[glibc] support: Provide a way to clear the RA bit in DNS server responses

[Florian Weimer <fw@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=08443b19965f48862b02c2fd7b33a39d66daf2ff

commit 08443b19965f48862b02c2fd7b33a39d66daf2ff
Author: Florian Weimer <fweimer@redhat.com>
Date:   Wed Oct 14 10:54:39 2020 +0200

    support: Provide a way to clear the RA bit in DNS server responses

Diff:
---
 support/resolv_test.c | 4 +++-
 support/resolv_test.h | 4 ++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/support/resolv_test.c b/support/resolv_test.c
index e343c4b516..9878a040a3 100644
--- a/support/resolv_test.c
+++ b/support/resolv_test.c
@@ -181,7 +181,9 @@ resolv_response_init (struct resolv_response_builder *b,
   b->buffer[2] |= b->query_buffer[2] & 0x01; /* Copy the RD bit.  */
   if (flags.tc)
     b->buffer[2] |= 0x02;
-  b->buffer[3] = 0x80 | flags.rcode; /* Always set RA.  */
+  b->buffer[3] = flags.rcode;
+  if (!flags.clear_ra)
+    b->buffer[3] |= 0x80;
   if (flags.ad)
     b->buffer[3] |= 0x20;
 
diff --git a/support/resolv_test.h b/support/resolv_test.h
index c46de32ff4..31a5c1c3e7 100644
--- a/support/resolv_test.h
+++ b/support/resolv_test.h
@@ -148,6 +148,10 @@ struct resolv_response_flags
   /* If true, the AD (authenticated data) flag will be set.  */
   bool ad;
 
+  /* If true, do not set the RA (recursion available) flag in the
+     response.  */
+  bool clear_ra;
+
   /* Initial section count values.  Can be used to artificially
      increase the counts, for malformed packet testing.*/
   unsigned short qdcount;