sFlow inserted twice on same graph arc?

[sflow]

We need to make sure that enabling sFlow on an interface twice does not insert the sampling node into the graph twice.

[pimvanpelt]

I can confirm this does happen. If we:

sflow enable-disable TenGigabitEthernet130/0/0
sflow enable-disable TenGigabitEthernet130/0/0
sflow enable-disable TenGigabitEthernet130/0/0
sflow enable-disable TenGigabitEthernet130/0/0

We will receive 4x the samples on the PSAMPLE netlink channel.

One way to detect this is to mark an interface as enabled (see #3 for more on this) and if it's enabled, refused to add the feature again on https://github.com/sflow/vpp-sflow/blame/main/sflow/sflow.c#L322

[sflow]

I believe this issue is addressed by the latest commit, which introduces per-interface data in sflow-main and uses it to gate the enable_disable config changes.
2684082

[pimvanpelt]

Confirmed - we only call vnet_feature_enable_disable() at most once now per interface.