Import functions from Terraform

cty/function/stdlib/cidr.go

@@ -0,0 +1,218 @@
+package stdlib
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/apparentlymart/go-cidr/cidr"
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/function"
+	"github.com/zclconf/go-cty/cty/gocty"
+)
+
+// CidrHostFunc contructs a function that calculates a full host IP address
+// within a given IP network address prefix.
+var CidrHostFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "prefix",
+			Type: cty.String,
+		},
+		{
+			Name: "hostnum",
+			Type: cty.Number,
+		},
+	},
+	Type: function.StaticReturnType(cty.String),
+	Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
+		var hostNum int
+		if err := gocty.FromCtyValue(args[1], &hostNum); err != nil {
+			return cty.UnknownVal(cty.String), err
+		}
+		_, network, err := net.ParseCIDR(args[0].AsString())
+		if err != nil {
+			return cty.UnknownVal(cty.String), fmt.Errorf("invalid CIDR expression: %s", err)
+		}
+
+		ip, err := cidr.Host(network, hostNum)
+		if err != nil {
+			return cty.UnknownVal(cty.String), err
+		}
+
+		return cty.StringVal(ip.String()), nil
+	},
+})
+
+// CidrNetmaskFunc contructs a function that converts an IPv4 address prefix given
+// in CIDR notation into a subnet mask address.
+var CidrNetmaskFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "prefix",
+			Type: cty.String,
+		},
+	},
+	Type: function.StaticReturnType(cty.String),
+	Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
+		_, network, err := net.ParseCIDR(args[0].AsString())
+		if err != nil {
+			return cty.UnknownVal(cty.String), fmt.Errorf("invalid CIDR expression: %s", err)
+		}
+
+		return cty.StringVal(net.IP(network.Mask).String()), nil
+	},
+})
+
+// CidrSubnetFunc contructs a function that calculates a subnet address within
+// a given IP network address prefix.
+var CidrSubnetFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "prefix",
+			Type: cty.String,
+		},
+		{
+			Name: "newbits",
+			Type: cty.Number,
+		},
+		{
+			Name: "netnum",
+			Type: cty.Number,
+		},
+	},
+	Type: function.StaticReturnType(cty.String),
+	Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
+		var newbits int
+		if err := gocty.FromCtyValue(args[1], &newbits); err != nil {
+			return cty.UnknownVal(cty.String), err
+		}
+		var netnum int
+		if err := gocty.FromCtyValue(args[2], &netnum); err != nil {
+			return cty.UnknownVal(cty.String), err
+		}
+
+		_, network, err := net.ParseCIDR(args[0].AsString())
+		if err != nil {
+			return cty.UnknownVal(cty.String), fmt.Errorf("invalid CIDR expression: %s", err)
+		}
+
+		// For portability with 32-bit systems where the subnet number
+		// will be a 32-bit int, we only allow extension of 32 bits in
+		// one call even if we're running on a 64-bit machine.
+		// (Of course, this is significant only for IPv6.)
+		if newbits > 32 {
+			return cty.UnknownVal(cty.String), fmt.Errorf("may not extend prefix by more than 32 bits")
+		}
+
+		newNetwork, err := cidr.Subnet(network, newbits, netnum)
+		if err != nil {
+			return cty.UnknownVal(cty.String), err
+		}
+
+		return cty.StringVal(newNetwork.String()), nil
+	},
+})
+
+// CidrSubnetsFunc is similar to CidrSubnetFunc but calculates many consecutive
+// subnet addresses at once, rather than just a single subnet extension.
