core -> metropolis

Smalltown is now called Metropolis!

This is the first commit in a series of cleanup commits that prepare us
for an open source release. This one just some Bazel packages around to
follow a stricter directory layout.

All of Metropolis now lives in `//metropolis`.

All of Metropolis Node code now lives in `//metropolis/node`.

All of the main /init now lives in `//m/n/core`.

All of the Kubernetes functionality/glue now lives in `//m/n/kubernetes`.

Next steps:
     - hunt down all references to Smalltown and replace them appropriately
     - narrow down visibility rules
     - document new code organization
     - move `//build/toolchain` to `//monogon/build/toolchain`
     - do another cleanup pass between `//golibs` and
       `//monogon/node/{core,common}`.
     - remove `//delta` and `//anubis`

Fixes T799.

Test Plan: Just a very large refactor. CI should help us out here.

Bug: T799

X-Origin-Diff: phab/D667
GitOrigin-RevId: 6029b8d4edc42325d50042596b639e8b122d0ded
diff --git a/metropolis/node/core/main.go b/metropolis/node/core/main.go
new file mode 100644
index 0000000..54d09a4
--- /dev/null
+++ b/metropolis/node/core/main.go
@@ -0,0 +1,321 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"context"
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/x509"
+	"fmt"
+	"log"
+	"math/big"
+	"net"
+	"os"
+	"os/signal"
+	"runtime/debug"
+
+	"golang.org/x/sys/unix"
+	"google.golang.org/grpc"
+
+	common "git.monogon.dev/source/nexantic.git/metropolis/node"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/common/supervisor"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/core/cluster"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/core/localstorage"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/core/localstorage/declarative"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/core/logtree"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/core/network"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/core/network/dns"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/core/tpm"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/kubernetes"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/kubernetes/containerd"
+	"git.monogon.dev/source/nexantic.git/metropolis/node/kubernetes/pki"
+	apb "git.monogon.dev/source/nexantic.git/metropolis/proto/api"
+)
+
+var (
+	// kubernetesConfig is the static/global part of the Kubernetes service configuration. In the future, this might
+	// be configurable by loading it from the EnrolmentConfig. Fow now, it's static and same across all clusters.
+	kubernetesConfig = kubernetes.Config{
+		ServiceIPRange: net.IPNet{ // TODO(q3k): Decide if configurable / final value
+			IP:   net.IP{10, 0, 255, 1},
+			Mask: net.IPMask{0xff, 0xff, 0xff, 0x00}, // /24, but Go stores as a literal mask
+		},
+		ClusterNet: net.IPNet{
+			IP:   net.IP{10, 0, 0, 0},
+			Mask: net.IPMask{0xff, 0xff, 0x00, 0x00}, // /16
+		},
+	}
+)
+
+func main() {
+	defer func() {
+		if r := recover(); r != nil {
+			fmt.Println("Init panicked:", r)
+			debug.PrintStack()
+		}
+		unix.Sync()
+		// TODO(lorenz): Switch this to Reboot when init panics are less likely
+		// Best effort, nothing we can do if this fails except printing the error to the console.
+		if err := unix.Reboot(unix.LINUX_REBOOT_CMD_POWER_OFF); err != nil {
+			panic(fmt.Sprintf("failed to halt node: %v\n", err))
+		}
+	}()
+
+	// Set up logger for Smalltown. Currently logs everything to stderr.
+	lt := logtree.New()
+	reader, err := lt.Read("", logtree.WithChildren(), logtree.WithStream())
+	if err != nil {
+		panic(fmt.Errorf("could not set up root log reader: %v", err))
+	}
+	go func() {
+		for {
+			p := <-reader.Stream
+			fmt.Fprintf(os.Stderr, "%s\n", p.String())
+		}
+	}()
+
+	// Initial logger. Used until we get to a supervisor.
+	logger := lt.MustLeveledFor("init")
+
+	// Remount onto a tmpfs and re-exec if needed. Otherwise, keep running.
+	err = switchRoot(logger)
+	if err != nil {
+		panic(fmt.Errorf("could not remount root: %w", err))
+	}
+
+	// Linux kernel default is 4096 which is far too low. Raise it to 1M which is what gVisor suggests.
