86 lines
4 KiB
Text
86 lines
4 KiB
Text
Frequently Asked Questions - Clixon
|
|
===================================
|
|
|
|
Q: What is the best way of understanding Clixon?
|
|
A: Run the ietf yang routing example.
|
|
|
|
Q: How do you build and install Clixon (and the example)?
|
|
A: Clixon: ./configure; make; sudo make install; sudo make install-include
|
|
Example: cd example; make; sudo make install
|
|
|
|
Q: Is there any reference documentation?
|
|
A: Clixon uses Doxygen for reference documentation.
|
|
Build using 'make doc' and aim your browser at doc/html/index.html
|
|
|
|
Q: How do you run the example?
|
|
A: Start a backend server: 'clicon_backend -Ff /usr/local/etc/routing.conf'
|
|
Start a cli session: clicon_cli -f /usr/local/etc/routing.conf
|
|
Start a netconf session: clicon_netconf -f /usr/local/etc/routing.conf
|
|
|
|
Q: How does Clixon differ from Clicon?
|
|
A: Clixon is a fork of Clicon focussing on Yang specification and XML
|
|
database. The yang support in clicon was grown out of a key-based
|
|
scheme that was complex since it had to translate between
|
|
formats. Clixon uses only XML. A simplified commit transaction
|
|
mechanism has been added to. But Clixon is not backward compliant with
|
|
key-based Clicon applications, such as ROST.
|
|
|
|
Q: In the example, how can you alter its semantics?
|
|
- routing.conf.local - Override default settings
|
|
- The yang specifications - Alter accepted XML, database format and the configuration part of the CLI commands that are generated.
|
|
- routing_cli.cli - Change the fixed part of the CLI commands
|
|
- routing_cli.c - New cli commands may need to write a new C-funtion.
|
|
- routing_backend.c - What happens at commit.
|
|
- routing_netconf.c - Modify semantics of netconf commands.
|
|
|
|
Q: How do you check what is in a database?
|
|
clicon_dbctrl -d <database> -p
|
|
The name of the running or candidate databases are found in the
|
|
configuration file, eg /usr/local/var/routing/candidate_db
|
|
Example:
|
|
/interfaces/interface/eth0/ipv4
|
|
/interfaces/interface/eth0/type bgp
|
|
/interfaces/interface/eth0
|
|
/interfaces/interface/eth0/name eth0
|
|
Each line corresponds to a database entry (node in an XML tree). If
|
|
the node is a leaf, the value appears as the second entry.
|
|
|
|
Q: How do you write a commit rule in the example?
|
|
A: You write a commit function in routing_backend.c.
|
|
Every time a commit is made, transaction_commit() is called in the
|
|
backend. It has a 'transaction_data td' argument which is used to fetch
|
|
information on added, deleted and changed entries. You access this
|
|
information using access functions as defined in clicon_backend_transaction.h
|
|
|
|
Q: How do you check what has changed on commit?
|
|
A: You use XPATHs on the XML trees in the transaction commit callback.
|
|
Suppose you want to print all added interfaces:
|
|
cxobj *target = transaction_target(td); # wanted XML tree
|
|
# Get all added i/fs
|
|
cxobj **vec = xpath_vec_flag(target, "//interface", &len, XML_FLAG_ADD);
|
|
for (i=0; i<len; i++) # Loop over added i/fs
|
|
clicon_xml2file(stdout, vec[i]) # Print the added interface
|
|
The flags you can check for are: XML_FLAG_ADD, _DEL and _CHANGE, and their combinations.
|
|
|
|
Q How do I access the XML tree?
|
|
A: Using XPATH, find and iteration functions defined in the XML library. Example
|
|
|
|
Q: How do you write a CLI callback function?
|
|
You add an entry in routing_cli.cli
|
|
example("This is a comment") <var:int32>("This is a variable"), mycallback("myarg");
|
|
Then define a function in routing_cli.c
|
|
mycallback(clicon_handle h, cvec *cvv, cg_var *arg)
|
|
where 'cvv' contains the value of the variable and 'arg' contains the
|
|
function parameter 'myarg'.
|
|
|
|
Q: What are cg_var and cvec used in CLI callbacks?
|
|
Those are 'CLIgen variables' and vector of CLOgen
|
|
variables. Documented in CLIgen documentation. Some examples on usage is found in the
|
|
routing_cli.c
|
|
|
|
Q: How do you write a validation rule?
|
|
Similar to a commit rule, but instead write the transaction_validate() function.
|
|
Check for consitencies in the XML trees and if they fail, make an clicon_err() call.
|
|
clicon_err(OE_PLUGIN, 0, "Route %s lacks ipv4 addr", name);
|
|
return -1;
|
|
The validation or commit will then be aborted.
|