package funcs import ( "fmt" "math/big" "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 *big.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.HostBig(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 *big.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) } newNetwork, err := cidr.SubnetBig(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) }