msantos
commented
8 years ago On Thu, Jan 21, 2016 at 09:37:21AM -0800, amuessig wrote:
Hey,
I am trying to build up a middlebox device which is reading packets from a socket, check some stuff like IP address and (if the check matches) send the packet out through the socket Later, I will be migrating the socket, thus I need to use raw sockets My code is as follow:
init({Parent, Port}) -> register(?MODULE,self()), proc_lib:init_ack(Parent, {ok, self()}), {ok, ListenSock} = procket:open(Port, [{protocol, 16#0008}, {type, raw}, {family, packet}]), P = erlang:open_port({fd, ListenSock, ListenSock}, [binary, stream]), accept(P)How can I bind the opened socket to a interface? I tried this: {ok, ListenSock} = procket:open(Port, [{protocol, 16#0008}, {type, raw}, {family, packet}, {interface, "vnf-eth0"}]), but it didn't work
procket calls setsockopt(SO_BINDTODEVICE) for the interface option. According to socket(7):
SO_BINDTODEVICE
Note that this works only for some socket types, particularly
AF_INET sockets. It is not supported for packet sockets (use normal
bind(2) there).So we need to use bind(2). There's a version of bind() in the procket PF_PACKET module that works with packet sockets:
{ok, ListenSock} = procket:open(Port, [{protocol, 16#0008}, {type, raw}, {family, packet}]),
IfIndex = packet:ifindex(ListenSock, "vnf-eth0"),
ok = packet:bind(ListenSock, IfIndex)Furthermore, trying the listening method, I am not sure how to write back the data: accept(ListenSock) -> case gen_tcp:accept(ListenSock) of {ok, Client} -> io:format("foo~n"), Tmp = rule_database:lookup_ruletable(Client), if Tmp -> %if the lookup is positive, send it back {ok, } = procket:sendTo(ListenSock); true -> % otherwise don't send it gen_tcp:close(Client) %erlang:port_close(Client) end, accept(ListenSock); _Error -> ok end
Any suggestions/help? Thanks!
Because we're using PF_PACKET sockets, we can't call gen_tcp:accept/1. The ethernet frame will be sent to our process as port data. The frame can be parsed using pkt (https://github.com/msantos/pkt).
For sending the frame, use packet:send/3.
Something like this:
accept(ListenSock, IfIndex, Port) ->
receive
{Port, {data, Data}} ->
Frame = pkt:decapsulate(Data),
Tmp = rule_database:lookup_rule_table(Frame),
if Tmp ->
%if the lookup is positive, send it back
% XXX will return {ok, Size} on partial write
ok = packet:send(ListenSock, Ifindex, Data);
true ->
% otherwise don't send it
% Could generate a RST here
%gen_tcp:close(Client)
%erlang:port_close(Client)
end,
accept(ListenSocket, IfIndex, Port);
_Error ->
ok
end.If the device is in the middle between the client and server, instead of closing the socket you could generate a RST in both directions to shut down the connection.
If any of that isn't clear or if you have any questions, please let me know!
amuessig
Hey,
I am trying to build up a middlebox device which is reading packets from a socket, check some stuff like IP address and (if the check matches) send the packet out through the socket. Later, I will be migrating the socket, thus I need to use raw sockets. My code is as follow:
How can I bind the opened socket to a interface? I tried this: {ok, ListenSock} = procket:open(Port, [{protocol, 16#0008}, {type, raw}, {family, packet}, {interface, "vnf-eth0"}]), but it didn't work.
Furthermore, trying the listening method, I am not sure how to write back the data..:
Any suggestions/help? Thanks!