tsweb: fix Port80Handler redirect to https with FQDN unset

Fixes the current http://pkgs.tailscale.com/ redirect to https:///
as that server doesn't configure the Port80Handler.FQDN field.

Change-Id: Iff56e6127a46c306ca97738d91b217bcab32a582
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

tsweb/tsweb.go

@@ -162,7 +162,7 @@ func (h Port80Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 	host := h.FQDN
 	if host == "" {
-		host = r.URL.Hostname()
+		host = r.Host
 	}
 	target := "https://" + host + path
 	http.Redirect(w, r, target, http.StatusFound)

tsweb/tsweb_test.go

@@ -580,3 +580,45 @@ func TestAcceptsEncoding(t *testing.T) {
 		}
 	}
 }
+
+func TestPort80Handler(t *testing.T) {
+	tests := []struct {
+		name    string
+		h       *Port80Handler
+		req     string
+		wantLoc string
+	}{
+		{
+			name:    "no_fqdn",
+			h:       &Port80Handler{},
+			req:     "GET / HTTP/1.1\r\nHost: foo.com\r\n\r\n",
+			wantLoc: "https://foo.com/",
+		},
+		{
+			name:    "fqdn_and_path",
+			h:       &Port80Handler{FQDN: "bar.com"},
+			req:     "GET /path HTTP/1.1\r\nHost: foo.com\r\n\r\n",
+			wantLoc: "https://bar.com/path",
+		},
+		{
+			name:    "path_and_query_string",
+			h:       &Port80Handler{FQDN: "baz.com"},
+			req:     "GET /path?a=b HTTP/1.1\r\nHost: foo.com\r\n\r\n",
+			wantLoc: "https://baz.com/path?a=b",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r, _ := http.ReadRequest(bufio.NewReader(strings.NewReader(tt.req)))
+			rec := httptest.NewRecorder()
+			tt.h.ServeHTTP(rec, r)
+			got := rec.Result()
+			if got, want := got.StatusCode, 302; got != want {
+				t.Errorf("got status code %v; want %v", got, want)
+			}
+			if got, want := got.Header.Get("Location"), "https://foo.com/"; got != tt.wantLoc {
+				t.Errorf("Location = %q; want %q", got, want)
+			}
+		})
+	}
+}