From d95103c467b03fcc0bd6e9835d9f1c7b64f2e28f Mon Sep 17 00:00:00 2001
From: Huw Davies <huw@codeweavers.com>
Date: Thu, 5 Aug 2021 09:56:42 +0100
Subject: [PATCH] iphlpapi: Use DnsQueryConfig() to retrieve the dns servers
 for GetAdaptersAddresses().

Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
---
 dlls/iphlpapi/Makefile.in     |  2 +-
 dlls/iphlpapi/iphlpapi_main.c | 86 ++++++++++++++++++++++-------------
 2 files changed, 56 insertions(+), 32 deletions(-)

diff --git a/dlls/iphlpapi/Makefile.in b/dlls/iphlpapi/Makefile.in
index 3db17289bf4..14a45e419a3 100644
--- a/dlls/iphlpapi/Makefile.in
+++ b/dlls/iphlpapi/Makefile.in
@@ -1,6 +1,6 @@
 MODULE    = iphlpapi.dll
 IMPORTLIB = iphlpapi
-IMPORTS   = advapi32 nsi uuid
+IMPORTS   = advapi32 dnsapi nsi uuid
 EXTRALIBS = $(RESOLV_LIBS) $(KSTAT_LIBS) $(PROCSTAT_LIBS)
 
 C_SRCS = \
diff --git a/dlls/iphlpapi/iphlpapi_main.c b/dlls/iphlpapi/iphlpapi_main.c
index 93efed2ca2e..2c8c1644b78 100644
--- a/dlls/iphlpapi/iphlpapi_main.c
+++ b/dlls/iphlpapi/iphlpapi_main.c
@@ -1395,41 +1395,65 @@ static int get_dns_servers( SOCKADDR_STORAGE *servers, int num, BOOL ip4_only )
 }
 #endif
 
-static ULONG get_dns_server_addresses(PIP_ADAPTER_DNS_SERVER_ADDRESS address, ULONG *len)
+static DWORD dns_servers_query_code( ULONG family )
 {
-    int num = get_dns_servers( NULL, 0, FALSE );
-    DWORD size;
+    if (family == WS_AF_INET) return DnsConfigDnsServersIpv4;
+    if (family == WS_AF_INET6) return DnsConfigDnsServersIpv6;
+    return DnsConfigDnsServersUnspec;
+}
 
-    size = num * (sizeof(IP_ADAPTER_DNS_SERVER_ADDRESS) + sizeof(SOCKADDR_STORAGE));
-    if (!address || *len < size)
+static ULONG get_dns_server_addresses( ULONG family, IP_ADAPTER_DNS_SERVER_ADDRESS *address, ULONG *len )
+{
+    char buf[FIELD_OFFSET(DNS_ADDR_ARRAY, AddrArray[3])];
+    DNS_ADDR_ARRAY *servers = (DNS_ADDR_ARRAY *)buf;
+    DWORD err, num, i, needed, array_len = sizeof(buf);
+    DWORD query = dns_servers_query_code( family );
+    SOCKADDR_INET *out_addrs;
+
+    for (;;)
     {
-        *len = size;
-        return ERROR_BUFFER_OVERFLOW;
-    }
-    *len = size;
-    if (num > 0)
-    {
-        PIP_ADAPTER_DNS_SERVER_ADDRESS addr = address;
-        SOCKADDR_STORAGE *sock_addrs = (SOCKADDR_STORAGE *)(address + num);
-        int i;
-
-        get_dns_servers( sock_addrs, num, FALSE );
-
-        for (i = 0; i < num; i++, addr = addr->Next)
+        err = DnsQueryConfig( query, 0, NULL, NULL, servers, &array_len );
+        if (err != ERROR_SUCCESS && err != ERROR_MORE_DATA) goto err;
+        num = (array_len - FIELD_OFFSET(DNS_ADDR_ARRAY, AddrArray[0])) / sizeof(DNS_ADDR);
+        needed = num * (sizeof(IP_ADAPTER_DNS_SERVER_ADDRESS) + sizeof(*out_addrs));
+        if (!address || *len < needed)
         {
-            addr->u.s.Length = sizeof(*addr);
-            if (sock_addrs[i].ss_family == WS_AF_INET6)
-                addr->Address.iSockaddrLength = sizeof(SOCKADDR_IN6);
-            else
-                addr->Address.iSockaddrLength = sizeof(SOCKADDR_IN);
-            addr->Address.lpSockaddr = (SOCKADDR *)(sock_addrs + i);
-            if (i == num - 1)
-                addr->Next = NULL;
-            else
-                addr->Next = addr + 1;
+            *len = needed;
+            err = ERROR_BUFFER_OVERFLOW;
+            goto err;
+        }
+        if (!err) break;
+
+        if ((char *)servers != buf) heap_free( servers );
+        servers = heap_alloc( array_len );
+        if (!servers)
+        {
+            err = ERROR_NOT_ENOUGH_MEMORY;
+            goto err;
         }
     }
-    return ERROR_SUCCESS;
+
+    *len = needed;
+    out_addrs = (SOCKADDR_INET *)(address + num);
+    for (i = 0; i < num; i++)
+    {
+        address[i].u.s.Length = sizeof(*address);
+        address[i].u.s.Reserved = 0;
+        address[i].Next = NULL;
+        address[i].Address.iSockaddrLength = servers->AddrArray[i].Data.DnsAddrUserDword[0];
+        if (address[i].Address.iSockaddrLength > sizeof(*out_addrs))
+            address[i].Address.iSockaddrLength = 0;
+        address[i].Address.lpSockaddr = (SOCKADDR *)(out_addrs + i);
+        memcpy( out_addrs + i, servers->AddrArray[i].MaxSa, address[i].Address.iSockaddrLength );
+        memset( (BYTE *)(out_addrs + i) + address[i].Address.iSockaddrLength, 0,
+                sizeof(*out_addrs) - address[i].Address.iSockaddrLength );
+        if (i) address[i - 1].Next = address + i;
+    }
+    err = ERROR_SUCCESS;
+
+err:
+    if ((char *)servers != buf) heap_free( servers );
+    return err;
 }
 
 #ifdef HAVE_STRUCT___RES_STATE
@@ -1506,7 +1530,7 @@ ULONG WINAPI DECLSPEC_HOTPATCH GetAdaptersAddresses(ULONG family, ULONG flags, P
         /* Since DNS servers aren't really per adapter, get enough space for a
          * single copy of them.
          */
-        get_dns_server_addresses(NULL, &dns_server_size);
+        get_dns_server_addresses( family, NULL, &dns_server_size );
         total_size += dns_server_size;
     }
     /* Since DNS suffix also isn't really per adapter, get enough space for a
@@ -1538,7 +1562,7 @@ ULONG WINAPI DECLSPEC_HOTPATCH GetAdaptersAddresses(ULONG family, ULONG flags, P
         if (dns_server_size)
         {
             firstDns = (PIP_ADAPTER_DNS_SERVER_ADDRESS)((BYTE *)first_aa + total_size - dns_server_size - dns_suffix_size);
-            get_dns_server_addresses(firstDns, &dns_server_size);
+            get_dns_server_addresses( family, firstDns, &dns_server_size );
             for (aa = first_aa; aa; aa = aa->Next)
             {
                 if (aa->IfType != IF_TYPE_SOFTWARE_LOOPBACK && aa->OperStatus == IfOperStatusUp)