lws-async-dns.h

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/*
 * libwebsockets - small server side websockets and web server implementation
 *
 * Copyright (C) 2010 - 2019 Andy Green <andy@warmcat.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */
 
#if defined(LWS_WITH_UDP) && defined(LWS_WITH_NETWORK)
 
typedef enum dns_query_type {
        LWS_ADNS_RECORD_A                                       = 0x01,
        LWS_ADNS_RECORD_CNAME                                   = 0x05,
        LWS_ADNS_RECORD_MX                                      = 0x0f,
        LWS_ADNS_RECORD_AAAA                                    = 0x1c,
} adns_query_type_t;
 
typedef enum {
        LADNS_RET_FAILED_WSI_CLOSED                             = -4,
        LADNS_RET_NXDOMAIN                                      = -3,
        LADNS_RET_TIMEDOUT                                      = -2,
        LADNS_RET_FAILED                                        = -1,
        LADNS_RET_FOUND,
        LADNS_RET_CONTINUING
} lws_async_dns_retcode_t;
 
#define LWS_ADNS_SYNTHETIC      0x10000 /* don't send, synthetic response will
                                         * be injected for testing */
 
struct addrinfo;
 
typedef struct lws * (*lws_async_dns_cb_t)(struct lws *wsi, const char *ads,
                const struct addrinfo *result, int n, void *opaque);
 
struct lws_adns_q;
struct lws_async_dns;
 
/**
 * lws_async_dns_query() - perform a dns lookup using async dns
 *
 * \param context: the lws_context
 * \param tsi: thread service index (usually 0)
 * \param name: DNS name to look up
 * \param qtype: type of query (A, AAAA etc)
 * \param cb: query completion callback
 * \param wsi: wsi if the query is related to one
 * \param pq: NULL, or pointer to lws_adns_q query (used for testing)
 *
 * Starts an asynchronous DNS lookup, on completion the \p cb callback will
 * be called.
 *
 * The reference count on the cached object is incremented for every callback
 * that was called with the cached addrinfo results.
 *
 * The cached object can't be evicted until the reference count reaches zero...
 * use lws_async_dns_freeaddrinfo() to indicate you're finsihed with the
 * results for each callback that happened with them.
 */
LWS_VISIBLE LWS_EXTERN lws_async_dns_retcode_t
lws_async_dns_query(struct lws_context *context, int tsi, const char *name,
                    adns_query_type_t qtype, lws_async_dns_cb_t cb,
                    struct lws *wsi, void *opaque, struct lws_adns_q **pq);
 
/**
 * lws_async_dns_freeaddrinfo() - decrement refcount on cached addrinfo results
 *
 * \param pai: a pointert to a pointer to first addrinfo returned as result in the callback
 *
 * Decrements the cache object's reference count.  When it reaches zero, the
 * cached object may be reaped subject to LRU rules.
 *
 * The pointer to the first addrinfo give in the argument is set to NULL.
 */
LWS_VISIBLE LWS_EXTERN void
lws_async_dns_freeaddrinfo(const struct addrinfo **ai);
 
/**
 * lws_async_dns_server_add() - add a DNS server to the lws async DNS list
 *
 * \param cx: the lws_context
 * \param sa46: the ipv4 or ipv6 DNS server address to add
 *
 * Adds the given DNS server to the lws list of async DNS servers to query.
 * If the address is already listed, its refcount is increased, otherwise a new
 * entry is made.
 */
LWS_VISIBLE LWS_EXTERN int
lws_async_dns_server_add(struct lws_context *cx, const lws_sockaddr46 *sa46);
 
/**
 * lws_async_dns_server_remove() - remove a DNS server from the lws async DNS list
 *
 * \param cx: the lws_context
 * \param sa46: the ipv4 or ipv6 DNS server address to add
 *
 * Removes the given DNS server from the lws list of async DNS servers to query.
 * If the address does not correspond to an existing entry, no action is taken.
 * If it does, the refcount on it is decremented, and if it reaches zero, the
 * entry is detached from the list and destroyed.
 */
LWS_VISIBLE LWS_EXTERN void
lws_async_dns_server_remove(struct lws_context *cx, const lws_sockaddr46 *sa46);
 
/* only needed for testing */
 
LWS_VISIBLE LWS_EXTERN uint16_t
lws_adns_get_tid(struct lws_adns_q *q);
LWS_VISIBLE LWS_EXTERN struct lws_async_dns *
lws_adns_get_async_dns(struct lws_adns_q *q);
 
LWS_VISIBLE LWS_EXTERN void
lws_adns_parse_udp(struct lws_async_dns *dns, const uint8_t *pkt, size_t len);
 
#endif