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package dhcpv6
import (
"fmt"
"net"
)
// InterfaceAddresses is used to fetch addresses of an interface with given name
var InterfaceAddresses func(string) ([]net.Addr, error) = interfaceAddresses
func interfaceAddresses(ifname string) ([]net.Addr, error) {
iface, err := net.InterfaceByName(ifname)
if err != nil {
return nil, err
}
return iface.Addrs()
}
func getMatchingAddr(ifname string, matches func(net.IP) bool) (net.IP, error) {
ifaddrs, err := InterfaceAddresses(ifname)
if err != nil {
return nil, err
}
for _, ifaddr := range ifaddrs {
if ifaddr, ok := ifaddr.(*net.IPNet); ok && matches(ifaddr.IP) {
return ifaddr.IP, nil
}
}
return nil, fmt.Errorf("no matching address found for interface %s", ifname)
}
// GetLinkLocalAddr returns a link-local address for the interface
func GetLinkLocalAddr(ifname string) (net.IP, error) {
return getMatchingAddr(ifname, func(ip net.IP) bool {
return ip.To4() == nil && ip.IsLinkLocalUnicast()
})
}
// GetGlobalAddr returns a global address for the interface
func GetGlobalAddr(ifname string) (net.IP, error) {
return getMatchingAddr(ifname, func(ip net.IP) bool {
return ip.To4() == nil && ip.IsGlobalUnicast()
})
}
// GetMacAddressFromEUI64 will return a valid MAC address ONLY if it's a EUI-48
func GetMacAddressFromEUI64(ip net.IP) (net.HardwareAddr, error) {
if ip.To16() == nil {
return nil, fmt.Errorf("IP address shorter than 16 bytes")
}
if isEUI48 := ip[11] == 0xff && ip[12] == 0xfe; !isEUI48 {
return nil, fmt.Errorf("IP address is not an EUI48 address")
}
mac := make(net.HardwareAddr, 6)
copy(mac[0:3], ip[8:11])
copy(mac[3:6], ip[13:16])
mac[0] ^= 0x02
return mac, nil
}
// ExtractMAC looks into the inner most PeerAddr field in the RelayInfo header
// which contains the EUI-64 address of the client making the request, populated
// by the dhcp relay, it is possible to extract the mac address from that IP.
// If that fails, it looks for the MAC addressed embededded in the DUID.
// Note that this only works with type DuidLL and DuidLLT.
// If a mac address cannot be found an error will be returned.
func ExtractMAC(packet DHCPv6) (net.HardwareAddr, error) {
msg := packet
if packet.IsRelay() {
inner, err := DecapsulateRelayIndex(packet, -1)
if err != nil {
return nil, err
}
relay := inner.(*RelayMessage)
if _, mac := relay.Options.ClientLinkLayerAddress(); mac != nil {
return mac, nil
}
if mac, err := GetMacAddressFromEUI64(relay.PeerAddr); err == nil {
return mac, nil
}
msg, err = msg.(*RelayMessage).GetInnerMessage()
if err != nil {
return nil, err
}
}
duid := msg.(*Message).Options.ClientID()
if duid == nil {
return nil, fmt.Errorf("client ID not found in packet")
}
if duid.LinkLayerAddr == nil {
return nil, fmt.Errorf("failed to extract MAC")
}
return duid.LinkLayerAddr, nil
}
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