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ipaux_linux.go
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ipaux_linux.go
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// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build linux
package osnetconfig
// We connect to the Netlink Route socket and parse messages to
// look for network configuration changes. This is very Linux
// specific, hence the file name.
import (
"errors"
"fmt"
"net"
"syscall"
"unsafe"
"v.io/x/lib/netconfig/route"
"v.io/x/lib/vlog"
)
/*
#include <linux/rtnetlink.h>
*/
import "C"
// All rtnetlink attributes start with this header.
type rtAttrHdr C.struct_rtattr
const rtAttrHdrLen = C.sizeof_struct_rtattr
// The address change messages (RTM_NEWADDR, RTM_DELADDR, RTM_GETADDR).
type ifaddrMsgHdr C.struct_ifaddrmsg
const ifaddrMsgHdrLen = C.sizeof_struct_ifaddrmsg
type rtAttribute fmt.Stringer
type rtAddressMessage struct {
name string
hdr ifaddrMsgHdr
attributes []rtAttribute
}
// Attribute types (see rtnetlink(7))
type ifaAddress net.IP
type ifaLocal net.IP
type ifaBroadcast net.IP
type ifaAnycast net.IP
type ifaMulticast net.IP
type ifaLabel string
type ifaCacheInfo C.struct_ifa_cacheinfo
const ifaCacheInfoLen = C.sizeof_struct_ifa_cacheinfo
// String routines to make debugging easier.
func (a ifaAddress) String() string { return "Address=" + net.IP(a).String() }
func (a ifaLocal) String() string { return "Local=" + net.IP(a).String() }
func (a ifaBroadcast) String() string { return "Braodcast=" + net.IP(a).String() }
func (a ifaAnycast) String() string { return "Anycast=" + net.IP(a).String() }
func (a ifaMulticast) String() string { return "Anycast=" + net.IP(a).String() }
func (a ifaLabel) String() string { return "Label=" + string(a) }
func (a ifaCacheInfo) String() string {
return fmt.Sprintf("CacheInfo[preferred %d valid %d cstamp %d tstamp %d]", a.ifa_prefered, a.ifa_valid, a.cstamp, a.tstamp)
}
func (m *rtAddressMessage) String() string {
return fmt.Sprintf("%s: index %d %v", m.name, m.hdr.ifa_index, m.attributes)
}
// Address looks for the address attribute in an rtAddressMessage. If it isn't there, just assume the null address.
func (m *rtAddressMessage) Address() net.IP {
for _, a := range m.attributes {
switch a.(type) {
case ifaAddress:
return net.IP(a.(ifaAddress))
}
}
return net.IPv4zero
}
func parsertAddressAttribute(b []byte) (rtAttribute, []byte, error) {
if len(b) == 0 {
return nil, nil, nil
}
if len(b) < rtAttrHdrLen {
return nil, nil, errors.New("attribute too short")
}
ahdr := (*rtAttrHdr)(unsafe.Pointer(&b[0]))
rounded := ((ahdr.rta_len + 3) / 4) * 4
if len(b) < int(rounded) {
return nil, nil, errors.New("attribute too short")
}
remaining := b[rounded:]
b = b[rtAttrHdrLen:ahdr.rta_len]
switch ahdr.rta_type {
case C.IFA_ADDRESS:
return rtAttribute(ifaAddress(net.IP(b))), remaining, nil
case C.IFA_LOCAL:
return rtAttribute(ifaLocal(b)), remaining, nil
case C.IFA_LABEL:
return rtAttribute(ifaLabel(b)), remaining, nil
case C.IFA_BROADCAST:
return rtAttribute(ifaBroadcast(b)), remaining, nil
case C.IFA_ANYCAST:
return rtAttribute(ifaAnycast(b)), remaining, nil
case C.IFA_CACHEINFO:
if len(b) < ifaCacheInfoLen {
return nil, nil, errors.New("attribute too short")
}
return rtAttribute(ifaCacheInfo(*(*C.struct_ifa_cacheinfo)(unsafe.Pointer(&b[0])))), remaining, nil
case C.IFA_MULTICAST:
return rtAttribute(ifaMulticast(b)), remaining, nil
}
return nil, remaining, errors.New("unknown attribute")
}
func parsertAddressMessage(nlm syscall.NetlinkMessage) (*rtAddressMessage, error) {
var name string
switch nlm.Header.Type {
case C.RTM_NEWADDR:
name = "RTM_NEWADDR"
case C.RTM_DELADDR:
name = "RTM_DELADDR"
case C.RTM_GETADDR:
name = "RTM_GETADDR"
default:
return nil, fmt.Errorf("unknown message type")
}
if len(nlm.Data) < ifaddrMsgHdrLen {
return nil, errors.New("bad length")
}
m := &rtAddressMessage{name: name, hdr: *(*ifaddrMsgHdr)(unsafe.Pointer(&nlm.Data[0]))}
b := nlm.Data[ifaddrMsgHdrLen:]
for {
var a rtAttribute
var err error
a, b, err = parsertAddressAttribute(b)
if b == nil {
break
}
if err == nil {
m.attributes = append(m.attributes, a)
}
}
return m, nil
}
// The link change messages (RTM_NEWLINK, RTM_DELLINK, RTM_GETLINK).
