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initial commit for ip_prefix_subnets
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@matt-calder
matt-calder committed Sep 19, 2024
1 parent 626bb99 commit 014609a
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8 changes: 8 additions & 0 deletions presto-docs/src/main/sphinx/functions/ip.rst
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Expand Up @@ -70,3 +70,11 @@ IP Functions
SELECT is_private_ip(IPADDRESS '157.240.200.99'); -- false
SELECT is_private_ip(IPADDRESS '2a03:2880:f031:12:face:b00c:0:2'); -- false

.. 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}]
67 changes: 67 additions & 0 deletions presto-main/src/main/java/com/facebook/presto/operator/scalar/IpPrefixFunctions.java
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Expand Up @@ -52,6 +52,8 @@ public final class IpPrefixFunctions
{
private static final BigInteger TWO = BigInteger.valueOf(2);

private static final Block EMPTY_BLOCK = IPPREFIX.createBlockBuilder(null, 0).build();

/**
* Our definitions for what IANA considers not "globally reachable" are taken from the docs at
* https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml and
Expand Down Expand Up @@ -290,6 +292,71 @@ public static boolean isPrivateIpAddress(@SqlType(StandardTypes.IPADDRESS) Slice
return false;
}

@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
}

if (newPrefixCount == 0) {
return EMPTY_BLOCK;
}

BlockBuilder blockBuilder = IPPREFIX.createBlockBuilder(null, newPrefixCount);

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

private static List<Slice> generateMinIpPrefixes(BigInteger firstIpAddress, BigInteger lastIpAddress, int ipVersionMaxBits)
{
List<Slice> ipPrefixSlices = new ArrayList<>();
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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 @@ -287,4 +287,37 @@ public void testIsPrivateIpNull()
{
assertFunction("IS_PRIVATE_IP(NULL)", BOOLEAN, null);
}

@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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