333 lines
9.5 KiB
Bash
333 lines
9.5 KiB
Bash
#!/usr/bin/env bash
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#
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# detect_bridge.sh -- improved / robust argument handling
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#
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# Usage: sudo ./detect_bridge.sh <target-ip-or-hostname> [interface] [--mac-spoof]
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#
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set -euo pipefail
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IFS=$'\n\t'
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# defaults
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TARGET=""
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IFACE=""
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MAC_SPOOF=false
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# --- parse args robustly ---
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while [[ $# -gt 0 ]]; do
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case "$1" in
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--mac-spoof)
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MAC_SPOOF=true
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shift
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;;
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-i|--iface)
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if [[ -n "${2:-}" ]]; then
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IFACE="$2"
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shift 2
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else
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echo "Error: --iface requires an argument" >&2
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exit 2
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fi
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;;
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-h|--help)
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cat <<EOF
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Usage: sudo $0 <target-ip-or-hostname> [interface] [--mac-spoof]
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Options:
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--mac-spoof Enable optional MAC-spoof learning probe (may disrupt link).
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-i, --iface Specify interface to use (otherwise auto-detected).
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EOF
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exit 0
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;;
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-*)
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echo "Unknown option: $1" >&2
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exit 2
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;;
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*)
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if [[ -z "$TARGET" ]]; then
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TARGET="$1"
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else
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# allow second positional to be iface for compatibility
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if [[ -z "$IFACE" ]]; then
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IFACE="$1"
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else
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echo "Ignoring extra argument: $1" >&2
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fi
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fi
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shift
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;;
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esac
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done
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if [[ -z "$TARGET" ]]; then
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echo "Error: target IP or hostname required." >&2
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echo "Usage: sudo $0 <target-ip-or-hostname> [interface] [--mac-spoof]" >&2
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exit 2
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fi
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# helper: detect default interface to reach target
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detect_iface() {
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if [[ -n "$IFACE" ]]; then
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printf '%s\n' "$IFACE"
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return 0
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fi
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if route_info=$(ip route get "$TARGET" 2>/dev/null); then
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dev=$(echo "$route_info" | awk '{for(i=1;i<=NF;i++){if($i=="dev"){print $(i+1);exit}}}')
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if [[ -n "$dev" ]]; then
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printf '%s\n' "$dev"
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return 0
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fi
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fi
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# fallback: first non-loopback up interface
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for dev in $(ls /sys/class/net); do
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if [[ "$dev" != "lo" ]] && [[ -f "/sys/class/net/$dev/operstate" ]] && grep -q "up" "/sys/class/net/$dev/operstate"; then
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printf '%s\n' "$dev"
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return 0
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fi
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done
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printf 'eth0\n'
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}
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# ensure ip exists
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if ! command -v ip >/dev/null 2>&1; then
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echo "This script requires 'ip' (iproute2). Aborting." >&2
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exit 1
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fi
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IFACE=$(detect_iface)
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echo "Target: $TARGET"
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echo "Interface: $IFACE"
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echo
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# resolve target IP
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if [[ "$TARGET" =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
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TARGET_IP="$TARGET"
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else
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TARGET_IP=$(getent hosts "$TARGET" | awk '{print $1}' | head -n1 || true)
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if [[ -z "$TARGET_IP" ]]; then
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echo "Failed to resolve target '$TARGET'." >&2
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exit 1
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fi
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fi
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echo "Resolved target IP: $TARGET_IP"
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echo
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# check required commands
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REQ_CMDS=(ip ping awk grep sed date)
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for c in "${REQ_CMDS[@]}"; do
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if ! command -v "$c" >/dev/null 2>&1; then
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echo "Missing required command: $c" >&2
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exit 1
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fi
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done
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# optional commands
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HAS_TCPDUMP=false
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HAS_ETHTOOL=false
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HAS_ARPING=false
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HAS_LLDPC=false
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HAS_TRACEROUTE=false
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if command -v tcpdump >/dev/null 2>&1; then HAS_TCPDUMP=true; fi
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if command -v ethtool >/dev/null 2>&1; then HAS_ETHTOOL=true; fi
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if command -v arping >/dev/null 2>&1; then HAS_ARPING=true; fi
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if command -v lldpctl >/dev/null 2>&1; then HAS_LLDPC=true; fi
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if command -v traceroute >/dev/null 2>&1; then HAS_TRACEROUTE=true; fi
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echo "Tool availability:"
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echo " tcpdump: $HAS_TCPDUMP"
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echo " ethtool: $HAS_ETHTOOL"
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echo " arping: $HAS_ARPING"
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echo " lldpctl: $HAS_LLDPC"
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echo " traceroute: $HAS_TRACEROUTE"
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echo
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run_header() {
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echo
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echo "===== $1 ====="
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}
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# 1) interface->master check
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run_header "Interface master / bridge hint (ip link)"
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ip link show dev "$IFACE" | sed -n '1,4p' || true
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master=$(ip link show dev "$IFACE" 2>/dev/null | tr '\n' ' ' | sed 's/.*master \([^ ]*\).*/\1/;t;d' || true)
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if [[ -n "$master" ]]; then
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echo "Interface reports master: $master -> This interface is enslaved to a bridge on this host (local bridge)."
