From: Amaury Denoyelle <adenoyelle@haproxy.com>
Date: Thu, 12 Jan 2023 13:53:43 +0000 (+0100)
Subject: MINOR: h3: implement TRAILERS encoding
X-Git-Tag: v2.8-dev2~15
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4e52010e576efe02f08ebfc2c6e0dbd593d3f405;p=thirdparty%2Fhaproxy.git

MINOR: h3: implement TRAILERS encoding

This patch implement the conversion of an HTX response containing
trailer into a H3 HEADERS frame. This is done through a new function
named h3_resp_trailers_send().

This was tested with a nginx configuration using <add_trailer>
statement.

It may be possible that HTX buffer only contains a EOT block without
preceeding trailer. In this case, the conversion will produce nothing
but fin will be reported. This causes QUIC mux to generate an empty
STREAM frame with FIN bit set.

This should be backported up to 2.7.
---

diff --git a/src/h3.c b/src/h3.c
index f30b3d9c7d..535fa6e1a1 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -1199,6 +1199,127 @@ static int h3_resp_headers_send(struct qcs *qcs, struct htx *htx)
 	return 0;
 }
 
+/* Convert a series of HTX trailer blocks from <htx> buffer into <qcs> buffer
+ * as a H3 HEADERS frame. H3 forbidden trailers are skipped. HTX trailer blocks
+ * are removed from <htx> until EOT is found and itself removed.
+ *
+ * If only a EOT HTX block is present without trailer, no H3 frame is produced.
+ * Caller is responsible to emit an empty QUIC STREAM frame to signal the end
+ * of the stream.
+ *
+ * Returns the size of HTX blocks removed.
+ */
+static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
+{
+	struct buffer headers_buf = BUF_NULL;
+	struct buffer *res;
+	struct http_hdr list[global.tune.max_http_hdr];
+	struct htx_blk *blk;
+	enum htx_blk_type type;
+	char *tail;
+	int ret = 0;
+	int hdr;
+
+	TRACE_ENTER(H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+
+	hdr = 0;
+	for (blk = htx_get_head_blk(htx); blk; blk = htx_get_next_blk(htx, blk)) {
+		type = htx_get_blk_type(blk);
+
+		if (type == HTX_BLK_UNUSED)
+			continue;
+
+		if (type == HTX_BLK_EOT)
+			break;
+
+		if (type == HTX_BLK_TLR) {
+			if (unlikely(hdr >= sizeof(list) / sizeof(list[0]) - 1))
+				goto err;
+			list[hdr].n = htx_get_blk_name(htx, blk);
+			list[hdr].v = htx_get_blk_value(htx, blk);
+			hdr++;
+		}
+		else {
+			TRACE_ERROR("unexpected HTX block", H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+			goto err;
+		}
+	}
+
+	list[hdr].n = ist("");
+
+	res = mux_get_buf(qcs);
+
+	/* At least 9 bytes to store frame type + length as a varint max size */
+	if (b_room(res) < 9) {
+		qcs->flags |= QC_SF_BLK_MROOM;
+		goto err;
+	}
+
+	/* Force buffer realignment as size required to encode headers is unknown. */
+	if (b_space_wraps(res))
+		b_slow_realign(res, trash.area, b_data(res));
+	/* Start the headers after frame type + length */
+	headers_buf = b_make(b_peek(res, b_data(res) + 9), b_contig_space(res) - 9, 0, 0);
+
+	if (qpack_encode_field_section_line(&headers_buf))
+		ABORT_NOW();
+
+	tail = b_tail(&headers_buf);
+	for (hdr = 0; hdr < sizeof(list) / sizeof(list[0]); ++hdr) {
+		if (isteq(list[hdr].n, ist("")))
+			break;
+
+		/* forbidden HTTP/3 headers, cf h3_resp_headers_send() */
+		if (isteq(list[hdr].n, ist("host")) ||
+		    isteq(list[hdr].n, ist("content-length")) ||
+		    isteq(list[hdr].n, ist("connection")) ||
+		    isteq(list[hdr].n, ist("proxy-connection")) ||
+		    isteq(list[hdr].n, ist("keep-alive")) ||
+		    isteq(list[hdr].n, ist("te")) ||
+		    isteq(list[hdr].n, ist("transfer-encoding"))) {
+			continue;
+		}
+
+		if (qpack_encode_header(&headers_buf, list[hdr].n, list[hdr].v))
+			ABORT_NOW();
+	}
+
+	/* Now that all headers are encoded, we are certain that res buffer is
+	 * big enough.
+	 */
+
+	/* Check that at least one header was encoded in buffer. */
+	if (b_tail(&headers_buf) != tail) {
+		b_putchr(res, 0x01); /* h3 HEADERS frame type */
+		if (!b_quic_enc_int(res, b_data(&headers_buf), 8))
+			ABORT_NOW();
+		b_add(res, b_data(&headers_buf));
+	}
+	else  {
+		/* No headers encoded here so no need to generate a H3 HEADERS
+		 * frame. Mux will send an empty QUIC STREAM frame with FIN.
+		 */
+		TRACE_DATA("skipping trailer", H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+	}
+
+	ret = 0;
+	blk = htx_get_head_blk(htx);
+	while (blk) {
+		type = htx_get_blk_type(blk);
+		ret += htx_get_blksz(blk);
+		blk = htx_remove_blk(htx, blk);
+		if (type == HTX_BLK_EOT)
+			break;
+	}
+
+	TRACE_LEAVE(H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+	return ret;
+
+ err:
+	TRACE_DEVEL("leaving on error", H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+	return 0;
+}
+
 /* Returns the total of bytes sent. */
 static int h3_resp_data_send(struct qcs *qcs, struct htx *htx, size_t count)
 {
@@ -1316,7 +1437,14 @@ static size_t h3_snd_buf(struct qcs *qcs, struct htx *htx, size_t count)
 
 		case HTX_BLK_TLR:
 		case HTX_BLK_EOT:
-			/* TODO trailers */
+			ret = h3_resp_trailers_send(qcs, htx);
+			if (ret > 0) {
+				total += ret;
+				count -= ret;
+				if (ret < bsize)
+					goto out;
+			}
+			break;
 
 		default:
 			htx_remove_blk(htx, blk);