Fix CIDR functions so they work

git-svn-id: http://svn.inspircd.org/repository/trunk/inspircd@4731 e03df62e-2008-0410-955e-edbf42e46eb7

1 files changed, 12 insertions, 7 deletions

diff --git a/src/socket.cpp b/src/socket.cpp
index 7ef7f225e..41c4fd1ca 100644
--- a/src/socket.cpp
+++ b/src/socket.cpp
@@ -29,27 +29,32 @@ extern time_t TIME;
 
 /* Used when comparing CIDR masks for the modulus bits left over */
 
-char inverted_bits[8] = { 0x80, /* 10000000 - 1 bits */
+char inverted_bits[8] = { 0x00, /* 00000000 - 0 bits */
+			  0x80, /* 10000000 - 1 bits */
 			  0xC0, /* 11000000 - 2 bits */
 			  0xE0, /* 11100000 - 3 bits */
 			  0xF0, /* 11110000 - 4 bits */
 			  0xF8, /* 11111000 - 5 bits */
 			  0xFC, /* 11111100 - 6 bits */
-			  0xFE, /* 11111110 - 7 bits */
-			  0xFF, /* 11111111 - 8 bits */
+			  0xFE  /* 11111110 - 7 bits */
 };
 
 bool MatchCIDRBits(unsigned char* address, unsigned char* mask, unsigned int mask_bits)
 {
-	unsigned int modulus = mask_bits % 8;
-	unsigned int divisor = mask_bits / 8;
+	unsigned int modulus = mask_bits  & 0x07; /* Number of whole bytes in the mask */
+	unsigned int divisor = mask_bits >> 0x04; /* Remaining bits in the mask after whole bytes are dealt with */
 
+	/* First compare the whole bytes, if they dont match, return false */
 	if (memcmp(address, mask, divisor))
-			return false;
+		return false;
+
+	/* Now if there are any remainder bits, we compare them with logic AND */
 	if (modulus)
-		if ((address[divisor] & inverted_bits[modulus]) != address[divisor])
+		if ((address[divisor] & inverted_bits[modulus]) != (mask[divisor] & inverted_bits[modulus]))
+			/* If they dont match, return false */
 			return false;
 
+	/* The address matches the mask, to mask_bits bits of mask */
 	return true;
 }