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@@ -0,0 +1,96 @@
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+// Copyright 2018-present the CoreDHCP Authors. All rights reserved
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+// This source code is licensed under the MIT license found in the
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+// LICENSE file in the root directory of this source tree.
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+
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+// +build linux
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+
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+package server
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+
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+import (
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+ "fmt"
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+ "net"
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+ "syscall"
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+
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+ "github.com/google/gopacket"
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+ "github.com/google/gopacket/layers"
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+ "github.com/insomniacslk/dhcp/dhcpv4"
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+)
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+
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+//this function sends an unicast to the hardware address defined in resp.ClientHWAddr,
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+//the layer3 destination address is still the broadcast address;
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+//iface: the interface where the DHCP message should be sent;
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+//resp: DHCPv4 struct, which should be sent;
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+func sendEthernet(iface net.Interface, resp *dhcpv4.DHCPv4) error {
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+
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+ eth := layers.Ethernet{
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+ EthernetType: layers.EthernetTypeIPv4,
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+ SrcMAC: iface.HardwareAddr,
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+ DstMAC: resp.ClientHWAddr,
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+ }
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+ ip := layers.IPv4{
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+ Version: 4,
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+ TTL: 64,
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+ SrcIP: resp.ServerIPAddr,
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+ DstIP: resp.YourIPAddr,
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+ Protocol: layers.IPProtocolUDP,
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+ Flags: layers.IPv4DontFragment,
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+ }
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+ udp := layers.UDP{
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+ SrcPort: dhcpv4.ServerPort,
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+ DstPort: dhcpv4.ClientPort,
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+ }
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+
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+ err := udp.SetNetworkLayerForChecksum(&ip)
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+ if err != nil {
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+ return fmt.Errorf("Send Ethernet: Couldn't set network layer: %v", err)
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+ }
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+
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+ buf := gopacket.NewSerializeBuffer()
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+ opts := gopacket.SerializeOptions{
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+ ComputeChecksums: true,
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+ FixLengths: true,
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+ }
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+
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+ // Decode a packet
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+ packet := gopacket.NewPacket(resp.ToBytes(), layers.LayerTypeDHCPv4, gopacket.NoCopy)
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+ dhcpLayer := packet.Layer(layers.LayerTypeDHCPv4)
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+ dhcp, ok := dhcpLayer.(gopacket.SerializableLayer)
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+ if !ok {
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+ return fmt.Errorf("Layer %s is not serializable", dhcpLayer.LayerType().String())
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+ }
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+ err = gopacket.SerializeLayers(buf, opts, ð, &ip, &udp, dhcp)
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+ if err != nil {
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+ return fmt.Errorf("Cannot serialize layer: %v", err)
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+ }
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+ data := buf.Bytes()
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+
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+ fd, err := syscall.Socket(syscall.AF_PACKET, syscall.SOCK_RAW, 0)
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+ if err != nil {
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+ return fmt.Errorf("Send Ethernet: Cannot open socket: %v", err)
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+ }
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+ defer func() {
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+ err = syscall.Close(fd)
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+ if err != nil {
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+ log.Errorf("Send Ethernet: Cannot close socket: %v", err)
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+ }
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+ }()
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+
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+ err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
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+ if err != nil {
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+ log.Errorf("Send Ethernet: Cannot set option for socket: %v", err)
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+ }
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+
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+ var hwAddr [8]byte
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+ copy(hwAddr[0:6], resp.ClientHWAddr[0:6])
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+ ethAddr := syscall.SockaddrLinklayer{
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+ Protocol: 0,
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+ Ifindex: iface.Index,
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+ Halen: 6,
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+ Addr: hwAddr, //not used
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+ }
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+ err = syscall.Sendto(fd, data, 0, ðAddr)
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+ if err != nil {
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+ return fmt.Errorf("Cannot send frame via socket: %v", err)
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+ }
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+ return nil
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+}
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dza1