The header size and the idle time as settings (closes #70)

SWWAF_CLIENT_REQUEST_HEADER_MAX_BYTES (default 32K) and
SWWAF_CLIENT_IDLE_TIMEOUT (default 120s) replace the two values the
proxy fixed, and are read like the other size and duration settings.

Go's server reads 4K past the header limit it is given before it
refuses, so it is still given the setting less 4K, and a header size
of 4K or less, or off, stops the start. The idle time can be off.

README.md lists both settings and no longer calls them fixed.

Model: opus-5-5

internal/proxy/passthrough_test.go

@@ -297,7 +297,7 @@ func echoAfterUpgrade(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func TestServerHasTheFixedLimits(t *testing.T) {
+func TestServerHasTheDefaultLimits(t *testing.T) {
 	t.Parallel()
 
 	cfg, err := config.FromEnvironment(func(string) (string, bool) { return "", false })
@@ -319,37 +319,48 @@ func TestServerHasTheFixedLimits(t *testing.T) {
 	}
 }
 
-func TestRefusesHeadersOver32KiB(t *testing.T) {
+func TestRefusesHeadersOverTheLimit(t *testing.T) {
 	t.Parallel()
 
-	var calls atomic.Int32
-
-	app := startApp(t, func(http.ResponseWriter, *http.Request) {
-		calls.Add(1)
-	})
-	addr, _ := startProxy(t, app.URL, nil)
-
-	// size counts every byte of the request: the request line, the
-	// headers and the blank line that ends them.
-	const (
-		start = "GET / HTTP/1.1\r\nHost: app\r\nX-Large: "
-		end   = "\r\n\r\n"
-	)
-
 	for _, tc := range []struct {
-		size int
-		want int
+		name  string
+		env   map[string]string
+		limit int
 	}{
-		{size: 32 << 10, want: http.StatusOK},
-		{size: 32<<10 + 1, want: http.StatusRequestHeaderFieldsTooLarge},
+		{"by default", nil, 32 << 10},
+		{"as set", map[string]string{clientHeaderMaxBytes: "8K"}, 8 << 10},
 	} {
-		conn := dial(t, addr)
-		send(t, conn, start+strings.Repeat("a", tc.size-len(start)-len(end))+end)
-		wantStatus(t, readResponse(t, conn), tc.want)
-	}
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
 
-	if calls.Load() != 1 {
-		t.Errorf("the app was called %d times, want once", calls.Load())
+			var calls atomic.Int32
+
+			app := startApp(t, func(http.ResponseWriter, *http.Request) {
+				calls.Add(1)
+			})
+			addr, _ := startProxy(t, app.URL, tc.env)
+
+			// size counts every byte of the request: the request line,
+			// the headers and the blank line that ends them.
+			const (
+				start = "GET / HTTP/1.1\r\nHost: app\r\nX-Large: "
+				end   = "\r\n\r\n"
+			)
+
+			for _, sent := range []struct{ size, want int }{
+				{tc.limit, http.StatusOK},
+				{tc.limit + 1, http.StatusRequestHeaderFieldsTooLarge},
+			} {
+				conn := dial(t, addr)
+				send(t, conn,
+					start+strings.Repeat("a", sent.size-len(start)-len(end))+end)
+				wantStatus(t, readResponse(t, conn), sent.want)
+			}
+
+			if calls.Load() != 1 {
+				t.Errorf("the app was called %d times, want once", calls.Load())
+			}
+		})
 	}
 }