apply some conditions onto the rule, that would be nice.
https://github.com/kubernetes/kubernetes/blob/692f9bb7b1fa6ca72ddd5a305607d79f9684e907/pkg/kubelet/dockershim/network/kubenet/kubenet_linux.go#L169-L181

[existing lxdbr0 bridge]

$ ip a s dev lxdbr0
8: lxdbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether fe:22:7a:6f:a3:09 brd ff:ff:ff:ff:ff:ff
    inet 10.0.8.1/24 scope global lxdbr0
       valid_lft forever preferred_lft forever
    inet6 fe80::30b2:deff:fe7a:383f/64 scope link 
       valid_lft forever preferred_lft forever

[existing iptables rules]

$ sudo iptables -t nat -L POSTROUTING -v
Chain POSTROUTING (policy ACCEPT 164 packets, 12290 bytes)
 pkts bytes target     prot opt in     out     source               destination         
   30  1836 MASQUERADE  all  --  any    any     10.0.8.0/24         !10.0.8.0/24          /* generated for LXD network lxdbr0 */
    4   309 MASQUERADE  all  --  any    any     10.112.155.0/24     !10.112.155.0/24     
    0     0 MASQUERADE  udp  --  any    any     10.112.155.0/24     !10.112.155.0/24      masq ports: 1024-65535
    0     0 MASQUERADE  tcp  --  any    any     10.112.155.0/24     !10.112.155.0/24      masq ports: 1024-65535
    0     0 RETURN     all  --  any    any     10.112.155.0/24      255.255.255.255     
    0     0 RETURN     all  --  any    any     10.112.155.0/24      base-address.mcast.net/24 
    5   332 RETURN     all  --  any    any     192.168.122.0/24     base-address.mcast.net/24 
    0     0 RETURN     all  --  any    any     192.168.122.0/24     255.255.255.255     
    0     0 MASQUERADE  tcp  --  any    any     192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
    0     0 MASQUERADE  udp  --  any    any     192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
    0     0 MASQUERADE  all  --  any    any     192.168.122.0/24    !192.168.122.0/24

[traffic 10.0.8.102 -> 10.0.8.2]

Jul  4 17:44:08    462 10.0.8.102 TCP_MISS/304 360 GET http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease - HIER_DIRECT/91.189.88.162 -
Jul  4 17:44:08    473 10.0.8.102 TCP_REFRESH_UNMODIFIED/200 107244 GET http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease - HIER_DIRECT/91.189.88.162 -
Jul  4 17:44:08    235 10.0.8.102 TCP_REFRESH_UNMODIFIED/200 109644 GET http://archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease - HIER_DIRECT/91.189.88.162 -
Jul  4 17:44:08    476 10.0.8.102 TCP_REFRESH_UNMODIFIED/200 107272 GET http://archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease - HIER_DIRECT/91.189.88.162 -

-> source IP = 10.0.8.102

[install microk8s]

$ sudo snap install microk8s --classic --edge

[new iptables rules]

$ sudo iptables -t nat -L POSTROUTING -v
Chain POSTROUTING (policy ACCEPT 49 packets, 2947 bytes)
 pkts bytes target     prot opt in     out     source               destination         
  341 20493 KUBE-POSTROUTING  all  --  any    any     anywhere             anywhere             /* kubernetes postrouting rules */
    0     0 MASQUERADE  all  --  any    !docker0  172.17.0.0/16        anywhere            
   30  1836 MASQUERADE  all  --  any    any     10.0.8.0/24         !10.0.8.0/24          /* generated for LXD network lxdbr0 */
    4   309 MASQUERADE  all  --  any    any     10.112.155.0/24     !10.112.155.0/24     
    0     0 MASQUERADE  udp  --  any    any     10.112.155.0/24     !10.112.155.0/24      masq ports: 1024-65535
    0     0 MASQUERADE  tcp  --  any    any     10.112.155.0/24     !10.112.155.0/24      masq ports: 1024-65535
    0     0 RETURN     all  --  any    any     10.112.155.0/24      255.255.255.255     
    0     0 RETURN     all  --  any    any     10.112.155.0/24      base-address.mcast.net/24 
    6   405 RETURN     all  --  any    any     192.168.122.0/24     base-address.mcast.net/24 
    0     0 RETURN     all  --  any    any     192.168.122.0/24     255.255.255.255     
    0     0 MASQUERADE  tcp  --  any    any     192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
    0     0 MASQUERADE  udp  --  any    any     192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
    0     0 MASQUERADE  all  --  any    any     192.168.122.0/24    !192.168.122.0/24    
    3   222 MASQUERADE  all  --  any    any     anywhere            !10.152.183.0/24      /* kubenet: SNAT for outbound traffic from cluster */ ADDRTYPE match dst-type !LOCAL

[traffic 10.0.8.102 -> 10.0.8.2]

Jul  4 17:48:36    390 10.0.8.1 TCP_REFRESH_UNMODIFIED/200 107244 GET http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease - HIER_DIRECT/91.189.91.23 -
Jul  4 17:48:36    514 10.0.8.1 TCP_MISS/304 360 GET http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease - HIER_DIRECT/91.189.88.162 -
Jul  4 17:48:36    234 10.0.8.1 TCP_REFRESH_UNMODIFIED/200 109644 GET http://archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease - HIER_DIRECT/91.189.88.162 -
Jul  4 17:48:37    472 10.0.8.1 TCP_REFRESH_UNMODIFIED/200 107272 GET http://archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease - HIER_DIRECT/91.189.88.162 -

-> source IP = 10.0.8.1

FWIW,

$ sudo rmmod br_netfilter

OR

$ sudo iptables -t nat -D POSTROUTING ! -d 10.152.183.0/24 \
    -m comment --comment "kubenet: SNAT for outbound traffic from cluster" \
    -m addrtype ! --dst-type LOCAL -j MASQUERADE

will temporarily disable the unwanted behavior, but it will break Kubernetes...
@nobuto-m
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nobuto-m commented Jul 4, 2018

Related line:
https://github.com/juju-solutions/microk8s/blob/006353429d0af976d89fb1c8291e53fe54730e4d/microk8s-resources/default-args/kubelet#L9

@ktsakalozos ktsakalozos added the kind/bug Something isn't working label Jul 8, 2018
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stale bot commented Apr 4, 2020

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

@stale stale bot added the inactive label Apr 4, 2020
@stale stale bot closed this as completed Jul 7, 2020
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