Byte limits per client over a minute, an hour and a day (closes #20)

SWWAF_BYTES_LIMIT_PER_MINUTE, _PER_HOUR and _PER_DAY (10G, 20G, 50G)
and SWWAF_BYTES_COUNT (both). A request's bytes are counted once its
answer has ended, for a request passed to the app that the rate limits
count; what a WebSocket carries each way, once it closes. Bytes over a
limit ban the client as a broken rate limit does, and cut nothing
short. clients.json keeps the byte buckets, the log line's counts carry
the byte totals, ban notes say what the limit is on, and the limit hits
metric is labelled by kind.

Judgement call: limit_hit names a byte window minute_bytes, hour_bytes
or day_bytes, as counts names the byte totals.
Judgement call: in observe mode, the bytes of a request enforce mode
would have refused are not counted.

Model: opus-5-5

internal/proxy/bytelimits_test.go

@@ -3,6 +3,7 @@ package proxy_test
 import (
 	"bufio"
 	"io"
+	"net"
 	"net/http"
 	"net/netip"
 	"strconv"
@@ -166,6 +167,39 @@ func TestWebSocketBytesAreCountedOnceItCloses(t *testing.T) {
 	}
 }
 
+func TestWebSocketPassesTheAnswerAfterTheClientStopsSending(t *testing.T) {
+	t.Parallel()
+
+	app := startApp(t, echoOnceTheClientStops)
+	addr, out := startProxy(t, app.URL,
+		map[string]string{trustedProxies: trustLocalhost})
+	s := &sender{t: t, addr: addr, out: out}
+
+	conn, reader := s.openWebSocket()
+	send(t, conn, uploadBody)
+
+	// The client closes its sending side and waits for the answer, which the
+	// app sends only once it has seen the client stop. smallwebwaf passes the
+	// close on to the app through CloseWrite on upgradedConn; without that,
+	// it closes both connections, and the answer is lost.
+	tcp, ok := conn.(*net.TCPConn)
+	if !ok {
+		t.Fatalf("connection is a %T, want a *net.TCPConn", conn)
+	}
+
+	err := tcp.CloseWrite()
+	if err != nil {
+		t.Fatalf("close the sending side: %v", err)
+	}
+
+	got, err := io.ReadAll(reader)
+	if err != nil || string(got) != uploadBody {
+		t.Errorf("got %q (%v), want %q", got, err, uploadBody)
+	}
+
+	s.closeWebSocket(conn)
+}
+
 func TestBytesCountSaysWhichBytesCount(t *testing.T) {
 	t.Parallel()
 
@@ -432,12 +466,52 @@ func answerAfterUpgrade(w http.ResponseWriter, _ *http.Request) {
 	}
 }
 
+// echoOnceTheClientStops is an app that switches protocols, as for a
+// WebSocket, reads what the client sends until the client stops sending,
+// and then sends it all back.
+func echoOnceTheClientStops(w http.ResponseWriter, _ *http.Request) {
+	conn, buffered, err := http.NewResponseController(w).Hijack()
+	if err != nil {
+		return
+	}
+
+	defer func() {
+		_ = conn.Close()
+	}()
+
+	_, _ = buffered.WriteString("HTTP/1.1 101 Switching Protocols\r\n" +
+		"Connection: Upgrade\r\nUpgrade: websocket\r\n\r\n")
+	_ = buffered.Flush()
+
+	received, _ := io.ReadAll(buffered)
+	_, _ = buffered.Write(received)
+	_ = buffered.Flush()
+}
+
 // webSocket opens a WebSocket from client to answerAfterUpgrade, sends a
 // line of bodyBytes on it, reads the answer, and closes it. It checks the
 // answer, and the log line as request does, and returns the log line.
 func (s *sender) webSocket() logLine {
 	s.t.Helper()
 
+	conn, reader := s.openWebSocket()
+	send(s.t, conn, strings.Repeat("u", bodyBytes-1)+"\n")
+
+	got, err := reader.ReadString('\n')
+	if err != nil || len(got) != answerBytes {
+		s.t.Errorf("got %d bytes (%v), want %d", len(got), err, answerBytes)
+	}
+
+	return s.closeWebSocket(conn)
+}
+
+// openWebSocket sends a request from client to switch protocols, as for a
+// WebSocket, and checks that the app switches. It returns the connection,
+// on which reading fails once waitLimit has passed, and a reader of what
+// the app sends on it.
+func (s *sender) openWebSocket() (net.Conn, *bufio.Reader) {
+	s.t.Helper()
+
 	conn := dial(s.t, s.addr)
 	send(s.t, conn, "GET /socket HTTP/1.1\r\nHost: "+appHost+"\r\n"+forwardedFor+
 		": "+client+"\r\nConnection: Upgrade\r\nUpgrade: websocket\r\n\r\n")
@@ -460,12 +534,13 @@ func (s *sender) webSocket() logLine {
 		s.t.Fatalf("status %d, want %d", res.StatusCode, http.StatusSwitchingProtocols)
 	}
 
-	send(s.t, conn, strings.Repeat("u", bodyBytes-1)+"\n")
+	return conn, reader
+}
 
-	got, err := reader.ReadString('\n')
-	if err != nil || len(got) != answerBytes {
-		s.t.Errorf("got %d bytes (%v), want %d", len(got), err, answerBytes)
-	}
+// closeWebSocket closes conn, a WebSocket openWebSocket opened, checks its
+// log line as request does, and returns it.
+func (s *sender) closeWebSocket(conn net.Conn) logLine {
+	s.t.Helper()
 
 	_ = conn.Close()