Leela, I think what you describe is roughly how I had plumbed the ACL plugin into the L2 datapath before the l2 feature arc infra.
https://gerrit.fd.io/r/#/c/15165/ might be thus useful to glance. (The deleted part) --a > On 7 Feb 2019, at 23:23, Gudimetla, Leela Sankar <lgudi...@ciena.com> wrote: > > Thanks a ton Neale for sharing the detailed view. > > From the example you mentioned, “to send to a GRE interface for output if a > classifier is matched”, > can I configure this classifier using VPP constructs i.e. > policy-classifier/ACL/N-tuple-classifier(https://wiki.fd.io/view/VPP/Introduction_To_N-tuple_Classifiers) > ? > > My use-case also involves ‘extract’ a packet that matches some criteria. For > e.g., matching particular fields (DMAC, ether-type, port, etc) in the packet > with the value-of-interest. > > Thanks, > Leela sankar > > From: <vpp-dev@lists.fd.io> on behalf of "Neale Ranns via Lists.Fd.Io" > <nranns=cisco....@lists.fd.io> > Reply-To: "nra...@cisco.com" <nra...@cisco.com> > Date: Wednesday, February 6, 2019 at 10:51 PM > To: Leela Gudimetla <lgudi...@ciena.com>, "vpp-dev@lists.fd.io" > <vpp-dev@lists.fd.io> > Cc: "vpp-dev@lists.fd.io" <vpp-dev@lists.fd.io> > Subject: Re: [**EXTERNAL**] [vpp-dev] Understanding feature-arcs & features > > the vlib graph is a completely free form directed and acyclic. Meaning you > can construct a graph of any nodes ‘pointing’ to any other. > > A router or switch has a well-known set of functions and so a graph is built > in VPP to implement these functions. This graph is typically referred to as > the L3 or L2 switch path. In order for you to augment this switch-path you > need to hook your node into the existing graph. Using vlib functions you > could build a edge from any node in the switch path to point to your new > node, say from ip4-input to my-node, however, without modifications to > ip4-input to ‘classify’ packets of interest there is no way a packet would > make it to your node. The community is unlikely to accept changes to > ip4-input and indeed any other node on the switch-path as they are > performance critical. > > This is what feature arcs are for. A ‘feature’ in this context is any > subsystem/module/etc that wants to see/modify/fiddle with the packet as it > traverses the switch-path. > > A feature arc is a sub-graph of nodes – maybe graph is too flexible a word in > this context as it’s really only an ordered linear set, or pipeline, of > nodes. A feature-arc is rooted, or begins, at one of the nodes defined in the > switch-path and ends at the next node in the switch-path (one can imagine it > starting and ending at the same node and then immediately moving onto the > next). Any node on the arc has the usual choice of sending the packet to the > next node of its choice, e.g. to send to a GRE interface for output if a > classifier matched, or drop it, and thus ‘extract’ the packet from the > switch-path, or it can select the next feature/node on the arc so the packet > can continue along the switch-path. > > The L2 and L3 switch-path both have feature arcs that are rooted at different > places (see slide 15 of the attached deck for L3). > > How you use a feature-arc is well described in the wiki you reference. > > Benoit recently added a neat feature that allows you to visualise the graph; > show vlib graphviz > > which might help you understand the monsters you create 😉 > > /neale > > > > De : <vpp-dev@lists.fd.io> au nom de "Gudimetla, Leela Sankar" > <lgudi...@ciena.com> > Date : jeudi 7 février 2019 à 02:43 > À : "vpp-dev@lists.fd.io" <vpp-dev@lists.fd.io> > Objet : Re: [**EXTERNAL**] [vpp-dev] Understanding feature-arcs & features > > Dave/Neale, > > Sharing any details would help to understand better on top of ‘use the force > and read the source’. > > Thanks, > Leela sankar > > From: <vpp-dev@lists.fd.io> on behalf of Leela Gudimetla <lgudi...@ciena.com> > Date: Wednesday, February 6, 2019 at 11:35 AM > To: "vpp-dev@lists.fd.io" <vpp-dev@lists.fd.io> > Subject: [**EXTERNAL**] [vpp-dev] Understanding feature-arcs & features > > Hello All, > > I have a use case with VPP as below. > 1. Need to send customized packets (similar to some L3 control packets. > ARP, ICMP, etc) from ‘my-node’ to loopback. > 2. The loopback interface is attached to a bridge-domain. So, the > customized packets need to be either flooded in the bridge-domain or > sent on a particular interface based on the destination-MAC in the packet. > > From the code-walk, I see that loopback-interface has a set of nodes i.e. > ‘output-node’ and ‘tx-node’ created as part of interface creation. > And I also see that the loopback-interface tx-node is added next to its > output-node. And the output-node is added to ‘interface-output’ feature-arc. > > I looked at the https://wiki.fd.io/view/VPP/Feature_Arcs and also lot of code > that does VPP_FEATURE_ARC_INIT & VPP_FEATURE_INIT, to get a clear > understanding on how my customized packet would traverse the VPP’s node > graph. But somehow I am missing the full packet traversal after the > loopback-interface’s output-node. > > Could someone share details on how the feature-arcs and ‘features that use > the feature-arcs’ work? > And to be specific how the ‘interface-output’ feature-arc works in order to > send the packet out from loopback-interface output-node to the corresponding > NIC? > And why is that ‘tx-node’ needed/used? > > Too many questions, but any help understanding the flow would really help. > > Thanks, > Leela sankar > > -=-=-=-=-=-=-=-=-=-=-=- > Links: You receive all messages sent to this group. > > View/Reply Online (#12209): https://lists.fd.io/g/vpp-dev/message/12209 > Mute This Topic: https://lists.fd.io/mt/29685539/675608 > Group Owner: vpp-dev+ow...@lists.fd.io > Unsubscribe: https://lists.fd.io/g/vpp-dev/unsub [ayour...@gmail.com] > -=-=-=-=-=-=-=-=-=-=-=-
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