/* 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 "ap_config.h"
#include "ap_mmn.h"
#include "httpd.h"
#include "http_config.h"
#include "http_connection.h"
#include "http_protocol.h"
#include "http_log.h"
#include "apr_strings.h"
#define APR_WANT_BYTEFUNC
#include "apr_want.h"
#include "apr_network_io.h"

module AP_MODULE_DECLARE_DATA remoteip_module;

typedef struct {
    const char *remoteip_header;
} remoteip_config_t;

static void *create_remoteip_server_config(apr_pool_t *p, server_rec *s)
{
    remoteip_config_t *config = apr_palloc(p, sizeof *config);
    config->remoteip_header = NULL;
    return config;
}

static void *merge_remoteip_server_config(apr_pool_t *p, void *globalv,
                                          void *serverv)
{
    remoteip_config_t *global = (remoteip_config_t *) globalv;
    remoteip_config_t *server = (remoteip_config_t *) serverv;
    remoteip_config_t *config;

    config = (remoteip_config_t *) apr_palloc(p, sizeof(*config));
    if (server->remoteip_header)
        config->remoteip_header = server->remoteip_header;
    else
        config->remoteip_header = global->remoteip_header;
    return config;
}
 
static const char *remoteip_header_set(cmd_parms *cmd, void *dummy,
                                       const char *arg)
{
    remoteip_config_t *config = ap_get_module_config(cmd->server->module_config,
                                                     &remoteip_module);
    config->remoteip_header = apr_pstrdup(cmd->pool, arg);
    return NULL;
}

static int modify_connection(request_rec *r)
{
    conn_rec *c = r->connection;
    remoteip_config_t *config = ap_get_module_config(r->server->module_config,
                                                     &remoteip_module);
    char *remote;

    if (!config->remoteip_header) 
        return OK;

    remote = (char*)apr_table_get(r->headers_in, config->remoteip_header);
    if (!remote)
        return OK;

    /* Decode remote_addr - sucks; apr_sockaddr_vars_set isn't 'public' */
    if (inet_pton(AF_INET, remote, 
                  &c->remote_addr->sa.sin.sin_addr) > 0) {
        apr_sockaddr_vars_set(c->remote_addr, APR_INET, 0);
    }
#if APR_HAVE_IPV6
    else if (inet_pton(AF_INET6, remote, 
                       &c->remote_addr->sa.sin6.sin6_addr) > 0) {
        apr_sockaddr_vars_set(c->remote_addr, APR_INET6, 0);
    }
#endif
    else {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG,  apr_get_netos_error(), r,
                      "Header %s value of %s doesn't appear to be a client IP",
                      config->remoteip_header, remote);
        return OK;
    }

    /* Set remote_ip string */
    remote = apr_pstrdup(c->pool, remote);
    c->remote_ip = remote;

    /* Unset remote_host string DNS lookups */
    c->remote_host = NULL;
    c->remote_logname = NULL;

    ap_log_rerror(APLOG_MARK, APLOG_DEBUG|APLOG_NOERRNO, 0, r,
                  "Using header %s value %s as client's IP",
                  config->remoteip_header, remote);
    return OK;
}

static const command_rec remoteip_cmds[] =
{
    AP_INIT_TAKE1("RemoteIPHeader", remoteip_header_set, NULL, RSRC_CONF,
                  "Define the request-header to identify the remote IP."),
    { NULL }
};

static void register_hooks(apr_pool_t *p)
{
    ap_hook_post_read_request(modify_connection, NULL, NULL, APR_HOOK_FIRST);
}

module AP_MODULE_DECLARE_DATA remoteip_module = {
    STANDARD20_MODULE_STUFF,
    NULL,                          /* create per-directory config structure */
    NULL,                          /* merge per-directory config structures */
    create_remoteip_server_config, /* create per-server config structure */
    merge_remoteip_server_config,  /* merge per-server config structures */
    remoteip_cmds,                 /* command apr_table_t */
    register_hooks                 /* register hooks */
};