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docs:techref:rpcd [2021/01/03 05:26] – [plugin executables] stangridocs:techref:rpcd [2023/10/14 06:08] (current) – update vgaetera
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 ====== rpcd: OpenWrt ubus RPC daemon for backend server ====== ====== rpcd: OpenWrt ubus RPC daemon for backend server ======
- 
 In OpenWrt we commonly use [[docs:techref:ubus|ubus]] for all kinds of communication. It can provide info from various software as well as request various actions. Nevertheless, not every part of OpenWrt has a daemon that can register itself using ''ubus''. For an example ''uci'' and ''opkg'' are command-line tools without any background process running all the time. In OpenWrt we commonly use [[docs:techref:ubus|ubus]] for all kinds of communication. It can provide info from various software as well as request various actions. Nevertheless, not every part of OpenWrt has a daemon that can register itself using ''ubus''. For an example ''uci'' and ''opkg'' are command-line tools without any background process running all the time.
  
 It would be not efficient to write a daemon for every software like this and run them independently. This is why ''rpcd'' was developed. It’s a tiny daemon with support for plugins using trivial API. It loads library ''%%.so%%'' files and calls init function of each of them. It would be not efficient to write a daemon for every software like this and run them independently. This is why ''rpcd'' was developed. It’s a tiny daemon with support for plugins using trivial API. It loads library ''%%.so%%'' files and calls init function of each of them.
- 
  
 The code is published under [[wp>ISC_license|ISC license]] and can be found via git at  [[https://git.openwrt.org/project/rpcd.git]]. The code is published under [[wp>ISC_license|ISC license]] and can be found via git at  [[https://git.openwrt.org/project/rpcd.git]].
  
 ==== Default plugins ==== ==== Default plugins ====
 +There are few small plugins distributed with the ''rpcd'' sources. Two of them (''session'' and ''uci'') are built-in, others are optional and have to be build as separated ''%%.so%%'' libraries. Apart from that there are other projects providing their own plugins.
  
-There are few small plugins distributed with the ''rpcd'' sources. Two of them (''session'' and ''uci'') are built-in, others are optional and have to be build as separated ''%%.so%%'' libraries. Apart from that there are other projects providing their own plugins. 
 ===== plugin executables ===== ===== plugin executables =====
- 
 It is possible to expose shell script functionality over ubus by using ''rpcd'' plugin executables functionality. Executables stored in ''/usr/libexec/rpcd/'' directory will be run by ''rpcd''. Lets look at the following example: It is possible to expose shell script functionality over ubus by using ''rpcd'' plugin executables functionality. Executables stored in ''/usr/libexec/rpcd/'' directory will be run by ''rpcd''. Lets look at the following example:
  
-<code> +<code bash> 
-$ mkdir -p /usr/libexec/rpcd/ +mkdir -p /usr/libexec/rpcd 
-$ cat << EOF > /usr/libexec/rpcd/foo+cat << "EOF" > /usr/libexec/rpcd/foo
 #!/bin/sh #!/bin/sh
  
Line 48: Line 45:
 esac esac
 EOF EOF
-$ chmod +x /usr/libexec/rpcd/foo +chmod +x /usr/libexec/rpcd/foo 
-$ /etc/init.d/rpcd restart+service rpcd restart
 </code> </code>
  
 This will create new ubus functions which then can be used (after restarting rpcd): This will create new ubus functions which then can be used (after restarting rpcd):
  
-<code>+<code bash>
 $ ubus -v list foo $ ubus -v list foo
 'foo' @a9482c5b 'foo' @a9482c5b
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  "toto":{}  "toto":{}
  "failme":{}  "failme":{}
 +
 $ ubus -S call foo bar '{"arg1": true }' $ ubus -S call foo bar '{"arg1": true }'
 {{"hello":"world"}} {{"hello":"world"}}
 +
 $ ubus -S call foo toto $ ubus -S call foo toto
 {"something":"somevalue"} {"something":"somevalue"}
 +
 $ ubus -S call foo failme $ ubus -S call foo failme
 +
 $ echo $? $ echo $?
 2 2
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 **The actual data is then sent by the ''ubus'' client via ''stdin''.** I.e. if you're testing the script itself, you need to use  **The actual data is then sent by the ''ubus'' client via ''stdin''.** I.e. if you're testing the script itself, you need to use 
-<code>+ 
 +<code bash>
 echo '{"arg1": 42}' | yourscript call yourmethod echo '{"arg1": 42}' | yourscript call yourmethod
 </code> </code>
 +
 You //cannot// simply use ''yourscript call yourmethod '{"arg1": 42}''' as you might have expected. You //cannot// simply use ''yourscript call yourmethod '{"arg1": 42}''' as you might have expected.
  
 The method signature is a simple object containing ''key:value'' pairs. The argument type is inferred from the value. If the value is a string (regardless of the contents) it is registered as string, if the value is a bool true or false, its registered as bool, if the value is an integer, it is registered as either int8, int16, int32 or int64 depending on the value i.e. ''"foo": 16'' will be ''INT16'', ''"foo": 64'' will be ''INT64'', ''"foo": 8'' will be ''INT8'' and everything else will be ''INT32''. The method signature is a simple object containing ''key:value'' pairs. The argument type is inferred from the value. If the value is a string (regardless of the contents) it is registered as string, if the value is a bool true or false, its registered as bool, if the value is an integer, it is registered as either int8, int16, int32 or int64 depending on the value i.e. ''"foo": 16'' will be ''INT16'', ''"foo": 64'' will be ''INT64'', ''"foo": 8'' will be ''INT8'' and everything else will be ''INT32''.
  
-It is enough to issue ''/etc/init.d/rpcd reload'' to make it pick up new plugin executables, that way one does not lose active sessions.+It is enough to issue ''service rpcd reload'' to make it pick up new plugin executables, that way one does not lose active sessions.
  
 **NOTE:** At least on CC builds, reload is //not// enough, and you must ''restart'' to pickup new plugins and changes to existing plugins. **NOTE:** At least on CC builds, reload is //not// enough, and you must ''restart'' to pickup new plugins and changes to existing plugins.
  
  • Last modified: 2021/01/03 05:26
  • by stangri