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initial commit for ip_prefix_subnets function
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tests and docs

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improved documentation

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changing return type when prefix_length arg is less specific that input prefix
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@matt-calder
matt-calder committed Sep 3, 2024
1 parent d69f1f8 commit 92db252
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9 changes: 9 additions & 0 deletions presto-docs/src/main/sphinx/functions/ip.rst
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Expand Up @@ -60,3 +60,12 @@ IP Functions
SELECT IP_PREFIX_COLLAPSE(ARRAY[IPPREFIX '2620:10d:c090::/48', IPPREFIX '2620:10d:c091::/48']); -- [{2620:10d:c090::/47}]
SELECT IP_PREFIX_COLLAPSE(ARRAY[IPPREFIX '192.168.1.0/24', IPPREFIX '192.168.0.0/24', IPPREFIX '192.168.2.0/24', IPPREFIX '192.168.9.0/24']); -- [{192.168.0.0/23}, {192.168.2.0/24}, {192.168.9.0/24}]

.. function:: ip_prefix_subnets(ip_prefix, prefix_length) -> array(ip_prefix)

Returns the subnets of ``ip_prefix`` of size ``prefix_length``. ``prefix_length`` must be valid ([0, 32] for IPv4
and [0, 128] for IPv6) or the query will fail and raise an error. An empty array is returned if ``prefix_length``
is shorter (that is, less specific) than ``ip_prefix``. ::

SELECT IP_PREFIX_SUBNETS(IPPREFIX '192.168.1.0/24', 25); -- [{192.168.1.0/25}, {192.168.1.128/25}]
SELECT IP_PREFIX_SUBNETS(IPPREFIX '2a03:2880:c000::/34', 36); -- [{2a03:2880:c000::/36}, {2a03:2880:d000::/36}, {2a03:2880:e000::/36}, {2a03:2880:f000::/36}]

62 changes: 62 additions & 0 deletions presto-main/src/main/java/com/facebook/presto/operator/scalar/IpPrefixFunctions.java
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Expand Up @@ -197,6 +197,63 @@ public static Block collapseIpPrefixes(@SqlType("array(IPPREFIX)") Block unsorte
return blockBuilder.build();
}

@Description("Split the input prefix into subnets the size of the new prefix length.")
@ScalarFunction("ip_prefix_subnets")
@SqlType("array(IPPREFIX)")
public static Block ipPrefixSubnets(@SqlType(StandardTypes.IPPREFIX) Slice prefix, @SqlType(StandardTypes.BIGINT) long newPrefixLength)
{
boolean inputIsIpV4 = isIpv4(prefix);

if (newPrefixLength < 0 || (inputIsIpV4 && newPrefixLength > 32) || (!inputIsIpV4 && newPrefixLength > 128)) {
throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Invalid prefix length for IPv" + (inputIsIpV4 ? "4" : "6") + ": " + newPrefixLength);
}

int inputPrefixLength = getPrefixLength(prefix);
// An IP prefix is a 'network', or group of contiguous IP addresses. The common format for describing IP prefixes is
// uses 2 parts separated by a '/': (1) the IP address part and the (2) prefix length part (also called subnet size or CIDR).
// For example, in 9.255.255.0/24, 9.255.255.0 is the IP address part and 24 is the prefix length.
// The prefix length describes how many IP addresses the prefix contains in terms of the leading number of bits required. A higher number of bits
// means smaller number of IP addresses. Subnets inherently mean smaller groups of IP addresses.
// We can only disaggregate a prefix if the prefix length is the same length or longer (more-specific) than the length of the input prefix.
// E.g., if the input prefix is 9.255.255.0/24, the prefix length can be /24, /25, /26, etc... but not 23 or larger value than 24.

int newPrefixCount = 0; // if inputPrefixLength > newPrefixLength, there are no new prefixes and we will return an empty array.
if (inputPrefixLength <= newPrefixLength) {
// Next, count how many new prefixes we will generate. In general, every difference in prefix length doubles the number new prefixes.
// For example if we start with 9.255.255.0/24, and want to split into /25s, we would have 2 new prefixes. If we wanted to split into /26s,
// we would have 4 new prefixes, and /27 would have 8 prefixes etc....
newPrefixCount = 1 << (newPrefixLength - inputPrefixLength); // 2^N
}

BlockBuilder blockBuilder = IPPREFIX.createBlockBuilder(null, newPrefixCount);
if (newPrefixCount <= 1) {
if (newPrefixCount == 1) {
IPPREFIX.writeSlice(blockBuilder, prefix); // just return the original prefix in an array
}
return blockBuilder.build(); // returns empty or single entry
}

int ipVersionMaxBits = inputIsIpV4 ? 32 : 128;
BigInteger newPrefixIpCount = TWO.pow(ipVersionMaxBits - (int) newPrefixLength);

