2 files changed, 28 insertions, 0 deletions
diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 101df6b90..54480ee8d 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -10107,6 +10107,27 @@ as is, and other byte values are converted to &`\xNN`&, for example a
 byte value 127 is converted to &`\x7f`&.
 
 
+.new
+.vitem &*${ipv6denorm:*&<&'string'&>&*}*&
+.cindex "&%ipv6denorm%& expansion item"
+.cindex "IP address" normalisation
+This expands an IPv6 address to a full eight-element colon-separated set
+of hex digits including leading zeroes.
+A trailing ipv4-style dotted-decimal set is converted to hex.
+Pure IPv4 addresses are converted to IPv4-mapped IPv6.
+
+.vitem &*${ipv6norm:*&<&'string'&>&*}*&
+.cindex "&%ipv6norm%& expansion item"
+.cindex "IP address" normalisation
+.cindex "IP address" "canonical form"
+This converts an IPv6 address to canonical form.
+Leading zeroes of groups are omitted, and the longest
+set of zero-valued groups is replaced with a double colon.
+A trailing ipv4-style dotted-decimal set is converted to hex.
+Pure IPv4 addresses are converted to IPv4-mapped IPv6.
+.wen
+
+
 .vitem &*${lc:*&<&'string'&>&*}*&
 .cindex "case forcing in strings"
 .cindex "string" "case forcing"
diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff
index a7185a4e2..ca65c98ea 100644
--- a/doc/doc-txt/NewStuff
+++ b/doc/doc-txt/NewStuff
@@ -17,6 +17,13 @@ Version 4.87
 
  3. Transports now take a "max_parallel" option, to limit concurrency.
 
+ 4. Expansion operators ${ipv6norm:<string>} and ${ipv6denorm:<string>}.
+    The latter expands to a 8-element colon-sep set of hex digits including
+    leading zeroes. A trailing ipv4-style dotted-decimal set is converted
+    to hex.  Pure ipv4 addresses are converted to IPv4-mapped IPv6.
+    The former operator strips leading zeroes and collapses the longest
+    set of 0-groups to a double-colon.
+
 
 Version 4.86
 ------------