133 lines
6.3 KiB
C
133 lines
6.3 KiB
C
/* Copyright 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <osmocom/core/linuxlist.h>
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#include <osmocom/core/timer.h>
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#include <osmocom/core/sockaddr_str.h>
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#include <osmocom/mslookup/mslookup.h>
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struct osmo_mslookup_client;
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struct osmo_mslookup_result;
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typedef void (*osmo_mslookup_cb_t)(struct osmo_mslookup_client *client,
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uint32_t request_handle,
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const struct osmo_mslookup_query *query,
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const struct osmo_mslookup_result *result);
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/*! This handling information is passed along with a lookup request.
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* It tells the osmo_mslookup_client layer how to handle responses received from various mslookup methods (at the time
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* of writing only mDNS exists as a method, but the intention is to easily allow adding other methods in the future).
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* This query handling info is not seen by the individual method implementations, to clarify that it is the
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* osmo_mslookup_client layer that takes care of these details. */
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struct osmo_mslookup_query_handling {
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/*! Wait at least this long before returning any results.
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*
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* If nonzero, result_cb will be called as soon as this delay has elapsed, either with the so far youngest age
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* result, or with a "not found yet" result. After this delay has elapsed, receiving results will continue
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* until result_timeout_milliseconds has elapsed.
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*
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* If zero, responses are fed to the result_cb right from the start, every time a younger aged result than
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* before comes in.
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*
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* If a result with age == 0 is received, min_wait_milliseconds is ignored, the result is returned immediately
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* and listening for responses ends.
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*
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* Rationale: If a subscriber has recently moved between sites, multiple results will arrive, and the youngest
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* age wins. It can make sense to wait a minimum time for responses before determining the winning result.
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*
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* However, if no result or no valid result has arrived within a short period, the subscriber may be at a site
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* that is far away or that is currently experiencing high latency. It is thus a good safety net to still
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* receive results for an extended period of time.
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*
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* For some services, it is possible to establish links to every received result, and whichever link succeeds
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* will be used (for example for SIP calls: first to pick up the call gets connected, the others are dropped
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* silently).
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*/
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uint32_t min_wait_milliseconds;
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/*! Total time in milliseconds to listen for lookup responses.
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*
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* When this timeout elapses, osmo_mslookup_client_request_cancel() is called implicitly; Manually invoking
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* osmo_mslookup_client_request_cancel() after result_timeout_milliseconds has elapsed is not necessary, but is
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* still safe to do anyway.
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*
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* If zero, min_wait_milliseconds is also used as result_timeout_milliseconds; if that is also zero, a default
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* timeout value is used.
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*
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* If result_timeout_milliseconds <= min_wait_milliseconds, then min_wait_milliseconds is used as
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* result_timeout_milliseconds, i.e. the timeout triggers as soon as min_wait_milliseconds hits.
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*
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* osmo_mslookup_client_request_cancel() can be called any time to end the request.
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*/
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uint32_t result_timeout_milliseconds;
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/*! Invoked every time a result with a younger age than the previous result has arrived.
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* To stop receiving results before result_timeout_milliseconds has elapsed, call
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* osmo_mslookup_client_request_cancel().
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*/
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osmo_mslookup_cb_t result_cb;
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};
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uint32_t osmo_mslookup_client_request(struct osmo_mslookup_client *client,
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const struct osmo_mslookup_query *query,
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const struct osmo_mslookup_query_handling *handling);
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void osmo_mslookup_client_request_cancel(struct osmo_mslookup_client *client, uint32_t request_handle);
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struct osmo_mslookup_client *osmo_mslookup_client_new(void *ctx);
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bool osmo_mslookup_client_active(struct osmo_mslookup_client *client);
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void osmo_mslookup_client_free(struct osmo_mslookup_client *client);
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/*! Describe a specific mslookup client method implementation. This struct is only useful for a lookup method
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* implementation to add itself to an osmo_mslookup_client, see for example osmo_mslookup_client_add_mdns(). */
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struct osmo_mslookup_client_method {
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struct llist_head entry;
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/*! Human readable name of this lookup method. */
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const char *name;
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/*! Private data for the lookup method implementation. */
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void *priv;
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/*! Backpointer to the client this method is added to. */
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struct osmo_mslookup_client *client;
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/*! Launch a lookup query. Called from osmo_mslookup_client_request().
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* The implementation returns results by calling osmo_mslookup_client_rx_result(). */
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void (*request)(struct osmo_mslookup_client_method *method,
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const struct osmo_mslookup_query *query,
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uint32_t request_handle);
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/*! End a lookup query. Called from osmo_mslookup_client_request_cancel(). It is guaranteed to be called
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* exactly once per above request() invocation. (The API user is required to invoke
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* osmo_mslookup_client_request_cancel() exactly once per osmo_mslookup_client_request().) */
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void (*request_cleanup)(struct osmo_mslookup_client_method *method,
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uint32_t request_handle);
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/*! The mslookup_client is removing this method, clean up all open requests, lists and allocations. */
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void (*destruct)(struct osmo_mslookup_client_method *method);
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};
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void osmo_mslookup_client_method_add(struct osmo_mslookup_client *client,
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struct osmo_mslookup_client_method *method);
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bool osmo_mslookup_client_method_del(struct osmo_mslookup_client *client,
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struct osmo_mslookup_client_method *method);
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void osmo_mslookup_client_rx_result(struct osmo_mslookup_client *client, uint32_t request_handle,
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const struct osmo_mslookup_result *result);
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