packet.erl

%% Copyright (c) 2010, Michael Santos <michael.santos@gmail.com>
%% All rights reserved.
%%
%% Redistribution and use in source and binary forms, with or without
%% modification, are permitted provided that the following conditions
%% are met:
%%
%% Redistributions of source code must retain the above copyright
%% notice, this list of conditions and the following disclaimer.
%%
%% Redistributions in binary form must reproduce the above copyright
%% notice, this list of conditions and the following disclaimer in the
%% documentation and/or other materials provided with the distribution.
%%
%% Neither the name of the author nor the names of its contributors
%% may be used to endorse or promote products derived from this software
%% without specific prior written permission.
%%
%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
%% "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
%% LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
%% FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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%% BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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%% POSSIBILITY OF SUCH DAMAGE.
-module(packet).
-export([
        socket/0,
        makesum/1,
        ifindex/2,
        send/3
    ]).

-define(SIOCGIFINDEX, 16#8933).
-define(PF_PACKET, 17).

socket() ->
    procket:listen(0, [{protocol, 16#0008}, {type, raw}, {family, packet}]).

ifindex(Socket, Dev) ->
    {ok, <<_Ifname:16/bytes, Ifr:8, _/binary>>} = procket:ioctl(Socket,
        ?SIOCGIFINDEX,
        list_to_binary([
                Dev, <<0:((16*8) - (length(Dev)*8)), 0:128>>
            ])),
    Ifr.

send(S, Interface, Packet) ->
    procket:sendto(S, Packet, 0,
        <<
        ?PF_PACKET:16/native,   % sll_family: PF_PACKET
        0:16,                   % sll_protocol: Physical layer protocol
        Interface: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
        >>).

makesum(Hdr) -> 16#FFFF - checksum(Hdr).

checksum(Hdr) ->
    lists:foldl(fun compl/2, 0, [ W || <<W:16>> <= Hdr ]).

compl(N) when N =< 16#FFFF -> N;
compl(N) -> (N band 16#FFFF) + (N bsr 16).
compl(N,S) -> compl(N+S).