2 This file is part of GNUnet
3 (C) 2012 Christian Grothoff (and other contributing authors)
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22 * @file include/gnunet_dns_service.h
23 * @brief API to access the DNS service.
24 * @author Christian Grothoff
26 #ifndef GNUNET_DNS_SERVICE_H
27 #define GNUNET_DNS_SERVICE_H
29 #include "gnunet_util_lib.h"
35 struct GNUNET_DNS_Handle;
38 * Handle to identify an individual DNS request.
40 struct GNUNET_DNS_RequestHandle;
43 * Flags that specify when to call the client's handler.
49 * Useless option: never call the client.
51 GNUNET_DNS_FLAG_NEVER = 0,
54 * Set this flag to see all requests first prior to resolution
55 * (for monitoring). Clients that set this flag must then
56 * call "GNUNET_DNS_request_forward" when they process a request
57 * for the first time. Caling "GNUNET_DNS_request_answer" is
58 * not allowed for MONITOR peers.
60 GNUNET_DNS_FLAG_REQUEST_MONITOR = 1,
63 * This client should be called on requests that have not
64 * yet been resolved as this client provides a resolution
65 * service. Note that this does not guarantee that the
66 * client will see all requests as another client might be
67 * called first and that client might have already done the
68 * resolution, in which case other pre-resolution clients
69 * won't see the request anymore.
71 GNUNET_DNS_FLAG_PRE_RESOLUTION = 2,
74 * This client wants to be called on the results of a DNS resolution
75 * (either resolved by PRE-RESOLUTION clients or the global DNS).
76 * The client then has a chance to modify the answer (or cause it to
77 * be dropped). There is no guarantee that other POST-RESOLUTION
78 * client's won't modify (or drop) the answer afterwards.
80 GNUNET_DNS_FLAG_POST_RESOLUTION = 4,
83 * Set this flag to see all requests just before they are
84 * returned to the network. Clients that set this flag must then
85 * call "GNUNET_DNS_request_forward" when they process a request
86 * for the last time. Caling "GNUNET_DNS_request_answer" is
87 * not allowed for MONITOR peers.
89 GNUNET_DNS_FLAG_RESPONSE_MONITOR = 8
96 * Signature of a function that is called whenever the DNS service
97 * encounters a DNS request and needs to do something with it. The
98 * function has then the chance to generate or modify the response by
99 * calling one of the three "GNUNET_DNS_request_*" continuations.
101 * When a request is intercepted, this function is called first to
102 * give the client a chance to do the complete address resolution;
103 * "rdata" will be NULL for this first call for a DNS request, unless
104 * some other client has already filled in a response.
106 * If multiple clients exist, all of them are called before the global
107 * DNS. The global DNS is only called if all of the clients'
108 * functions call GNUNET_DNS_request_forward. Functions that call
109 * GNUNET_DNS_request_forward will be called again before a final
110 * response is returned to the application. If any of the clients'
111 * functions call GNUNET_DNS_request_drop, the response is dropped.
114 * @param rh request handle to user for reply
115 * @param request_length number of bytes in request
116 * @param request udp payload of the DNS request
118 typedef void (*GNUNET_DNS_RequestHandler)(void *cls,
119 struct GNUNET_DNS_RequestHandle *rh,
120 size_t request_length,
121 const char *request);
125 * If a GNUNET_DNS_RequestHandler calls this function, the client
126 * has no desire to interfer with the request and it should
127 * continue to be processed normally.
129 * @param rh request that should now be forwarded
132 GNUNET_DNS_request_forward (struct GNUNET_DNS_RequestHandle *rh);
136 * If a GNUNET_DNS_RequestHandler calls this function, the request is
137 * to be dropped and no response should be generated.
139 * @param rh request that should now be dropped
142 GNUNET_DNS_request_drop (struct GNUNET_DNS_RequestHandle *rh);
146 * If a GNUNET_DNS_RequestHandler calls this function, the request is
147 * supposed to be answered with the data provided to this call (with
148 * the modifications the function might have made). The reply given
149 * must always be a valid DNS reply and not a mutated DNS request.
151 * @param rh request that should now be answered
152 * @param reply_length size of reply (uint16_t to force sane size)
153 * @param reply reply data
156 GNUNET_DNS_request_answer (struct GNUNET_DNS_RequestHandle *rh,
157 uint16_t reply_length,
162 * Connect to the service-dns
164 * @param cfg configuration to use
165 * @param flags when to call rh
166 * @param rh function to call with DNS requests
167 * @param rh_cls closure to pass to rh
170 struct GNUNET_DNS_Handle *
171 GNUNET_DNS_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
172 enum GNUNET_DNS_Flags flags,
173 GNUNET_DNS_RequestHandler rh,
178 * Disconnect from the DNS service.
180 * @param dh DNS handle
183 GNUNET_DNS_disconnect (struct GNUNET_DNS_Handle *dh);