Adding update config for ISIS link metric

[SuryyaKrJana]

Feature Overview

• Related Issue: FR to be able to change the ISIS SIM router properties on the fly. [433281254] - Issue Tracker
• Brief Description:
  Tart is to change of ISIS Link Metric on the Fly only however added other attributes and BGP OTF to oversee over design.

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Feature Details

• Redocly docs for this feature/branch

• New Locations/Nomenclature:
  update_config: UpdateProtocol.Config.Isis.Link

• Dev-Snappi branch reference

• Example command to fetch the dev-snappi branch:

  go get github.com/open-traffic-generator/snappi/gosnappi@<isis-otf-on-link-metric>
  

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Code snippets

•     ISIS OTF: both interface metrics 10 → 50 (LSP re-advertisement, no session flap)
  

•     BGP OTF: both peer hold times 90 → 120 (router-level attribute update)
  

•     Flow rate OTF via UpdateConfig (Existing feature already available): both flows 100 → 200 pps using FlowsUpdate with property RATE
  

      // Changes p1d1IsisIntf metric from 10 → 50 and p2d1IsisIntf from 10 → 50.
       isisUpdate := gosnappi.NewUpdateProtocolConfigIsis()

	p1IfUpdate := gosnappi.NewUpdateProtocolConfigIsisInterfaceUpdateGroup()
	p1IfUpdate.SetNames([]string{"p1d1IsisIntf"})
	p1IfUpdate.SetMetric(uint32(50))
	isisUpdate.Interfaces().Append(p1IfUpdate)

	p2IfUpdate := gosnappi.NewUpdateProtocolConfigIsisInterfaceUpdateGroup()
	p2IfUpdate.SetNames([]string{"p2d1IsisIntf"})
	p2IfUpdate.SetMetric(uint32(50))
	isisUpdate.Interfaces().Append(p2IfUpdate)

        // BGP OTF: both peer hold times 90 → 120 (router-level attribute update)
	bgpUpdate := gosnappi.NewUpdateProtocolConfigBgp()
	p1BgpRouterUpdate := gosnappi.NewUpdateProtocolConfigBgpRouterUpdateGroup()
	p1BgpRouterUpdate.SetNames([]string{"p1d1BgpPeer"})
	p1BgpRouterUpdate.SetHoldTime(uint32(120))
	bgpUpdate.Routers().Append(p1BgpRouterUpdate)

	p2BgpRouterUpdate := gosnappi.NewUpdateProtocolConfigBgpRouterUpdateGroup()
	p2BgpRouterUpdate.SetNames([]string{"p2d1BgpPeer"})
	p2BgpRouterUpdate.SetHoldTime(uint32(120))
	bgpUpdate.Routers().Append(p2BgpRouterUpdate)

	pu := gosnappi.NewProtocolsUpdate()
	pu.SetIsis(isisUpdate)
	pu.SetBgp(bgpUpdate)

	cu := gosnappi.NewConfigUpdate()
	cu.SetProtocols(pu)

	if _, err := client.UpdateConfig(cu); err != nil {
		t.Fatal(err)
	}


	// Changes flow rate from 100 pps → 200 pps on both flows.
	
	getCfg, err := client.GetConfig()
	if err != nil {
		t.Fatal(err)
	}

	fu := gosnappi.NewConfigUpdate().Flows()
	for _, flow := range getCfg.Flows().Items() {
		flow.Rate().SetPps(200)
		fu.Flows().Append(flow)
	}
	fu.SetPropertyNames([]gosnappi.FlowsUpdatePropertyNamesEnum{
		gosnappi.FlowsUpdatePropertyNames.RATE,
	})

	flowCu := gosnappi.NewConfigUpdate()
	flowCu.SetFlows(fu)
	if _, err := client.UpdateConfig(flowCu); err != nil {
		t.Fatal(err)
	}
	
	if err := client.StartTransmit(nil); err != nil {
		t.Fatal(err)
	}