+	if err := unix.Setrlimit(unix.RLIMIT_NOFILE, &unix.Rlimit{Cur: 1048576, Max: 1048576}); err != nil {
+		logger.Fatalf("Failed to raise rlimits: %v", err)
+	}
+
+	logger.Info("Starting Smalltown Init")
+
+	signalChannel := make(chan os.Signal, 2)
+	signal.Notify(signalChannel)
+
+	if err := tpm.Initialize(logger); err != nil {
+		logger.Fatalf("Failed to initialize TPM 2.0: %v", err)
+	}
+
+	corednsRegistrationChan := make(chan *dns.ExtraDirective)
+
+	networkSvc := network.New(network.Config{CorednsRegistrationChan: corednsRegistrationChan})
+
+	// This function initializes a headless Delve if this is a debug build or does nothing if it's not
+	initializeDebugger(networkSvc)
+
+	// Prepare local storage.
+	root := &localstorage.Root{}
+	if err := declarative.PlaceFS(root, "/"); err != nil {
+		panic(fmt.Errorf("when placing root FS: %w", err))
+	}
+
+	// trapdoor is a channel used to signal to the init service that a very low-level, unrecoverable failure
+	// occured. This causes a GURU MEDITATION ERROR visible to the end user.
+	trapdoor := make(chan struct{})
+
+	// Make context for supervisor. We cancel it when we reach the trapdoor.
+	ctxS, ctxC := context.WithCancel(context.Background())
+
+	// Start root initialization code as a supervisor one-shot runnable. This means waiting for the network, starting
+	// the cluster manager, and then starting all services related to the node's roles.
+	// TODO(q3k): move this to a separate 'init' service.
+	supervisor.New(ctxS, func(ctx context.Context) error {
+		logger := supervisor.Logger(ctx)
+
+		// Start storage and network - we need this to get anything else done.
+		if err := root.Start(ctx); err != nil {
+			return fmt.Errorf("cannot start root FS: %w", err)
+		}
+		if err := supervisor.Run(ctx, "network", networkSvc.Run); err != nil {
+			return fmt.Errorf("when starting network: %w", err)
+		}
+
+		// Wait for IP address from network.
+		ip, err := networkSvc.GetIP(ctx, true)
+		if err != nil {
+			return fmt.Errorf("when waiting for IP address: %w", err)
+		}
+
+		// Start cluster manager. This kicks off cluster membership machinery, which will either start
+		// a new cluster, enroll into one or join one.
+		m := cluster.NewManager(root, networkSvc)
+		if err := supervisor.Run(ctx, "enrolment", m.Run); err != nil {
+			return fmt.Errorf("when starting enrolment: %w", err)
+		}
+
+		// Wait until the cluster manager settles.
+		success := m.WaitFinished()
+		if !success {
+			close(trapdoor)
+			return fmt.Errorf("enrolment failed, aborting")
+		}
+
+		// We are now in a cluster. We can thus access our 'node' object and start all services that
+		// we should be running.
+
+		node := m.Node()
+		if err := node.ConfigureLocalHostname(&root.Etc); err != nil {
+			close(trapdoor)
+			return fmt.Errorf("failed to set local hostname: %w", err)
+		}
+
+		logger.Info("Enrolment success, continuing startup.")
+		logger.Info(fmt.Sprintf("This node (%s) has roles:", node.String()))
+		if cm := node.ConsensusMember(); cm != nil {
+			// There's no need to start anything for when we are a consensus member - the cluster
+			// manager does this for us if necessary (as creating/enrolling/joining a cluster is
+			// pretty tied into cluster lifecycle management).
+			logger.Info(fmt.Sprintf(" - etcd consensus member"))
+		}
+		if kw := node.KubernetesWorker(); kw != nil {
+			logger.Info(fmt.Sprintf(" - kubernetes worker"))
+		}
+
+		// If we're supposed to be a kubernetes worker, start kubernetes services and containerd.
+		// In the future, this might be split further into kubernetes control plane and data plane
+		// roles.
+		var containerdSvc *containerd.Service
+		var kubeSvc *kubernetes.Service
+		if kw := node.KubernetesWorker(); kw != nil {
+			logger.Info("Starting Kubernetes worker services...")
+
+			// Ensure Kubernetes PKI objects exist in etcd.
+			kpkiKV := m.ConsensusKV("cluster", "kpki")
+			kpki := pki.NewKubernetes(lt.MustLeveledFor("pki.kubernetes"), kpkiKV)
+			if err := kpki.EnsureAll(ctx); err != nil {
+				return fmt.Errorf("failed to ensure kubernetes PKI present: %w", err)
