Documentation and configuration changes

* configure.ac: Remove leftover checks for libresolv.
* doc/upgrade.texi: Document recent changes.

2 files changed, 19 insertions, 17 deletions

diff --git a/configure.ac b/configure.ac
index 5ac9a00b..ec17774c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -53,17 +53,6 @@ MU_DEBUG_MODE
 MF_GCC_QUIRKS
 
 # Checks for libraries.
-dnl Cannot use AC_CHECK_LIB to check for libresolv, because res_query
-dnl can be a macro, so resolv.h needs to be included.
-saved_LIBS=$LIBS
-LIBS="$LIBS -lresolv"
-AC_TRY_LINK([#include <sys/types.h>
-             #include <sys/socket.h>
-             #include <netinet/in.h>
-             #include <resolv.h>],
-            [res_query;],
-            [:],
-            [LIBS=$saved_LIBS])
 AC_CHECK_LIB(socket, socket)
 AC_CHECK_LIB(nsl, gethostbyaddr)
 AC_CHECK_LIB(rt, nanosleep)
diff --git a/doc/upgrade.texi b/doc/upgrade.texi
index 636ed813..c86b879d 100644
--- a/doc/upgrade.texi
+++ b/doc/upgrade.texi
@@ -30,10 +30,15 @@ between the consecutive Mailfromd releases.
 @appendixsec Upgrading from 8.2 to 8.3
 @cindex Upgrading from 8.2 to 8.3
 
-  Version 8.3 contains significant improvements in the DNS
-resolver. In particular, it removes arbitrary limits on the sizes
-of the RRs. Consequently, the following configurations statements
-are withdrawn:
+  In version 8.3 I abandoned the legacy DNS resolver and switched to 
+@dfn{GNU adns}. GNU ands is a standalone resolver library, which provides
+a number of advanced features. It is included in most distributions. The 
+source code of the recent release is available from
+@uref{http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz}.
+
+  This change brought a number of user-visible changes. In particular,
+arbitrary limits on the sizes of the RRs are removed. Consequently,
+the following configurations statements are withdrawn:
 
 @table @code
 @item runtime.max-dns-reply-a
@@ -47,8 +52,16 @@ are withdrawn:
 @item max-callout-mx
 @end table
 
-This version no longer caches results of SPF checks. As the effect,
-the following MFL global variables have been removed:
+  Secondly, the new resolver is less tolerant to deviations from the
+standard. This means that remote DNS misconfigurations that would have
+slipped unnoticed in previous versions, will be noticed by mailfromd
+8.3. For example, a CNAME record pointing to another CNAME is treated
+as an error.
+
+  Another user-visible change is in handling of SPF checks. Previously,
+results if SPF checks were cached in a database. This proved to cause
+more problems than solutions and was removed in this version. As a
+result, the following MFL global variables have been withdrawn:
 
 @table @code
 @item spf_ttl