func (h *DHCPHandler) ServeDHCP(p dhcp.Packet, msgType dhcp.MessageType, options dhcp.Options) (d dhcp.Packet) {
// First find the subnet to use. giaddr field to lookup subnet if not all zeros.
// If all zeros, use the interfaces Addrs to find a subnet, first wins.
var subnet *Subnet
subnet = nil
giaddr := p.GIAddr()
if !giaddr.Equal(net.IPv4zero) {
subnet = h.info.FindSubnet(giaddr)
} else {
log.Println("Received Broadcast/Local message on ", h.intf.Name)
addrs, err := h.intf.Addrs()
if err != nil {
log.Println("Can't find addresses for ", h.intf.Name, ": ", err)
}
for _, a := range addrs {
aip, _, _ := net.ParseCIDR(a.String())
// Only operate on v4 addresses
if aip.To4() == nil {
continue
}
subnet = h.info.FindSubnet(aip)
if subnet != nil {
break
}
}
if ignore_anonymus {
// Search all subnets for a binding. First wins
log.Println("Looking up bound subnet for ", p.CHAddr().String())
subnet = h.info.FindBoundIP(p.CHAddr())
}
if subnet == nil {
// We didn't find a subnet for the interface. Look for the assigned server IP
subnet = h.info.FindSubnet(h.ip)
}
}
if subnet == nil {
log.Println("Can not find subnet for packet, ignoring")
return
}
nic := p.CHAddr().String()
switch msgType {
case dhcp.Discover:
lease, binding := subnet.find_or_get_info(h.info, nic, p.CIAddr())
if lease == nil {
log.Println("Out of IPs for ", subnet.Name, ", ignoring")
return nil
}
// Ignore unknown MAC address
if ignore_anonymus && binding == nil {
log.Println("Ignoring request from unknown MAC address")
return dhcp.ReplyPacket(p, dhcp.NAK, h.ip, nil, 0, nil)
}
options, lease_time := subnet.build_options(lease, binding)
reply := dhcp.ReplyPacket(p, dhcp.Offer,
h.ip,
lease.Ip,
lease_time,
subnet.Options.SelectOrderOrAll(options[dhcp.OptionParameterRequestList]))
log.Println("Discover: Handing out: ", reply.YIAddr(), " to ", reply.CHAddr())
return reply
case dhcp.Request:
server, ok := options[dhcp.OptionServerIdentifier]
if ok && !net.IP(server).Equal(h.ip) {
return nil // Message not for this dhcp server
}
reqIP := net.IP(options[dhcp.OptionRequestedIPAddress])
if reqIP == nil {
reqIP = net.IP(p.CIAddr())
}
if len(reqIP) != 4 || reqIP.Equal(net.IPv4zero) {
return dhcp.ReplyPacket(p, dhcp.NAK, h.ip, nil, 0, nil)
}
lease, binding := subnet.find_info(h.info, nic)
// Ignore unknown MAC address
if ignore_anonymus && binding == nil {
log.Println("Ignoring request from unknown MAC address")
return dhcp.ReplyPacket(p, dhcp.NAK, h.ip, nil, 0, nil)
}
if lease == nil || !lease.Ip.Equal(reqIP) {
return dhcp.ReplyPacket(p, dhcp.NAK, h.ip, nil, 0, nil)
}
options, lease_time := subnet.build_options(lease, binding)
subnet.update_lease_time(h.info, lease, lease_time)
reply := dhcp.ReplyPacket(p, dhcp.ACK,
h.ip,
lease.Ip,
lease_time,
subnet.Options.SelectOrderOrAll(options[dhcp.OptionParameterRequestList]))
if binding != nil && binding.NextServer != nil {
reply.SetSIAddr(net.ParseIP(*binding.NextServer))
} else if subnet.NextServer != nil {
reply.SetSIAddr(*subnet.NextServer)
}
log.Println("Request: Handing out: ", reply.YIAddr(), " to ", reply.CHAddr())
return reply
case dhcp.Release, dhcp.Decline:
nic := p.CHAddr().String()
subnet.free_lease(h.info, nic)
}
return nil
}
