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Happy Eyeballs: add resolution time delay

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HEv3 describes conditions on when first connect attempts shall be
started.
https://www.ietf.org/archive/id/draft-ietf-happy-happyeyeballs-v3-01.html
Chapter 4.2

libcurl now waits 50ms for AAAA and HTTPS results (when requested) to
return before continuing with the connect.

Added HTTPS-RR to the "was resolved" information info message. Changed
logging of HTTPS-RR to a one-liner with RFC 9460 like formatting. This
way the user can see if/what was resolved and used in connecting.

Closes #21354
This commit is contained in:
Stefan Eissing 2026-04-17 10:26:25 +02:00 • committed by Daniel Stenberg
parent 70a159527c
commit 809dda3a37
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GPG key ID: 5CC908FDB71E12C2
13 changed files with 272 additions and 158 deletions
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86
lib/cf-dns.c
View file

@ -28,6 +28,7 @@
#include "cfilters.h"
#include "connect.h"
#include "dnscache.h"
#include "httpsrr.h"
#include "curl_trc.h"
#include "progress.h"
#include "url.h"
@ -138,11 +139,24 @@ static void cf_dns_report(struct Curl_cfilter *cf,
break;
default:
curlx_dyn_init(&tmp, 1024);
infof(data, "Host %s:%d was resolved.", dns->hostname, dns->port);
infof(data, "Host %s:%u was resolved.", dns->hostname, dns->port);
#ifdef CURLRES_IPV6
cf_dns_report_addr(data, &tmp, "IPv6: ", AF_INET6, dns->addr);
#endif
cf_dns_report_addr(data, &tmp, "IPv4: ", AF_INET, dns->addr);
#ifdef USE_HTTPSRR
if(!dns->hinfo)
infof(data, "HTTPS-RR: -");
else if(!Curl_httpsrr_applicable(data, dns->hinfo))
infof(data, "HTTPS-RR: not applicable");
else {
CURLcode result = Curl_httpsrr_print(&tmp, dns->hinfo);
if(!result)
infof(data, "HTTPS-RR: %s", curlx_dyn_ptr(&tmp));
else
infof(data, "Error printing HTTPS-RR information");
}
#endif
curlx_dyn_free(&tmp);
break;
}
@ -205,6 +219,41 @@ static CURLcode cf_dns_start(struct Curl_cfilter *cf,
}
}
#define CURL_HEV3_RESOLVE_DELAY_MS 50
static bool cf_dns_ready_to_connect(struct Curl_cfilter *cf,
struct Curl_easy *data)
{
struct cf_dns_ctx *ctx = cf->ctx;
if(ctx->resolv_result)
return TRUE;
else if(ctx->dns)
return TRUE;
#ifdef USE_CURL_ASYNC
else {
/* We want AAAA answer as we prefer ipv6. If a sub-filter desires
* HTTPS-RR, we check for that query as well. */
uint8_t wanted_answers = CURL_DNSQ_AAAA;
if(Curl_conn_cf_wants_httpsrr(cf, data))
wanted_answers |= CURL_DNSQ_HTTPS;
/* Note: if a query was never started, it is considered to have
* an answer (e.g. a negative one). */
if(Curl_resolv_has_answers(data, ctx->resolv_id, wanted_answers))
return TRUE;
/* If the wanted answers are not available after a delay,
* we let the connect attempts start anyway. */
return Curl_resolv_elapsed_ms(data, ctx->resolv_id) >=
CURL_HEV3_RESOLVE_DELAY_MS;
}
#else
(void)data;
DEBUGASSERT(0); /* We should not come here */
return FALSE;
#endif /* USE_CURL_ASYNC */
}
static CURLcode cf_dns_connect(struct Curl_cfilter *cf,
struct Curl_easy *data,
bool *done)
@ -225,9 +274,6 @@ static CURLcode cf_dns_connect(struct Curl_cfilter *cf,
if(!ctx->dns && !ctx->resolv_result) {
ctx->resolv_result =
Curl_resolv_take_result(data, ctx->resolv_id, &ctx->dns);
if(!ctx->dns && !ctx->resolv_result)
CURL_TRC_CF(data, cf, "DNS resolution ongoing for %s:%u",
ctx->hostname, ctx->port);
}
if(ctx->resolv_result) {
@ -244,19 +290,23 @@ static CURLcode cf_dns_connect(struct Curl_cfilter *cf,
cf_dns_report(cf, data, ctx->dns);
}
if(!cf_dns_ready_to_connect(cf, data)) {
return CURLE_OK;
}
if(cf->next && !cf->next->connected) {
bool sub_done;
CURLcode result = Curl_conn_cf_connect(cf->next, data, &sub_done);
CURL_TRC_CF(data, cf, "connect subfilters -> %d, done=%d",
result, sub_done);
if(result || !sub_done)
return result;
DEBUGASSERT(sub_done);
}
/* sub filter chain is connected */
CURL_TRC_CF(data, cf, "connected filter chain below");
if(ctx->complete_resolve && !ctx->dns && !ctx->resolv_result) {
/* This filter only connects when it has resolved everything. */
CURL_TRC_CF(data, cf, "delay connect until resolve complete");
return CURLE_OK;
}
*done = TRUE;
@ -536,30 +586,6 @@ static const struct Curl_addrinfo *cf_dns_get_nth_ai(
return NULL;
}
bool Curl_conn_dns_has_any_ai(struct Curl_easy *data, int sockindex)
{
struct Curl_cfilter *cf = data->conn->cfilter[sockindex];
(void)data;
for(; cf; cf = cf->next) {
if(cf->cft == &Curl_cft_dns) {
struct cf_dns_ctx *ctx = cf->ctx;
if(ctx->resolv_result)
return FALSE;
else if(ctx->dns)
return !!ctx->dns->addr;
else
#ifdef USE_IPV6
return Curl_resolv_get_ai(data, ctx->resolv_id, AF_INET, 0) ||
Curl_resolv_get_ai(data, ctx->resolv_id, AF_INET6, 0);
#else
return !!Curl_resolv_get_ai(data, ctx->resolv_id, AF_INET, 0);
#endif
}
}
return FALSE;
}
/* Return the addrinfo at `index` for the given `family` from the
* first "resolve" filter underneath `cf`. If the DNS resolving is
* not done yet or if no address for the family exists, returns NULL.