+var CidrSubnetsFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "prefix",
+			Type: cty.String,
+		},
+	},
+	VarParam: &function.Parameter{
+		Name: "newbits",
+		Type: cty.Number,
+	},
+	Type: function.StaticReturnType(cty.List(cty.String)),
+	Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
+		_, network, err := net.ParseCIDR(args[0].AsString())
+		if err != nil {
+			return cty.UnknownVal(cty.String), function.NewArgErrorf(0, "invalid CIDR expression: %s", err)
+		}
+		startPrefixLen, _ := network.Mask.Size()
+
+		prefixLengthArgs := args[1:]
+		if len(prefixLengthArgs) == 0 {
+			return cty.ListValEmpty(cty.String), nil
+		}
+
+		var firstLength int
+		if err := gocty.FromCtyValue(prefixLengthArgs[0], &firstLength); err != nil {
+			return cty.UnknownVal(cty.String), function.NewArgError(1, err)
+		}
+		firstLength += startPrefixLen
+
+		retVals := make([]cty.Value, len(prefixLengthArgs))
+
+		current, _ := cidr.PreviousSubnet(network, firstLength)
+		for i, lengthArg := range prefixLengthArgs {
+			var length int
+			if err := gocty.FromCtyValue(lengthArg, &length); err != nil {
+				return cty.UnknownVal(cty.String), function.NewArgError(i+1, err)
+			}
+
+			if length < 1 {
+				return cty.UnknownVal(cty.String), function.NewArgErrorf(i+1, "must extend prefix by at least one bit")
+			}
+			// For portability with 32-bit systems where the subnet number
+			// will be a 32-bit int, we only allow extension of 32 bits in
+			// one call even if we're running on a 64-bit machine.
+			// (Of course, this is significant only for IPv6.)
+			if length > 32 {
+				return cty.UnknownVal(cty.String), function.NewArgErrorf(i+1, "may not extend prefix by more than 32 bits")
+			}
+			length += startPrefixLen
+			if length > (len(network.IP) * 8) {
+				protocol := "IP"
+				switch len(network.IP) * 8 {
+				case 32:
+					protocol = "IPv4"
+				case 128:
+					protocol = "IPv6"
+				}
+				return cty.UnknownVal(cty.String), function.NewArgErrorf(i+1, "would extend prefix to %d bits, which is too long for an %s address", length, protocol)
+			}
+
+			next, rollover := cidr.NextSubnet(current, length)
+			if rollover || !network.Contains(next.IP) {
+				// If we run out of suffix bits in the base CIDR prefix then
+				// NextSubnet will start incrementing the prefix bits, which
+				// we don't allow because it would then allocate addresses
+				// outside of the caller's given prefix.
+				return cty.UnknownVal(cty.String), function.NewArgErrorf(i+1, "not enough remaining address space for a subnet with a prefix of %d bits after %s", length, current.String())
+			}
+
+			current = next
+			retVals[i] = cty.StringVal(current.String())
+		}
+
+		return cty.ListVal(retVals), nil
+	},
+})
+
+// CidrHost calculates a full host IP address within a given IP network address prefix.
+func CidrHost(prefix, hostnum cty.Value) (cty.Value, error) {
+	return CidrHostFunc.Call([]cty.Value{prefix, hostnum})
+}
+
+// CidrNetmask converts an IPv4 address prefix given in CIDR notation into a subnet mask address.
+func CidrNetmask(prefix cty.Value) (cty.Value, error) {
+	return CidrNetmaskFunc.Call([]cty.Value{prefix})
+}
+
+// CidrSubnet calculates a subnet address within a given IP network address prefix.
+func CidrSubnet(prefix, newbits, netnum cty.Value) (cty.Value, error) {
+	return CidrSubnetFunc.Call([]cty.Value{prefix, newbits, netnum})
+}
+
+// CidrSubnets calculates a sequence of consecutive subnet prefixes that may
+// be of different prefix lengths under a common base prefix.
+func CidrSubnets(prefix cty.Value, newbits ...cty.Value) (cty.Value, error) {
+	args := make([]cty.Value, len(newbits)+1)
+	args[0] = prefix
+	copy(args[1:], newbits)
+	return CidrSubnetsFunc.Call(args)
+}