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moby--moby/netlink/netlink.go
Alexander Larsson bf61d41d6c Add netlink submodule
This contains various operations that can replace the use of
shelling out to "ip".
2013-10-25 15:13:24 -07:00

548 lines
11 KiB
Go

package netlink
import (
"encoding/binary"
"fmt"
"net"
"syscall"
"unsafe"
)
var nextSeqNr int
func nativeEndian() binary.ByteOrder {
var x uint32 = 0x01020304
if *(*byte)(unsafe.Pointer(&x)) == 0x01 {
return binary.BigEndian
}
return binary.LittleEndian
}
func getSeq() int {
nextSeqNr = nextSeqNr + 1
return nextSeqNr
}
func getIpFamily(ip net.IP) int {
if len(ip) <= net.IPv4len {
return syscall.AF_INET
}
if ip.To4() != nil {
return syscall.AF_INET
}
return syscall.AF_INET6
}
type NetlinkRequestData interface {
ToWireFormat() []byte
}
type IfInfomsg struct {
syscall.IfInfomsg
}
func newIfInfomsg(family int) *IfInfomsg {
msg := &IfInfomsg{}
msg.Family = uint8(family)
msg.Type = uint16(0)
msg.Index = int32(0)
msg.Flags = uint32(0)
msg.Change = uint32(0)
return msg
}
func (msg *IfInfomsg) ToWireFormat() []byte {
native := nativeEndian()
len := syscall.SizeofIfInfomsg
b := make([]byte, len)
b[0] = msg.Family
b[1] = 0
native.PutUint16(b[2:4], msg.Type)
native.PutUint32(b[4:8], uint32(msg.Index))
native.PutUint32(b[8:12], msg.Flags)
native.PutUint32(b[12:16], msg.Change)
return b
}
type IfAddrmsg struct {
syscall.IfAddrmsg
}
func newIfAddrmsg(family int) *IfAddrmsg {
msg := &IfAddrmsg{}
msg.Family = uint8(family)
msg.Prefixlen = uint8(0)
msg.Flags = uint8(0)
msg.Scope = uint8(0)
msg.Index = uint32(0)
return msg
}
func (msg *IfAddrmsg) ToWireFormat() []byte {
native := nativeEndian()
len := syscall.SizeofIfAddrmsg
b := make([]byte, len)
b[0] = msg.Family
b[1] = msg.Prefixlen
b[2] = msg.Flags
b[3] = msg.Scope
native.PutUint32(b[4:8], msg.Index)
return b
}
type RtMsg struct {
syscall.RtMsg
}
func newRtMsg(family int) *RtMsg {
msg := &RtMsg{}
msg.Family = uint8(family)
msg.Table = syscall.RT_TABLE_MAIN
msg.Scope = syscall.RT_SCOPE_UNIVERSE
msg.Protocol = syscall.RTPROT_BOOT
msg.Type = syscall.RTN_UNICAST
return msg
}
func (msg *RtMsg) ToWireFormat() []byte {
native := nativeEndian()
len := syscall.SizeofRtMsg
b := make([]byte, len)
b[0] = msg.Family
b[1] = msg.Dst_len
b[2] = msg.Src_len
b[3] = msg.Tos
b[4] = msg.Table
b[5] = msg.Protocol
b[6] = msg.Scope
b[7] = msg.Type
native.PutUint32(b[8:12], msg.Flags)
return b
}
func rtaAlignOf(attrlen int) int {
return (attrlen + syscall.RTA_ALIGNTO - 1) & ^(syscall.RTA_ALIGNTO - 1)
}
type RtAttr struct {
syscall.RtAttr
Data []byte
}
func newRtAttr(attrType int, data []byte) *RtAttr {
attr := &RtAttr{}
attr.Type = uint16(attrType)
attr.Data = data
return attr
}
func (attr *RtAttr) ToWireFormat() []byte {
native := nativeEndian()
len := syscall.SizeofRtAttr + len(attr.Data)
b := make([]byte, rtaAlignOf(len))
native.PutUint16(b[0:2], uint16(len))
native.PutUint16(b[2:4], attr.Type)
for i, d := range attr.Data {
b[4+i] = d
}
return b
}
type NetlinkRequest struct {
syscall.NlMsghdr
Data []NetlinkRequestData
}
func (rr *NetlinkRequest) ToWireFormat() []byte {
native := nativeEndian()
length := rr.Len
dataBytes := make([][]byte, len(rr.Data))
for i, data := range rr.Data {
dataBytes[i] = data.ToWireFormat()
length = length + uint32(len(dataBytes[i]))
}
b := make([]byte, length)
native.PutUint32(b[0:4], length)
native.PutUint16(b[4:6], rr.Type)
native.PutUint16(b[6:8], rr.Flags)
native.PutUint32(b[8:12], rr.Seq)
native.PutUint32(b[12:16], rr.Pid)
i := 16
for _, data := range dataBytes {
