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package cidr
import (
"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"
)
// SubnetsFunc is similar to SubnetFunc but calculates many consecutive subnet
// addresses at once, rather than just a single subnet extension.
var SubnetsFunc = 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
},
})
// Subnets calculates a sequence of consecutive subnet prefixes that may be of
// different prefix lengths under a common base prefix.
func Subnets(prefix cty.Value, newbits ...cty.Value) (cty.Value, error) {
args := make([]cty.Value, len(newbits)+1)
args[0] = prefix
copy(args[1:], newbits)
return SubnetsFunc.Call(args)
}
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