path: root/lib/snmp/src/agent/snmpa_net_if.erl

%%
%% %CopyrightBegin%
%% 
%% Copyright Ericsson AB 2004-2014. All Rights Reserved.
%% 
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%% 
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%% 
%% %CopyrightEnd%
%%
-module(snmpa_net_if).

-behaviour(snmpa_network_interface).

-export([start_link/4,
	 info/1, 
	 verbosity/2]).
-export([get_log_type/1,  set_log_type/2]).
-export([get_request_limit/1, set_request_limit/2]).
-export([system_continue/3, system_terminate/4, system_code_change/4]).
-export([init/5]).
-export([filter_reset/1]).

-include("snmp_types.hrl").
-include("snmpa_internal.hrl").
-include("snmpa_atl.hrl").
-include("snmp_debug.hrl").
-include("snmp_verbosity.hrl").

-record(state, {parent, 
		note_store,
		master_agent, 
		usock, 
		usock_opts, 
		mpd_state, 
		log,
		reqs  = [], 
		debug = false,
		limit = infinity,
		rcnt  = [],
		filter,
		domain = snmpUDPDomain}).

-ifndef(default_verbosity).
-define(default_verbosity,silence).
-endif.

-define(DEFAULT_FILTER_MODULE, snmpa_net_if_filter).
-define(DEFAULT_FILTER_OPTS,   [{module, ?DEFAULT_FILTER_MODULE}]).

-define(ATL_SEQNO_INITIAL, 1).
-define(ATL_SEQNO_MAX,     2147483647).


%%%-----------------------------------------------------------------
%%% This module implements the default Network Interface part
%%% of the SNMP agent. It uses UDP, and read the agent.conf to find
%%% the UDP port.
%%%
%%% Opts = [Opt]
%%% Opt  = {verbosity,silence | log | debug} | 
%%%        {bind_to, bool()} |
%%%        {recbuf,integer()} |
%%%        {no_reuse, bool()} |
%%%        {req_limit, integer() | infinity}
%%%-----------------------------------------------------------------
start_link(Prio, NoteStore, MasterAgent, Opts) ->
    ?d("start_link -> entry with"
	"~n   Prio:        ~p"
	"~n   NoteStore:   ~p"
	"~n   MasterAgent: ~p"
	"~n   Opts:        ~p", [Prio, NoteStore, MasterAgent, Opts]),
    Args = [Prio, NoteStore, MasterAgent, self(), Opts],
    proc_lib:start_link(?MODULE, init, Args).

    
info(Pid) ->
    case call(Pid, info) of
	Info when is_list(Info) ->
	    Info;
	_ ->
	    []
    end.

verbosity(Pid, Verbosity) -> 
    Pid ! {verbosity, Verbosity}.

get_log_type(Pid) ->
    call(Pid, get_log_type).

set_log_type(Pid, NewType) ->
    call(Pid, {set_log_type, NewType}).

get_request_limit(Pid) ->
    call(Pid, get_request_limit).

set_request_limit(Pid, NewLimit) ->
    call(Pid, {set_request_limit, NewLimit}).

get_port() ->
    {value, UDPPort} = snmp_framework_mib:intAgentUDPPort(get),
    UDPPort.

get_address() ->
    {value, IPAddress} = snmp_framework_mib:intAgentIpAddress(get),
    IPAddress.

get_domain() ->
    case snmp_framework_mib:intAgentTransportDomain(get) of
	{value, Domain} ->
	    Domain;
	genErr ->
	    snmpUDPDomain
    end.

filter_reset(Pid) ->
    Pid ! filter_reset.


%%-----------------------------------------------------------------
%%-----------------------------------------------------------------

init(Prio, NoteStore, MasterAgent, Parent, Opts) ->
    ?d("init -> entry with"
      "~n   Prio:        ~p"
      "~n   NoteStore:   ~p"
      "~n   MasterAgent: ~p"
      "~n   Parent:      ~p"
      "~n   Opts:        ~p", [Prio, NoteStore, MasterAgent, Parent, Opts]),
    case (catch do_init(Prio, NoteStore, MasterAgent, Parent, Opts)) of
	{ok, State} ->
	    proc_lib:init_ack({ok, self()}),
	    try loop(State)
	    catch C:E ->
		    S = erlang:get_stacktrace(),
		    Fmt =
			"loop/1 EXCEPTION ~w:~w~n"
			"   ~p",
		    case C of
			exit ->
			    %% Externally killed, root cause is elsewhere
			    info_msg(Fmt, [C, E, S]);
			_ ->
			    error_msg(Fmt, [C, E, S])
		    end,
		    erlang:raise(C, E, S)
	    end;
	{error, Reason} ->
	    config_err("failed starting net-if: ~n~p", [Reason]),
	    proc_lib:init_ack({error, Reason});
	Error ->
	    config_err("failed starting net-if: ~n~p", [Error]),
	    proc_lib:init_ack({error, Error})
    end.

do_init(Prio, NoteStore, MasterAgent, Parent, Opts) ->
    process_flag(trap_exit, true),
    process_flag(priority, Prio),

    %% -- Verbosity --
    put(sname,nif),
    put(verbosity,get_verbosity(Opts)),
    ?vlog("starting",[]),

    %% -- Port and address --
    Domain = get_domain(),
    ?vdebug("domain: ~w",[Domain]),
    UDPPort = get_port(),
    ?vdebug("port: ~w",[UDPPort]),
    IPAddress = get_address(),
    ?vdebug("addr: ~w",[IPAddress]),

    %% -- Versions --
    Vsns = get_vsns(Opts),
    ?vdebug("vsns: ~w",[Vsns]),

    %% Flow control --
    Limit      = get_req_limit(Opts),
    ?vdebug("Limit: ~w", [Limit]),
    FilterOpts = get_filter_opts(Opts),
    FilterMod  = create_filter(FilterOpts),
    ?vdebug("FilterMod: ~w FilterOpts: ~p", [FilterMod,FilterOpts]),

