Document OpenBSD resolver ignoring EDNS0

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index db4c6e2a2ab4d565df8977459d5a1cd3ddc8ffe3..1ab2bba0a8c9170920cebf7413444517a8cc854a 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.
 
 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 "&$sender_host_name$&"
 
 .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"
 .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
 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.
 
 
 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
 
 .option drop_cr main boolean false
 This is an obsolete option that is now a no-op. It used to affect the way Exim


@@ -25865,6 +25879,19 @@ turned into a permanent error if you wish. In the second case, Exim tries to
 deliver the message unauthenticated.
 .endlist
 
 deliver the message unauthenticated.
 .endlist
 

+.new
+Note that the hostlist test for whether to do authentication can be
+confused if name-IP lookups change between the time the peer is decided
+on and the transport running.  For example, with a manualroute
+router given a host name, and DNS "round-robin" use by that name: if
+the local resolver cache times out between the router and the transport
+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 always authenticates.
+.wen
+

 .cindex "AUTH" "on MAIL command"
 When Exim has authenticated itself to a remote server, it adds the AUTH
 parameter to the MAIL commands it sends, if it has an authenticated sender for
 .cindex "AUTH" "on MAIL command"
 When Exim has authenticated itself to a remote server, it adds the AUTH
 parameter to the MAIL commands it sends, if it has an authenticated sender for


@@ -28080,6 +28107,11 @@ run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
 remaining recipients. The &"discard"& return is not permitted for the
 &%acl_smtp_predata%& ACL.
 
 remaining recipients. The &"discard"& return is not permitted for the
 &%acl_smtp_predata%& ACL.
 

+.new
+If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
+is done on the address and the result determines the SMTP response.
+.wen
+

 
 .cindex "&[local_scan()]& function" "when all recipients discarded"
 The &[local_scan()]& function is always run, even if there are no remaining
 
 .cindex "&[local_scan()]& function" "when all recipients discarded"
 The &[local_scan()]& function is always run, even if there are no remaining