ADDED:
* netx now has a ton of netmask conversion functions for IPv4 netmasks.
  (IPv6 doesn't really *have* netmasks, so it was intentionally
  excluded).
This commit is contained in:
brent saner 2025-10-13 15:56:07 -04:00
parent 3c49a5b70a
commit e101758187
Signed by: bts
GPG Key ID: 8C004C2F93481F6B
5 changed files with 580 additions and 0 deletions

13
netx/consts_nix.go Normal file
View File

@ -0,0 +1,13 @@
//go:build !windows
package netx
import (
`golang.org/x/sys/unix`
)
const (
AFUnspec uint16 = unix.AF_UNSPEC
AFInet uint16 = unix.AF_INET
AFInet6 uint16 = unix.AF_INET6
)

13
netx/consts_windows.go Normal file
View File

@ -0,0 +1,13 @@
//go:build windows
package netx
import (
`golang.org/x/sys/windows`
)
const (
AFUnspec uint16 = windows.AF_UNSPEC
AFInet uint16 = windows.AF_INET
AFInet6 uint16 = windows.AF_INET6
)

10
netx/errors.go Normal file
View File

@ -0,0 +1,10 @@
package netx
import (
`errors`
)
var (
ErrBadMask4Str error = errors.New("netx: unknown/bad IPv4 netmask dotted quad")
ErrBadNetFam error = errors.New("netx: unknown/bad IP network family")
)

