Add a telepresence wiretap command.

CHANGELOG.yml

@@ -24,6 +24,18 @@
 #
 # For older changes, see CHANGELOG.OLD.md
 items:
+  - version: 2.23.0
+    date: (TBD)
+    notes:
+      - type: feature
+        title: New telepresence wiretap command
+        body: >-
+          The new `telepresence wiretap` command introduces a read-only form of an `intercept` where the original
+          container will run unaffected while a copy of the wiretapped traffic is sent to the client.
+
+          Similar to an `ingest`, a `wiretap` will always enforce read-only status on all volume mounts, and since that
+          makes the `wiretap` completely read-only, there's no limit to how many simultaneous wiretaps that can be
+          served. In fact, a `wiretap` and an `intercept` on the same port can run simultaneously.
   - version: 2.22.1
     date: (TBD)
     notes:

cmd/traffic/cmd/agent/fwdstate.go

@@ -4,21 +4,23 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"slices"
 	"time"
 
 	"github.com/datawire/dlib/dlog"
 	"github.com/telepresenceio/telepresence/rpc/v2/manager"
 	"github.com/telepresenceio/telepresence/v2/pkg/forwarder"
+	"github.com/telepresenceio/telepresence/v2/pkg/iputil"
 	"github.com/telepresenceio/telepresence/v2/pkg/restapi"
 	"github.com/telepresenceio/telepresence/v2/pkg/tunnel"
 )
 
 type fwdState struct {
 	*state
-	intercept       InterceptTarget
-	container       string
-	forwarder       forwarder.Interceptor
-	chosenIntercept *manager.InterceptInfo
+	intercept         InterceptTarget
+	container         string
+	forwarder         forwarder.Interceptor
+	chosenInterceptId string
 }
 
 // NewInterceptState creates an InterceptState that performs intercepts by using an Interceptor which indiscriminately
@@ -73,118 +75,122 @@ func (pm *ProviderMux) CreateClientStream(ctx context.Context, tag tunnel.Tag, s
 }
 
 func (fs *fwdState) HandleIntercepts(ctx context.Context, cepts []*manager.InterceptInfo) []*manager.ReviewInterceptRequest {
-	var myChoice, activeIntercept *manager.InterceptInfo
-	if fs.chosenIntercept != nil {
-		chosenID := fs.chosenIntercept.Id
-		for _, is := range cepts {
-			if chosenID == is.Id {
-				fs.chosenIntercept = is
-				myChoice = is
+	var active []*manager.InterceptInfo
+	var waiting []*manager.InterceptInfo
+	for _, is := range cepts {
+		switch is.Disposition {
+		case manager.InterceptDispositionType_ACTIVE:
+			active = append(active, is)
+		case manager.InterceptDispositionType_WAITING:
+			waiting = append(waiting, is)
+		}
+	}
+
+	var activeIntercept *manager.InterceptInfo
+	if fs.chosenInterceptId != "" {
+		for _, is := range active {
+			if fs.chosenInterceptId == is.Id {
+				if !is.Spec.Wiretap {
+					activeIntercept = is
+				}
 				break
 			}
 		}
+	}
+
+	if activeIntercept == nil {
+		fs.chosenInterceptId = ""
 
-		if myChoice == nil {
-			// Chosen intercept is not present in the snapshot
-			fs.chosenIntercept = nil
-		} else if myChoice.Disposition == manager.InterceptDispositionType_ACTIVE {
-			// The chosen intercept still exists and is active
-			activeIntercept = myChoice
-		}
-	} else {
 		// Attach to already ACTIVE intercept if there is one.
-		for _, cept := range cepts {
-			if cept.Disposition == manager.InterceptDispositionType_ACTIVE {
-				myChoice = cept
-				fs.chosenIntercept = cept
-				activeIntercept = cept
+		for _, is := range active {
+			if !is.Spec.Wiretap {
+				fs.chosenInterceptId = is.Id
+				activeIntercept = is
 				break
 			}
 		}
 	}
 
+	fwd := fs.forwarder
 	if fs.sessionInfo != nil {
 		// Update forwarding.
-		fs.forwarder.SetStreamProvider(
+		fwd.SetStreamProvider(
 			&ProviderMux{
 				AgentProvider:   fs,
 				ManagerProvider: &tunnel.TrafficManagerStreamProvider{Manager: fs.ManagerClient(), AgentSessionID: tunnel.SessionID(fs.sessionInfo.SessionId)},
 			})
 	}
-	fs.forwarder.SetIntercepting(activeIntercept)
+	fwd.SetIntercepting(activeIntercept)
 
