Adding support for ServerIP context

caddyhttp/httpserver/context.go

@@ -84,6 +84,29 @@ func (c Context) IP() string {
 	return ip
 }
 
+// To mock the net.InterfaceAddrs from the test.
+var networkInterfacesFn = net.InterfaceAddrs
+
+// ServerIP gets the (local) IP address of the server.
+// TODO: The bind directive should be honored in this method (see PR #1474).
+func (c Context) ServerIP() string {
+	addrs, err := networkInterfacesFn()
+	if err != nil {
+		return ""
+	}
+
+	for _, address := range addrs {
+		// Validate the address and check if it's not a loopback
+		if ipnet, ok := address.(*net.IPNet); ok && !ipnet.IP.IsLoopback() {
+			if ipnet.IP.To4() != nil || ipnet.IP.To16() != nil {
+				return ipnet.IP.String()
+			}
+		}
+	}
+
+	return ""
+}
+
 // URI returns the raw, unprocessed request URI (including query
 // string and hash) obtained directly from the Request-Line of
 // the HTTP request.

caddyhttp/httpserver/context_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io/ioutil"
+	"net"
 	"net/http"
 	"net/url"
 	"os"
@@ -302,6 +303,44 @@ func TestIP(t *testing.T) {
 	}
 }
 
+type myIP string
+
+func (ip myIP) mockInterfaces() ([]net.Addr, error) {
+	a := net.ParseIP(string(ip))
+
+	return []net.Addr{
+		&net.IPNet{IP: a, Mask: nil},
+	}, nil
+}
+
+func TestServerIP(t *testing.T) {
+	context := getContextOrFail(t)
+
+	tests := []string{
+		// Test 0 - ipv4
+		"1.1.1.1",
+		// Test 1 - ipv6
+		"2001:db8:a0b:12f0::1",
+	}
+
+	for i, expectedIP := range tests {
+		testPrefix := getTestPrefix(i)
+
+		// Mock the network interface
+		ip := myIP(expectedIP)
+		networkInterfacesFn = ip.mockInterfaces
+		defer func() {
+			networkInterfacesFn = net.InterfaceAddrs
+		}()
+
+		actualIP := context.ServerIP()
+
+		if actualIP != expectedIP {
+			t.Errorf("%sExpected IP \"%s\", found \"%s\".", testPrefix, expectedIP, actualIP)
+		}
+	}
+}
+
 func TestURL(t *testing.T) {
 	context := getContextOrFail(t)