DSCP: document; hex print; -bI:dscp

4 files changed, 31 insertions, 0 deletions

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 64aac1ae5..15a8f3550 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -2938,6 +2938,7 @@ if this is required. If the &%bi_command%& option is not set, calling Exim with
 &%-bi%& is a no-op.
 
 .new
+. // Keep :help first, then the rest in alphabetical order
 .vitem &%-bI:help%&
 .oindex "&%-bI:help%&"
 .cindex "querying exim information"
@@ -2947,6 +2948,12 @@ consumption.  This one is not.  The &%-bI:help%& option asks Exim for a
 synopsis of supported options beginning &`-bI:`&.  Use of any of these
 options shall cause Exim to exit after producing the requested output.
 
+.vitem &%-bI:dscp%&
+.oindex "&%-bI:dscp%&"
+.cindex "DSCP" "values"
+This option causes Exim to emit an alphabetically sorted list of all
+recognised DSCP names.
+
 .vitem &%-bI:sieve%&
 .oindex "&%-bI:sieve%&"
 .cindex "Sieve filter" "capabilities"
@@ -22094,6 +22101,22 @@ See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
 details.
 
 
+.new
+.option dscp smtp string unset
+.cindex "DCSP"
+.cindex "DiffServ"
+This option causes the DSCP value associated with a socket to be set to one
+of a number of fixed strings.  The &%-bI:dscp%& option may be used to ask
+Exim which values it knows of.  Common values include &`throughput`&,
+&`mincost`&, and on newer systems &`ef`&, &`af41`&, ...
+
+The outbound packets from Exim will be marked with this value in the header
+(for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
+that these packets will have any effect, not be stripped by networking
+equipment, or do much of anything without cooperation with your Network
+Engineer and those of all network operators between the source and destination.
+.wen
+
 
 .option fallback_hosts smtp "string list" unset
 .cindex "fallback" "hosts specified on transport"
diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 34f940592..1e8063bf3 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -16,6 +16,8 @@ PP/04 First step towards DNSSEC, provide $sender_host_dnssec for
       $sender_host_name and config options to manage this, and basic check
       routines.
 
+PP/05 DSCP support for outbound connections.
+
 
 Exim version 4.80
 -----------------
diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff
index 093feee72..2aaf56232 100644
--- a/doc/doc-txt/NewStuff
+++ b/doc/doc-txt/NewStuff
@@ -39,6 +39,11 @@ Version 4.81
 
     Current status: work-in-progress; $sender_host_dnssec variable added.
 
+ 5. DSCP support for outbound connections: on a transport using the smtp driver,
+    set "dscp = ef", for instance, to cause the connections to have the relevant
+    DSCP (IPv4 TOS or IPv6 TCLASS) value in the header.  Supported values depend
+    upon system libraries.  "exim -bI:dscp" to list the ones Exim knows of.
+
 
 Version 4.80
 ------------
diff --git a/doc/doc-txt/OptionLists.txt b/doc/doc-txt/OptionLists.txt
index 20d8dbdc5..1c7881e76 100644
--- a/doc/doc-txt/OptionLists.txt
+++ b/doc/doc-txt/OptionLists.txt
@@ -187,6 +187,7 @@ driver                               string          unset         authenticator
                                                      unset         routers           4.00
                                                      unset         transports
 drop_cr                              boolean         false         main              4.00 became a no-op in 4.21
+dscp                                 string          unset         smtp              4.81
 dsn_from                             string*         +             main              4.67
 envelope_to_add                      boolean         false         transports
 envelope_to_remove                   boolean         true          main