-	// Review waiting intercepts
-	reviews := make([]*manager.ReviewInterceptRequest, 0, len(cepts))
-	for _, cept := range cepts {
-		container := cept.Spec.ContainerName
-		if container == "" {
-			container = fs.container
+	// Remove inactive wiretaps.
+	for _, id := range fwd.WiretapIDs() {
+		if !slices.ContainsFunc(active, func(ii *manager.InterceptInfo) bool { return ii.Id == id && ii.Spec.Wiretap }) {
+			dlog.Debugf(ctx, "removing wiretap id %s", id)
+			fwd.RemoveWiretap(id)
 		}
-		cs := fs.containerStates[container]
-		if cs == nil {
-			reviews = append(reviews, &manager.ReviewInterceptRequest{
-				Id:                cept.Id,
-				Disposition:       manager.InterceptDispositionType_AGENT_ERROR,
-				Message:           fmt.Sprintf("No match for container %q", container),
-				MechanismArgsDesc: "all TCP connections",
-			})
-			continue
+	}
+
+	// Add active wiretaps.
+	for _, ii := range active {
+		if ii.Spec.Wiretap {
+			if !fwd.HasWiretap(ii.Id) {
+				dlog.Debugf(ctx, "adding wiretap id %s to %s", ii.Id, iputil.JoinHostPort(ii.Spec.TargetHost, uint16(ii.Spec.TargetPort)))
+				fwd.AddWiretap(ii)
+			}
 		}
-		if cept.Disposition == manager.InterceptDispositionType_WAITING {
+	}
+
+	// Review waiting intercepts
+	reviews := make([]*manager.ReviewInterceptRequest, 0, len(waiting))
+	for _, ii := range waiting {
+		switch {
+		case activeIntercept == nil || ii.Spec.Wiretap:
 			// This intercept is ready to be active
-			switch {
-			case cept == myChoice:
-				// We've already chosen this one, but it's not active yet in this
-				// snapshot. Let's go ahead and tell the manager to mark it ACTIVE.
-				dlog.Infof(ctx, "Setting intercept %q as ACTIVE (again?)", cept.Id)
-				reviews = append(reviews, &manager.ReviewInterceptRequest{
-					Id:                cept.Id,
-					Disposition:       manager.InterceptDispositionType_ACTIVE,
-					PodIp:             fs.PodIP(),
-					FtpPort:           int32(fs.FtpPort()),
-					SftpPort:          int32(fs.SftpPort()),
-					MountPoint:        cs.MountPoint(),
-					Mounts:            cs.Mounts().ToRPC(),
-					MechanismArgsDesc: "all TCP connections",
-					Environment:       cs.Env(),
-				})
-			case fs.chosenIntercept == nil:
-				// We don't have an intercept in play, so choose this one. All
-				// agents will get intercepts in the same order every time, so
-				// this will yield a consistent result. Note that the intercept
-				// will not become active at this time. That will happen later,
-				// once the manager assigns a port.
-				dlog.Infof(ctx, "Setting intercept %q as ACTIVE", cept.Id)
-				fs.chosenIntercept = cept
-				myChoice = cept
-				reviews = append(reviews, &manager.ReviewInterceptRequest{
-					Id:                cept.Id,
-					Disposition:       manager.InterceptDispositionType_ACTIVE,
-					PodIp:             fs.PodIP(),
-					FtpPort:           int32(fs.FtpPort()),
-					SftpPort:          int32(fs.SftpPort()),
-					MountPoint:        cs.MountPoint(),
-					Mounts:            cs.Mounts().ToRPC(),
-					MechanismArgsDesc: "all TCP connections",
-					Environment:       cs.Env(),
-				})
-			default:
-				// We already have an intercept in play, so reject this one.
-				chosenID := fs.chosenIntercept.Id
-				dlog.Infof(ctx, "Setting intercept %q as AGENT_ERROR; as it conflicts with %q as the current chosen-to-be-ACTIVE intercept", cept.Id, chosenID)
-				var msg string
-				if fs.chosenIntercept.Disposition == manager.InterceptDispositionType_ACTIVE {
-					msg = fmt.Sprintf("Conflicts with the currently-served intercept %q", chosenID)
-				} else {
-					msg = fmt.Sprintf("Conflicts with the currently-waiting-to-be-served intercept %q", chosenID)
-				}
+			container := ii.Spec.ContainerName
+			if container == "" {
+				container = fs.container
+			}
+			cs := fs.containerStates[container]
+			if cs == nil {
 				reviews = append(reviews, &manager.ReviewInterceptRequest{
-					Id:                cept.Id,
+					Id:                ii.Id,
 					Disposition:       manager.InterceptDispositionType_AGENT_ERROR,
-					Message:           msg,
+					Message:           fmt.Sprintf("No match for container %q", container),
 					MechanismArgsDesc: "all TCP connections",
 				})
+				continue
+			}
+			if !ii.Spec.Wiretap {
+				// We can only have one active intercept that isn't a wiretap
+				activeIntercept = ii
 			}
+			reviews = append(reviews, &manager.ReviewInterceptRequest{
+				Id:                ii.Id,
+				Disposition:       manager.InterceptDispositionType_ACTIVE,
+				PodIp:             fs.PodIP(),
+				FtpPort:           int32(fs.FtpPort()),
+				SftpPort:          int32(fs.SftpPort()),
+				MountPoint:        cs.MountPoint(),
+				Mounts:            cs.Mounts().ToRPC(),
+				MechanismArgsDesc: "all TCP connections",
+				Environment:       cs.Env(),
+			})
+		default:
+			// We already have an intercept in play, so reject this one.
+			chosenID := activeIntercept.Id
+			dlog.Infof(ctx, "Setting intercept %q as AGENT_ERROR; as it conflicts with %q as the current chosen-to-be-ACTIVE intercept", ii.Id, chosenID)
+			var msg string
+			if activeIntercept.Disposition == manager.InterceptDispositionType_ACTIVE {
+				msg = fmt.Sprintf("Conflicts with the currently-served intercept %q", chosenID)
+			} else {
+				msg = fmt.Sprintf("Conflicts with the currently-waiting-to-be-served intercept %q", chosenID)
+			}
+			reviews = append(reviews, &manager.ReviewInterceptRequest{
+				Id:                ii.Id,
+				Disposition:       manager.InterceptDispositionType_AGENT_ERROR,
+				Message:           msg,
+				MechanismArgsDesc: "all TCP connections",
+			})
 		}
 	}
 	return reviews

