dns-resolver.h
/*
* QEMU DNS resolver
*
* Copyright (c) 2016-2017 Red Hat, Inc.
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library; if not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef QIO_DNS_RESOLVER_H
#define QIO_DNS_RESOLVER_H
#include "qapi/qapi-types-sockets.h"
#include "qom/object.h"
#include "io/task.h"
#define TYPE_QIO_DNS_RESOLVER "qio-dns-resolver"
#define QIO_DNS_RESOLVER(obj) \
OBJECT_CHECK(QIODNSResolver, (obj), TYPE_QIO_DNS_RESOLVER)
#define QIO_DNS_RESOLVER_CLASS(klass) \
OBJECT_CLASS_CHECK(QIODNSResolverClass, klass, TYPE_QIO_DNS_RESOLVER)
#define QIO_DNS_RESOLVER_GET_CLASS(obj) \
OBJECT_GET_CLASS(QIODNSResolverClass, obj, TYPE_QIO_DNS_RESOLVER)
typedef struct QIODNSResolver QIODNSResolver;
typedef struct QIODNSResolverClass QIODNSResolverClass;
/**
* QIODNSResolver:
*
* The QIODNSResolver class provides a framework for doing
* DNS resolution on SocketAddress objects, independently
* of socket creation.
*
* <example>
* <title>Resolving addresses synchronously</title>
* <programlisting>
* int mylisten(SocketAddress *addr, Error **errp) {
* QIODNSResolver *resolver = qio_dns_resolver_get_instance();
* SocketAddress **rawaddrs = NULL;
* size_t nrawaddrs = 0;
* Error *err = NULL;
* QIOChannel **socks = NULL;
* size_t nsocks = 0;
*
* if (qio_dns_resolver_lookup_sync(dns, addr, &nrawaddrs,
* &rawaddrs, errp) < 0) {
* return -1;
* }
*
* for (i = 0; i < nrawaddrs; i++) {
* QIOChannel *sock = qio_channel_new();
* Error *local_err = NULL;
* qio_channel_listen_sync(sock, rawaddrs[i], &local_err);
* if (local_err) {
* error_propagate(&err, local_err);
* } else {
* socks = g_renew(QIOChannelSocket *, socks, nsocks + 1);
* socks[nsocks++] = sock;
* }
* qapi_free_SocketAddress(rawaddrs[i]);
* }
* g_free(rawaddrs);
*
* if (nsocks == 0) {
* error_propagate(errp, err);
* } else {
* error_free(err);
* }
* }
* </programlisting>
* </example>
*
* <example>
* <title>Resolving addresses asynchronously</title>
* <programlisting>
* typedef struct MyListenData {
* Error *err;
* QIOChannelSocket **socks;
* size_t nsocks;
* } MyListenData;
*
* void mylistenresult(QIOTask *task, void *opaque) {
* MyListenData *data = opaque;
* QIODNSResolver *resolver =
* QIO_DNS_RESOLVER(qio_task_get_source(task);
* SocketAddress **rawaddrs = NULL;
* size_t nrawaddrs = 0;
* Error *err = NULL;
*
* if (qio_task_propagate_error(task, &data->err)) {
* return;
* }
*
* qio_dns_resolver_lookup_result(resolver, task,
* &nrawaddrs, &rawaddrs);
*
* for (i = 0; i < nrawaddrs; i++) {
* QIOChannel *sock = qio_channel_new();
* Error *local_err = NULL;
* qio_channel_listen_sync(sock, rawaddrs[i], &local_err);
* if (local_err) {
* error_propagate(&err, local_err);
* } else {
* socks = g_renew(QIOChannelSocket *, socks, nsocks + 1);
* socks[nsocks++] = sock;
* }
* qapi_free_SocketAddress(rawaddrs[i]);
* }
* g_free(rawaddrs);
*
* if (nsocks == 0) {
* error_propagate(&data->err, err);
* } else {
* error_free(err);
* }
* }
*
* void mylisten(SocketAddress *addr, MyListenData *data) {
* QIODNSResolver *resolver = qio_dns_resolver_get_instance();
* qio_dns_resolver_lookup_async(dns, addr,
* mylistenresult, data, NULL);
* }
* </programlisting>
* </example>
*/
struct QIODNSResolver {
Object parent;
};
struct QIODNSResolverClass {
ObjectClass parent;
};
/**
* qio_dns_resolver_get_instance:
*
* Get the singleton dns resolver instance. The caller
* does not own a reference on the returned object.
*
* Returns: the single dns resolver instance
*/
QIODNSResolver *qio_dns_resolver_get_instance(void);
/**
* qio_dns_resolver_lookup_sync:
* @resolver: the DNS resolver instance
* @addr: the address to resolve
* @naddr: pointer to hold number of resolved addresses
* @addrs: pointer to hold resolved addresses
* @errp: pointer to NULL initialized error object
*
* This will attempt to resolve the address provided
* in @addr. If resolution succeeds, @addrs will be filled
* with all the resolved addresses. @naddrs will specify
* the number of entries allocated in @addrs. The caller
* is responsible for freeing each entry in @addrs, as
* well as @addrs itself. @naddrs is guaranteed to be
* greater than zero on success.
*
* DNS resolution will be done synchronously so execution
* of the caller may be blocked for an arbitrary length
* of time.
*
* Returns: 0 if resolution was successful, -1 on error
*/
int qio_dns_resolver_lookup_sync(QIODNSResolver *resolver,
SocketAddress *addr,
size_t *naddrs,
SocketAddress ***addrs,
Error **errp);
/**
* qio_dns_resolver_lookup_async:
* @resolver: the DNS resolver instance
* @addr: the address to resolve
* @func: the callback to invoke on lookup completion
* @opaque: data blob to pass to @func
* @notify: the callback to free @opaque, or NULL
*
* This will attempt to resolve the address provided
* in @addr. The callback @func will be invoked when
* resolution has either completed or failed. On
* success, the @func should call the method
* qio_dns_resolver_lookup_result() to obtain the
* results.
*
* DNS resolution will be done asynchronously so execution
* of the caller will not be blocked.
*/
void qio_dns_resolver_lookup_async(QIODNSResolver *resolver,
SocketAddress *addr,
QIOTaskFunc func,
gpointer opaque,
GDestroyNotify notify);
/**
* qio_dns_resolver_lookup_result:
* @resolver: the DNS resolver instance
* @task: the task object to get results for
* @naddr: pointer to hold number of resolved addresses
* @addrs: pointer to hold resolved addresses
*
* This method should be called from the callback passed
* to qio_dns_resolver_lookup_async() in order to obtain
* results. @addrs will be filled with all the resolved
* addresses. @naddrs will specify the number of entries
* allocated in @addrs. The caller is responsible for
* freeing each entry in @addrs, as well as @addrs itself.
*/
void qio_dns_resolver_lookup_result(QIODNSResolver *resolver,
QIOTask *task,
size_t *naddrs,
SocketAddress ***addrs);
#endif /* QIO_DNS_RESOLVER_H */