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else
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echo "No 'master' shown; interface is not a local bridge slave (or not reported)."
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fi
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# 2) check /sys/class/net/<if>/bridge
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run_header "Check local bridge sysfs"
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if [[ -d "/sys/class/net/$IFACE/bridge" ]]; then
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echo "/sys/class/net/$IFACE/bridge exists -> this host has a bridge device attached to $IFACE (local)."
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else
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echo "No /sys/class/net/$IFACE/bridge -> local host is not the bridge owner for this interface."
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fi
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# 3) LLDP via lldpctl
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if $HAS_LLDPC; then
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run_header "LLDP via lldpctl"
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sudo lldpctl -f keyvalue "$IFACE" 2>/dev/null || echo "lldpctl produced no output or isn't running for $IFACE."
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else
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run_header "LLDP: lldpctl not installed"
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echo "lldpctl not installed. Install lldpd and run lldpctl to try LLDP discovery."
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fi
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# 4) passive capture for STP/LLDP (tcpdump)
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if $HAS_TCPDUMP; then
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run_header "Passive capture: look for STP BPDUs and LLDP frames (tcpdump, 6s capture)"
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TMPPCAP=$(mktemp /tmp/detect_bridge_pcap.XXXX.pcap)
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trap 'rm -f "$TMPPCAP"' EXIT
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sudo timeout 6 tcpdump -i "$IFACE" -s 128 -w "$TMPPCAP" "ether dst 01:80:c2:00:00:00 or ether proto 0x88cc or ether multicast" >/dev/null 2>&1 || true
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if [[ -s "$TMPPCAP" ]]; then
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echo "Captured packets; summary:"
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sudo tcpdump -n -r "$TMPPCAP" -e | sed -n '1,50p' || true
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if sudo tcpdump -n -r "$TMPPCAP" -e | grep -i "stp\|bpdu" >/dev/null 2>&1; then
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echo "-> STP/BPDU frames observed."
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fi
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if sudo tcpdump -n -r "$TMPPCAP" -e | grep -i "LLDP" >/dev/null 2>&1; then
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echo "-> LLDP frames observed."
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fi
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else
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echo "No control frames captured in 6s capture."
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fi
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rm -f "$TMPPCAP" || true
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trap - EXIT
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else
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run_header "Passive capture: tcpdump not available"
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echo "tcpdump missing. Install tcpdump and re-run to capture control frames (STP/LLDP)."
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fi
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# 5) ethtool
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if $HAS_ETHTOOL; then
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run_header "ethtool: link/partner info"
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sudo ethtool "$IFACE" || true
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sudo ethtool -a "$IFACE" 2>/dev/null || true
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sudo ethtool -S "$IFACE" 2>/dev/null || true
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else
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run_header "ethtool not available"
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fi
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# 6) ARP / neighbor and MAC lookup
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run_header "ARP table and MAC OUI"
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ip neigh show to "$TARGET_IP" | sed -n '1,50p' || true
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arp_mac=$(ip neigh show to "$TARGET_IP" | awk '{print $5; exit}' || true)
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if [[ -n "$arp_mac" ]]; then
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echo "Observed MAC for $TARGET_IP: $arp_mac"
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else
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echo "No ARP entry yet."
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fi
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# 7) arping
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if $HAS_ARPING; then
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run_header "arping: 5 probes to target"
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sudo timeout 6 arping -c 5 -I "$IFACE" "$TARGET_IP" || true
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fi
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# 8) ping micro-latency test
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run_header "ping micro-latency test: 100 pings, 10ms interval"
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if ping -c 1 "$TARGET_IP" >/dev/null 2>&1; then
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ping -c 100 -i 0.01 "$TARGET_IP" | tail -n 5 || true
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stats=$(ping -c 10 -i 0.01 -q "$TARGET_IP" 2>/dev/null | tail -n1 || true)
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echo "Ping summary: $stats"
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else
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echo "Target is not responding to ICMP, skipping ping test."
