[PATCH] resovl: Avoid duplicate query if search list contains '.' (option 1)

[Carlos Peón Costa]

The same query is performed twice under some contidions:

* The domain name has enough dots to be queried 'as is'.
* The 'as is' response is NXDOMAIN
* The search list contains root domain '.'

e.g.: LOCALDOMAIN="." RES_OPTIONS="ndots:1" ./gethostbyname null.example.org

This is the simplest solution (IMO), but I'll send option 2 removing 'root_on_list'
var and reusing 'tried_as_is', as *I think* they both serve the same purpose.

The thing is so small and harmless that I didn't file a bug, let me know if it's
apropiate to do so.

---
 resolv/res_query.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/resolv/res_query.c b/resolv/res_query.c
index 039c25a3c3..29ae85e71b 100644
--- a/resolv/res_query.c
+++ b/resolv/res_query.c
@@ -433,8 +433,11 @@ __res_context_search (struct resolv_context *ctx,
 			   domain.  */
 			if (dname[0] == '.')
 				dname++;
-			if (dname[0] == '\0')
+			if (dname[0] == '\0') {
 				root_on_list++;
+				if (tried_as_is)
+					continue;
+			}
 
 			ret = __res_context_querydomain
 			  (ctx, name, dname, class, type,
-- 
2.52.0