From 1dc228c872974d7eafc34b53816e973e00224351 Mon Sep 17 00:00:00 2001
From: kedixa <1204837541@qq.com>
Date: Tue, 9 Apr 2019 07:37:43 +0800
Subject: [PATCH 05/10] getaddrinfo: avoid infinite loop in case of
 NXDOMAIN(#240) (#242)

There are two possible causes for infinite loops fo NXDOMAIN, based on how many dots are in the domain name (one for < ARES_OPT_NDOTS and one for >= ARES_OPT_NDOTS), where it will repeat the same query over and over as the hquery->next_domain doesn't increment.

Fix By: @kedixa
---
 ares_getaddrinfo.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/ares_getaddrinfo.c b/ares_getaddrinfo.c
index ebaeda8..16c8b38 100644
--- a/ares_getaddrinfo.c
+++ b/ares_getaddrinfo.c
@@ -122,7 +122,7 @@ void ares_getaddrinfo(ares_channel channel,
   hquery->callback = callback;
   hquery->arg = arg;
   hquery->timeouts = 0;
-  hquery->next_domain = 0;
+  hquery->next_domain = -1; /* see next_dns_lookup for more info  */
   hquery->remaining = 0;
 
   /* Host file lookup */
@@ -279,11 +279,20 @@ static void next_dns_lookup(struct host_query *hquery) {
   char *s = NULL;
   int is_s_allocated = 0;
   int status;
-
-  if (( as_is_first(hquery) && hquery->next_domain == 0) ||
-      (!as_is_first(hquery) && hquery->next_domain ==
-       hquery->channel->ndomains)) {
-    s = hquery->name;
+  /* if next_domain == -1 and as_is_first is true, try hquery->name */
+  if(hquery->next_domain == -1) {
+    if(as_is_first(hquery)) {
+      s = hquery->name;
+    }
+    hquery->next_domain = 0;
+  }
+  /* if as_is_first is false, try hquery->name at last */
+  if(!s && hquery->next_domain == hquery->channel->ndomains) {
+    if(!as_is_first(hquery)) {
+      s = hquery->name;
+    }
+    /* avoid infinite loop */
+    hquery->next_domain++;
   }
 
   if (!s && hquery->next_domain < hquery->channel->ndomains) {
-- 
2.16.4