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From dsclose <...@git.apache.org>
Subject [GitHub] cloudstack pull request: Cloudstack 9339: Virtual Routers do not h...
Date Wed, 25 May 2016 14:50:03 GMT
GitHub user dsclose reopened a pull request:

    https://github.com/apache/cloudstack/pull/1519

    Cloudstack 9339: Virtual Routers do not handle Multiple Public Interfaces

    This PR addresses CLOUDSTACK-9339 and may need a code review from someone familiar with
the System VM scripts. In particular, this PR has not been tested in a VPC RvR context. Only
standalone routers and RvR routers have been demonstrated.
    
    - **d582358: Leave public interfaces down in backup redundant routers.** Previously backup
routers were bringing all interfaces up and thus arping public IPs away from the master router.
    - **9ee1eb6: Add the default gateway to the main routing table when interfaces are configured.**
The gateway for the first public IP was always being added to the main routing table. Sometimes
a router would consequently add the gateway for an IP other than the default source-NAT IP.
This would prevent outbound connectivity for guest VMs.
    - **ad9d72f: Add default gateway to device-specific routing tables.** Link-level routes
were being put into the device-specific routing tables (accessed via firewall marks) but these
are unnecessary. Instead, the default gateway is needed to allow the kernel to make an appropriate
routing decision.
    - **8db879e: Only mark guest connections when they are part of a static-NAT.** Guest connections
were being marked with a zero. This added no functionality and prevented static-NAT rules
from routing outbound traffic properly as device-specific routing tables would not be used.
Instead, all traffic would be routed out via the default public interface.
    - **788b1be: Allow forwarding and collect network stats on any public interface.** Forwarding
rules and network stats were limited to eth2 on RvR networks. This needed to be decoupled
from eth2 and reapplied to whichever interface was under consideration.
    - **b19e8aa: Ensure that CONNMARK --restore-mark only appears once.** This is a bit of
a hack and can do with being improved. The CONNMARK rule was not being picked up by the de-duplication
logic in CsNetfilter and was being added twice. This caused checksum errors on packets traversing
NAT.
    - **bf285e1: Transition to master state should add all necessary routes.** Now that backup
routers keep their interfaces down, the route logic executed at configuration-time cannot
be applied. Instead, once the interface is brought up during a transition to master, routers
must re-evaluate what routes are needed and add them. Unfortunately I couldn't see a way to
re-use the existing route logic with the variables that I had in scope so there is some duplication.
In some cases, routers did not successfully arp IPs away from the old master so some arp logic
was added. During a failover most connections with guest VMs will be maintained with only
minor packet loss. SSH sessions implemented via port-forwarding rules on an interface other
than the source-NAT interface consistently get dropped, however, so the failover isn't quite
seamless. It's possible that there's an easy fix for that.
    
    I expect that a number of tests may need to be modified/written as part of this PR. Any
feedback or pointers would be useful as initially I'll be relying on the CI failures to tell
me where to look.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/dsclose/cloudstack CLOUDSTACK-9339

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/cloudstack/pull/1519.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #1519
    
----
commit e7a63be161bdd14c985a8b483bffe4bfdaa3f5d4
Author: dean.close <dean.close@icloudhosting.com>
Date:   2016-05-09T10:31:26Z

    CLOUDSTACK-9339: Handle multiple public subnets on virtual routers.

----


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