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fi
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# 9) traceroute
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if $HAS_TRACEROUTE; then
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run_header "traceroute to target"
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traceroute -n -w 1 -q 1 "$TARGET_IP" || true
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fi
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# 10) passive multicast sniff
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if $HAS_TCPDUMP; then
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run_header "Passive: sniff for LLDP/stp multicast (4s)"
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TMPLOG=$(mktemp /tmp/detect_bridge_log.XXXX.txt)
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sudo timeout 4 tcpdump -i "$IFACE" -s 160 -l -n 'ether multicast' 2>/dev/null | sed -n '1,200p' >"$TMPLOG" || true
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if [[ -s "$TMPLOG" ]]; then
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sed -n '1,50p' "$TMPLOG"
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else
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echo "No multicast control frames in short 4s sniff."
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fi
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rm -f "$TMPLOG" || true
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fi
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# 11) gentle ARP burst
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run_header "Broadcast/ARP test (gentle)"
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if $HAS_ARPING; then
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sudo timeout 4 arping -c 3 -I "$IFACE" "$TARGET_IP" >/dev/null 2>&1 || true
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else
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echo "arping not available -> skipping."
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fi
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# 12) Optional MAC-spoof test (prompt/confirm)
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if [ "$MAC_SPOOF" = true ]; then
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echo
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echo "***** MAC SPOOF TEST ENABLED *****"
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read -r -p "This may disrupt link. Continue? (y/N) " yn
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if [[ "$yn" =~ ^[Yy]$ ]]; then
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orig_mac=$(cat "/sys/class/net/$IFACE/address")
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rand_mac=$(printf '02:%02x:%02x:%02x:%02x:%02x\n' $((RANDOM%256)) $((RANDOM%256)) $((RANDOM%256)) $((RANDOM%256)) $((RANDOM%256)))
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echo "Original MAC: $orig_mac"
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echo "Changing $IFACE to $rand_mac"
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sudo ip link set dev "$IFACE" down
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sudo ip link set dev "$IFACE" address "$rand_mac"
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sudo ip link set dev "$IFACE" up
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ping -c 5 "$TARGET_IP" || true
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echo "Restoring original MAC"
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sudo ip link set dev "$IFACE" down
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sudo ip link set dev "$IFACE" address "$orig_mac"
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sudo ip link set dev "$IFACE" up
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echo "MAC restored to $orig_mac"
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else
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echo "Skipping MAC spoof test."
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fi
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else
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echo "(MAC spoof test disabled. To enable, re-run with --mac-spoof.)"
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fi
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# 13) Synthesis (simple)
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run_header "Synthesis (brief)"
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score=0
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notes=()
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if $HAS_TCPDUMP && sudo timeout 1 tcpdump -n -c 1 -i "$IFACE" 'ether dst 01:80:c2:00:00:00' >/dev/null 2>&1; then
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score=$((score+40))
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notes+=("STP/BPDU observed -> likely bridge/switch.")
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fi
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if $HAS_TCPDUMP && sudo timeout 1 tcpdump -n -c 1 -i "$IFACE" 'ether proto 0x88cc' >/dev/null 2>&1; then
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score=$((score+40))
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notes+=("LLDP observed -> neighbor advertising.")
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elif $HAS_LLDPC; then
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if sudo lldpctl "$IFACE" 2>/dev/null | grep -q .; then
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score=$((score+40))
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notes+=("lldpctl shows LLDP neighbor on $IFACE.")
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fi
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fi
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if [[ -n "$master" ]]; then
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score=$((score+30))
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notes+=("Interface master indicates local bridge ($master).")
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fi
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if [[ -n "$arp_mac" ]]; then
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score=$((score+2))
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notes+=("ARP resolved target MAC ($arp_mac).")
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fi
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if [[ "$score" -gt 100 ]]; then score=100; fi
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echo "Score: $score / 100"
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for n in "${notes[@]}"; do
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echo " - $n"
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done
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if [[ "$score" -ge 70 ]]; then
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echo "Conclusion: HIGH confidence of a bridge/switch between hosts."
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elif [[ "$score" -ge 35 ]]; then
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echo "Conclusion: MEDIUM confidence."
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else
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echo "Conclusion: LOW confidence."
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fi
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echo
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echo "Done." |