410
netx/funcs.go Normal file
View File

@ -0,0 +1,410 @@
package netx
import (
`math/bits`
`net`
`net/netip`
`strconv`
`strings`
`go4.org/netipx`
)
/*
AddrRfc returns an RFC-friendly string from an IP address ([net/netip.Addr]).
If addr is an IPv4 address, it will simmply be the string representation (e.g. "203.0.113.1").
If addr is an IPv6 address, it will be enclosed in brackets (e.g. "[2001:db8::1]").
If the version can't be determined, rfcStr will be an empty string.
*/
func AddrRfc(addr netip.Addr) (rfcStr string) {
if addr.Is4() {
rfcStr = addr.String()
} else if addr.Is6() {
rfcStr = "[" + addr.String() + "]"
}
return
}
/*
Cidr4ToIPMask takes an IPv4 CIDR/bit size/prefix length and returns the [net.IPMask].
It's (essentially) the inverse of [net.IPMask.Size].
See also:
* [Cidr4ToMask]
* [Cidr4ToStr]
Inverse of [IPMask4ToCidr].
*/
func Cidr4ToIPMask(cidr uint8) (ipMask net.IPMask, err error) {
if cidr > 32 {
err = ErrBadNetFam
return
}
ipMask = net.CIDRMask(int(cidr), 32)
return
}
/*
Cidr4ToMask takes an IPv4 CIDR/bit size/prefix length and returns the netmask *in bitmask form*.
See also:
* [Cidr4ToIPMask]
* [Cidr4ToStr]
Inverse of [Mask4ToCidr].
*/
func Cidr4ToMask(cidr uint8) (mask uint32, err error) {
if cidr > 32 {
err = ErrBadNetFam
return
}
// COULD do (1 << 32) - (1 << (32 - ip.Bits())) instead but in EXTREME edge cases that could cause an overflow.
// We're basically converting the CIDR size ("number of bits"/"number of ones") to an integer mask ("number AS bits")
mask = uint32(0xffffffff) << uint32(32-cidr)
return
}
/*
Cidr4ToStr is a convenience wrapper around [IPMask4ToStr]([Cidr4ToMask](cidr)).
See also:
* [Cidr4ToIPMask]
* [Cidr4ToMask]
Inverse of [Mask4StrToCidr].
*/
func Cidr4ToStr(cidr uint8) (maskStr string, err error) {
var ipMask net.IPMask
if ipMask, err = Cidr4ToIPMask(cidr); err != nil {
return
}
if maskStr, err = IPMask4ToStr(ipMask); err != nil {
return
}
return
}
/*
GetAddrFamily returns the network family of a [net/netip.Addr].
See also [GetIpFamily].
If addr is not a "valid" IP address or the version can't be determined, family will be AFUnspec (usually 0x00/0).
*/
func GetAddrFamily(addr netip.Addr) (family uint16) {
family = AFUnspec
if !addr.IsValid() {
return
}
if addr.Is4() {
family = AFInet
} else if addr.Is6() {
family = AFInet6
} else {
return
}
return
}
/*
GetIpFamily returns the network family of a [net.IP].
See also [GetAddrFamily].
If ip is not a "valid" IP address or the version can't be determined,
family will be [golang.org/x/sys/unix.AF_UNSPEC] or [golang.org/x/sys/windows.AF_UNSPEC] depending on platform (usually 0x00/0).
*/
func GetIpFamily(ip net.IP) (family uint16) {
var ok bool
var addr netip.Addr
if addr, ok = netipx.FromStdIP(ip); !ok {
return
}
family = GetAddrFamily(addr)
return
}
/*
IpRfc returns an RFC-friendly string from an IP address ([net.IP]).
If ip is an IPv4 address, it will simmply be the string representation (e.g. "203.0.113.1").
If ip is an IPv6 address, it will be enclosed in brackets (e.g. "[2001:db8::1]").
If the version can't be determined, rfcStr will be an empty string.
*/
func IpRfc(ip net.IP) (rfcStr string) {
if ip.To4() != nil {
rfcStr = ip.To4().String()
} else if ip.To16() != nil {
rfcStr = "[" + ip.To16().String() + "]"
}
return
}
/*
IPMask4ToCidr returns a CIDR prefix size/bit size/bit length from a [net.IPMask].
See also:
* [IPMask4ToMask]
* [IPMask4ToStr]
Inverse of [Cidr4ToIPMask].
*/
func IPMask4ToCidr(ipMask net.IPMask) (cidr uint8, err error) {
var ones int
var total int