    %% -- Audit trail log
    Log = create_log(),
    ?vdebug("Log: ~w",[Log]),


    %% -- Socket --
    IPOpts1 = ip_opt_bind_to_ip_address(Opts, IPAddress),
    IPOpts2 = ip_opt_no_reuse_address(Opts),
    IPOpts3 = ip_opt_recbuf(Opts),
    IPOpts4 = ip_opt_sndbuf(Opts),
    IPOpts  =
	[binary, snmp_conf:tdomain_to_family(Domain)
	 | IPOpts1 ++ IPOpts2 ++ IPOpts3 ++ IPOpts4],
    case gen_udp_open(UDPPort, IPOpts) of
	{ok, Sock} ->
	    MpdState = snmpa_mpd:init(Vsns),
	    init_counters(), 
	    active_once(Sock),
	    S = #state{parent       = Parent,
		       note_store   = NoteStore,
		       master_agent = MasterAgent, 
		       mpd_state    = MpdState,
		       usock        = Sock, 
		       usock_opts   = IPOpts,
		       log          = Log,
		       limit        = Limit,
		       filter       = FilterMod,
		       domain       = Domain},
	    ?vdebug("started with MpdState: ~p", [MpdState]),
	    {ok, S};
	{error, Reason} ->
	    ?vinfo("Failed to open UDP socket: ~p", [Reason]),
	    {error, {udp_open, UDPPort, Reason}}
    end.


create_log() ->
    case ets:lookup(snmp_agent_table, audit_trail_log) of
	[] ->
	    {undefined, []};
	[{audit_trail_log, AtlOpts}] ->
	    ?vtrace("AtlOpts: ~p", [AtlOpts]),
	    Type   = get_atl_type(AtlOpts),
	    Dir    = get_atl_dir(AtlOpts),
	    Size   = get_atl_size(AtlOpts),
	    Repair = get_atl_repair(AtlOpts),
	    Name   = ?audit_trail_log_name,
	    File   = filename:absname(?audit_trail_log_file, Dir),
	    case get_atl_seqno(AtlOpts) of
		true ->
		    Initial  = ?ATL_SEQNO_INITIAL,
		    Max      = ?ATL_SEQNO_MAX, 
		    Module   = snmpa_agent, 
		    Function = increment_counter, 
		    Args     = [atl_seqno, Initial, Max], 
		    SeqNoGen = {Module, Function, Args}, 
		    case snmp_log:create(Name, File, 
					 SeqNoGen, Size, Repair, true) of
			{ok, Log} ->
			    ?vdebug("log created: ~w", [Log]),
			    {Log, Type};
			{error, Reason} ->
			    throw({error, {create_log, Reason}})
		    end;
		_ ->
		    case snmp_log:create(Name, File, Size, Repair, true) of
			{ok, Log} ->
			    ?vdebug("log created: ~w", [Log]),
			    {Log, Type};
			{error, Reason} ->
			    throw({error, {create_log, Reason}})
		    end
	    end
    end.


create_filter(Opts) when is_list(Opts) ->
    case get_filter_module(Opts) of
	?DEFAULT_FILTER_MODULE = Mod ->
	    Mod;
	Module ->
	    snmpa_network_interface_filter:verify(Module),
	    Module
    end;
create_filter(BadOpts) ->
    throw({error, {bad_filter_opts, BadOpts}}).


log({_, []}, _, _, _) ->
    ok;
log({Log, Types}, 'set-request', Packet, Address) ->
    case lists:member(write, Types) of
	true ->
	    snmp_log:log(Log, Packet, format_address(Address));
	false ->
	    ok
    end;
log({Log, Types}, _, Packet, Address) ->
     case lists:member(read, Types) of
	true ->
	    snmp_log:log(Log, Packet, format_address(Address));
	false ->
	    ok
    end.

format_address(Address) ->
    iolist_to_binary(snmp_conf:mk_addr_string(Address)).



gen_udp_open(Port, Opts) ->
    case init:get_argument(snmp_fd) of
	{ok, [[FdStr]]} ->
	    Fd = list_to_integer(FdStr),
	    ?vdebug("gen_udp_open(~p, ~p) Fd: ~p",[Port,Opts,Fd]),
	    gen_udp:open(0, [{fd, Fd}|Opts]);
	error ->
	    case init:get_argument(snmpa_fd) of
		{ok, [[FdStr]]} ->
		    Fd = list_to_integer(FdStr),
		    ?vdebug("gen_udp_open(~p, ~p) Fd: ~p",[Port,Opts,Fd]),
		    gen_udp:open(0, [{fd, Fd}|Opts]);
		error ->
		    ?vdebug("gen_udp_open(~p, ~p)",[Port,Opts]),
		    gen_udp:open(Port, Opts)
	    end
    end.


loop(#state{domain = Domain} = S) ->
    receive
	{udp, _UdpId, Ip, Port, Packet} ->
	    ?vlog("got paket from ~w:~w",[Ip,Port]),
	    From = fix_filter_address(Domain, {Domain, {Ip, Port}}),
	    NewS = maybe_handle_recv(S, From, Packet),
	    loop(NewS);

	{info, ReplyRef, Pid} ->
	    Info = get_info(S),
	    Pid ! {ReplyRef, Info, self()},
	    loop(S);

	%% response (to get/get_next/get_bulk/set requests)
	{snmp_response, Vsn, RePdu, Type, ACMData, To, []} ->
	    ?vlog("reply pdu: "
		  "~n   ~s", 
		  [?vapply(snmp_misc, format, [256, "~w", [RePdu]])]),
	    NewS = maybe_handle_reply_pdu(S, Vsn, RePdu, Type, ACMData, To),
	    loop(NewS);

	%% Traps/notification
	{send_pdu, Vsn, Pdu, MsgData, TDomAddrs} ->
	    ?vdebug("send pdu:~n"
		    "   Pdu:       ~p~n"
		    "   TDomAddrs: ~p", [Pdu, TDomAddrs]),
	    NewS =
		maybe_handle_send_pdu(
		  S, Vsn, Pdu, MsgData, TDomAddrs, undefined),
	    loop(NewS);

	%% We dont use the extra-info at this time, ...
	{send_pdu, Vsn, Pdu, MsgData, TDomAddrs, _ExtraInfo} ->
	    ?vdebug("send pdu:~n"
		    "   Pdu:        ~p~n"
		    "   TDomAddrs: ~p", [Pdu, TDomAddrs]),
	    NewS =
		maybe_handle_send_pdu(
		  S, Vsn, Pdu, MsgData, TDomAddrs, undefined),
	    loop(NewS);

