Motivation
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==========
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One of the nice things about network namespaces is that they allow one
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to easily create and test complex environments.
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Unfortunately, these namespaces can not be used with actual switching
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ASICs, as their ports can not be migrated to other network namespaces
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(NETIF_F_NETNS_LOCAL) and most of them probably do not support the
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L1-separation provided by namespaces.
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However, a similar kind of flexibility can be achieved by using VRFs and
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by looping the switch ports together. For example:
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br0
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+
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vrf-h1 | vrf-h2
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+ +---+----+ +
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| | | |
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192.0.2.1/24 + + + + 192.0.2.2/24
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swp1 swp2 swp3 swp4
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+ + + +
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| | | |
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+--------+ +--------+
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The VRFs act as lightweight namespaces representing hosts connected to
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the switch.
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This approach for testing switch ASICs has several advantages over the
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traditional method that requires multiple physical machines, to name a
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few:
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1. Only the device under test (DUT) is being tested without noise from
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other system.
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2. Ability to easily provision complex topologies. Testing bridging
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between 4-ports LAGs or 8-way ECMP requires many physical links that are
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not always available. With the VRF-based approach one merely needs to
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loopback more ports.
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These tests are written with switch ASICs in mind, but they can be run
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on any Linux box using veth pairs to emulate physical loopbacks.
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Guidelines for Writing Tests
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============================
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o Where possible, reuse an existing topology for different tests instead
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of recreating the same topology.
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o Tests that use anything but the most trivial topologies should include
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an ASCII art showing the topology.
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o Where possible, IPv6 and IPv4 addresses shall conform to RFC 3849 and
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RFC 5737, respectively.
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o Where possible, tests shall be written so that they can be reused by
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multiple topologies and added to lib.sh.
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o Checks shall be added to lib.sh for any external dependencies.
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o Code shall be checked using ShellCheck [1] prior to submission.
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1. https://www.shellcheck.net/
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