Clients disconnected on SIGHUP

[ckrey]

I found a way to reproduce the problem reported in #1494:

[ckrey]

Minimal mosquitto.conf:

pid_file /tmp/mosquitto.pid
persistence true
persistence_location /tmp/
allow_anonymous false
log_dest file /tmp/mosquitto.log
autosave_interval 10
persistent_client_expiration 1w
connection_messages true
log_type all
log_timestamp true

1. run mosquitto with that config
2. run mosquitto_sub -u user1 -P password1 -i client1 -c -t abc -v
3. abort mosquitto_sub
4. stop mosquitto
5. restart mosquitto with that config
6. now send mosquitto a SIGHUP signal

mosquitto.log`:

...
1575150018: Reloading config.
1575150018: Client client1 disconnected.
...

The code triggering the disconnect is in security_default.c/mosquitto_security_apply_default
context__disconnect then calls session_expiry__add.

The result is:
If there are inactive clients and mosquitto is once restarted, the daily SIGHUPs used for log rotation
cause the session expiry mechanism to be reset every day.

Probably context__disconnect should return if the context is already disconnected.

[ckrey]

P.S. to find the problem, I extended db_dump.c a bit:

diff --git a/src/db_dump/db_dump.c b/src/db_dump/db_dump.c
index 45eb80a..4605d6f 100644
--- a/src/db_dump/db_dump.c
+++ b/src/db_dump/db_dump.c
@@ -45,6 +45,8 @@ struct client_data
        int subscription_size;
        int messages;
        long message_size;
+       int64_t session_expiry_time;
+       uint32_t session_expiry_interval;
 };

 struct msg_store_chunk
@@ -167,6 +169,8 @@ static int dump__client_chunk_process(struct mosquitto_db *db, FILE *db_fd, uint
                        return 1;
                }
                cc->id = strdup(chunk.client_id);
+               cc->session_expiry_time = chunk.F.session_expiry_time;
+               cc->session_expiry_interval = chunk.F.session_expiry_interval;
                HASH_ADD_KEYPTR(hh_id, clients_by_id, cc->id, strlen(cc->id), cc);
        }

@@ -467,8 +471,15 @@ int main(int argc, char *argv[])

        if(client_stats){
                HASH_ITER(hh_id, clients_by_id, cc, cc_tmp){
-                       printf("SC: %d SS: %d MC: %d MS: %ld   ", cc->subscriptions, cc->subscription_size, cc->messages, cc->message_size);
-                       printf("%s\n", cc->id);
+                       printf("SC: %d SS: %d MC: %d MS: %ld SET: %" PRIu64 " SEI: %u ID: %s\n",
+                                       cc->subscriptions,
+                                       cc->subscription_size,
+                                       cc->messages,
+                                       cc->message_size,
+                                       cc->session_expiry_time,
+                                       cc->session_expiry_interval,
+                                       cc->id
+                                       );
                        free(cc->id);
                }
        }

[karlp]

Is your "minimial config" complete? do you meant to have no passwords, is that the edge case you're trying to hit?

[ckrey]

yes it is complete, the trigger is the allow_anonymous false

it doesn't matter if the user/password combinations are actually valid.
Thus we don't need an actual mosquitto.acl file, although it wouldn't change the result

[karlp]

So the users/passwords provided in your mosquitto_sub line are arbitrary then?

[ckrey]

yes, just to be non-anonymous