cmd/tailscale, ipn/ipnstate: note which nodes are exit nodes in status

Fixes #3446

Change-Id: Ib41d588e7fa434c02d134fa449f85b0e15083683
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/status.go

@@ -148,6 +148,8 @@ func runStatus(ctx context.Context, args []string) error {
 		if !ps.Active {
 			if ps.ExitNode {
 				f("idle; exit node")
+			} else if ps.ExitNodeOption {
+				f("idle; offers exit node")
 			} else if anyTraffic {
 				f("idle")
 			} else {
@@ -157,6 +159,8 @@ func runStatus(ctx context.Context, args []string) error {
 			f("active; ")
 			if ps.ExitNode {
 				f("exit node; ")
+			} else if ps.ExitNodeOption {
+				f("offers exit node; ")
 			}
 			if relay != "" && ps.CurAddr == "" {
 				f("relay %q", relay)

ipn/ipnlocal/local.go

@@ -402,6 +402,9 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 				tailscaleIPs = append(tailscaleIPs, addr.IP())
 			}
 		}
+		exitNodeOption := tsaddr.PrefixesContainsFunc(p.AllowedIPs, func(r netaddr.IPPrefix) bool {
+			return r.Bits() == 0
+		})
 		sb.AddPeer(p.Key, &ipnstate.PeerStatus{
 			InNetworkMap:       true,
 			ID:                 p.StableID,
@@ -416,6 +419,7 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 			LastSeen:           lastSeen,
 			ShareeNode:         p.Hostinfo.ShareeNode,
 			ExitNode:           p.StableID != "" && p.StableID == b.prefs.ExitNodeID,
+			ExitNodeOption:     exitNodeOption,
 		})
 	}
 }

ipn/ipnstate/ipnstate.go

@@ -96,14 +96,15 @@ type PeerStatus struct {
 	CurAddr string // one of Addrs, or unique if roaming
 	Relay   string // DERP region
 
-	RxBytes       int64
-	TxBytes       int64
-	Created       time.Time // time registered with tailcontrol
-	LastWrite     time.Time // time last packet sent
-	LastSeen      time.Time // last seen to tailcontrol
-	LastHandshake time.Time // with local wireguard
-	KeepAlive     bool
-	ExitNode      bool // true if this is the currently selected exit node.
+	RxBytes        int64
+	TxBytes        int64
+	Created        time.Time // time registered with tailcontrol
+	LastWrite      time.Time // time last packet sent
+	LastSeen       time.Time // last seen to tailcontrol
+	LastHandshake  time.Time // with local wireguard
+	KeepAlive      bool
+	ExitNode       bool // true if this is the currently selected exit node.
+	ExitNodeOption bool // true if this node can be an exit node (offered && approved)
 
 	// Active is whether the node was recently active. The
 	// definition is somewhat undefined but has historically and
@@ -290,6 +291,9 @@ func (sb *StatusBuilder) AddPeer(peer key.NodePublic, st *PeerStatus) {
 	if st.ExitNode {
 		e.ExitNode = true
 	}
+	if st.ExitNodeOption {
+		e.ExitNodeOption = true
+	}
 	if st.ShareeNode {
 		e.ShareeNode = true
 	}