cmd/traffic/cmd/manager/state/intercept.go

@@ -208,10 +208,14 @@ func (s *state) preparePorts(ac *agentconfig.Sidecar, cn *agentconfig.Container,
 		return info.Disposition == rpc.InterceptDispositionType_ACTIVE && info.Spec.Agent == ac.AgentName && info.Spec.Namespace == ac.Namespace
 	})
 
-	if spec.Mechanism != "http" {
+	if !(spec.Wiretap || spec.Mechanism == "http") {
 		// Intercept is global, so it will conflict with any other intercept using the same port and protocol.
 		for _, otherIc := range otherIcs {
 			oSpec := otherIc.Spec // Validate that there's no port conflict
+			if oSpec.Wiretap {
+				// wiretaps will not cause conflicts
+				continue
+			}
 			for cp := range uniqueContainerPorts {
 				if cp.Port == uint16(oSpec.ContainerPort) && string(cp.Proto) == oSpec.Protocol {
 					name := oSpec.Name

docs/compare/mirrord.md

@@ -51,9 +51,9 @@ This comparison chart applies to the Open Source editions of both products.
 | Doesn't require injection of a sidecar                                     | ✅ [^3]       | ✅       |
 | Supports connecting to clusters over a corporate VPN                       | ✅            | ✅       |
 | Can intercept traffic                                                      | ✅            | ✅       |
+| Can mirror traffic                                                         | ✅            | ✅       |
 | Can ingest a container                                                     | ✅            | ❌       |
 | Can replace a container                                                    | ✅            | ❌       |
-| Can mirror traffic                                                         | ❌            | ✅       |
 | Can act as a cluster VPN only                                              | ✅            | ❌       |
 | Will work with statically linked binaries                                  | ✅            | ❌       |
 | Runs natively on windows                                                   | ✅            | ❌       |

docs/howtos/engage.md

@@ -38,6 +38,24 @@ Telepresence offers three powerful ways to develop your services locally:
   - You want your local service to only receive specific ingress traffic, while other traffic must be untouched.
   - You want your remote container to continue processing other requests or background tasks.
 
