run: go fmt; use 'MAIN' for the address portion to use system's prima…

…ry interface

cmd.go

@@ -23,17 +23,17 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/alecthomas/kingpin/v2"
 	"github.com/olekukonko/tablewriter"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
-	"github.com/alecthomas/kingpin/v2"
 )
 
-const version = "0.7.1"
+const version = "0.7.2"
 
 var (
 	list        = kingpin.Flag("int", "list local interface IP addresses").Short('i').Bool()
-	from        = kingpin.Flag("from", "from IP address:port").Short('f').String()
+	from        = kingpin.Flag("from", "from IP address:port; use 'MAIN' for the address portion to use system's primary interface").Short('f').String()
 	to          = kingpin.Flag("to", "to IP address:port").Short('t').String()
 	examples    = kingpin.Flag("examples", "show command line example and then exit").Bool()
 	versionOnly = kingpin.Flag("version", "show version and then exit").Bool()
@@ -298,6 +298,10 @@ func main() {
 		os.Exit(1)
 	}
 
+	if strings.HasPrefix(*from, "MAIN:") {
+		*from = strings.Replace(*from, "MAIN", getMainNic(), 1)
+	}
+
 	if len(*loc) > 0 && 0 == *distance {
 		kingpin.FatalUsage("--distance must be used with --loc")
 		os.Exit(1)

docker_build_image.sh

@@ -69,8 +69,7 @@ if [ $# -eq 0 ] ; then
     exit 1
 fi
 
-TAG=$1
-IMG=gofwd:${TAG}
+IMG=$1
 BUND="ca-bundle.crt"
 SC="ssl/certs/"
 GF="gofwd"

geoip.go

@@ -28,9 +28,11 @@ type ipInfoResult struct {
 getIpInfo issues a web query to ipinfo.io
 The JSON result is converted to an ipInfoResult struct
 Args:
+
 	ip: an IPv4 address
 
 Returns:
+
 	an ipInfoResult struct containing the information returned by the service
 */
 func getIPInfo(ip string) (ipInfoResult, error) {
@@ -122,9 +124,11 @@ func validateLocation(localGeoIP ipInfoResult, remoteGeoIP ipInfoResult, restric
 latlon2coord converts a string such as "36.0525,-79.107" to a tuple of floats
 
 Args:
+
 	latlon: a string in "lat, lon" format
 
 Returns:
+
 	a tuple in (float64, float64) format
 */
 func latlon2coord(latlon string) (float64, float64, error) {
@@ -147,9 +151,10 @@ func hsin(theta float64) float64 {
 }
 
 // HaversineDistance returns the distance (in miles) between two points of
-//	 a given longitude and latitude relatively accurately (using a spherical
-//	 approximation of the Earth) through the Haversin Distance Formula for
-//	 great arc distance on a sphere with accuracy for small distances
+//
+//	a given longitude and latitude relatively accurately (using a spherical
+//	approximation of the Earth) through the Haversin Distance Formula for
+//	great arc distance on a sphere with accuracy for small distances
 //
 // point coordinates are supplied in degrees and converted into rad. in the func
 //

nics.go

@@ -66,6 +66,30 @@ func extractIPAddrs(ifaceName string, allAddresses []net.Addr, brief bool) ([]st
 	return allIPv4, allIPv6
 }
 
+func getMainNic() string {
+	adapters, err := net.Interfaces()
+	if err != nil {
+		return "0.0.0.0"
+	}
+
+	for _, iface := range adapters {
+		allAddresses, err := iface.Addrs()
+		if err != nil {
+			return "0.0.0.0"
+		}
+
+		allIPv4, allIPv6 := extractIPAddrs(iface.Name, allAddresses, true)
+		if len(allIPv4) == 1 && strings.ToLower(iface.Name) == "eth0" {
+			for _, ipWithMask := range allIPv4 {
+				ip := strings.Split(ipWithMask, "/")
+				return ip[0]
+			}
+		}
+	}
+
+	return "0.0.0.0"
+}
+
 func networkInterfaces(brief bool, debug bool) ([]string, []string, error) {
 	adapters, err := net.Interfaces()
 	if err != nil {