MINOR: h3: Add HTTP/3 definitions.

Add all the definitions for HTTP/3 implementation.
diff --git a/include/haproxy/h3.h b/include/haproxy/h3.h
new file mode 100644
index 0000000..67ead4c
--- /dev/null
+++ b/include/haproxy/h3.h
@@ -0,0 +1,97 @@
+/*
+ * include/haproxy/h3.h
+ * This file containts types for H3
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef _HAPROXY_H3_T_H
+#define _HAPROXY_H3_T_H
+#ifdef USE_QUIC
+#ifndef USE_OPENSSL
+#error "Must define USE_OPENSSL"
+#endif
+
+#include <haproxy/buf-t.h>
+#include <haproxy/mux_quic-t.h>
+
+/* H3 unidirectional stream types (does not exist for bidirectional streams) */
+#define H3_UNI_STRM_TP_CONTROL_STREAM 0x00
+#define H3_UNI_STRM_TP_PUSH_STREAM    0x01
+#define H3_UNI_STRM_TP_QPACK_ENCODER  0x02
+#define H3_UNI_STRM_TP_QPACK_DECODER  0x03
+/* Must be the last one */
+#define H3_UNI_STRM_TP_MAX            H3_UNI_STRM_TP_QPACK_DECODER
+
+/* Settings */
+#define H3_SETTINGS_QPACK_MAX_TABLE_CAPACITY 0x01
+/* there is a hole here of reserved settings, matching the h2 settings */
+#define H3_SETTINGS_RESERVED_2               0x02
+#define H3_SETTINGS_RESERVED_3               0x03
+#define H3_SETTINGS_RESERVED_4               0x04
+#define H3_SETTINGS_RESERVED_5               0x05
+#define H3_SETTINGS_MAX_FIELD_SECTION_SIZE   0x06
+#define H3_SETTINGS_QPACK_BLOCKED_STREAMS    0x07
+
+/* Errors. */
+enum h3_err {
+	H3_NO_ERROR                = 0x100,
+	H3_GENERAL_PROTOCOL_ERROR  = 0x101,
+	H3_INTERNAL_ERROR          = 0x102,
+	H3_STREAM_CREATION_ERROR   = 0x103,
+	H3_CLOSED_CRITICAL_STREAM  = 0x104,
+	H3_FRAME_UNEXPECTED        = 0x105,
+	H3_FRAME_ERROR             = 0x106,
+	H3_EXCESSIVE_LOAD          = 0x107,
+	H3_ID_ERROR                = 0x108,
+	H3_SETTINGS_ERROR          = 0x109,
+	H3_MISSING_SETTINGS        = 0x10a,
+	H3_REQUEST_REJECTED        = 0x10b,
+	H3_REQUEST_CANCELLED       = 0x10c,
+	H3_REQUEST_INCOMPLETE      = 0x10d,
+	H3_MESSAGE_ERROR           = 0x10e,
+	H3_CONNECT_ERROR           = 0x10f,
+	H3_VERSION_FALLBACK        = 0x110,
+
+	QPACK_DECOMPRESSION_FAILED = 0x200,
+	QPACK_ENCODER_STREAM_ERROR = 0x201,
+	QPACK_DECODER_STREAM_ERROR = 0x202,
+};
+
+/* Frame types. */
+enum h3_ft       {
+	H3_FT_DATA         = 0x00,
+	H3_FT_HEADERS      = 0x01,
+	/* There is a hole here */
+	H3_FT_CANCEL_PUSH  = 0x03,
+	H3_FT_SETTINGS     = 0x04,
+	H3_FT_PUSH_PROMISE = 0x05,
+	H3_FT_GOAWAY       = 0x06,
+	H3_FT_MAX_PUSH_ID  = 0x07,
+};
+
+/* H3 unidirectional QUIC stream */
+struct h3_uqs {
+	/* Underlying incoming QUIC uni-stream */
+	struct qcs *qcs;
+	/* Callback to tx/rx bytes */
+	int (*cb)(struct h3_uqs *h3_uqs, void *ctx);
+	struct wait_event wait_event;
+};
+
+extern const struct qcc_app_ops h3_ops;
+
