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dhcpd: impl rfc 2131 for req
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@EugeneOne1
EugeneOne1 committed Aug 30, 2022
1 parent 2348b8f commit 20de395
Showing 1 changed file with 148 additions and 29 deletions.
177 changes: 148 additions & 29 deletions internal/dhcpd/v4.go
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Original file line number Diff line number Diff line change
Expand Up @@ -94,9 +94,6 @@ func (s *v4Server) validHostnameForClient(cliHostname string, ip net.IP) (hostna

if hostname == "" {
hostname = aghnet.GenerateHostname(ip)
} else if s.leaseHosts.Has(hostname) {
log.Info("dhcpv4: hostname %q already exists", hostname)
hostname = aghnet.GenerateHostname(ip)
}

err = netutil.ValidateDomainName(hostname)
Expand Down Expand Up @@ -545,7 +542,9 @@ func (s *v4Server) reserveLease(mac net.HardwareAddr) (l *Lease, err error) {
return l, nil
}

func (s *v4Server) commitLease(l *Lease) {
// commitLease refreshes the l's values. A non-empty prevName will be removed
// from the known hostnames registry.
func (s *v4Server) commitLease(l *Lease, prevName string) {
l.Expiry = time.Now().Add(s.conf.leaseTime)

func() {
Expand All @@ -554,6 +553,9 @@ func (s *v4Server) commitLease(l *Lease) {

s.conf.notify(LeaseChangedDBStore)

if prevName != "" && prevName != l.Hostname {
s.leaseHosts.Del(prevName)
}
if l.Hostname != "" {
s.leaseHosts.Add(l.Hostname)
}
Expand Down Expand Up @@ -664,59 +666,176 @@ func (s *v4Server) checkLease(mac net.HardwareAddr, ip net.IP) (lease *Lease, mi
return nil, false
}

// processRequest is the handler for the DHCP Request request.
func (s *v4Server) processRequest(req, resp *dhcpv4.DHCPv4) (lease *Lease, needsReply bool) {
// setHostname sets the unique hostname, either requested or generated, to the
// lease and to the DHCP response if the one is requested. It returns the
// previous value of the lease's hostname.
func (s *v4Server) setHostname(req, resp *dhcpv4.DHCPv4, lease *Lease) (prev string) {
prev = lease.Hostname

hostname := req.HostName()
requested := hostname != "" || req.ParameterRequestList().Has(dhcpv4.OptionHostName)
hostname = s.validHostnameForClient(hostname, lease.IP)

if s.leaseHosts.Has(hostname) {
log.Info("dhcpv4: hostname %q already exists", hostname)

if prev == "" {
// The lease is just allocated due to DHCPDISCOVER.
hostname = aghnet.GenerateHostname(lease.IP)
} else {
hostname = prev
}
}
if lease.Hostname != hostname {
lease.Hostname = hostname
}

if requested {
resp.UpdateOption(dhcpv4.OptHostName(lease.Hostname))
}

return prev
}

// processSelecting handles the DHCPREQUEST generated during SELECTING state.
func (s *v4Server) processSelecting(req *dhcpv4.DHCPv4, sid net.IP) (l *Lease, needsReply bool) {
// Client inserts the address of the selected server in 'server identifier',
// 'ciaddr' MUST be zero.
mac := req.ClientHWAddr
// TODO(e.burkov): The IP address can only be requested in DHCPDISCOVER
// message.
reqIP := req.RequestedIPAddress()
if reqIP == nil {
reqIP = req.ClientIPAddr
if !sid.Equal(s.conf.dnsIPAddrs[0]) {
log.Debug("dhcpv4: bad server identifier in req msg for %s: %s", mac, sid)

return nil, false
} else if ciaddr := req.ClientIPAddr; ciaddr != nil && !ciaddr.IsUnspecified() {
log.Debug("dhcpv4: non-zero ciaddr in selecting req msg for %s", mac)

return nil, false
}

sid := req.ServerIdentifier()
if len(sid) != 0 && !sid.Equal(s.conf.dnsIPAddrs[0]) {
log.Debug("dhcpv4: bad OptionServerIdentifier in req msg for %s", mac)
// 'requested IP address' MUST be filled in with the yiaddr value from the
// chosen DHCPOFFER.
reqIP := req.RequestedIPAddress()
if ip4 := reqIP.To4(); ip4 == nil {
log.Debug("dhcpv4: bad requested address in req msg for %s: %s", mac, reqIP)

return nil, false
}

var mismatch bool
if l, mismatch = s.checkLease(mac, reqIP); mismatch {
return nil, true
} else if l == nil {
log.Debug("dhcpv4: no reserved lease for %s", mac)
}

return l, true
}

// processInitReboot handles the DHCPREQUEST generated during INIT-REBOOT state.
func (s *v4Server) processInitReboot(req *dhcpv4.DHCPv4, reqIP net.IP) (l *Lease, needsReply bool) {
mac := req.ClientHWAddr