ones, total = ipMask.Size()
if total != 32 {
err = ErrBadNetFam
return
}
if ones > 32 {
err = ErrBadNetFam
return
}
cidr = uint8(ones)
return
}
/*
IPMask4ToMask returns the mask *in bitmask form* from a [net.IPMask].
See also:
* [IPMask4ToCidr]
* [IPMask4ToStr]
Inverse of [Mask4ToIPMask].
*/
func IPMask4ToMask(ipMask net.IPMask) (mask uint32, err error) {
var cidr uint8
if cidr, err = IPMask4ToCidr(ipMask); err != nil {
return
}
if mask, err = Cidr4ToMask(cidr); err != nil {
return
}
return
}
/*
IPMask4ToStr returns a string representation of an IPv4 netmask (e.g. "255.255.255.0" for a /24) from a [net.IPMask].
See also:
* [IPMask4ToCidr]
* [IPMask4ToMask]
Inverse of [Mask4StrToIPMask].
*/
func IPMask4ToStr(ipMask net.IPMask) (maskStr string, err error) {
var idx int
var b []byte
var quads []string = make([]string, 4)
b = []byte(ipMask)
if len(b) != 4 {
err = ErrBadNetFam
return
}
for idx = 0; idx < len(b); idx++ {
quads[idx] = strconv.Itoa(int(b[idx]))
}
maskStr = strings.Join(quads, ".")
return
}
/*
Mask4ToCidr converts an IPv4 netmask *in bitmask form* to a CIDR prefix size/bit size/bit length.
See also:
* [Mask4ToIPMask]
* [Mask4ToStr]
Inverse of [Cidr4ToMask].
*/
func Mask4ToCidr(mask uint32) (cidr uint8, err error) {
cidr = 32 - uint8(bits.LeadingZeros32(mask))
return
}
/*
Mask4ToIPMask returns mask *in bitmask form* as a [net.IPMask].
See also:
* [Mask4ToCidr]
* [Mask4ToStr]
Inverse of [IPMask4ToMask].
*/
func Mask4ToIPMask(mask uint32) (ipMask net.IPMask, err error) {
var cidr uint8
if cidr, err = Mask4ToCidr(mask); err != nil {
return
}
ipMask = net.CIDRMask(int(cidr), 32)
return
}
/*
Mask4ToStr returns a string representation of an IPv4 netmask (e.g. "255.255.255.0" for a /24) from a netmask *in bitmask form*.
See also:
* [Mask4ToCidr]
* [Mask4ToIPMask]
Inverse of [Mask4StrToMask].
*/
func Mask4ToStr(mask uint32) (maskStr string, err error) {
var ipMask net.IPMask
if ipMask, err = Mask4ToIPMask(mask); err != nil {
return
}
if maskStr, err = IPMask4ToStr(ipMask); err != nil {
return
}
return
}
/*
Mask4StrToCidr parses a "dotted-quad" IPv4 netmask (e.g. "255.255.255.0" for a /24) and returns am IPv4 CIDR/bit size/prefix length.
See also:
* [Mask4StrToIPMask]
* [Mask4StrToMask]
Inverse of [Cidr4ToMaskStr].
*/
func Mask4StrToCidr(maskStr string) (cidr uint8, err error) {
var ipMask net.IPMask
if ipMask, err = Mask4StrToIPMask(maskStr); err != nil {
return
}
if cidr, err = IPMask4ToCidr(ipMask); err != nil {
return
}
return
}
/*
Mask4StrToIPMask parses a "dotted-quad" IPv4 netmask (e.g. "255.255.255.0" for a /24) and returns a [net.IPMask].
See also:
* [Mask4StrToCidr]
* [Mask4StrToMask]
Inverse of [IPMask4ToStr].
*/
func Mask4StrToIPMask(maskStr string) (mask net.IPMask, err error) {
var idx int
var s string
var u64 uint64
var b []byte = make([]byte, 4)
var sl []string = strings.Split(maskStr, ".")
if len(sl) != 4 {
err = ErrBadMask4Str
return
}
// A net.IPMask is just a []byte.
for idx = 0; idx < len(sl); idx++ {
s = sl[idx]
if u64, err = strconv.ParseUint(s, 10, 8); err != nil {
return
}
b[idx] = byte(u64)
}
mask = net.IPMask(b)
return
}
/*
Mask4StrToMask parses a "dotted-quad" IPv4 netmask (e.g. "255.255.255.0" for a /24) and returns a netmask *in bitmask form*.
See also:
* [Mask4StrToCidr]
* [Mask4StrToIPMask]
Inverse of [Mask4ToStr].
*/
func Mask4StrToMask(maskStr string) (mask uint32, err error) {
var ipMask net.IPMask
if ipMask, err = Mask4StrToIPMask(maskStr); err != nil {
return
}
if mask, err = IPMask4ToMask(ipMask); err != nil {
return
}
return
}

