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Source file src/net/interface_linux.go

Documentation: net

     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  package net
     6  
     7  import (
     8  	"os"
     9  	"syscall"
    10  	"unsafe"
    11  )
    12  
    13  // If the ifindex is zero, interfaceTable returns mappings of all
    14  // network interfaces. Otherwise it returns a mapping of a specific
    15  // interface.
    16  func interfaceTable(ifindex int) ([]Interface, error) {
    17  	tab, err := syscall.NetlinkRIB(syscall.RTM_GETLINK, syscall.AF_UNSPEC)
    18  	if err != nil {
    19  		return nil, os.NewSyscallError("netlinkrib", err)
    20  	}
    21  	msgs, err := syscall.ParseNetlinkMessage(tab)
    22  	if err != nil {
    23  		return nil, os.NewSyscallError("parsenetlinkmessage", err)
    24  	}
    25  	var ift []Interface
    26  loop:
    27  	for _, m := range msgs {
    28  		switch m.Header.Type {
    29  		case syscall.NLMSG_DONE:
    30  			break loop
    31  		case syscall.RTM_NEWLINK:
    32  			ifim := (*syscall.IfInfomsg)(unsafe.Pointer(&m.Data[0]))
    33  			if ifindex == 0 || ifindex == int(ifim.Index) {
    34  				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
    35  				if err != nil {
    36  					return nil, os.NewSyscallError("parsenetlinkrouteattr", err)
    37  				}
    38  				ift = append(ift, *newLink(ifim, attrs))
    39  				if ifindex == int(ifim.Index) {
    40  					break loop
    41  				}
    42  			}
    43  		}
    44  	}
    45  	return ift, nil
    46  }
    47  
    48  const (
    49  	// See linux/if_arp.h.
    50  	// Note that Linux doesn't support IPv4 over IPv6 tunneling.
    51  	sysARPHardwareIPv4IPv4 = 768 // IPv4 over IPv4 tunneling
    52  	sysARPHardwareIPv6IPv6 = 769 // IPv6 over IPv6 tunneling
    53  	sysARPHardwareIPv6IPv4 = 776 // IPv6 over IPv4 tunneling
    54  	sysARPHardwareGREIPv4  = 778 // any over GRE over IPv4 tunneling
    55  	sysARPHardwareGREIPv6  = 823 // any over GRE over IPv6 tunneling
    56  )
    57  
    58  func newLink(ifim *syscall.IfInfomsg, attrs []syscall.NetlinkRouteAttr) *Interface {
    59  	ifi := &Interface{Index: int(ifim.Index), Flags: linkFlags(ifim.Flags)}
    60  	for _, a := range attrs {
    61  		switch a.Attr.Type {
    62  		case syscall.IFLA_ADDRESS:
    63  			// We never return any /32 or /128 IP address
    64  			// prefix on any IP tunnel interface as the
    65  			// hardware address.
    66  			switch len(a.Value) {
    67  			case IPv4len:
    68  				switch ifim.Type {
    69  				case sysARPHardwareIPv4IPv4, sysARPHardwareGREIPv4, sysARPHardwareIPv6IPv4:
    70  					continue
    71  				}
    72  			case IPv6len:
    73  				switch ifim.Type {
    74  				case sysARPHardwareIPv6IPv6, sysARPHardwareGREIPv6:
    75  					continue
    76  				}
    77  			}
    78  			var nonzero bool
    79  			for _, b := range a.Value {
    80  				if b != 0 {
    81  					nonzero = true
    82  					break
    83  				}
    84  			}
    85  			if nonzero {
    86  				ifi.HardwareAddr = a.Value[:]
    87  			}
    88  		case syscall.IFLA_IFNAME:
    89  			ifi.Name = string(a.Value[:len(a.Value)-1])
    90  		case syscall.IFLA_MTU:
    91  			ifi.MTU = int(*(*uint32)(unsafe.Pointer(&a.Value[:4][0])))
    92  		}
    93  	}
    94  	return ifi
    95  }
    96  
    97  func linkFlags(rawFlags uint32) Flags {
    98  	var f Flags
    99  	if rawFlags&syscall.IFF_UP != 0 {
   100  		f |= FlagUp
   101  	}
   102  	if rawFlags&syscall.IFF_BROADCAST != 0 {
   103  		f |= FlagBroadcast
   104  	}
   105  	if rawFlags&syscall.IFF_LOOPBACK != 0 {
   106  		f |= FlagLoopback
   107  	}
   108  	if rawFlags&syscall.IFF_POINTOPOINT != 0 {
   109  		f |= FlagPointToPoint
   110  	}
   111  	if rawFlags&syscall.IFF_MULTICAST != 0 {
   112  		f |= FlagMulticast
   113  	}
   114  	return f
   115  }
   116  
   117  // If the ifi is nil, interfaceAddrTable returns addresses for all
   118  // network interfaces. Otherwise it returns addresses for a specific
   119  // interface.
   120  func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
   121  	tab, err := syscall.NetlinkRIB(syscall.RTM_GETADDR, syscall.AF_UNSPEC)
   122  	if err != nil {
   123  		return nil, os.NewSyscallError("netlinkrib", err)
   124  	}
   125  	msgs, err := syscall.ParseNetlinkMessage(tab)
   126  	if err != nil {
   127  		return nil, os.NewSyscallError("parsenetlinkmessage", err)
   128  	}
   129  	var ift []Interface
   130  	if ifi == nil {
   131  		var err error
   132  		ift, err = interfaceTable(0)
   133  		if err != nil {
