Hi everyone,
I'm looking at OpenContrail (3.1 if that matters) code to figure out how
BGPaaS flows are installed in the vRouter. This is what I've got so far:
Config phase:
-------------
- InterfaceNH::CreatePacketInterfaceNh() creates two next hops (nh) for
pkt0: one with policy disabled and one with policy enabled
- VnTable::AddIPAMRoutes() creates a route to the VN's default gateway
via the policy-enabled nexthop, as "we want to trap BGPaaS flows" (as
the comment says).
- NHKSyncEntry::Encode() pushes NH_FLAG_FLOW_LOOKUP to the kernel if
both policy and relaxed_policy are enabled for the interface.
Runtime phase - vRouter Agent:
------------------------------
- VrouterControllerInterface::Process() captures a packet from pkt0,
decodes agent headers and sends it to the PktHandler::Process()
- PktHandler::ParsePacket() is called which checks if this packet was
trapped due to TRAP_FLOW_MISS or TRAP_ACTION_HOLD (or TRAP_ECMP_RESOLVE,
actually). If so, it checks if it is a BGP SYN packet, creates the
corresponding NAT flow for BGPaaS and pushes it to the kernel.
So far, so good. Now, let us see what happens inside vRouter:
- Both TRAP_FLOW_MISS and TRAP_ACTION_HOLD are set in vr_trap_flow()
- vr_trap_flow() is called from vr_enqueue_flow()
- vr_enqueue_flow() is called from vr_do_flow_action() if
VR_FLOW_ACTION_HOLD is set
- vr_do_flow_action() is called from vr_flow_lookup(), which also sets
VR_FLOW_ACTIOB_HOLD on the flow if it's a new one (true for the SYN
packet) **UNLESS** the corresponding next hop has NH_FLAG_FLOW_LOOKUP flag.
Bang! We set the NH_FLAG_FLOW_LOOKUP flag to trap new BGP sessions to
agent, and this very flag prevents them from being trapped with an
appropriate reason.
I doubt it's a bug as I have an impression BGPaaS works in 3.1, at least
to some extent.
So which piece of a puzzle am I missing?
Sukhdev, you are a kind of point of contact in the TSC: may I ask you to
summon a Juniper's BGPaaS expert in this thread? :-) Many thanks!
Cheers,
Valentine
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