+### Wiretap
+* **How it Works:**
+  - Adds a wiretap on a specific service port (or ports) and sends the data to the local workstation.
+  - Makes the remote environment of the targeted container available to the local workstation.
+  - Provides read-only access to the volumes mounted by the targeted container.
+* **Impact:**
+  - A Traffic Agent is injected into the pods of the targeted workload.
+  - All containers keep on running.
+  - All traffic will still reach the remote service.
+  - Wiretapped traffic is rerouted to the local workstation.
+* **Use-cases:**
+  - You need a solution where several developers can engage with the same service simultaneously.
+  - Your main focus is the service API rather than the cluster's pods and containers.
+  - You want your local service to only receive specific ingress traffic.
+  - You don't care about the responses sent by your local service.
+  - You don't want breakpoints in your local service to affect the remote service.
+  - You want to keep the impact that your local development has on the cluster to a minimum.
+
 ### Ingest
 * **How it Works:**
    - Makes the remote environment of the ingested container available to the local workstation.
@@ -46,7 +64,7 @@ Telepresence offers three powerful ways to develop your services locally:
    - A Traffic Agent is injected into the pods of the targeted workload.
    - No traffic is rerouted and all containers keep on running.
 * **Use-cases:**
-   - You want to keep the impact of your local development to a minimum.
+   - You want to keep the impact that your local development has on the cluster to a minimum.
    - You have don't need traffic being routed from the cluster, and read-only access to the container's volumes is ok.
 
 ## Prerequisites
@@ -199,6 +217,41 @@ You can now:
 - Query services only exposed in your cluster's network.
 - Set breakpoints in your IDE to investigate bugs.
 
+## Wiretap your application
+
+You can use the `telepresence wiretap` command when you want to wiretap the traffic for a specific service and send a
+copy of it to your workstation. The `wiretap` is less intrusive than the `intercept`, because it does not interfere
+with the traffic at all.
+
+1. Connect to your cluster with `telepresence connect`.
+
+2. Put a wiretap on all traffic going to the application's http port in your cluster and send it to port 8080 on your workstation.
+    ```console
+    $ telepresence wiretap example-app --port 8080:http --env-file ~/example-app-intercept.env --mount /tmp/example-app-mounts
+    Using Deployment example-app
+    wiretapped
+      Wiretap name  : example-app
+      State         : ACTIVE
+      Workload kind : Deployment
+      Destination   : 127.0.0.1:8080
+      Intercepting  : all TCP connections
+    ```
+
+    * For `--port`: specify the port the local instance of your application is running on, and optionally the remote port
+      that you want to wiretap. Telepresence will select the remote port automatically when there's only one service
+      port available to access the workload. You must specify the port to wiretap when the workload exposes multiple
+      ports. You can do this by specifying the port you want to wiretap after a colon in the `--port` argument (like in
+      the example), and/or by specifying the service you want to wiretap using the `--service` flag.
+
+    * For `--env-file`: specify a file path for Telepresence to write the environment variables that are set for the targeted
+      container.
+
+3. Start your local application using the environment variables retrieved and the volumes that were mounted in the previous step.
+
+You can now:
+- Query services only exposed in your cluster's network.
+- Set breakpoints in your IDE to investigate bugs.
+
 ### Running everything using Docker
 
 This approach eliminates the need for root access and confines the Telepresence network interface and remote mounts

docs/reference/architecture.md

@@ -36,11 +36,13 @@ in the telepresence client binary (`telepresence helm install`) or by using a He
 
 ## Traffic Agent
 
-The Traffic Agent is a sidecar container that facilitates engagements. When a `replace`, `ingest` or `intercept` is first
+The Traffic Agent is a sidecar container that facilitates engagements. When a `replace`, `ingest`, `intercept`, or `wiretap` is first
 started, the Traffic Agent container is injected into the workload's pod(s). You can see the Traffic Agent's status by
 running `telepresence list` or `kubectl describe pod <pod-name>`.
 
 Depending on if an `replace` or `intercept` is active or not, the Traffic Agent will either route the incoming request 
 to your workstation, or it will pass it along to the container in the pod usually handling requests.
 
+When a `wiretap` is active, the Traffic Agent will send a copy of the incoming requests to your workstation.
+
 Please see [Traffic Agent Sidecar](engagements/sidecar.md) for details.