Implemented the combine_all function for Cidrs containing one another.

[hath.git] / src / Cidr.hs

diff --git a/src/Cidr.hs b/src/Cidr.hs
index efd3ae0413b43095ae2dab5abc046f6885806354..266b7c57f8a8e8318124a2518900de75a4d166ca 100644 (file)
--- a/src/Cidr.hs
+++ b/src/Cidr.hs
@@ -1,45 +1,111 @@
 module Cidr
 ( Cidr(..),
   cidr_from_string,
-  is_valid_cidr
+  combine_all
 ) where
 
-import Text.Regex.Posix
-
 import IPv4Address
 import ListUtils
+import Maskable
+import Maskbits
 import Octet
 
 
-data Cidr = Cidr { ipv4address :: IPv4Address,
-                   maskbits :: Maskbits }
+data Cidr = None | Cidr { ipv4address :: IPv4Address,
+                          maskbits :: Maskbits }
             deriving (Eq, Show)
 
--- Will return True if the passed String is in CIDR notation, False
--- otherwise.
-is_valid_cidr :: String -> Bool
-is_valid_cidr cidr = cidr =~ "([0-9]{1,3}\\.){3}[0-9]{1,3}/[0-9]{1,2}"
-
 
 -- Returns the mask portion of a CIDR address. That is, everything
 -- after the trailing slash.
-maskbits_from_string :: String -> Maskbits
-maskbits_from_string s = read ((splitWith (`elem` "/") s) !! 1)
+maskbits_from_cidr_string :: String -> Maskbits
+maskbits_from_cidr_string s =
+    maskbits_from_string ((splitWith (`elem` "/") s) !! 1)
 
 
 -- Takes an IP address String in CIDR notation, and returns a list of
 -- its octets (as Ints).
-octets_from_string :: String -> [Int]
-octets_from_string s = map read (take 4 (splitWith (`elem` "./") s))
+octets_from_cidr_string :: String -> [Octet]
+octets_from_cidr_string s =
+    map octet_from_string (take 4 (splitWith (`elem` "./") s))
 
 
 cidr_from_string :: String -> Cidr
-cidr_from_string s = Cidr addr mbits
+cidr_from_string s
+    | addr  == IPv4Address.None = Cidr.None
+    | mbits == Maskbits.None    = Cidr.None
+    | otherwise = Cidr addr mbits
                where
-                 addr = IPv4Address (oct1) (oct2) (oct3) (oct4)
-                 oct1 = octet_from_int (octs !! 0)
-                 oct2 = octet_from_int (octs !! 1)
-                 oct3 = octet_from_int (octs !! 2)
-                 oct4 = octet_from_int (octs !! 3)
-                 octs  = octets_from_string s
-                 mbits = maskbits_from_string s
+                 addr = ipv4address_from_octets (oct1) (oct2) (oct3) (oct4)
+                 oct1 = (octs !! 0)
+                 oct2 = (octs !! 1)
+                 oct3 = (octs !! 2)
+                 oct4 = (octs !! 3)
+                 octs  = octets_from_cidr_string s
+                 mbits = maskbits_from_cidr_string s
+
+
+
+-- Return true if the first argument (a CIDR range) contains the
+-- second (another CIDR range). There are a lot of ways we can be fed
+-- junk here. For lack of a better alternative, just return False when
+-- we are given nonsense.
+contains :: Cidr -> Cidr -> Bool
+contains Cidr.None _ = False
+contains _ Cidr.None = False
+contains (Cidr _ Maskbits.None) _    = False
+contains (Cidr IPv4Address.None _) _ = False
+contains _ (Cidr _ Maskbits.None)    = False
+contains _ (Cidr IPv4Address.None _) = False
+
+-- If the number of bits in the network part of the first address is
+-- larger than the number of bits in the second, there is no way that
+-- the first range can contain the second. For, if the number of
+-- network bits is larger, then the number of host bits must be
+-- smaller, and if cidr1 has fewer hosts than cidr2, cidr1 most
+-- certainly does not contain cidr2.
+--
+-- On the other hand, if the first argument (cidr1) has fewer (or the
+-- same number of) network bits as the second, it can contain the
+-- second. In this case, we need to check that every host in cidr2 is
+-- contained in cidr1. If a host in cidr2 is contained in cidr1, then
+-- at least mbits1 of an address in cidr2 will match cidr1. For
+-- example,
+--
+-- cidr1 = 192.168.1.0/23, cidr2 = 192.168.1.100/24
+--
+-- Here, cidr2 contains all of 192.168.1.0 through
+-- 192.168.1.255. However, cidr1 contains BOTH 192.168.0.0 through
+-- 192.168.0.255 and 192.168.1.0 through 192.168.1.255. In essence,
+-- what we want to check is that cidr2 "begins with" something that
+-- cidr1 CAN begin with. Since cidr1 can begin with 192.168.1, and
+-- cidr2 DOES, cidr1 contains cidr2..
+--
+-- The way that we check this is to apply cidr1's mask to cidr2's
+-- address and see if the result is the same as cidr1's mask applied
+-- to cidr1's address.
+--
+contains (Cidr addr1 mbits1) (Cidr addr2 mbits2)
+    | mbits1 > mbits2 = False
+    | otherwise = addr1masked == addr2masked
+    where
+      addr1masked = apply_mask addr1 mbits1
+      addr2masked = apply_mask addr2 mbits1
+
+
+contains_proper :: Cidr -> Cidr -> Bool
+contains_proper cidr1 cidr2 =
+    (cidr1 `contains` cidr2) && (not (cidr1 == cidr2))
+
+
+-- A CIDR range is redundant (with respect to the given list) if
+-- another CIDR range in that list properly contains it.
+redundant :: [Cidr] -> Cidr -> Bool
+redundant cidrlist cidr = any ((flip contains_proper) cidr) cidrlist
+
+
+-- We want to get rid of all the Cidrs that are properly contained
+-- in some other Cidr.
+combine_all :: [Cidr] -> [Cidr]
+combine_all cidrs =
+    filter (not . (redundant cidrs)) cidrs