📜Bash Script to Log Packet Loss via mtr⚗️

The script below attempts to pick up packet loss issues to a destination IP address over a longer period while still measuring the loss over a count of 100 packets.

It logs the anomalies which can then be shared.

#!/bin/bash

# Ensure the script is run with a target IP/hostname as an argument
if [ -z "$1" ]; then
   echo "Usage: $0 <target>"
   exit 1
fi

# Variables
TARGET=$1 # Get target from the command line
PING_COUNT=200
ITERATIONS=1000
LOSS_THRESHOLD=${2:-2}  # Packet loss threshold, default is 2% if not provided
DAY_OF_WEEK=$(date +%A) # Get the current day of the week (e.g., Monday)
LOG_FILE="/tmp/mtr_report_${TARGET}_${DAY_OF_WEEK}.log" # Log file in /tmp directory

# Function to check packet loss of the last hop and log the full mtr report if necessary
check_packet_loss_or_path_change() {
    # Run mtr and capture the full output
    MTR_OUTPUT=$(mtr -r -c $PING_COUNT $TARGET)
    echo "$MTR_OUTPUT"

    # Extract the packet loss percentage of the last hop
    LOSS_PERCENT=$(echo "$MTR_OUTPUT" | tail -n 1 | awk '{print $3}' | sed 's/%//')
    echo "Actual: $LOSS_PERCENT"
    echo "Threshold: $LOSS_THRESHOLD"

    # Extract the previous hop's IP addresses (excluding the last hop)
    CURRENT_PATH=$(echo "$MTR_OUTPUT" | awk '{print $2}' | head -n -1 | tail -n +2)
    echo "Path: $CURRENT_PATH"

    # Check if a path change occurred by comparing the current path with the previous one
    if [ "$CURRENT_PATH" != "$PREVIOUS_PATH" ]; then
       PATH_CHANGED=true
       echo "Path changed!"
    else
       PATH_CHANGED=false
    fi

    # If packet loss is greater than loss linit, or if there's a path change, log the full mtr report with timestamp
    if (( $(echo "$LOSS_PERCENT > $LOSS_THRESHOLD" | bc -l) )) || [ "$PATH_CHANGED" = true ]; then
       echo "Logging MTR output."
       echo "--------------------------------------" >> $LOG_FILE
       echo "$(date): Packet loss on last hop ($LOSS_PERCENT%) or path change detected" >> $LOG_FILE
       echo "$MTR_OUTPUT" >> $LOG_FILE
       echo "--------------------------------------" >> $LOG_FILE
    fi
    # Store the current path as the previous path for the next iteration
    PREVIOUS_PATH=$CURRENT_PATH
}

# Initialize the previous path as an empty string for the first run
PREVIOUS_PATH=""

# Main loop to run mtr 1000 times
for ((i=1; i<=$ITERATIONS; i++)); do
   echo "Running mtr iteration $i for target $TARGET..."
   check_packet_loss_or_path_change
done

echo "Completed $ITERATIONS iterations of mtr."