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/*
This file is part of GNUnet
Copyright (C) 2012 GNUnet e.V.
GNUnet is free software: you can redistribute it and/or modify it
under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License,
or (at your option) any later version.
GNUnet 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
Affero General Public License for more details.
*/
/**
* @author Christian Grothoff
*
* @file
* API to access the DNS service.
*
* @defgroup dns DNS service
*
* @see [Documentation](https://gnunet.org/gnunet-service-dns)
*
* @{
*/
#ifndef GNUNET_DNS_SERVICE_H
#define GNUNET_DNS_SERVICE_H
#include "gnunet_util_lib.h"
/**
* Opaque DNS handle
*/
struct GNUNET_DNS_Handle;
/**
* Handle to identify an individual DNS request.
*/
struct GNUNET_DNS_RequestHandle;
/**
* Flags that specify when to call the client's handler.
*/
enum GNUNET_DNS_Flags
{
/**
* Useless option: never call the client.
*/
GNUNET_DNS_FLAG_NEVER = 0,
/**
* Set this flag to see all requests first prior to resolution
* (for monitoring). Clients that set this flag must then
* call "GNUNET_DNS_request_forward" when they process a request
* for the first time. Caling "GNUNET_DNS_request_answer" is
* not allowed for MONITOR peers.
*/
GNUNET_DNS_FLAG_REQUEST_MONITOR = 1,
/**
* This client should be called on requests that have not
* yet been resolved as this client provides a resolution
* service. Note that this does not guarantee that the
* client will see all requests as another client might be
* called first and that client might have already done the
* resolution, in which case other pre-resolution clients
* won't see the request anymore.
*/
GNUNET_DNS_FLAG_PRE_RESOLUTION = 2,
/**
* This client wants to be called on the results of a DNS resolution
* (either resolved by PRE-RESOLUTION clients or the global DNS).
* The client then has a chance to modify the answer (or cause it to
* be dropped). There is no guarantee that other POST-RESOLUTION
* client's won't modify (or drop) the answer afterwards.
*/
GNUNET_DNS_FLAG_POST_RESOLUTION = 4,
/**
* Set this flag to see all requests just before they are
* returned to the network. Clients that set this flag must then
* call "GNUNET_DNS_request_forward" when they process a request
* for the last time. Caling "GNUNET_DNS_request_answer" is
* not allowed for MONITOR peers.
*/
GNUNET_DNS_FLAG_RESPONSE_MONITOR = 8
};
/**
* Signature of a function that is called whenever the DNS service
* encounters a DNS request and needs to do something with it. The
* function has then the chance to generate or modify the response by
* calling one of the three "GNUNET_DNS_request_*" continuations.
*
* When a request is intercepted, this function is called first to
* give the client a chance to do the complete address resolution;
* "rdata" will be NULL for this first call for a DNS request, unless
* some other client has already filled in a response.
*
* If multiple clients exist, all of them are called before the global
* DNS. The global DNS is only called if all of the clients'
* functions call GNUNET_DNS_request_forward. Functions that call
* GNUNET_DNS_request_forward will be called again before a final
* response is returned to the application. If any of the clients'
* functions call GNUNET_DNS_request_drop, the response is dropped.
*
* @param cls closure
* @param rh request handle to user for reply
* @param request_length number of bytes in request
* @param request udp payload of the DNS request
*/
typedef void
(*GNUNET_DNS_RequestHandler)(void *cls,
struct GNUNET_DNS_RequestHandle *rh,
size_t request_length,
const char *request);
/**
* If a GNUNET_DNS_RequestHandler calls this function, the client
* has no desire to interfer with the request and it should
* continue to be processed normally.
*
* @param rh request that should now be forwarded
*/
void
GNUNET_DNS_request_forward (struct GNUNET_DNS_RequestHandle *rh);
/**
* If a GNUNET_DNS_RequestHandler calls this function, the request is
* to be dropped and no response should be generated.
*
* @param rh request that should now be dropped
*/
void
GNUNET_DNS_request_drop (struct GNUNET_DNS_RequestHandle *rh);
/**
* If a GNUNET_DNS_RequestHandler calls this function, the request is
* supposed to be answered with the data provided to this call (with
* the modifications the function might have made). The reply given
* must always be a valid DNS reply and not a mutated DNS request.
*
* @param rh request that should now be answered
* @param reply_length size of @a reply (uint16_t to force sane size)
* @param reply reply data
*/
void
GNUNET_DNS_request_answer (struct GNUNET_DNS_RequestHandle *rh,
uint16_t reply_length,
const char *reply);
/**
* Connect to the service-dns
*
* @param cfg configuration to use
* @param flags when to call @a rh
* @param rh function to call with DNS requests
* @param rh_cls closure to pass to @a rh
* @return DNS handle
*/
struct GNUNET_DNS_Handle *
GNUNET_DNS_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
enum GNUNET_DNS_Flags flags,
GNUNET_DNS_RequestHandler rh,
void *rh_cls);
/**
* Disconnect from the DNS service.
*
* @param dh DNS handle
*/
void
GNUNET_DNS_disconnect (struct GNUNET_DNS_Handle *dh);
#endif
/** @} */ /* end of group */
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