Merge pull request #3761 from telepresenceio/thallgren/drop-replaced

Remove the dormant container during intercept with --replace.

Author: thallgren

CHANGELOG.yml

@@ -44,6 +44,16 @@ items:
                values: <namespaces>`.
           ```
         docs: install/manager#static-versus-dynamic-namespace-selection
+      - type: feature
+        title: Removal of the dormant container during intercept with --replace.
+        body: |-
+          During a `telepresence intercept --replace operation`, the previously injected dormant container has been
+          removed. The Traffic Agent now directly serves as the replacement container, eliminating the need to forward
+          traffic to the original application container. This simplification offers several advantages when using the
+          `--replace` flag:
+          
+          - **Removal of the init-container:** The need for a separate init-container is no longer necessary.
+          - **Elimination of port renames:** Port renames within the intercepted pod are no longer required.
       - type: change
         title: Drop deprecated current-cluster-id command.
         body: >-

cmd/traffic/cmd/agent/agent.go

@@ -95,11 +95,11 @@ func sftpServer(ctx context.Context, sftpPortCh chan<- uint16) error {
 		_ = l.Close()
 	}()
 
-	_, sftpPort, err := iputil.SplitToIPPort(l.Addr())
+	ap, err := iputil.SplitToIPPort(l.Addr())
 	if err != nil {
 		return err
 	}
-	sftpPortCh <- sftpPort
+	sftpPortCh <- ap.Port()
 
 	dlog.Infof(ctx, "Listening at: %s", l.Addr())
 	for {
@@ -163,31 +163,38 @@ func sidecar(ctx context.Context, s State, info *rpc.AgentInfo) error {
 		// Group the container's intercepts by agent port
 		icStates := make(map[agentconfig.PortAndProto][]*agentconfig.Intercept, len(cn.Intercepts))
 		for _, ic := range cn.Intercepts {
-			k := agentconfig.PortAndProto{Port: ic.AgentPort, Proto: ic.Protocol}
+			ap := ic.AgentPort
+			if cn.Replace {
+				// Listen to replaced container's original port.
+				ap = ic.ContainerPort
+			}
+			k := agentconfig.PortAndProto{Port: ap, Proto: ic.Protocol}
 			icStates[k] = append(icStates[k], ic)
 		}
 
 		for pp, ics := range icStates {
 			ic := ics[0] // They all have the same protocol container port, so the first one will do.
+			var fwd forwarder.Interceptor
 			var cp uint16
-			if ic.TargetPortNumeric {
-				// We must differentiate between connections originating from the agent's forwarder to the container
-				// port and those from other sources. The former should not be routed back, while the latter should
-				// always be routed to the agent. We do this by using a proxy port that will be recognized by the
-				// iptables filtering in our init-container.
-				cp = ac.ProxyPort(ic)
+			if !cn.Replace {
+				if ic.TargetPortNumeric {
+					// We must differentiate between connections originating from the agent's forwarder to the container
+					// port and those from other sources. The former should not be routed back, while the latter should
+					// always be routed to the agent. We do this by using a proxy port that will be recognized by the
+					// iptables filtering in our init-container.
+					cp = ac.ProxyPort(ic)
+				} else {
+					cp = ic.ContainerPort
+				}
+				// Redirect non-intercepted traffic to the pod, so that injected sidecars that hijack the ports for
+				// incoming connections will continue to work.
+				targetHost := s.PodIP()
+				fwd = forwarder.NewInterceptor(pp, targetHost, cp)
 			} else {
+				fwd = forwarder.NewInterceptor(pp, "", 0)
 				cp = ic.ContainerPort
 			}
-			lisAddr, err := pp.Addr()
-			if err != nil {
-				return err
-			}
-			// Redirect non-intercepted traffic to the pod, so that injected sidecars that hijack the ports for
-			// incoming connections will continue to work.
-			targetHost := s.PodIP()
 
-			fwd := forwarder.NewInterceptor(lisAddr, targetHost, cp)
 			dgroup.ParentGroup(ctx).Go(fmt.Sprintf("forward-%s", iputil.JoinHostPort(cn.Name, cp)), func(ctx context.Context) error {
 				return fwd.Serve(tunnel.WithPool(ctx, tunnel.NewPool()), nil)
 			})

cmd/traffic/cmd/agent/server.go

@@ -118,7 +118,7 @@ func (s *state) ReportMetrics(ctx context.Context, metrics *rpc.TunnelMetrics) {
 		mCtx, mCancel := context.WithTimeout(context.WithoutCancel(ctx), time.Second)
 		defer mCancel()
 		_, err := s.manager.ReportMetrics(mCtx, metrics)
-		if err != nil {
+		if err != nil && status.Code(err) != codes.Canceled {
 			dlog.Errorf(ctx, "ReportMetrics failed: %v", err)
 		}
 	}()

cmd/traffic/cmd/agent/state_test.go

@@ -2,13 +2,13 @@ package agent_test
 
 import (
 	"context"
-	"net"
 	"path/filepath"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	core "k8s.io/api/core/v1"
 
