libgo/go/syscall/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 "unsafe"
  10
  11 // Round the length of a netlink message up to align it properly.
  12 func nlmAlignOf(msglen int) int {
  13         return (msglen + NLMSG_ALIGNTO - 1) & ^(NLMSG_ALIGNTO - 1)
  14 }
  15
  16 // Round the length of a netlink route attribute up to align it
  17 // properly.
  18 func rtaAlignOf(attrlen int) int {
  19         return (attrlen + RTA_ALIGNTO - 1) & ^(RTA_ALIGNTO - 1)
  20 }
  21
  22 // NetlinkRouteRequest represents a request message to receive routing
  23 // and link states from the kernel.
  24 type NetlinkRouteRequest struct {
  25         Header NlMsghdr
  26         Data   RtGenmsg
  27 }
  28
  29 func (rr *NetlinkRouteRequest) toWireFormat() []byte {
  30         b := make([]byte, rr.Header.Len)
  31         *(*uint32)(unsafe.Pointer(&b[0:4][0])) = rr.Header.Len
  32         *(*uint16)(unsafe.Pointer(&b[4:6][0])) = rr.Header.Type
  33         *(*uint16)(unsafe.Pointer(&b[6:8][0])) = rr.Header.Flags
  34         *(*uint32)(unsafe.Pointer(&b[8:12][0])) = rr.Header.Seq
  35         *(*uint32)(unsafe.Pointer(&b[12:16][0])) = rr.Header.Pid
  36         b[16] = byte(rr.Data.Family)
  37         return b
  38 }
  39
  40 func newNetlinkRouteRequest(proto, seq, family int) []byte {
  41         rr := &NetlinkRouteRequest{}
  42         rr.Header.Len = uint32(NLMSG_HDRLEN + SizeofRtGenmsg)
  43         rr.Header.Type = uint16(proto)
  44         rr.Header.Flags = NLM_F_DUMP | NLM_F_REQUEST
  45         rr.Header.Seq = uint32(seq)
  46         rr.Data.Family = uint8(family)
  47         return rr.toWireFormat()
  48 }
  49
  50 // NetlinkRIB returns routing information base, as known as RIB, which
  51 // consists of network facility information, states and parameters.
  52 func NetlinkRIB(proto, family int) ([]byte, error) {
  53         s, err := Socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)
  54         if err != nil {
  55                 return nil, err
  56         }
  57         defer Close(s)
  58         lsa := &SockaddrNetlink{Family: AF_NETLINK}
  59         if err := Bind(s, lsa); err != nil {
  60                 return nil, err
  61         }
  62         wb := newNetlinkRouteRequest(proto, 1, family)
  63         if err := Sendto(s, wb, 0, lsa); err != nil {
  64                 return nil, err
  65         }
  66         var tab []byte
  67         rbNew := make([]byte, Getpagesize())
  68 done:
  69         for {
  70                 rb := rbNew
  71                 nr, _, err := Recvfrom(s, rb, 0)
  72                 if err != nil {
  73                         return nil, err
  74                 }
  75                 if nr < NLMSG_HDRLEN {
  76                         return nil, EINVAL
  77                 }
  78                 rb = rb[:nr]
  79                 tab = append(tab, rb...)
  80                 msgs, err := ParseNetlinkMessage(rb)
  81                 if err != nil {
  82                         return nil, err
  83                 }
  84                 for _, m := range msgs {
  85                         lsa, err := Getsockname(s)
  86                         if err != nil {
  87                                 return nil, err
  88                         }
  89                         switch v := lsa.(type) {
  90                         case *SockaddrNetlink:
  91                                 if m.Header.Seq != 1 || m.Header.Pid != v.Pid {
  92                                         return nil, EINVAL
  93                                 }
  94                         default:
  95                                 return nil, EINVAL
  96                         }
  97                         if m.Header.Type == NLMSG_DONE {
  98                                 break done
  99                         }
 100                         if m.Header.Type == NLMSG_ERROR {
 101                                 return nil, EINVAL
 102                         }
 103                 }
 104         }
 105         return tab, nil
 106 }
 107
 108 // NetlinkMessage represents a netlink message.
 109 type NetlinkMessage struct {
 110         Header NlMsghdr
 111         Data   []byte
 112 }
 113
 114 // ParseNetlinkMessage parses b as an array of netlink messages and
 115 // returns the slice containing the NetlinkMessage structures.
 116 func ParseNetlinkMessage(b []byte) ([]NetlinkMessage, error) {
 117         var msgs []NetlinkMessage
 118         for len(b) >= NLMSG_HDRLEN {
 119                 h, dbuf, dlen, err := netlinkMessageHeaderAndData(b)
 120                 if err != nil {
 121                         return nil, err
 122                 }
 123                 m := NetlinkMessage{Header: *h, Data: dbuf[:int(h.Len)-NLMSG_HDRLEN]}
 124                 msgs = append(msgs, m)
 125                 b = b[dlen:]
 126         }
 127         return msgs, nil
 128 }
 129
 130 func netlinkMessageHeaderAndData(b []byte) (*NlMsghdr, []byte, int, error) {
 131         h := (*NlMsghdr)(unsafe.Pointer(&b[0]))
 132         if int(h.Len) < NLMSG_HDRLEN || int(h.Len) > len(b) {
 133                 return nil, nil, 0, EINVAL
 134         }
 135         return h, b[NLMSG_HDRLEN:], nlmAlignOf(int(h.Len)), nil
 136 }
 137
 138 // NetlinkRouteAttr represents a netlink route attribute.
 139 type NetlinkRouteAttr struct {
 140         Attr  RtAttr
 141         Value []byte
 142 }
 143
 144 // ParseNetlinkRouteAttr parses m's payload as an array of netlink
 145 // route attributes and returns the slice containing the
 146 // NetlinkRouteAttr structures.
 147 func ParseNetlinkRouteAttr(m *NetlinkMessage) ([]NetlinkRouteAttr, error) {
 148         var b []byte
 149         switch m.Header.Type {
 150         case RTM_NEWLINK, RTM_DELLINK:
 151                 b = m.Data[SizeofIfInfomsg:]
 152         case RTM_NEWADDR, RTM_DELADDR:
 153                 b = m.Data[SizeofIfAddrmsg:]
 154         case RTM_NEWROUTE, RTM_DELROUTE:
 155                 b = m.Data[SizeofRtMsg:]
 156         default:
 157                 return nil, EINVAL
 158         }
 159         var attrs []NetlinkRouteAttr
 160         for len(b) >= SizeofRtAttr {
 161                 a, vbuf, alen, err := netlinkRouteAttrAndValue(b)
 162                 if err != nil {
 163                         return nil, err
 164                 }
 165                 ra := NetlinkRouteAttr{Attr: *a, Value: vbuf[:int(a.Len)-SizeofRtAttr]}
 166                 attrs = append(attrs, ra)
 167                 b = b[alen:]
 168         }
 169         return attrs, nil
 170 }
 171
 172 func netlinkRouteAttrAndValue(b []byte) (*RtAttr, []byte, int, error) {
 173         a := (*RtAttr)(unsafe.Pointer(&b[0]))
 174         if int(a.Len) < SizeofRtAttr || int(a.Len) > len(b) {
 175                 return nil, nil, 0, EINVAL
 176         }
 177         return a, b[SizeofRtAttr:], rtaAlignOf(int(a.Len)), nil
 178 }