interface_linux.go

Documentation: net

  // 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.
  
  package net
  
  import (
  	"os"
  	"syscall"
  	"unsafe"
  )
  
  // If the ifindex is zero, interfaceTable returns mappings of all
  // network interfaces. Otherwise it returns a mapping of a specific
  // interface.
  func interfaceTable(ifindex int) ([]Interface, error) {
  	tab, err := syscall.NetlinkRIB(syscall.RTM_GETLINK, syscall.AF_UNSPEC)
  	if err != nil {
  		return nil, os.NewSyscallError("netlinkrib", err)
  	}
  	msgs, err := syscall.ParseNetlinkMessage(tab)
  	if err != nil {
  		return nil, os.NewSyscallError("parsenetlinkmessage", err)
  	}
  	var ift []Interface
  loop:
  	for _, m := range msgs {
  		switch m.Header.Type {
  		case syscall.NLMSG_DONE:
  			break loop
  		case syscall.RTM_NEWLINK:
  			ifim := (*syscall.IfInfomsg)(unsafe.Pointer(&m.Data[0]))
  			if ifindex == 0 || ifindex == int(ifim.Index) {
  				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
  				if err != nil {
  					return nil, os.NewSyscallError("parsenetlinkrouteattr", err)
  				}
  				ift = append(ift, *newLink(ifim, attrs))
  				if ifindex == int(ifim.Index) {
  					break loop
  				}
  			}
  		}
  	}
  	return ift, nil
  }
  
  const (
  	// See linux/if_arp.h.
  	// Note that Linux doesn't support IPv4 over IPv6 tunneling.
  	sysARPHardwareIPv4IPv4 = 768 // IPv4 over IPv4 tunneling
  	sysARPHardwareIPv6IPv6 = 769 // IPv6 over IPv6 tunneling
  	sysARPHardwareIPv6IPv4 = 776 // IPv6 over IPv4 tunneling
  	sysARPHardwareGREIPv4  = 778 // any over GRE over IPv4 tunneling
  	sysARPHardwareGREIPv6  = 823 // any over GRE over IPv6 tunneling
  )
  
  func newLink(ifim *syscall.IfInfomsg, attrs []syscall.NetlinkRouteAttr) *Interface {
  	ifi := &Interface{Index: int(ifim.Index), Flags: linkFlags(ifim.Flags)}
  	for _, a := range attrs {
  		switch a.Attr.Type {
  		case syscall.IFLA_ADDRESS:
  			// We never return any /32 or /128 IP address
  			// prefix on any IP tunnel interface as the
  			// hardware address.
  			switch len(a.Value) {
  			case IPv4len:
  				switch ifim.Type {
  				case sysARPHardwareIPv4IPv4, sysARPHardwareGREIPv4, sysARPHardwareIPv6IPv4:
  					continue
  				}
  			case IPv6len:
  				switch ifim.Type {
  				case sysARPHardwareIPv6IPv6, sysARPHardwareGREIPv6:
  					continue
  				}
  			}
  			var nonzero bool
  			for _, b := range a.Value {
  				if b != 0 {
  					nonzero = true
  					break
  				}
  			}
  			if nonzero {
  				ifi.HardwareAddr = a.Value[:]
  			}
  		case syscall.IFLA_IFNAME:
  			ifi.Name = string(a.Value[:len(a.Value)-1])
  		case syscall.IFLA_MTU:
  			ifi.MTU = int(*(*uint32)(unsafe.Pointer(&a.Value[:4][0])))
  		}
  	}
  	return ifi
  }
  
  func linkFlags(rawFlags uint32) Flags {
  	var f Flags
  	if rawFlags&syscall.IFF_UP != 0 {
  		f |= FlagUp
  	}
  	if rawFlags&syscall.IFF_BROADCAST != 0 {
  		f |= FlagBroadcast
  	}
  	if rawFlags&syscall.IFF_LOOPBACK != 0 {
  		f |= FlagLoopback
  	}
  	if rawFlags&syscall.IFF_POINTOPOINT != 0 {
  		f |= FlagPointToPoint
  	}
  	if rawFlags&syscall.IFF_MULTICAST != 0 {
  		f |= FlagMulticast
  	}
  	return f
  }
  
