#!/usr/libexec/platform-python

## Created by Andrii Ivanov
##       Namecheap

##
##  We need to monitor the state of TCP connections from the public IP interface on our servers.
##  Check status based on successful TCP probes to destination address: port.
##  

##
## Icinga Status
## CRITICAL - counter is equal to 0 successful TCP probes.
## WARNING - counter is less {--checks_count} and more then 0 successful TCP probes
## OK - counter is equal to {--checks_count} successful TCP probes
##

import argparse
import socket
import threading
import re
import os
from time import sleep, time

# Arguments parser
parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument("-a", "--dst_address", default="google.com", help="Destination address")
parser.add_argument("-p", "--dst_port", default="80", help="Destination port")
parser.add_argument("-t", "--sock_timeout", default="5", help="Socket connection timeout")
parser.add_argument("-c", "--checks_count", default="3", help="Connection attempt count")
parser.add_argument("-v", "--verbose", default=False, action="store_true", help="Extra output")
parser.add_argument("-d", "--dynamic_src_port", default=True, action="store_false", help="Dynamic src port for probes")
parser.add_argument("-l", "--include_private_ip", default=False, action="store_true", help="Include private IP")
parser.add_argument("-x", "--exclude_ips", nargs="+", help="Exclude IPs")
args = parser.parse_args()

# Variables
DST_ADDRESS = args.dst_address
DST_PORT = int(args.dst_port)
SOCK_TIMEOUT = int(args.sock_timeout)
CHECKS_COUNT = int(args.checks_count)
EXCLUDE_IPS = args.exclude_ips
PRIVATE_REGEX = re.compile('(^127\.)|(^10\.)|(^172\.1[6-9]\.)|(^172\.2[0-9]\.)|(^172\.3[0-1]\.)|(^192\.168\.)')
GLOBAL_REGEX = re.compile('(\d+)(?<!10)\.(\d+)(?<!192\.168)(?<!172\.(1[6-9]|2\d|3[0-1]))\.(\d+)\.(\d+)')
THREADS = []
MAX_THREADS = 10
REPORT = {}
CRITICAL = ""
WARNING = ""
TOTAL = ""

def get_source_ip():
    """a function for get set of local IP addresses"""
    addresses = []
    IP_LIST = os.popen('hostname -I')
    IPS = IP_LIST.read().strip().split(" ")
    for IP in IPS:
        if GLOBAL_REGEX.match(IP): 
            addresses.append(IP)
        if args.include_private_ip: 
            if PRIVATE_REGEX.match(IP): 
                addresses.append(IP)
        if args.exclude_ips:
            for E_IP in EXCLUDE_IPS:
                if re.compile("^"+E_IP).match(IP):
                    addresses.remove(IP)
    return addresses


def check_tcp_connection(SRC_IP):
    """a function for TCP check the connection and generate the report"""
    SRC_PORT = 0
    COUNTER = 0
    for _ in range(CHECKS_COUNT):
        try:
            if args.verbose: 
                start_time = time()
            client_socket = socket.socket()
            client_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            client_socket.settimeout(SOCK_TIMEOUT)
            client_socket.bind((SRC_IP, SRC_PORT))
            if args.dynamic_src_port: 
                SRC_PORT = int(client_socket.getsockname()[1]) # minimize ports usage
            result = client_socket.connect_ex((DST_ADDRESS, DST_PORT))
            client_socket.close()
            if args.verbose:
                end_time = time()
                exec_time = end_time - start_time
            if result == 0:
                COUNTER += 1
                if args.verbose: print ("%s:%s open counter=%d time=%f" % (SRC_IP, SRC_PORT, COUNTER, exec_time))
            else:
                if args.verbose: print ("%s:%s closed counter=%d time=%f" % (SRC_IP, SRC_PORT, COUNTER, exec_time))
                pass
            sleep(0.1)
        except socket.error as exc:
            print("%s: %s. Is destination address correct?" % (SRC_IP,exc))
            pass   
    if COUNTER == CHECKS_COUNT:
        REPORT[SRC_IP] = "OK"
    elif COUNTER < CHECKS_COUNT and COUNTER > 0:
        REPORT[SRC_IP] = "WARNING"
    elif COUNTER == 0:
        REPORT[SRC_IP] = "CRITICAL"


# multithreading
for SRC_IP in get_source_ip():
    THREAD = threading.Thread(target=check_tcp_connection, args=[SRC_IP])
    THREADS.append(THREAD)
# threads start
for THREAD in THREADS:
    THREAD.start()
    while threading.active_count() > MAX_THREADS:
        sleep(0.5)
# THREAD waiting
for THREAD in THREADS:
    THREAD.join()

if args.verbose: print(" ")
if args.verbose: print(REPORT)
if args.verbose: print(" ")

# generating Icinga check result output
for key, value in REPORT.items():
    if value == "CRITICAL":
        CRITICAL = CRITICAL + key + " "
    elif value == "WARNING":
        WARNING = WARNING + key + " "

if CRITICAL:
    TOTAL = "CRITICAL - " + CRITICAL
if WARNING:
    TOTAL = TOTAL + "WARNING - " + WARNING

if TOTAL:
    print(TOTAL)
else:
    print("OK")