src/Cidr.hs

   1 module Cidr
   2 ( Cidr(..),
   3   cidr_from_string,
   4   cidr_tests,
   5   combine_all
   6 ) where
   7
   8 import Data.List (nubBy)
   9 import Test.HUnit
  10 import Test.QuickCheck
  11
  12 import IPv4Address
  13 import ListUtils
  14 import Maskable
  15 import Maskbits
  16 import Octet
  17
  18
  19 data Cidr = None | Cidr { ipv4address :: IPv4Address,
  20                           maskbits :: Maskbits }
  21             deriving (Eq)
  22
  23
  24 instance Show Cidr where
  25     show Cidr.None = "None"
  26     show cidr = (show (ipv4address cidr)) ++ "/" ++ (show (maskbits cidr))
  27
  28
  29 instance Arbitrary Cidr where
  30     arbitrary = do
  31       ipv4 <- arbitrary :: Gen IPv4Address
  32       mask <- arbitrary :: Gen Maskbits
  33       return (Cidr ipv4 mask)
  34
  35     coarbitrary _ = variant 0
  36
  37
  38 -- Two CIDR ranges are equivalent if they have the same network bits
  39 -- and the masks are the same.
  40 equivalent :: Cidr -> Cidr -> Bool
  41 equivalent Cidr.None Cidr.None = True
  42 equivalent Cidr.None _ = False
  43 equivalent _ Cidr.None = False
  44 equivalent (Cidr addr1 mbits1) (Cidr addr2 mbits2) =
  45     (mbits1 == mbits2) && ((apply_mask addr1 mbits1) == (apply_mask addr2 mbits2))
  46
  47 -- Returns the mask portion of a CIDR address. That is, everything
  48 -- after the trailing slash.
  49 maskbits_from_cidr_string :: String -> Maskbits
  50 maskbits_from_cidr_string s =
  51     maskbits_from_string ((splitWith (`elem` "/") s) !! 1)
  52
  53
  54 -- Takes an IP address String in CIDR notation, and returns a list of
  55 -- its octets (as Ints).
  56 octets_from_cidr_string :: String -> [Octet]
  57 octets_from_cidr_string s =
  58     map octet_from_string (take 4 (splitWith (`elem` "./") s))
  59
  60
  61 cidr_from_string :: String -> Cidr
  62 cidr_from_string s
  63     | addr  == IPv4Address.None = Cidr.None
  64     | mbits == Maskbits.None    = Cidr.None
  65     | otherwise = Cidr addr mbits
  66                where
  67                  addr = ipv4address_from_octets (oct1) (oct2) (oct3) (oct4)
  68                  oct1 = (octs !! 0)
  69                  oct2 = (octs !! 1)
  70                  oct3 = (octs !! 2)
  71                  oct4 = (octs !! 3)
  72                  octs  = octets_from_cidr_string s
  73                  mbits = maskbits_from_cidr_string s
  74
  75
  76
  77 -- Return true if the first argument (a CIDR range) contains the
  78 -- second (another CIDR range). There are a lot of ways we can be fed
  79 -- junk here. For lack of a better alternative, just return False when
  80 -- we are given nonsense.
  81 contains :: Cidr -> Cidr -> Bool
  82 contains Cidr.None _ = False
  83 contains _ Cidr.None = False
  84 contains (Cidr _ Maskbits.None) _    = False
  85 contains (Cidr IPv4Address.None _) _ = False
  86 contains _ (Cidr _ Maskbits.None)    = False
  87 contains _ (Cidr IPv4Address.None _) = False
  88
  89 -- If the number of bits in the network part of the first address is
  90 -- larger than the number of bits in the second, there is no way that
  91 -- the first range can contain the second. For, if the number of
  92 -- network bits is larger, then the number of host bits must be
  93 -- smaller, and if cidr1 has fewer hosts than cidr2, cidr1 most
  94 -- certainly does not contain cidr2.
