usm: http2: fix index calculation (#20931)

* usm: http2: Change type from u8 to u64, to allow indexes bigger than 255

* usm: http2: Add missing parenthesis

That bug cause wrong order or execution and lead into truncation

* usm: http2: Added test

pkg/network/ebpf/c/protocols/http2/decoding.h

@@ -43,18 +43,18 @@ static __always_inline http2_stream_t *http2_fetch_stream(const http2_stream_key
 }
 
 // Similar to read_var_int, but with a small optimization of getting the current character as input argument.
-static __always_inline bool read_var_int_with_given_current_char(struct __sk_buff *skb, skb_info_t *skb_info, __u8 current_char_as_number, __u8 max_number_for_bits, __u8 *out) {
+static __always_inline bool read_var_int_with_given_current_char(struct __sk_buff *skb, skb_info_t *skb_info, __u64 current_char_as_number, __u64 max_number_for_bits, __u64 *out) {
     current_char_as_number &= max_number_for_bits;
 
     if (current_char_as_number < max_number_for_bits) {
         *out = current_char_as_number;
         return true;
     }
 
-    __u8 next_char = 0;
-    if (bpf_skb_load_bytes(skb, skb_info->data_off, &next_char, sizeof(next_char)) >=0 && (next_char & 128) == 0) {
+    __u64 next_char = 0;
+    if (bpf_skb_load_bytes(skb, skb_info->data_off, &next_char, 1) >=0 && (next_char & 128) == 0) {
         skb_info->data_off++;
-        *out = current_char_as_number + next_char & 127;
+        *out = current_char_as_number + (next_char & 127);
         return true;
     }
 
@@ -68,9 +68,9 @@ static __always_inline bool read_var_int_with_given_current_char(struct __sk_buf
 // n must always be between 1 and 8.
 //
 // The returned remain buffer is either a smaller suffix of p, or err != nil.
-static __always_inline bool read_var_int(struct __sk_buff *skb, skb_info_t *skb_info, __u8 max_number_for_bits, __u8 *out) {
-    __u8 current_char_as_number = 0;
-    if (bpf_skb_load_bytes(skb, skb_info->data_off, &current_char_as_number, sizeof(current_char_as_number)) < 0) {
+static __always_inline bool read_var_int(struct __sk_buff *skb, skb_info_t *skb_info, __u64 max_number_for_bits, __u64 *out) {
+    __u64 current_char_as_number = 0;
+    if (bpf_skb_load_bytes(skb, skb_info->data_off, &current_char_as_number, 1) < 0) {
         return false;
     }
     skb_info->data_off++;
@@ -119,8 +119,8 @@ READ_INTO_BUFFER(path, HTTP2_MAX_PATH_LEN, BLK_SIZE)
 
 // parse_field_literal handling the case when the key is part of the static table and the value is a dynamic string
 // which will be stored in the dynamic table.
-static __always_inline bool parse_field_literal(struct __sk_buff *skb, skb_info_t *skb_info, http2_header_t *headers_to_process, __u8 index, __u64 global_dynamic_counter, __u8 *interesting_headers_counter) {
-    __u8 str_len = 0;
+static __always_inline bool parse_field_literal(struct __sk_buff *skb, skb_info_t *skb_info, http2_header_t *headers_to_process, __u64 index, __u64 global_dynamic_counter, __u8 *interesting_headers_counter) {
+    __u64 str_len = 0;
     if (!read_var_int(skb, skb_info, MAX_6_BITS, &str_len)) {
         return false;
     }
@@ -162,8 +162,8 @@ static __always_inline __u8 filter_relevant_headers(struct __sk_buff *skb, skb_i
     const __u32 end = frame_end < skb_info->data_end + 1 ? frame_end : skb_info->data_end + 1;
     bool is_literal = false;
     bool is_indexed = false;
-    __u8 max_bits = 0;
-    __u8 index = 0;
+    __u64 max_bits = 0;
+    __u64 index = 0;
 
     __u64 *global_dynamic_counter = get_dynamic_counter(tup);
     if (global_dynamic_counter == NULL) {

pkg/network/usm/monitor_test.go

@@ -539,6 +539,59 @@ func TestHTTP2(t *testing.T) {
 	})
 }
 
+func (s *USMHTTP2Suite) TestHTTP2ManyDifferentPaths() {
+	t := s.T()
+	cfg := networkconfig.New()
+	cfg.EnableHTTP2Monitoring = true
+
+	startH2CServer(t)
+
+	monitor, err := NewMonitor(cfg, nil, nil, nil)
+	require.NoError(t, err)
+	require.NoError(t, monitor.Start())
+	defer monitor.Stop()
+
+	// Should be bigger than the length of the http2_dynamic_table which is 1024
+	numberOfRequests := 1500
+	clients := getClientsArray(t, 1)
+	for i := 0; i < numberOfRequests; i++ {
+		for j := 0; j < 2; j++ {
+			req, err := clients[0].Post(fmt.Sprintf("%s/test-%d", http2SrvAddr, i+1), "application/json", bytes.NewReader([]byte("test")))
+			require.NoError(t, err, "could not make request")
+			req.Body.Close()
+		}
+	}
+
+	matches := PrintableInt(0)
+
+	seenRequests := map[string]int{}
+	assert.Eventuallyf(t, func() bool {
+		stats := monitor.GetProtocolStats()
+		http2Stats, ok := stats[protocols.HTTP2]
+		if !ok {
+			return false
+		}
+		http2StatsTyped := http2Stats.(map[http.Key]*http.RequestStats)
+		for key, stat := range http2StatsTyped {
+			if (key.DstPort == http2SrvPort || key.SrcPort == http2SrvPort) && key.Method == http.MethodPost && strings.HasPrefix(key.Path.Content.Get(), "/test") {
+				if _, ok := seenRequests[key.Path.Content.Get()]; !ok {
+					seenRequests[key.Path.Content.Get()] = 0
+				}
+				seenRequests[key.Path.Content.Get()] += stat.Data[200].Count
+				matches.Add(stat.Data[200].Count)
+			}
+		}
+
+		return matches.Load() == 2*numberOfRequests
+	}, time.Second*10, time.Millisecond*100, "%v != %v", &matches, 2*numberOfRequests)
+
+	for i := 0; i < numberOfRequests; i++ {
+		if v, ok := seenRequests[fmt.Sprintf("/test-%d", i+1)]; !ok || v != 2 {
+			t.Logf("path: /test-%d should have 2 occurrences but instead has %d", i+1, v)
+		}
+	}
+}
+
 func (s *USMHTTP2Suite) TestSimpleHTTP2() {
 	t := s.T()
 	cfg := networkconfig.New()