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* dhcp: refactor

This commit is contained in:
Simon Zolin 2019-03-06 15:13:27 +03:00
parent b5f0d48e7f
commit 92cf7c1aca
1 changed files with 94 additions and 50 deletions
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128
dhcpd/dhcpd.go
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@ -4,6 +4,7 @@ import (
"bytes" "bytes"
"fmt" "fmt"
"net" "net"
"strings"
"sync" "sync"
"time" "time"
@ -59,6 +60,16 @@ type Server struct {
sync.RWMutex sync.RWMutex
} }
// Print information about the available network interfaces
func printInterfaces() {
ifaces, _ := net.Interfaces()
var buf strings.Builder
for i := range ifaces {
buf.WriteString(fmt.Sprintf("\"%s\", ", ifaces[i].Name))
}
log.Info("Available network interfaces: %s", buf.String())
}
// Start will listen on port 67 and serve DHCP requests. // Start will listen on port 67 and serve DHCP requests.
// Even though config can be nil, it is not optional (at least for now), since there are no default values (yet). // Even though config can be nil, it is not optional (at least for now), since there are no default values (yet).
func (s *Server) Start(config *ServerConfig) error { func (s *Server) Start(config *ServerConfig) error {
@ -69,6 +80,7 @@ func (s *Server) Start(config *ServerConfig) error {
iface, err := net.InterfaceByName(s.InterfaceName) iface, err := net.InterfaceByName(s.InterfaceName)
if err != nil { if err != nil {
s.closeConn() // in case it was already started s.closeConn() // in case it was already started
printInterfaces()
return wrapErrPrint(err, "Couldn't find interface by name %s", s.InterfaceName) return wrapErrPrint(err, "Couldn't find interface by name %s", s.InterfaceName)
} }
@ -189,6 +201,7 @@ func (s *Server) closeConn() error {
return err return err
} }
// Reserve a lease for the client
func (s *Server) reserveLease(p dhcp4.Packet) (*Lease, error) { func (s *Server) reserveLease(p dhcp4.Packet) (*Lease, error) {
// WARNING: do not remove copy() // WARNING: do not remove copy()
// the given hwaddr by p.CHAddr() in the packet survives only during ServeDHCP() call // the given hwaddr by p.CHAddr() in the packet survives only during ServeDHCP() call
@ -196,11 +209,6 @@ func (s *Server) reserveLease(p dhcp4.Packet) (*Lease, error) {
hwaddrCOW := p.CHAddr() hwaddrCOW := p.CHAddr()
hwaddr := make(net.HardwareAddr, len(hwaddrCOW)) hwaddr := make(net.HardwareAddr, len(hwaddrCOW))
copy(hwaddr, hwaddrCOW) copy(hwaddr, hwaddrCOW)
foundLease := s.locateLease(p)
if foundLease != nil {
// log.Tracef("found lease for %s: %+v", hwaddr, foundLease)
return foundLease, nil
}
// not assigned a lease, create new one, find IP from LRU // not assigned a lease, create new one, find IP from LRU
log.Tracef("Lease not found for %s: creating new one", hwaddr) log.Tracef("Lease not found for %s: creating new one", hwaddr)
ip, err := s.findFreeIP(hwaddr) ip, err := s.findFreeIP(hwaddr)
@ -216,7 +224,8 @@ func (s *Server) reserveLease(p dhcp4.Packet) (*Lease, error) {
return lease, nil return lease, nil
} }
func (s *Server) locateLease(p dhcp4.Packet) *Lease { // Find a lease for the client
func (s *Server) findLease(p dhcp4.Packet) *Lease {
hwaddr := p.CHAddr() hwaddr := p.CHAddr()
for i := range s.leases { for i := range s.leases {
if bytes.Equal([]byte(hwaddr), []byte(s.leases[i].HWAddr)) { if bytes.Equal([]byte(hwaddr), []byte(s.leases[i].HWAddr)) {
@ -243,7 +252,6 @@ func (s *Server) findFreeIP(hwaddr net.HardwareAddr) (net.IP, error) {
// if !bytes.Equal(foundHWaddr, hwaddr) { // if !bytes.Equal(foundHWaddr, hwaddr) {
// log.Tracef("SHOULD NOT HAPPEN: hwaddr in IP pool %s is not equal to hwaddr in lease %s", foundHWaddr, hwaddr) // log.Tracef("SHOULD NOT HAPPEN: hwaddr in IP pool %s is not equal to hwaddr in lease %s", foundHWaddr, hwaddr)
// } // }
log.Tracef("will try again")
continue continue
} }
foundIP = newIP foundIP = newIP
@ -280,12 +288,7 @@ func (s *Server) unreserveIP(ip net.IP) {
// ServeDHCP handles an incoming DHCP request // ServeDHCP handles an incoming DHCP request
func (s *Server) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dhcp4.Options) dhcp4.Packet { func (s *Server) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dhcp4.Options) dhcp4.Packet {
log.Tracef("Message from client %s: %d", p.CHAddr(), msgType) s.printLeases()
log.Tracef("Leases:")
for i, lease := range s.leases {
log.Tracef("Lease #%d: hwaddr %s, ip %s, expiry %s", i, lease.HWAddr, lease.IP, lease.Expiry)
}
switch msgType { switch msgType {
case dhcp4.Discover: // Broadcast Packet From Client - Can I have an IP? case dhcp4.Discover: // Broadcast Packet From Client - Can I have an IP?
