dns-latency-test.sh

#!/bin/bash

TEST_DOMAIN="download.docker.com"
PING_TIMEOUT=10
TEMP_RESULTS_FILE=$(mktemp)
DNS_LIST_FILE="dns-servers.txt"

COLOR_RED='\033[0;31m'
COLOR_YELLOW='\033[0;33m'
COLOR_GREEN='\033[0;32m'
COLOR_RESET='\033[0m'

validate_dns_list_file() {
    if [[ ! -f $DNS_LIST_FILE ]]; then
        echo "Error: $DNS_LIST_FILE not found!"
        exit 1
    fi
}

display_header() {
    echo "Testing DNS latency (Max: ${PING_TIMEOUT}s)..."
    echo "------------------------------------------------------"
    echo "DNS Server          Ping (ms)   Query Time (ms)"
    echo "------------------------------------------------------"
}

check_ping_latency() {
    local dns_ip=$1
    ping -c 1 -W "$PING_TIMEOUT" "$dns_ip" | awk -F'=' '/time=/ {print $4}' | cut -d' ' -f1
}

check_dns_response_time() {
    local dns_ip=$1
    dig @$dns_ip $TEST_DOMAIN +stats +time="$PING_TIMEOUT" | awk '/Query time:/ {print $4}'
}

get_response_time_color() {
    local response_time=$1
    if [[ "$response_time" == "Timeout" ]]; then
        echo "$COLOR_RED"
    elif [[ "$response_time" -lt 50 ]]; then
        echo "$COLOR_GREEN"
    elif [[ "$response_time" -lt 150 ]]; then
        echo "$COLOR_YELLOW"
    else
        echo "$COLOR_RED"
    fi
}

run_dns_test() {
    local dns_ip=$1
    local ping_time response_time color

    ping_time=$(check_ping_latency "$dns_ip")
    if [[ -z "$ping_time" ]]; then
        printf "%-20s ${COLOR_RED}Timeout${COLOR_RESET}   ${COLOR_RED}Unreachable${COLOR_RESET}\n" "$dns_ip" >> "$TEMP_RESULTS_FILE"
        return
    fi

    response_time=$(check_dns_response_time "$dns_ip")
    if [[ -z "$response_time" || "$response_time" == "Timeout" ]]; then
        response_time="Timeout"
    fi
    color=$(get_response_time_color "$response_time")

    if [[ "$response_time" == "Timeout" ]]; then
        printf "%-20s ${COLOR_RED}%s ms${COLOR_RESET}   ${COLOR_RED}Timeout${COLOR_RESET}\n" "$dns_ip" "$ping_time" >> "$TEMP_RESULTS_FILE"
    else
        printf "%-20s ${COLOR_GREEN}%s ms${COLOR_RESET}   %s%s ms${COLOR_RESET}\n" "$dns_ip" "$ping_time" "$color" "$response_time" >> "$TEMP_RESULTS_FILE"
    fi
}

process_dns_servers() {
    while read -r dns_ip; do
        [[ -n "$dns_ip" ]] && run_dns_test "$dns_ip" &
    done < "$DNS_LIST_FILE"
    wait
}

display_results() {
    sort -nk3 "$TEMP_RESULTS_FILE" 2>/dev/null
}

display_fastest_slowest() {
    local fastest slowest
    fastest=$(awk '$3 ~ /^[0-9]+$/ {print $0}' "$TEMP_RESULTS_FILE" | sort -nk3 | head -n 1)
    slowest=$(awk '$3 ~ /^[0-9]+$/ {print $0}' "$TEMP_RESULTS_FILE" | sort -nk3 | tail -n 1)

    if [[ -n "$fastest" && "$fastest" != "Timeout" ]]; then
        echo -e "\n🚀 Fastest DNS: ${COLOR_GREEN}${fastest}${COLOR_RESET}"
    else
        echo -e "\n🚀 Fastest DNS: ${COLOR_RED}No valid DNS found${COLOR_RESET}"
    fi

    if [[ -n "$slowest" && "$slowest" != "Timeout" ]]; then
        echo -e "🐢 Slowest DNS: ${COLOR_RED}${slowest}${COLOR_RESET}"
    else
        echo -e "🐢 Slowest DNS: ${COLOR_RED}No valid DNS found${COLOR_RESET}"
    fi
}

validate_dns_list_file

display_header

process_dns_servers

display_results

display_fastest_slowest

rm -f "$TEMP_RESULTS_FILE"