  // If the ifi is nil, interfaceAddrTable returns addresses for all
  // network interfaces. Otherwise it returns addresses for a specific
  // interface.
  func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
  	tab, err := syscall.NetlinkRIB(syscall.RTM_GETADDR, syscall.AF_UNSPEC)
  	if err != nil {
  		return nil, os.NewSyscallError("netlinkrib", err)
  	}
  	msgs, err := syscall.ParseNetlinkMessage(tab)
  	if err != nil {
  		return nil, os.NewSyscallError("parsenetlinkmessage", err)
  	}
  	var ift []Interface
  	if ifi == nil {
  		var err error
  		ift, err = interfaceTable(0)
  		if err != nil {
  			return nil, err
  		}
  	}
  	ifat, err := addrTable(ift, ifi, msgs)
  	if err != nil {
  		return nil, err
  	}
  	return ifat, nil
  }
  
  func addrTable(ift []Interface, ifi *Interface, msgs []syscall.NetlinkMessage) ([]Addr, error) {
  	var ifat []Addr
  loop:
  	for _, m := range msgs {
  		switch m.Header.Type {
  		case syscall.NLMSG_DONE:
  			break loop
  		case syscall.RTM_NEWADDR:
  			ifam := (*syscall.IfAddrmsg)(unsafe.Pointer(&m.Data[0]))
  			if len(ift) != 0 || ifi.Index == int(ifam.Index) {
  				if len(ift) != 0 {
  					var err error
  					ifi, err = interfaceByIndex(ift, int(ifam.Index))
  					if err != nil {
  						return nil, err
  					}
  				}
  				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
  				if err != nil {
  					return nil, os.NewSyscallError("parsenetlinkrouteattr", err)
  				}
  				ifa := newAddr(ifam, attrs)
  				if ifa != nil {
  					ifat = append(ifat, ifa)
  				}
  			}
  		}
  	}
  	return ifat, nil
  }
  
  func newAddr(ifam *syscall.IfAddrmsg, attrs []syscall.NetlinkRouteAttr) Addr {
  	var ipPointToPoint bool
  	// Seems like we need to make sure whether the IP interface
  	// stack consists of IP point-to-point numbered or unnumbered
  	// addressing.
  	for _, a := range attrs {
  		if a.Attr.Type == syscall.IFA_LOCAL {
  			ipPointToPoint = true
  			break
  		}
  	}
  	for _, a := range attrs {
  		if ipPointToPoint && a.Attr.Type == syscall.IFA_ADDRESS {
  			continue
  		}
  		switch ifam.Family {
  		case syscall.AF_INET:
  			return &IPNet{IP: IPv4(a.Value[0], a.Value[1], a.Value[2], a.Value[3]), Mask: CIDRMask(int(ifam.Prefixlen), 8*IPv4len)}
  		case syscall.AF_INET6:
  			ifa := &IPNet{IP: make(IP, IPv6len), Mask: CIDRMask(int(ifam.Prefixlen), 8*IPv6len)}
  			copy(ifa.IP, a.Value[:])
  			return ifa
  		}
  	}
  	return nil
  }
  
  // interfaceMulticastAddrTable returns addresses for a specific
  // interface.
  func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
  	ifmat4 := parseProcNetIGMP("/proc/net/igmp", ifi)
  	ifmat6 := parseProcNetIGMP6("/proc/net/igmp6", ifi)
  	return append(ifmat4, ifmat6...), nil
  }
  
  func parseProcNetIGMP(path string, ifi *Interface) []Addr {
  	fd, err := open(path)
  	if err != nil {
  		return nil
  	}
  	defer fd.close()
  	var (
  		ifmat []Addr
  		name  string
  	)
  	fd.readLine() // skip first line
  	b := make([]byte, IPv4len)
  	for l, ok := fd.readLine(); ok; l, ok = fd.readLine() {
  		f := splitAtBytes(l, " :\r\t\n")
  		if len(f) < 4 {
  			continue
  		}
  		switch {
  		case l[0] != ' ' && l[0] != '\t': // new interface line
  			name = f[1]
  		case len(f[0]) == 8:
  			if ifi == nil || name == ifi.Name {
  				// The Linux kernel puts the IP
  				// address in /proc/net/igmp in native
  				// endianness.
  				for i := 0; i+1 < len(f[0]); i += 2 {
  					b[i/2], _ = xtoi2(f[0][i:i+2], 0)
  				}
  				i := *(*uint32)(unsafe.Pointer(&b[:4][0]))
  				ifma := &IPAddr{IP: IPv4(byte(i>>24), byte(i>>16), byte(i>>8), byte(i))}
  				ifmat = append(ifmat, ifma)
  			}
  		}
  	}
  	return ifmat
  }
  
  func parseProcNetIGMP6(path string, ifi *Interface) []Addr {
  	fd, err := open(path)
  	if err != nil {
  		return nil
  	}
  	defer fd.close()
  	var ifmat []Addr
  	b := make([]byte, IPv6len)
  	for l, ok := fd.readLine(); ok; l, ok = fd.readLine() {
  		f := splitAtBytes(l, " \r\t\n")
  		if len(f) < 6 {
  			continue
  		}
  		if ifi == nil || f[1] == ifi.Name {
  			for i := 0; i+1 < len(f[2]); i += 2 {
  				b[i/2], _ = xtoi2(f[2][i:i+2], 0)
  			}
  			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]}}
  			ifmat = append(ifmat, ifma)
  		}
  	}
  	return ifmat
  }
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