   134  			return nil, err
   135  		}
   136  	}
   137  	ifat, err := addrTable(ift, ifi, msgs)
   138  	if err != nil {
   139  		return nil, err
   140  	}
   141  	return ifat, nil
   142  }
   143  
   144  func addrTable(ift []Interface, ifi *Interface, msgs []syscall.NetlinkMessage) ([]Addr, error) {
   145  	var ifat []Addr
   146  loop:
   147  	for _, m := range msgs {
   148  		switch m.Header.Type {
   149  		case syscall.NLMSG_DONE:
   150  			break loop
   151  		case syscall.RTM_NEWADDR:
   152  			ifam := (*syscall.IfAddrmsg)(unsafe.Pointer(&m.Data[0]))
   153  			if len(ift) != 0 || ifi.Index == int(ifam.Index) {
   154  				if len(ift) != 0 {
   155  					var err error
   156  					ifi, err = interfaceByIndex(ift, int(ifam.Index))
   157  					if err != nil {
   158  						return nil, err
   159  					}
   160  				}
   161  				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
   162  				if err != nil {
   163  					return nil, os.NewSyscallError("parsenetlinkrouteattr", err)
   164  				}
   165  				ifa := newAddr(ifam, attrs)
   166  				if ifa != nil {
   167  					ifat = append(ifat, ifa)
   168  				}
   169  			}
   170  		}
   171  	}
   172  	return ifat, nil
   173  }
   174  
   175  func newAddr(ifam *syscall.IfAddrmsg, attrs []syscall.NetlinkRouteAttr) Addr {
   176  	var ipPointToPoint bool
   177  	// Seems like we need to make sure whether the IP interface
   178  	// stack consists of IP point-to-point numbered or unnumbered
   179  	// addressing.
   180  	for _, a := range attrs {
   181  		if a.Attr.Type == syscall.IFA_LOCAL {
   182  			ipPointToPoint = true
   183  			break
   184  		}
   185  	}
   186  	for _, a := range attrs {
   187  		if ipPointToPoint && a.Attr.Type == syscall.IFA_ADDRESS {
   188  			continue
   189  		}
   190  		switch ifam.Family {
   191  		case syscall.AF_INET:
   192  			return &IPNet{IP: IPv4(a.Value[0], a.Value[1], a.Value[2], a.Value[3]), Mask: CIDRMask(int(ifam.Prefixlen), 8*IPv4len)}
   193  		case syscall.AF_INET6:
   194  			ifa := &IPNet{IP: make(IP, IPv6len), Mask: CIDRMask(int(ifam.Prefixlen), 8*IPv6len)}
   195  			copy(ifa.IP, a.Value[:])
   196  			return ifa
   197  		}
   198  	}
   199  	return nil
   200  }
   201  
   202  // interfaceMulticastAddrTable returns addresses for a specific
   203  // interface.
   204  func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
   205  	ifmat4 := parseProcNetIGMP("/proc/net/igmp", ifi)
   206  	ifmat6 := parseProcNetIGMP6("/proc/net/igmp6", ifi)
   207  	return append(ifmat4, ifmat6...), nil
   208  }
   209  
   210  func parseProcNetIGMP(path string, ifi *Interface) []Addr {
   211  	fd, err := open(path)
   212  	if err != nil {
   213  		return nil
   214  	}
   215  	defer fd.close()
   216  	var (
   217  		ifmat []Addr
   218  		name  string
   219  	)
   220  	fd.readLine() // skip first line
   221  	b := make([]byte, IPv4len)
   222  	for l, ok := fd.readLine(); ok; l, ok = fd.readLine() {
   223  		f := splitAtBytes(l, " :\r\t\n")
   224  		if len(f) < 4 {
   225  			continue
   226  		}
   227  		switch {
   228  		case l[0] != ' ' && l[0] != '\t': // new interface line
   229  			name = f[1]
   230  		case len(f[0]) == 8:
   231  			if ifi == nil || name == ifi.Name {
   232  				// The Linux kernel puts the IP
   233  				// address in /proc/net/igmp in native
   234  				// endianness.
   235  				for i := 0; i+1 < len(f[0]); i += 2 {
   236  					b[i/2], _ = xtoi2(f[0][i:i+2], 0)
   237  				}
   238  				i := *(*uint32)(unsafe.Pointer(&b[:4][0]))
   239  				ifma := &IPAddr{IP: IPv4(byte(i>>24), byte(i>>16), byte(i>>8), byte(i))}
   240  				ifmat = append(ifmat, ifma)
   241  			}
   242  		}
   243  	}
   244  	return ifmat
   245  }
   246  
   247  func parseProcNetIGMP6(path string, ifi *Interface) []Addr {
   248  	fd, err := open(path)
   249  	if err != nil {
   250  		return nil
   251  	}
   252  	defer fd.close()
   253  	var ifmat []Addr
   254  	b := make([]byte, IPv6len)
   255  	for l, ok := fd.readLine(); ok; l, ok = fd.readLine() {
   256  		f := splitAtBytes(l, " \r\t\n")
   257  		if len(f) < 6 {
   258  			continue
   259  		}
   260  		if ifi == nil || f[1] == ifi.Name {
   261  			for i := 0; i+1 < len(f[2]); i += 2 {
   262  				b[i/2], _ = xtoi2(f[2][i:i+2], 0)
   263  			}
   264  			ifma := &IPAddr{IP: IP{b[0], b[1], b[2], b[3], b[4], b[5], b[6], b[7], b[8], b[9], b[10], b[11], b[12], b[13], b[14], b[15]}}
   265  			ifmat = append(ifmat, ifma)
   266  		}
   267  	}
   268  	return ifmat
   269  }
   270  

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