---
title: "mi_fifo Module"
description: "This is a module which provides a FIFO transport layer implementation for Management Interface."
---

## Admin Guide


### Overview


This is a module which provides a FIFO transport layer
implementation for Management Interface. It receives the
command over a FIFO file and returns the output through the
reply_fifo specified.


The module checks every 30 seconds if the FIFO file exists,
and if it was deleted, it recreates it. If one wants to force
the fifo file recreation, it should send a SIGHUP signal to
the MI process PID.


### FIFO command syntax


The external commands issued via FIFO interface must follow the
following syntax:
*request = ':'(reply_fifo)?':'jsonrpc_command*


If the *reply_fifo* is missing, the MI FIFO
module will not send any reply back. A similar behavior happens
when the *jsonrpc_command* does not contain
the *id* element, and the command is considered
a JSON-RPC notification.


### Values Returned


In case of success, a valid
[JSON-RPC](http://www.jsonrpc.org/specification)
response is replied back on the fifo file, containing a successful
JSON-RPC response.


In case of failure of the MI command, a JSON-RPC reply error is
sent back over the reply fifo file.


If case of an error generated by the MI engine, mostly internal
errors, an error cause is sent back over the reply FIFO in
plain text.


### Dependencies


#### OpenSIPS Modules


The following modules must be loaded before this module:


- *No dependencies on other OpenSIPS modules*.


#### External Libraries or Applications


The following libraries or applications must be installed before
running OpenSIPS with this module loaded:


- *none*


### Exported Parameters


#### fifo_name (string)


The name of the FIFO file to be created for listening and
reading external commands.


> [!NOTE]
> Starting with Linux kernel 4.19,
> processes can no longer read from FIFO files that are saved
> in directories with sticky bits (such as */tmp*)
> and are not owned by the same user the process runs with. This
> prevents external tools (such as *opensips-cli*)
> from running MI commands using a different user (a
> *Permissions denied* error is triggered). If
> you are getting this error while trying to use
> *opensips-cli*, you can fix it by either store
> the fifo file in a non-sticky bit directory (such as
> */run/opensips*), or disable the fifo
> protection using *sysctl fs.protected_fifos = 0*
> (NOT RECOMMENDED).


*Default value is "/tmp/opensips_fifo".*


```opensips title="Set fifo_name parameter"
...
modparam("mi_fifo", "fifo_name", "/tmp/opensips_b2b_fifo")
...
```


#### fifo_mode (integer)


Permission to be used for creating the listening FIFO file. It
follows the UNIX conventions.


*Default value is 0660 (rw-rw----).*


```opensips title="Set fifo_mode parameter"
...
modparam("mi_fifo", "fifo_mode", 0600)
...
```


#### fifo_group (integer) fifo_group (string)


Group to be used for creating the listening FIFO file.


*Default value is the inherited one.*


```opensips title="Set fifo_group parameter"
...
modparam("mi_fifo", "fifo_group", 0)
modparam("mi_fifo", "fifo_group", "root")
...
```


#### fifo_user (integer) fifo_group (string)


User to be used for creating the listening FIFO file.


*Default value is the inherited one.*


```opensips title="Set fifo_user parameter"
...
modparam("mi_fifo", "fifo_user", 0)
modparam("mi_fifo", "fifo_user", "root")
...
```


#### reply_dir (string)


Directory to be used for creating the reply FIFO files.


*Default value is "/tmp/"*


```opensips title="Set reply_dir parameter"
...
modparam("mi_fifo", "reply_dir", "/home/opensips/tmp/")
...
```


#### pretty_printing (int)


Indicates whether the JSONRPC responses sent through MI should
be pretty-printed or not.


*Default value is "0 - no pretty-printing".*


```opensips title="Set pretty_printing parameter"
...
modparam("mi_fifo", "pretty_printing", 1)
...
```


#### trace_destination (string)


Trace destination as defined in the tracing module. Currently
the only tracing module is **proto_hep**.
This is where traced mi messages will go.


**WARNING:**A tracing module must be
loaded in order for this parameter to work. (for example
**proto_hep**).


*Default value is none(not defined).*


```opensips title="Set trace_destination parameter"
...
modparam("proto_hep", "trace_destination", "[hep_dest]10.0.0.2;transport=tcp;version=3")

modparam("mi_fifo", "trace_destination", "hep_dest")
...
```


#### trace_bwlist (string)


Filter traced mi commands based on a blacklist or a whitelist.
**trace_destination** must be defined for
this parameter to have any purpose. Whitelists can be defined using
'w' or 'W', blacklists using 'b' or 'B'. The type is separate by the
actual blacklist by ':'. The mi commands in the list must be separated
by ','.


Defining a blacklists means all the commands that are not blacklisted
will be traced. Defining a whitelist means all the commands that are
not whitelisted will not be traced.
**WARNING:** One can't define both
a whitelist and a blacklist. Only one of them is allowed. Defining
the parameter a second time will just overwrite the first one.


> [!WARNING]
> A tracing module must be
> loaded in order for this parameter to work. (for example
> **proto_hep**).


*Default value is none(not defined).*


```opensips title="Set trace_destination parameter"
...
## blacklist ps and which mi commands
## all the other commands shall be traced
modparam("mi_fifo", "trace_bwlist", "b: ps, which")
...
## allow only sip_trace mi command
## all the other commands will not be traced
modparam("mi_fifo", "trace_bwlist", "w: sip_trace")
...
```


### Exported Functions


No function exported to be used from configuration file.


### Example


This is an example showing the FIFO format for the
"get_statistics dialog: tm:" MI commad:
response.


```c title="FIFO request"
:reply_fifo:{"jsonrpc":"2.0","method":"get_statistics","id":"5672","params":[["dialog:","tm:"]]}
```
<!-- CONTRIBUTORS -->

### License

All documentation files (i.e. .md extension) are licensed under the Creative Common License 4.0
