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erldns_encoder.erl
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erldns_encoder.erl
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%% Copyright (c) 2012-2020, DNSimple Corporation
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
%% @doc Safe response encoding, where exceptions will not result in a full
%% system crash.
-module(erldns_encoder).
-include_lib("dns_erlang/include/dns_records.hrl").
-export([
encode_message/1,
encode_message/2
]).
%% @doc Encode the DNS message into its binary representation.
%%
%% Note that if the erldns catch_exceptions property is set in the
%% configuration, then this function should never throw an
%% exception.
-spec encode_message(dns:message()) -> dns:message_bin().
encode_message(Response) ->
case application:get_env(erldns, catch_exceptions) of
{ok, false} ->
dns:encode_message(Response);
_ ->
try dns:encode_message(Response) of
M ->
M
catch
Exception:Reason ->
erldns_events:notify({?MODULE, encode_message_error, {Exception, Reason, Response}}),
encode_message(build_error_response(Response))
end
end.
%% @doc Encode the DNS message into its binary representation. Use the
%% Opts argument to pass in encoding options.
%%
%% Note that if the erldns catch_exceptions property is set in the
%% configuration, then this function should never throw an
%% exception.
-spec encode_message(dns:message(), [dns:encode_message_opt()]) ->
{false, dns:message_bin()}
| {true, dns:message_bin(), dns:message()}
| {false, dns:message_bin(), dns:tsig_mac()}
| {true, dns:message_bin(), dns:tsig_mac(), dns:message()}.
encode_message(Response, Opts) ->
case application:get_env(erldns, catch_exceptions) of
{ok, false} ->
dns:encode_message(Response, Opts);
_ ->
try dns:encode_message(Response, Opts) of
M ->
M
catch
Exception:Reason ->
erldns_events:notify({?MODULE, encode_message_error, {Exception, Reason, Response, Opts}}),
{false, encode_message(build_error_response(Response))}
end
end.
% Private functions
%% Populate a response with a servfail error
build_error_response(Response) when is_record(Response, dns_message) ->
build_error_response(Response, ?DNS_RCODE_SERVFAIL);
build_error_response({_, Response}) ->
build_error_response(Response, ?DNS_RCODE_SERVFAIL).
build_error_response(Response, Rcode) ->
Response#dns_message{
anc = 0,
auc = 0,
adc = 0,
qr = true,
aa = true,
rc = Rcode,
answers = [],
authority = [],
additional = []
}.