+#endif /* USE_QUIC */
+#endif /* _HAPROXY_H3_T_H */
diff --git a/src/h3.c b/src/h3.c
new file mode 100644
index 0000000..550f932
--- /dev/null
+++ b/src/h3.c
@@ -0,0 +1,555 @@
+/*
+ * HTTP/3 protocol processing
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <haproxy/buf.h>
+#include <haproxy/dynbuf.h>
+#include <haproxy/h3.h>
+#include <haproxy/istbuf.h>
+#include <haproxy/mux_quic.h>
+#include <haproxy/pool.h>
+#include <haproxy/qpack-dec.h>
+#include <haproxy/tools.h>
+#include <haproxy/xprt_quic.h>
+
+#define DEBUG_H3
+
+#if defined(DEBUG_H3)
+#define h3_debug_printf fprintf
+#define h3_debug_hexdump debug_hexdump
+#else
+#define h3_debug_printf(...) do { } while (0)
+#define h3_debug_hexdump(...) do { } while (0)
+#endif
+
+#define H3_CF_SETTINGS_SENT  0x00000001
+
+/* Default settings */
+static uint64_t h3_settings_qpack_max_table_capacity = 4096;
+static uint64_t h3_settings_qpack_blocked_streams = 100;
+static uint64_t h3_settings_max_field_section_size; /* Unlimited */
+
+struct h3 {
+	struct qcc *qcc;
+	enum h3_err err;
+	uint32_t flags;
+	/* Locally initiated uni-streams */
+	struct h3_uqs lqpack_enc;
+	struct h3_uqs lqpack_dec;
+	struct h3_uqs lctrl;
+	/* Remotely initiated uni-streams */
+	struct h3_uqs rqpack_enc;
+	struct h3_uqs rqpack_dec;
+	struct h3_uqs rctrl;
+	/* Settings */
+	uint64_t qpack_max_table_capacity;
+	uint64_t qpack_blocked_streams;
+	uint64_t max_field_section_size;
+	struct buffer_wait buf_wait; /* wait list for buffer allocations */
+};
+
+DECLARE_STATIC_POOL(pool_head_h3, "h3", sizeof(struct h3));
+
+/* Simple function to duplicate a buffer */
+static inline struct buffer h3_b_dup(struct buffer *b)
+{
+	return b_make(b->area, b->size, b->head, b->data);
+}
+
+static int qcs_buf_available(void *target)
+{
+	struct h3_uqs *h3_uqs = target;
+	struct qcs *qcs = h3_uqs->qcs;
+
+	if ((qcs->flags & OUQS_SF_TXBUF_MALLOC) && b_alloc(&qcs->tx.buf)) {
+		qcs->flags &= ~OUQS_SF_TXBUF_MALLOC;
+		tasklet_wakeup(h3_uqs->wait_event.tasklet);
+		return 1;
+	}
+
+	return 0;
+}
+
+static struct buffer *h3_uqs_get_buf(struct h3_uqs *h3_uqs)
+{
+	struct buffer *buf = NULL;
+	struct h3 *h3 = h3_uqs->qcs->qcc->ctx;
+
+	if (likely(!LIST_INLIST(&h3->buf_wait.list)) &&
+	    unlikely((buf = b_alloc(&h3_uqs->qcs->tx.buf)) == NULL)) {
+		h3->buf_wait.target = h3_uqs;
+		h3->buf_wait.wakeup_cb = qcs_buf_available;
+		LIST_APPEND(&ti->buffer_wq, &h3->buf_wait.list);
+	}
+
+	return buf;
+}
+
+/* Decode a h3 frame header made of two QUIC varints from <b> buffer.
+ * Returns the number of bytes consumed if there was enough data in <b>, 0 if not.
+ * Note that this function update <b> buffer to reflect the number of bytes consumed
+ * to decode the h3 frame header.