	%% Informs
	{send_pdu_req, Vsn, Pdu, MsgData, TDomAddrs, From} ->
	    ?vdebug("send pdu request:~n"
		    "   Pdu:       ~p~n"
		    "   TDomAddrs: ~p~n"
		    "   From:      ~p",
		    [Pdu, TDomAddrs, toname(From)]),
	    NewS =
		maybe_handle_send_pdu(
		  S, Vsn, Pdu, MsgData, TDomAddrs, From),
	    loop(NewS);

	%% We dont use the extra-info at this time, ...
	{send_pdu_req, Vsn, Pdu, MsgData, TDomAddrs, From, _ExtraInfo} ->
	    ?vdebug("send pdu request:~n"
		    "   Pdu:       ~p~n"
		    "   TDomAddrs: ~p~n"
		    "   From:      ~p",
		    [Pdu, TDomAddrs, toname(From)]),
	    NewS =
		maybe_handle_send_pdu(
		  S, Vsn, Pdu, MsgData, TDomAddrs, From),
	    loop(NewS);

	%% Discovery Inform
	%% <BACKWARD-COMPAT>
	{send_discovery, Pdu, MsgData, To, From} ->
	    ?vdebug("received send discovery request: "
		    "~n   Pdu:  ~p"
		    "~n   To:   ~p"
		    "~n   From: ~p", 
		    [Pdu, To, toname(From)]),
	    NewS = handle_send_discovery(S, Pdu, MsgData, To, From),
	    loop(NewS);
	%% </BACKWARD-COMPAT>

	%% Discovery Inform
	{send_discovery, Pdu, MsgData, To, From, ExtraInfo} ->
	    ?vdebug("received send discovery request: "
		    "~n   Pdu:       ~p"
		    "~n   To:        ~p"
		    "~n   From:      ~p"
		    "~n   ExtraInfo: ~p", 
		    [Pdu, To, toname(From), ExtraInfo]),
	    NewS = handle_send_discovery(S, Pdu, MsgData, To, From),
	    loop(NewS);

	{discarded_pdu, _Vsn, ReqId, _ACMData, Variable, _Extra} ->
	    ?vdebug("discard PDU: ~p", [Variable]),
	    snmpa_mpd:discarded_pdu(Variable),
	    NewS = update_req_counter_outgoing(S, ReqId),
	    loop(NewS);

	{get_log_type, ReplyRef, Pid} ->
	    ?vdebug("get log type: ~p", []),
	    #state{log = {_, LogType}} = S,
	    Pid ! {ReplyRef, {ok, LogType}, self()},
	    loop(S);

	{{set_log_type, NewType}, ReplyRef, Pid} ->
	    ?vdebug("set log type: ~p", [NewType]),
	    {NewState, Reply} = (catch handle_set_log_type(S, NewType)),
	    Pid ! {ReplyRef, Reply, self()},
	    loop(NewState);

	{get_request_limit, ReplyRef, Pid} ->
	    ?vdebug("get request limit: ~p", []),
	    #state{limit = Limit} = S,
	    Pid ! {ReplyRef, {ok, Limit}, self()},
	    loop(S);

	{{set_request_limit, NewLimit}, ReplyRef, Pid} ->
	    ?vdebug("set request limit: ~p", [NewLimit]),
	    {NewState, Reply} = (catch handle_set_request_limit(S, NewLimit)),
	    Pid ! {ReplyRef, Reply, self()},
	    loop(NewState);

	{disk_log, _Node, Log, Info} ->
	    ?vdebug("disk log event: ~p, ~p", [Log, Info]),
	    NewS = handle_disk_log(Log, Info, S),
	    loop(NewS);

	{verbosity, Verbosity} ->
	    ?vlog("verbosity: ~p -> ~p", [get(verbosity), Verbosity]),
	    put(verbosity, snmp_verbosity:validate(Verbosity)),
	    loop(S);

	filter_reset ->
	    reset_counters(),
	    loop(S);

	{'EXIT', Parent, Reason} when Parent == S#state.parent ->
	    ?vlog("parent (~p) exited: "
		  "~n   ~p", [Parent, Reason]),
	    exit(Reason);

	{'EXIT', Port, Reason} when Port == S#state.usock ->
	    UDPPort = get_port(),
	    NewS = 
		case gen_udp_open(UDPPort, S#state.usock_opts) of
		    {ok, Id} ->
			error_msg("Port ~p exited for reason"
				  "~n   ~p"
				  "~n   Re-opened (~p)", [Port, Reason, Id]),
			S#state{usock = Id};
		    {error, ReopenReason} ->
			error_msg("Port ~p exited for reason"
				  "~n   ~p"
				  "~n   Re-open failed with reason"
				  "~n   ~p", 
				  [Port, Reason, ReopenReason]),
			ok
		end,
	    loop(NewS);

	{'EXIT', Port, Reason} when is_port(Port) ->
	    error_msg("Exit message from port ~p for reason ~p~n", 
		      [Port, Reason]),
	    loop(S);

	{'EXIT', Pid, Reason} ->
	    ?vlog("~p exited: "
		  "~n   ~p", [Pid, Reason]),
	    NewS = clear_reqs(Pid, S),
	    loop(NewS);

	{system, From, Msg} ->
	    ?vdebug("system event ~p from ~p", [Msg, From]),
	    sys:handle_system_msg(Msg, From, S#state.parent, ?MODULE, [], S);

	_ ->
	    loop(S)
    end.


update_req_counter_incomming(#state{limit = infinity, usock = Sock} = S, _) ->
    active_once(Sock), %% No limit so activate directly
    S; 
update_req_counter_incomming(#state{limit = Limit, 
				    rcnt  = RCnt, 
				    usock = Sock} = S, Rid) 
  when length(RCnt) + 1 == Limit ->
    %% Ok, one more and we are at the limit.
    %% Just make sure we are not already processing this one...
    case lists:member(Rid, RCnt) of
	false ->
	    %% We are at the limit, do _not_ activate socket
	    S#state{rcnt = [Rid|RCnt]};
	true ->
	    active_once(Sock),
	    S
    end;
update_req_counter_incomming(#state{rcnt  = RCnt, 
				    usock = Sock} = S, Rid) ->
    active_once(Sock),
    case lists:member(Rid, RCnt) of
	false ->
	    S#state{rcnt = [Rid|RCnt]};
	true ->
	    S
    end.