 	"github.com/datawire/dlib/dlog"
 	rpc "github.com/telepresenceio/telepresence/rpc/v2/manager"
@@ -23,10 +23,7 @@ const (
 )
 
 func makeFS(t *testing.T, ctx context.Context) (forwarder.Interceptor, agent.State) {
-	lAddr, err := net.ResolveTCPAddr("tcp", ":1111")
-	assert.NoError(t, err)
-
-	f := forwarder.NewInterceptor(lAddr, appHost, appPort)
+	f := forwarder.NewInterceptor(agentconfig.PortAndProto{Proto: core.ProtocolTCP, Port: 1111}, appHost, appPort)
 	go func() {
 		if err := f.Serve(context.Background(), nil); err != nil {
 			dlog.Error(ctx, err)

cmd/traffic/cmd/agentinit/agent_init.go

@@ -7,6 +7,7 @@ import (
 	"context"
 	"fmt"
 	"net"
+	"net/netip"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -19,7 +20,6 @@ import (
 	"github.com/datawire/dlib/dlog"
 	"github.com/telepresenceio/telepresence/v2/pkg/agentconfig"
 	"github.com/telepresenceio/telepresence/v2/pkg/dos"
-	"github.com/telepresenceio/telepresence/v2/pkg/iputil"
 	"github.com/telepresenceio/telepresence/v2/pkg/version"
 )
 
@@ -45,7 +45,7 @@ func loadConfig(ctx context.Context) (*config, error) {
 	return &c, nil
 }
 
-func (c *config) configureIptables(ctx context.Context, iptables *iptables.IPTables, loopback, localHostCIDR, podIP string) error {
+func (c *config) configureIptables(ctx context.Context, iptables *iptables.IPTables, loopback string, localHostCIDR netip.Prefix, podIP netip.Addr) error {
 	// These iptables rules implement routing such that a packet directed to the appPort will hit the agentPort instead.
 	// If there's no mesh this is simply request -> agent -> app (or intercept)
 	// However, if there's a service mesh we want to make sure we don't bypass the mesh, so the traffic
@@ -114,8 +114,8 @@ func (c *config) configureIptables(ctx context.Context, iptables *iptables.IPTab
 						// loop it back into the agent.
 						dlog.Debugf(ctx, "output DNAT %s:%d -> %s:%d", podIP, ac.ProxyPort(ic), podIP, ic.ContainerPort)
 						err = iptables.AppendUnique(nat, outputChain,
-							"-p", lcProto, "-d", podIP, "--dport", strconv.Itoa(int(ac.ProxyPort(ic))),
-							"-j", "DNAT", "--to-destination", net.JoinHostPort(podIP, strconv.Itoa(int(ic.ContainerPort))))
+							"-p", lcProto, "-d", podIP.String(), "--dport", strconv.Itoa(int(ac.ProxyPort(ic))),
+							"-j", "DNAT", "--to-destination", netip.AddrPortFrom(podIP, ic.ContainerPort).String())
 						if err != nil {
 							return fmt.Errorf("failed to append rule to %s: %w", outputChain, err)
 						}
@@ -155,7 +155,7 @@ func (c *config) configureIptables(ctx context.Context, iptables *iptables.IPTab
 		err = iptables.Insert(nat, "OUTPUT", 1,
 			"-o", loopback,
 			"-p", lcProto,
-			"!", "-d", localHostCIDR,
+			"!", "-d", localHostCIDR.String(),
 			"-m", "owner", "--uid-owner", agentUID,
 			"-j", outputChain)
 		if err != nil {
@@ -213,11 +213,15 @@ func Main(ctx context.Context, args ...string) error {
 		return err
 	}
 	proto := iptables.ProtocolIPv4
-	localhostCIDR := "127.0.0.1/32"
-	podIP := os.Getenv("POD_IP")
-	if len(iputil.Parse(podIP)) == 16 {
+	localhostCIDR := netip.PrefixFrom(netip.AddrFrom4([4]byte{127, 0, 0, 1}), 32)
+	podIP, err := netip.ParseAddr(os.Getenv("POD_IP"))
+	if err != nil {
+		dlog.Error(ctx, err)
+		return err
+	}
+	if podIP.Is6() {
 		proto = iptables.ProtocolIPv6
-		localhostCIDR = "::1/128"
+		localhostCIDR = netip.PrefixFrom(netip.IPv6Loopback(), 128)
 	}
 	it, err := iptables.NewWithProtocol(proto)
 	if err != nil {

cmd/traffic/cmd/manager/cluster/info.go

@@ -348,7 +348,11 @@ func getInjectorSvcIP(ctx context.Context, env *managerutil.Env, client v1.CoreV
 			break
 		}
 	}
-	return iputil.Parse(sc.Spec.ClusterIP), p, nil
+	ip, err := netip.ParseAddr(sc.Spec.ClusterIP)
+	if err != nil {
+		return nil, 0, err
+	}
+	return ip.AsSlice(), p, nil
 }
 
 func (oi *info) watchPodSubnets(ctx context.Context) {