+ */
+static inline size_t h3_decode_frm_header(uint64_t *ftype, uint64_t *flen,
+                                          struct buffer *b)
+{
+	size_t hlen;
+
+	hlen = 0;
+	if (!b_quic_dec_int(ftype, b, &hlen) || !b_quic_dec_int(flen, b, &hlen))
+		return 0;
+
+	return hlen;
+}
+
+/* Decode <qcs> remotely initiated bidi-stream */
+static int h3_decode_qcs(struct qcs *qcs, void *ctx)
+{
+	struct buffer *rxbuf = &qcs->rx.buf;
+	struct h3 *h3 = ctx;
+
+	h3_debug_printf(stderr, "%s: STREAM ID: %llu\n", __func__, qcs->by_id.key);
+	if (!b_data(rxbuf))
+		return 0;
+
+	while (b_data(rxbuf)) {
+		size_t hlen;
+		uint64_t ftype, flen;
+		struct buffer b;
+
+		/* Work on a copy of <rxbuf> */
+		b = h3_b_dup(rxbuf);
+		hlen = h3_decode_frm_header(&ftype, &flen, &b);
+		if (!hlen)
+			break;
+
+		h3_debug_printf(stderr, "%s: ftype: %llu, flen: %llu\n", __func__,
+		        (unsigned long long)ftype, (unsigned long long)flen);
+		if (flen > b_data(&b))
+			break;
+
+		b_del(rxbuf, hlen);
+		switch (ftype) {
+		case H3_FT_DATA:
+			break;
+		case H3_FT_HEADERS:
+		{
+			const unsigned char *buf = (const unsigned char *)b_head(rxbuf);
+			size_t len = b_data(rxbuf);
+			struct buffer *tmp = get_trash_chunk();
+
+			if (qpack_decode_fs(buf, len, tmp) < 0) {
+				h3->err = QPACK_DECOMPRESSION_FAILED;
+				return -1;
+			}
+			break;
+		}
+		case H3_FT_PUSH_PROMISE:
+			/* Not supported */
+			break;
+		default:
+			/* Error */
+			h3->err = H3_FRAME_UNEXPECTED;
+			return -1;
+		}
+		b_del(rxbuf, flen);
+	}
+
+	return 1;
+}
+
+/* Parse a SETTINGS frame which must not be truncated with <flen> as length from
+ * <rxbuf> buffer. This function does not update this buffer.
+ * Returns 0 if something wrong happened, 1 if not.
+ */
+static int h3_parse_settings_frm(struct h3 *h3, const struct buffer *rxbuf, size_t flen)
+{
+	uint64_t id, value;
+	const unsigned char *buf, *end;
+
+	buf = (const unsigned char *)b_head(rxbuf);
+	end = buf + flen;
+
+	while (buf <= end) {
+		if (!quic_dec_int(&id, &buf, end) || !quic_dec_int(&value, &buf, end))
+			return 0;
+
+		h3_debug_printf(stderr, "%s id: %llu value: %llu\n",
+		                __func__, (unsigned long long)id, (unsigned long long)value);
+		switch (id) {
+		case H3_SETTINGS_QPACK_MAX_TABLE_CAPACITY:
+			h3->qpack_max_table_capacity = value;
+			break;
+		case H3_SETTINGS_MAX_FIELD_SECTION_SIZE:
+			h3->max_field_section_size = value;
+			break;
+		case H3_SETTINGS_QPACK_BLOCKED_STREAMS:
+			h3->qpack_blocked_streams = value;
+			break;
+		case H3_SETTINGS_RESERVED_2 ... H3_SETTINGS_RESERVED_5:
+			h3->err = H3_SETTINGS_ERROR;
+			return 0;
+		default:
+			/* MUST be ignored */
+			break;
+		}
+	}
+
+	return 1;
+}
+
+/* Decode <qcs> remotely initiated uni-stream. We stop parsing a frame as soon as
+ * there is not enough received data.
+ * Returns 0 if something wrong happened, 1 if not.
