From e92a09e1196194cb89ec5132ade635316b00de4e Mon Sep 17 00:00:00 2001
From: Ian Gulliver <git@flamingcow.io>
Date: Sat, 17 Jan 2026 21:12:21 -0800
Subject: [PATCH] add debug flags for arp, lldp, and snmp discovery

---
 arp.go               |  4 ++++
 cmd/tendrils/main.go |  6 ++++++
 lldp.go              |  4 ++++
 snmp.go              | 12 ++++++++++++
 tendrils.go          |  3 +++
 5 files changed, 29 insertions(+)

diff --git a/arp.go b/arp.go
index 983fec9..4a3b64b 100644
--- a/arp.go
+++ b/arp.go
@@ -44,6 +44,10 @@ func (t *Tendrils) readARPTable() {
 			continue
 		}
 
+		if t.DebugARP {
+			log.Printf("[arp] %s: ip=%s mac=%s", entry.iface, entry.ip, entry.mac)
+		}
+
 		t.nodes.Update([]net.IP{entry.ip}, []net.HardwareAddr{entry.mac}, entry.iface, "", "arp")
 	}
 }
diff --git a/cmd/tendrils/main.go b/cmd/tendrils/main.go
index e978450..802c3e6 100644
--- a/cmd/tendrils/main.go
+++ b/cmd/tendrils/main.go
@@ -13,6 +13,9 @@ func main() {
 	noSNMP := flag.Bool("no-snmp", false, "disable SNMP discovery")
 	logTree := flag.Bool("log-tree", false, "log full tree on changes")
 	logReasons := flag.Bool("log-reasons", false, "log addition reasons")
+	debugARP := flag.Bool("debug-arp", false, "debug ARP discovery")
+	debugLLDP := flag.Bool("debug-lldp", false, "debug LLDP discovery")
+	debugSNMP := flag.Bool("debug-snmp", false, "debug SNMP discovery")
 	flag.Parse()
 
 	t := tendrils.New()
@@ -22,5 +25,8 @@ func main() {
 	t.DisableSNMP = *noSNMP
 	t.LogTree = *logTree
 	t.LogReasons = *logReasons
+	t.DebugARP = *debugARP
+	t.DebugLLDP = *debugLLDP
+	t.DebugSNMP = *debugSNMP
 	t.Run()
 }
diff --git a/lldp.go b/lldp.go
index 09e5045..b4ab22f 100644
--- a/lldp.go
+++ b/lldp.go
@@ -64,6 +64,10 @@ func (t *Tendrils) handleLLDPPacket(ifaceName string, packet gopacket.Packet) {
 				}
 			}
 
+			if t.DebugLLDP {
+				log.Printf("[lldp] %s: mac=%s port=%s name=%s", ifaceName, mac, childPort, systemName)
+			}
+
 			t.nodes.Update(nil, []net.HardwareAddr{mac}, ifaceName, childPort, "lldp")
 
 			if systemName != "" {
diff --git a/snmp.go b/snmp.go
index 08849df..e18d917 100644
--- a/snmp.go
+++ b/snmp.go
@@ -3,6 +3,7 @@ package tendrils
 import (
 	"context"
 	"fmt"
+	"log"
 	"net"
 	"regexp"
 	"strings"
@@ -109,10 +110,17 @@ func (t *Tendrils) querySwitches() {
 func (t *Tendrils) querySNMPDevice(ip net.IP) {
 	snmp, err := t.connectSNMP(ip)
 	if err != nil {
+		if t.DebugSNMP {
+			log.Printf("[snmp] %s: connect failed: %v", ip, err)
+		}
 		return
 	}
 	defer snmp.Conn.Close()
 
+	if t.DebugSNMP {
+		log.Printf("[snmp] %s: connected", ip)
+	}
+
 	t.querySysName(snmp, ip)
 	t.queryBridgeMIB(snmp, ip)
 }
@@ -219,6 +227,10 @@ func (t *Tendrils) queryBridgeMIB(snmp *gosnmp.GoSNMP, deviceIP net.IP) {
 			}
 		}
 
+		if t.DebugSNMP {
+			log.Printf("[snmp] %s: mac=%s port=%s", deviceIP, mac, ifName)
+		}
+
 		if addToParent {
 			t.nodes.Update([]net.IP{deviceIP}, []net.HardwareAddr{mac}, "", "", "snmp")
 		} else {
diff --git a/tendrils.go b/tendrils.go
index 95b127d..2a75254 100644
--- a/tendrils.go
+++ b/tendrils.go
@@ -18,6 +18,9 @@ type Tendrils struct {
 	DisableSNMP bool
 	LogTree     bool
 	LogReasons  bool
+	DebugARP    bool
+	DebugLLDP   bool
+	DebugSNMP   bool
 }
 
 func New() *Tendrils {