MINOR: h3: check if frame is valid for stream type

Define a new function h3_is_frame_valid(). It returns if a frame is
valid or not depending on the stream which received it.

For the moment, it is used in h3_decode_qcs() which only deals with
bidirectional streams. Soon, uni streams will use the same function,
rendering the frame type check useful.

diff --git a/src/h3.c b/src/h3.c
index 3510e644016ec1999af22da1dc93c1c6c99ea150..11440e726b90d1027b9222bf9bf641a37ad96a58 100644 (file)
--- a/src/h3.c
+++ b/src/h3.c
@@ -41,10 +41,11 @@
 #define h3_debug_hexdump(...) do { } while (0)
 #endif
 
-#define H3_CF_SETTINGS_SENT     0x00000001
-#define H3_CF_UNI_CTRL_SET      0x00000002  /* Remote H3 Control stream opened */
-#define H3_CF_UNI_QPACK_DEC_SET 0x00000004  /* Remote QPACK decoder stream opened */
-#define H3_CF_UNI_QPACK_ENC_SET 0x00000008  /* Remote QPACK encoder stream opened */
+#define H3_CF_SETTINGS_SENT     0x00000001  /* SETTINGS frame already sent on local control stream */
+#define H3_CF_SETTINGS_RECV     0x00000002  /* SETTINGS frame already received on remote control stream */
+#define H3_CF_UNI_CTRL_SET      0x00000004  /* Remote H3 Control stream opened */
+#define H3_CF_UNI_QPACK_DEC_SET 0x00000008  /* Remote QPACK decoder stream opened */
+#define H3_CF_UNI_QPACK_ENC_SET 0x00000010  /* Remote QPACK encoder stream opened */
 
 /* Default settings */
 static uint64_t h3_settings_qpack_max_table_capacity = 0;
@@ -172,6 +173,56 @@ static inline size_t h3_decode_frm_header(uint64_t *ftype, uint64_t *flen,
        return hlen;
 }
 
+/* Check if H3 frame of type <ftype> is valid when received on stream <qcs>.
+ *
+ * Returns a boolean. If false, a connection error H3_FRAME_UNEXPECTED should
+ * be reported.
+ */
+static int h3_is_frame_valid(struct h3c *h3c, struct qcs *qcs, uint64_t ftype)
+{
+       struct h3s *h3s = qcs->ctx;
+       const uint64_t id = qcs->id;
+
+       BUG_ON_HOT(h3s->type == H3S_T_UNKNOWN);
+
+       switch (ftype) {
+       case H3_FT_DATA:
+       case H3_FT_HEADERS:
+               return h3s->type != H3S_T_CTRL;
+
+       case H3_FT_CANCEL_PUSH:
+       case H3_FT_GOAWAY:
+       case H3_FT_MAX_PUSH_ID:
+               /* Only allowed for control stream. First frame of control
+                * stream MUST be SETTINGS.
+                */
+               return h3s->type == H3S_T_CTRL &&
+                      (h3c->flags & H3_CF_SETTINGS_RECV);
+
+       case H3_FT_SETTINGS:
+               /* draft-ietf-quic-http34 7.2.4. SETTINGS
+                *
+                * If an endpoint receives a second SETTINGS frame on the control
+                * stream, the endpoint MUST respond with a connection error of type
+                * H3_FRAME_UNEXPECTED.
+                */
+               return h3s->type == H3S_T_CTRL &&
+                      !(h3c->flags & H3_CF_SETTINGS_RECV);
+
+       case H3_FT_PUSH_PROMISE:
+               return h3s->type != H3S_T_CTRL &&
+                      (id & QCS_ID_SRV_INTIATOR_BIT);
+
+       default:
+               /* draft-ietf-quic-http34 9. Extensions to HTTP/3
+                *
+                * Implementations MUST discard frames [...] that have unknown
+                * or unsupported types.
+                */
+               return h3s->type != H3S_T_CTRL || (h3c->flags & H3_CF_SETTINGS_RECV);
+       }
+}
+
 /* Parse from buffer <buf> a H3 HEADERS frame of length <len>. Data are copied
  * in a local HTX buffer and transfer to the conn-stream layer. <fin> must be
  * set if this is the last data to transfer from this stream.
@@ -340,6 +391,7 @@ static int h3_data_to_htx(struct qcs *qcs, struct ncbuf *buf, uint64_t len,
 static int h3_decode_qcs(struct qcs *qcs, int fin, void *ctx)
 {
        struct ncbuf *rxbuf = &qcs->rx.ncbuf;
+       struct h3c *h3c = ctx;
        struct h3s *h3s = qcs->ctx;
        ssize_t ret;
 
@@ -370,6 +422,11 @@ static int h3_decode_qcs(struct qcs *qcs, int fin, void *ctx)
                flen = h3s->demux_frame_len;
                ftype = h3s->demux_frame_type;
 
+               if (!h3_is_frame_valid(h3c, qcs, ftype)) {
+                       qcc_emit_cc_app(qcs->qcc, H3_FRAME_UNEXPECTED);
+                       return 1;
+               }
+
                /* Do not demux incomplete frames except H3 DATA which can be
                 * fragmented in multiple HTX blocks.
                 */
@@ -406,7 +463,9 @@ static int h3_decode_qcs(struct qcs *qcs, int fin, void *ctx)
                        break;
                default:
                        /* draft-ietf-quic-http34 9. Extensions to HTTP/3
-                        * unknown frame types MUST be ignored
+                        *
+                        * Implementations MUST discard frames [...] that have unknown
+                        * or unsupported types.
                         */
                        h3_debug_printf(stderr, "ignore unknown frame type 0x%lx\n", ftype);
                        ret = flen;