findpeers.sh

#!/bin/bash

# findpeers.sh - Discover peers on your subnet when connected to WiFi
# Usage: ./findpeers.sh [options]

set -e

# Colors for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
CYAN='\033[0;36m'
NC='\033[0m' # No Color

# Default values
FAST_SCAN=false
VERBOSE=false
SHOW_HELP=false
PING_TIMEOUT=1
NMAP_AVAILABLE=false

# Check if nmap is available
if command -v nmap >/dev/null 2>&1; then
    NMAP_AVAILABLE=true
fi

show_help() {
    echo "findpeers.sh - Discover peers on your subnet when connected to WiFi"
    echo ""
    echo "Usage: $0 [options]"
    echo ""
    echo "Options:"
    echo "  -f, --fast      Fast scan (ping only, no port scanning)"
    echo "  -v, --verbose   Verbose output"
    echo "  -h, --help      Show this help message"
    echo ""
    echo "Requirements:"
    echo "  - Must be connected to WiFi"
    echo "  - nmap (optional, for enhanced scanning)"
    echo ""
    echo "Install nmap with: brew install nmap"
}

# Parse command line arguments
while [[ $# -gt 0 ]]; do
    case $1 in
        -f|--fast)
            FAST_SCAN=true
            shift
            ;;
        -v|--verbose)
            VERBOSE=true
            shift
            ;;
        -h|--help)
            show_help
            exit 0
            ;;
        *)
            echo "Unknown option: $1"
            show_help
            exit 1
            ;;
    esac
done

log_verbose() {
    if [[ "$VERBOSE" == true ]]; then
        echo -e "${CYAN}[VERBOSE]${NC} $1"
    fi
}

log_info() {
    echo -e "${BLUE}[INFO]${NC} $1"
}

log_success() {
    echo -e "${GREEN}[SUCCESS]${NC} $1"
}

log_warning() {
    echo -e "${YELLOW}[WARNING]${NC} $1"
}

log_error() {
    echo -e "${RED}[ERROR]${NC} $1"
}

# Check if connected to WiFi
check_wifi_connection() {
    log_verbose "Checking WiFi connection..."
    
    # Get WiFi interface name
    WIFI_INTERFACE=$(networksetup -listallhardwareports | awk '/Wi-Fi|AirPort/{getline; print $2}' | head -1)
    
    if [[ -z "$WIFI_INTERFACE" ]]; then
        log_error "No WiFi interface found"
        exit 1
    fi
    
    log_verbose "WiFi interface: $WIFI_INTERFACE"
    
    # Check if WiFi interface has an IP address (more reliable than networksetup)
    WIFI_IP=$(ifconfig "$WIFI_INTERFACE" | grep 'inet ' | awk '{print $2}' | head -1)
    
    if [[ -z "$WIFI_IP" ]]; then
        log_error "WiFi interface has no IP address. Please connect to a WiFi network first."
        exit 1
    fi
    
    # Try to get network name, but don't fail if we can't
    WIFI_STATUS=$(networksetup -getairportnetwork "$WIFI_INTERFACE" 2>/dev/null)
    
    if [[ "$WIFI_STATUS" == *"You are not associated with an AirPort network"* ]] || [[ -z "$WIFI_STATUS" ]]; then
        # Fallback: try to get SSID using airport command
        NETWORK_NAME=$(/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I 2>/dev/null | awk -F': ' '/^\s*SSID:/ {print $2}')
        if [[ -z "$NETWORK_NAME" ]]; then
            NETWORK_NAME="Unknown Network"
        fi
    else
        NETWORK_NAME=$(echo "$WIFI_STATUS" | sed 's/Current Wi-Fi Network: //')
    fi
    
    log_info "Connected to WiFi network: ${GREEN}$NETWORK_NAME${NC} (IP: ${GREEN}$WIFI_IP${NC})"
}

# Get local IP and subnet
get_network_info() {
    log_verbose "Getting network information..."
    
    # Get the active WiFi interface IP
    LOCAL_IP=$(ifconfig "$WIFI_INTERFACE" | grep 'inet ' | awk '{print $2}' | head -1)
    
    if [[ -z "$LOCAL_IP" ]]; then
        log_error "Could not determine local IP address"
        exit 1
    fi
    