+ */
+static int h3_control_recv(struct h3_uqs *h3_uqs, void *ctx)
+{
+	struct buffer *rxbuf = &h3_uqs->qcs->rx.buf;
+	struct h3 *h3 = ctx;
+
+	h3_debug_printf(stderr, "%s STREAM ID: %llu\n", __func__,  h3_uqs->qcs->by_id.key);
+	if (!b_data(rxbuf))
+		return 1;
+
+	while (b_data(rxbuf)) {
+		size_t hlen;
+		uint64_t ftype, flen;
+		struct buffer b;
+
+		/* Work on a copy of <rxbuf> */
+		b = h3_b_dup(rxbuf);
+		hlen = h3_decode_frm_header(&ftype, &flen, &b);
+		if (!hlen)
+			break;
+
+		h3_debug_printf(stderr, "%s: ftype: %llu, flen: %llu\n", __func__,
+		        (unsigned long long)ftype, (unsigned long long)flen);
+		if (flen > b_data(&b))
+			break;
+
+		b_del(rxbuf, hlen);
+		/* From here, a frame must not be truncated */
+		switch (ftype) {
+		case H3_FT_CANCEL_PUSH:
+			break;
+		case H3_FT_SETTINGS:
+			if (!h3_parse_settings_frm(h3, rxbuf, flen))
+				return 0;
+			break;
+		case H3_FT_GOAWAY:
+			break;
+		case H3_FT_MAX_PUSH_ID:
+			break;
+		default:
+			/* Error */
+			h3->err = H3_FRAME_UNEXPECTED;
+			return 0;
+		}
+		b_del(rxbuf, flen);
+	}
+
+	if (b_data(rxbuf))
+		h3->qcc->conn->mux->ruqs_subscribe(h3_uqs->qcs, SUB_RETRY_RECV, &h3->rctrl.wait_event);
+
+	return 1;
+}
+
+int h3_txbuf_cpy(struct h3_uqs *h3_uqs, unsigned char *buf, size_t len)
+{
+	struct buffer *res = &h3_uqs->qcs->tx.buf;
+	struct qcc *qcc = h3_uqs->qcs->qcc;
+	int ret;
+
+	ret = 0;
+	if (!h3_uqs_get_buf(h3_uqs)) {
+		qcc->flags |= OUQS_SF_TXBUF_MALLOC;
+		goto out;
+	}
+
+	ret = b_istput(res, ist2((char *)buf, len));
+	if (unlikely(!ret))
+		qcc->flags |= OUQS_SF_TXBUF_FULL;
+
+ out:
+	return ret;
+}
+
+/* Function used to emit stream data from <h3_uqs> control uni-stream */
+static int h3_control_send(struct h3_uqs *h3_uqs, void *ctx)
+{
+	int ret;
+	struct h3 *h3 = ctx;
+	unsigned char data[(2 + 3) * 2 * QUIC_VARINT_MAX_SIZE]; /* enough for 3 settings */
+	unsigned char *pos, *end;
+
+	ret = 0;
+	pos = data;
+	end = pos + sizeof data;
+	if (!(h3->flags & H3_CF_SETTINGS_SENT)) {
+		struct qcs *qcs = h3_uqs->qcs;
+		struct buffer *txbuf = &qcs->tx.buf;
+		size_t frm_len;
+
+		frm_len = quic_int_getsize(H3_SETTINGS_QPACK_MAX_TABLE_CAPACITY) +
+			quic_int_getsize(h3_settings_qpack_max_table_capacity) +
+			quic_int_getsize(H3_SETTINGS_QPACK_BLOCKED_STREAMS) +
+			quic_int_getsize(h3_settings_qpack_blocked_streams);
+		if (h3_settings_max_field_section_size) {
+			frm_len += quic_int_getsize(H3_SETTINGS_MAX_FIELD_SECTION_SIZE) +
+			quic_int_getsize(h3_settings_max_field_section_size);
+		}
+
+		quic_enc_int(&pos, end, H3_UNI_STRM_TP_CONTROL_STREAM);
+		/* Build a SETTINGS frame */
+		quic_enc_int(&pos, end, H3_FT_SETTINGS);
+		quic_enc_int(&pos, end, frm_len);
+		quic_enc_int(&pos, end, H3_SETTINGS_QPACK_MAX_TABLE_CAPACITY);
+		quic_enc_int(&pos, end, h3_settings_qpack_max_table_capacity);
+		quic_enc_int(&pos, end, H3_SETTINGS_QPACK_BLOCKED_STREAMS);
+		quic_enc_int(&pos, end, h3_settings_qpack_blocked_streams);
+		if (h3_settings_max_field_section_size) {
+			quic_enc_int(&pos, end, H3_SETTINGS_MAX_FIELD_SECTION_SIZE);
+			quic_enc_int(&pos, end, h3_settings_max_field_section_size);
+		}
+		ret = h3_txbuf_cpy(h3_uqs, data, pos - data);
+		if (ret < 0) {
+			qc_error(qcs->qcc, H3_INTERNAL_ERROR);
+			return ret;
+		}
+
+		if (ret > 0) {
+			h3->flags |= H3_CF_SETTINGS_SENT;
+			luqs_snd_buf(h3_uqs->qcs, txbuf, b_data(&qcs->tx.buf), 0);
+		}
+		if (b_data(&qcs->tx.buf))
+			qcs->qcc->conn->mux->luqs_subscribe(qcs, SUB_RETRY_SEND, &h3->lctrl.wait_event);
+	}
+
+	return ret;
+}
+
+/* Finalize the initialization of remotely initiated uni-stream <qcs>.