for _, dataByte := range data {
b[i] = dataByte
i = i + 1
}
}
return b
}
func (rr *NetlinkRequest) AddData(data NetlinkRequestData) {
rr.Data = append(rr.Data, data)
}
func newNetlinkRequest(proto, flags int) *NetlinkRequest {
rr := &NetlinkRequest{}
rr.Len = uint32(syscall.NLMSG_HDRLEN)
rr.Type = uint16(proto)
rr.Flags = syscall.NLM_F_REQUEST | uint16(flags)
rr.Seq = uint32(getSeq())
return rr
}
type NetlinkSocket struct {
fd int
lsa syscall.SockaddrNetlink
}
func getNetlinkSocket() (*NetlinkSocket, error) {
fd, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_RAW, syscall.NETLINK_ROUTE)
if err != nil {
return nil, err
}
s := &NetlinkSocket{
fd: fd,
}
s.lsa.Family = syscall.AF_NETLINK
if err := syscall.Bind(fd, &s.lsa); err != nil {
syscall.Close(fd)
return nil, err
}
return s, nil
}
func (s *NetlinkSocket) Close() {
syscall.Close(s.fd)
}
func (s *NetlinkSocket) Send(request *NetlinkRequest) error {
if err := syscall.Sendto(s.fd, request.ToWireFormat(), 0, &s.lsa); err != nil {
return err
}
return nil
}
func (s *NetlinkSocket) Recieve() ([]syscall.NetlinkMessage, error) {
rb := make([]byte, syscall.Getpagesize())
nr, _, err := syscall.Recvfrom(s.fd, rb, 0)
if err != nil {
return nil, err
}
if nr < syscall.NLMSG_HDRLEN {
return nil, fmt.Errorf("Got short response from netlink")
}
rb = rb[:nr]
return syscall.ParseNetlinkMessage(rb)
}
func (s *NetlinkSocket) GetPid() (uint32, error) {
lsa, err := syscall.Getsockname(s.fd)
if err != nil {
return 0, err
}
switch v := lsa.(type) {
case *syscall.SockaddrNetlink:
return v.Pid, nil
}
return 0, fmt.Errorf("Wrong socket type")
}
func (s *NetlinkSocket) HandleAck(seq uint32) error {
native := nativeEndian()
pid, err := s.GetPid()
if err != nil {
return err
}
done:
for {
msgs, err := s.Recieve()
if err != nil {
return err
}
for _, m := range msgs {
if m.Header.Seq != seq {
return fmt.Errorf("Wrong Seq nr %d, expected %d", m.Header.Seq, seq)
}
if m.Header.Pid != pid {
return fmt.Errorf("Wrong pid %d, expected %d", m.Header.Pid, pid)
}
if m.Header.Type == syscall.NLMSG_DONE {
break done
}
if m.Header.Type == syscall.NLMSG_ERROR {
error := int32(native.Uint32(m.Data[0:4]))
if error == 0 {
break done
}
return syscall.Errno(-error)
}
}
}
return nil
}
// Add a new default gateway. Identical to:
// ip route add default via $ip
func AddDefaultGw(ip net.IP) error {
s, err := getNetlinkSocket()
if err != nil {
return err
}
defer s.Close()
family := getIpFamily(ip)
wb := newNetlinkRequest(syscall.RTM_NEWROUTE, syscall.NLM_F_CREATE|syscall.NLM_F_EXCL|syscall.NLM_F_ACK)
msg := newRtMsg(family)
wb.AddData(msg)
var ipData []byte
if family == syscall.AF_INET {
ipData = ip.To4()
} else {
ipData = ip.To16()
}
gateway := newRtAttr(syscall.RTA_GATEWAY, ipData)
wb.AddData(gateway)
if err := s.Send(wb); err != nil {
return err
}
return s.HandleAck(wb.Seq)
}
// Bring up a particular network interface
func NetworkLinkUp(iface *net.Interface) error {
s, err := getNetlinkSocket()
if err != nil {
return err
}
defer s.Close()
wb := newNetlinkRequest(syscall.RTM_NEWLINK, syscall.NLM_F_ACK)
msg := newIfInfomsg(syscall.AF_UNSPEC)
msg.Change = syscall.IFF_UP
msg.Flags = syscall.IFF_UP
msg.Index = int32(iface.Index)
wb.AddData(msg)
if err := s.Send(wb); err != nil {
return err
}
return s.HandleAck(wb.Seq)
}
// Add an Ip address to an interface. This is identical to:
// ip addr add $ip/$ipNet dev $iface
func NetworkLinkAddIp(iface *net.Interface, ip net.IP, ipNet *net.IPNet) error {
s, err := getNetlinkSocket()
if err != nil {
return err
}
defer s.Close()
family := getIpFamily(ip)
