/* Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include <apr_strings.h>

#include <httpd.h>

#include <http_core.h>

#include <http_connection.h>

#include <http_protocol.h>

#include <http_log.h>

#include "h2_private.h"

#include "h2_alt_svc.h"

#include "h2_ctx.h"

#include "h2_config.h"

#include "h2_h2.h"

#include "h2_util.h"

static int h2_alt_svc_handler(request_rec *r);

void h2_alt_svc_register_hooks(void)

{

    ap_hook_post_read_request(h2_alt_svc_handler, NULL, NULL, APR_HOOK_MIDDLE);

}

/**

 * Parse an Alt-Svc specifier as described in "HTTP Alternative Services"

 * (https://tools.ietf.org/html/draft-ietf-httpbis-alt-svc-04)

 * with the following changes:

 * - do not percent encode token values

 * - do not use quotation marks

 */

h2_alt_svc *h2_alt_svc_parse(const char *s, apr_pool_t *pool)

{

    const char *sep = ap_strchr_c(s, '=');

    if (sep) {

        const char *alpn = apr_pstrmemdup(pool, s, sep - s);

        const char *host = NULL;

        int port = 0;

        s = sep + 1;

        sep = ap_strchr_c(s, ':');  /* mandatory : */

        if (sep) {

            if (sep != s) {    /* optional host */

                host = apr_pstrmemdup(pool, s, sep - s);

            }

            s = sep + 1;

            if (*s) {          /* must be a port number */

                port = (int)apr_atoi64(s);

                if (port > 0 && port < (0x1 << 16)) {

                    h2_alt_svc *as = apr_pcalloc(pool, sizeof(*as));

                    as->alpn = alpn;

                    as->host = host;

                    as->port = port;

                    return as;

                }

            }

        }

    }

    return NULL;

}

#define h2_alt_svc_IDX(list, i) ((h2_alt_svc**)(list)->elts)[i]

static int h2_alt_svc_handler(request_rec *r)

{

    const h2_config *cfg;

    int i;

    if (r->connection->keepalives > 0) {

        /* Only announce Alt-Svc on the first response */

        return DECLINED;

    }

    if (h2_ctx_rget(r)) {

        return DECLINED;

    }

    cfg = h2_config_sget(r->server);

    if (r->hostname && cfg && cfg->alt_svcs && cfg->alt_svcs->nelts > 0) {

        const char *alt_svc_used = apr_table_get(r->headers_in, "Alt-Svc-Used");

        if (!alt_svc_used) {

            /* We have alt-svcs defined and client is not already using

             * one, announce the services that were configured and match. 

             * The security of this connection determines if we allow

             * other host names or ports only.

             */

            const char *alt_svc = "";

            const char *svc_ma = "";

            int secure = h2_h2_is_tls(r->connection);

            int ma = h2_config_geti(cfg, H2_CONF_ALT_SVC_MAX_AGE);

            if (ma >= 0) {

                svc_ma = apr_psprintf(r->pool, "; ma=%d", ma);

            }

            ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(03043)

                          "h2_alt_svc: announce %s for %s:%d", 

                          (secure? "secure" : "insecure"), 

                          r->hostname, (int)r->server->port);

            for (i = 0; i < cfg->alt_svcs->nelts; ++i) {

                h2_alt_svc *as = h2_alt_svc_IDX(cfg->alt_svcs, i);

                const char *ahost = as->host;

                if (ahost && !apr_strnatcasecmp(ahost, r->hostname)) {

                    ahost = NULL;

                }

                if (secure || !ahost) {

                    alt_svc = apr_psprintf(r->pool, "%s%s%s=\"%s:%d\"%s", 

                                           alt_svc,

                                           (*alt_svc? ", " : ""), as->alpn,

                                           ahost? ahost : "", as->port,

                                           svc_ma);

                }

            }

            if (*alt_svc) {

                apr_table_setn(r->headers_out, "Alt-Svc", alt_svc);

            }

        }

    }

    return DECLINED;

}