+			}
+
+			containerdSvc = &containerd.Service{
+				EphemeralVolume: &root.Ephemeral.Containerd,
+			}
+			if err := supervisor.Run(ctx, "containerd", containerdSvc.Run); err != nil {
+				return fmt.Errorf("failed to start containerd service: %w", err)
+			}
+
+			kubernetesConfig.KPKI = kpki
+			kubernetesConfig.Root = root
+			kubernetesConfig.AdvertiseAddress = *ip
+			kubernetesConfig.CorednsRegistrationChan = corednsRegistrationChan
+			kubeSvc = kubernetes.New(kubernetesConfig)
+			if err := supervisor.Run(ctx, "kubernetes", kubeSvc.Run); err != nil {
+				return fmt.Errorf("failed to start kubernetes service: %w", err)
+			}
+
+		}
+
+		// Start the node debug service.
+		dbg := &debugService{
+			cluster:    m,
+			logtree:    lt,
+			kubernetes: kubeSvc,
+		}
+		dbgSrv := grpc.NewServer()
+		apb.RegisterNodeDebugServiceServer(dbgSrv, dbg)
+		dbgLis, err := net.Listen("tcp", fmt.Sprintf(":%d", common.DebugServicePort))
+		if err != nil {
+			return fmt.Errorf("failed to listen on debug service: %w", err)
+		}
+		if err := supervisor.Run(ctx, "debug", supervisor.GRPCServer(dbgSrv, dbgLis, false)); err != nil {
+			return fmt.Errorf("failed to start debug service: %w", err)
+		}
+
+		supervisor.Signal(ctx, supervisor.SignalHealthy)
+		supervisor.Signal(ctx, supervisor.SignalDone)
+		return nil
+	}, supervisor.WithExistingLogtree(lt))
+
+	// We're PID1, so orphaned processes get reparented to us to clean up
+	for {
+		select {
+		case <-trapdoor:
+			// If the trapdoor got closed, we got stuck early enough in the boot process that we can't do anything about
+			// it. Display a generic error message until we handle error conditions better.
+			ctxC()
+			log.Printf("                  ########################")
+			log.Printf("                  # GURU MEDIATION ERROR #")
+			log.Printf("                  ########################")
+			log.Printf("")
+			log.Printf("Smalltown encountered an uncorrectable error and must be restarted.")
+			log.Printf("(Error condition: init trapdoor closed)")
+			log.Printf("")
+			select {}
+
+		case sig := <-signalChannel:
+			switch sig {
+			case unix.SIGCHLD:
+				var status unix.WaitStatus
+				var rusage unix.Rusage
+				for {
+					res, err := unix.Wait4(-1, &status, unix.WNOHANG, &rusage)
+					if err != nil && err != unix.ECHILD {
+						logger.Errorf("Failed to wait on orphaned child: %v", err)
+						break
+					}
+					if res <= 0 {
+						break
+					}
+				}
+			case unix.SIGURG:
+				// Go 1.14 introduced asynchronous preemption, which uses SIGURG.
+				// In order not to break backwards compatibility in the unlikely case
+				// of an application actually using SIGURG on its own, they're not filtering them.
+				// (https://github.com/golang/go/issues/37942)
+				logger.V(5).Info("Ignoring SIGURG")
+			// TODO(lorenz): We can probably get more than just SIGCHLD as init, but I can't think
+			// of any others right now, just log them in case we hit any of them.
+			default:
+				logger.Warningf("Got unexpected signal %s", sig.String())
+			}
+		}
+	}
+}
+
+// nodeCertificate creates a node key/certificate for a foreign node. This is duplicated code with localstorage's
+// PKIDirectory EnsureSelfSigned, but is temporary (and specific to 'golden tickets').
+func (s *debugService) nodeCertificate() (cert, key []byte, err error) {
+	pubKey, privKey, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		err = fmt.Errorf("failed to generate key: %w", err)
+		return
+	}
+
+	key, err = x509.MarshalPKCS8PrivateKey(privKey)
+	if err != nil {
+		err = fmt.Errorf("failed to marshal key: %w", err)
+		return
+	}
+
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 127)
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	if err != nil {
+		err = fmt.Errorf("failed to generate serial number: %w", err)
+		return
+	}
+
+	template := localstorage.CertificateForNode(pubKey)
+	template.SerialNumber = serialNumber
+
+	cert, err = x509.CreateCertificate(rand.Reader, &template, &template, pubKey, privKey)
+	if err != nil {
+		err = fmt.Errorf("could not sign certificate: %w", err)
+		return
+	}
+	return
+}