// ServeDHCP is called by dhcp4.ListenAndServe when the service is started
func (d *DHCPService) ServeDHCP(packet dhcp4.Packet, msgType dhcp4.MessageType, reqOptions dhcp4.Options) (response dhcp4.Packet) {
switch msgType {
case dhcp4.Discover:
// RFC 2131 4.3.1
// FIXME: send to StatHat and/or increment a counter
mac := packet.CHAddr()
// Check MAC blacklist
if !d.isMACPermitted(mac) {
log.Printf("DHCP Discover from %s\n is not permitted", mac.String())
return nil
}
log.Printf("DHCP Discover from %s\n", mac.String())
// Look up the MAC entry with cascaded attributes
lease, found, err := d.db.GetMAC(mac, true)
if err != nil {
return nil
}
// Existing Lease
if found {
options := d.getOptionsFromMAC(lease)
log.Printf("DHCP Discover from %s (we offer %s from current lease)\n", lease.MAC.String(), lease.IP.String())
// for x, y := range reqOptions {
// log.Printf("\tR[%v] %v %s\n", x, y, y)
// }
// for x, y := range options {
// log.Printf("\tO[%v] %v %s\n", x, y, y)
// }
return dhcp4.ReplyPacket(packet, dhcp4.Offer, d.ip.To4(), lease.IP.To4(), d.getLeaseDurationForRequest(reqOptions, lease.Duration), options.SelectOrderOrAll(reqOptions[dhcp4.OptionParameterRequestList]))
}
// New Lease
ip := d.getIPFromPool()
if ip != nil {
options := d.getOptionsFromMAC(lease)
log.Printf("DHCP Discover from %s (we offer %s from pool)\n", mac.String(), ip.String())
// for x, y := range reqOptions {
// log.Printf("\tR[%v] %v %s\n", x, y, y)
// }
// for x, y := range options {
// log.Printf("\tO[%v] %v %s\n", x, y, y)
// }
return dhcp4.ReplyPacket(packet, dhcp4.Offer, d.ip.To4(), ip.To4(), d.getLeaseDurationForRequest(reqOptions, d.leaseDuration), options.SelectOrderOrAll(reqOptions[dhcp4.OptionParameterRequestList]))
}
log.Printf("DHCP Discover from %s (no offer due to no addresses available in pool)\n", mac.String())
// FIXME: Send to StatHat and/or increment a counter
// TODO: Send an email?
return nil
case dhcp4.Request:
// RFC 2131 4.3.2
// FIXME: send to StatHat and/or increment a counter
mac := packet.CHAddr()
// Check MAC blacklist
if !d.isMACPermitted(mac) {
log.Printf("DHCP Request from %s\n is not permitted", mac.String())
return nil
}
// Check IP presence
state, requestedIP := d.getRequestState(packet, reqOptions)
log.Printf("DHCP Request (%s) from %s...\n", state, mac.String())
if len(requestedIP) == 0 || requestedIP.IsUnspecified() { // no IP provided at all... why? FIXME
log.Printf("DHCP Request (%s) from %s (empty IP, so we're just ignoring this request)\n", state, mac.String())
return nil
}
// Check IPv4
if len(requestedIP) != net.IPv4len {
log.Printf("DHCP Request (%s) from %s wanting %s (IPv6 address requested, so we're just ignoring this request)\n", state, mac.String(), requestedIP.String())
return nil
}
// Check IP subnet
if !d.subnet.Contains(requestedIP) {
log.Printf("DHCP Request (%s) from %s wanting %s (we reject due to wrong subnet)\n", state, mac.String(), requestedIP.String())
return dhcp4.ReplyPacket(packet, dhcp4.NAK, d.ip.To4(), nil, 0, nil)
}
// Check Target Server
targetServerIP := packet.SIAddr()
if len(targetServerIP) > 0 && !targetServerIP.IsUnspecified() {
