MINOR: quic: adjust buffer handling for STREAM transmission

Simplify the data manipulation of STREAM frames on TX. Only stream data
and len field are used to generate a valid STREAM frames from the
buffer. Do not use the offset field, which required that a single buffer
instance should be shared for every frames on a single stream.

include/haproxy/quic_frame-t.h

@@ -148,10 +148,23 @@ struct quic_new_token {
 struct quic_stream {
 	uint64_t id;
 	struct qcs *qcs;
+
+	/* used only on TX when constructing frames.
+	 * Data cleared when processing ACK related to this STREAM frame.
+	 *
+	 * A same buffer may be shared between several STREAM frames. The
+	 * <data> field of each quic_stream serves to differentiate the payload
+	 * of each of these.
+	 */
 	struct buffer *buf;
+
 	struct eb64_node offset;
 	uint64_t len;
 	int fin;
+
+	/* for TX pointer into <buf> field.
+	 * for RX pointer into the packet buffer.
+	 */
 	const unsigned char *data;
 };
 

src/mux_quic.c

@@ -271,6 +271,7 @@ static int qcs_push_frame(struct qcs *qcs, struct buffer *payload, int fin, uint
 	struct buffer *buf = &qcs->tx.xprt_buf;
 	struct quic_enc_level *qel = &qcs->qcc->conn->qc->els[QUIC_TLS_ENC_LEVEL_APP];
 	int total = 0, to_xfer;
+	unsigned char *btail;
 
 	fprintf(stderr, "%s\n", __func__);
 
@@ -283,6 +284,8 @@ static int qcs_push_frame(struct qcs *qcs, struct buffer *payload, int fin, uint
 	if (!frm)
 		goto err;
 
+	/* store buffer end before transfering data for frm.stream.data */
+	btail = (unsigned char *)b_tail(buf);
 	total = b_force_xfer(buf, payload, to_xfer);
 	/* FIN is positioned only when the buffer has been totally emptied. */
 	fin = fin && !b_data(payload);
@@ -295,6 +298,7 @@ static int qcs_push_frame(struct qcs *qcs, struct buffer *payload, int fin, uint
 	}
 	frm->stream.qcs = (struct qcs *)qcs;
 	frm->stream.buf = buf;
+	frm->stream.data = btail;
 	frm->stream.id = qcs->by_id.key;
 	if (total) {
 		frm->type |= QUIC_STREAM_FRAME_TYPE_LEN_BIT;

src/quic_frame.c

@@ -501,8 +501,7 @@ static int quic_build_stream_frame(unsigned char **buf, const unsigned char *end
                                    struct quic_frame *frm, struct quic_conn *conn)
 {
 	struct quic_stream *stream = &frm->stream;
-	size_t offset, block1, block2;
-	struct buffer b;
+	const unsigned char *wrap;
 
 	if (!quic_enc_int(buf, end, stream->id) ||
 	    ((frm->type & QUIC_STREAM_FRAME_TYPE_OFF_BIT) && !quic_enc_int(buf, end, stream->offset.key)) ||
@@ -510,19 +509,19 @@ static int quic_build_stream_frame(unsigned char **buf, const unsigned char *end
 	     (!quic_enc_int(buf, end, stream->len) || end - *buf < stream->len)))
 		return 0;
 
-	/* Buffer copy */
-	b = *stream->buf;
-	offset = (frm->type & QUIC_STREAM_FRAME_TYPE_OFF_BIT) ?
-		stream->offset.key & (b_size(stream->buf) - 1): 0;
-	block1 = b_wrap(&b) - (b_orig(&b) + offset);
-	if (block1 > stream->len)
-		block1 = stream->len;
-	block2 = stream->len - block1;
-	memcpy(*buf, b_orig(&b) + offset, block1);
-	*buf += block1;
-	if (block2) {
-		memcpy(*buf, b_orig(&b), block2);
-		*buf += block2;
+	wrap = (const unsigned char *)b_wrap(stream->buf);
+	if (stream->data + stream->len > wrap) {
+		size_t to_copy = wrap - stream->data;
+		memcpy(*buf, stream->data, to_copy);
+		*buf += to_copy;
+
+		to_copy = stream->len - to_copy;
+		memcpy(*buf, b_orig(stream->buf), to_copy);
+		*buf += to_copy;
+	}
+	else {
+		memcpy(*buf, stream->data, stream->len);
+		*buf += stream->len;
 	}
 
 	return 1;

src/xprt_quic.c

@@ -4775,6 +4775,7 @@ static inline int qc_build_frms(struct list *l,
 			}
 			else {
 				struct quic_frame *new_cf;
+				struct buffer cf_buf;
 
 				new_cf = pool_zalloc(pool_head_quic_frame);
 				if (!new_cf) {
@@ -4796,9 +4797,12 @@ static inline int qc_build_frms(struct list *l,
 				LIST_APPEND(l, &new_cf->list);
 				cf->type |= QUIC_STREAM_FRAME_TYPE_OFF_BIT;
 				/* Consume <dlen> bytes of the current frame. */
+				cf_buf = b_make(b_orig(cf->stream.buf),
+				                b_size(cf->stream.buf),
+				                (char *)cf->stream.data - b_orig(cf->stream.buf), 0);
 				cf->stream.len -= dlen;
 				cf->stream.offset.key += dlen;
-				cf->stream.data += dlen;
+				cf->stream.data = (unsigned char *)b_peek(&cf_buf, dlen);
 			}
 			break;