tsconsensus: add a tsconsensus package

tsconsensus enables tsnet.Server instances to form a consensus.

tsconsensus wraps hashicorp/raft with
 * the ability to do discovery via tailscale tags
 * inter node communication over tailscale
 * routing of commands to the leader

Updates #14667

Signed-off-by: Fran Bull <fran@tailscale.com>

tsconsensus/monitor.go

@@ -0,0 +1,160 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package tsconsensus
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"slices"
+
+	"tailscale.com/ipn"
+	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/tsnet"
+	"tailscale.com/util/dnsname"
+)
+
+type status struct {
+	Status    *ipnstate.Status
+	RaftState string
+}
+
+type monitor struct {
+	ts  *tsnet.Server
+	con *Consensus
+	sg  statusGetter
+}
+
+func (m *monitor) getStatus(ctx context.Context) (status, error) {
+	tStatus, err := m.sg.getStatus(ctx)
+	if err != nil {
+		return status{}, err
+	}
+	return status{Status: tStatus, RaftState: m.con.raft.State().String()}, nil
+}
+
+func serveMonitor(c *Consensus, ts *tsnet.Server, listenAddr string) (*http.Server, error) {
+	ln, err := ts.Listen("tcp", listenAddr)
+	if err != nil {
+		return nil, err
+	}
+	m := &monitor{con: c, ts: ts, sg: &tailscaleStatusGetter{
+		ts: ts,
+	}}
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /full", m.handleFullStatus)
+	mux.HandleFunc("GET /{$}", m.handleSummaryStatus)
+	mux.HandleFunc("GET /netmap", m.handleNetmap)
+	mux.HandleFunc("POST /dial", m.handleDial)
+	srv := &http.Server{Handler: mux}
+	go func() {
+		err := srv.Serve(ln)
+		log.Printf("MonitorHTTP stopped serving with error: %v", err)
+	}()
+	return srv, nil
+}
+
+func (m *monitor) handleFullStatus(w http.ResponseWriter, r *http.Request) {
+	s, err := m.getStatus(r.Context())
+	if err != nil {
+		log.Printf("monitor: error getStatus: %v", err)
+		http.Error(w, "", http.StatusInternalServerError)
+		return
+	}
+	if err := json.NewEncoder(w).Encode(s); err != nil {
+		log.Printf("monitor: error encoding full status: %v", err)
+		return
+	}
+}
+
+func (m *monitor) handleSummaryStatus(w http.ResponseWriter, r *http.Request) {
+	s, err := m.getStatus(r.Context())
+	if err != nil {
+		log.Printf("monitor: error getStatus: %v", err)
+		http.Error(w, "", http.StatusInternalServerError)
+		return
+	}
+	lines := []string{}
+	for _, p := range s.Status.Peer {
+		if p.Online {
+			name := dnsname.FirstLabel(p.DNSName)
+			lines = append(lines, fmt.Sprintf("%s\t\t%d\t%d\t%t", name, p.RxBytes, p.TxBytes, p.Active))
+		}
+	}
+	_, err = w.Write([]byte(fmt.Sprintf("RaftState: %s\n", s.RaftState)))
+	if err != nil {
+		log.Printf("monitor: error writing status: %v", err)
+		return
+	}
+
+	slices.Sort(lines)
+	for _, l := range lines {
+		_, err = w.Write([]byte(fmt.Sprintf("%s\n", l)))
+		if err != nil {
+			log.Printf("monitor: error writing status: %v", err)
+			return
+		}
+	}
+}
+
+func (m *monitor) handleNetmap(w http.ResponseWriter, r *http.Request) {
+	var mask ipn.NotifyWatchOpt = ipn.NotifyInitialNetMap
+	mask |= ipn.NotifyNoPrivateKeys
+	lc, err := m.ts.LocalClient()
+	if err != nil {
+		log.Printf("monitor: error LocalClient: %v", err)
+		http.Error(w, "", http.StatusInternalServerError)
+		return
+	}
+	watcher, err := lc.WatchIPNBus(r.Context(), mask)
+	if err != nil {
+		log.Printf("monitor: error WatchIPNBus: %v", err)
+		http.Error(w, "", http.StatusInternalServerError)
+		return
+	}
+	defer watcher.Close()
+
+	n, err := watcher.Next()
+	if err != nil {
+		log.Printf("monitor: error watcher.Next: %v", err)
+		http.Error(w, "", http.StatusInternalServerError)
+		return
+	}
+	encoder := json.NewEncoder(w)
+	encoder.SetIndent("", "\t")
+	if err := encoder.Encode(n); err != nil {
+		log.Printf("monitor: error encoding netmap: %v", err)
+		return
+	}
+}
+
+func (m *monitor) handleDial(w http.ResponseWriter, r *http.Request) {
+	var dialParams struct {
+		Addr string
+	}
+	defer r.Body.Close()
+	bs, err := io.ReadAll(http.MaxBytesReader(w, r.Body, maxBodyBytes))
+	if err != nil {
+		log.Printf("monitor: error reading body: %v", err)
+		http.Error(w, "", http.StatusInternalServerError)
+		return
+	}
+	err = json.Unmarshal(bs, &dialParams)
+	if err != nil {
+		log.Printf("monitor: error unmarshalling json: %v", err)
+		http.Error(w, "", http.StatusBadRequest)
+		return
+	}
+	c, err := m.ts.Dial(r.Context(), "tcp", dialParams.Addr)
+	if err != nil {
+		log.Printf("monitor: error dialing: %v", err)
+		http.Error(w, "", http.StatusInternalServerError)
+		return
+	}
+	c.Close()
+	w.Write([]byte("ok\n"))
+}