update_req_counter_outgoing(#state{limit = infinity} = S, _Rid) ->
    %% Already activated (in the incoming function)
    S;
update_req_counter_outgoing(#state{limit = Limit, 
				   rcnt  = RCnt, 
				   usock = Sock} = S, Rid) 
  when length(RCnt) == Limit ->
    ?vtrace("handle_req_counter_outgoing(~w) -> entry with"
	"~n   Rid:          ~w"
	"~n   length(RCnt): ~w", [Limit, Rid, length(RCnt)]),
    case lists:delete(Rid, RCnt) of
	NewRCnt when length(NewRCnt) < Limit ->
	    ?vtrace("update_req_counter_outgoing -> "
		"passed below limit: activate", []),
	    active_once(Sock),
	    S#state{rcnt = NewRCnt};
	_ ->
	    S
    end;
update_req_counter_outgoing(#state{limit = Limit, rcnt = RCnt} = S, 
			    Rid) ->
    ?vtrace("handle_req_counter_outgoing(~w) -> entry with"
	"~n   Rid:          ~w"
	"~n   length(RCnt): ~w", [Limit, Rid, length(RCnt)]),
    NewRCnt = lists:delete(Rid, RCnt),
    S#state{rcnt = NewRCnt}.
    

maybe_handle_recv(
  #state{usock = Sock, filter = FilterMod} = S, From, Packet) ->
    {From_1, From_2} = From,
    case
	try FilterMod:accept_recv(From_1, From_2)
	catch
	    Class:Exception ->
		error_msg(
		  "FilterMod:accept_recv(~p, ~p) crashed: ~w:~w~n    ~p",
		  [From_1,From_2,Class,Exception,erlang:get_stacktrace()]),
		true
	end
    of
	false ->
	    %% Drop the received packet 
	    inc(netIfMsgInDrops),
	    active_once(Sock),
	    S;
	Other ->
	    case Other of
		true ->
		    ok;
		_ ->
		    error_msg(
		      "FilterMod:accept_recv(~p, ~p) returned: ~p",
		      [From_1,From_2,Other])
	    end,
	    handle_recv(S, From, Packet)
    end.

handle_discovery_response(_From, #pdu{request_id = ReqId} = Pdu,
			  ManagerEngineId, 
			  #state{usock = Sock, reqs = Reqs} = S) ->
    case lists:keysearch(ReqId, 1, S#state.reqs) of
	{value, {_, Pid}} ->
	    active_once(Sock),
	    Pid ! {snmp_discovery_response_received, Pdu, ManagerEngineId},
	    NReqs = lists:keydelete(ReqId, 1, Reqs),
	    S#state{reqs = NReqs};
	_ ->
	    %% Ouch, timeout? resend?
	    S
    end.

handle_recv(
  #state{usock      = Sock,
	 mpd_state  = MpdState,
	 note_store = NS,
	 log        = Log} = S, From, Packet) ->
    put(n1, erlang:now()),
    LogF =
	fun(Type, Data) ->
		log(Log, Type, Data, From)
	end,
    case (catch snmpa_mpd:process_packet(
		  Packet, From, MpdState, NS, LogF)) of
	{ok, _Vsn, Pdu, _PduMS, {discovery, ManagerEngineId}} ->
	    handle_discovery_response(From, Pdu, ManagerEngineId, S);

	{ok, _Vsn, Pdu, _PduMS, discovery} ->
	    handle_discovery_response(From, Pdu, undefined, S);

	{ok, Vsn, Pdu, PduMS, ACMData} ->
	    ?vlog("got pdu ~s", 
		  [?vapply(snmp_misc, format, [256, "~w", [Pdu]])]),
	    %% handle_recv_pdu(From, Vsn, Pdu, PduMS, ACMData, S);
	    maybe_handle_recv_pdu(From, Vsn, Pdu, PduMS, ACMData, S);

	{discarded, Reason} ->
	    ?vlog("packet discarded for reason: ~s",
		  [?vapply(snmp_misc, format, [256, "~w", [Reason]])]),
	    active_once(Sock),
	    S;

	{discarded, Reason, ReportPacket} ->
	    ?vlog("sending report for reason: "
		"~n   ~s", 
		[?vapply(snmp_misc, format, [256, "~w", [Reason]])]),
	    (catch udp_send(S#state.usock, From, ReportPacket)),
	    active_once(Sock),
	    S;
	
	{discovery, ReportPacket} ->
	    ?vlog("sending discovery report", []),
	    (catch udp_send(S#state.usock, From, ReportPacket)),
	    active_once(Sock),
	    S;
	
	Error ->
	    error_msg("processing of received message failed: "
                      "~n   ~p", [Error]),
	    active_once(Sock),
	    S
    end.

maybe_handle_recv_pdu(
  From, Vsn,
  #pdu{type = Type} = Pdu, PduMS, ACMData,
  #state{usock = Sock, filter = FilterMod} = S) ->
    {From_1, From_2} = From,
    case
	try FilterMod:accept_recv_pdu(From_1, From_2, Type)
	catch
	    Class:Exception ->
		error_msg(
		  "FilterMod:accept_recv_pdu(~p, ~p, ~p) crashed: ~w:~w~n"
		  "    ~p",
		  [From_1,From_2,Type,Class,Exception,
		   erlang:get_stacktrace()]),
		true
	end
    of
	false ->
	    inc(netIfPduInDrops),
	    active_once(Sock),
	    ok;
	Other ->
	    case Other of
		true ->
		    ok;
		_ ->
		    error_msg(
		      "FilterMod:accept_recv_pdu(~p, ~p, ~p) returned: ~p",
		      [From_1,From_2,Type,Other])
	    end,
	    handle_recv_pdu(From, Vsn, Pdu, PduMS, ACMData, S)
    end.

handle_recv_pdu(
  From, Vsn,
  #pdu{type = 'get-response'} = Pdu, _PduMS, _ACMData,
  #state{usock = Sock} = S) ->
    active_once(Sock),
    handle_response(Vsn, Pdu, From, S),
    S;
handle_recv_pdu(From, Vsn, #pdu{request_id = Rid, type = Type} = Pdu,
		PduMS, ACMData, #state{master_agent = Pid} = S) 
  when ((Type =:= 'get-request') orelse
	(Type =:= 'get-next-request') orelse
	(Type =:= 'get-bulk-request')) ->
    ?vtrace("handle_recv_pdu -> received get (~w)", [Type]),
    Pid ! {snmp_pdu, Vsn, Pdu, PduMS, ACMData, From, []},
    update_req_counter_incomming(S, Rid);
handle_recv_pdu(From, Vsn, Pdu, PduMS, ACMData,
		#state{usock = Sock, master_agent = Pid} = S) ->
    ?vtrace("handle_recv_pdu -> received other request", []),
    active_once(Sock),
    Pid ! {snmp_pdu, Vsn, Pdu, PduMS, ACMData, From, []},
    S.


