net: add network interface identification API

This CL introduces new API into package net to identify the network
interface.  A functionality of new API is very similar to RFC3493 -
"Interface Identification".

R=r, gri, bradfitz, robert.hencke, fullung, rsc
CC=golang-dev
https://golang.org/cl/4437087

src/pkg/net/Makefile

@@ -10,6 +10,7 @@ GOFILES=\
 	dnsmsg.go\
 	fd_$(GOOS).go\
 	hosts.go\
+	interface.go\
 	ip.go\
 	ipsock.go\
 	iprawsock.go\
@@ -27,6 +28,7 @@ GOFILES_freebsd=\
 	dnsconfig.go\
 	fd.go\
 	file.go\
+	interface_bsd.go\
 	newpollserver.go\
 	port.go\
 	sendfile_stub.go\
@@ -41,6 +43,7 @@ GOFILES_darwin=\
 	dnsconfig.go\
 	fd.go\
 	file.go\
+	interface_bsd.go\
 	newpollserver.go\
 	port.go\
 	sendfile_stub.go\
@@ -55,12 +58,14 @@ GOFILES_linux=\
 	dnsconfig.go\
 	fd.go\
 	file.go\
+	interface_linux.go\
 	newpollserver.go\
 	port.go\
 	sendfile_linux.go\
 	sock_linux.go\
 
 GOFILES_plan9=\
+	interface_stub.go\
 	sendfile_stub.go\
 
 ifeq ($(GOARCH),arm)
@@ -75,6 +80,7 @@ endif
 GOFILES_windows=\
 	cgo_stub.go\
 	file_windows.go\
+	interface_stub.go\
 	resolv_windows.go\
 	sendfile_stub.go\
 	sock_windows.go\

src/pkg/net/interface.go

@@ -0,0 +1,133 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Network interface identification
+
+package net
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"syscall"
+)
+
+// A HardwareAddr represents a physical hardware address.
+type HardwareAddr []byte
+
+func (a HardwareAddr) String() string {
+	var buf bytes.Buffer
+	for i, b := range a {
+		if i > 0 {
+			buf.WriteByte(':')
+		}
+		fmt.Fprintf(&buf, "%02x", b)
+	}
+	return buf.String()
+}
+
+// Interface represents a mapping between network interface name
+// and index.  It also represents network interface facility
+// information.
+type Interface struct {
+	Index        int          // positive integer that starts at one, zero is never used
+	MTU          int          // maximum transmission unit
+	Name         string       // e.g., "en0", "lo0", "eth0.100"
+	HardwareAddr HardwareAddr // IEEE MAC-48, EUI-48 and EUI-64 form
+	rawFlags     int
+}
+
+// IsUp returns true if ifi is up.
+func (ifi *Interface) IsUp() bool {
+	if ifi == nil {
+		return false
+	}
+	return ifi.rawFlags&syscall.IFF_UP != 0
+}
+
+// IsLoopback returns true if ifi is a loopback interface.
+func (ifi *Interface) IsLoopback() bool {
+	if ifi == nil {
+		return false
+	}
+	return ifi.rawFlags&syscall.IFF_LOOPBACK != 0
+}
+
+// CanBroadcast returns true if ifi supports a broadcast access
+// capability.
+func (ifi *Interface) CanBroadcast() bool {
+	if ifi == nil {
+		return false
+	}
+	return ifi.rawFlags&syscall.IFF_BROADCAST != 0
+}
+
+// IsPointToPoint returns true if ifi belongs to a point-to-point
+// link.
+func (ifi *Interface) IsPointToPoint() bool {
+	if ifi == nil {
+		return false
+	}
+	return ifi.rawFlags&syscall.IFF_POINTOPOINT != 0
+}
+
+// CanMulticast returns true if ifi supports a multicast access
+// capability.
+func (ifi *Interface) CanMulticast() bool {
+	if ifi == nil {
+		return false
+	}
+	return ifi.rawFlags&syscall.IFF_MULTICAST != 0
+}
+
+// Addrs returns interface addresses for a specific interface.
+func (ifi *Interface) Addrs() ([]Addr, os.Error) {
+	if ifi == nil {
+		return nil, os.NewError("net: invalid interface")
+	}
+	return interfaceAddrTable(ifi.Index)
+}
+
+// Interfaces returns a list of the systems's network interfaces.
+func Interfaces() ([]Interface, os.Error) {
+	return interfaceTable(0)
+}
+
+// InterfaceAddrs returns a list of the system's network interface
+// addresses.
+func InterfaceAddrs() ([]Addr, os.Error) {
+	return interfaceAddrTable(0)
+}
+
+// InterfaceByIndex returns the interface specified by index.
+func InterfaceByIndex(index int) (*Interface, os.Error) {
+	if index <= 0 {
+		return nil, os.NewError("net: invalid interface index")
+	}
+	ift, err := interfaceTable(index)
+	if err != nil {
+		return nil, err
+	}
+	for _, ifi := range ift {
+		return &ifi, nil
+	}
+	return nil, os.NewError("net: no such interface")
+}
+
+// InterfaceByName returns the interface specified by name.
+func InterfaceByName(name string) (*Interface, os.Error) {
+	if name == "" {
+		return nil, os.NewError("net: invalid interface name")
+	}
+	ift, err := interfaceTable(0)
+	if err != nil {
+		return nil, err
+	}
+	for _, ifi := range ift {
+		if name == ifi.Name {
+			return &ifi, nil
+		}
+	}
+	return nil, os.NewError("net: no such interface")
+}

