File 2471-Fix-channel-close-procedure-when-the-peer-dies-or-ou.patch of Package erlang
From af56b4d0837474070283fc0e1cb0b517fa3bda53 Mon Sep 17 00:00:00 2001
From: Yaroslav Maslennikov <ymaslenn@cisco.com>
Date: Fri, 22 Nov 2024 18:15:14 +0100
Subject: [PATCH 1/5] Fix channel close procedure when the peer dies or our
handler goes down
---
lib/ssh/src/ssh_connection.erl | 16 ++++++++---
lib/ssh/src/ssh_connection_handler.erl | 37 +++++++++++++++++++-------
2 files changed, 41 insertions(+), 12 deletions(-)
diff --git a/lib/ssh/src/ssh_connection.erl b/lib/ssh/src/ssh_connection.erl
index c82dd67197..3493809362 100644
--- a/lib/ssh/src/ssh_connection.erl
+++ b/lib/ssh/src/ssh_connection.erl
@@ -769,14 +769,24 @@ handle_msg(#ssh_msg_channel_request{recipient_channel = ChannelId,
?DEC_BIN(Err, _ErrLen),
?DEC_BIN(Lang, _LangLen)>> = Data,
case ssh_client_channel:cache_lookup(Cache, ChannelId) of
- #channel{remote_id = RemoteId} = Channel ->
+ #channel{remote_id = RemoteId, sent_close = SentClose} = Channel ->
{Reply, Connection} = reply_msg(Channel, Connection0,
{exit_signal, ChannelId,
binary_to_list(SigName),
binary_to_list(Err),
binary_to_list(Lang)}),
- ChannelCloseMsg = channel_close_msg(RemoteId),
- {[{connection_reply, ChannelCloseMsg}|Reply], Connection};
+ %% Send 'channel-close' only if it has not been sent yet
+ %% by e.g. our side also closing the channel or going down
+ %% and(!) update the cache
+ %% so that the 'channel-close' is not sent twice
+ if not SentClose ->
+ CloseMsg = channel_close_msg(RemoteId),
+ ssh_client_channel:cache_update(Cache,
+ Channel#channel{sent_close = true}),
+ {[{connection_reply, CloseMsg}|Reply], Connection};
+ true ->
+ {Reply, Connection}
+ end;
_ ->
%% Channel already closed by peer
{[], Connection0}
diff --git a/lib/ssh/src/ssh_connection_handler.erl b/lib/ssh/src/ssh_connection_handler.erl
index 44a0a0f1ea..ceb353c3f3 100644
--- a/lib/ssh/src/ssh_connection_handler.erl
+++ b/lib/ssh/src/ssh_connection_handler.erl
@@ -1085,12 +1085,20 @@ handle_event({call,From}, {recv_window, ChannelId}, StateName, D)
handle_event({call,From}, {close, ChannelId}, StateName, D0)
when ?CONNECTED(StateName) ->
+ %% Send 'channel-close' only if it has not been sent yet
+ %% e.g. when 'exit-signal' was received from the peer
+ %% and(!) we update the cache so that we remember what we've done
case ssh_client_channel:cache_lookup(cache(D0), ChannelId) of
- #channel{remote_id = Id} = Channel ->
+ #channel{remote_id = Id, sent_close = false} = Channel ->
D1 = send_msg(ssh_connection:channel_close_msg(Id), D0),
- ssh_client_channel:cache_update(cache(D1), Channel#channel{sent_close = true}),
+ ssh_client_channel:cache_update(cache(D1),
+ Channel#channel{sent_close = true}),
{keep_state, D1, [cond_set_idle_timer(D1), {reply,From,ok}]};
- undefined ->
+ _ ->
+ %% Here we match a channel which has already sent 'channel-close'
+ %% AND possible cases of 'broken cache' i.e. when a channel
+ %% disappeared from the cache, but has not been properly shut down
+ %% The latter would be a bug, but hard to chase
{keep_state_and_data, [{reply,From,ok}]}
end;
@@ -1251,15 +1259,26 @@ handle_event(info, {timeout, {_, From} = Request}, _,
%%% Handle that ssh channels user process goes down
handle_event(info, {'DOWN', _Ref, process, ChannelPid, _Reason}, _, D) ->
Cache = cache(D),
- ssh_client_channel:cache_foldl(
- fun(#channel{user=U,
- local_id=Id}, Acc) when U == ChannelPid ->
- ssh_client_channel:cache_delete(Cache, Id),
- Acc;
+ %% Here we first collect the list of channel id's handled by the process
+ %% Do NOT remove them from the cache - they are not closed yet!
+ Channels = ssh_client_channel:cache_foldl(
+ fun(#channel{user=U} = Channel, Acc) when U == ChannelPid ->
+ [Channel | Acc];
(_,Acc) ->
Acc
end, [], Cache),
- {keep_state, D, cond_set_idle_timer(D)};
+ %% Then for each channel where 'channel-close' has not been sent yet
+ %% we send 'channel-close' and(!) update the cache so that we remember
+ %% what we've done
+ D2 = lists:foldl(
+ fun(#channel{remote_id = Id, sent_close = false} = Channel, D0) ->
+ D1 = send_msg(ssh_connection:channel_close_msg(Id), D0),
+ ssh_client_channel:cache_update(cache(D1),
+ Channel#channel{sent_close = true}),
+ D1;
+ (_, D0) -> D0
+ end, D, Channels),
+ {keep_state, D2, cond_set_idle_timer(D2)};
handle_event({timeout,idle_time}, _Data, _StateName, D) ->
case ssh_client_channel:cache_info(num_entries, cache(D)) of
--
2.43.0
