jimlib/ipv4.tcl      | 23 +++++++++++++++++++++++
 jimlib/net-utils.tcl | 27 +++++++++++++++++++++++++++

diff --git a/jimlib/ipv4.tcl b/jimlib/ipv4.tcl
new file mode 100644
index 0000000000000000000000000000000000000000..724a9b8e543a05cb6797923cb2fc73b6a6b66dbbd5ed1565ada1b91df833896d
--- /dev/null
+++ b/jimlib/ipv4.tcl
@@ -0,0 +1,23 @@
+package provide ipv4 1.0
+
+namespace eval ipv4 {
+
+proc contract {addr} {
+    set octets [split $addr .]
+    if {[llength $octets] != 4} {
+        error "invalid format"
+    }
+    set rv [list]
+    foreach octet $octets {
+        if {[string is integer -strict $octet] == 0} {
+            error "non integer IPv4 octet"
+        }
+        if {($octet < 0) || ($octet > 255)} {
+            error "out of range IPv4 octet"
+        }
+        lappend rv [expr {0 + $octet}]
+    }
+    return [join $rv .]
+}
+
+}
diff --git a/jimlib/net-utils.tcl b/jimlib/net-utils.tcl
index 5c24cda56c385789b75835ea969941f7c120462b66520d922fcad36e51ae73aa..cb217988cd92c2790de17b9601525c529633ab2cc88124c8036586481c1540b3 100644
--- a/jimlib/net-utils.tcl
+++ b/jimlib/net-utils.tcl
@@ -35,3 +35,30 @@         }
     }
     return $addrs
 }
+
+proc parse-ip {addr} {
+    set addr [string map {/ " "} $addr]
+    set addr [split $addr " "]
+    set prefixlen ""
+    switch [llength $addr] {
+        1 {}
+        2 {lassign $addr addr prefixlen}
+        default {error "bad address format"}
+    }
+    set maxlen 128
+    if {[string first : $addr] == -1} {
+        package require ipv4
+        set maxlen 32
+        set addr [ipv4::contract $addr]
+    } else {
+        package require ipv6
+        if {[ipv6::isIpv6 $addr] != 1} {error "invalid IPv6 format"}
+        set addr [ipv6::contract $addr]
+    }
+    package require check-utils
+    set prefixlen [parse-int $prefixlen $maxlen]
+    if {($prefixlen < 0) || ($prefixlen > $maxlen)} {
+        error "prefixlen is not in acceptable range"
+    }
+    return [list $addr $prefixlen]
+}