Add ifIndex and RPF checks #1022
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added 2 commits
October 7, 2020 08:20
Copy was copying only data, losing all metadata in the process. This resulted in very erratic behaviour of Replicate in a pipeline which relies on metadata to identify packets.
This is a set of basic functionality which is present in all switching and forwarding frameworks. They all set/keep packet origin in the packet metadata. The reason is that knowing your "in" interface is essential for most forwarding decisions. Example - you cannot implement even a basic hub without knowing your "in" interface, because you are not supposed to send packets to the interface which originated them. There are similar requirements for forwarding, security, acls, etc. This changeset adds the following functionality: 1. Each port gets an ifIndex similar to ifIndex in SNMP assigned on creation. 2. PortInc now always sets an integer metadata called ifIndex with the ifIndex value. 3. PortOut now can optionally check if the packet is being sent out from its arrival port and drop it. The default behavious is rpf check off - to emulate previous BESS behaviour. Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
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This is a basic requirement for most switching/routing algorithms.
Example - most trivial possible "hub" - two ports wired to a replicator and two Linux instances off them:
UnixSocketPort(name='u0', path="/var/tmp/uml-test-0")
UnixSocketPort(name='u1', path="/var/tmp/uml-test-1")
PortInc(port="u0") -> repl::Replicate(gates=[0,1])
PortInc(port="u1") -> repl
repl:0 -> PortOut(port="u0")
repl:1 -> PortOut(port="u1")
This behaves pretty badly with BESS as is because the packets sent out of port 0 are also received on port 0 and vice versa.
Adding this change and enabling it results in the correct expected behaviour and correct high throughput.
UnixSocketPort(name='u0', path="/var/tmp/uml-test-0")
UnixSocketPort(name='u1', path="/var/tmp/uml-test-1")
PortInc(port="u0") -> repl::Replicate(gates=[0,1])
PortInc(port="u1") -> repl
repl:0 -> PortOut(port="u0", rpfcheck=1)
repl:1 -> PortOut(port="u1", rpfcheck=1)
I have tried to preserve packet batching to the extent possible for packets being sent. As a result of the "drops" the batches may now be a bit smaller, but it will still batch.
A.