From 05c180e7b28c4659b55e5bf1ebc4847e5b62230e Mon Sep 17 00:00:00 2001 From: jwijenbergh Date: Mon, 12 Aug 2024 11:33:52 +0200 Subject: Util: Add a function to calculate the gateway --- util/util.go | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 util/util.go (limited to 'util/util.go') diff --git a/util/util.go b/util/util.go new file mode 100644 index 0000000..c7816df --- /dev/null +++ b/util/util.go @@ -0,0 +1,33 @@ +// package util defines public utility functions to be used by applications +// these are outside of the client package as they can be used even if a client hasn't been created yet +package util + +import ( + "net" + + "github.com/eduvpn/eduvpn-common/i18nerr" +) + +// CalculateGateway takes a CIDR encoded subnet `cidr` and returns the gateway and an error +func CalculateGateway(cidr string) (string, error) { + _, ipn, err := net.ParseCIDR(cidr) + if err != nil { + return "", i18nerr.WrapInternalf(err, "failed to parse CIDR for calculating gateway: %v", cidr) + } + + ret := make(net.IP, len(ipn.IP)) + copy(ret, ipn.IP) + + for i := len(ret) - 1; i >= 0; i-- { + ret[i]++ + if ret[i] > 0 { + break + } + } + + if !ipn.Contains(ret) { + return "", i18nerr.Newf("IP network does not contain incremented IP: %v", ret) + } + + return ret.String(), nil +} -- cgit v1.2.3