zgrab2 bind interface (https://github.com/zmap/zgrab2/issues/351)

bind_interface.patch

diff --git i/conn.go w/conn.go
index ef701c8..f8cfb29 100644
--- i/conn.go
+++ w/conn.go
@@ -5,7 +5,9 @@ import (
 	"errors"
 	"io"
 	"net"
+	"os"
 	"time"
+	"syscall"
 
 	"github.com/sirupsen/logrus"
 )
@@ -342,6 +344,27 @@ func (d *Dialer) SetDefaults() *Dialer {
 			DualStack: true,
 		}
 	}
+	if iface := os.Getenv("ZIFACE"); iface != "" {
+
+	    ief, err := net.InterfaceByName(iface)
+	    if err != nil {
+			panic("InterfaceByName(): interface specified does not exist")
+	    }
+
+		addrs, err := ief.Addrs()
+		if err != nil || len(addrs) == 0 {
+			panic("Addrs(): specified interface does not exist or has addresses assigned")
+		}
+		d.Dialer.LocalAddr = addrs[0]
+		d.Dialer.Control = func(network, address string, c syscall.RawConn) error {
+			return c.Control(func (fd uintptr)  {
+				if err := syscall.BindToDevice(int(fd), iface); err != nil {
+					panic("BindToDevice(): bind to interface failed")
+				}
+			})
+		}
+		
+	}
 	return d
 }