+ * Return 1 if succeeded, 0 if not. In this latter case, set the ->err h3 error
+ * to inform the QUIC mux layer of the encountered error.
+ */
+static int h3_attach_ruqs(struct qcs *qcs, void *ctx)
+{
+	uint64_t strm_type;
+	struct h3 *h3 = ctx;
+	struct buffer *rxbuf = &qcs->rx.buf;
+
+	/* First octets: the uni-stream type */
+	if (!b_quic_dec_int(&strm_type, rxbuf, NULL) || strm_type > H3_UNI_STRM_TP_MAX)
+		return 0;
+
+	/* Note that for all the uni-streams below, this is an error to receive two times the
+	 * same type of uni-stream (even for Push stream which is not supported at this time.
+	 */
+	switch (strm_type) {
+	case H3_UNI_STRM_TP_CONTROL_STREAM:
+		if (h3->rctrl.qcs) {
+			h3->err = H3_STREAM_CREATION_ERROR;
+			return 0;
+		}
+
+		h3->rctrl.qcs = qcs;
+		h3->rctrl.cb = h3_control_recv;
+		h3->qcc->conn->mux->ruqs_subscribe(qcs, SUB_RETRY_RECV, &h3->rctrl.wait_event);
+		break;
+	case H3_UNI_STRM_TP_PUSH_STREAM:
+		/* NOT SUPPORTED */
+		break;
+	case H3_UNI_STRM_TP_QPACK_ENCODER:
+		if (h3->rqpack_enc.qcs) {
+			h3->err = H3_STREAM_CREATION_ERROR;
+			return 0;
+		}
+
+		h3->rqpack_enc.qcs = qcs;
+		h3->rqpack_enc.cb = qpack_decode_enc;
+		h3->qcc->conn->mux->ruqs_subscribe(qcs, SUB_RETRY_RECV, &h3->rqpack_enc.wait_event);
+		break;
+	case H3_UNI_STRM_TP_QPACK_DECODER:
+		if (h3->rqpack_dec.qcs) {
+			h3->err = H3_STREAM_CREATION_ERROR;
+			return 0;
+		}
+
+		h3->rqpack_dec.qcs = qcs;
+		h3->rqpack_dec.cb = qpack_decode_dec;
+		h3->qcc->conn->mux->ruqs_subscribe(qcs, SUB_RETRY_RECV, &h3->rqpack_dec.wait_event);
+		break;
+	default:
+		/* Error */
+		h3->err = H3_STREAM_CREATION_ERROR;
+		return 0;
+	}
+
+	return 1;
+}
+
+static int h3_finalize(void *ctx)
+{
+	struct h3 *h3 = ctx;
+
+	h3->lctrl.qcs = luqs_new(h3->qcc);
+	if (!h3->lctrl.qcs)
+		return 0;
+
+	/* Wakeup ->lctrl uni-stream */
+	tasklet_wakeup(h3->lctrl.wait_event.tasklet);
+
+	return 1;
+}
+
+/* Tasklet dedicated to h3 incoming uni-streams */
+static struct task *h3_uqs_task(struct task *t, void *ctx, unsigned int state)
+{
+	struct h3_uqs *h3_uqs = ctx;
+	struct h3 *h3 = h3_uqs->qcs->qcc->ctx;
+
+	h3_uqs->cb(h3_uqs, h3);
+	return NULL;
+}
+
+#if 0
+/* Initialiaze <h3_uqs> uni-stream with <t> as tasklet */
+static int h3_uqs_init(struct h3_uqs *h3_uqs,
+                         struct task *(*t)(struct task *, void *, unsigned int))
+{
+	h3_uqs->qcs = NULL;
+	h3_uqs->cb = NULL;
+	h3_uqs->wait_event.tasklet = tasklet_new();
+	if (!h3_uqs->wait_event.tasklet)
+		return 0;
+
+	h3_uqs->wait_event.tasklet->process = t;
+	h3_uqs->wait_event.tasklet->context = h3_uqs;
+	return 1;
+}
+#endif
+
+/* Release all the tasklet attached to <h3_uqs> uni-stream */
+static inline void h3_uqs_tasklet_release(struct h3_uqs *h3_uqs)
