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resolver: simplify fetch response handling

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There is no longer a need to decide whether a fetch response should be
prepended or appended to the fetch response list. As query response data
is stored directly in the fetch context object, responses containing a
sigrdataset no longer need to be ordered first. Remove the code
implementing this logic.

Additionally, the distinction between `fetchstate_done` and
`fetchstate_sendevents` is no longer needed. New clients
`dns_fetchresponse_t` can be attached any time to the fetch context
until `fctx__done()` is called, since there is no dependency on the
first fetch response in the list. This simplifies the code and reduces
(just a bit) locking usage.
This commit is contained in:
Colin Vidal 2026-01-15 16:30:59 +01:00
parent b764d43203
commit a5b2a8c931
1 changed files with 11 additions and 32 deletions
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43
lib/dns/resolver.c
View file

@ -299,9 +299,8 @@ struct tried {
#define RESQUERY_SENDING(q) ((q)->sends > 0)
typedef enum {
fetchstate_active = 0,
fetchstate_done,
fetchstate_sendevents /*%< Fetch completion events posted. */
fetchstate_active,
fetchstate_done /*%< Fetch completion events posted. */
} fetchstate_t;
typedef enum {
@ -508,7 +507,7 @@ struct fetchctx {
((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_GLUING) != 0)
#define ADDRWAIT(f) \
((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_ADDRWAIT) != 0)
#define SHUTTINGDOWN(f) ((f)->state >= fetchstate_done)
#define SHUTTINGDOWN(f) ((f)->state == fetchstate_done)
#define WANTCACHE(f) \
((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_WANTCACHE) != 0)
#define WANTNCACHE(f) \
@ -1667,7 +1666,7 @@ fctx_sendevents(fetchctx_t *fctx, isc_result_t result) {
LOCK(&fctx->lock);
REQUIRE(fctx->state == fetchstate_sendevents);
REQUIRE(fctx->state == fetchstate_done);
if (result == ISC_R_SUCCESS) {
clone_results(fctx);
@ -1804,11 +1803,11 @@ fctx__done(fetchctx_t *fctx, isc_result_t result, const char *func,
LOCK(&fctx->lock);
}
/* We need to do this under the lock for intra-thread synchronization */
if (fctx->state == fetchstate_sendevents) {
if (fctx->state == fetchstate_done) {
UNLOCK(&fctx->lock);
return false;
}
fctx->state = fetchstate_sendevents;
fctx->state = fetchstate_done;
FCTX_ATTR_CLR(fctx, FCTX_ATTR_ADDRWAIT);
/* The fctx will get deleted either here or in get_attached_fctx() */
@ -4430,9 +4429,6 @@ resume_qmin(void *arg) {
}
dns_name_copy(fname, dns_fixedname_name(
&fctx->resp_foundname));
LOCK(&fctx->lock);
fctx->state = fetchstate_done;
UNLOCK(&fctx->lock);
goto cleanup;
}
@ -4493,22 +4489,18 @@ resume_qmin(void *arg) {
dns_name_copy(fname, dns_fixedname_name(
&fctx->resp_foundname));
LOCK(&fctx->lock);
fctx->state = fetchstate_done;
if (result == DNS_R_CNAME &&
dns_rdataset_isassociated(&rdataset) &&
fctx->type == dns_rdatatype_cname)
{
LOCK(&fctx->lock);
fctx_success_unref(fctx);
result = ISC_R_SUCCESS;
/*
* Yes, we're not releasing the lock, because
* `fctx_success_unref()` directly goes into the
* `fctx__done()` flow which expect fctx to be
* locked in case of success. Spicy...
* locked in case of success.
*/
} else {
UNLOCK(&fctx->lock);
}
goto cleanup;
@ -4770,16 +4762,7 @@ fctx_add_event(fetchctx_t *fctx, isc_loop_t *loop, const isc_sockaddr_t *client,
isc_mem_attach(fctx->mctx, &resp->mctx);
resp->foundname = dns_fixedname_initname(&resp->fname);
/*
* Store the sigrdataset in the first resp in case it is needed
* by any of the events.
*/
if (resp->sigrdataset != NULL) {
ISC_LIST_PREPEND(fctx->resps, resp, link);
} else {
ISC_LIST_APPEND(fctx->resps, resp, link);
}
ISC_LIST_APPEND(fctx->resps, resp, link);
}
static void
@ -5799,7 +5782,6 @@ answer_response:
dns_name_copy(val->name, dns_fixedname_name(&fctx->resp_foundname));
dns_db_attach(fctx->cache, &fctx->resp_db);
dns_db_transfernode(fctx->cache, &node, &fctx->resp_node);
fctx->state = fetchstate_done;
done = true;
@ -6245,7 +6227,6 @@ rctx_cachename(respctx_t *rctx, dns_message_t *message, dns_name_t *name) {
dns_name_copy(name, dns_fixedname_name(&fctx->resp_foundname));
dns_db_attach(fctx->cache, &fctx->resp_db);
dns_db_transfernode(fctx->cache, &node, &fctx->resp_node);
fctx->state = fetchstate_done;
FCTX_ATTR_SET(fctx, FCTX_ATTR_HAVEANSWER);
}
@ -6432,7 +6413,6 @@ rctx_ncache(respctx_t *rctx) {
dns_name_copy(name, dns_fixedname_name(&fctx->resp_foundname));
dns_db_attach(fctx->cache, &fctx->resp_db);
dns_db_transfernode(fctx->cache, &node, &fctx->resp_node);
fctx->state = fetchstate_done;
unlock:
UNLOCK(&fctx->lock);
@ -10710,8 +10690,6 @@ dns_resolver_dumpfetches(dns_resolver_t *res, isc_statsformat_t format,
char typebuf[DNS_RDATATYPE_FORMATSIZE];
char timebuf[1024];
unsigned int resp_count = 0, query_count = 0;
const char *fetchstatestr[] = { "active", "done",
"sendevents" };
LOCK(&fctx->lock);
dns_name_print(fctx->name, fp);
@ -10722,7 +10700,8 @@ dns_resolver_dumpfetches(dns_resolver_t *res, isc_statsformat_t format,
dns_rdatatype_format(fctx->type, typebuf, sizeof(typebuf));
fprintf(fp, "/%s (%s), 0x%x: started %s, ", typebuf,
fetchstatestr[fctx->state], fctx->options, timebuf);
fctx->state == fetchstate_done ? "done" : "active",
fctx->options, timebuf);
ISC_LIST_FOREACH(fctx->resps, resp, link) {
resp_count++;