BZ#16469: resolv: skip leading dot in domain to search

[Alexandre Oliva]

This should only happen if the domain to search is the root,
represented as "." rather than by an empty string.  Skipping it here
prevents libc_res_nquerydomain from duplicating the trailing dot,
which would cause the domain name compression to fail.

No testcase for this one; we can't really exercise this in a controlled
fashion without overriding /etc/resolv.conf.

No regressions on x86_64-linux-gnu.  Ok to install?


for  ChangeLog

	[BZ #16469]
	* resolv/res_query.c (__libc_res_nsearch): Skip leading dot in
	search domain names.
---
 resolv/res_query.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/resolv/res_query.c b/resolv/res_query.c
index 338ad82..0d276b0 100644
--- a/resolv/res_query.c
+++ b/resolv/res_query.c
@@ -413,13 +413,24 @@ __libc_res_nsearch(res_state statp,
 		for (domain = (const char * const *)statp->dnsrch;
 		     *domain && !done;
 		     domain++) {
+			const char *dname = domain[0];
 			searched = 1;
 
-			if (domain[0][0] == '\0' ||
-			    (domain[0][0] == '.' && domain[0][1] == '\0'))
+			/* __libc_res_nquerydoman concatenates name
+			   with dname with a "." in between.  If we
+			   pass it in dname the "." we got from the
+			   configured default search path, we'll end
+			   up with "name..", which won't resolve.
+			   OTOH, passing it "" will result in "name.",
+			   which has the intended effect for both
+			   possible representations of the root
+			   domain.  */
+			if (dname[0] == '.')
+				dname++;
+			if (dname[0] == '\0')
 				root_on_list++;
 
-			ret = __libc_res_nquerydomain(statp, name, *domain,
+			ret = __libc_res_nquerydomain(statp, name, dname,
 						      class, type,
 						      answer, anslen, answerp,
 						      answerp2, nanswerp2,

-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer