[resolved] P4runtime: No forwarding pipeline config or SEGFAULT

leonderooij · December 16, 2023, 10:58pm

Hi all!

I’m experimenting with creating a p4 application that forwards packets to a different destination based on table entries set by a custom c/c++ application.

The p4 program is here: rtpengine/test-dpu-offload/p4/softdpu.p4 at dpu_offload · oshlabs/rtpengine · GitHub

It allows the table entries to be set as is described here: rtpengine/test-dpu-offload/p4/README.md at dpu_offload · oshlabs/rtpengine · GitHub

So this all works when I’m using the regular simple_switch and manipulating the table using simple_switch_CLI.

I’m now trying to populate the tables over GRPC using p4runtime with the program that’s located here: rtpengine/test-dpu-offload/p4runtimeclient at dpu_offload · oshlabs/rtpengine · GitHub

But if I run it as it is there, the simple_switch_grpc segfaults.

It doesn’t segfault if I comment out this line: rtpengine/test-dpu-offload/p4runtimeclient/p4runtime_client_wrapper.cpp at dpu_offload · oshlabs/rtpengine · GitHub

But then I get the following error:

Failed to insert table entry: No forwarding pipeline config set for this device

Does anyone know what I’m doing wrong?

Thank you,

Leon

leonderooij · December 16, 2023, 11:03pm

Wondering if it’s correct to push the literal JSON here:

github.com

oshlabs/rtpengine/blob/dpu_offload/test-dpu-offload/p4runtimeclient/p4runtime_client_wrapper.cpp#L67


      
          // NOTE NOTE THIS MAKES simple_switch_grpc CRASH !!! !!! !!!
          // https://p4.org/p4-spec/p4runtime/main/P4Runtime-Spec.html#sec-setforwardingpipelineconfig-rpc
          void setForwardingPipeline() {
              p4::v1::SetForwardingPipelineConfigRequest request;
              p4::v1::SetForwardingPipelineConfigResponse response;
              grpc::ClientContext context;
              
              // Assuming 'p4info' and 'device_config' are std::string containing the P4Info and device config data
              auto* config = request.mutable_config();
              //config->mutable_p4info()->set_preamble(p4info);
              config->set_p4_device_config(device_config);
              
              // Set the action and device id
              request.set_action(p4::v1::SetForwardingPipelineConfigRequest::RECONCILE_AND_COMMIT);
              //request.set_action(p4::v1::SetForwardingPipelineConfigRequest::VERIFY);
          
              //request.add_device_ids(0);  // The target device ID
              request.set_device_id(0);  // The target device ID
              
              // Send the request
              grpc::Status status = stub_->SetForwardingPipelineConfig(&context, request, &response);

?

leonderooij · December 17, 2023, 9:06am

I made a pcap of the p4runtime/grpc traffic going over the wire, it can be found here: rtpengine/test-dpu-offload/simple_switch_grpc_crash.pcap at dpu_offload · oshlabs/rtpengine · GitHub

I see the whole JSON is sent (frame 9, 10, 12 [large MTU therefore fits in so few packets]).

But not sure how to further interpret this and whether it’s correct what’s being sent.

I tried recompiling simple_switch_grpc with -ggdb and -O0, with ulimit -c unlimited and analyze the coredump in GDB, but getting some weird errors like:

warning: core file may not match specified executable file.
warning: Section .reg-xstate/1058446 in core file too small.
of course nothing in the backtrace after that

while I’m sure the binary executable is the same while running vs what’s passed to GDB.

I think I will try to:

use another tool to interface with the simple_switch_grpc to see if that works (i believe there is some python/shell thing that uses grpc?)
try to lookup more examples to see how the SetForwardingPipelineConfig() is being used…

Hope someone has a hint, thanks

leonderooij · December 17, 2023, 9:43am

Alright! I was just experimenting a bit, and I can prevent the segfault if I do VERIFY_AND_COMMIT instead of RECONCILE_AND_COMMIT !!!

When doing the insert I don’t get the No forwarding pipeline config set for this device error anymore… Just an empty error: Failed to insert table entry: … anyway progress

– ah the simple_switch_grpc logs [P4Runtime] Invalid P4 id

leonderooij · December 17, 2023, 10:15pm

last bits with Invalid P4 id also fixed I now have a functional p4runtime_client

Topic		Replies	Views
P4Runtime-shell with proactive and reactive approach	13	1165	October 14, 2021
Connection error in using P4runtime	0	308	July 18, 2023
Need help with digest p4runtime Getting Started with P4	3	1471	June 12, 2022
Running simple_switch_grpc? Getting Started with P4	4	541	January 11, 2023
Problems encountered with p4runtime Getting Started with P4	11	634	March 12, 2023

[resolved] P4runtime: No forwarding pipeline config or SEGFAULT

Related Topics