@ -297,26 +300,26 @@ func (s *Server) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dh
return s.handleDHCP4Request(p, options) return s.handleDHCP4Request(p, options)
case dhcp4.Decline: // Broadcast From Client - Sorry I can't use that IP case dhcp4.Decline: // Broadcast From Client - Sorry I can't use that IP
log.Tracef("Got from client: Decline") return s.handleDecline(p, options)
case dhcp4.Release: // From Client, I don't need that IP anymore case dhcp4.Release: // From Client, I don't need that IP anymore
log.Tracef("Got from client: Release") return s.handleRelease(p, options)
case dhcp4.Inform: // From Client, I have this IP and there's nothing you can do about it case dhcp4.Inform: // From Client, I have this IP and there's nothing you can do about it
log.Tracef("Got from client: Inform") return s.handleInform(p, options)
// from server -- ignore those but enumerate just in case // from server -- ignore those but enumerate just in case
case dhcp4.Offer: // Broadcast From Server - Here's an IP case dhcp4.Offer: // Broadcast From Server - Here's an IP
log.Printf("DHCP: received message from another server: Offer") log.Printf("DHCP: received message from %s: Offer", p.CHAddr())
case dhcp4.ACK: // From Server, Yes you can have that IP case dhcp4.ACK: // From Server, Yes you can have that IP
log.Printf("DHCP: received message from another server: ACK") log.Printf("DHCP: received message from %s: ACK", p.CHAddr())
case dhcp4.NAK: // From Server, No you cannot have that IP case dhcp4.NAK: // From Server, No you cannot have that IP
log.Printf("DHCP: received message from another server: NAK") log.Printf("DHCP: received message from %s: NAK", p.CHAddr())
default: default:
log.Printf("DHCP: unknown packet %v from client %s", msgType, p.CHAddr()) log.Printf("DHCP: unknown packet %v from %s", msgType, p.CHAddr())
return nil return nil
} }
return nil return nil
@ -324,14 +327,25 @@ func (s *Server) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dh
func (s *Server) handleDiscover(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet { func (s *Server) handleDiscover(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet {
// find a lease, but don't update lease time // find a lease, but don't update lease time
var lease *Lease
var err error
lease, err := s.reserveLease(p) reqIP := net.IP(options[dhcp4.OptionRequestedIPAddress])
hostname := p.ParseOptions()[dhcp4.OptionHostName]
log.Tracef("Message from client: Discover. ReqIP: %s HW: %s Hostname: %s",
reqIP, p.CHAddr(), hostname)
lease = s.findLease(p)
for lease == nil {
lease, err = s.reserveLease(p)
if err != nil { if err != nil {
log.Tracef("Couldn't find free lease: %s", err) log.Error("Couldn't find free lease: %s", err)
// couldn't find lease, don't respond
return nil return nil
} }
break
}
opt := s.leaseOptions.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList]) opt := s.leaseOptions.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList])
reply := dhcp4.ReplyPacket(p, dhcp4.Offer, s.ipnet.IP, lease.IP, s.leaseTime, opt) reply := dhcp4.ReplyPacket(p, dhcp4.Offer, s.ipnet.IP, lease.IP, s.leaseTime, opt)
log.Tracef("Replying with offer: offered IP %v for %v with options %+v", lease.IP, s.leaseTime, reply.ParseOptions()) log.Tracef("Replying with offer: offered IP %v for %v with options %+v", lease.IP, s.leaseTime, reply.ParseOptions())
@ -339,49 +353,70 @@ func (s *Server) handleDiscover(p dhcp4.Packet, options dhcp4.Options) dhcp4.Pac
} }
func (s *Server) handleDHCP4Request(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet { func (s *Server) handleDHCP4Request(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet {
var lease *Lease
var err error
reqIP := net.IP(options[dhcp4.OptionRequestedIPAddress])