maybe_handle_reply_pdu(
  #state{filter = FilterMod, domain = Domain} = S, Vsn,
  #pdu{request_id = Rid} = Pdu,
  Type, ACMData, To) ->

    S1 = update_req_counter_outgoing(S, Rid),
    Addresses = [fix_filter_address(Domain, To)],
    case
	try
	    FilterMod:accept_send_pdu(Addresses, Type)
	catch
	    Class:Exception ->
		error_msg(
		  "FilterMod:accept_send_pdu(~p, ~p) crashed: ~w:~w~n    ~p",
		  [Addresses,Type,Class,Exception,erlang:get_stacktrace()]),
		true
	end
    of
	false ->
	    inc(netIfPduOutDrops),
	    ok;
	Other ->
	    case Other of
		true ->
		    ok;
		_ ->
		    error_msg(
		      "FilterMod:accept_send_pdu(~p, ~p) returned: ~p",
		      [Addresses,Type,Other])
	    end,
	    handle_reply_pdu(S1, Vsn, Pdu, Type, ACMData, To)
    end,
    S1.

handle_reply_pdu(#state{log = Log} = S, Vsn, Pdu, Type, ACMData, To) ->
    LogF =
	fun(Type2, Data) ->
		log(Log, Type2, Data, To)
	end,
    case (catch snmpa_mpd:generate_response_msg(Vsn, Pdu, Type,
						ACMData, LogF)) of
	{ok, Packet} ->
	    ?vinfo("time in agent: ~w mysec", [time_in_agent()]),
	    maybe_udp_send(S, To, Packet);
	{discarded, Reason} ->
	    ?vlog("handle_reply_pdu -> "
		  "~n   reply discarded for reason: ~s", 
		[?vapply(snmp_misc, format, [256, "~w", [Reason]])]),
	    ok;
	{'EXIT', Reason} ->
	    user_err("failed generating response message: "
		     "~nPDU: ~p~n~p", [Pdu, Reason])
    end.



maybe_handle_send_pdu(
  #state{filter = FilterMod, domain = Domain} = S,
  Vsn, Pdu, MsgData, TDomAddrSecs, From) ->

    ?vtrace("maybe_handle_send_pdu -> entry with~n"
	    "   FilterMod: ~p~n"
	    "   TDomAddrSecs: ~p", [FilterMod, TDomAddrSecs]),

    DomAddrSecs = snmpa_mpd:process_taddrs(TDomAddrSecs),
    AddressesToFilter =
	[case Domain of
	     snmpUDPDomain ->
		 case DAS of
		     {{Dom, Addr}, _SecData}
		       when is_atom(Dom) -> % v3
			 Addr;
		     {Dom, Addr}
		       when is_atom(Dom) -> % v1 & v2
			 Addr
		 end;
	     _ ->
		 case DAS of
		     {{Dom, _Addr} = DomAddr, _SecData}
		       when is_atom(Dom) -> % v3
			 DomAddr;
		     {Dom, _Addr} = DomAddr
		       when is_atom(Dom) -> % v1 & v2
			 DomAddr
		 end
	 end || DAS <- DomAddrSecs],
    Type = pdu_type_of(Pdu),

    case
	try FilterMod:accept_send_pdu(AddressesToFilter, Type)
	catch
	    Class:Exception ->
		error_msg(
		  "FilterMod:accept_send_pdu(~p, ~p) crashed: ~w:~w~n    ~p",
		  [AddressesToFilter,Type,
		   Class,Exception,erlang:get_stacktrace()]),
		true
	end
    of
	false ->
	    inc(netIfPduOutDrops),
	    ok;
	true ->
	    handle_send_pdu(S, Vsn, Pdu, MsgData, DomAddrSecs, From);
	FilteredAddresses when is_list(FilteredAddresses) ->
	    MergedDomAddrSecs =
		[DAS ||
		    DAS <- DomAddrSecs,
		    lists:member(
		      case Domain of
			  snmpUDPDomain ->
			      case DAS of
				  {{Dom, Addr}, _SData}
				    when is_atom(Dom) -> % v3
				      Addr;
				  {Dom, Addr}
				    when is_atom(Dom) -> % v1 & v2
				      Addr
			      end;
			  true ->
			      case DAS of
				  {{Dom, _Addr} = DomAddr, _SData}
				    when is_atom(Dom) -> % v3
				      DomAddr;
				  {Dom, _Addr} = DomAddr
				    when is_atom(Dom) -> % v1 & v2
				      DomAddr
			      end
		      end, FilteredAddresses)],
	    ?vtrace("maybe_handle_send_pdu -> MergedDomAddrSecs:~n"
		    "   ~p", [MergedDomAddrSecs]),
	    handle_send_pdu(S, Vsn, Pdu, MsgData, MergedDomAddrSecs, From);
	Other ->
	    error_msg(
	      "FilterMod:accept_send_pdu(~p, ~p) returned: ~p",
	      [AddressesToFilter,Type,Other]),
	    handle_send_pdu(S, Vsn, Pdu, MsgData, DomAddrSecs, From)
    end.

handle_send_pdu(
  #state{note_store = NS} = S, Vsn, Pdu, MsgData, DomAddrSecs, From) ->
    
    ?vtrace("handle_send_pdu -> entry with~n"
	    "   Pdu:         ~p~n"
	    "   DomAddrSecs: ~p", [Pdu, DomAddrSecs]),

    case (catch snmpa_mpd:generate_msg(
		  Vsn, NS, Pdu, MsgData, DomAddrSecs)) of
	{ok, Addresses} ->
	    do_handle_send_pdu(S, Pdu, Addresses);
	{discarded, Reason} ->
	    ?vlog("handle_send_pdu -> "
		  "~n   PDU ~p not sent due to ~p", [Pdu, Reason]),
	    ok;
        {'EXIT', Reason} ->
            user_err("failed generating message: "
                     "~nPDU: ~p~n~p", [Pdu, Reason]),
            ok
    end,
    case From of
	undefined ->
	    S;
	Pid ->
	    ?vtrace("link to ~p and add to request list", [Pid]),
	    link(Pid),
	    NReqs = snmp_misc:keyreplaceadd(
		      Pid, 2, S#state.reqs, {Pdu#pdu.request_id, From}),
	    S#state{reqs = NReqs}
    end.


