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evdns: add DNS_OPTION_NAMESERVERS_NO_DEFAULT/EVDNS_BASE_NAMESERVERS_NO_DEFAULT

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- DNS_OPTION_NAMESERVERS_NO_DEFAULT
  Do not "default" nameserver (i.e. "127.0.0.1:53") if there is no nameservers
  in resolv.conf, (iff DNS_OPTION_NAMESERVERS is set)

- EVDNS_BASE_NAMESERVERS_NO_DEFAULT
  If EVDNS_BASE_INITIALIZE_NAMESERVERS isset, do not add default
  nameserver if there are no nameservers in resolv.conf (just set
  DNS_OPTION_NAMESERVERS_NO_DEFAULT internally)

Fixes: #569
(cherry picked from commit e5b8f4c1925867d8e4cd7dc0390e5141d7ef1106)
This commit is contained in:
Azat Khuzhin 2019-04-01 01:47:00 +03:00
parent aa5a65d194
commit 58e81106ad
No known key found for this signature in database
GPG Key ID: B86086848EF8686D
3 changed files with 96 additions and 8 deletions
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31
evdns.c
View File

@ -3327,10 +3327,16 @@ search_request_finished(struct evdns_request *const handle) {
static void
evdns_resolv_set_defaults(struct evdns_base *base, int flags) {
int add_default = flags & DNS_OPTION_NAMESERVERS;
if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
add_default = 0;
/* if the file isn't found then we assume a local resolver */
ASSERT_LOCKED(base);
if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(base);
if (flags & DNS_OPTION_NAMESERVERS) evdns_base_nameserver_ip_add(base,"127.0.0.1");
if (flags & DNS_OPTION_SEARCH)
search_set_from_hostname(base);
if (add_default)
evdns_base_nameserver_ip_add(base, "127.0.0.1");
}
#ifndef EVENT__HAVE_STRTOK_R
@ -3626,9 +3632,14 @@ evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char
char *resolv;
char *start;
int err = 0;
int add_default;
log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);
add_default = flags & DNS_OPTION_NAMESERVERS;
if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
add_default = 0;
if (flags & DNS_OPTION_HOSTSFILE) {
char *fname = evdns_get_default_hosts_filename();
evdns_base_load_hosts(base, fname);
@ -3664,7 +3675,7 @@ evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char
}
}
if (!base->server_head && (flags & DNS_OPTION_NAMESERVERS)) {
if (!base->server_head && add_default) {
/* no nameservers were configured. */
evdns_base_nameserver_ip_add(base, "127.0.0.1");
err = 6;
@ -3965,7 +3976,12 @@ evdns_base_new(struct event_base *event_base, int flags)
TAILQ_INIT(&base->hostsdb);
#define EVDNS_BASE_ALL_FLAGS (0x8001)
#define EVDNS_BASE_ALL_FLAGS ( \
EVDNS_BASE_INITIALIZE_NAMESERVERS | \
EVDNS_BASE_DISABLE_WHEN_INACTIVE | \
EVDNS_BASE_NAMESERVERS_NO_DEFAULT | \
0)
if (flags & ~EVDNS_BASE_ALL_FLAGS) {
flags = EVDNS_BASE_INITIALIZE_NAMESERVERS;
log(EVDNS_LOG_WARN,
@ -3976,10 +3992,15 @@ evdns_base_new(struct event_base *event_base, int flags)
if (flags & EVDNS_BASE_INITIALIZE_NAMESERVERS) {
int r;
int opts = DNS_OPTIONS_ALL;
if (flags & EVDNS_BASE_NAMESERVERS_NO_DEFAULT) {
opts |= DNS_OPTION_NAMESERVERS_NO_DEFAULT;
}
#ifdef _WIN32
r = evdns_base_config_windows_nameservers(base);
#else
r = evdns_base_resolv_conf_parse(base, DNS_OPTIONS_ALL, "/etc/resolv.conf");
r = evdns_base_resolv_conf_parse(base, opts, "/etc/resolv.conf");
#endif
if (r == -1) {
evdns_base_free_and_unlock(base, 0);

