cmd/hello: break out local HTTP client into client/tailscale

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

client/tailscale/tailscale.go

@@ -0,0 +1,90 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tailscale contains Tailscale client code.
+package tailscale
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	"tailscale.com/safesocket"
+	"tailscale.com/tailcfg"
+)
+
+// tsClient does HTTP requests to the local Tailscale daemon.
+var tsClient = &http.Client{
+	Transport: &http.Transport{
+		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			if addr != "local-tailscaled.sock:80" {
+				return nil, fmt.Errorf("unexpected URL address %q", addr)
+			}
+			// On macOS, when dialing from non-sandboxed program to sandboxed GUI running
+			// a TCP server on a random port, find the random port. For HTTP connections,
+			// we don't send the token. It gets added in an HTTP Basic-Auth header.
+			if port, _, err := safesocket.LocalTCPPortAndToken(); err == nil {
+				var d net.Dialer
+				return d.DialContext(ctx, "tcp", "localhost:"+strconv.Itoa(port))
+			}
+			return safesocket.ConnectDefault()
+		},
+	},
+}
+
+// DoLocalRequest makes an HTTP request to the local machine's Tailscale daemon.
+//
+// URLs are of the form http://local-tailscaled.sock/localapi/v0/whois?ip=1.2.3.4.
+//
+// The hostname must be "local-tailscaled.sock", even though it
+// doesn't actually do any DNS lookup. The actual means of connecting to and
+// authenticating to the local Tailscale daemon vary by platform.
+//
+// DoLocalRequest may mutate the request to add Authorization headers.
+func DoLocalRequest(req *http.Request) (*http.Response, error) {
+	if _, token, err := safesocket.LocalTCPPortAndToken(); err == nil {
+		req.SetBasicAuth("", token)
+	}
+	return tsClient.Do(req)
+}
+
+// WhoIs returns the owner of the remoteAddr, which must be an IP or IP:port.
+func WhoIs(ctx context.Context, remoteAddr string) (*tailcfg.WhoIsResponse, error) {
+	var ip string
+	if net.ParseIP(remoteAddr) != nil {
+		ip = remoteAddr
+	} else {
+		var err error
+		ip, _, err = net.SplitHostPort(remoteAddr)
+		if err != nil {
+			return nil, fmt.Errorf("invalid remoteAddr %q", remoteAddr)
+		}
+	}
+	req, err := http.NewRequestWithContext(ctx, "GET", "http://local-tailscaled.sock/localapi/v0/whois?ip="+url.QueryEscape(ip), nil)
+	if err != nil {
+		return nil, err
+	}
+	res, err := DoLocalRequest(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	slurp, _ := ioutil.ReadAll(res.Body)
+	if res.StatusCode != 200 {
+		return nil, fmt.Errorf("HTTP %s: %s", res.Status, slurp)
+	}
+	r := new(tailcfg.WhoIsResponse)
+	if err := json.Unmarshal(slurp, r); err != nil {
+		if max := 200; len(slurp) > max {
+			slurp = slurp[:max]
+		}
+		return nil, fmt.Errorf("failed to parse JSON WhoIsResponse from %q", slurp)
+	}
+	return r, nil
+}

cmd/hello/hello.go

@@ -10,19 +10,15 @@ import (
 	_ "embed"
 	"encoding/json"
 	"flag"
-	"fmt"
 	"html/template"
 	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
-	"net/url"
 	"os"
-	"strconv"
 	"strings"
 
-	"tailscale.com/safesocket"
-	"tailscale.com/tailcfg"
+	"tailscale.com/client/tailscale"
 )
 
 var (
@@ -37,7 +33,7 @@ var embeddedTemplate string
 func main() {
 	flag.Parse()
 	if *testIP != "" {
-		res, err := whoIs(*testIP)
+		res, err := tailscale.WhoIs(context.Background(), *testIP)
 		if err != nil {
 			log.Fatal(err)
 		}
@@ -46,7 +42,14 @@ func main() {
 		e.Encode(res)
 		return
 	}
-	if !devMode() {
+	if devMode() {
+		// Parse it optimistically
+		var err error
+		tmpl, err = template.New("home").Parse(embeddedTemplate)
+		if err != nil {
+			log.Printf("ignoring template error in dev mode: %v", err)
+		}
+	} else {
 		if embeddedTemplate == "" {
 			log.Fatalf("embeddedTemplate is empty; must be build with Go 1.16+")
 		}
@@ -76,24 +79,24 @@ func main() {
 	log.Fatal(<-errc)
 }
 
