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