/*
 * Copyright (C) Roman Arutyunyan
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef ngx_int_t (*ngx_http_v3_handler_pt)(ngx_connection_t *c, void *data,
    u_char ch);


typedef struct {
    ngx_http_v3_handler_pt          handler;
    void                           *data;
    ngx_int_t                       index;
} ngx_http_v3_uni_stream_t;


typedef struct {
    ngx_queue_t                     queue;
    uint64_t                        id;
    ngx_connection_t               *connection;
    ngx_uint_t                     *npushing;
} ngx_http_v3_push_t;


static void ngx_http_v3_keepalive_handler(ngx_event_t *ev);
static void ngx_http_v3_cleanup_session(void *data);
static void ngx_http_v3_close_uni_stream(ngx_connection_t *c);
static void ngx_http_v3_read_uni_stream_type(ngx_event_t *rev);
static void ngx_http_v3_uni_read_handler(ngx_event_t *rev);
static void ngx_http_v3_dummy_write_handler(ngx_event_t *wev);
static void ngx_http_v3_push_cleanup(void *data);
static ngx_connection_t *ngx_http_v3_get_uni_stream(ngx_connection_t *c,
    ngx_uint_t type);
static ngx_int_t ngx_http_v3_send_settings(ngx_connection_t *c);


ngx_int_t
ngx_http_v3_init_session(ngx_connection_t *c)
{
    ngx_connection_t          *pc;
    ngx_pool_cleanup_t        *cln;
    ngx_http_connection_t     *phc;
    ngx_http_v3_connection_t  *h3c;

    pc = c->quic->parent;
    phc = pc->data;

    if (phc->http3) {
        return NGX_OK;
    }

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 init session");

    h3c = ngx_pcalloc(pc->pool, sizeof(ngx_http_v3_connection_t));
    if (h3c == NULL) {
        return NGX_ERROR;
    }

    h3c->hc = *phc;
    h3c->hc.http3 = 1;
    h3c->max_push_id = (uint64_t) -1;

    ngx_queue_init(&h3c->blocked);
    ngx_queue_init(&h3c->pushing);

    h3c->keepalive.log = pc->log;
    h3c->keepalive.data = pc;
    h3c->keepalive.handler = ngx_http_v3_keepalive_handler;
    h3c->keepalive.cancelable = 1;

    cln = ngx_pool_cleanup_add(pc->pool, 0);
    if (cln == NULL) {
        return NGX_ERROR;
    }

    cln->handler = ngx_http_v3_cleanup_session;
    cln->data = h3c;

    pc->data = h3c;

    return ngx_http_v3_send_settings(c);
}


static void
ngx_http_v3_keepalive_handler(ngx_event_t *ev)
{
    ngx_connection_t  *c;

    c = ev->data;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 keepalive handler");

    ngx_quic_finalize_connection(c, NGX_HTTP_V3_ERR_NO_ERROR,
                                 "keepalive timeout");
}


static void
ngx_http_v3_cleanup_session(void *data)
{
    ngx_http_v3_connection_t  *h3c = data;

    if (h3c->keepalive.timer_set) {
        ngx_del_timer(&h3c->keepalive);
    }
}


void
ngx_http_v3_init_uni_stream(ngx_connection_t *c)
{
    ngx_http_v3_uni_stream_t  *us;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 init uni stream");

    c->quic->cancelable = 1;

    us = ngx_pcalloc(c->pool, sizeof(ngx_http_v3_uni_stream_t));
    if (us == NULL) {
        ngx_http_close_connection(c);
        return;
    }

    us->index = -1;

    c->data = us;

    c->read->handler = ngx_http_v3_read_uni_stream_type;
    c->write->handler = ngx_http_v3_dummy_write_handler;

    ngx_http_v3_read_uni_stream_type(c->read);
}


static void
ngx_http_v3_close_uni_stream(ngx_connection_t *c)
{
    ngx_pool_t                *pool;
    ngx_http_v3_connection_t  *h3c;
    ngx_http_v3_uni_stream_t  *us;

