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1# Copyright 2018 The Chromium OS Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5"""Return information about routing table entries
6
7Read and parse the system routing table. There are
8four classes defined here: NetworkRoutes, which contains
9information about all routes; IPv4Route, which describes
10a single IPv4 routing table entry; IPv6Route, which
11does the same for IPv6; and Route, which has common code
12for IPv4Route and IPv6Route.
13"""
14
15ROUTES_V4_FILE = "/proc/net/route"
16ROUTES_V6_FILE = "/proc/net/ipv6_route"
17
18# The following constants are from <net/route.h>
19RTF_UP      = 0x0001
20RTF_GATEWAY = 0x0002
21RTF_HOST    = 0x0004
22# IPv6 constants from <net/route.h>
23RTF_DEFAULT = 0x10000
24
25import socket
26import struct
27
28class Route(object):
29    def __init__(self, iface, dest, gway, flags, mask):
30        self.interface = iface
31        self.destination = dest
32        self.gateway = gway
33        self.flagbits = flags
34        self.netmask = mask
35
36    def __str__(self):
37        flags = ""
38        if self.flagbits & RTF_UP:
39            flags += "U"
40        if self.flagbits & RTF_GATEWAY:
41            flags += "G"
42        if self.flagbits & RTF_HOST:
43            flags += "H"
44        if self.flagbits & RTF_DEFAULT:
45            flags += "D"
46        return "<%s dest: %s gway: %s mask: %s flags: %s>" % (
47                self.interface,
48                self._intToIp(self.destination),
49                self._intToIp(self.gateway),
50                self._intToIp(self.netmask),
51                flags)
52
53    def isUsable(self):
54        return self.flagbits & RTF_UP
55
56    def isHostRoute(self):
57        return self.flagbits & RTF_HOST
58
59    def isGatewayRoute(self):
60        return self.flagbits & RTF_GATEWAY
61
62    def isInterfaceRoute(self):
63        return (self.flagbits & RTF_GATEWAY) == 0
64
65    def matches(self, ip):
66        try:
67            return (self._ipToInt(ip) & self.netmask) == self.destination
68        except socket.error:
69            return False
70
71
72class IPv4Route(Route):
73    def __init__(self, iface, dest, gway, flags, mask):
74        super(IPv4Route, self).__init__(
75            iface, int(dest, 16), int(gway, 16), int(flags, 16), int(mask, 16))
76
77    def _intToIp(self, addr):
78        return socket.inet_ntoa(struct.pack('@I', addr))
79
80    def _ipToInt(self, ip):
81        return struct.unpack('I', socket.inet_aton(ip))[0]
82
83    def isDefaultRoute(self):
84        return (self.flagbits & RTF_GATEWAY) and self.destination == 0
85
86def parseIPv4Routes(routelist):
87    # The first line is headers that will allow us
88    # to correctly interpret the values in the following
89    # lines
90    headers = routelist[0].split()
91    col_map = {token: pos for (pos, token) in enumerate(headers)}
92
93    routes = []
94    for routeline in routelist[1:]:
95        route = routeline.split()
96        interface = route[col_map["Iface"]]
97        destination = route[col_map["Destination"]]
98        gateway = route[col_map["Gateway"]]
99        flags = route[col_map["Flags"]]
100        mask = route[col_map["Mask"]]
101        routes.append(IPv4Route(interface, destination, gateway, flags, mask))
102
103    return routes
104
105
106class IPv6Route(Route):
107    def __init__(self, iface, dest, gway, flags, plen):
108        super(IPv6Route, self).__init__(
109            iface,
110            long(dest, 16),
111            long(gway, 16),
112            long(flags, 16),
113            # netmask = set first plen bits to 1, all following to 0
114            (1 << 128) - (1 << (128 - int(plen, 16))))
115
116    def _intToIp(self, addr):
117        return socket.inet_ntop(socket.AF_INET6, ("%032x" % addr).decode("hex"))
118
119    def _ipToInt(self, ip):
120        return long(socket.inet_pton(socket.AF_INET6, ip).encode("hex"), 16)
121
122    def isDefaultRoute(self):
123        return self.flagbits & RTF_DEFAULT
124
125def parseIPv6Routes(routelist):
126    # ipv6_route has no headers, so the routing table looks like the following:
127    # Dest DestPrefix Src SrcPrefix Gateway Metric RefCnt UseCnt Flags Iface
128    routes = []
129    for routeline in routelist:
130        route = routeline.split()
131        interface = route[9]
132        destination = route[0]
133        gateway = route[4]
134        flags = route[8]
135        prefix = route[1]
136        routes.append(IPv6Route(interface, destination, gateway, flags, prefix))
137
138    return routes
139
140
141class NetworkRoutes(object):
142    def __init__(self, routelist_v4=None, routelist_v6=None):
143        if routelist_v4 is None:
144            with open(ROUTES_V4_FILE) as routef_v4:
145                routelist_v4 = routef_v4.readlines()
146
147        self.routes = parseIPv4Routes(routelist_v4)
148
149        if routelist_v6 is None:
150            with open(ROUTES_V6_FILE) as routef_v6:
151                routelist_v6 = routef_v6.readlines()
152
153        self.routes += parseIPv6Routes(routelist_v6)
154
155    def _filterUsableRoutes(self):
156        return (rr for rr in self.routes if rr.isUsable())
157
158    def hasDefaultRoute(self, interface):
159        return any(rr for rr in self._filterUsableRoutes()
160                   if (rr.interface == interface and rr.isDefaultRoute()))
161
162    def getDefaultRoutes(self):
163        return [rr for rr in self._filterUsableRoutes() if rr.isDefaultRoute()]
164
165    def hasInterfaceRoute(self, interface):
166        return any(rr for rr in self._filterUsableRoutes()
167                   if (rr.interface == interface and rr.isInterfaceRoute()))
168
169    def getRouteFor(self, ip):
170        for rr in self._filterUsableRoutes():
171            if rr.matches(ip):
172                return rr
173        return None
174