all: include client IP if ctrld is dnsmasq upstream

So ctrld can record the raw/original client IP instead of looking up
from MAC to IP, which may not the right choice in some network setup
like using wireguard/vpn on Merlin router.

internal/clientinfo/arp.go

@@ -33,6 +33,9 @@ func (a *arpDiscover) String() string {
 }
 
 func (a *arpDiscover) List() []string {
+	if a == nil {
+		return nil
+	}
 	var ips []string
 	a.ip.Range(func(key, value any) bool {
 		ips = append(ips, value.(string))

internal/clientinfo/client_info.go

@@ -74,6 +74,7 @@ type Table struct {
 	ptr    *ptrDiscover
 	mdns   *mdns
 	hf     *hostsFile
+	vpn    *vpn
 	cfg    *ctrld.Config
 	quitCh chan struct{}
 	selfIP string
@@ -117,6 +118,7 @@ func (t *Table) Init() {
 }
 
 func (t *Table) init() {
+	// Custom client ID presents, use it as the only source.
 	if _, clientID := controld.ParseRawUID(t.cdUID); clientID != "" {
 		ctrld.ProxyLogger.Load().Debug().Msg("start self discovery")
 		t.dhcp = &dhcp{selfIP: t.selfIP}
@@ -126,6 +128,11 @@ func (t *Table) init() {
 		t.hostnameResolvers = append(t.hostnameResolvers, t.dhcp)
 		return
 	}
+
+	// Otherwise, process all possible sources in order, that means
+	// the first result of IP/MAC/Hostname lookup will be used.
+	//
+	// Merlin custom clients.
 	if t.discoverDHCP() || t.discoverARP() {
 		t.merlin = &merlinDiscover{}
 		if err := t.merlin.refresh(); err != nil {
@@ -135,6 +142,7 @@ func (t *Table) init() {
 			t.refreshers = append(t.refreshers, t.merlin)
 		}
 	}
+	// Hosts file mapping.
 	if t.discoverHosts() {
 		t.hf = &hostsFile{}
 		ctrld.ProxyLogger.Load().Debug().Msg("start hosts file discovery")
@@ -146,6 +154,7 @@ func (t *Table) init() {
 		}
 		go t.hf.watchChanges()
 	}
+	// DHCP lease files.
 	if t.discoverDHCP() {
 		t.dhcp = &dhcp{selfIP: t.selfIP}
 		ctrld.ProxyLogger.Load().Debug().Msg("start dhcp discovery")
@@ -158,6 +167,7 @@ func (t *Table) init() {
 		}
 		go t.dhcp.watchChanges()
 	}
+	// ARP table.
 	if t.discoverARP() {
 		t.arp = &arpDiscover{}
 		ctrld.ProxyLogger.Load().Debug().Msg("start arp discovery")
@@ -169,6 +179,7 @@ func (t *Table) init() {
 			t.refreshers = append(t.refreshers, t.arp)
 		}
 	}
+	// PTR lookup.
 	if t.discoverPTR() {
 		t.ptr = &ptrDiscover{resolver: ctrld.NewPrivateResolver()}
 		ctrld.ProxyLogger.Load().Debug().Msg("start ptr discovery")
@@ -179,6 +190,7 @@ func (t *Table) init() {
 			t.refreshers = append(t.refreshers, t.ptr)
 		}
 	}
+	// mdns.
 	if t.discoverMDNS() {
 		t.mdns = &mdns{}
 		ctrld.ProxyLogger.Load().Debug().Msg("start mdns discovery")
@@ -188,6 +200,11 @@ func (t *Table) init() {
 			t.hostnameResolvers = append(t.hostnameResolvers, t.mdns)
 		}
 	}
+	// VPN clients.
+	if t.discoverDHCP() || t.discoverARP() {
+		t.vpn = &vpn{}
+		t.hostnameResolvers = append(t.hostnameResolvers, t.vpn)
+	}
 }
 
 func (t *Table) LookupIP(mac string) string {
@@ -271,7 +288,7 @@ func (t *Table) ListClients() []*Client {
 		_ = r.refresh()
 	}
 	ipMap := make(map[string]*Client)
-	il := []ipLister{t.dhcp, t.arp, t.ptr, t.mdns}
+	il := []ipLister{t.dhcp, t.arp, t.ptr, t.mdns, t.vpn}
 	for _, ir := range il {
 		for _, ip := range ir.List() {
 			c, ok := ipMap[ip]
@@ -312,6 +329,15 @@ func (t *Table) ListClients() []*Client {
 	return clients
 }
 
