Drop the per-request pre-resolve that slowed crawls on non-default ports (#181)

back_solve() resolved the raw "host:port" authority once per backing
request through check_hostname_dns() — an uncached getaddrinfo whose
result was only logged (host_wait() is always synchronous now). The
connect path already strips the port and resolves through the DNS cache,
so this lookup was pure overhead. On resolvers that don't fail fast on
the malformed "host:port" name (search-domain expansion, DNS timeouts)
it added a per-request stall: the reported slowness. Mirrors on port 80,
or with the port omitted, avoided the bad name and stayed fast.

Remove back_solve() and its debug-only lookup; keep the synchronous
host_wait() gate. Add a DNS self-test pinning that the cache/connect
path resolves "host:port" as the bare host.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

src/htsback.c

@@ -2050,13 +2050,9 @@ int back_add(struct_back * sback, httrackp * opt, cache_back * cache, const char
 
       if (!back_trylive(opt, cache, sback, p)) {
 #if HTS_XGETHOST
-#if HDEBUG
-        printf("back_solve..\n");
-#endif
-        back[p].status = STATUS_WAIT_DNS;       // tentative de résolution du nom de host
-        soc = INVALID_SOCKET;   // pas encore ouverte
-        back_solve(opt, &back[p]);      // préparer
-        if (host_wait(opt, &back[p])) { // prêt, par ex fichier ou dispo dans dns
+        back[p].status = STATUS_WAIT_DNS; // host name resolution attempt
+        soc = INVALID_SOCKET;             // not opened yet
+        if (host_wait(opt, &back[p])) {   // ready (file, or cached dns)
 #if HDEBUG
           printf("ok, dns cache ready..\n");
 #endif
@@ -2199,37 +2195,9 @@ int back_add(struct_back * sback, httrackp * opt, cache_back * cache, const char
 }
 
 #if HTS_XGETHOST
-// attendre que le host (ou celui du proxy) ait été résolu
-// si c'est un fichier, la résolution est immédiate
-// idem pour ftp://
-void back_solve(httrackp * opt, lien_back * back) {
-  assertf(opt != NULL);
-  assertf(back != NULL);
-  if ((!strfield(back->url_adr, "file://"))
-      && !strfield(back->url_adr, "ftp://")
-    ) {
-    const char *a;
-
-    if (!(back->r.req.proxy.active))
-      a = back->url_adr;
-    else
-      a = back->r.req.proxy.name;
-    assertf(a != NULL);
-    a = jump_protocol_const(a);
-    if (check_hostname_dns(a)) {
-      hts_log_print(opt, LOG_DEBUG, "resolved: %s", a);
-    } else {
-      hts_log_print(opt, LOG_DEBUG, "failed to resolve: %s", a);
-    }
-  }
-}
-
-// détermine si le host a pu être résolu
-int host_wait(httrackp * opt, lien_back * back) {
-  // Always synchronous. No more background DNS resolution
-  // (does not really improve performances)
-  return 1;
-}
+// Resolution is synchronous inside the connect path; no pre-resolve step, so
+// the host is always immediately ready.
+int host_wait(httrackp *opt, lien_back *back) { return 1; }
 #endif
 
 // élimine les fichiers non html en backing (anticipation)

src/htsback.h

@@ -138,7 +138,6 @@ LLint back_transferred(LLint add, struct_back * sback);
 
 // hostback
 #if HTS_XGETHOST
-void back_solve(httrackp * opt, lien_back * sback);
 int host_wait(httrackp * opt, lien_back * sback);
 #endif
 int back_checksize(httrackp * opt, lien_back * eback, int check_only_totalsize);

src/htsdns_selftest.c

@@ -297,6 +297,26 @@ int dns_selftests(httrackp *opt) {
     IPV6_resolver = 0;
   }
 
+  /* "host:port" resolves as the bare host: the cache/connect path strips
+     ":port" before both the backend and the cache key (#181). */
+  mock_reset_calls();
+  {
+    SOCaddr a;
+    char ip[64];
+    const char *err = NULL;
+
+    /* cache miss: the backend is hit with the stripped host, not "host:port" */
+    CHECK(hts_dns_resolve2(opt, "v6only.test:8080", &a, &err) != NULL);
+    CHECK(mock_find("v6only.test")->calls == 1);
+    /* the bare host shares that one cache entry (stripped key) */
+    CHECK(hts_dns_resolve2(opt, "v6only.test", &a, &err) != NULL);
+    CHECK(mock_find("v6only.test")->calls == 1);
+    /* a port variant of an already-cached host also hits, right address */
+    CHECK(hts_dns_resolve2(opt, "v4only.test:1234", &a, &err) != NULL);
+    SOCaddr_inetntoa(ip, sizeof(ip), a);
+    CHECK(strcmp(ip, "1.2.3.4") == 0);
+  }
+
   /* newhttp_addr() must connect to the addr_index-th address, not always the
      first: this is what back_connect_next relies on to reach the fallback. */
   {