rst.erl

%% Copyright (c) 2010, Michael Santos <[email protected]>
%% 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
%% COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
%% INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
%% BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
%% LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
%% CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
%% LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
%% ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
%% POSSIBILITY OF SUCH DAMAGE.
-module(rst).
-export([
        start/2
    ]).

-include("epcap_net.hrl").

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

-record(state, {
        s,          % socket
        i,          % ifindex

        addr        % IP to exclude
    }).


start(Device, IP) when length(Device) < 16 ->
    {ok, FD} = packet:socket(),

    Interface = packet:ifindex(FD, Device),
    loop(#state{
            s = FD,
            i = Interface,
            addr = IP
        }).

loop(#state{s = S} = State) ->
    case procket:recvfrom(S, 65535) of
        nodata ->
            timer:sleep(10);
        {ok, Data} ->
            P = epcap_net:decapsulate(Data),
            filter(State, P);
        Error ->
            error_logger:error_report(Error)
    end,
    loop(State).


filter(#state{addr = IP}, [
    #ether{},
    #ipv4{
        saddr = Saddr,
        daddr = Daddr
    },
    #tcp{},
    _Payload
]) when Saddr =:= IP; Daddr =:= IP  ->
    ok;
filter(#state{
        s = Socket,
        i = Ifindex
    }, [
    #ether{
        shost = DM,
        dhost = SM
    },
    #ipv4{
        saddr = {DA1,DA2,DA3,DA4},
        daddr = {SA1,SA2,SA3,SA4}
    },
    #tcp{
        sport = DP,
        dport = SP,
        seqno = AckNo,
        ackno = SeqNo,
        syn = S,
        ack = A
    },
    _Payload
]) when S =:= 1; A =:= 1 ->
    Id = 0,
    TTL = 64,

    IPLen = 40,
    IPsum = packet:makesum(
        <<
        % IPv4 header
        4:4, 5:4, 0:8, IPLen:16,
        Id:16, 0:1, 1:1, 0:1,
        0:13, TTL:8, 6:8, 0:16,
        SA1:8, SA2:8, SA3:8, SA4:8,
        DA1:8, DA2:8, DA3:8, DA4:8
        >>
    ),

    TCPoff = 5,
    Win = 1024,
    PSH = 0,

    TCPsum = packet:makesum(
        <<
        % IP Pseudoheader
        SA1:8,SA2:8,SA3:8,SA4:8,
        DA1:8,DA2:8,DA3:8,DA4:8,
        0:8,
        6:8,                % Protocol: TCP
        (TCPoff * 4):16,

        % TCP Header
        SP:16, DP:16,
        SeqNo:32,
        AckNo:32,
        TCPoff:4, 0:4, 0:1, 0:1, 0:1, 0:1,
        PSH:1, 1:1, 0:1, 0:1, Win:16,
        0:16, 0:16
        >>
    ),

    packet:send(Socket, Ifindex, <<
        % Ethernet header
        DM:6/bytes,
        SM:6/bytes,
        16#08, 16#00,

        % IPv4 header
        4:4, 5:4, 0:8, IPLen:16,
        Id:16, 0:1, 1:1, 0:1,
        0:13, TTL:8, 6:8, IPsum:16,
        SA1:8, SA2:8, SA3:8, SA4:8,
        DA1:8, DA2:8, DA3:8, DA4:8,

        % TCP Header
        SP:16, DP:16,
        SeqNo:32,
        AckNo:32,
        TCPoff:4, 0:4, 0:1, 0:1, 0:1, 0:1,
        PSH:1, 1:1, 0:1, 0:1, Win:16,
        TCPsum:16, 0:16
        >>);
filter(_,_) ->
    ok.