type ifInfoMsgHdr C.struct_ifinfomsg
const ifInfoMsgHdrLen = C.sizeof_struct_ifinfomsg
type rtLinkMessage struct {
name string
hdr ifInfoMsgHdr
attributes []rtAttribute
}
// Attribute types (see rtnetlink(7))
type iflaAddress []byte
type iflaBroadcast []byte
type iflaIFName string
type iflaMTU uint32
type iflaLink int
type iflaQDisc string
type iflaOperstate int
type iflaStats C.struct_rtnl_link_stats
const iflaStatsLen = C.sizeof_struct_rtnl_link_stats
// String routines to make debugging easier.
func (a iflaAddress) String() string { return fmt.Sprintf("HWAddress=%v", []byte(a)) }
func (a iflaBroadcast) String() string { return fmt.Sprintf("HWBroadcast=%v", []byte(a)) }
func (a iflaIFName) String() string { return "Name=" + string(a) }
func (a iflaMTU) String() string { return fmt.Sprintf("MTU=%d", uint32(a)) }
func (a iflaLink) String() string { return fmt.Sprintf("Type=%d", int(a)) }
func (a iflaQDisc) String() string { return "Qdisc=" + string(a) }
func (a iflaStats) String() string {
return fmt.Sprintf("Stats[rx %d tx %d ...]", a.rx_packets, a.tx_packets)
}
func (a iflaOperstate) String() string { return fmt.Sprintf("Operstate=%d", int(a)) }
func (m *rtLinkMessage) String() string {
return fmt.Sprintf("%s: index %d %v", m.name, m.hdr.ifi_index, m.attributes)
}
func parseRTLinkAttribute(b []byte) (rtAttribute, []byte, error) {
if len(b) == 0 {
return nil, nil, nil
}
if len(b) < rtAttrHdrLen {
return nil, nil, errors.New("attribute too short")
}
ahdr := (*rtAttrHdr)(unsafe.Pointer(&b[0]))
rounded := ((ahdr.rta_len + 3) / 4) * 4
if len(b) < int(rounded) {
return nil, nil, errors.New("attribute too short")
}
remaining := b[rounded:]
b = b[rtAttrHdrLen:ahdr.rta_len]
switch ahdr.rta_type {
case C.IFLA_ADDRESS:
return rtAttribute(iflaAddress(b)), remaining, nil
case C.IFLA_BROADCAST:
return rtAttribute(iflaBroadcast(b)), remaining, nil
case C.IFLA_IFNAME:
return rtAttribute(iflaIFName(string(b))), remaining, nil
case C.IFLA_MTU:
return rtAttribute(iflaMTU(*(*C.uint)(unsafe.Pointer(&b[0])))), remaining, nil
case C.IFLA_LINK:
return rtAttribute(iflaMTU(*(*C.int)(unsafe.Pointer(&b[0])))), remaining, nil
case C.IFLA_QDISC:
return rtAttribute(iflaQDisc(string(b))), remaining, nil
case C.IFLA_STATS:
if len(b) < iflaStatsLen {
return nil, remaining, errors.New("attribute too short")
}
return rtAttribute(iflaStats(*(*C.struct_rtnl_link_stats)(unsafe.Pointer(&b[0])))), remaining, nil
case C.IFLA_OPERSTATE:
return rtAttribute(iflaOperstate(*(*C.int)(unsafe.Pointer(&b[0])))), remaining, nil
}
return nil, remaining, errors.New("unknown attribute")
}
func parsertLinkMessage(nlm syscall.NetlinkMessage) (*rtLinkMessage, error) {
var name string
switch nlm.Header.Type {
case C.RTM_NEWLINK:
name = "RTM_NEWLINK"
case C.RTM_DELLINK:
name = "RTM_DELLINK"
case C.RTM_GETLINK:
name = "RTM_GETLINK"
default:
return nil, fmt.Errorf("unknown message type")
}
if len(nlm.Data) < ifInfoMsgHdrLen {
return nil, errors.New("bad length")
}
m := &rtLinkMessage{name: name, hdr: *(*ifInfoMsgHdr)(unsafe.Pointer(&nlm.Data[0]))}
b := nlm.Data[ifInfoMsgHdrLen:]
for {
var a rtAttribute
var err error
a, b, err = parseRTLinkAttribute(b)
if b == nil {
break
}
if err == nil {
m.attributes = append(m.attributes, a)
}
}
return m, nil
}
const (