handle_send_discovery(
  #state{note_store = NS,
	 log        = Log,
	 usock      = Sock,
	 reqs       = Reqs} = S,
  #pdu{type = Type,
       request_id = ReqId} = Pdu,
  MsgData, To, From) ->
    
    ?vtrace("handle_send_discovery -> entry with"
	    "~n   Pdu:     ~p"
	    "~n   MsgData: ~p"
	    "~n   To:      ~p"
	    "~n   From:    ~p", [Pdu, MsgData, To, From]),

    case (catch snmpa_mpd:generate_discovery_msg(NS, Pdu, MsgData, To)) of
	{ok, {Domain, Address, Packet}} ->
	    log(Log, Type, Packet, {Domain, Address}),
	    udp_send(Sock, {Domain, Address}, Packet),
	    ?vtrace("handle_send_discovery -> sent (~w)", [ReqId]),
	    NReqs = snmp_misc:keyreplaceadd(From, 2, Reqs, {ReqId, From}),
	    S#state{reqs = NReqs};
	{discarded, Reason} ->
	    ?vlog("handle_send_discovery -> "
		  "~n   Discovery PDU ~p not sent due to ~p", [Pdu, Reason]),
	    ok;
        {'EXIT', Reason} ->
            user_err("failed generating discovery message: "
                     "~n   PDU:    ~p"
		     "~n   Reason: ~p", [Pdu, Reason]),
            ok
    end.


do_handle_send_pdu(S, #pdu{type = Type} = Pdu, Addresses) ->
    do_handle_send_pdu(S, Type, Pdu, Addresses);
do_handle_send_pdu(S, Trap, Addresses) ->
    do_handle_send_pdu(S, trappdu, Trap, Addresses).

do_handle_send_pdu(S, Type, Pdu, Addresses) ->
    case (catch do_handle_send_pdu1(S, Type, Addresses)) of
	{Reason, Sz} ->
	    error_msg("Cannot send message "
		      "~n   size:   ~p"
		      "~n   reason: ~p"
		      "~n   pdu:    ~p",
		      [Sz, Reason, Pdu]);
	_ ->
	    ok
    end.

do_handle_send_pdu1(S, Type, Addresses) ->
    lists:foreach(
      fun ({Domain, Address, Packet}) when is_binary(Packet) ->
	      ?vdebug(
		 "[~w] sending packet:~n"
		 "   size: ~p~n"
		 "   to:   ~p", [Domain, sz(Packet), Address]),
	      To = {Domain, Address},
	      maybe_udp_send(S, To, Packet);
	  ({Domain, Address, {Packet, LogData}}) when is_binary(Packet) ->
	      ?vdebug(
		 "[~w] sending encrypted packet:~n"
		 "   size: ~p~n"
		 "   to:   ~p", [Domain, sz(Packet), Address]),
	      To = {Domain, Address},
	      maybe_udp_send(S, To, Packet, Type, LogData)
      end,
      Addresses).

handle_response(Vsn, Pdu, From, S) ->
    case lists:keysearch(Pdu#pdu.request_id, 1, S#state.reqs) of
	{value, {_, Pid}} ->
	    ?vdebug("handle_response -> "
		    "~n   send response to receiver ~p", [Pid]),
	    Pid ! {snmp_response_received, Vsn, Pdu, From};
	_ ->
	    ?vdebug("handle_response -> "
		    "~n   No receiver available for response pdu", [])
    end.

maybe_udp_send(
  #state{usock  = Sock, filter = FilterMod, domain = Domain},
  To, Packet) ->
    {To_1, To_2} = fix_filter_address(Domain, To),
    case
	try FilterMod:accept_send(To_1, To_2)
	catch
	    Class:Exception ->
		error_msg(
		  "FilterMod:accept_send(~p, ~p) crashed: ~w:~w~n    ~p",
		  [To_1,To_2,Class,Exception,erlang:get_stacktrace()]),
		true
	end
    of
	false ->
	    inc(netIfMsgOutDrops),
	    ok;
	Other ->
	    case Other of
		true ->
		    ok;
		_ ->
		    error_msg(
		      "FilterMod:accept_send(~p, ~p) returned: ~p",
		      [To_1,To_2,Other])
	    end,
	    %% XXX should be some kind of lookup of domain to socket
	    (catch udp_send(Sock, To, Packet))
    end.

maybe_udp_send(
  #state{
     log    = Log,
     usock  = Sock,
     filter = FilterMod,
     domain = Domain},
  To, Packet, Type, _LogData) ->
    {To_1, To_2} = fix_filter_address(Domain, To),
    case
	try FilterMod:accept_send(To_1, To_2)
	catch
	    Class:Exception ->
		error_msg(
		  "FilterMod:accept_send(~p, ~p) crashed for: ~w:~w~n    ~p",
		  [To_1,To_2,Class,Exception,erlang:get_stacktrace()]),
		true
	end
    of
	false ->
	    inc(netIfMsgOutDrops),
	    ok;
	Other ->
	    case Other of
		true ->
		    ok;
		_ ->
		    error_msg(
		      "FilterMod:accept_send(~p, ~p) returned: ~p",
		      [To_1,To_2,Other])
	    end,
	    log(Log, Type, Packet, To),
	    (catch udp_send(Sock, To, Packet))
    end.

udp_send(UdpId, To, B) ->
    %% XXX should be some kind of lookup of domain to socket
    {Ip, Port} =
	case To of
	    {Domain, Addr} when is_atom(Domain) ->
		Addr;
	    {_, P} = Addr when is_integer(P) ->
		Addr
	end,
    case (catch gen_udp:send(UdpId, Ip, Port, B)) of
	{error, emsgsize} ->
	    %% From this message we cannot recover, so exit sending loop
	    throw({emsgsize, sz(B)});
	{error, ErrorReason} ->
	    error_msg("[error] cannot send message "
		      "(destination: ~p:~p, size: ~p, reason: ~p)",
		      [Ip, Port, sz(B), ErrorReason]);
	{'EXIT', ExitReason} ->
	    error_msg("[exit] cannot send message "
		      "(destination: ~p:~p, size: ~p, reason: ~p)",
		      [Ip, Port, sz(B), ExitReason]);
	_ ->
	    ok
    end.