  95 --
  96 -- On the other hand, if the first argument (cidr1) has fewer (or the
  97 -- same number of) network bits as the second, it can contain the
  98 -- second. In this case, we need to check that every host in cidr2 is
  99 -- contained in cidr1. If a host in cidr2 is contained in cidr1, then
 100 -- at least mbits1 of an address in cidr2 will match cidr1. For
 101 -- example,
 102 --
 103 -- cidr1 = 192.168.1.0/23, cidr2 = 192.168.1.100/24
 104 --
 105 -- Here, cidr2 contains all of 192.168.1.0 through
 106 -- 192.168.1.255. However, cidr1 contains BOTH 192.168.0.0 through
 107 -- 192.168.0.255 and 192.168.1.0 through 192.168.1.255. In essence,
 108 -- what we want to check is that cidr2 "begins with" something that
 109 -- cidr1 CAN begin with. Since cidr1 can begin with 192.168.1, and
 110 -- cidr2 DOES, cidr1 contains cidr2..
 111 --
 112 -- The way that we check this is to apply cidr1's mask to cidr2's
 113 -- address and see if the result is the same as cidr1's mask applied
 114 -- to cidr1's address.
 115 --
 116 contains (Cidr addr1 mbits1) (Cidr addr2 mbits2)
 117     | mbits1 > mbits2 = False
 118     | otherwise = addr1masked == addr2masked
 119     where
 120       addr1masked = apply_mask addr1 mbits1
 121       addr2masked = apply_mask addr2 mbits1
 122
 123
 124 contains_proper :: Cidr -> Cidr -> Bool
 125 contains_proper cidr1 cidr2 =
 126     (cidr1 `contains` cidr2) && (not (cidr1 == cidr2))
 127
 128
 129 -- A CIDR range is redundant (with respect to the given list) if
 130 -- another CIDR range in that list properly contains it.
 131 redundant :: [Cidr] -> Cidr -> Bool
 132 redundant cidrlist cidr = any ((flip contains_proper) cidr) cidrlist
 133
 134
 135 -- First, we look at all possible pairs of cidrs, and combine the
 136 -- adjacent ones in to a new list. Then, we concatenate that list with
 137 -- the original one, and filter out all of the redundancies. If two
 138 -- adjacent Cidrs are combined into a larger one, they will be removed
 139 -- in the second step since the larger Cidr must contain the smaller
 140 -- two.
 141 combine_all :: [Cidr] -> [Cidr]
 142 combine_all cidrs =
 143     combine_contained unique_cidrs
 144     where
 145       unique_cidrs = nubBy equivalent valid_cidr_combinations
 146       valid_cidr_combinations = filter (/= Cidr.None) cidr_combinations
 147       cidr_combinations =
 148           cidrs ++ [ (combine_adjacent x y) | x <- cidrs, y <- cidrs ]
 149
 150
 151 -- Take a list of CIDR ranges and filter out all of the ones that are
 152 -- contained entirelt within some other range in the list.
 153 combine_contained :: [Cidr] -> [Cidr]
 154 combine_contained cidrs =
 155     filter (not . (redundant cidrs)) cidrs
 156
 157
 158 -- If the two Cidrs are not adjacent, return Cidr.None. Otherwise,
 159 -- decrement the maskbits of cidr1 and return that; it will contain
 160 -- both cidr1 and cidr2.
 161 combine_adjacent :: Cidr -> Cidr -> Cidr
 162 combine_adjacent cidr1 cidr2
 163   | not (adjacent cidr1 cidr2) = Cidr.None
 164   | (maskbits cidr1 == Zero) = Cidr.None
 165   | otherwise = cidr1 { maskbits = decrement (maskbits cidr1) }
 166
 167
 168
 169 -- Determine whether or not two CIDR ranges are adjacent. If two
 170 -- ranges lie consecutively within the IP space, they can be
 171 -- combined. For example, 10.1.0.0/24 and 10.0.1.0/24 are adjacent,
 172 -- and can be combined in to 10.1.0.0/23.
 173 adjacent :: Cidr -> Cidr -> Bool
 174 adjacent Cidr.None _ = False
 175 adjacent _ Cidr.None = False
 176 adjacent cidr1 cidr2
 177   | mbits1 /= mbits2 = False
 178   | mbits1 == Maskbits.Zero = False -- They're equal.