    us = c->data;
    h3c = c->quic->parent->data;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 close stream");

    if (us->index >= 0) {
        h3c->known_streams[us->index] = NULL;
    }

    c->destroyed = 1;

    pool = c->pool;

    ngx_close_connection(c);

    ngx_destroy_pool(pool);
}


static void
ngx_http_v3_read_uni_stream_type(ngx_event_t *rev)
{
    u_char                     ch;
    ssize_t                    n;
    ngx_int_t                  index, rc;
    ngx_connection_t          *c;
    ngx_http_v3_connection_t  *h3c;
    ngx_http_v3_uni_stream_t  *us;

    c = rev->data;
    us = c->data;
    h3c = c->quic->parent->data;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 read stream type");

    while (rev->ready) {

        n = c->recv(c, &ch, 1);

        if (n == NGX_AGAIN) {
            break;
        }

        if (n == 0) {
            rc = NGX_HTTP_V3_ERR_GENERAL_PROTOCOL_ERROR;
            goto failed;
        }

        if (n != 1) {
            rc = NGX_HTTP_V3_ERR_INTERNAL_ERROR;
            goto failed;
        }

        switch (ch) {

        case NGX_HTTP_V3_STREAM_ENCODER:

            ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                           "http3 encoder stream");

            index = NGX_HTTP_V3_STREAM_CLIENT_ENCODER;
            us->handler = ngx_http_v3_parse_encoder;
            n = sizeof(ngx_http_v3_parse_encoder_t);

            break;

        case NGX_HTTP_V3_STREAM_DECODER:

            ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                           "http3 decoder stream");

            index = NGX_HTTP_V3_STREAM_CLIENT_DECODER;
            us->handler = ngx_http_v3_parse_decoder;
            n = sizeof(ngx_http_v3_parse_decoder_t);

            break;

        case NGX_HTTP_V3_STREAM_CONTROL:

            ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                           "http3 control stream");

            index = NGX_HTTP_V3_STREAM_CLIENT_CONTROL;
            us->handler = ngx_http_v3_parse_control;
            n = sizeof(ngx_http_v3_parse_control_t);

            break;

        default:

            ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                           "http3 stream 0x%02xi", (ngx_int_t) ch);
            index = -1;
            n = 0;
        }

        if (index >= 0) {
            if (h3c->known_streams[index]) {
                ngx_log_error(NGX_LOG_INFO, c->log, 0, "stream exists");
                rc = NGX_HTTP_V3_ERR_STREAM_CREATION_ERROR;
                goto failed;
            }

            us->index = index;
            h3c->known_streams[index] = c;
        }

        if (n) {
            us->data = ngx_pcalloc(c->pool, n);
            if (us->data == NULL) {
                rc = NGX_HTTP_V3_ERR_INTERNAL_ERROR;
                goto failed;
            }
        }

        rev->handler = ngx_http_v3_uni_read_handler;
        ngx_http_v3_uni_read_handler(rev);
        return;
    }

    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
        rc = NGX_HTTP_V3_ERR_INTERNAL_ERROR;
        goto failed;
    }

    return;

failed:

    ngx_http_v3_finalize_connection(c, rc, "could not read stream type");
    ngx_http_v3_close_uni_stream(c);
}


static void
ngx_http_v3_uni_read_handler(ngx_event_t *rev)
{
    u_char                     buf[128];
    ssize_t                    n;
    ngx_int_t                  rc, i;
    ngx_connection_t          *c;
    ngx_http_v3_uni_stream_t  *us;

    c = rev->data;
    us = c->data;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 read handler");

    while (rev->ready) {

        n = c->recv(c, buf, sizeof(buf));

        if (n == NGX_ERROR) {
            rc = NGX_HTTP_V3_ERR_INTERNAL_ERROR;
            goto failed;
        }

        if (n == 0) {
            if (us->index >= 0) {
                rc = NGX_HTTP_V3_ERR_CLOSED_CRITICAL_STREAM;
                goto failed;
            }

            ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 read eof");
            ngx_http_v3_close_uni_stream(c);
            return;
        }

        if (n == NGX_AGAIN) {
            break;
        }

        if (us->handler == NULL) {
            continue;
        }

        for (i = 0; i < n; i++) {

            rc = us->handler(c, us->data, buf[i]);

            if (rc == NGX_DONE) {
                ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                               "http3 read done");
                ngx_http_v3_close_uni_stream(c);
                return;
            }

            if (rc > 0) {
                goto failed;
            }

            if (rc != NGX_AGAIN) {
                rc = NGX_HTTP_V3_ERR_GENERAL_PROTOCOL_ERROR;
                goto failed;
            }
        }
    }

    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
        rc = NGX_HTTP_V3_ERR_INTERNAL_ERROR;
        goto failed;
    }

    return;

failed:

    ngx_http_v3_finalize_connection(c, rc, "stream error");
    ngx_http_v3_close_uni_stream(c);
}


static void
ngx_http_v3_dummy_write_handler(ngx_event_t *wev)
{
    ngx_connection_t  *c;

    c = wev->data;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 dummy write handler");

    if (ngx_handle_write_event(wev, 0) != NGX_OK) {
        ngx_http_v3_finalize_connection(c, NGX_HTTP_V3_ERR_INTERNAL_ERROR,
                                        NULL);
        ngx_http_v3_close_uni_stream(c);
    }
}


/* XXX async & buffered stream writes */

ngx_connection_t *
ngx_http_v3_create_push_stream(ngx_connection_t *c, uint64_t push_id)
{
    u_char                    *p, buf[NGX_HTTP_V3_VARLEN_INT_LEN * 2];
    size_t                     n;
    ngx_connection_t          *sc;
    ngx_pool_cleanup_t        *cln;
    ngx_http_v3_push_t        *push;
    ngx_http_v3_connection_t  *h3c;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 create push stream id:%uL", push_id);

    sc = ngx_quic_open_stream(c, 0);
    if (sc == NULL) {
        return NULL;
    }

    p = buf;
    p = (u_char *) ngx_http_v3_encode_varlen_int(p, NGX_HTTP_V3_STREAM_PUSH);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p, push_id);
    n = p - buf;

    if (sc->send(sc, buf, n) != (ssize_t) n) {
        goto failed;
    }

    cln = ngx_pool_cleanup_add(sc->pool, sizeof(ngx_http_v3_push_t));
    if (cln == NULL) {
        goto failed;
    }

    h3c = c->quic->parent->data;
    h3c->npushing++;

    cln->handler = ngx_http_v3_push_cleanup;

    push = cln->data;
    push->id = push_id;
    push->connection = sc;
    push->npushing = &h3c->npushing;

    ngx_queue_insert_tail(&h3c->pushing, &push->queue);

    return sc;

failed:

    ngx_http_v3_close_uni_stream(sc);

    return NULL;
}


static void
ngx_http_v3_push_cleanup(void *data)
{
    ngx_http_v3_push_t  *push = data;

    ngx_queue_remove(&push->queue);
    (*push->npushing)--;
}


static ngx_connection_t *
ngx_http_v3_get_uni_stream(ngx_connection_t *c, ngx_uint_t type)
{
    u_char                     buf[NGX_HTTP_V3_VARLEN_INT_LEN];
    size_t                     n;
    ngx_int_t                  index;
    ngx_connection_t          *sc;
    ngx_http_v3_connection_t  *h3c;
    ngx_http_v3_uni_stream_t  *us;