    # Get subnet mask and convert to decimal if needed
    NETMASK_RAW=$(ifconfig "$WIFI_INTERFACE" | grep 'inet ' | awk '{print $4}' | head -1)
    
    # Convert hex netmask to dotted decimal
    if [[ "$NETMASK_RAW" == 0x* ]]; then
        # Convert hex to decimal, then to dotted notation
        NETMASK_HEX=${NETMASK_RAW#0x}
        NETMASK=$(printf "%d.%d.%d.%d\n" \
            $((0x${NETMASK_HEX:0:2})) \
            $((0x${NETMASK_HEX:2:2})) \
            $((0x${NETMASK_HEX:4:2})) \
            $((0x${NETMASK_HEX:6:2})))
    else
        NETMASK="$NETMASK_RAW"
    fi
    
    # Convert netmask to CIDR
    CIDR=$(echo "$NETMASK" | awk -F. '{
        cidr = 0
        for (i = 1; i <= 4; i++) {
            if ($i == 255) cidr += 8
            else if ($i == 254) cidr += 7
            else if ($i == 252) cidr += 6
            else if ($i == 248) cidr += 5
            else if ($i == 240) cidr += 4
            else if ($i == 224) cidr += 3
            else if ($i == 192) cidr += 2
            else if ($i == 128) cidr += 1
            else break
        }
        print cidr
    }')
    
    # Calculate network address (simplified for common cases)
    NETWORK=$(echo "$LOCAL_IP" | awk -F. -v cidr="$CIDR" '{
        if (cidr >= 24) {
            print $1 "." $2 "." $3 ".0"
        } else if (cidr >= 16) {
            print $1 "." $2 ".0.0"
        } else {
            print $1 ".0.0.0"
        }
    }')
    
    SUBNET="$NETWORK/$CIDR"
    
    log_info "Local IP: ${GREEN}$LOCAL_IP${NC}"
    log_info "Subnet: ${GREEN}$SUBNET${NC}"
    log_verbose "Netmask: $NETMASK"
}

# Ping scan function
ping_scan() {
    local subnet=$1
    local found_hosts=()
    
    log_info "Starting ping scan on $subnet..."
    
    # Extract network portion and CIDR
    local network=$(echo "$subnet" | cut -d'/' -f1)
    local cidr=$(echo "$subnet" | cut -d'/' -f2)
    
    # Calculate IP range based on common subnet sizes
    local base_ip=$(echo "$network" | cut -d'.' -f1-3)
    local start=1
    local end=254
    
    if [[ "$cidr" -eq 24 ]]; then
        # /24 network - scan .1 to .254
        start=1
        end=254
    elif [[ "$cidr" -eq 16 ]]; then
        # /16 network - limit scan to current /24 block for performance
        local last_octet=$(echo "$LOCAL_IP" | cut -d'.' -f4)
        log_warning "Large /16 network detected. Limiting scan to current /24 block for performance."
    fi
    
    log_verbose "Scanning IP range: $base_ip.$start to $base_ip.$end"
    
    # Parallel ping scan
    for i in $(seq $start $end); do
        {
            local ip="$base_ip.$i"
            if ping -c 1 -W $PING_TIMEOUT "$ip" >/dev/null 2>&1; then
                echo "$ip"
            fi
        } &
        
        # Limit concurrent processes
        if (( $(jobs -r | wc -l) >= 50 )); then
            wait
        fi
    done
    
    # Wait for all background jobs to complete
    wait
}

# Enhanced scan with nmap
nmap_scan() {
    local subnet=$1
    
    log_info "Starting enhanced nmap scan on $subnet..."
    log_verbose "Running: nmap -sn $subnet"
    
