#!/usr/bin/env python3
# Copyright (c) 2014-2016 The Bitcoin Core developers
# Copyright (c) 2017 The BitcoinSubsidium Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Linux network utilities.

Roughly based on http://voorloopnul.com/blog/a-python-netstat-in-less-than-100-lines-of-code/ by Ricardo Pascal
"""

import sys
import socket
import fcntl
import struct
import array
import os
from binascii import unhexlify, hexlify

# STATE_ESTABLISHED = '01'
# STATE_SYN_SENT  = '02'
# STATE_SYN_RECV = '03'
# STATE_FIN_WAIT1 = '04'
# STATE_FIN_WAIT2 = '05'
# STATE_TIME_WAIT = '06'
# STATE_CLOSE = '07'
# STATE_CLOSE_WAIT = '08'
# STATE_LAST_ACK = '09'
STATE_LISTEN = '0A'
# STATE_CLOSING = '0B'

def get_socket_inodes(pid):
    '''
    Get list of socket inodes for process pid.
    '''
    base = '/proc/%i/fd' % pid
    inodes = []
    for item in os.listdir(base):
        target = os.readlink(os.path.join(base, item))
        if target.startswith('socket:'):
            inodes.append(int(target[8:-1]))
    return inodes

def _remove_empty(array):
    return [x for x in array if x !='']

def _convert_ip_port(array):
    host,port = array.split(':')
    # convert host from mangled-per-four-bytes form as used by kernel
    host = unhexlify(host)
    host_out = ''
    for x in range(0, len(host) // 4):
        (val,) = struct.unpack('=I', host[x*4:(x+1)*4])
        host_out += '%08x' % val

    return host_out,int(port,16)

def netstat(typ='tcp'):
    '''
    Function to return a list with status of tcp connections at linux systems
    To get pid of all network process running on system, you must run this script
    as superuser
    '''
    with open('/proc/net/'+typ,'r',encoding='utf8') as f:
        content = f.readlines()
        content.pop(0)
    result = []
    for line in content:
        line_array = _remove_empty(line.split(' '))     # Split lines and remove empty spaces.
        tcp_id = line_array[0]
        l_addr = _convert_ip_port(line_array[1])
        r_addr = _convert_ip_port(line_array[2])
        state = line_array[3]
        inode = int(line_array[9])                      # Need the inode to match with process pid.
        nline = [tcp_id, l_addr, r_addr, state, inode]
        result.append(nline)
    return result

def get_bind_addrs(pid):
    '''
    Get bind addresses as (host,port) tuples for process pid.
    '''
    inodes = get_socket_inodes(pid)
    bind_addrs = []
    for conn in netstat('tcp') + netstat('tcp6'):
        if conn[3] == STATE_LISTEN and conn[4] in inodes:
            bind_addrs.append(conn[1])
    return bind_addrs

# from: http://code.activestate.com/recipes/439093/
def all_interfaces():
    '''
    Return all interfaces that are up
    '''
    is_64bits = sys.maxsize > 2**32
    struct_size = 40 if is_64bits else 32
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    max_possible = 8 # initial value
    while True:
        bytes = max_possible * struct_size
        names = array.array('B', b'\0' * bytes)
        outbytes = struct.unpack('iL', fcntl.ioctl(
            s.fileno(),
            0x8912,  # SIOCGIFCONF
            struct.pack('iL', bytes, names.buffer_info()[0])
        ))[0]
        if outbytes == bytes:
            max_possible *= 2
        else:
            break
    namestr = names.tostring()
    return [(namestr[i:i+16].split(b'\0', 1)[0],
             socket.inet_ntoa(namestr[i+20:i+24]))
            for i in range(0, outbytes, struct_size)]

def addr_to_hex(addr):
    '''
    Convert string IPv4 or IPv6 address to binary address as returned by
    get_bind_addrs.
    Very naive implementation that certainly doesn't work for all IPv6 variants.
    '''
    if '.' in addr: # IPv4
        addr = [int(x) for x in addr.split('.')]
    elif ':' in addr: # IPv6
        sub = [[], []] # prefix, suffix
        x = 0
        addr = addr.split(':')
        for i,comp in enumerate(addr):
            if comp == '':
                if i == 0 or i == (len(addr)-1): # skip empty component at beginning or end
                    continue
                x += 1 # :: skips to suffix
                assert(x < 2)
            else: # two bytes per component
                val = int(comp, 16)
                sub[x].append(val >> 8)
                sub[x].append(val & 0xff)
        nullbytes = 16 - len(sub[0]) - len(sub[1])
        assert((x == 0 and nullbytes == 0) or (x == 1 and nullbytes > 0))
        addr = sub[0] + ([0] * nullbytes) + sub[1]
    else:
        raise ValueError('Could not parse address %s' % addr)
    return hexlify(bytearray(addr)).decode('ascii')

def test_ipv6_local():
    '''
    Check for (local) IPv6 support.
    '''
    import socket
    # By using SOCK_DGRAM this will not actually make a connection, but it will
    # fail if there is no route to IPv6 localhost.
    have_ipv6 = True
    try:
        s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
        s.connect(('::1', 0))
    except socket.error:
        have_ipv6 = False
    return have_ipv6
