packet: add bind/2

Binding a PF_PACKET socket to an interface will return packets only for
that device (rather than all interfaces on the host).

src/packet.erl

@@ -45,6 +45,7 @@
         ipv4address/2,
         macaddress/2,
         promiscuous/2,
+        bind/2,
         bindtodevice/2,
         filter/2, unfilter/1, unfilter/2,
         send/3
@@ -225,6 +226,30 @@ promiscuous(Socket, Ifindex) ->
         >>).
 
 
+%%-------------------------------------------------------------------------
+%% Bind a PF_PACKET socket to an interface.
+%%-------------------------------------------------------------------------
+bind(Socket, Ifindex) ->
+    Sockaddr_ll = <<
+        ?PF_PACKET:16/native,   % sll_family: PF_PACKET
+        0:16,                   % sll_protocol: Physical layer protocol
+        Ifindex:32/native,      % sll_ifindex: Interface number
+        0:16,                   % sll_hatype: Header type
+        0:8,                    % sll_pkttype: Packet type
+        0:8,                    % sll_halen: address length
+        0:8,                    % sll_addr[8]: physical layer address
+        0:8,                    % sll_addr[8]: physical layer address
+        0:8,                    % sll_addr[8]: physical layer address
+        0:8,                    % sll_addr[8]: physical layer address
+        0:8,                    % sll_addr[8]: physical layer address
+        0:8,                    % sll_addr[8]: physical layer address
+        0:8,                    % sll_addr[8]: physical layer address
+        0:8                     % sll_addr[8]: physical layer address
+    >>,
+
+    procket:bind(Socket, Sockaddr_ll).
+
+
 %%-------------------------------------------------------------------------
 %% Bind socket to interface. Equivalent to the {interface, Device} option
 %% but requires running Erlang with heightened privs (CAP_NET_RAW)