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https://issues.apache.org/jira/browse/CLOUDSTACK-9339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15443235#comment-15443235
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ASF GitHub Bot commented on CLOUDSTACK-9339:
--------------------------------------------
Github user dsclose commented on the issue:
https://github.com/apache/cloudstack/pull/1659
@murali-reddy - thank you for picking this up. Let me know when you think
it's appropriate to close PR #1519 and I shall do so.
> Virtual Routers don't handle Multiple Public Interfaces
> -------------------------------------------------------
>
> Key: CLOUDSTACK-9339
> URL: https://issues.apache.org/jira/browse/CLOUDSTACK-9339
> Project: CloudStack
> Issue Type: Bug
> Security Level: Public(Anyone can view this level - this is the
> default.)
> Components: Virtual Router
> Affects Versions: 4.8.0
> Reporter: dsclose
> Labels: firewall, nat, router
>
> There are a series of issues with the way Virtual Routers manage multiple
> public interfaces. These are more pronounced on redundant virtual router
> setups. I have not attempted to examine these issues in a VPC context.
> Outside of a VPC context, however, the following is expected behaviour:
> * eth0 connects the router to the guest network.
> * In RvR setups, keepalived manages the guests' gateway IP as a virtual IP on
> eth0.
> * eth1 provides a local link to the hypervisor, allowing Cloudstack to issue
> commands to the router.
> * eth2 is the routers public interface. By default, a single public IP will
> be setup on eth2 along with the necessary iptables and ip rules to source-NAT
> guest traffic to that public IP.
> * When a public IP address is assigned to the router that is on a separate
> subnet to the source-NAT IP, a new interface is configured, such as eth3, and
> the IP is assigned to that interface.
> * This can result in eth3, eth4, eth5, etc. being created depending upon how
> many public subnets the router has to work with.
> The above all works. The following, however, is currently not working:
> * Public interfaces should be set to DOWN on backup redundant routers. The
> master.py script is responsible for setting public interfaces to UP during a
> keepalived transition. Currently the check_is_up method of the CsIP class
> brings all interfaces UP on both RvR. A proposed fix for this has been
> discussed on the mailing list. That fix will leave public interfaces DOWN on
> RvR allowing the keepalived transition to control the state of public
> interfaces. Issue #1413 includes a commit that contradicts the proposed fix
> so it is unclear what the current state of the code should be.
> * Newly created interfaces should be set to UP on master redundant routers.
> Assuming public interfaces should be default be DOWN on an RvR we need to
> accommodate the fact that, as interfaces are created, no keepalived
> transition occurs. This means that assigning an IP from a new public subnet
> will have no effect (as the interface will be down) until the network is
> restarted with a "clean up."
> * Public interfaces other than eth2 do not forward traffic. There are two
> iptables rules in the FORWARD chain of the filter table created for eth2 that
> allow forwarding between eth2 and eth0. Equivalent rules are not created for
> other public interfaces so forwarded traffic is dropped.
> * Outbound traffic from guest VMs does not honour static-NAT rules. Instead,
> outbound traffic is source-NAT'd to the networks default source-NAT IP. New
> connections from guests that are destined for public networks are processed
> like so:
> 1. Traffic is matched against the following rule in the mangle table that
> marks the connection with a 0x0:
> *mangle
> -A PREROUTING -i eth0 -m state --state NEW -j CONNMARK --set-xmark
> 0x0/0xffffffff
> 2. There are no "ip rule" statements that match a connection marked 0x0, so
> the kernel routes the connection via the default gateway. That gateway is on
> source-NAT subnet, so the connection is routed out of eth2.
> 3. The following iptables rules are then matched in the filter table:
> *filter
> -A FORWARD -i eth0 -o eth2 -j FW_OUTBOUND
> -A FW_OUTBOUND -j FW_EGRESS_RULES
> -A FW_EGRESS_RULES -j ACCEPT
> 4. Finally, the following rule is matched from the nat table, where the IP
> address is the source-NAT IP:
> *nat
> -A POSTROUTING -o eth2 -j SNAT --to-source 123.4.5.67
>
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