How to implement modules in ejabberd? - ejabberd-module

Question

I am new on the XMPP server ejabberd. I installed ejabberd on ubuntu from this link: https://docs.ejabberd.im/admin/installation/#install-on-linux. I am using the default ejabberd.yml file which is present in ejabberd-20.07/conf folder. Here is my ejabberd.yml file:
hosts:
- "faiqkhan-VirtualBox"
loglevel: 4
log_rotate_size: 10485760
log_rotate_count: 1
certfiles:
- "/home/faiqkhan/ejabberd-20.07/conf/server.pem"
## - "/etc/letsencrypt/live/localhost/fullchain.pem"
## - "/etc/letsencrypt/live/localhost/privkey.pem"
ca_file: "/home/faiqkhan/ejabberd-20.07/conf/cacert.pem"
listen:
-
port: 5222
ip: "::"
module: ejabberd_c2s
max_stanza_size: 262144
shaper: c2s_shaper
access: c2s
starttls_required: false
-
port: 5269
ip: "::"
module: ejabberd_s2s_in
max_stanza_size: 524288
-
port: 5443
ip: "::"
module: ejabberd_http
tls: true
request_handlers:
"/admin": ejabberd_web_admin
"/api": mod_http_api
"/bosh": mod_bosh
"/captcha": ejabberd_captcha
"/upload": mod_http_upload
"/ws": ejabberd_http_ws
"/oauth": ejabberd_oauth
-
port: 5280
ip: "::"
module: ejabberd_http
request_handlers:
"/admin": ejabberd_web_admin
-
port: 1883
ip: "::"
module: mod_mqtt
backlog: 1000
s2s_use_starttls: optional
acl:
local:
user_regexp: ""
loopback:
ip:
- 127.0.0.0/8
- ::1/128
- ::FFFF:127.0.0.1/128
admin:
user:
- "admin#faiqkhan-VirtualBox"
access_rules:
local:
allow: local
c2s:
deny: blocked
allow: all
announce:
allow: admin
configure:
allow: admin
muc_create:
allow: local
pubsub_createnode:
allow: local
trusted_network:
allow: local
api_permissions:
"console commands":
from:
- ejabberd_ctl
who: all
what: "*"
"admin access":
who:
access:
allow:
acl: loopback
acl: admin
oauth:
scope: "ejabberd:admin"
access:
allow:
acl: loopback
acl: admin
what:
- "*"
- "!stop"
- "!start"
"public commands":
who:
ip: 127.0.0.1/8
what:
- status
- connected_users_number
shaper:
normal: 1000
fast: 50000
shaper_rules:
max_user_sessions: 10
max_user_offline_messages:
5000: admin
100: all
c2s_shaper:
none: admin
normal: all
s2s_shaper: fast
max_fsm_queue: 10000
acme:
contact: "mailto:admin#faiqkhan-VirtualBox"
ca_url: "https://acme-v02.api.letsencrypt.org/directory"
modules:
mod_adhoc: {}
mod_admin_extra: {}
mod_announce:
access: announce
mod_avatar: {}
mod_blocking: {}
mod_bosh: {}
mod_caps: {}
mod_carboncopy: {}
mod_client_state: {}
mod_configure: {}
mod_disco: {}
mod_fail2ban: {}
mod_http_api: {}
mod_http_upload:
put_url: https://#HOST#:5443/upload
mod_last: {}
mod_mam:
## Mnesia is limited to 2GB, better to use an SQL backend
## For small servers SQLite is a good fit and is very easy
## to configure. Uncomment this when you have SQL configured:
## db_type: sql
assume_mam_usage: true
default: never
mod_mqtt: {}
mod_muc:
access:
- allow
access_admin:
- allow: admin
access_create: muc_create
access_persistent: muc_create
access_mam:
- allow
default_room_options:
allow_subscription: true # enable MucSub
mam: false
mod_muc_admin: {}
mod_offline:
access_max_user_messages: max_user_offline_messages
mod_ping: {}
mod_privacy: {}
mod_private: {}
mod_proxy65:
access: local
max_connections: 5
mod_pubsub:
access_createnode: pubsub_createnode
plugins:
- flat
- pep
force_node_config:
## Avoid buggy clients to make their bookmarks public
storage:bookmarks:
access_model: whitelist
mod_push: {}
mod_push_keepalive: {}
mod_register:
## Only accept registration requests from the "trusted"
## network (see access_rules section above).
## Think twice before enabling registration from any
## address. See the Jabber SPAM Manifesto for details:
## https://github.com/ge0rg/jabber-spam-fighting-manifesto
ip_access: all
mod_roster:
versioning: true
mod_s2s_dialback: {}
mod_shared_roster: {}
mod_stream_mgmt:
resend_on_timeout: if_offline
mod_vcard: {}
mod_vcard_xupdate: {}
mod_version:
show_os: false
mod_stanza_ack: {}
I try the given code in the link question Ejabberd return message to sender hook / message receipts and added my module in ejabberd.yml file which is in the last line of the above code. I create mod_stanza_ack.erl file and compile the file using command
./erlc mod_stanza_ack.erl
and get mod_stanza_ack.beam file. I coped mod_stanza_ack.beam file to ejabberd-20.07/lib/ejabberd-20.07/ebin folder where all the module files are present. Then I start ejabberd server using
./ejabberdctl live
command to view logs. Module works for me but on the server-side, it always crashes with an error
**Hook user_send_packet crashed when running mod_stanza_ack:on_user_send_packet/1:
** exception error: undefined function mod_stanza_ack:on_user_send_packet/1
in function ejabberd_hooks:safe_apply/4 (src/ejabberd_hooks.erl, line 236)
in call from ejabberd_hooks:run_fold1/4 (src/ejabberd_hooks.erl, line 217)
in call from ejabberd_c2s:handle_authenticated_packet/2 (src/ejabberd_c2s.erl, line 484)
in call from xmpp_stream_in:process_authenticated_packet/2 (src/xmpp_stream_in.erl, line 714)
in call from xmpp_stream_in:handle_info/2 (src/xmpp_stream_in.erl, line 404)
in call from p1_server:handle_msg/8 (src/p1_server.erl, line 696)
in call from proc_lib:init_p_do_apply/3 (proc_lib.erl, line 249)**.
Did I miss something? Or using deprecated functions?

