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// 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.
// Netlink sockets and messages
package syscall
import (
"sync"
"unsafe"
)
// Round the length of a netlink message up to align it properly.
func nlmAlignOf(msglen int) int {
return (msglen + NLMSG_ALIGNTO - 1) & ^(NLMSG_ALIGNTO - 1)
}
// Round the length of a netlink route attribute up to align it
// properly.
func rtaAlignOf(attrlen int) int {
return (attrlen + RTA_ALIGNTO - 1) & ^(RTA_ALIGNTO - 1)
}
// NetlinkRouteRequest represents a request message to receive routing
// and link states from the kernel.
type NetlinkRouteRequest struct {
Header NlMsghdr
Data RtGenmsg
}
func (rr *NetlinkRouteRequest) toWireFormat() []byte {
b := make([]byte, rr.Header.Len)
*(*uint32)(unsafe.Pointer(&b[0:4][0])) = rr.Header.Len
*(*uint16)(unsafe.Pointer(&b[4:6][0])) = rr.Header.Type
*(*uint16)(unsafe.Pointer(&b[6:8][0])) = rr.Header.Flags
*(*uint32)(unsafe.Pointer(&b[8:12][0])) = rr.Header.Seq
*(*uint32)(unsafe.Pointer(&b[12:16][0])) = rr.Header.Pid
b[16] = byte(rr.Data.Family)
return b
}
func newNetlinkRouteRequest(proto, seq, family int) []byte {
rr := &NetlinkRouteRequest{}
rr.Header.Len = uint32(NLMSG_HDRLEN + SizeofRtGenmsg)
rr.Header.Type = uint16(proto)
rr.Header.Flags = NLM_F_DUMP | NLM_F_REQUEST
rr.Header.Seq = uint32(seq)
rr.Data.Family = uint8(family)
return rr.toWireFormat()
}
var pageBufPool = &sync.Pool{New: func() any {
b := make([]byte, Getpagesize())
return &b
}}
// NetlinkRIB returns routing information base, as known as RIB, which
// consists of network facility information, states and parameters.
func NetlinkRIB(proto, family int) ([]byte, error) {
s, err := Socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE)
if err != nil {
return nil, err
}
defer Close(s)
sa := &SockaddrNetlink{Family: AF_NETLINK}
if err := Bind(s, sa); err != nil {
return nil, err
}
wb := newNetlinkRouteRequest(proto, 1, family)
if err := Sendto(s, wb, 0, sa); err != nil {
return nil, err
}
lsa, err := Getsockname(s)
if err != nil {
return nil, err
}
lsanl, ok := lsa.(*SockaddrNetlink)
if !ok {
return nil, EINVAL
}
var tab []byte
rbNew := pageBufPool.Get().(*[]byte)
defer pageBufPool.Put(rbNew)
done:
for {
rb := *rbNew
nr, _, err := Recvfrom(s, rb, 0)
if err != nil {
return nil, err
}
if nr < NLMSG_HDRLEN {
return nil, EINVAL
}
rb = rb[:nr]
tab = append(tab, rb...)
msgs, err := ParseNetlinkMessage(rb)
if err != nil {
return nil, err
}
for _, m := range msgs {
if m.Header.Seq != 1 || m.Header.Pid != lsanl.Pid {
return nil, EINVAL
}
if m.Header.Type == NLMSG_DONE {
break done
}
if m.Header.Type == NLMSG_ERROR {
return nil, EINVAL
}
}
}
return tab, nil
}
// NetlinkMessage represents a netlink message.
type NetlinkMessage struct {
Header NlMsghdr
Data []byte
}
// ParseNetlinkMessage parses b as an array of netlink messages and
// returns the slice containing the NetlinkMessage structures.
func ParseNetlinkMessage(b []byte) ([]NetlinkMessage, error) {
var msgs []NetlinkMessage
for len(b) >= NLMSG_HDRLEN {
h, dbuf, dlen, err := netlinkMessageHeaderAndData(b)
if err != nil {
return nil, err
}
m := NetlinkMessage{Header: *h, Data: dbuf[:int(h.Len)-NLMSG_HDRLEN]}
msgs = append(msgs, m)
b = b[dlen:]
}
return msgs, nil
}
func netlinkMessageHeaderAndData(b []byte) (*NlMsghdr, []byte, int, error) {
h := (*NlMsghdr)(unsafe.Pointer(&b[0]))
l := nlmAlignOf(int(h.Len))
if int(h.Len) < NLMSG_HDRLEN || l > len(b) {
return nil, nil, 0, EINVAL
}
return h, b[NLMSG_HDRLEN:], l, nil
}
// NetlinkRouteAttr represents a netlink route attribute.
type NetlinkRouteAttr struct {
Attr RtAttr
Value []byte
}
// ParseNetlinkRouteAttr parses m's payload as an array of netlink
// route attributes and returns the slice containing the
// NetlinkRouteAttr structures.
func ParseNetlinkRouteAttr(m *NetlinkMessage) ([]NetlinkRouteAttr, error) {
var b []byte
switch m.Header.Type {
case RTM_NEWLINK, RTM_DELLINK:
b = m.Data[SizeofIfInfomsg:]
case RTM_NEWADDR, RTM_DELADDR:
b = m.Data[SizeofIfAddrmsg:]
case RTM_NEWROUTE, RTM_DELROUTE:
b = m.Data[SizeofRtMsg:]
default:
return nil, EINVAL
}
var attrs []NetlinkRouteAttr
for len(b) >= SizeofRtAttr {
a, vbuf, alen, err := netlinkRouteAttrAndValue(b)
if err != nil {
return nil, err
}
ra := NetlinkRouteAttr{Attr: *a, Value: vbuf[:int(a.Len)-SizeofRtAttr]}
attrs = append(attrs, ra)
b = b[alen:]
}
return attrs, nil
}
func netlinkRouteAttrAndValue(b []byte) (*RtAttr, []byte, int, error) {
a := (*RtAttr)(unsafe.Pointer(&b[0]))
if int(a.Len) < SizeofRtAttr || int(a.Len) > len(b) {
return nil, nil, 0, EINVAL
}
return a, b[SizeofRtAttr:], rtaAlignOf(int(a.Len)), nil
}
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