sz(L) when is_list(L) -> length(L);
sz(B) when is_binary(B) -> size(B);
sz(_) -> undefined.


handle_disk_log(_Log, {wrap, NoLostItems}, State) ->
    ?vlog("Audit Trail Log - wrapped: ~w previously logged items where lost", 
	  [NoLostItems]),
    State;
handle_disk_log(_Log, {truncated, NoLostItems}, State) ->
    ?vlog("Audit Trail Log - truncated: ~w items where lost when truncating", 
	  [NoLostItems]),
    State;
handle_disk_log(_Log, full, State) ->
    error_msg("Failure to write to Audit Trail Log (full)", []),
    State;
handle_disk_log(_Log, {error_status, ok}, State) ->
    State;
handle_disk_log(_Log, {error_status, {error, Reason}}, State) ->
    error_msg("Error status received from Audit Trail Log: "
	      "~n~p", [Reason]),
    State;
handle_disk_log(_Log, _Info, State) ->
    State.


clear_reqs(Pid, S) ->
    NReqs = lists:keydelete(Pid, 2, S#state.reqs),
    S#state{reqs = NReqs}.


toname(P) when is_pid(P) ->
    case process_info(P, registered_name) of
	{registered_name, Name} ->
	    Name;
	_ ->
	    P
    end;
toname(Else) ->
    Else.


active_once(Sock) ->
    ?vtrace("activate once", []),
    inet:setopts(Sock, [{active, once}]).


%% If the agent uses legacy snmpUDPDomain e.g has not set
%% intAgentTransportDomain, then make sure
%% snmpa_network_interface_filter gets legacy arguments
%% to not break backwards compatibility.
%%
fix_filter_address(snmpUDPDomain, {Domain, Addr})
  when Domain =:= snmpUDPDomain;
       Domain =:= transportDomainUdpIpv4 ->
    Addr;
fix_filter_address(_AgentDomain, {Domain, _} = Address)
  when is_atom(Domain) ->
    Address;
fix_filter_address(snmpUDPDomain, {_, Port} = Addr)
  when is_integer(Port) ->
    Addr.

%%%-----------------------------------------------------------------

handle_set_log_type(#state{log = {Log, OldValue}} = State, NewType) 
  when (Log /= undefined) ->
    NewValue =
	case NewType of
	    read ->
		[read];
	    write ->
		[write];
	    read_write ->
		[read,write];
	    _ ->
		throw({State, {error, {bad_atl_type, NewType}}})
	end,
    NewState = State#state{log = {Log, NewValue}},
    OldType =
	case {lists:member(read, OldValue),
	      lists:member(write, OldValue)} of
	    {true, true} ->
		read_write;
	    {true, false} ->
		read;
	    {false, true} ->
		write;
	    {false, false} ->
		throw({State, {error, {bad_atl_type, OldValue}}})
	end,
    {NewState, {ok, OldType}};
handle_set_log_type(State, _NewType) ->
    {State, {error, not_enabled}}.


handle_set_request_limit(#state{limit = OldLimit} = State, NewLimit) 
  when ((is_integer(NewLimit) andalso (NewLimit >= 0)) orelse 
	(NewLimit == infinity)) ->
    NewState = State#state{limit = NewLimit},
    {NewState, {ok, OldLimit}};
handle_set_request_limit(State, BadLimit) ->
    {State, {error, {bad_request_limit, BadLimit}}}.


%%%-----------------------------------------------------------------
%%% System messages
%%%-----------------------------------------------------------------
system_continue(_Parent, _Dbg, S) ->
    loop(S).

system_terminate(Reason, _Parent, _Dbg, #state{log = Log}) ->
    ?vlog("system-terminate -> entry with"
	  "~n   Reason: ~p", [Reason]),
    do_close_log(Log),
    exit(Reason).

system_code_change(OldState, _Module, _OldVsn, downgrade_to_pre_4_16) ->
    {OldLog, Type} = OldState#state.log, 
    NewLog   = snmp_log:downgrade(OldLog), 
    NewState = OldState#state{log = {NewLog, Type}}, 
    {ok, NewState};

system_code_change(OldState, _Module, _OldVsn, upgrade_from_pre_4_16) ->
    Initial  = ?ATL_SEQNO_INITIAL,
    Max      = ?ATL_SEQNO_MAX, 
    Module   = snmpa_agent, 
    Function = increment_counter, 
    Args     = [atl_seqno, Initial, Max], 
    SeqNoGen = {Module, Function, Args}, 
    {OldLog, Type} = OldState#state.log, 
    NewLog   = snmp_log:upgrade(OldLog, SeqNoGen), 
    NewState = OldState#state{log = {NewLog, Type}}, 
    {ok, NewState};

system_code_change(S, _Module, _OldVsn, _Extra) ->
    {ok, S}.

do_close_log({undefined, []}) ->
    ok;
do_close_log({Log, _}) ->
    (catch snmp_log:sync(Log)),
    (catch snmp_log:close(Log)),
    ok;
do_close_log(_) ->
    ok.


%%%-----------------------------------------------------------------
%%% DEBUG FUNCTIONS
%%%-----------------------------------------------------------------
time_in_agent() ->
    subtr(erlang:now(), get(n1)).

subtr({X1,Y1,Z1}, {X1,Y1,Z2}) ->
    Z1 - Z2;
subtr({X1,Y1,Z1}, {X1,Y2,Z2}) ->
    ((Y1-Y2) * 1000000) + (Z1 - Z2);
subtr({X1,Y1,Z1}, {X2,Y2,Z2}) ->
    ((X1 - X2) * 1000000000000) + ((Y1 - Y2) * 1000000) + (Z1 - Z2).


%% ----------------------------------------------------------------

pdu_type_of(#pdu{type = Type}) ->
    Type;
pdu_type_of(TrapPdu) when is_record(TrapPdu, trappdu) ->
    trap.