log.Tracef("Message from client: Request. IP: %s ReqIP: %s HW: %s",
p.CIAddr(), reqIP, p.CHAddr())
server := options[dhcp4.OptionServerIdentifier] server := options[dhcp4.OptionServerIdentifier]
if server != nil && !net.IP(server).Equal(s.ipnet.IP) { if server != nil && !net.IP(server).Equal(s.ipnet.IP) {
log.Tracef("Request message not for this DHCP server (%v vs %v)", server, s.ipnet.IP) log.Tracef("Request message not for this DHCP server (%v vs %v)", server, s.ipnet.IP)
return nil // Message not for this dhcp server return nil // Message not for this dhcp server
} }
reqIP := net.IP(options[dhcp4.OptionRequestedIPAddress])
if reqIP == nil { if reqIP == nil {
reqIP = p.CIAddr() reqIP = p.CIAddr()
}
if reqIP.To4() == nil { } else if reqIP == nil || reqIP.To4() == nil {
log.Tracef("Replying with NAK: request IP isn't valid IPv4: %s", reqIP) log.Tracef("Requested IP isn't a valid IPv4: %s", reqIP)
return dhcp4.ReplyPacket(p, dhcp4.NAK, s.ipnet.IP, nil, 0, nil) return dhcp4.ReplyPacket(p, dhcp4.NAK, s.ipnet.IP, nil, 0, nil)
} }
if reqIP.Equal(net.IPv4zero) { lease = s.findLease(p)
log.Tracef("Replying with NAK: request IP is 0.0.0.0") if lease == nil {
return dhcp4.ReplyPacket(p, dhcp4.NAK, s.ipnet.IP, nil, 0, nil) lease, err = s.reserveLease(p)
}
log.Tracef("requested IP is %s", reqIP)
lease, err := s.reserveLease(p)
if err != nil { if err != nil {
log.Tracef("Couldn't find free lease: %s", err) log.Tracef("Couldn't find free lease: %s", err)
// couldn't find lease, don't respond // couldn't find lease, don't respond
return nil return nil
} }
}
if !lease.IP.Equal(reqIP) {
log.Tracef("Lease for %s doesn't match requested/client IP: %s vs %s",
lease.HWAddr, lease.IP, reqIP)
return dhcp4.ReplyPacket(p, dhcp4.NAK, s.ipnet.IP, nil, 0, nil)
}
if lease.IP.Equal(reqIP) {
// IP matches lease IP, nothing else to do
lease.Expiry = time.Now().Add(s.leaseTime) lease.Expiry = time.Now().Add(s.leaseTime)
log.Tracef("Replying with ACK: request IP matches lease IP, nothing else to do. IP %v for %v", lease.IP, p.CHAddr()) log.Tracef("Replying with ACK. IP: %s HW: %s Expire: %s",
lease.IP, lease.HWAddr, lease.Expiry)
opt := s.leaseOptions.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList]) opt := s.leaseOptions.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList])
return dhcp4.ReplyPacket(p, dhcp4.ACK, s.ipnet.IP, lease.IP, s.leaseTime, opt) return dhcp4.ReplyPacket(p, dhcp4.ACK, s.ipnet.IP, lease.IP, s.leaseTime, opt)
} }
// func (s *Server) handleInform(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet {
// requested IP different from lease log.Tracef("Message from client: Inform. IP: %s HW: %s",
// p.CIAddr(), p.CHAddr())
log.Tracef("lease IP is different from requested IP: %s vs %s", lease.IP, reqIP) return nil
return dhcp4.ReplyPacket(p, dhcp4.NAK, s.ipnet.IP, nil, 0, nil) }
func (s *Server) handleRelease(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet {
log.Tracef("Message from client: Release. IP: %s HW: %s",
p.CIAddr(), p.CHAddr())
return nil
}
func (s *Server) handleDecline(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet {
reqIP := net.IP(options[dhcp4.OptionRequestedIPAddress])
log.Tracef("Message from client: Decline. IP: %s HW: %s",
reqIP, p.CHAddr())
return nil
} }
// Leases returns the list of current DHCP leases (thread-safe) // Leases returns the list of current DHCP leases (thread-safe)
@ -392,6 +427,15 @@ func (s *Server) Leases() []*Lease {
return result return result
} }
// Print information about the current leases
func (s *Server) printLeases() {
log.Tracef("Leases:")
for i, lease := range s.leases {
log.Tracef("Lease #%d: hwaddr %s, ip %s, expiry %s",
i, lease.HWAddr, lease.IP, lease.Expiry)
}
}
// Reset internal state // Reset internal state
func (s *Server) reset() { func (s *Server) reset() {
s.Lock() s.Lock()