GROUPS = C.RTMGRP_LINK | C.RTMGRP_IPV4_IFADDR | C.RTMGRP_IPV4_MROUTE | C.RTMGRP_IPV4_ROUTE | C.RTMGRP_IPV6_IFADDR | C.RTMGRP_IPV6_MROUTE | C.RTMGRP_IPV6_ROUTE | C.RTMGRP_NOTIFY
)
func (n *Notifier) initLocked() error {
s, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_RAW, syscall.NETLINK_ROUTE)
if err != nil {
return fmt.Errorf("socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE) failed: %v", err)
}
lsa := &syscall.SockaddrNetlink{Family: syscall.AF_NETLINK, Groups: GROUPS}
if err := syscall.Bind(s, lsa); err != nil {
syscall.Close(s)
return fmt.Errorf("bind(%d, {AF_NETLINK, 0x%x}) failed: %v", s, lsa.Groups, err)
}
go watcher(n, s)
return nil
}
func watcher(n *Notifier, sock int) {
defer syscall.Close(sock)
var newAddrs []net.IP
buf := make([]byte, 4096)
for {
nr, _, err := syscall.Recvfrom(sock, buf, 0)
if err != nil {
vlog.Infof("recvfrom(%d) on an AF_NETLINK socket failed: %v", sock, err)
return
}
msgs, err := syscall.ParseNetlinkMessage(buf[:nr])
if err != nil {
vlog.Infof("ParseNetlinkMessage failed: %s", err)
continue
}
L:
for _, m := range msgs {
if am, err := parsertAddressMessage(m); err == nil {
// NOTE(p): We get continuous NEWADDR messages about some
// IPv6 addresses in Google corp. Just ignore duplicate back
// to back NEWADDRs about the same addresses.
if am.name == "RTM_NEWADDR" {
addr := am.Address()
for _, a := range newAddrs {
if addr.Equal(a) {
break L
}
}
newAddrs = append(newAddrs, addr)
} else {
newAddrs = nil
}
} else if _, err := parsertLinkMessage(m); err == nil {
newAddrs = nil
} else {
continue
}
if n.ding() {
return
}
}
}
}
func toIP(a []byte) (net.IP, error) {
switch len(a) {
case 4:
return net.IPv4(a[0], a[1], a[2], a[3]), nil
case 16:
return net.IP(a), nil
}
return net.IPv6unspecified, errors.New("unknown ip address len")
}
func (n *Notifier) shutdown() {}
// GetIPRoutes implements netconfig.Notifier.
func (n *Notifier) GetIPRoutes(defaultOnly bool) []route.IPRoute {
var iproutes []route.IPRoute
rib, err := syscall.NetlinkRIB(syscall.RTM_GETROUTE, syscall.AF_UNSPEC)
if err != nil {
vlog.Infof("Couldn't read: %s", err)
return iproutes
}
msgs, err := syscall.ParseNetlinkMessage(rib)
if err != nil {
vlog.Infof("Couldn't parse: %s", err)
return iproutes
}
L:
for _, m := range msgs {
if m.Header.Type != syscall.RTM_NEWROUTE {
continue
}
attrs, err := syscall.ParseNetlinkRouteAttr(&m)
if err != nil {
continue
}
r := route.IPRoute{}
for _, a := range attrs {
switch a.Attr.Type {
case syscall.RTA_DST:
if r.Net.IP, err = toIP(a.Value[:]); err != nil {
continue L
}
case syscall.RTA_GATEWAY:
if r.Gateway, err = toIP(a.Value[:]); err != nil {
continue L
}
case syscall.RTA_OIF:
r.IfcIndex = int(a.Value[0])
case syscall.RTA_PREFSRC:
if r.PreferredSource, err = toIP(a.Value[:]); err != nil {
continue L
}
}
}
// There is no RTA_DST attribute if destination is a default gateway.
// Set the destination IP with zero IP, if not set yet.
if r.Net.IP == nil {
if r.Gateway == nil {
continue
}
if r.Gateway.To4() != nil {
r.Net.IP = net.IPv4zero
} else {
r.Net.IP = net.IPv6zero
}
}
addrLen := 128
if r.Net.IP.To4() != nil {
addrLen = 32
}
b := m.Data[:syscall.SizeofRtMsg]
a := (*syscall.RtMsg)(unsafe.Pointer(&b[0]))
if int(a.Dst_len) > addrLen {
continue
}
r.Net.Mask = net.CIDRMask(int(a.Dst_len), addrLen)
if !defaultOnly || route.IsDefaultIPRoute(&r) {
iproutes = append(iproutes, r)
}
}
return iproutes
}