From 9659ab81e0e74f3f650a1cb78eb74f0df3914ef2 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Mon, 29 Mar 2021 12:49:13 -0700
Subject: [PATCH] ipn/ipnlocal: send peerapi port(s) in Hostinfo.Services

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
---
 ipn/ipnlocal/local.go   | 41 ++++++++++++++++++++++++++++++++---------
 ipn/ipnlocal/peerapi.go |  1 +
 2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/ipn/ipnlocal/local.go b/ipn/ipnlocal/local.go
index 9a8c59bce..f225ecfe4 100644
--- a/ipn/ipnlocal/local.go
+++ b/ipn/ipnlocal/local.go
@@ -1330,25 +1330,47 @@ func (b *LocalBackend) SetPrefs(newp *ipn.Prefs) {
 	b.send(ipn.Notify{Prefs: newp})
 }
 
+func (b *LocalBackend) peerAPIServicesLocked() (ret []tailcfg.Service) {
+	for _, pln := range b.peerAPIListeners {
+		proto := tailcfg.ServiceProto("peerapi4")
+		if pln.ip.Is6() {
+			proto = "peerapi6"
+		}
+		ret = append(ret, tailcfg.Service{
+			Proto: proto,
+			Port:  uint16(pln.Port()),
+		})
+	}
+	return ret
+}
+
 // doSetHostinfoFilterServices calls SetHostinfo on the controlclient,
 // possibly after mangling the given hostinfo.
 //
 // TODO(danderson): we shouldn't be mangling hostinfo here after
 // painstakingly constructing it in twelvety other places.
 func (b *LocalBackend) doSetHostinfoFilterServices(hi *tailcfg.Hostinfo) {
-	hi2 := *hi
-	if !b.shouldUploadServices() {
-		hi2.Services = []tailcfg.Service{}
-	}
-
 	b.mu.Lock()
-	cli := b.c
+	cc := b.c
+	if cc == nil {
+		// Control client isn't up yet.
+		b.mu.Unlock()
+		return
+	}
+	peerAPIServices := b.peerAPIServicesLocked()
 	b.mu.Unlock()
 
-	// b.c might not be started yet
-	if cli != nil {
-		cli.SetHostinfo(&hi2)
+	// Make a shallow copy of hostinfo so we can mutate
+	// at the Service field.
+	hi2 := *hi // shallow copy
+	if !b.shouldUploadServices() {
+		hi2.Services = []tailcfg.Service{}
 	}
+	// Don't mutate hi.Service's underlying array. Append to
+	// the slice with no free capacity.
+	c := len(hi2.Services)
+	hi2.Services = append(hi2.Services[:c:c], peerAPIServices...)
+	cc.SetHostinfo(&hi2)
 }
 
 // NetMap returns the latest cached network map received from
@@ -1490,6 +1512,7 @@ func (b *LocalBackend) initPeerAPIListener() {
 		}
 		pln := &peerAPIListener{
 			ps: ps,
+			ip: a.IP,
 			ln: ln,
 			lb: b,
 		}
diff --git a/ipn/ipnlocal/peerapi.go b/ipn/ipnlocal/peerapi.go
index 43d6ceb78..857639610 100644
--- a/ipn/ipnlocal/peerapi.go
+++ b/ipn/ipnlocal/peerapi.go
@@ -80,6 +80,7 @@ func (s *peerAPIServer) listen(ip netaddr.IP, ifState *interfaces.State) (ln net
 
 type peerAPIListener struct {
 	ps     *peerAPIServer
+	ip     netaddr.IP
 	ln     net.Listener
 	lb     *LocalBackend
 	urlStr string