diff --git a/vendor/github.com/spf13/pflag/ipmask.go b/vendor/github.com/spf13/pflag/ipmask.go
new file mode 100644
index 0000000..5bd44bd
--- /dev/null
+++ b/vendor/github.com/spf13/pflag/ipmask.go
@@ -0,0 +1,122 @@
+package pflag
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+)
+
+// -- net.IPMask value
+type ipMaskValue net.IPMask
+
+func newIPMaskValue(val net.IPMask, p *net.IPMask) *ipMaskValue {
+	*p = val
+	return (*ipMaskValue)(p)
+}
+
+func (i *ipMaskValue) String() string { return net.IPMask(*i).String() }
+func (i *ipMaskValue) Set(s string) error {
+	ip := ParseIPv4Mask(s)
+	if ip == nil {
+		return fmt.Errorf("failed to parse IP mask: %q", s)
+	}
+	*i = ipMaskValue(ip)
+	return nil
+}
+
+func (i *ipMaskValue) Type() string {
+	return "ipMask"
+}
+
+// ParseIPv4Mask written in IP form (e.g. 255.255.255.0).
+// This function should really belong to the net package.
+func ParseIPv4Mask(s string) net.IPMask {
+	mask := net.ParseIP(s)
+	if mask == nil {
+		if len(s) != 8 {
+			return nil
+		}
+		// net.IPMask.String() actually outputs things like ffffff00
+		// so write a horrible parser for that as well  :-(
+		m := []int{}
+		for i := 0; i < 4; i++ {
+			b := "0x" + s[2*i:2*i+2]
+			d, err := strconv.ParseInt(b, 0, 0)
+			if err != nil {
+				return nil
+			}
+			m = append(m, int(d))
+		}
+		s := fmt.Sprintf("%d.%d.%d.%d", m[0], m[1], m[2], m[3])
+		mask = net.ParseIP(s)
+		if mask == nil {
+			return nil
+		}
+	}
+	return net.IPv4Mask(mask[12], mask[13], mask[14], mask[15])
+}
+
+func parseIPv4Mask(sval string) (interface{}, error) {
+	mask := ParseIPv4Mask(sval)
+	if mask == nil {
+		return nil, fmt.Errorf("unable to parse %s as net.IPMask", sval)
+	}
+	return mask, nil
+}
+
+// GetIPv4Mask return the net.IPv4Mask value of a flag with the given name
+func (f *FlagSet) GetIPv4Mask(name string) (net.IPMask, error) {
+	val, err := f.getFlagType(name, "ipMask", parseIPv4Mask)
+	if err != nil {
+		return nil, err
+	}
+	return val.(net.IPMask), nil
+}
+
+// IPMaskVar defines an net.IPMask flag with specified name, default value, and usage string.
+// The argument p points to an net.IPMask variable in which to store the value of the flag.
+func (f *FlagSet) IPMaskVar(p *net.IPMask, name string, value net.IPMask, usage string) {
+	f.VarP(newIPMaskValue(value, p), name, "", usage)
+}
+
+// IPMaskVarP is like IPMaskVar, but accepts a shorthand letter that can be used after a single dash.
+func (f *FlagSet) IPMaskVarP(p *net.IPMask, name, shorthand string, value net.IPMask, usage string) {
+	f.VarP(newIPMaskValue(value, p), name, shorthand, usage)
+}
+
+// IPMaskVar defines an net.IPMask flag with specified name, default value, and usage string.
+// The argument p points to an net.IPMask variable in which to store the value of the flag.
+func IPMaskVar(p *net.IPMask, name string, value net.IPMask, usage string) {
+	CommandLine.VarP(newIPMaskValue(value, p), name, "", usage)
+}
+
+// IPMaskVarP is like IPMaskVar, but accepts a shorthand letter that can be used after a single dash.
+func IPMaskVarP(p *net.IPMask, name, shorthand string, value net.IPMask, usage string) {
+	CommandLine.VarP(newIPMaskValue(value, p), name, shorthand, usage)
+}
+
+// IPMask defines an net.IPMask flag with specified name, default value, and usage string.
+// The return value is the address of an net.IPMask variable that stores the value of the flag.
+func (f *FlagSet) IPMask(name string, value net.IPMask, usage string) *net.IPMask {
+	p := new(net.IPMask)
+	f.IPMaskVarP(p, name, "", value, usage)
+	return p
+}
+
+// IPMaskP is like IPMask, but accepts a shorthand letter that can be used after a single dash.
+func (f *FlagSet) IPMaskP(name, shorthand string, value net.IPMask, usage string) *net.IPMask {
+	p := new(net.IPMask)
+	f.IPMaskVarP(p, name, shorthand, value, usage)
+	return p
+}
+
+// IPMask defines an net.IPMask flag with specified name, default value, and usage string.
+// The return value is the address of an net.IPMask variable that stores the value of the flag.
+func IPMask(name string, value net.IPMask, usage string) *net.IPMask {
+	return CommandLine.IPMaskP(name, "", value, usage)
+}
+
+// IPMaskP is like IP, but accepts a shorthand letter that can be used after a single dash.
+func IPMaskP(name, shorthand string, value net.IPMask, usage string) *net.IPMask {
+	return CommandLine.IPMaskP(name, shorthand, value, usage)
+}