feat(connection): configurable TCP keepalive

[paulozulato]

Fixes https://emqx.atlassian.net/browse/EMQX-9852

Summary

🤖 Generated by Copilot at 7f73c08

This pull request adds support for TCP keepalive on Mac OS and configurable TCP keepalive options for listeners. It modifies the emqx_connection, emqx_schema, emqx_gateway_api_listeners, and emqx_listeners modules, as well as the emqx_mqtt_SUITE test case and the emqx_schema.hocon file. It also fixes some socket errors and refactors some code for readability and consistency.

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Changed lines covered in coverage report
• Change log has been added to changes/{ce,ee}/(feat|perf|fix)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• If there should be document changes, a PR to emqx-docs.git is sent, or a jira ticket is created to follow up
• Schema changes are backward compatible

Checklist for CI (.github/workflows) changes

• If changed package build workflow, pass this action (manual trigger)
• Change log has been added to changes/ dir for user-facing artifacts update

[zmstone]

Suggested change

	default => "none",
	default => <<"none">>,

[paulozulato]

Ack

[zmstone]

maybe move this hunk to a small function (take get_active_n function as an example).

also, we should not try to set tcp-ka for QUIC connections.

ok = maybe_set_tcp_keepalive(Listener),

maybe_set_tcp_keepalive({quic, _}) -> ok;
maybe_set_tcp_keepalive({Type, Id}) ->
    Conf = mqx_config:get_listener_conf(ListenerType, ListenerId, [tcp_options, keepalive], <<"none">>),
    case iolist_to_binary(Conf) of
        <<"none">> ->
            ok;
        Value ->
            %% the value is already validated by schema, so we do not validate it again.
            {Idle, Interval, Probes} = emqx_schema:parse_tcp_keepalive(Value),
            async_set_keepalive(Idle, Interfval, Probe)
    end.

-module(emqx_schema).
-export([parse_tcp_keepalive/1]).

%% @doc This function is used as value validator and also run-time parser.
parse_tcp_keepalive(Str) ->
    try
        [Idle, Interval, Probes]  = binary:split(iolist_to_binary(Str), <<",">>, [global]),
        %% use 10 times the Linux defaults as range limit
        IdleInt = parse_ka_int(Idle, "Idle", 1, 7200_0),
        IntervalInt = parse_ka_int(Interval, "Interva",  75_0),
        ProbesInt = parse_ka_int(Probe, "Probes", 1, 9_0),
        {IdleInt, IntervalInt, ProbesInt}
    catch
        error:_ ->
           throw(#{reason => “Not comma separated positive integers of 'Idle,Interval,Probes' format", value => Str})
    end.

parse_ka_int(Bin, Name, Min, Max) ->
    I = binary_to_integer(Bin),
    case I >= Min andalso I =< Max of
        true ->
            I;
        false ->
            Msg = io_lib:format("TCP-Keepalive '~s' value must be in the rage of [~p, ~p].", [Name, Min, Max]),
            throw(#{reason => lists:flatten(Msg), value => I}
    end.

[paulozulato]

Ack

[zmstone]

Suggested change

	case Value of
	"none" ->
	ok;
	_ ->
	try
	[IdleStr, IntervalStr, ProbesStr] = string:tokens(Value, ", "),
	_ = list_to_integer(IdleStr),
	_ = list_to_integer(IntervalStr),
	_ = list_to_integer(ProbesStr),
	ok
	catch
	_:_ ->
	{error, "value does not contain 3 comma-separate integer values"}
	end
	end.
	case iolist_to_binary(Value) of
	<<"none">> ->
	ok;
	_ ->
	_ = parse_tcp_keealive(Value),
	ok
	end.

[paulozulato]

Ack

[coveralls]

Pull Request Test Coverage Report for Build 5194657467

• 7 of 18 (38.89%) changed or added relevant lines in 1 file are covered.
• 42 unchanged lines in 18 files lost coverage.
• Overall coverage decreased (-0.04%) to 81.675%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
apps/emqx/src/emqx_connection.erl	7	18	38.89%

Files with Coverage Reduction	New Missed Lines	%
apps/emqx_authn/src/enhanced_authn/emqx_enhanced_authn_scram_mnesia.erl	1	85.29%
apps/emqx_gateway_exproto/src/emqx_exproto_gcli.erl	1	64.15%
apps/emqx_gateway/src/emqx_gateway_schema.erl	1	88.89%
apps/emqx/src/emqx_broker.erl	1	88.2%
apps/emqx/src/emqx_channel.erl	1	87.69%
apps/emqx/src/emqx_cm.erl	1	92.47%
apps/emqx/src/emqx_config_handler.erl	1	95.57%
apps/emqx/src/emqx_flapping.erl	1	85.45%
apps/emqx/src/emqx_limiter/src/emqx_limiter_schema.erl	1	81.48%
apps/emqx/src/emqx_router_helper.erl	1	87.04%

Totals
Change from base Build 5189817718:	-0.04%
Covered Lines:	29105
Relevant Lines:	35635

---

💛 - Coveralls

[yanzhiemq]

Enhancements

• Added support for configuring TCP keep-alive in MQTT/TCP and MQTT/SSL listeners.

[yanzhiemq]

增强

• 支持在 MQTT/TCP 和 MQTT/SSL 监听器中配置 TCP keep-alive。