    switch (type) {
    case NGX_HTTP_V3_STREAM_ENCODER:
        index = NGX_HTTP_V3_STREAM_SERVER_ENCODER;
        break;
    case NGX_HTTP_V3_STREAM_DECODER:
        index = NGX_HTTP_V3_STREAM_SERVER_DECODER;
        break;
    case NGX_HTTP_V3_STREAM_CONTROL:
        index = NGX_HTTP_V3_STREAM_SERVER_CONTROL;
        break;
    default:
        index = -1;
    }

    h3c = c->quic->parent->data;

    if (index >= 0) {
        if (h3c->known_streams[index]) {
            return h3c->known_streams[index];
        }
    }

    sc = ngx_quic_open_stream(c, 0);
    if (sc == NULL) {
        return NULL;
    }

    sc->quic->cancelable = 1;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 create uni stream, type:%ui", type);

    us = ngx_pcalloc(sc->pool, sizeof(ngx_http_v3_uni_stream_t));
    if (us == NULL) {
        goto failed;
    }

    us->index = index;

    sc->data = us;

    sc->read->handler = ngx_http_v3_uni_read_handler;
    sc->write->handler = ngx_http_v3_dummy_write_handler;

    if (index >= 0) {
        h3c->known_streams[index] = sc;
    }

    n = (u_char *) ngx_http_v3_encode_varlen_int(buf, type) - buf;

    if (sc->send(sc, buf, n) != (ssize_t) n) {
        goto failed;
    }

    return sc;

failed:

    ngx_http_v3_close_uni_stream(sc);

    return NULL;
}


static ngx_int_t
ngx_http_v3_send_settings(ngx_connection_t *c)
{
    u_char                    *p, buf[NGX_HTTP_V3_VARLEN_INT_LEN * 6];
    size_t                     n;
    ngx_connection_t          *cc;
    ngx_http_v3_srv_conf_t    *h3scf;
    ngx_http_v3_connection_t  *h3c;

    h3c = c->quic->parent->data;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 send settings");

    cc = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_CONTROL);
    if (cc == NULL) {
        return NGX_DECLINED;
    }

    h3scf = ngx_http_get_module_srv_conf(h3c->hc.conf_ctx, ngx_http_v3_module);

    n = ngx_http_v3_encode_varlen_int(NULL,
                                      NGX_HTTP_V3_PARAM_MAX_TABLE_CAPACITY);
    n += ngx_http_v3_encode_varlen_int(NULL, h3scf->max_table_capacity);
    n += ngx_http_v3_encode_varlen_int(NULL, NGX_HTTP_V3_PARAM_BLOCKED_STREAMS);
    n += ngx_http_v3_encode_varlen_int(NULL, h3scf->max_blocked_streams);

    p = (u_char *) ngx_http_v3_encode_varlen_int(buf,
                                                 NGX_HTTP_V3_FRAME_SETTINGS);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p, n);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p,
                                         NGX_HTTP_V3_PARAM_MAX_TABLE_CAPACITY);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p, h3scf->max_table_capacity);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p,
                                            NGX_HTTP_V3_PARAM_BLOCKED_STREAMS);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p, h3scf->max_blocked_streams);
    n = p - buf;

    if (cc->send(cc, buf, n) != (ssize_t) n) {
        goto failed;
    }

    return NGX_OK;

failed:

    ngx_http_v3_close_uni_stream(cc);

    return NGX_ERROR;
}


ngx_int_t
ngx_http_v3_send_goaway(ngx_connection_t *c, uint64_t id)
{
    u_char            *p, buf[NGX_HTTP_V3_VARLEN_INT_LEN * 3];
    size_t             n;
    ngx_connection_t  *cc;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 send goaway %uL", id);

    cc = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_CONTROL);
    if (cc == NULL) {
        return NGX_DECLINED;
    }

    n = ngx_http_v3_encode_varlen_int(NULL, id);
    p = (u_char *) ngx_http_v3_encode_varlen_int(buf, NGX_HTTP_V3_FRAME_GOAWAY);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p, n);
    p = (u_char *) ngx_http_v3_encode_varlen_int(p, id);
    n = p - buf;