+// StoreVPNClient stores client info for VPN clients.
+func (t *Table) StoreVPNClient(ci *ctrld.ClientInfo) {
+	if ci == nil || t.vpn == nil {
+		return
+	}
+	t.vpn.mac.Store(ci.IP, ci.Mac)
+	t.vpn.ip2name.Store(ci.IP, ci.Hostname)
+}
+
 func (t *Table) discoverDHCP() bool {
 	if t.cfg.Service.DiscoverDHCP == nil {
 		return true

internal/clientinfo/dhcp.go

@@ -119,6 +119,9 @@ func (d *dhcp) String() string {
 }
 
 func (d *dhcp) List() []string {
+	if d == nil {
+		return nil
+	}
 	var ips []string
 	d.ip.Range(func(key, value any) bool {
 		ips = append(ips, value.(string))

internal/clientinfo/mdns.go

@@ -48,6 +48,9 @@ func (m *mdns) String() string {
 }
 
 func (m *mdns) List() []string {
+	if m == nil {
+		return nil
+	}
 	var ips []string
 	m.name.Range(func(key, value any) bool {
 		ips = append(ips, key.(string))

internal/clientinfo/ptr_lookup.go

@@ -41,6 +41,9 @@ func (p *ptrDiscover) String() string {
 }
 
 func (p *ptrDiscover) List() []string {
+	if p == nil {
+		return nil
+	}
 	var ips []string
 	p.hostname.Range(func(key, value any) bool {
 		ips = append(ips, key.(string))

internal/clientinfo/vpn.go

@@ -0,0 +1,43 @@
+package clientinfo
+
+import (
+	"sync"
+)
+
+// vpn is the manager for VPN clients info.
+type vpn struct {
+	ip2name sync.Map // ip  => name
+	mac     sync.Map // ip  => mac
+}
+
+// LookupHostnameByIP returns hostname of the given VPN client ip.
+func (v *vpn) LookupHostnameByIP(ip string) string {
+	val, ok := v.ip2name.Load(ip)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+// LookupHostnameByMac always returns empty string.
+func (v *vpn) LookupHostnameByMac(mac string) string {
+	return ""
+}
+
+// String returns the string representation of vpn struct.
+func (v *vpn) String() string {
+	return "vpn"
+}
+
+// List lists all known VPN clients IP.
+func (v *vpn) List() []string {
+	if v == nil {
+		return nil
+	}
+	var ips []string
+	v.mac.Range(func(key, value any) bool {
+		ips = append(ips, key.(string))
+		return true
+	})
+	return ips
+}

internal/router/dnsmasq/dnsmasq.go

@@ -17,6 +17,7 @@ server={{ .IP }}#{{ .Port }}
 {{- end}}
 {{- if .SendClientInfo}}
 add-mac
+add-subnet=32,128
 {{- end}}
 `
 
@@ -39,7 +40,10 @@ if [ -n "$pid" ] && [ -f "/proc/${pid}/cmdline" ]; then
   pc_append "server={{ .IP }}#{{ .Port }}" "$config_file"
   {{- end}}
   {{- if .SendClientInfo}}
+  pc_delete "add-mac" "$config_file"
+  pc_delete "add-subnet" "$config_file"
   pc_append "add-mac" "$config_file"                # add client mac
+  pc_append "add-subnet=32,128" "$config_file"      # add client ip
   {{- end}}
   pc_delete "dnssec" "$config_file"                 # disable DNSSEC
   pc_delete "trust-anchor=" "$config_file"          # disable DNSSEC