11
include/event2/dns.h
View File

@ -209,6 +209,9 @@ extern "C" {
DNS_OPTION_HOSTSFILE | \
0 \
)
/* Do not "default" nameserver (i.e. "127.0.0.1:53") if there is no nameservers
* in resolv.conf, (iff DNS_OPTION_NAMESERVERS is set) */
#define DNS_OPTION_NAMESERVERS_NO_DEFAULT 16
/* Obsolete name for DNS_QUERY_NO_SEARCH */
#define DNS_NO_SEARCH DNS_QUERY_NO_SEARCH
@ -233,6 +236,10 @@ struct event_base;
/** Flag for evdns_base_new: Do not prevent the libevent event loop from
* exiting when we have no active dns requests. */
#define EVDNS_BASE_DISABLE_WHEN_INACTIVE 0x8000
/** Flag for evdns_base_new: If EVDNS_BASE_INITIALIZE_NAMESERVERS isset, do not
* add default nameserver if there are no nameservers in resolv.conf
* @see DNS_OPTION_NAMESERVERS_NO_DEFAULT */
#define EVDNS_BASE_NAMESERVERS_NO_DEFAULT 0x10000
/**
Initialize the asynchronous DNS library.
@ -243,7 +250,7 @@ struct event_base;
@param event_base the event base to associate the dns client with
@param flags any of EVDNS_BASE_INITIALIZE_NAMESERVERS|
EVDNS_BASE_DISABLE_WHEN_INACTIVE
EVDNS_BASE_DISABLE_WHEN_INACTIVE|EVDNS_BASE_NAMESERVERS_NO_DEFAULT
@return evdns_base object if successful, or NULL if an error occurred.
@see evdns_base_free()
*/
@ -478,7 +485,7 @@ int evdns_base_set_option(struct evdns_base *base, const char *option, const cha
@param base the evdns_base to which to apply this operation
@param flags any of DNS_OPTION_NAMESERVERS|DNS_OPTION_SEARCH|DNS_OPTION_MISC|
DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL
DNS_OPTION_HOSTSFILE|DNS_OPTIONS_ALL|DNS_OPTION_NAMESERVERS_NO_DEFAULT
@param filename the path to the resolv.conf file
@return 0 if successful, or various positive error codes if an error
occurred (see above)

62
test/regress_dns.c
View File

@ -204,7 +204,7 @@ dns_resolve_reverse(void *ptr)
{
struct in_addr in;
struct event_base *base = event_base_new();
struct evdns_base *dns = evdns_base_new(base, 1/* init name servers */);
struct evdns_base *dns = evdns_base_new(base, EVDNS_BASE_INITIALIZE_NAMESERVERS);
struct evdns_request *req = NULL;
tt_assert(base);
@ -1004,6 +1004,59 @@ end:
event_base_free(inactive_base);
}
static void
dns_initialize_nameservers_test(void *arg)
{
struct basic_test_data *data = arg;
struct event_base *base = data->base;
struct evdns_base *dns = NULL;
dns = evdns_base_new(base, 0);
tt_assert(dns);
tt_int_op(evdns_base_get_nameserver_addr(dns, 0, NULL, 0), ==, -1);
evdns_base_free(dns, 0);
dns = evdns_base_new(base, EVDNS_BASE_INITIALIZE_NAMESERVERS);
tt_assert(dns);
tt_int_op(evdns_base_get_nameserver_addr(dns, 0, NULL, 0), ==, sizeof(struct sockaddr));
end:
if (dns)
evdns_base_free(dns, 0);
}
#ifndef _WIN32
#define RESOLV_FILE "empty-resolv.conf"
static void
dns_nameservers_no_default_test(void *arg)
{
struct basic_test_data *data = arg;
struct event_base *base = data->base;
struct evdns_base *dns = NULL;
int ok = access(RESOLV_FILE, R_OK);
tt_assert(ok);
dns = evdns_base_new(base, 0);
tt_assert(dns);
tt_int_op(evdns_base_get_nameserver_addr(dns, 0, NULL, 0), ==, -1);
/* We cannot test
* EVDNS_BASE_INITIALIZE_NAMESERVERS|EVDNS_BASE_NAMESERVERS_NO_DEFAULT
* because we cannot mock "/etc/resolv.conf" (yet). */
evdns_base_resolv_conf_parse(dns,
DNS_OPTIONS_ALL|DNS_OPTION_NAMESERVERS_NO_DEFAULT, RESOLV_FILE);
tt_int_op(evdns_base_get_nameserver_addr(dns, 0, NULL, 0), ==, -1);
evdns_base_resolv_conf_parse(dns, DNS_OPTIONS_ALL, RESOLV_FILE);
tt_int_op(evdns_base_get_nameserver_addr(dns, 0, NULL, 0), ==, sizeof(struct sockaddr));
end:
if (dns)
evdns_base_free(dns, 0);
}
#endif
/* === Test for bufferevent_socket_connect_hostname */
static int total_connected_or_failed = 0;
@ -2332,6 +2385,13 @@ struct testcase_t dns_testcases[] = {
{ "disable_when_inactive_no_ns", dns_disable_when_inactive_no_ns_test,
TT_FORK|TT_NEED_BASE, &basic_setup, NULL },
{ "initialize_nameservers", dns_initialize_nameservers_test,
TT_FORK|TT_NEED_BASE, &basic_setup, NULL },
#ifndef _WIN32
{ "nameservers_no_default", dns_nameservers_no_default_test,
TT_FORK|TT_NEED_BASE, &basic_setup, NULL },
#endif
{ "getaddrinfo_async", test_getaddrinfo_async,
TT_FORK|TT_NEED_BASE, &basic_setup, (char*)"" },
{ "getaddrinfo_cancel_stress", test_getaddrinfo_async_cancel_stress,