// 'requested IP address' option MUST be filled in with client's notion of
// its previously assigned address.
if ip4 := reqIP.To4(); ip4 == nil {
log.Debug("dhcpv4: bad OptionRequestedIPAddress in req msg for %s", mac)
log.Debug("dhcpv4: bad requested address in req msg for %s: %s", mac, reqIP)

return nil, false
}

// 'ciaddr' MUST be zero. The client is seeking to verify a previously
// allocated, cached configuration.
if ciaddr := req.ClientIPAddr; ciaddr != nil && !ciaddr.IsUnspecified() {
log.Debug("dhcpv4: non-zero ciaddr in init-reboot req msg for %s", mac)

return nil, false
}

if !s.conf.subnet.Contains(reqIP) {
// If the DHCP server detects that the client is on the wrong net then
// the server SHOULD send a DHCPNAK message to the client.
log.Debug("dhcpv4: wrong subnet in init-reboot req msg for %s: %s", mac, reqIP)

return nil, true
}

var mismatch bool
if lease, mismatch = s.checkLease(mac, reqIP); mismatch {
if l, mismatch = s.checkLease(mac, reqIP); mismatch {
return nil, true
} else if l == nil {
// If the DHCP server has no record of this client, then it MUST remain
// silent, and MAY output a warning to the network administrator.
log.Debug("dhcpv4: no existing lease for %s", mac)

return nil, false
}

if lease == nil {
log.Debug("dhcpv4: no reserved lease for %s", mac)
return l, true
}

// processRenew handles the DHCPREQUEST generated during RENEWING or REBINDING
// state.
func (s *v4Server) processRenew(req *dhcpv4.DHCPv4) (l *Lease, needsReply bool) {
mac := req.ClientHWAddr

// 'ciaddr' MUST be filled in with client's IP address.
ciaddr := req.ClientIPAddr
if ciaddr == nil || ciaddr.IsUnspecified() || ciaddr.To4() == nil {
log.Debug("dhcpv4: bad ciaddr in renew req msg for %s", mac)

return nil, false
}

var mismatch bool
if l, mismatch = s.checkLease(mac, ciaddr); mismatch {
return nil, true
} else if l == nil {
// If the DHCP server has no record of this client, then it MUST remain
// silent, and MAY output a warning to the network administrator.
log.Debug("dhcpv4: no existing lease for %s", mac)

return nil, false
}

if !lease.IsStatic() {
cliHostname := req.HostName()
hostname := s.validHostnameForClient(cliHostname, reqIP)
if lease.Hostname != hostname {
lease.Hostname = hostname
resp.UpdateOption(dhcpv4.OptHostName(hostname))
}
return l, true
}

// processRequest is the handler for a DHCPREQUEST message.
//
// See https://datatracker.ietf.org/doc/html/rfc2131#section-4.3.2.
func (s *v4Server) processRequest(req, resp *dhcpv4.DHCPv4) (l *Lease, needsReply bool) {
if sid := req.ServerIdentifier(); sid != nil && !sid.IsUnspecified() {
// If the DHCPREQUEST message contains a 'server identifier' option, the
// message is in response to a DHCPOFFER message. Otherwise, the
// message is a request to verify or extend an existing lease.
l, needsReply = s.processSelecting(req, sid)
} else if reqIP := req.RequestedIPAddress(); reqIP != nil && !reqIP.IsUnspecified() {
// The DHCPREQUEST generated during INIT-REBOOT state must not contain a
// 'requested IP address' option.
l, needsReply = s.processInitReboot(req, reqIP)
} else {
// 'server identifier' MUST NOT be filled in, 'requested IP address'
// option MUST NOT be filled in.
l, needsReply = s.processRenew(req)
}

if l == nil {
return nil, needsReply
}

s.commitLease(lease)
} else if lease.Hostname != "" {
if !l.IsStatic() {
prev := s.setHostname(req, resp, l)
s.commitLease(l, prev)
} else if l.Hostname != "" {
// TODO(e.burkov): This option is used to update the server's DNS
// mapping. The option should only be answered when it has been
// requested.
resp.UpdateOption(OptionFQDN(lease.Hostname))
resp.UpdateOption(OptionFQDN(l.Hostname))
}

resp.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeAck))

return lease, true
return l, needsReply
}

// processRequest is the handler for the DHCP Decline request.
Expand Down

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