libgo/syscalls/netlink_linux.go

   1 // Copyright 2011 The Go Authors.  All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Netlink sockets and messages
   6
   7 package syscall
   8
   9 import (
  10         "unsafe"
  11 )
  12
  13 // Round the length of a netlink message up to align it properly.
  14 func nlmAlignOf(msglen int) int {
  15         return (msglen + NLMSG_ALIGNTO - 1) & ^(NLMSG_ALIGNTO - 1)
  16 }
  17
  18 // Round the length of a netlink route attribute up to align it
  19 // properly.
  20 func rtaAlignOf(attrlen int) int {
  21         return (attrlen + RTA_ALIGNTO - 1) & ^(RTA_ALIGNTO - 1)
  22 }
  23
  24 // NetlinkRouteRequest represents the request message to receive
  25 // routing and link states from the kernel.
  26 type NetlinkRouteRequest struct {
  27         Header NlMsghdr
  28         Data   RtGenmsg
  29 }
  30
  31 func (rr *NetlinkRouteRequest) toWireFormat() []byte {
  32         b := make([]byte, rr.Header.Len)
  33         b[0] = byte(rr.Header.Len)
  34         b[1] = byte(rr.Header.Len >> 8)
  35         b[2] = byte(rr.Header.Len >> 16)
  36         b[3] = byte(rr.Header.Len >> 24)
  37         b[4] = byte(rr.Header.Type)
  38         b[5] = byte(rr.Header.Type >> 8)
  39         b[6] = byte(rr.Header.Flags)
  40         b[7] = byte(rr.Header.Flags >> 8)
  41         b[8] = byte(rr.Header.Seq)
  42         b[9] = byte(rr.Header.Seq >> 8)
  43         b[10] = byte(rr.Header.Seq >> 16)
  44         b[11] = byte(rr.Header.Seq >> 24)
  45         b[12] = byte(rr.Header.Pid)
  46         b[13] = byte(rr.Header.Pid >> 8)
  47         b[14] = byte(rr.Header.Pid >> 16)
  48         b[15] = byte(rr.Header.Pid >> 24)
  49         b[16] = byte(rr.Data.Family)
  50         return b
  51 }
  52
  53 func newNetlinkRouteRequest(proto, seq, family int) []byte {
  54         rr := &NetlinkRouteRequest{}
  55         rr.Header.Len = uint32(NLMSG_HDRLEN + SizeofRtGenmsg)
  56         rr.Header.Type = uint16(proto)
  57         rr.Header.Flags = NLM_F_DUMP | NLM_F_REQUEST
  58         rr.Header.Seq = uint32(seq)
  59         rr.Data.Family = uint8(family)
  60         return rr.toWireFormat()
  61 }
  62
  63 // NetlinkRIB returns routing information base, as known as RIB,
  64 // which consists of network facility information, states and
  65 // parameters.
  66 func NetlinkRIB(proto, family int) ([]byte, int) {
  67         var (
  68                 s     int
  69                 e     int
  70                 lsanl SockaddrNetlink
  71                 seq   int
  72                 tab   []byte
  73         )
  74
  75         s, e = Socket(AF_NETLINK, SOCK_RAW, 0)
  76         if e != 0 {
  77                 return nil, e
  78         }
  79         defer Close(s)
  80
  81         lsanl.Family = AF_NETLINK
  82         e = Bind(s, &lsanl)
  83         if e != 0 {
  84                 return nil, e
  85         }
  86
  87         seq++
  88         wb := newNetlinkRouteRequest(proto, seq, family)
  89         e = Sendto(s, wb, 0, &lsanl)
  90         if e != 0 {
  91                 return nil, e
  92         }
  93
  94         for {
  95                 var (
  96                         rb  []byte
  97                         nr  int
  98                         lsa Sockaddr
  99                 )
 100
 101                 rb = make([]byte, Getpagesize())
 102                 nr, _, e = Recvfrom(s, rb, 0)
 103                 if e != 0 {
 104                         return nil, e
 105                 }
 106                 if nr < NLMSG_HDRLEN {
 107                         return nil, EINVAL
 108                 }
 109                 rb = rb[:nr]
 110                 tab = append(tab, rb...)
