[newlib-cygwin] Cygwin: resolver: Fix to match response ID with request ID

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=905f51d7978e09b8f21d7442c58751fdf775c637

commit 905f51d7978e09b8f21d7442c58751fdf775c637
Author: Anton Lavrentiev via Cygwin-patches <cygwin-patches@cygwin.com>
Date:   Tue Jan 18 17:39:15 2022 -0500

    Cygwin: resolver: Fix to match response ID with request ID
    
    In case when the native OS resolver is used (via os_query) the returned
    response ID is always 0.  It should actually match the ID passed in to
    res_send() in the DNS request header.  This patch fixes that

Diff:
---
 winsup/cygwin/libc/minires-os-if.c | 6 +++++-
 winsup/cygwin/libc/minires.c       | 7 ++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/libc/minires-os-if.c b/winsup/cygwin/libc/minires-os-if.c
index c4183db9c..8d3178f70 100644
--- a/winsup/cygwin/libc/minires-os-if.c
+++ b/winsup/cygwin/libc/minires-os-if.c
@@ -189,10 +189,14 @@ static int cygwin_query(res_state statp, const char * DomName, int Class, int Ty
   DWORD section;
   int len, counts[4] = {0, 0, 0, 0}, debug = statp->options & RES_DEBUG;
   unsigned char * dnptrs[256], * ptr;
+  unsigned short Id = 0;
 
   dnptrs[0] = AnsPtr;
   dnptrs[1] = NULL;
 
+  if (AnsLength >= 2)
+    memcpy(&Id, AnsPtr, 2);
+
   memset(AnsPtr, 0, AnsLength);
 
   if (Class != ns_c_in) {
@@ -294,7 +298,7 @@ static int cygwin_query(res_state statp, const char * DomName, int Class, int Ty
 done:
   if (HFIXEDSZ <= AnsLength) {
     ptr = AnsPtr;
-    PUTSHORT(0, ptr); /* Id */
+    PUTSHORT(Id, ptr);
     PUTSHORT((QR << 8) + RA + RD, ptr);
     for (section = 0; section < DIM(counts); section++) {
       PUTSHORT(counts[section], ptr);
diff --git a/winsup/cygwin/libc/minires.c b/winsup/cygwin/libc/minires.c
index fdc6087f5..b540f6a1b 100644
--- a/winsup/cygwin/libc/minires.c
+++ b/winsup/cygwin/libc/minires.c
@@ -450,6 +450,8 @@ int res_nsend( res_state statp, const unsigned char * MsgPtr,
       ptr += len;
       GETSHORT(Type, ptr);
       GETSHORT(Class, ptr);
+      if (AnsLength >= 2)
+          memcpy(AnsPtr, MsgPtr, 2);
       return ((os_query_t *) statp->os_query)(statp, DomName, Class, Type, AnsPtr, AnsLength);
     }
     else {
@@ -709,8 +711,11 @@ int res_nquery( res_state statp, const char * DomName, int Class, int Type,
   statp->res_h_errno = NETDB_SUCCESS;
 
   /* If a hook exists to a native implementation, use it */
-  if (statp->os_query)
+  if (statp->os_query) {
+    if (AnsLength >= 2)
+        memset(AnsPtr, 0/*Id*/, 2);
     return ((os_query_t *) statp->os_query)(statp, DomName, Class, Type, AnsPtr, AnsLength);
+  }
 
   if ((len = res_nmkquery (statp, QUERY, DomName, Class, Type,
 			   0, 0, 0, packet, PACKETSZ)) < 0)