src/pkg/net/interface_bsd.go

@@ -0,0 +1,148 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Network interface identification for BSD variants
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces.  Otheriwse it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, os.Error) {
+	var (
+		tab  []byte
+		e    int
+		msgs []syscall.RoutingMessage
+		ift  []Interface
+	)
+
+	tab, e = syscall.RouteRIB(syscall.NET_RT_IFLIST, ifindex)
+	if e != 0 {
+		return nil, os.NewSyscallError("route rib", e)
+	}
+
+	msgs, e = syscall.ParseRoutingMessage(tab)
+	if e != 0 {
+		return nil, os.NewSyscallError("route message", e)
+	}
+
+	for _, m := range msgs {
+		switch v := m.(type) {
+		case *syscall.InterfaceMessage:
+			if ifindex == 0 || ifindex == int(v.Header.Index) {
+				ifi, err := newLink(v)
+				if err != nil {
+					return nil, err
+				}
+				ift = append(ift, ifi...)
+			}
+		}
+	}
+
+	return ift, nil
+}
+
+func newLink(m *syscall.InterfaceMessage) ([]Interface, os.Error) {
+	var ift []Interface
+
+	sas, e := syscall.ParseRoutingSockaddr(m)
+	if e != 0 {
+		return nil, os.NewSyscallError("route sockaddr", e)
+	}
+
+	for _, s := range sas {
+		switch v := s.(type) {
+		case *syscall.SockaddrDatalink:
+			ifi := Interface{Index: int(m.Header.Index), rawFlags: int(m.Header.Flags)}
+			var name [syscall.IFNAMSIZ]byte
+			for i := 0; i < int(v.Nlen); i++ {
+				name[i] = byte(v.Data[i])
+			}
+			ifi.Name = string(name[:v.Nlen])
+			ifi.MTU = int(m.Header.Data.Mtu)
+			addr := make([]byte, v.Alen)
+			for i := 0; i < int(v.Alen); i++ {
+				addr[i] = byte(v.Data[int(v.Nlen)+i])
+			}
+			ifi.HardwareAddr = addr[:v.Alen]
+			ift = append(ift, ifi)
+		}
+	}
+
+	return ift, nil
+}
+
+// If the ifindex is zero, interfaceAddrTable returns addresses
+// for all network interfaces.  Otherwise it returns addresses
+// for a specific interface.
+func interfaceAddrTable(ifindex int) ([]Addr, os.Error) {
+	var (
+		tab  []byte
+		e    int
+		msgs []syscall.RoutingMessage
+		ifat []Addr
+	)
+
+	tab, e = syscall.RouteRIB(syscall.NET_RT_IFLIST, ifindex)
+	if e != 0 {
+		return nil, os.NewSyscallError("route rib", e)
+	}
+
+	msgs, e = syscall.ParseRoutingMessage(tab)
+	if e != 0 {
+		return nil, os.NewSyscallError("route message", e)
+	}
+
+	for _, m := range msgs {
+		switch v := m.(type) {
+		case *syscall.InterfaceAddrMessage:
+			if ifindex == 0 || ifindex == int(v.Header.Index) {
+				ifa, err := newAddr(v)
+				if err != nil {
+					return nil, err
+				}
+				ifat = append(ifat, ifa...)
+			}
+		}
+	}
+
+	return ifat, nil
+}
+
+func newAddr(m *syscall.InterfaceAddrMessage) ([]Addr, os.Error) {
+	var ifat []Addr
+
+	sas, e := syscall.ParseRoutingSockaddr(m)
+	if e != 0 {
+		return nil, os.NewSyscallError("route sockaddr", e)
+	}
+
+	for _, s := range sas {
+		var ifa IPAddr
+		switch v := s.(type) {
+		case *syscall.SockaddrInet4:
+			ifa.IP = IPv4(v.Addr[0], v.Addr[1], v.Addr[2], v.Addr[3])
+		case *syscall.SockaddrInet6:
+			ifa.IP = make(IP, IPv6len)
+			copy(ifa.IP, v.Addr[:])
+			// NOTE: KAME based IPv6 protcol stack usually embeds
+			// the interface index in the interface-local or link-
+			// local address as the kernel-internal form.
+			if ifa.IP.IsLinkLocalUnicast() ||
+				ifa.IP.IsInterfaceLocalMulticast() ||
+				ifa.IP.IsLinkLocalMulticast() {
+				// remove embedded scope zone ID
+				ifa.IP[2], ifa.IP[3] = 0, 0
+			}
+		}
+		ifat = append(ifat, ifa.toAddr())
+	}
+
+	return ifat, nil
+}

