API Code Examples? #487

vne147 · 2021-11-16T11:49:07Z

vne147
Nov 16, 2021

Hello!

I'm developing some C code that will use LLDP to query neighbors and specific information about them (interface, MAC, and IP). I've used the documentation in lldpctl.h to write the code below, which seems to work well. Right now it's just printing the IP and interfaces, but eventually I'll update it to probably push that info into a structure.

Next I'd like to register a callback to basically reset all the gathered information and re-query whenever any neighbor change is detected. I've read the documentation on lldpctl_watch_callback2 and lldpctl_change_callback2, but I'm still having some trouble implementing it. I'm probably not as proficient with C as I ought to be.

Is there any example code out there you can point me to that I can use as a template? If it exists, I couldn't find it.

Thanks in advance for any help you can provide.

	lldpctl_conn_t *conn;
	lldpctl_atom_t *interfaces;
	lldpctl_atom_t *iface;
	lldpctl_atom_t *neighbors;
	lldpctl_atom_t *neigh;
	lldpctl_atom_t *port;
	lldpctl_atom_t *addresses;
	lldpctl_atom_t *adr;
	
	const char *ctlname;
	const char *ifname;
	const char *mgmt_ip;
	
	//Get default transport name
	ctlname = lldpctl_get_default_transport();
	
	//Make connection to LLDP
	conn = lldpctl_new_name(ctlname,NULL,NULL,NULL);
	
	//Get list of interfaces
	interfaces = lldpctl_get_interfaces(conn);	
	
	//Iterate over each interface
	lldpctl_atom_foreach(interfaces,iface){
		
		ifname = lldpctl_atom_get_str(iface,lldpctl_k_interface_name);
		printf("Interface: %s\n",ifname);
		
		port = lldpctl_get_port(iface);
		
		neighbors = lldpctl_atom_get(port, lldpctl_k_port_neighbors);

		//Iterate over each neighbor
		lldpctl_atom_foreach(neighbors,neigh){
			
			addresses = lldpctl_atom_get(neigh,lldpctl_k_chassis_mgmt);
			
			//Iterate over each management address
			lldpctl_atom_foreach(addresses,adr){			
				mgmt_ip = lldpctl_atom_get_str(adr,lldpctl_k_mgmt_ip);
				printf("mgmt_ip: %s\n",mgmt_ip);
				
			}//end foreach addresses
			lldpctl_atom_dec_ref(adr);
		
		}//end foreach neighbors
		lldpctl_atom_dec_ref(neigh);	
		
	}//end foreach interfcaes
	lldpctl_atom_dec_ref(iface);

Answered by vincentbernat

Nov 16, 2021

lldpcli uses the same API. So, you can look at its code to see how it is implemented. lldpctl_watch_callback2() is used in lldpcli.

View full answer

vincentbernat · 2021-11-16T12:47:54Z

vincentbernat
Nov 16, 2021
Maintainer

lldpcli uses the same API. So, you can look at its code to see how it is implemented. lldpctl_watch_callback2() is used in lldpcli.

2 replies

vne147 Nov 16, 2021
Author

Hello, Vincent. Thank you for the quick reply.

Are you referring to src/client/lldpcli.c?

If so I looked through that file and didn't see any references to lldpctl_watch_callback2().

I'm kind of a noob. What am I doing wrong?

vne147 Nov 16, 2021
Author

Never mind. I found the relevant code blocks in src/client/show.c. Thanks for the help!

Ekmansoft · 2025-02-05T07:20:40Z

Ekmansoft
Feb 5, 2025

We are using this API to gather info on POE status, and to reconfigure POE. However, we have a problem that during boot, lldpd is reconfigured twice with added device name and (it seems) port filtering. When this happens, it seems like the lldpd API freezes, and may give bad responses.
It does not seem possible to get information (through any callback or similar) in the API that a reconfiguration has made lldpd API stop working.

I am thinking of the time between these prints:

lldpcli[1344]: system name set to new value blablabla1
lldpcli[1344]: iface-pattern set to new value eth*,!eth1
lldpcli[1344]: description set to new value blablabla2
lldpcli[1344]: lldpd should resume operations

We have been discussing that maybe if we control everything from the process that uses the lldpd API, we may get rid of these problems since we can control when it is done. But this will cause a bit of work which we haven't started on yet.

What is your proposal for these cases @vincentbernat?

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