Created
October 21, 2020 14:58
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Duplicate socket async reference
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#!/usr/bin/env escript | |
-module(duplicate_socket_async_ref). | |
-mode(compile). | |
-export([main/1]). | |
main([]) -> | |
{ok, ListenSocket, ListenPort} = create_listen_socket(), | |
spawn_link(fun () -> run_socket_acceptor(ListenSocket) end), | |
try_reproducing_the_issue(ListenPort, 0). | |
create_listen_socket() -> | |
{ok, Socket} = gen_tcp:listen(0, [{ifaddr, {127,0,0,1}}, | |
{active, false}, | |
{reuseaddr, true}, | |
{linger, {false, 0}}, | |
{recbuf, 16}]), | |
{ok, Port} = inet:port(Socket), | |
{ok, Socket, Port}. | |
run_socket_acceptor(ListenSocket) -> | |
case gen_tcp:accept(ListenSocket) of | |
{ok, ConnectionSocket} -> | |
handle_inbound_connection(ConnectionSocket), | |
run_socket_acceptor(ListenSocket); | |
{error, _} -> | |
run_socket_acceptor(ListenSocket) | |
end. | |
handle_inbound_connection(Socket) -> | |
case gen_tcp:recv(Socket, 0) of | |
{ok, _} -> | |
handle_inbound_connection(Socket); | |
{error, closed} -> | |
ok | |
end. | |
try_reproducing_the_issue(ListenPort, AttemptsSoFar) -> | |
UpdatedAttemptsSoFar = AttemptsSoFar + 1, | |
case attempt(ListenPort) of | |
{succeeded, FirstMsg, SecondMsg} -> | |
io:format("Succeeded after ~b attempt(s)~n" | |
"First message: ~p~n" | |
"Second message: ~p~n", | |
[UpdatedAttemptsSoFar, | |
FirstMsg, SecondMsg]); | |
failed -> | |
io:format("Failed (~b attempt(s) so far)~n", [UpdatedAttemptsSoFar]), | |
try_reproducing_the_issue(ListenPort, UpdatedAttemptsSoFar) | |
end. | |
attempt(ListenPort) -> | |
{ok, Socket} = connect(ListenPort), | |
ok = socket:setopt(Socket, socket, sndbuf, 16), | |
PacketLength = 128, | |
Packet = <<0:PacketLength/integer-unit:8>>, | |
Self = self(), | |
SocketCloserPid = spawn(fun () -> run_socket_closer(Self, Socket) end), | |
case socket:send(Socket, Packet, nowait) of | |
ok -> | |
_ = socket:close(Socket), | |
failed; | |
{ok, {_Unsent, {select_info, _, SelectRef}}} -> | |
await_socket_closer(SocketCloserPid), | |
await_occurence(Socket, SelectRef); | |
{select, {select_info, _, SelectRef}} -> | |
await_socket_closer(SocketCloserPid), | |
await_occurence(Socket, SelectRef); | |
{error, _} -> | |
_ = socket:close(Socket), | |
failed | |
end. | |
connect(ListenPort) -> | |
{ok, Socket} = socket:open(inet, stream, tcp), | |
BindAddr = #{family => inet, addr => {127,0,0,1}}, | |
{ok, _BindPort} = socket:bind(Socket, BindAddr), | |
ok = socket:setopt(Socket, socket, linger, abort), | |
ConnectAddr = #{family => inet, addr => {127,0,0,1}, port => ListenPort}, | |
ok = socket:connect(Socket, ConnectAddr), | |
{ok, Socket}. | |
run_socket_closer(Parent, Socket) -> | |
_ = socket:close(Socket), | |
_ = Parent ! {self(), done}. | |
await_socket_closer(Pid) -> | |
receive | |
{Pid, done} -> ok | |
end. | |
await_occurence(Socket, SelectRef) -> | |
case receive_socket_messages(Socket) of | |
[{'$socket', Socket, select, SelectRef} = FirstMsg, | |
{'$socket', Socket, abort, {SelectRef, closed}} = SecondMsg | |
] -> | |
{succeeded, FirstMsg, SecondMsg}; | |
[{'$socket', Socket, _, _}] -> | |
failed | |
end. | |
receive_socket_messages(Socket) -> | |
receive | |
{'$socket', Socket, _, _} = Msg -> | |
[Msg | receive_socket_messages(Socket)] | |
after | |
0 -> [] | |
end. |
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