Slice startingIpAddressAsSlice = ipSubnetMin(prefix);
BigInteger currentIpAddress = toBigInteger(startingIpAddressAsSlice);

try {
for (int i = 0; i < newPrefixCount; i++) {
InetAddress asInetAddress = bigIntegerToIpAddress(currentIpAddress);
Slice ipPrefixAsSlice = castFromVarcharToIpPrefix(utf8Slice(InetAddresses.toAddrString(asInetAddress) + "/" + newPrefixLength));
IPPREFIX.writeSlice(blockBuilder, ipPrefixAsSlice);
currentIpAddress = currentIpAddress.add(newPrefixIpCount); // increment to start of next new prefix
}
}
catch (UnknownHostException ex) {
throw new PrestoException(GENERIC_INTERNAL_ERROR, "Unable to convert " + currentIpAddress + " to IP prefix", ex);
}

return blockBuilder.build();
}

private static List<Slice> generateMinIpPrefixes(BigInteger firstIpAddress, BigInteger lastIpAddress, int ipVersionMaxBits)
{
List<Slice> ipPrefixSlices = new ArrayList<>();
Expand Down Expand Up @@ -358,6 +415,11 @@ private static boolean isIpv4(Slice ipPrefix)
return ipPartBytes[10] == (byte) 0xff && ipPartBytes[11] == (byte) 0xff;
}

private static int getPrefixLength(Slice ipPrefix)
{
return ipPrefix.getByte(IPPREFIX.getFixedSize() - 1) & 0xFF;
}

private static InetAddress toInetAddress(Slice ipAddress)
{
try {
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33 changes: 33 additions & 0 deletions presto-main/src/test/java/com/facebook/presto/operator/scalar/TestIpPrefixFunctions.java
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Expand Up @@ -216,4 +216,37 @@ public void testIpPrefixCollapseMixedIpVersionError()
assertInvalidFunction("IP_PREFIX_COLLAPSE(ARRAY[IPPREFIX '192.168.0.0/22', IPPREFIX '2409:4043:251a:d200::/56'])",
"All IPPREFIX elements must be the same IP version.");
}

@Test
public void testIpPrefixSubnets()
{
assertFunction("IP_PREFIX_SUBNETS(IPPREFIX '192.168.1.0/24', 25)", new ArrayType(IPPREFIX), ImmutableList.of("192.168.1.0/25", "192.168.1.128/25"));
assertFunction("IP_PREFIX_SUBNETS(IPPREFIX '192.168.0.0/24', 26)", new ArrayType(IPPREFIX), ImmutableList.of("192.168.0.0/26", "192.168.0.64/26", "192.168.0.128/26", "192.168.0.192/26"));
assertFunction("IP_PREFIX_SUBNETS(IPPREFIX '2A03:2880:C000::/34', 37)",
new ArrayType(IPPREFIX),
ImmutableList.of("2a03:2880:c000::/37", "2a03:2880:c800::/37", "2a03:2880:d000::/37", "2a03:2880:d800::/37", "2a03:2880:e000::/37", "2a03:2880:e800::/37", "2a03:2880:f000::/37", "2a03:2880:f800::/37"));
}

@Test
public void testIpPrefixSubnetsReturnSelf()
{
assertFunction("IP_PREFIX_SUBNETS(IPPREFIX '192.168.1.0/24', 24)", new ArrayType(IPPREFIX), ImmutableList.of("192.168.1.0/24"));
assertFunction("IP_PREFIX_SUBNETS(IPPREFIX '2804:431:b000::/38', 38)", new ArrayType(IPPREFIX), ImmutableList.of("2804:431:b000::/38"));
}

@Test
public void testIpPrefixSubnetsNewPrefixLengthLongerReturnsEmpty()
{
assertFunction("IP_PREFIX_SUBNETS(IPPREFIX '192.168.0.0/24', 23)", new ArrayType(IPPREFIX), ImmutableList.of());
assertFunction("IP_PREFIX_SUBNETS(IPPREFIX '64:ff9b::17/64', 48)", new ArrayType(IPPREFIX), ImmutableList.of());
}

@Test
public void testIpPrefixSubnetsInvalidPrefixLengths()
{
assertInvalidFunction("IP_PREFIX_SUBNETS(IPPREFIX '192.168.0.0/24', -1)", "Invalid prefix length for IPv4: -1");
assertInvalidFunction("IP_PREFIX_SUBNETS(IPPREFIX '192.168.0.0/24', 33)", "Invalid prefix length for IPv4: 33");
assertInvalidFunction("IP_PREFIX_SUBNETS(IPPREFIX '64:ff9b::17/64', -1)", "Invalid prefix length for IPv6: -1");
assertInvalidFunction("IP_PREFIX_SUBNETS(IPPREFIX '64:ff9b::17/64', 129)", "Invalid prefix length for IPv6: 129");
}
}

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