layer.h 3.57 KB
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/*  Copyright (C) 2014-2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
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    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
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    This program 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 General Public License for more details.
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    You should have received a copy of the GNU General Public License
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    along with this program.  If not, see <https://www.gnu.org/licenses/>.
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 */
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#pragma once

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#include "lib/defines.h"
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#include "lib/utils.h"
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#ifdef NOVERBOSELOG
	#define QRVERBOSE(query, cls, ...)
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#else
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	/** Print a debug message related to resolution.
	 * \param _query	associated kr_query, may be NULL
	 * \param _cls	identifying string, typically of length exactly four (padded)
	 * \param ...	printf-compatible list of parameters
	 */
	#define QRVERBOSE(_query, _cls, ...) do { \
		const struct kr_query *_qry = (_query); \
		if (kr_log_trace_enabled(_qry)) { \
			kr_log_trace(_qry, (_cls), __VA_ARGS__); \
		} else if (VERBOSE_STATUS) { \
			kr_log_qverbose_impl(_qry, (_cls), __VA_ARGS__); \
		}  \
	} while (false)
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#endif

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/** Layer processing states.  Only one value at a time (but see TODO).
 *
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 *  Each state represents the state machine transition,
 *  and determines readiness for the next action.
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 *  See struct kr_layer_api for the actions.
 *
 *  TODO: the cookie module sometimes sets (_FAIL | _DONE) on purpose (!)
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 */
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enum kr_layer_state {
	KR_STATE_CONSUME = 1 << 0, /*!< Consume data. */
	KR_STATE_PRODUCE = 1 << 1, /*!< Produce data. */
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	KR_STATE_DONE    = 1 << 2, /*!< Finished successfully. */
	KR_STATE_FAIL    = 1 << 3, /*!< Error. */
	KR_STATE_YIELD   = 1 << 4, /*!< Paused, waiting for a sub-query. */
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};

/* Forward declarations. */
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struct kr_layer_api;
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/** Packet processing context. */
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typedef struct kr_layer {
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	int state; /*!< The current state; bitmap of enum kr_layer_state. */
	struct kr_request *req; /*!< The corresponding request. */
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	const struct kr_layer_api *api;
} kr_layer_t;
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/** Packet processing module API.  All functions return the new kr_layer_state. */
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struct kr_layer_api {
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      	/** Start of processing the DNS request. */
	int (*begin)(kr_layer_t *ctx);

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	int (*reset)(kr_layer_t *ctx);
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	/** Paired to begin, called both on successes and failures. */
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	int (*finish)(kr_layer_t *ctx);
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	/** Processing an answer from upstream or the answer to the request. */
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	int (*consume)(kr_layer_t *ctx, knot_pkt_t *pkt);
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	/** Produce either an answer to the request or a query for upstream (or fail). */
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	int (*produce)(kr_layer_t *ctx, knot_pkt_t *pkt);
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	/** Finalises the outbound query packet with the knowledge of the IP addresses.
	 * The checkout layer doesn't persist the state, so canceled subrequests
	 * don't affect the resolution or rest of the processing. */
	int (*checkout)(kr_layer_t *ctx, knot_pkt_t *packet, struct sockaddr *dst, int type);

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	/** Finalises the answer.
	 * Last chance to affect what will get into the answer, including EDNS.*/
	int (*answer_finalize)(kr_layer_t *ctx);

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	/** The module can store anything in here. */
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	void *data;
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	/** Internal to ./daemon/ffimodule.c. */
	int cb_slots[];
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};

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typedef struct kr_layer_api kr_layer_api_t;
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/** Pickled layer state (api, input, state). */
struct kr_layer_pickle {
    struct kr_layer_pickle *next;
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    const struct kr_layer_api *api;
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    knot_pkt_t *pkt;
    unsigned state;
};