A token can be issued for a machine's tunnel key, and it joins through the tunnel

token issue --overlay-key records the key the machine made, binds the
token to it, gives the machine its address and makes it a peer of the
hub, pushing the hub before the token is shown. The token carries the
hub's tunnel and the bus at its address on the private network, and
enrolment refuses any other key (novox/hq ADR 0169). Tokens without a
key enrol as before until the bus is closed. Also a token verb.

internal/token/token.go

@@ -55,6 +55,26 @@ type Token struct {
 	// that it speaks the firewall found on the machine, because an adopted node keeps that firewall
 	// in force. Absent for a converged node, so a converged token is byte for byte what it was.
 	Adopted bool `json:"adopted,omitempty"`
+
+	// Tunnel is the one peer a joining machine needs, when the token was issued for its tunnel key
+	// (novox/hq ADR 0169). The machine brings its tunnel up from this alone and reaches the bus over
+	// it, at an address on the private network — so the bus is never open to the internet. Absent
+	// on a token issued without a key, which then reads byte for byte as before.
+	Tunnel *Tunnel `json:"tunnel,omitempty"`
+}
+
+// Tunnel is the joining machine's side of its first tunnel: its own address and the hub to reach.
+type Tunnel struct {
+	// Key is the public half of the key the machine made itself, which this token was issued for.
+	// The private half never left the machine (novox/hq ADR 0004).
+	Key string `json:"key"`
+	// Address is the machine's own address on the private network, with its prefix.
+	Address string `json:"address"`
+	// Range is the private network, routed through the hub until the machine is told more.
+	Range string `json:"range"`
+	// HubKey and HubEndpoint are the hub's tunnel key and where it is dialled.
+	HubKey      string `json:"hub_key"`
+	HubEndpoint string `json:"hub_endpoint"`
 }
 
 // Missing names the parts that are not filled in.
@@ -83,6 +103,19 @@ func (t Token) Missing() []string {
 	if strings.TrimSpace(t.Secret) == "" {
 		missing = append(missing, "the one-time secret — nothing to present")
 	}
+	if t.Tunnel != nil {
+		for _, part := range []struct{ value, says string }{
+			{t.Tunnel.Key, "the machine's own tunnel key — the hub would not know it"},
+			{t.Tunnel.Address, "the machine's address on the private network"},
+			{t.Tunnel.Range, "the private network's range — nothing to route through the hub"},
+			{t.Tunnel.HubKey, "the hub's tunnel key — nothing to dial"},
+			{t.Tunnel.HubEndpoint, "where the hub's tunnel is dialled"},
+		} {
+			if strings.TrimSpace(part.value) == "" {
+				missing = append(missing, part.says)
+			}
+		}
+	}
 	return missing
 }