src/pkg/net/interface_linux.go

@@ -0,0 +1,165 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Network interface identification for Linux
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces.  Otheriwse it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, os.Error) {
+	var (
+		ift  []Interface
+		tab  []byte
+		msgs []syscall.NetlinkMessage
+		e    int
+	)
+
+	tab, e = syscall.NetlinkRIB(syscall.RTM_GETLINK, syscall.AF_UNSPEC)
+	if e != 0 {
+		return nil, os.NewSyscallError("netlink rib", e)
+	}
+
+	msgs, e = syscall.ParseNetlinkMessage(tab)
+	if e != 0 {
+		return nil, os.NewSyscallError("netlink message", e)
+	}
+
+	for _, m := range msgs {
+		switch m.Header.Type {
+		case syscall.NLMSG_DONE:
+			goto done
+		case syscall.RTM_NEWLINK:
+			ifim := (*syscall.IfInfomsg)(unsafe.Pointer(&m.Data[0]))
+			if ifindex == 0 || ifindex == int(ifim.Index) {
+				attrs, e := syscall.ParseNetlinkRouteAttr(&m)
+				if e != 0 {
+					return nil, os.NewSyscallError("netlink routeattr", e)
+				}
+				ifi := newLink(attrs, ifim)
+				ift = append(ift, ifi)
+			}
+		}
+	}
+
+done:
+	return ift, nil
+}
+
+func newLink(attrs []syscall.NetlinkRouteAttr, ifim *syscall.IfInfomsg) Interface {
+	ifi := Interface{Index: int(ifim.Index), rawFlags: int(ifim.Flags)}
+	for _, a := range attrs {
+		switch a.Attr.Type {
+		case syscall.IFLA_ADDRESS:
+			var nonzero bool
+			for _, b := range a.Value {
+				if b != 0 {
+					nonzero = true
+				}
+			}
+			if nonzero {
+				ifi.HardwareAddr = a.Value[:]
+			}
+		case syscall.IFLA_IFNAME:
+			ifi.Name = string(a.Value[:])
+		case syscall.IFLA_MTU:
+			ifi.MTU = int(uint32(a.Value[3])<<24 | uint32(a.Value[2])<<16 | uint32(a.Value[1])<<8 | uint32(a.Value[0]))
+		}
+	}
+	return ifi
+}
+
+// If the ifindex is zero, interfaceAddrTable returns addresses
+// for all network interfaces.  Otherwise it returns addresses
+// for a specific interface.
+func interfaceAddrTable(ifindex int) ([]Addr, os.Error) {
+	var (
+		ifat4 []Addr
+		ifat6 []Addr
+		tab   []byte
+		msgs4 []syscall.NetlinkMessage
+		msgs6 []syscall.NetlinkMessage
+		e     int
+		err   os.Error
+	)
+
+	tab, e = syscall.NetlinkRIB(syscall.RTM_GETADDR, syscall.AF_INET)
+	if e != 0 {
+		return nil, os.NewSyscallError("netlink rib", e)
+	}
+	msgs4, e = syscall.ParseNetlinkMessage(tab)
+	if e != 0 {
+		return nil, os.NewSyscallError("netlink message", e)
+	}
+	ifat4, err = addrTable(msgs4, ifindex)
+	if err != nil {
+		return nil, err
+	}
+
+	tab, e = syscall.NetlinkRIB(syscall.RTM_GETADDR, syscall.AF_INET6)
+	if e != 0 {
+		return nil, os.NewSyscallError("netlink rib", e)
+	}
+	msgs6, e = syscall.ParseNetlinkMessage(tab)
+	if e != 0 {
+		return nil, os.NewSyscallError("netlink message", e)
+	}
+	ifat6, err = addrTable(msgs6, ifindex)
+	if err != nil {
+		return nil, err
+	}
+
+	return append(ifat4, ifat6...), nil
+}
+
+func addrTable(msgs []syscall.NetlinkMessage, ifindex int) ([]Addr, os.Error) {
+	var ifat []Addr
+
+	for _, m := range msgs {
+		switch m.Header.Type {
+		case syscall.NLMSG_DONE:
+			goto done
+		case syscall.RTM_NEWADDR:
+			ifam := (*syscall.IfAddrmsg)(unsafe.Pointer(&m.Data[0]))
+			if ifindex == 0 || ifindex == int(ifam.Index) {
+				attrs, e := syscall.ParseNetlinkRouteAttr(&m)
+				if e != 0 {
+					return nil, os.NewSyscallError("netlink routeattr", e)
+				}
+				ifat = append(ifat, newAddr(attrs, int(ifam.Family))...)
+			}
+		}
+	}
+
+done:
+	return ifat, nil
+}
+
+func newAddr(attrs []syscall.NetlinkRouteAttr, family int) []Addr {
+	var ifat []Addr
+
+	for _, a := range attrs {
+		switch a.Attr.Type {
+		case syscall.IFA_ADDRESS:
+			ifa := IPAddr{}
+			switch family {
+			case syscall.AF_INET:
+				ifa.IP = IPv4(a.Value[0], a.Value[1], a.Value[2], a.Value[3])
+			case syscall.AF_INET6:
+				ifa.IP = make(IP, IPv6len)
+				copy(ifa.IP, a.Value[:])
+			}
+			ifat = append(ifat, ifa.toAddr())
+		}
+	}
+
+	return ifat
+}