 179   | otherwise = (mbits1 == (most_sig_bit_different addr1 addr2))
 180   where
 181     addr1 = ipv4address cidr1
 182     addr2 = ipv4address cidr2
 183     mbits1 = maskbits cidr1
 184     mbits2 = maskbits cidr2
 185
 186
 187
 188
 189
 190 -- HUnit Tests
 191
 192 test_equality1 :: Test
 193 test_equality1 =
 194     TestCase $ assertEqual "10.1.1.0/23 equals itself" True (cidr1 == cidr1)
 195     where
 196       cidr1 = cidr_from_string "10.1.1.0/23"
 197
 198
 199 test_contains1 :: Test
 200 test_contains1 =
 201     TestCase $ assertEqual "10.1.1.0/23 contains 10.1.1.0/24" True (cidr1 `contains` cidr2)
 202     where
 203       cidr1 = cidr_from_string "10.1.1.0/23"
 204       cidr2 = cidr_from_string "10.1.1.0/24"
 205
 206
 207 test_contains2 :: Test
 208 test_contains2 =
 209     TestCase $ assertEqual "10.1.1.0/23 contains itself" True (cidr1 `contains` cidr1)
 210     where
 211       cidr1 = cidr_from_string "10.1.1.0/23"
 212
 213
 214 test_contains_proper1 :: Test
 215 test_contains_proper1 =
 216     TestCase $ assertEqual "10.1.1.0/23 contains 10.1.1.0/24 properly" True (cidr1 `contains_proper` cidr2)
 217     where
 218       cidr1 = cidr_from_string "10.1.1.0/23"
 219       cidr2 = cidr_from_string "10.1.1.0/24"
 220
 221
 222 test_contains_proper2 :: Test
 223 test_contains_proper2 =
 224     TestCase $ assertEqual "10.1.1.0/23 does not contain itself properly" False (cidr1 `contains_proper` cidr1)
 225     where
 226       cidr1 = cidr_from_string "10.1.1.0/23"
 227
 228
 229 test_adjacent1 :: Test
 230 test_adjacent1 =
 231     TestCase $ assertEqual "10.1.0.0/24 is adjacent to 10.1.1.0/24" True (cidr1 `adjacent` cidr2)
 232     where
 233       cidr1 = cidr_from_string "10.1.0.0/24"
 234       cidr2 = cidr_from_string "10.1.1.0/24"
 235
 236
 237 test_adjacent2 :: Test
 238 test_adjacent2 =
 239     TestCase $ assertEqual "10.1.0.0/23 is not adjacent to 10.1.0.0/24" False (cidr1 `adjacent` cidr2)
 240     where
 241       cidr1 = cidr_from_string "10.1.0.0/23"
 242       cidr2 = cidr_from_string "10.1.0.0/24"
 243
 244
 245 test_adjacent3 :: Test
 246 test_adjacent3 =
 247     TestCase $ assertEqual "10.1.0.0/24 is not adjacent to 10.2.5.0/24" False (cidr1 `adjacent` cidr2)
 248     where
 249       cidr1 = cidr_from_string "10.1.0.0/24"
 250       cidr2 = cidr_from_string "10.2.5.0/24"
 251
 252
 253 test_adjacent4 :: Test
 254 test_adjacent4 =
 255     TestCase $ assertEqual "10.1.1.0/24 is not adjacent to 10.1.2.0/24" False (cidr1 `adjacent` cidr2)
 256     where
 257       cidr1 = cidr_from_string "10.1.1.0/24"
 258       cidr2 = cidr_from_string "10.1.2.0/24"
 259
 260
 261 test_combine_contained1 :: Test
 262 test_combine_contained1 =
 263     TestCase $ assertEqual "10.0.0.0/8, 10.1.0.0/16, and 10.1.1.0/24 combine to 10.0.0.0/8" expected_cidrs (combine_all test_cidrs)
 264     where
 265       cidr1 = cidr_from_string "10.0.0.0/8"
 266       cidr2 = cidr_from_string "10.1.0.0/16"
 267       cidr3 = cidr_from_string "10.1.1.0/24"
 268       expected_cidrs = [cidr1]
 269       test_cidrs = [cidr1, cidr2, cidr3]
 270
 271
 272 test_combine_contained2 :: Test
 273 test_combine_contained2 =
 274     TestCase $ assertEqual "192.168.1.0/24 combines with itself" [cidr1] (combine_all [cidr1, cidr1])
 275     where
 276       cidr1 = cidr_from_string "192.168.1.0/24"
 277
 278
 279 cidr_tests :: [Test]
 280 cidr_tests = [ test_equality1,
 281                test_contains1,
 282                test_contains2,
 283                test_contains_proper1,
 284                test_contains_proper2,
 285                test_adjacent1,
 286                test_adjacent2,
 287                test_adjacent3,
 288                test_adjacent4,
 289                test_combine_contained1,
 290                test_combine_contained2
 291              ]