Docs: add note on system_filter forced expansion fail

[users/jgh/exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 8303848c8e3777b59c9aa1cb013bb7ebebae76d3..1bc2028d50637596802ff2da4a494154ec50e838 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -12607,6 +12607,13 @@ validating resolver (e.g. unbound, or bind with suitable configuration).
 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
 mechanism in the list, then this variable will be false.
 
+.new
+This requires that your system resolver library support EDNS0 (and that
+DNSSEC flags exist in the system headers).  If the resolver silently drops
+all EDNS0 options, then this will have no effect.  OpenBSD's asr resolver
+is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
+.wen
+
 
 .vitem &$sender_host_name$&
 .vindex "&$sender_host_name$&"
@@ -14665,6 +14672,7 @@ record in the authoritative section is used instead.
 .option dns_use_edns0 main integer -1
 .cindex "DNS" "resolver options"
 .cindex "DNS" "EDNS0"
+.cindex "DNS" "OpenBSD
 If this option is set to a non-negative number then Exim will initialise the
 DNS resolver library to either use or not use EDNS0 extensions, overriding
 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
@@ -14672,6 +14680,12 @@ on.
 
 If the resolver library does not support EDNS0 then this option has no effect.
 
+.new
+OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
+means that DNSSEC will not work with Exim on that platform either, unless Exim
+is linked against an alternative DNS client library.
+.wen
+
 
 .option drop_cr main boolean false
 This is an obsolete option that is now a no-op. It used to affect the way Exim
@@ -16871,6 +16885,9 @@ generates any deliveries to files or pipes, or any new mail messages, the
 appropriate &%system_filter_..._transport%& option(s) must be set, to define
 which transports are to be used. Details of this facility are given in chapter
 &<<CHAPsystemfilter>>&.
+.new
+A forced expansion failure results in no filter operation.
+.wen
 
 
 .option system_filter_directory_transport main string&!! unset
@@ -25875,7 +25892,7 @@ running, the transport may get an IP for the name for its authentication
 check which does not match the connection peer IP.
 No authentication will then be done, despite the names being identical.
 
-For such cases use a separate transport which alwats authenticates.
+For such cases use a separate transport which always authenticates.
 .wen
 
 .cindex "AUTH" "on MAIL command"