src/pkg/net/interface_stub.go

@@ -0,0 +1,23 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Network interface identification
+
+package net
+
+import "os"
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces.  Otheriwse it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, os.Error) {
+	return nil, nil
+}
+
+// If the ifindex is zero, interfaceAddrTable returns addresses
+// for all network interfaces.  Otherwise it returns addresses
+// for a specific interface.
+func interfaceAddrTable(ifindex int) ([]Addr, os.Error) {
+	return nil, nil
+}

src/pkg/net/interface_test.go

@@ -0,0 +1,90 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bytes"
+	"testing"
+)
+
+func sameInterface(i, j *Interface) bool {
+	if i == nil || j == nil {
+		return false
+	}
+	if i.Index == j.Index && i.Name == j.Name && bytes.Equal(i.HardwareAddr, j.HardwareAddr) {
+		return true
+	}
+	return false
+}
+
+func interfaceFlagsString(ifi *Interface) string {
+	fs := "<"
+	if ifi.IsUp() {
+		fs += "UP,"
+	}
+	if ifi.CanBroadcast() {
+		fs += "BROADCAST,"
+	}
+	if ifi.IsLoopback() {
+		fs += "LOOPBACK,"
+	}
+	if ifi.IsPointToPoint() {
+		fs += "POINTOPOINT,"
+	}
+	if ifi.CanMulticast() {
+		fs += "MULTICAST,"
+	}
+	if len(fs) > 1 {
+		fs = fs[:len(fs)-1]
+	}
+	fs += ">"
+	return fs
+}
+
+func TestInterfaces(t *testing.T) {
+	ift, err := Interfaces()
+	if err != nil {
+		t.Fatalf("Interfaces() failed: %v", err)
+	}
+	t.Logf("table: len/cap = %v/%v\n", len(ift), cap(ift))
+
+	for _, ifi := range ift {
+		ifxi, err := InterfaceByIndex(ifi.Index)
+		if err != nil {
+			t.Fatalf("InterfaceByIndex(%#q) failed: %v", ifi.Index, err)
+		}
+		if !sameInterface(ifxi, &ifi) {
+			t.Fatalf("InterfaceByIndex(%#q) = %v, want %v", ifi.Index, *ifxi, ifi)
+		}
+		ifxn, err := InterfaceByName(ifi.Name)
+		if err != nil {
+			t.Fatalf("InterfaceByName(%#q) failed: %v", ifi.Name, err)
+		}
+		if !sameInterface(ifxn, &ifi) {
+			t.Fatalf("InterfaceByName(%#q) = %v, want %v", ifi.Name, *ifxn, ifi)
+		}
+		ifat, err := ifi.Addrs()
+		if err != nil {
+			t.Fatalf("Interface.Addrs() failed: %v", err)
+		}
+		t.Logf("%s: flags %s, ifindex %v, mtu %v\n", ifi.Name, interfaceFlagsString(&ifi), ifi.Index, ifi.MTU)
+		for _, ifa := range ifat {
+			t.Logf("\tinterface address %s\n", ifa.String())
+		}
+		t.Logf("\thardware address %v", ifi.HardwareAddr.String())
+	}
+}
+
+func TestInterfaceAddrs(t *testing.T) {
+	ifat, err := InterfaceAddrs()
+	if err != nil {
+		t.Fatalf("InterfaceAddrs() failed: %v", err)
+	}
+	t.Logf("table: len/cap = %v/%v\n", len(ifat), cap(ifat))
+
+	for _, ifa := range ifat {
+		t.Logf("interface address %s\n", ifa.String())
+	}
+}