    if (cc->send(cc, buf, n) != (ssize_t) n) {
        goto failed;
    }

    return NGX_OK;

failed:

    ngx_http_v3_close_uni_stream(cc);

    return NGX_ERROR;
}


ngx_int_t
ngx_http_v3_client_ref_insert(ngx_connection_t *c, ngx_uint_t dynamic,
    ngx_uint_t index, ngx_str_t *value)
{
    u_char            *p, buf[NGX_HTTP_V3_PREFIX_INT_LEN * 2];
    size_t             n;
    ngx_connection_t  *ec;

    ngx_log_debug3(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 client ref insert, %s[%ui] \"%V\"",
                   dynamic ? "dynamic" : "static", index, value);

    ec = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_ENCODER);
    if (ec == NULL) {
        return NGX_ERROR;
    }

    p = buf;

    *p = (dynamic ? 0x80 : 0xc0);
    p = (u_char *) ngx_http_v3_encode_prefix_int(p, index, 6);

    /* XXX option for huffman? */
    *p = 0;
    p = (u_char *) ngx_http_v3_encode_prefix_int(p, value->len, 7);

    n = p - buf;

    if (ec->send(ec, buf, n) != (ssize_t) n) {
        goto failed;
    }

    if (ec->send(ec, value->data, value->len) != (ssize_t) value->len) {
        goto failed;
    }

    return NGX_OK;

failed:

    ngx_http_v3_close_uni_stream(ec);

    return NGX_ERROR;
}


ngx_int_t
ngx_http_v3_client_insert(ngx_connection_t *c, ngx_str_t *name,
    ngx_str_t *value)
{
    u_char             buf[NGX_HTTP_V3_PREFIX_INT_LEN];
    size_t             n;
    ngx_connection_t  *ec;

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 client insert \"%V\":\"%V\"", name, value);

    ec = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_ENCODER);
    if (ec == NULL) {
        return NGX_ERROR;
    }

    /* XXX option for huffman? */
    buf[0] = 0x40;
    n = (u_char *) ngx_http_v3_encode_prefix_int(buf, name->len, 5) - buf;

    if (ec->send(ec, buf, n) != (ssize_t) n) {
        goto failed;
    }

    if (ec->send(ec, name->data, name->len) != (ssize_t) name->len) {
        goto failed;
    }

    /* XXX option for huffman? */
    buf[0] = 0;
    n = (u_char *) ngx_http_v3_encode_prefix_int(buf, value->len, 7) - buf;

    if (ec->send(ec, buf, n) != (ssize_t) n) {
        goto failed;
    }

    if (ec->send(ec, value->data, value->len) != (ssize_t) value->len) {
        goto failed;
    }

    return NGX_OK;

failed:

    ngx_http_v3_close_uni_stream(ec);

    return NGX_ERROR;
}


ngx_int_t
ngx_http_v3_client_set_capacity(ngx_connection_t *c, ngx_uint_t capacity)
{
    u_char             buf[NGX_HTTP_V3_PREFIX_INT_LEN];
    size_t             n;
    ngx_connection_t  *ec;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 client set capacity %ui", capacity);

    ec = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_ENCODER);
    if (ec == NULL) {
        return NGX_ERROR;
    }

    buf[0] = 0x20;
    n = (u_char *) ngx_http_v3_encode_prefix_int(buf, capacity, 5) - buf;

    if (ec->send(ec, buf, n) != (ssize_t) n) {
        ngx_http_v3_close_uni_stream(ec);
        return NGX_ERROR;
    }

