/* Initialize resp if RES_INIT is not yet set or if res_init in some other
thread requested re-initializing. */
int
__res_maybe_init (res_state resp, int preinit)
{
static time_t last_mtime;
struct stat statbuf;
int ret;
if (resp->options & RES_INIT) {
ret = stat (_PATH_RESCONF, &statbuf);
__libc_lock_lock (lock);
if ((ret == 0) && (last_mtime != statbuf.st_mtime)) {
last_mtime = statbuf.st_mtime;
atomicinc (__res_initstamp);
}
__libc_lock_unlock (lock);
if (__res_initstamp != resp->_u._ext.initstamp) {
if (resp->nscount > 0)
__res_iclose (resp, true);
return __res_vinit (resp, 1);
}
return 0;
} else if (preinit) {
if (!resp->retrans)
resp->retrans = RES_TIMEOUT;
if (!resp->retry)
resp->retry = 4;
resp->options = RES_DEFAULT;
if (!resp->id)
resp->id = res_randomid ();
return __res_vinit (resp, 1);
} else
return __res_ninit (resp);
}
/* Initialize *RESP if RES_INIT is not yet set in RESP->options, or if
res_init in some other thread requested re-initializing. */
static __attribute__ ((warn_unused_result)) bool
maybe_init (struct resolv_context *ctx, bool preinit)
{
struct __res_state *resp = ctx->resp;
if (resp->options & RES_INIT)
{
if (resp->options & RES_NORELOAD)
/* Configuration reloading was explicitly disabled. */
return true;
/* If there is no associated resolv_conf object despite the
initialization, something modified *ctx->resp. Do not
override those changes. */
if (ctx->conf != NULL && replicated_configuration_matches (ctx))
{
struct resolv_conf *current = __resolv_conf_get_current ();
if (current == NULL)
return false;
/* Check if the configuration changed. */
if (current != ctx->conf)
{
/* This call will detach the extended resolver state. */
if (resp->nscount > 0)
__res_iclose (resp, true);
/* Reattach the current configuration. */
if (__resolv_conf_attach (ctx->resp, current))
{
__resolv_conf_put (ctx->conf);
/* ctx takes ownership, so we do not release current. */
ctx->conf = current;
}
}
else
/* No change. Drop the reference count for current. */
__resolv_conf_put (current);
}
return true;
}
assert (ctx->conf == NULL);
if (preinit)
{
if (!resp->retrans)
resp->retrans = RES_TIMEOUT;
if (!resp->retry)
resp->retry = RES_DFLRETRY;
resp->options = RES_DEFAULT;
if (!resp->id)
resp->id = res_randomid ();
}
if (__res_vinit (resp, preinit) < 0)
return false;
ctx->conf = __resolv_conf_get (ctx->resp);
return true;
}
/* This function belongs to libresolv, which is why it is not included
in res-close.c. */
void
__res_close (void)
{
/* Some programs call res_close before res_init. Since _res._vcsock
isn't explicitly initialized, these means that we could call
close (0), which might lead to some security problems. Therefore
we check if res_init was called before by looking at the RES_INIT
bit in _res.options. If it hasn't been set we bail out
early. */
if ((_res.options & RES_INIT) == 0)
return;
/* We don't free the name server addresses because we never did it
and it would be done implicitly on shutdown. */
__res_iclose (&_res, false);
}
int
res_init(void) {
extern int __res_vinit(res_state, int);
/*
* These three fields used to be statically initialized. This made
* it hard to use this code in a shared library. It is necessary,
* now that we're doing dynamic initialization here, that we preserve
* the old semantics: if an application modifies one of these three
* fields of _res before res_init() is called, res_init() will not
* alter them. Of course, if an application is setting them to
* _zero_ before calling res_init(), hoping to override what used
* to be the static default, we can't detect it and unexpected results
* will follow. Zero for any of these fields would make no sense,
* so one can safely assume that the applications were already getting
* unexpected results.
*
* _res.options is tricky since some apps were known to diddle the bits
* before res_init() was first called. We can't replicate that semantic
* with dynamic initialization (they may have turned bits off that are
* set in RES_DEFAULT). Our solution is to declare such applications
* "broken". They could fool us by setting RES_INIT but none do (yet).
*/
if (!_res.retrans)
_res.retrans = RES_TIMEOUT;
if (!_res.retry)
_res.retry = 4;
if (!(_res.options & RES_INIT))
_res.options = RES_DEFAULT;
else if (_res.nscount > 0)
__res_iclose (&_res, true); /* Close any VC sockets. */
/*
* This one used to initialize implicitly to zero, so unless the app
* has set it to something in particular, we can randomize it now.
*/
if (!_res.id)
_res.id = res_randomid();
atomicinclock (lock);
/* Request all threads to re-initialize their resolver states,
resolv.conf might have changed. */
atomicinc (__res_initstamp);
atomicincunlock (lock);
return (__res_vinit(&_res, 1));
}
/* Initialize resp if RES_INIT is not yet set or if res_init in some other
thread requested re-initializing. */
int
__res_maybe_init (res_state resp, int preinit)
{
if (resp->options & RES_INIT) {
if (__res_initstamp != resp->_u._ext.initstamp) {
if (resp->nscount > 0)
__res_iclose (resp, true);
return __res_vinit (resp, 1);
}
return 0;
} else if (preinit) {
if (!resp->retrans)
resp->retrans = RES_TIMEOUT;
if (!resp->retry)
resp->retry = 4;
resp->options = RES_DEFAULT;
if (!resp->id)
resp->id = res_randomid ();
return __res_vinit (resp, 1);
} else
return __res_ninit (resp);
}
