tailcfg, ipn/ipnlocal: add Hostinfo.SSH_HostKeys, send when SSH enabled

(The name SSH_HostKeys is bad but SSHHostKeys is worse.)

Updates #3802

Change-Id: I2a889019c9e8b065b668dd58140db4fcab868a91
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

tailcfg/tailcfg.go

@@ -454,6 +454,7 @@ type Hostinfo struct {
 	RequestTags   []string           `json:",omitempty"` // set of ACL tags this node wants to claim
 	Services      []Service          `json:",omitempty"` // services advertised by this machine
 	NetInfo       *NetInfo           `json:",omitempty"`
+	SSH_HostKeys  []string           `json:"sshHostKeys,omitempty"` // if advertised
 
 	// NOTE: any new fields containing pointers in this type
 	//       require changes to Hostinfo.Equal.
@@ -516,6 +517,10 @@ func (v HostinfoView) RequestTags() views.StringSlice {
 	return views.StringSliceOf(v.ж.RequestTags)
 }
 
+func (v HostinfoView) SSH_HostKeys() views.StringSlice {
+	return views.StringSliceOf(v.ж.SSH_HostKeys)
+}
+
 func (v HostinfoView) Services() ServiceSlice {
 	return ServiceSliceOf(v.ж.Services)
 }

tailcfg/tailcfg_clone.go

@@ -106,6 +106,7 @@ func (src *Hostinfo) Clone() *Hostinfo {
 	dst.RequestTags = append(src.RequestTags[:0:0], src.RequestTags...)
 	dst.Services = append(src.Services[:0:0], src.Services...)
 	dst.NetInfo = src.NetInfo.Clone()
+	dst.SSH_HostKeys = append(src.SSH_HostKeys[:0:0], src.SSH_HostKeys...)
 	return dst
 }
 
@@ -126,6 +127,7 @@ var _HostinfoCloneNeedsRegeneration = Hostinfo(struct {
 	RequestTags   []string
 	Services      []Service
 	NetInfo       *NetInfo
+	SSH_HostKeys  []string
 }{})
 
 // Clone makes a deep copy of NetInfo.

tailcfg/tailcfg_test.go

@@ -32,7 +32,7 @@ func TestHostinfoEqual(t *testing.T) {
 		"ShieldsUp", "ShareeNode",
 		"GoArch",
 		"RoutableIPs", "RequestTags",
-		"Services", "NetInfo",
+		"Services", "NetInfo", "SSH_HostKeys",
 	}
 	if have := fieldsOf(reflect.TypeOf(Hostinfo{})); !reflect.DeepEqual(have, hiHandles) {
 		t.Errorf("Hostinfo.Equal check might be out of sync\nfields: %q\nhandled: %q\n",
@@ -181,6 +181,11 @@ func TestHostinfoEqual(t *testing.T) {
 			&Hostinfo{},
 			false,
 		},
+		{
+			&Hostinfo{SSH_HostKeys: []string{"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIO.... root@bar"}},
+			&Hostinfo{},
+			false,
+		},
 	}
 	for i, tt := range tests {
 		got := tt.a.Equal(tt.b)