wb := newNetlinkRequest(syscall.RTM_NEWADDR, syscall.NLM_F_CREATE|syscall.NLM_F_EXCL|syscall.NLM_F_ACK)
msg := newIfAddrmsg(family)
msg.Index = uint32(iface.Index)
prefixLen, _ := ipNet.Mask.Size()
msg.Prefixlen = uint8(prefixLen)
wb.AddData(msg)
var ipData []byte
if family == syscall.AF_INET {
ipData = ip.To4()
} else {
ipData = ip.To16()
}
localData := newRtAttr(syscall.IFA_LOCAL, ipData)
wb.AddData(localData)
addrData := newRtAttr(syscall.IFA_ADDRESS, ipData)
wb.AddData(addrData)
if err := s.Send(wb); err != nil {
return err
}
return s.HandleAck(wb.Seq)
}
func zeroTerminated(s string) []byte {
bytes := make([]byte, len(s)+1)
for i := 0; i < len(s); i++ {
bytes[i] = s[i]
}
bytes[len(s)] = 0
return bytes
}
func nonZeroTerminated(s string) []byte {
bytes := make([]byte, len(s))
for i := 0; i < len(s); i++ {
bytes[i] = s[i]
}
return bytes
}
// Add a new network link of a specified type. This is identical to
// running: ip add link $name type $linkType
func NetworkLinkAdd(name string, linkType string) error {
s, err := getNetlinkSocket()
if err != nil {
return err
}
defer s.Close()
wb := newNetlinkRequest(syscall.RTM_NEWLINK, syscall.NLM_F_CREATE|syscall.NLM_F_EXCL|syscall.NLM_F_ACK)
msg := newIfInfomsg(syscall.AF_UNSPEC)
wb.AddData(msg)
nameData := newRtAttr(syscall.IFLA_IFNAME, zeroTerminated(name))
wb.AddData(nameData)
IFLA_INFO_KIND := 1
kindData := newRtAttr(IFLA_INFO_KIND, nonZeroTerminated(linkType))
infoData := newRtAttr(syscall.IFLA_LINKINFO, kindData.ToWireFormat())
wb.AddData(infoData)
if err := s.Send(wb); err != nil {
return err
}
return s.HandleAck(wb.Seq)
}
// Returns an array of IPNet for all the currently routed subnets on ipv4
// This is similar to the first column of "ip route" output
func NetworkGetRoutes() ([]*net.IPNet, error) {
native := nativeEndian()
s, err := getNetlinkSocket()
if err != nil {
return nil, err
}
defer s.Close()
wb := newNetlinkRequest(syscall.RTM_GETROUTE, syscall.NLM_F_DUMP)
msg := newIfInfomsg(syscall.AF_UNSPEC)
wb.AddData(msg)
if err := s.Send(wb); err != nil {
return nil, err
}
pid, err := s.GetPid()
if err != nil {
return nil, err
}
res := make([]*net.IPNet, 0)
done:
for {
msgs, err := s.Recieve()
if err != nil {
return nil, err
}
for _, m := range msgs {
if m.Header.Seq != wb.Seq {
return nil, fmt.Errorf("Wrong Seq nr %d, expected 1", m.Header.Seq)
}
if m.Header.Pid != pid {
return nil, fmt.Errorf("Wrong pid %d, expected %d", m.Header.Pid, pid)
}
if m.Header.Type == syscall.NLMSG_DONE {
break done
}
if m.Header.Type == syscall.NLMSG_ERROR {
error := int32(native.Uint32(m.Data[0:4]))
if error == 0 {
break done
}
return nil, syscall.Errno(-error)
}
if m.Header.Type != syscall.RTM_NEWROUTE {
continue
}
var iface *net.Interface = nil
var ipNet *net.IPNet = nil
msg := (*RtMsg)(unsafe.Pointer(&m.Data[0:syscall.SizeofRtMsg][0]))
if msg.Flags&syscall.RTM_F_CLONED != 0 {
// Ignore cloned routes
continue
}
if msg.Table != syscall.RT_TABLE_MAIN {
// Ignore non-main tables
continue
}
if msg.Family != syscall.AF_INET {
// Ignore non-ipv4 routes
continue
}
if msg.Dst_len == 0 {
// Ignore default routes
continue
}
attrs, err := syscall.ParseNetlinkRouteAttr(&m)
if err != nil {
return nil, err
}
for _, attr := range attrs {
switch attr.Attr.Type {
case syscall.RTA_DST:
ip := attr.Value
ipNet = &net.IPNet{
IP: ip,
Mask: net.CIDRMask(int(msg.Dst_len), 8*len(ip)),
}
case syscall.RTA_OIF:
index := int(native.Uint32(attr.Value[0:4]))
iface, _ = net.InterfaceByIndex(index)
_ = iface
}
}
if ipNet != nil {
res = append(res, ipNet)
}
}
}
return res, nil
}