    # Host discovery scan
    nmap -sn "$subnet" 2>/dev/null | grep -E "Nmap scan report|MAC Address" | while read -r line; do
        if [[ "$line" == *"Nmap scan report"* ]]; then
            echo "$line" | awk '{print $5}'
        elif [[ "$line" == *"MAC Address"* ]] && [[ "$VERBOSE" == true ]]; then
            echo "  └─ $line"
        fi
    done
}

# Get hostname and additional info
get_host_info() {
    local ip=$1
    local hostname=""
    local mac=""
    local ports=""
    
    # Try to get hostname
    hostname=$(nslookup "$ip" 2>/dev/null | grep "name =" | awk '{print $4}' | sed 's/\.$//' | head -1)
    if [[ -z "$hostname" ]]; then
        hostname=$(dig +short -x "$ip" 2>/dev/null | sed 's/\.$//' | head -1)
    fi
    
    # Get MAC address if possible (only works for same subnet)
    mac=$(arp -n "$ip" 2>/dev/null | awk '{print $4}' | head -1)
    
    # Basic port scan if not fast mode and nmap available
    if [[ "$FAST_SCAN" == false ]] && [[ "$NMAP_AVAILABLE" == true ]]; then
        log_verbose "Port scanning $ip..."
        ports=$(nmap -F --open "$ip" 2>/dev/null | grep "/tcp" | head -3 | awk '{print $1}' | tr '\n' ',' | sed 's/,$//')
    fi
    
    # Format output
    local output="$ip"
    if [[ -n "$hostname" ]]; then
        output="$output (${GREEN}$hostname${NC})"
    fi
    if [[ -n "$mac" ]] && [[ "$mac" != "(incomplete)" ]]; then
        output="$output [MAC: $mac]"
    fi
    if [[ -n "$ports" ]]; then
        output="$output [Ports: $ports]"
    fi
    
    echo -e "  $output"
}

# Main scanning function
scan_network() {
    local hosts=()
    
    echo ""
    log_info "Scanning for active hosts..."
    echo ""
    
    if [[ "$NMAP_AVAILABLE" == true ]] && [[ "$FAST_SCAN" == false ]]; then
        log_verbose "Using nmap for enhanced scanning"
        while IFS= read -r host; do
            if [[ -n "$host" ]]; then
                hosts+=("$host")
            fi
        done < <(nmap_scan "$SUBNET")
    else
        if [[ "$NMAP_AVAILABLE" == false ]]; then
            log_warning "nmap not found. Using basic ping scan. Install with: brew install nmap"
        fi
        log_verbose "Using ping scan"
        while IFS= read -r host; do
            if [[ -n "$host" ]]; then
                hosts+=("$host")
            fi
        done < <(ping_scan "$SUBNET")
    fi
    
    # Sort hosts by IP
    IFS=$'\n' hosts=($(sort -V <<<"${hosts[*]}"))
    
    echo ""
    if [[ ${#hosts[@]} -eq 0 ]]; then
        log_warning "No active hosts found on the network"
        return
    fi
    
    log_success "Found ${#hosts[@]} active host(s):"
    echo ""
    
    # Get detailed info for each host
    for host in "${hosts[@]}"; do
        if [[ "$host" == "$LOCAL_IP" ]]; then
            echo -e "  $host (${YELLOW}this device${NC})"
        else
            get_host_info "$host"
        fi
    done
    
    echo ""
}

# Print summary
print_summary() {
    echo ""
    echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
    echo ""
    log_info "Scan completed!"
    echo ""
    if [[ "$NMAP_AVAILABLE" == false ]]; then
        echo "💡 Tip: Install nmap for enhanced scanning capabilities:"
        echo "   ${CYAN}brew install nmap${NC}"
        echo ""
    fi
    if [[ "$FAST_SCAN" == false ]] && [[ "$NMAP_AVAILABLE" == true ]]; then
        echo "💡 Use ${CYAN}-f${NC} or ${CYAN}--fast${NC} for quicker scans (ping only)"
        echo ""
    fi
}

# Main execution
main() {
    echo ""
    echo "🔍 WiFi Peer Discovery Script"
    echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
    
    check_wifi_connection
    get_network_info
    scan_network
    print_summary
}

# Run main function
main "$@"