%%-----------------------------------------------------------------
%% Counter functions
%%-----------------------------------------------------------------

init_counters() -> 
    F = fun(Counter) -> maybe_create_counter(Counter) end,
    lists:map(F, counters()).

reset_counters() -> 
    F = fun(Counter) -> init_counter(Counter) end,
    lists:map(F, counters()).

maybe_create_counter(Counter) ->
    case ets:lookup(snmp_agent_table, Counter) of
	[_] -> ok;
	_ -> init_counter(Counter)
    end.

init_counter(Counter) -> 
    ets:insert(snmp_agent_table, {Counter, 0}).

counters() ->
    [
     netIfMsgOutDrops,
     netIfMsgInDrops,
     netIfPduOutDrops,
     netIfPduInDrops
    ].

inc(Name) -> 
    ets:update_counter(snmp_agent_table, Name, 1).

get_counters() ->
    Counters = counters(),
    get_counters(Counters, []).

get_counters([], Acc) ->
    lists:reverse(Acc);
get_counters([Counter|Counters], Acc) ->
    case ets:lookup(snmp_agent_table, Counter) of
	[CounterVal] ->
	    get_counters(Counters, [CounterVal|Acc]);
	_ ->
	    get_counters(Counters, Acc)
    end.


%% ----------------------------------------------------------------

ip_opt_bind_to_ip_address(Opts, Ip) ->
    case get_bind_to_ip_address(Opts) of
	true ->
	    [{ip, Ip}];
	_ ->
	    []
    end.

ip_opt_no_reuse_address(Opts) ->
    case get_no_reuse_address(Opts) of
	false ->
	    [{reuseaddr, true}];
	_ ->
	    []
    end.

ip_opt_recbuf(Opts) ->
    case get_recbuf(Opts) of
	use_default ->
	    [];
	Sz ->
	    [{recbuf, Sz}]
    end.

ip_opt_sndbuf(Opts) ->
    case get_sndbuf(Opts) of
	use_default ->
	    [];
	Sz ->
	    [{sndbuf, Sz}]
    end.


%% ----------------------------------------------------------------

get_atl_type(Opts) ->
    case snmp_misc:get_option(type, Opts, read_write) of
	read_write ->
	    [read,write];
	write ->
	    [write];
	read ->
	    [read]
    end.
	
get_atl_dir(Opts) ->
    snmp_misc:get_option(dir, Opts).

get_atl_size(Opts) ->
    snmp_misc:get_option(size, Opts).

get_atl_repair(Opts) ->
    snmp_misc:get_option(repair, Opts, true).

get_atl_seqno(Opts) ->
    snmp_misc:get_option(seqno, Opts, false).

get_verbosity(Opts) ->
    snmp_misc:get_option(verbosity, Opts, ?default_verbosity).

get_vsns(Opts) ->
    snmp_misc:get_option(versions, Opts, [v1, v2, v3]).

get_req_limit(O) ->
    snmp_misc:get_option(req_limit, O, infinity).

get_filter_opts(O) ->
    snmp_misc:get_option(filter, O, []).

get_filter_module(O) ->
    snmp_misc:get_option(module, O, ?DEFAULT_FILTER_MODULE).

get_recbuf(Opts) -> 
    snmp_misc:get_option(recbuf, Opts, use_default).

get_sndbuf(Opts) -> 
    snmp_misc:get_option(sndbuf, Opts, use_default).

get_no_reuse_address(Opts) -> 
    snmp_misc:get_option(no_reuse, Opts, false).

get_bind_to_ip_address(Opts) ->
    snmp_misc:get_option(bind_to, Opts, false).


%% ----------------------------------------------------------------

error_msg(F,A) -> 
    ?snmpa_error("NET-IF server: " ++ F, A).

info_msg(F,A) ->
    ?snmpa_info("NET-IF server: " ++ F, A).

%% --- 

user_err(F, A) ->
    snmpa_error:user_err(F, A).
 
config_err(F, A) ->
    snmpa_error:config_err(F, A).
 

%% ----------------------------------------------------------------

call(Pid, Req) ->
    ReplyRef = make_ref(),
    Pid ! {Req, ReplyRef, self()},
    receive 
	{ReplyRef, Reply, Pid} ->
	    Reply
    after 5000 ->
	    {error, timeout}
    end.

		       
%% ----------------------------------------------------------------

get_info(#state{usock = Id, reqs = Reqs}) ->
    ProcSize = proc_mem(self()),
    PortInfo = get_port_info(Id),
    Counters = get_counters(),
    [{reqs,           Reqs}, 
     {counters,       Counters}, 
     {process_memory, ProcSize}, 
     {port_info,      PortInfo}].

proc_mem(P) when is_pid(P) ->
    case (catch erlang:process_info(P, memory)) of
	{memory, Sz} when is_integer(Sz) ->
	    Sz;
	_ ->
	    undefined
    end.
%% proc_mem(_) ->
%%     undefined.

get_port_info(Id) ->
    PortInfo = 
	case (catch erlang:port_info(Id)) of
	    PI when is_list(PI) ->
		[{port_info, PI}];
	    _ ->
		[]
	end,
    PortStatus = 
	case (catch prim_inet:getstatus(Id)) of
	    {ok, PS} ->
		[{port_status, PS}];
	    _ ->
		[]
	end,
    PortAct = 
	case (catch inet:getopts(Id, [active])) of
	    {ok, PA} ->
		[{port_act, PA}];
	    _ ->
		[]
	end,
    PortStats = 
	case (catch inet:getstat(Id)) of
	    {ok, Stat} ->
		[{port_stats, Stat}];
	    _ ->
		[]
	end,
    IfList = 
	case (catch inet:getif(Id)) of
	    {ok, IFs} ->
		[{interfaces, IFs}];
	    _ ->
		[]
	end,
    BufSz = 
	case (catch inet:getopts(Id, [recbuf, sndbuf])) of
	    {ok, Sz} ->
		[{buffer_size, Sz}];
	    _ ->
		[]
	end,
    [{socket, Id}] ++ 
	IfList ++ 
	PortStats ++ 
	PortInfo ++ 
	PortStatus ++ 
	PortAct ++ 
	BufSz.


%% ----------------------------------------------------------------

% i(F) ->
%     i(F, []).

% i(F, A) ->
%     io:format("~p: " ++ F ++ "~n", [?MODULE|A]).