Oliver Smith | bf7deda | 2019-11-20 10:56:35 +0100 | [diff] [blame^] | 1 | /* Copyright 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de> |
| 2 | * |
| 3 | * All Rights Reserved |
| 4 | * |
| 5 | * This program is free software; you can redistribute it and/or modify |
| 6 | * it under the terms of the GNU General Public License as published by |
| 7 | * the Free Software Foundation; either version 2 of the License, or |
| 8 | * (at your option) any later version. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
| 14 | * |
| 15 | * You should have received a copy of the GNU General Public License along |
| 16 | * with this program. If not, see <http://www.gnu.org/licenses/>. |
| 17 | */ |
| 18 | |
| 19 | #pragma once |
| 20 | |
| 21 | #include <osmocom/core/linuxlist.h> |
| 22 | #include <osmocom/core/timer.h> |
| 23 | #include <osmocom/core/sockaddr_str.h> |
| 24 | #include <osmocom/mslookup/mslookup.h> |
| 25 | |
| 26 | struct osmo_mslookup_client; |
| 27 | struct osmo_mslookup_result; |
| 28 | |
| 29 | typedef void (*osmo_mslookup_cb_t)(struct osmo_mslookup_client *client, |
| 30 | uint32_t request_handle, |
| 31 | const struct osmo_mslookup_query *query, |
| 32 | const struct osmo_mslookup_result *result); |
| 33 | |
| 34 | /*! This handling information is passed along with a lookup request. |
| 35 | * It tells the osmo_mslookup_client layer how to handle responses received from various mslookup methods (at the time |
| 36 | * of writing only mDNS exists as a method, but the intention is to easily allow adding other methods in the future). |
| 37 | * This query handling info is not seen by the individual method implementations, to clarify that it is the |
| 38 | * osmo_mslookup_client layer that takes care of these details. */ |
| 39 | struct osmo_mslookup_query_handling { |
| 40 | /*! Wait at least this long before returning any results. |
| 41 | * |
| 42 | * If nonzero, result_cb will be called as soon as this delay has elapsed, either with the so far youngest age |
| 43 | * result, or with a "not found yet" result. After this delay has elapsed, receiving results will continue |
| 44 | * until result_timeout_milliseconds has elapsed. |
| 45 | * |
| 46 | * If zero, responses are fed to the result_cb right from the start, every time a younger aged result than |
| 47 | * before comes in. |
| 48 | * |
| 49 | * If a result with age == 0 is received, min_wait_milliseconds is ignored, the result is returned immediately |
| 50 | * and listening for responses ends. |
| 51 | * |
| 52 | * Rationale: If a subscriber has recently moved between sites, multiple results will arrive, and the youngest |
| 53 | * age wins. It can make sense to wait a minimum time for responses before determining the winning result. |
| 54 | * |
| 55 | * However, if no result or no valid result has arrived within a short period, the subscriber may be at a site |
| 56 | * that is far away or that is currently experiencing high latency. It is thus a good safety net to still |
| 57 | * receive results for an extended period of time. |
| 58 | * |
| 59 | * For some services, it is possible to establish links to every received result, and whichever link succeeds |
| 60 | * will be used (for example for SIP calls: first to pick up the call gets connected, the others are dropped |
| 61 | * silently). |
| 62 | */ |
| 63 | uint32_t min_wait_milliseconds; |
| 64 | |
| 65 | /*! Total time in milliseconds to listen for lookup responses. |
| 66 | * |
| 67 | * When this timeout elapses, osmo_mslookup_client_request_cancel() is called implicitly; Manually invoking |
| 68 | * osmo_mslookup_client_request_cancel() after result_timeout_milliseconds has elapsed is not necessary, but is |
| 69 | * still safe to do anyway. |
| 70 | * |
| 71 | * If zero, min_wait_milliseconds is also used as result_timeout_milliseconds; if that is also zero, a default |
| 72 | * timeout value is used. |
| 73 | * |
| 74 | * If result_timeout_milliseconds <= min_wait_milliseconds, then min_wait_milliseconds is used as |
| 75 | * result_timeout_milliseconds, i.e. the timeout triggers as soon as min_wait_milliseconds hits. |
| 76 | * |
| 77 | * osmo_mslookup_client_request_cancel() can be called any time to end the request. |
| 78 | */ |
| 79 | uint32_t result_timeout_milliseconds; |
| 80 | |
| 81 | /*! Invoked every time a result with a younger age than the previous result has arrived. |
| 82 | * To stop receiving results before result_timeout_milliseconds has elapsed, call |
| 83 | * osmo_mslookup_client_request_cancel(). |
| 84 | */ |
| 85 | osmo_mslookup_cb_t result_cb; |
| 86 | }; |
| 87 | |
| 88 | uint32_t osmo_mslookup_client_request(struct osmo_mslookup_client *client, |
| 89 | const struct osmo_mslookup_query *query, |
| 90 | const struct osmo_mslookup_query_handling *handling); |
| 91 | |
| 92 | void osmo_mslookup_client_request_cancel(struct osmo_mslookup_client *client, uint32_t request_handle); |
| 93 | |
| 94 | struct osmo_mslookup_client *osmo_mslookup_client_new(void *ctx); |
| 95 | bool osmo_mslookup_client_active(struct osmo_mslookup_client *client); |
| 96 | void osmo_mslookup_client_free(struct osmo_mslookup_client *client); |
| 97 | |
| 98 | /*! Describe a specific mslookup client method implementation. This struct is only useful for a lookup method |
| 99 | * implementation to add itself to an osmo_mslookup_client, see for example osmo_mslookup_client_add_mdns(). */ |
| 100 | struct osmo_mslookup_client_method { |
| 101 | struct llist_head entry; |
| 102 | |
| 103 | /*! Human readable name of this lookup method. */ |
| 104 | const char *name; |
| 105 | |
| 106 | /*! Private data for the lookup method implementation. */ |
| 107 | void *priv; |
| 108 | |
| 109 | /*! Backpointer to the client this method is added to. */ |
| 110 | struct osmo_mslookup_client *client; |
| 111 | |
| 112 | /*! Launch a lookup query. Called from osmo_mslookup_client_request(). |
| 113 | * The implementation returns results by calling osmo_mslookup_client_rx_result(). */ |
| 114 | void (*request)(struct osmo_mslookup_client_method *method, |
| 115 | const struct osmo_mslookup_query *query, |
| 116 | uint32_t request_handle); |
| 117 | /*! End a lookup query. Called from osmo_mslookup_client_request_cancel(). It is guaranteed to be called |
| 118 | * exactly once per above request() invocation. (The API user is required to invoke |
| 119 | * osmo_mslookup_client_request_cancel() exactly once per osmo_mslookup_client_request().) */ |
| 120 | void (*request_cleanup)(struct osmo_mslookup_client_method *method, |
| 121 | uint32_t request_handle); |
| 122 | |
| 123 | /*! The mslookup_client is removing this method, clean up all open requests, lists and allocations. */ |
| 124 | void (*destruct)(struct osmo_mslookup_client_method *method); |
| 125 | }; |
| 126 | |
| 127 | void osmo_mslookup_client_method_add(struct osmo_mslookup_client *client, |
| 128 | struct osmo_mslookup_client_method *method); |
| 129 | bool osmo_mslookup_client_method_del(struct osmo_mslookup_client *client, |
| 130 | struct osmo_mslookup_client_method *method); |
| 131 | void osmo_mslookup_client_rx_result(struct osmo_mslookup_client *client, uint32_t request_handle, |
| 132 | const struct osmo_mslookup_result *result); |