Implement the pseudo dns lookup type "zns" for ${dnsdb lookups.

[users/jgh/exim.git] / doc / doc-txt / NewStuff

diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff
index 7421078bc6b93a9b79bdfba6553c74849f54137a..ee9f55c31fd1d0a64a6a3c526a1df66e81d54129 100644 (file)
--- a/doc/doc-txt/NewStuff
+++ b/doc/doc-txt/NewStuff
@@ -1,4 +1,4 @@
-$Cambridge: exim/doc/doc-txt/NewStuff,v 1.10 2004/11/17 14:32:25 ph10 Exp $
+$Cambridge: exim/doc/doc-txt/NewStuff,v 1.12 2004/11/19 09:45:54 ph10 Exp $
 
 New Features in Exim
 --------------------
@@ -90,6 +90,45 @@ Version 4.44
     to find the amount of free space (only true for experimental systems), the
     space value is -1.
 
+11. It is now permitted to omit both strings after an "if" condition; if the
+    condition is true, the result is the string "true". As before, when the
+    second string is omitted, a false condition yields an empty string. This
+    makes it less cumbersome to write custom ACL and router conditions. For
+    example, instead of
+
+      condition = ${if eq {$acl_m4}{1}{yes}{no}}
+
+    or the shorter form
+
+      condition = ${if eq {$acl_m4}{1}{yes}}
+
+    (because the second string has always defaulted to ""), you can now write
+
+      condition = ${if eq {$acl_m4}{1}}
+
+    Previously this was a syntax error.
+
+12. There is now a new "record type" that can be specified in dnsdb lookups. It
+    is "zns" (for "zone NS"). It performs a lookup for NS records on the given
+    domain, but if none are found, it removes the first component of the domain
+    name, and tries again. This process continues until NS records are found
+    or there are no more components left (or there's a DNS error). In other
+    words, it may return the name servers for a top-level domain, but it never
+    returns the root name servers. If there are no NS records for the top-level
+    domain, the lookup fails.
+
+    For example, ${lookup dnsdb{zns=xxx.quercite.com}} returns the name
+    servers for quercite.com, whereas ${lookup dnsdb{zns=xxx.edu}} returns
+    the name servers for edu, assuming in each case that there are no NS
+    records for the full domain name.
+
+    You should be careful about how you use this lookup because, unless the
+    top-level domain does not exist, the lookup will always return some host
+    names. The sort of use to which this might be put is for seeing if the name
+    servers for a given domain are on a blacklist. You can probably assume that
+    the name servers for the high-level domains such as .com or .co.uk are not
+    going to be on such a list.
+
 
 Version 4.43
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