Answer 1

Well, that example source code is six years old, and ejabberd development API has changed since then. I've updated the example, and this compiles and starts correctly with ejabberd 20.07:
-module(mod_stanza_ack).
-behaviour(gen_mod).
-include("xmpp.hrl").
-include("logger.hrl").
-include("translate.hrl").
-export([start/2, stop/1, mod_options/1, mod_doc/0, depends/2]).
-export([on_user_send_packet/1]).
start(Host, _Opts) ->
?INFO_MSG("mod_stanza_ack starting", []),
ejabberd_hooks:add(user_send_packet, Host, ?MODULE, on_user_send_packet, 0),
ok.
stop(Host) ->
?INFO_MSG("mod_stanza_ack stopping", []),
ejabberd_hooks:delete(user_send_packet, Host, ?MODULE, on_user_send_packet, 0),
ok.
on_user_send_packet({#presence{to = To, from = From} = Packet, C2SState}) ->
?INFO_MSG("mod_stanza_ack a presence has been sent coming from: ~p", [From]),
?INFO_MSG("mod_stanza_ack a presence has been sent to: ~p", [To]),
?INFO_MSG("mod_stanza_ack a presence has been sent with the following packet:~n ~p", [Packet]),
{Packet, C2SState};
on_user_send_packet({#iq{to = To, from = From} = Packet, C2SState}) ->
?INFO_MSG("mod_stanza_ack a iq has been sent coming from: ~p", [From]),
?INFO_MSG("mod_stanza_ack a iq has been sent to: ~p", [To]),
?INFO_MSG("mod_stanza_ack a iq has been sent with the following packet:~n ~p", [Packet]),
{Packet, C2SState};
on_user_send_packet({#message{to = To, from = From} = Packet, C2SState}) ->
?INFO_MSG("mod_stanza_ack a message has been sent coming from: ~p", [From]),
?INFO_MSG("mod_stanza_ack a message has been sent to: ~p", [To]),
?INFO_MSG("mod_stanza_ack a message has been sent with the following packet:~n ~p", [Packet]),
{Packet, C2SState}.
depends(_Host, _Opts) ->
[].
mod_options(_Host) ->
[].
mod_doc() ->
#{desc =>
?T("This an example module.")}.
Following your detailed step by step installation guide, I get two problems, that I describe here and how to solve them:
Compilation lacks header files.
I copy mod_stanza_ack.erl to ejabberd-20.07/bin, and then run this command:
$ ./erlc mod_stanza_ack.erl
mod_stanza_ack.erl:4: can't find include file "xmpp.hrl"
mod_stanza_ack.erl:5: can't find include file "logger.hrl"
mod_stanza_ack.erl:6: can't find include file "translate.hrl"
mod_stanza_ack.erl:12: undefined macro 'INFO_MSG/2'
mod_stanza_ack.erl:17: undefined macro 'INFO_MSG/2'
mod_stanza_ack.erl:22: undefined macro 'INFO_MSG/2'
mod_stanza_ack.erl:47: undefined macro 'T/1'
mod_stanza_ack.erl:8: function mod_doc/0 undefined
mod_stanza_ack.erl:8: function start/2 undefined
mod_stanza_ack.erl:8: function stop/1 undefined
mod_stanza_ack.erl:9: function on_user_send_packet/1 undefined
The solution is simple: provide the paths to the header files:
$ ./erlc -I ../lib/ejabberd-20.07/include/ -I ../lib/xmpp-1.4.9/include/ -I ../lib/fast_xml-1.1.43/include/ mod_stanza_ack.erl
This way the file is compiled correctly.
INFO_MSG in the source code do not produce log messages in ejabberd log file or "ejabberdctl live" console.
This is because we didn't tell the compiler to use the LAGER library. The solution is quite simple: include -DLAGER in the module compilation. So, this is the perfect compilation call:
$ ./erlc -I ../lib/ejabberd-20.07/include/ -I ../lib/xmpp-1.4.9/include/ -I ../lib/fast_xml-1.1.43/include/ -DLAGER mod_stanza_ack.erl
Now, you copy the resulting mod_stanza_ack.beam with all the other ejabberd beam files, enable the module in ejabberd.yml, and restart ejabberd, and all will work as expected