ipn/ipnstate: put SSH Host Keys in ipnstate.PeerStatus

Updates #3802

Change-Id: I47ba3b4545b25988f375bd867aecd98bb0da8d79
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnlocal/local.go

@@ -472,6 +472,7 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 			ShareeNode:     p.Hostinfo.ShareeNode(),
 			ExitNode:       p.StableID != "" && p.StableID == b.prefs.ExitNodeID,
 			ExitNodeOption: exitNodeOption,
+			SSH_HostKeys:   p.Hostinfo.SSH_HostKeys().AsSlice(),
 		})
 	}
 }

ipn/ipnstate/ipnstate.go

@@ -145,6 +145,9 @@ type PeerStatus struct {
 	PeerAPIURL   []string
 	Capabilities []string `json:",omitempty"`
 
+	// SSH_HostKeys are the node's SSH host keys, if known.
+	SSH_HostKeys []string `json:"sshHostKeys,omitempty"`
+
 	// ShareeNode indicates this node exists in the netmap because
 	// it's owned by a shared-to user and that node might connect
 	// to us. These nodes should be hidden by "tailscale status"
@@ -284,6 +287,9 @@ func (sb *StatusBuilder) AddPeer(peer key.NodePublic, st *PeerStatus) {
 	if v := st.OS; v != "" {
 		e.OS = st.OS
 	}
+	if v := st.SSH_HostKeys; v != nil {
+		e.SSH_HostKeys = v
+	}
 	if v := st.Addrs; v != nil {
 		e.Addrs = v
 	}