Refuse a converged genesis on a machine in use, naming every container and listener counted (hq ADR 0100)

2026-09-22 17:29:32 +02:00
parent 3964d9da0a
commit 4811f176fd
3 changed files with 217 additions and 0 deletions
@@ -0,0 +1,113 @@
+package bootstrap
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"strings"
+
+	"github.com/novox/mesh-host/internal/reachable"
+	"github.com/novox/mesh-host/internal/store"
+)
+
+// quietUDP are processes whose UDP sockets every fresh machine has — name resolution, address
+// configuration, time — and which serve nobody. ss names a process by its first fifteen characters,
+// so both spellings are here.
+//
+// **Still to be measured** (novox/hq ADR 0100): this list is what a fresh machine is expected to
+// hold, and it must be checked against a freshly installed lab machine before it is trusted.
+var quietUDP = map[string]bool{
+	"systemd-resolved": true, "systemd-resolve": true,
+	"systemd-networkd": true, "systemd-network": true,
+	"systemd-timesyncd": true, "systemd-timesyn": true,
+	"dhcpcd": true,
+}
+
+// InUse says what makes this machine a machine in use (novox/hq ADR 0100): every running container
+// no host made, and every socket listening on an address other than loopback that is not ssh's — a
+// UDP one only when it is held by something other than what every fresh machine runs. ours names
+// what the mesh itself runs, which a re-run of genesis finds and does not count.
+func InUse(ctx context.Context, run Runner, ours func(name string) bool) ([]string, []reachable.Reach, error) {
+	var containers []string
+	out, err := run(ctx, "docker", "ps", "--format", "{{.Names}}\t{{.Label \"mesh-host.spec\"}}")
+	if err != nil {
+		return nil, nil, fmt.Errorf("cannot ask the container runtime what is running here: %w", err)
+	}
+	for _, line := range strings.Split(out, "\n") {
+		name, label, _ := strings.Cut(strings.TrimSpace(line), "\t")
+		label = strings.TrimSpace(label)
+		if name == "" || (label != "" && label != "<no value>") || ours(name) {
+			continue
+		}
+		containers = append(containers, name)
+	}
+
+	listening, err := run(ctx, "ss", "-Hltunp")
+	if err != nil {
+		return nil, nil, fmt.Errorf("cannot read what listens on this machine: %w", err)
+	}
+	var listeners []reachable.Reach
+	for _, r := range reachable.Sockets(listening) {
+		if counts(r) && !ours(r.By) {
+			listeners = append(listeners, r)
+		}
+	}
+	return containers, listeners, nil
+}
+
+func counts(r reachable.Reach) bool {
+	if ip := net.ParseIP(r.Address); ip != nil && ip.IsLoopback() {
+		return false
+	}
+	switch r.Protocol {
+	case "tcp":
+		return r.By != "sshd" && !(r.By == "" && r.Port == 22)
+	case "udp":
+		return !quietUDP[r.By]
+	}
+	return false
+}
+
+// RefuseAMachineInUse is the check a converged genesis makes before changing anything: a machine
+// in use is refused, naming every container and listener counted, because raising the foundation's
+// filter there would close what it serves — a forgotten --adopted must not close a working machine.
+// An adopted genesis is told what it found, and goes on.
+func RefuseAMachineInUse(ctx context.Context, o Options, run Runner, say func(string)) error {
+	known, err := store.Load(o.State)
+	if err != nil {
+		return err
+	}
+	if len(known.Resources) > 0 {
+		// What genesis raised on an earlier run is the mesh's, and it is what the machine now
+		// serves; the question was answered the first time.
+		say("  in use            not asked: this machine carries what an earlier genesis raised")
+		return nil
+	}
+	containers, listeners, err := InUse(ctx, run, func(string) bool { return false })
+	if err != nil {
+		return err
+	}
+	if len(containers) == 0 && len(listeners) == 0 {
+		say("  in use            no: no container runs and nothing listens beyond ssh")
+		return nil
+	}
+	var named []string
+	for _, c := range containers {
+		named = append(named, "container "+c)
+	}
+	for _, l := range listeners {
+		by := l.By
+		if by == "" {
+			by = "an unnamed process"
+		}
+		named = append(named, fmt.Sprintf("%s %s:%d by %s", l.Protocol, l.Address, l.Port, by))
+	}
+	if o.Adopted {
+		say(fmt.Sprintf("  in use            yes, and adopted: %d thing(s) found are kept", len(named)))
+		return nil
+	}
+	return fmt.Errorf("this machine is in use, and a converged genesis would close what it serves:\n  - %s\n"+
+		"If it is meant to join the mesh keeping what it runs, pass --adopted: its firewall stays in "+
+		"force and every module is taken on it one at a time. Nothing was changed",
+		strings.Join(named, "\n  - "))
+}