log.Printf("DHCP Request (%s) from %s wanting %s is in response to a DHCP offer from %s\n", state, mac.String(), requestedIP.String(), targetServerIP.String())
if d.ip.Equal(targetServerIP) {
return nil
}
}
// Process Request
log.Printf("DHCP Request (%s) from %s wanting %s...\n", state, mac.String(), requestedIP.String())
lease, found, err := d.db.GetMAC(mac, true)
if err != nil {
return nil
}
if found {
// Existing Lease
lease.Duration = d.getLeaseDurationForRequest(reqOptions, d.leaseDuration)
if lease.IP.Equal(requestedIP) {
err = d.db.RenewLease(lease)
} else {
log.Printf("DHCP Request (%s) from %s wanting %s (we reject due to lease mismatch, should be %s)\n", state, lease.MAC.String(), requestedIP.String(), lease.IP.String())
return dhcp4.ReplyPacket(packet, dhcp4.NAK, d.ip.To4(), nil, 0, nil)
}
} else {
// Check IP subnet is within the guestPool (we don't want users requesting non-pool addresses unless we assigned it to their MAC, administratively)
if !d.guestPool.Contains(requestedIP) {
log.Printf("DHCP Request (%s) from %s wanting %s (we reject due to not being within the guestPool)\n", state, mac.String(), requestedIP.String())
return dhcp4.ReplyPacket(packet, dhcp4.NAK, d.ip.To4(), nil, 0, nil)
}
// New lease
lease = &MACEntry{
MAC: mac,
IP: requestedIP,
Duration: d.getLeaseDurationForRequest(reqOptions, d.leaseDuration),
}
err = d.db.CreateLease(lease)
}
if err == nil {
d.maintainDNSRecords(lease, packet, reqOptions) // TODO: Move this?
options := d.getOptionsFromMAC(lease)
log.Printf("DHCP Request (%s) from %s wanting %s (we agree)\n", state, mac.String(), requestedIP.String())
return dhcp4.ReplyPacket(packet, dhcp4.ACK, d.ip.To4(), requestedIP.To4(), lease.Duration, options.SelectOrderOrAll(reqOptions[dhcp4.OptionParameterRequestList]))
}
log.Printf("DHCP Request (%s) from %s wanting %s (we reject due to address collision)\n", state, mac.String(), requestedIP.String())
return dhcp4.ReplyPacket(packet, dhcp4.NAK, d.ip.To4(), nil, 0, nil)
case dhcp4.Decline:
// RFC 2131 4.3.3
// FIXME: release from DB? tick a flag? increment a counter? send to StatHat?
mac := packet.CHAddr()
log.Printf("DHCP Decline from %s\n", mac.String())
case dhcp4.Release:
// RFC 2131 4.3.4
// FIXME: release from DB? tick a flag? increment a counter? send to StatHat?
mac := packet.CHAddr()
log.Printf("DHCP Release from %s\n", mac.String())
case dhcp4.Inform:
// RFC 2131 4.3.5
// https://tools.ietf.org/html/draft-ietf-dhc-dhcpinform-clarify-06
// FIXME: release from DB? tick a flag? increment a counter? send to StatHat?
// FIXME: we should reply with valuable info, but not assign an IP to this client, per RFC 2131 for DHCPINFORM
// NOTE: the client's IP is supposed to only be in the ciaddr field, not the requested IP field, per RFC 2131 4.4.3
mac := packet.CHAddr()
ip := packet.CIAddr()
if len(ip) > 0 && !ip.IsUnspecified() {
log.Printf("DHCP Inform from %s for %s \n", mac.String(), ip.String())
if len(ip) == net.IPv4len && d.guestPool.Contains(ip) {
entry, found, _ := d.db.GetMAC(mac, true)
if found {
options := d.getOptionsFromMAC(entry)
return informReplyPacket(packet, dhcp4.ACK, d.ip.To4(), options.SelectOrderOrAll(reqOptions[dhcp4.OptionParameterRequestList]))
}
}
}
}
return nil
}
