Add GResolver, a glib-ish interface to DNS

GResolver provides asynchronous (and synchronous-but-cancellable) APIs
for resolving hostnames, reverse-resolving IP addresses back to
hostnames, and resolving SRV records. Part of #548466.

gio/libasyncns/asyncns.h

@@ -0,0 +1,163 @@
+#ifndef fooasyncnshfoo
+#define fooasyncnshfoo
+
+/***
+  This file is part of libasyncns.
+
+  Copyright 2005-2008 Lennart Poettering
+
+  libasyncns is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as
+  published by the Free Software Foundation, either version 2.1 of the
+  License, or (at your option) any later version.
+
+  libasyncns 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with libasyncns. If not, see
+  <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+
+/** \mainpage
+ *
+ * \section moo Method of operation
+ *
+ * To use libasyncns allocate an _g_asyncns_t object with
+ * _g_asyncns_new(). This will spawn a number of worker threads (or processes, depending on what is available) which
+ * are subsequently used to process the queries the controlling
+ * program issues via _g_asyncns_getaddrinfo() and
+ * _g_asyncns_getnameinfo(). Use _g_asyncns_free() to shut down the worker
+ * threads/processes.
+ *
+ * Since libasyncns may fork off new processes you have to make sure that
+ * your program is not irritated by spurious SIGCHLD signals.
+ */
+
+/** \example asyncns-test.c
+ * An example program */
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+
+/** An opaque libasyncns session structure */
+typedef struct asyncns _g_asyncns_t;
+
+/** An opaque libasyncns query structure */
+typedef struct _g_asyncns_query _g_asyncns_query_t;
+
+/** Allocate a new libasyncns session with n_proc worker processes/threads */
+_g_asyncns_t* _g_asyncns_new(unsigned n_proc);
+
+/** Free a libasyncns session. This destroys all attached
+ * _g_asyncns_query_t objects automatically */
+void _g_asyncns_free(_g_asyncns_t *asyncns);
+
+/** Return the UNIX file descriptor to select() for readability
+ * on. Use this function to integrate libasyncns with your custom main
+ * loop. */
+int _g_asyncns_fd(_g_asyncns_t *asyncns);
+
+/** Process pending responses. After this function is called you can
+ * get the next completed query object(s) using _g_asyncns_getnext(). If
+ * block is non-zero wait until at least one response has been
+ * processed. If block is zero, process all pending responses and
+ * return. */
+int _g_asyncns_wait(_g_asyncns_t *asyncns, int block);
+
+/** Issue a name to address query on the specified session. The
+ * arguments are compatible with the ones of libc's
+ * getaddrinfo(3). The function returns a new query object. When the
+ * query is completed you may retrieve the results using
+ * _g_asyncns_getaddrinfo_done().*/
+_g_asyncns_query_t* _g_asyncns_getaddrinfo(_g_asyncns_t *asyncns, const char *node, const char *service, const struct addrinfo *hints);
+
+/** Retrieve the results of a preceding _g_asyncns_getaddrinfo()
+ * call. Returns a addrinfo structure and a return value compatible
+ * with libc's getaddrinfo(3). The query object q is destroyed by this
+ * call and may not be used any further. Make sure to free the
+ * returned addrinfo structure with _g_asyncns_freeaddrinfo() and not
+ * libc's freeaddrinfo(3)! If the query is not completed yet EAI_AGAIN
+ * is returned.*/
+int _g_asyncns_getaddrinfo_done(_g_asyncns_t *asyncns, _g_asyncns_query_t* q, struct addrinfo **ret_res);
+
+/** Issue an address to name query on the specified session. The
+ * arguments are compatible with the ones of libc's
+ * getnameinfo(3). The function returns a new query object. When the
+ * query is completed you may retrieve the results using
+ * _g_asyncns_getnameinfo_done(). Set gethost (resp. getserv) to non-zero
+ * if you want to query the hostname (resp. the service name). */
+_g_asyncns_query_t* _g_asyncns_getnameinfo(_g_asyncns_t *asyncns, const struct sockaddr *sa, socklen_t salen, int flags, int gethost, int getserv);
+
+/** Retrieve the results of a preceding _g_asyncns_getnameinfo()
+ * call. Returns the hostname and the service name in ret_host and
+ * ret_serv. The query object q is destroyed by this call and may not
+ * be used any further. If the query is not completed yet EAI_AGAIN is
+ * returned. */
+int _g_asyncns_getnameinfo_done(_g_asyncns_t *asyncns, _g_asyncns_query_t* q, char *ret_host, size_t hostlen, char *ret_serv, size_t servlen);
+
+/** Issue a resolver query on the specified session. The arguments are
+ * compatible with the ones of libc's res_query(3). The function returns a new
+ * query object. When the query is completed you may retrieve the results using
+ * _g_asyncns_res_done().  */
+_g_asyncns_query_t* _g_asyncns_res_query(_g_asyncns_t *asyncns, const char *dname, int class, int type);
+
+/** Issue an resolver query on the specified session. The arguments are
+ * compatible with the ones of libc's res_search(3). The function returns a new
+ * query object. When the query is completed you may retrieve the results using
+ * _g_asyncns_res_done().  */
+_g_asyncns_query_t* _g_asyncns_res_search(_g_asyncns_t *asyncns, const char *dname, int class, int type);
+
+/** Retrieve the results of a preceding _g_asyncns_res_query() or
+ * _g_asyncns_res_search call.  The query object q is destroyed by this
+ * call and may not be used any further. Returns a pointer to the
+ * answer of the res_query call. If the query is not completed yet
+ * -EAGAIN is returned, on failure -errno is returned, otherwise the
+ * length of answer is returned. Make sure to free the answer is a
+ * call to _g_asyncns_freeanswer(). */
+int _g_asyncns_res_done(_g_asyncns_t *asyncns, _g_asyncns_query_t* q, unsigned char **answer);
+
+/** Return the next completed query object. If no query has been
+ * completed yet, return NULL. Please note that you need to run
+ * _g_asyncns_wait() before this function will return sensible data.  */
+_g_asyncns_query_t* _g_asyncns_getnext(_g_asyncns_t *asyncns);
+
+/** Return the number of query objects (completed or not) attached to
+ * this session */
+int _g_asyncns_getnqueries(_g_asyncns_t *asyncns);
+
+/** Cancel a currently running query. q is is destroyed by this call
+ * and may not be used any futher. */
+void _g_asyncns_cancel(_g_asyncns_t *asyncns, _g_asyncns_query_t* q);
+
+/** Free the addrinfo structure as returned by
+ * _g_asyncns_getaddrinfo_done(). Make sure to use this functions instead
+ * of the libc's freeaddrinfo()! */
+void _g_asyncns_freeaddrinfo(struct addrinfo *ai);
+
+/** Free the answer data as returned by _g_asyncns_res_done().*/
+void _g_asyncns_freeanswer(unsigned char *answer);
+
+/** Returns non-zero when the query operation specified by q has been completed */
+int _g_asyncns_isdone(_g_asyncns_t *asyncns, _g_asyncns_query_t*q);
+
+/** Assign some opaque userdata with a query object */
+void _g_asyncns_setuserdata(_g_asyncns_t *asyncns, _g_asyncns_query_t *q, void *userdata);
+
+/** Return userdata assigned to a query object. Use
+ * _g_asyncns_setuserdata() to set this data. If no data has been set
+ * prior to this call it returns NULL. */
+void* _g_asyncns_getuserdata(_g_asyncns_t *asyncns, _g_asyncns_query_t *q);
+
+#ifdef  __cplusplus
+}
+#endif
+
+#endif