-func slurpHTML() string {
-	slurp, err := ioutil.ReadFile("hello.tmpl.html")
-	if err != nil {
-		log.Fatal(err)
-	}
-	return string(slurp)
-}
-
 func devMode() bool { return *httpsAddr == "" && *httpAddr != "" }
 
 func getTmpl() (*template.Template, error) {
 	if devMode() {
-		return template.New("home").Parse(slurpHTML())
+		tmplData, err := ioutil.ReadFile("hello.tmpl.html")
+		if os.IsNotExist(err) {
+			log.Printf("using baked-in template in dev mode; can't find hello.tmpl.html in current directory")
+			return tmpl, nil
+		}
+		return template.New("home").Parse(string(tmplData))
 	}
 	return tmpl, nil
 }
 
-var tmpl *template.Template // not used in dev mode, initialized by main after flag parse
+// tmpl is the template used in prod mode.
+// In dev mode it's only used if the template file doesn't exist on disk.
+// It's initialized by main after flag parsing.
+var tmpl *template.Template
 
 type tmplData struct {
 	DisplayName   string // "Foo Barberson"
@@ -117,11 +120,6 @@ func root(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/", http.StatusFound)
 		return
 	}
-	ip, _, err := net.SplitHostPort(r.RemoteAddr)
-	if err != nil {
-		http.Error(w, "no remote addr", 500)
-		return
-	}
 	tmpl, err := getTmpl()
 	if err != nil {
 		w.Header().Set("Content-Type", "text/plain")
@@ -129,7 +127,7 @@ func root(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	who, err := whoIs(ip)
+	who, err := tailscale.WhoIs(r.Context(), r.RemoteAddr)
 	var data tmplData
 	if err != nil {
 		if devMode() {
@@ -143,11 +141,12 @@ func root(w http.ResponseWriter, r *http.Request) {
 				IP:            "100.1.2.3",
 			}
 		} else {
-			log.Printf("whois(%q) error: %v", ip, err)
+			log.Printf("whois(%q) error: %v", r.RemoteAddr, err)
 			http.Error(w, "Your Tailscale works, but we failed to look you up.", 500)
 			return
 		}
 	} else {
+		ip, _, _ := net.SplitHostPort(r.RemoteAddr)
 		data = tmplData{
 			DisplayName:   who.UserProfile.DisplayName,
 			LoginName:     who.UserProfile.LoginName,
@@ -168,48 +167,3 @@ func firstLabel(s string) string {
 	}
 	return s
 }
-
-// tsSockClient does HTTP requests to the local Tailscale daemon.
-// The hostname in the HTTP request is ignored.
-var tsSockClient = &http.Client{
-	Transport: &http.Transport{
-		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
-			// On macOS, when dialing from non-sandboxed program to sandboxed GUI running
-			// a TCP server on a random port, find the random port. For HTTP connections,
-			// we don't send the token. It gets added in an HTTP Basic-Auth header.
-			if port, _, err := safesocket.LocalTCPPortAndToken(); err == nil {
-				var d net.Dialer
-				return d.DialContext(ctx, "tcp", "localhost:"+strconv.Itoa(port))
-			}
-			return safesocket.ConnectDefault()
-		},
-	},
-}
-
-func whoIs(ip string) (*tailcfg.WhoIsResponse, error) {
-	ctx := context.Background()
-	req, err := http.NewRequestWithContext(ctx, "GET", "http://local-tailscaled.sock/localapi/v0/whois?ip="+url.QueryEscape(ip), nil)
-	if err != nil {
-		return nil, err
-	}
-	if _, token, err := safesocket.LocalTCPPortAndToken(); err == nil {
-		req.SetBasicAuth("", token)
-	}
-	res, err := tsSockClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer res.Body.Close()
-	slurp, _ := ioutil.ReadAll(res.Body)
-	if res.StatusCode != 200 {
-		return nil, fmt.Errorf("HTTP %s: %s", res.Status, slurp)
-	}
-	r := new(tailcfg.WhoIsResponse)
-	if err := json.Unmarshal(slurp, r); err != nil {
-		if max := 200; len(slurp) > max {
-			slurp = slurp[:max]
-		}
-		return nil, fmt.Errorf("failed to parse JSON WhoIsResponse from %q", slurp)
-	}
-	return r, nil
-}