 111
 112                 msgs, _ := ParseNetlinkMessage(rb)
 113                 for _, m := range msgs {
 114                         if lsa, e = Getsockname(s); e != 0 {
 115                                 return nil, e
 116                         }
 117                         switch v := lsa.(type) {
 118                         case *SockaddrNetlink:
 119                                 if m.Header.Seq != uint32(seq) || m.Header.Pid != v.Pid {
 120                                         return nil, EINVAL
 121                                 }
 122                         default:
 123                                 return nil, EINVAL
 124                         }
 125                         if m.Header.Type == NLMSG_DONE {
 126                                 goto done
 127                         }
 128                         if m.Header.Type == NLMSG_ERROR {
 129                                 return nil, EINVAL
 130                         }
 131                 }
 132         }
 133
 134 done:
 135         return tab, 0
 136 }
 137
 138 // NetlinkMessage represents the netlink message.
 139 type NetlinkMessage struct {
 140         Header NlMsghdr
 141         Data   []byte
 142 }
 143
 144 // ParseNetlinkMessage parses buf as netlink messages and returns
 145 // the slice containing the NetlinkMessage structs.
 146 func ParseNetlinkMessage(buf []byte) ([]NetlinkMessage, int) {
 147         var (
 148                 h    *NlMsghdr
 149                 dbuf []byte
 150                 dlen int
 151                 e    int
 152                 msgs []NetlinkMessage
 153         )
 154
 155         for len(buf) >= NLMSG_HDRLEN {
 156                 h, dbuf, dlen, e = netlinkMessageHeaderAndData(buf)
 157                 if e != 0 {
 158                         break
 159                 }
 160                 m := NetlinkMessage{}
 161                 m.Header = *h
 162                 m.Data = dbuf[:int(h.Len)-NLMSG_HDRLEN]
 163                 msgs = append(msgs, m)
 164                 buf = buf[dlen:]
 165         }
 166
 167         return msgs, e
 168 }
 169
 170 func netlinkMessageHeaderAndData(buf []byte) (*NlMsghdr, []byte, int, int) {
 171         h := (*NlMsghdr)(unsafe.Pointer(&buf[0]))
 172         if int(h.Len) < NLMSG_HDRLEN || int(h.Len) > len(buf) {
 173                 return nil, nil, 0, EINVAL
 174         }
 175         return h, buf[NLMSG_HDRLEN:], nlmAlignOf(int(h.Len)), 0
 176 }
 177
 178 // NetlinkRouteAttr represents the netlink route attribute.
 179 type NetlinkRouteAttr struct {
 180         Attr  RtAttr
 181         Value []byte
 182 }
 183
 184 // ParseNetlinkRouteAttr parses msg's payload as netlink route
 185 // attributes and returns the slice containing the NetlinkRouteAttr
 186 // structs.
 187 func ParseNetlinkRouteAttr(msg *NetlinkMessage) ([]NetlinkRouteAttr, int) {
 188         var (
 189                 buf   []byte
 190                 a     *RtAttr
 191                 alen  int
 192                 vbuf  []byte
 193                 e     int
 194                 attrs []NetlinkRouteAttr
 195         )
 196
 197         switch msg.Header.Type {
 198         case RTM_NEWLINK:
 199                 buf = msg.Data[SizeofIfInfomsg:]
 200         case RTM_NEWADDR:
 201                 buf = msg.Data[SizeofIfAddrmsg:]
 202         default:
 203                 return nil, EINVAL
 204         }
 205
 206         for len(buf) >= SizeofRtAttr {
 207                 a, vbuf, alen, e = netlinkRouteAttrAndValue(buf)
 208                 if e != 0 {
 209                         break
 210                 }
 211                 ra := NetlinkRouteAttr{}
 212                 ra.Attr = *a
 213                 ra.Value = vbuf[:int(a.Len)-SizeofRtAttr]
 214                 attrs = append(attrs, ra)
 215                 buf = buf[alen:]
 216         }
 217
 218         return attrs, 0
 219 }
 220
 221 func netlinkRouteAttrAndValue(buf []byte) (*RtAttr, []byte, int, int) {
 222         h := (*RtAttr)(unsafe.Pointer(&buf[0]))
 223         if int(h.Len) < SizeofRtAttr || int(h.Len) > len(buf) {
 224                 return nil, nil, 0, EINVAL
 225         }
 226         return h, buf[SizeofRtAttr:], rtaAlignOf(int(h.Len)), 0
 227 }