From 92cf7c1aca63afa3c16a6e6c327772646ac1781e Mon Sep 17 00:00:00 2001
From: Simon Zolin <s.zolin@adguard.com>
Date: Wed, 6 Mar 2019 15:13:27 +0300
Subject: [PATCH] * dhcp: refactor
---
dhcpd/dhcpd.go | 144 ++++++++++++++++++++++++++++++++-----------------
1 file changed, 94 insertions(+), 50 deletions(-)
diff --git a/dhcpd/dhcpd.go b/dhcpd/dhcpd.go
index d0c61934..f7d99d36 100644
--- a/dhcpd/dhcpd.go
+++ b/dhcpd/dhcpd.go
@@ -4,6 +4,7 @@ import (
"bytes"
"fmt"
"net"
+ "strings"
"sync"
"time"
@@ -59,6 +60,16 @@ type Server struct {
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.
// 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 {
@@ -69,6 +80,7 @@ func (s *Server) Start(config *ServerConfig) error {
iface, err := net.InterfaceByName(s.InterfaceName)
if err != nil {
s.closeConn() // in case it was already started
+ printInterfaces()
return wrapErrPrint(err, "Couldn't find interface by name %s", s.InterfaceName)
}
@@ -189,6 +201,7 @@ func (s *Server) closeConn() error {
return err
}
+// Reserve a lease for the client
func (s *Server) reserveLease(p dhcp4.Packet) (*Lease, error) {
// WARNING: do not remove copy()
// 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()
hwaddr := make(net.HardwareAddr, len(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
log.Tracef("Lease not found for %s: creating new one", hwaddr)
ip, err := s.findFreeIP(hwaddr)
@@ -216,7 +224,8 @@ func (s *Server) reserveLease(p dhcp4.Packet) (*Lease, error) {
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()
for i := range s.leases {
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) {
// 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
}
foundIP = newIP
@@ -280,12 +288,7 @@ func (s *Server) unreserveIP(ip net.IP) {
// ServeDHCP handles an incoming DHCP request
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)
-
- 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)
- }
+ s.printLeases()
switch msgType {
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)
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
- 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
- log.Tracef("Got from client: Inform")
+ return s.handleInform(p, options)
// from server -- ignore those but enumerate just in case
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
- 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
- log.Printf("DHCP: received message from another server: NAK")
+ log.Printf("DHCP: received message from %s: NAK", p.CHAddr())
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
@@ -324,12 +327,23 @@ func (s *Server) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dh
func (s *Server) handleDiscover(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet {
// find a lease, but don't update lease time
+ var lease *Lease
+ var err error
- lease, err := s.reserveLease(p)
- if err != nil {
- log.Tracef("Couldn't find free lease: %s", err)
- // couldn't find lease, don't respond
- return nil
+ 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 {
+ log.Error("Couldn't find free lease: %s", err)
+ return nil
+ }
+
+ break
}
opt := s.leaseOptions.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList])
@@ -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 {
+ 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]
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)
return nil // Message not for this dhcp server
}
- reqIP := net.IP(options[dhcp4.OptionRequestedIPAddress])
if reqIP == nil {
reqIP = p.CIAddr()
- }
- if reqIP.To4() == nil {
- log.Tracef("Replying with NAK: request IP isn't valid IPv4: %s", reqIP)
+ } else if reqIP == nil || reqIP.To4() == nil {
+ log.Tracef("Requested IP isn't a valid IPv4: %s", reqIP)
return dhcp4.ReplyPacket(p, dhcp4.NAK, s.ipnet.IP, nil, 0, nil)
}
- if reqIP.Equal(net.IPv4zero) {
- log.Tracef("Replying with NAK: request IP is 0.0.0.0")
+ lease = s.findLease(p)
+ if lease == nil {
+ lease, err = s.reserveLease(p)
+ if err != nil {
+ log.Tracef("Couldn't find free lease: %s", err)
+ // couldn't find lease, don't respond
+ 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)
}
- log.Tracef("requested IP is %s", reqIP)
- lease, err := s.reserveLease(p)
- if err != nil {
- log.Tracef("Couldn't find free lease: %s", err)
- // couldn't find lease, don't respond
- return nil
- }
+ lease.Expiry = time.Now().Add(s.leaseTime)
+ log.Tracef("Replying with ACK. IP: %s HW: %s Expire: %s",
+ lease.IP, lease.HWAddr, lease.Expiry)
+ opt := s.leaseOptions.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList])
+ return dhcp4.ReplyPacket(p, dhcp4.ACK, s.ipnet.IP, lease.IP, s.leaseTime, opt)
+}
- if lease.IP.Equal(reqIP) {
- // IP matches lease IP, nothing else to do
- 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())
- opt := s.leaseOptions.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList])
- 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 {
+ log.Tracef("Message from client: Inform. IP: %s HW: %s",
+ p.CIAddr(), p.CHAddr())
- //
- // requested IP different from lease
- //
+ return nil
+}
- log.Tracef("lease IP is different from requested IP: %s vs %s", lease.IP, reqIP)
- 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)
@@ -392,6 +427,15 @@ func (s *Server) Leases() []*Lease {
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
func (s *Server) reset() {
s.Lock()