134
netx/funcs_test.go Normal file
View File

@ -0,0 +1,134 @@
package netx
import (
`math`
`net`
`net/netip`
"testing"
)
func TestFuncsIP(t *testing.T) {
var err error
var ip net.IP
var addr netip.Addr
var ipFamily uint16
var tgtFamily uint16
var addrFamily uint16
// IPv4 on even indexes, IPv6 on odd.
for idx, s := range []string{
"203.0.113.10",
"2001:db8::203:0:113:10",
} {
if ip = net.ParseIP(s); ip == nil {
t.Fatalf("ip %s not valid", s)
}
if addr, err = netip.ParseAddr(s); err != nil {
t.Fatalf("addr %s not valid", s)
}
ipFamily = GetIpFamily(ip)
addrFamily = GetAddrFamily(addr)
if ipFamily == AFUnspec {
t.Fatalf("GetIpFamily: Failed on IP %s (unspecified family)", s)
}
if addrFamily == AFUnspec {
t.Fatalf("GetAddrFamily: Failed on IP %s (unspecified family)", s)
}
switch idx%2 == 0 {
case true:
tgtFamily = AFInet
case false:
tgtFamily = AFInet6
}
if ipFamily != tgtFamily {
t.Fatalf("GetIpFamily: Failed on IP %s (expected %d, got %d)", s, AFInet, tgtFamily)
}
if addrFamily != tgtFamily {
t.Fatalf("GetAddrFamily: Failed on IP %s (expected %d, got %d)", s, AFInet, tgtFamily)
}
}
}
func TestFuncsMask(t *testing.T) {
var err error
var cidr uint8
var mask uint32
var maskStr string
var ipMask net.IPMask
var cidrTgt uint8 = 32
var maskTgt uint32 = math.MaxUint32
var maskStrTgt string = "255.255.255.255"
var ipMaskTgt net.IPMask = net.IPMask{255, 255, 255, 255}
// To CIDR
if cidr, err = Mask4ToCidr(maskTgt); err != nil {
t.Fatal(err)
} else if cidr != cidrTgt {
t.Fatalf("Mask4ToCidr: cidr %d != cidrTgt %d", cidr, cidrTgt)
}
if cidr, err = IPMask4ToCidr(ipMaskTgt); err != nil {
t.Fatal(err)
} else if cidr != cidrTgt {
t.Fatalf("IPMask4ToCidr: cidr %d != cidrTgt %d", cidr, cidrTgt)
}
if cidr, err = Mask4StrToCidr(maskStrTgt); err != nil {
t.Fatal(err)
} else if cidr != cidrTgt {
t.Fatalf("Mask4StrToCidr cidr %d != cidrTgt %d", cidr, cidrTgt)
}
// To net.IPMask
if ipMask, err = Cidr4ToIPMask(cidrTgt); err != nil {
t.Fatal(err)
} else if ipMaskTgt.String() != ipMask.String() {
t.Fatalf("Cidr4ToIPMask ipMask %s != ipMaskTgt %s", ipMask.String(), ipMaskTgt.String())
}
if ipMask, err = Mask4ToIPMask(maskTgt); err != nil {
t.Fatal(err)
} else if ipMaskTgt.String() != ipMask.String() {
t.Fatalf("Mask4ToIPMask ipMask %s != ipMaskTgt %s", ipMask.String(), ipMaskTgt.String())
}
if ipMask, err = Mask4StrToIPMask(maskStrTgt); err != nil {
t.Fatal(err)
} else if ipMaskTgt.String() != ipMask.String() {
t.Fatalf("Mask4StrToIPMask ipMask %s != ipMaskTgt %s", ipMask.String(), ipMaskTgt.String())
}
// To bitmask
if mask, err = Cidr4ToMask(cidrTgt); err != nil {
t.Fatal(err)
} else if mask != maskTgt {
t.Fatalf("Cidr4ToMask mask %d != maskTgt %d", mask, maskTgt)
}
if mask, err = IPMask4ToMask(ipMaskTgt); err != nil {
t.Fatal(err)
} else if mask != maskTgt {
t.Fatalf("IPMask4ToMask mask %d != maskTgt %d", mask, maskTgt)
}
if mask, err = Mask4StrToMask(maskStrTgt); err != nil {
t.Fatal(err)
} else if mask != maskTgt {
t.Fatalf("Mask4StrToMask mask %d != maskTgt %d", mask, maskTgt)
}
// To string
if maskStr, err = Cidr4ToStr(cidrTgt); err != nil {
t.Fatal(err)
} else if maskStr != maskStrTgt {
t.Fatalf("Cidr4ToStr maskStr %s != maskStrTgt %s", maskStr, maskStrTgt)
}
if maskStr, err = IPMask4ToStr(ipMaskTgt); err != nil {
t.Fatal(err)
} else if maskStr != maskStrTgt {
t.Fatalf("IPMask4ToStr maskStr %s != maskStrTgt %s", maskStr, maskStrTgt)
}
if maskStr, err = Mask4ToStr(maskTgt); err != nil {
t.Fatal(err)
} else if maskStr != maskStrTgt {
t.Fatalf("Mask4ToStr maskStr %s != maskStrTgt %s", maskStr, maskStrTgt)
}
}