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_client_duplicate(ngx_connection_t *c, ngx_uint_t index)
{
    u_char             buf[NGX_HTTP_V3_PREFIX_INT_LEN];
    size_t             n;
    ngx_connection_t  *ec;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 client duplicate %ui", index);

    ec = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_ENCODER);
    if (ec == NULL) {
        return NGX_ERROR;
    }

    buf[0] = 0;
    n = (u_char *) ngx_http_v3_encode_prefix_int(buf, index, 5) - buf;

    if (ec->send(ec, buf, n) != (ssize_t) n) {
        ngx_http_v3_close_uni_stream(ec);
        return NGX_ERROR;
    }

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_client_ack_header(ngx_connection_t *c, ngx_uint_t stream_id)
{
    u_char             buf[NGX_HTTP_V3_PREFIX_INT_LEN];
    size_t             n;
    ngx_connection_t  *dc;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 client ack header %ui", stream_id);

    dc = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_DECODER);
    if (dc == NULL) {
        return NGX_ERROR;
    }

    buf[0] = 0x80;
    n = (u_char *) ngx_http_v3_encode_prefix_int(buf, stream_id, 7) - buf;

    if (dc->send(dc, buf, n) != (ssize_t) n) {
        ngx_http_v3_close_uni_stream(dc);
        return NGX_ERROR;
    }

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_client_cancel_stream(ngx_connection_t *c, ngx_uint_t stream_id)
{
    u_char             buf[NGX_HTTP_V3_PREFIX_INT_LEN];
    size_t             n;
    ngx_connection_t  *dc;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 client cancel stream %ui", stream_id);

    dc = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_DECODER);
    if (dc == NULL) {
        return NGX_ERROR;
    }

    buf[0] = 0x40;
    n = (u_char *) ngx_http_v3_encode_prefix_int(buf, stream_id, 6) - buf;

    if (dc->send(dc, buf, n) != (ssize_t) n) {
        ngx_http_v3_close_uni_stream(dc);
        return NGX_ERROR;
    }

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_client_inc_insert_count(ngx_connection_t *c, ngx_uint_t inc)
{
    u_char             buf[NGX_HTTP_V3_PREFIX_INT_LEN];
    size_t             n;
    ngx_connection_t  *dc;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 client increment insert count %ui", inc);

    dc = ngx_http_v3_get_uni_stream(c, NGX_HTTP_V3_STREAM_DECODER);
    if (dc == NULL) {
        return NGX_ERROR;
    }

    buf[0] = 0;
    n = (u_char *) ngx_http_v3_encode_prefix_int(buf, inc, 6) - buf;

    if (dc->send(dc, buf, n) != (ssize_t) n) {
        ngx_http_v3_close_uni_stream(dc);
        return NGX_ERROR;
    }

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_set_max_push_id(ngx_connection_t *c, uint64_t max_push_id)
{
    ngx_http_v3_connection_t  *h3c;

    h3c = c->quic->parent->data;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 MAX_PUSH_ID:%uL", max_push_id);

    if (h3c->max_push_id != (uint64_t) -1 && max_push_id < h3c->max_push_id) {
        return NGX_HTTP_V3_ERR_ID_ERROR;
    }

    h3c->max_push_id = max_push_id;

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_cancel_push(ngx_connection_t *c, uint64_t push_id)
{
    ngx_queue_t               *q;
    ngx_http_request_t        *r;
    ngx_http_v3_push_t        *push;
    ngx_http_v3_connection_t  *h3c;

    h3c = c->quic->parent->data;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 CANCEL_PUSH:%uL", push_id);

    if (push_id >= h3c->next_push_id) {
        return NGX_HTTP_V3_ERR_ID_ERROR;
    }

    for (q = ngx_queue_head(&h3c->pushing);
         q != ngx_queue_sentinel(&h3c->pushing);
         q = ngx_queue_next(&h3c->pushing))
    {
        push = (ngx_http_v3_push_t *) q;

        if (push->id != push_id) {
            continue;
        }

        r = push->connection->data;

        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                       "http3 cancel push");

        ngx_http_finalize_request(r, NGX_HTTP_CLOSE);

        break;
    }

    return NGX_OK;
}