+{
+	struct tasklet *t = h3_uqs->wait_event.tasklet;
+
+	if (t)
+		tasklet_free(t);
+}
+
+/* Release all the tasklet attached to <h3> uni-streams */
+static void h3_uqs_tasklets_release(struct h3 *h3)
+{
+	h3_uqs_tasklet_release(&h3->rqpack_enc);
+	h3_uqs_tasklet_release(&h3->rqpack_dec);
+	h3_uqs_tasklet_release(&h3->rctrl);
+}
+
+/* Tasklet dedicated to h3 outgoing uni-streams */
+__maybe_unused
+static struct task *h3_uqs_send_task(struct task *t, void *ctx, unsigned int state)
+{
+	struct h3_uqs *h3_uqs = ctx;
+	struct h3 *h3 = h3_uqs->qcs->qcc->ctx;
+
+	h3_uqs->cb(h3_uqs, h3);
+	return NULL;
+}
+
+/* Initialiaze <h3_uqs> uni-stream with <t> as tasklet */
+static int h3_uqs_init(struct h3_uqs *h3_uqs, struct h3 *h3,
+                       int (*cb)(struct h3_uqs *h3_uqs, void *ctx),
+                       struct task *(*t)(struct task *, void *, unsigned int))
+{
+	h3_uqs->qcs = NULL;
+	h3_uqs->cb = cb;
+	h3_uqs->wait_event.tasklet = tasklet_new();
+	if (!h3_uqs->wait_event.tasklet)
+		return 0;
+
+	h3_uqs->wait_event.tasklet->process = t;
+	h3_uqs->wait_event.tasklet->context = h3_uqs;
+	return 1;
+
+ err:
+	tasklet_free(h3_uqs->wait_event.tasklet);
+	return 0;
+}
+
+static inline void h3_uqs_release(struct h3_uqs *h3_uqs)
+{
+	if (h3_uqs->qcs)
+		qcs_release(h3_uqs->qcs);
+}
+
+static inline void h3_uqs_release_all(struct h3 *h3)
+{
+	h3_uqs_tasklet_release(&h3->lctrl);
+	h3_uqs_release(&h3->lctrl);
+	h3_uqs_tasklet_release(&h3->lqpack_enc);
+	h3_uqs_release(&h3->lqpack_enc);
+	h3_uqs_tasklet_release(&h3->lqpack_dec);
+	h3_uqs_release(&h3->lqpack_dec);
+}
+
+/* Initialize the HTTP/3 context for <qcc> mux.
+ * Return 1 if succeeded, 0 if not.
+ */
+static int h3_init(struct qcc *qcc)
+{
+	struct h3 *h3;
+
+	h3 = pool_alloc(pool_head_h3);
+	if (!h3)
+		goto fail_no_h3;
+
+	h3->qcc = qcc;
+	h3->err = H3_NO_ERROR;
+	h3->flags = 0;
+
+	if (!h3_uqs_init(&h3->rqpack_enc, h3, NULL, h3_uqs_task) ||
+	    !h3_uqs_init(&h3->rqpack_dec, h3, NULL, h3_uqs_task) ||
+	    !h3_uqs_init(&h3->rctrl, h3, h3_control_recv, h3_uqs_task))
+		goto fail_no_h3_ruqs;
+
+	if (!h3_uqs_init(&h3->lctrl, h3, h3_control_send, h3_uqs_task) ||
+	    !h3_uqs_init(&h3->lqpack_enc, h3, NULL, h3_uqs_task) ||
+	    !h3_uqs_init(&h3->lqpack_dec, h3, NULL, h3_uqs_task))
+		goto fail_no_h3_luqs;
+
+	qcc->ctx = h3;
+	LIST_INIT(&h3->buf_wait.list);
+
+	return 1;
+
+ fail_no_h3_ruqs:
+	h3_uqs_release_all(h3);
+ fail_no_h3_luqs:
+	h3_uqs_tasklets_release(h3);
+	pool_free(pool_head_h3, h3);
+ fail_no_h3:
+	return 0;
+}
+
+/* HTTP/3 application layer operations */
+const struct qcc_app_ops h3_ops = {
+	.init        = h3_init,
+	.attach_ruqs = h3_attach_ruqs,
+	.decode_qcs  = h3_decode_qcs,
+	.finalize    = h3_finalize,
+};