From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Neale Ranns Sent: Saturday, April 17, 2021 8:57 AM To: hem...@mnkcg.com; vpp-dev@lists.fd.io Subject: Re: [vpp-dev] dst mac-address look up?
From: hem...@mnkcg.com <mailto:hem...@mnkcg.com> <hem...@mnkcg.com <mailto:hem...@mnkcg.com> > Date: Friday, 16 April 2021 at 21:07 To: Neale Ranns <ne...@graphiant.com <mailto:ne...@graphiant.com> >, vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> <vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> > Subject: RE: [vpp-dev] dst mac-address look up? this is the definition of changing the semantics; there was an API that returned the mac address of the ip_neighbor object passed, now it uses the neighbor object passed as a key to find another neighbour object and return that address. Clients that use that API would be in for a shock. <hs> I don't see anything shocking. The ip-neighbor passed in has only the key setup to find any entry. A new API could just pass in a key to lookup an entry and then ip_neighbor_get_mac() is used to get the mac-address. My goal is simple: I have an IP/IP6 address and sw_index for use to find an entry in ARP/ND cache. On finding the entry, the mac-address of the entry is returned. This way if I know IP and egress interface for next-hop, I get the mac-address for next-hop to forward a packet. Then you're also missing the source mac and the vlan tags. <hs> No. Routing has already found the egress interface and thus interface link-type (vlan, mpls, native) and mac rewrite string is known. Retrieving these from the local interface and finding the ip-neighbor per-packet in the data-path is a considerable cost - the information is distributed across various memory locations, stored in tables that are not optimised. You should instead build in the control plane an address+interface lookup table and link the result to the appropriate adjacency. <hs> Agree on control-plane. ARP/ND are protocols with interface scope and routing found the egress interface. I just need to find the ARP/ND entry on the interface Further, I am using device-input and interface-output for a plugin - it is simpler for me to lookup ARP/ND table and not bother with any adjacency and ARP/ND link. Hemant
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