1 files changed, 53 insertions, 0 deletions
diff --git a/libpod/network/util/ip_calc.go b/libpod/network/util/ip_calc.go
new file mode 100644
index 000000000..a27ddf78b
--- /dev/null
+++ b/libpod/network/util/ip_calc.go
@@ -0,0 +1,53 @@
+// Copyright 2015 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	"math/big"
+	"net"
+)
+
+// NextIP returns IP incremented by 1
+func NextIP(ip net.IP) net.IP {
+	i := ipToInt(ip)
+	return intToIP(i.Add(i, big.NewInt(1)))
+}
+
+// PrevIP returns IP decremented by 1
+func PrevIP(ip net.IP) net.IP {
+	i := ipToInt(ip)
+	return intToIP(i.Sub(i, big.NewInt(1)))
+}
+
+// Cmp compares two IPs, returning the usual ordering:
+// a < b : -1
+// a == b : 0
+// a > b : 1
+func Cmp(a, b net.IP) int {
+	aa := ipToInt(a)
+	bb := ipToInt(b)
+	return aa.Cmp(bb)
+}
+
+func ipToInt(ip net.IP) *big.Int {
+	if v := ip.To4(); v != nil {
+		return big.NewInt(0).SetBytes(v)
+	}
+	return big.NewInt(0).SetBytes(ip.To16())
+}
+
+func intToIP(i *big.Int) net.IP {
+	return net.IP(i.Bytes())
+}