How to use API/function to get informations

[HelloLady]

Hi,vincent:

I want to use API/function to get some informations what I want .There's a parameter confuse me that is lldpctl_atom_t .I can get it with a function or I need to set it by myselt .Here is a simple test program to get ip address.What should I do to deal with lldpctl_atom_t???

#include "lldpctl.h"
#include <stdio.h>
#include <string.h>

int main(void){
	lldpctl_atom_t{
		//... ...
	};

	lldpctl_conn_t *conn;
	lldpctl_atom_t *atom;

	
	char *port_id;
	char *IP_address; 
	char *hostname;
	lldpctl_key_t  lldpctl_key_id;
	lldpctl_key_t  lldpctl_mgmt_id;

 	// 1.get connection socket
	conn = lldpctl_atom_get_connection(atom);
	//2.read IP_address
	IP_address = lldpctl_atom_get(atom,lldpctl_config_hostname);
	//3.read port_id
	port_id = lldpctl_atom_get_str(atom, lldpctl_mgmt_id);
	//4.print messages
	printf("ID_address: %s\r\n",IP_address);
	printf("port_id: %s\r\n",port_id);

	return 0;
}

[vincentbernat]

Look at src/lib/lldpctl.h or the source code of lldpctl for documentation. Don't use lldpctl_atom_get_connection().

[HelloLady]

For my understanding, I think that lldpd has been installed already and I can use lldpcli to get neighbors' information, so I can get the lldpctl_conn_t structure and lldpctl_atuom_t structure via API function.
But I didn't find them in src/lib/lldpctl.h .

[vincentbernat]

The structures are opaque. The documentation on how to use them is src/lib/lldpctl.h. The canonical example is lldpcli itself (in src/client).

[HelloLady]

I wrote a test program to get neighbor's ip reffering to lldpcli,but actually I get the local ip. Below is part of the code,after excuting it shows：

lldpd# ./lldpd2 
get interface sucessful!
mgmt_ip: 192.168.2.75
mgmt_ip: fe80::f9b:3521:9c5b:98b5
end to get mgmt_ip...

Could you hlep me to fix it?

	/*get default transport name*/
	ctlname = lldpctl_get_default_transport();
	/*make a connection*/
	conn = lldpctl_new_name(ctlname,NULL,NULL,NULL);
	if(conn == NULL){
		printf("make a new connection failed\n");
		return NULL;
	}

	iface = iter_on _interfaces(interfaces)

	while(iface){
		
		printf("get interface sucessful!\n");
		
		port = lldpctl_get_port(iface);

		if(port == NULL){
			printf("get port failed\n");
			return NULL;
		}

		neighbors = lldpctl_atom_get(port,lldpctl_k_port_neighbors);

		if(neighbors == NULL){
			printf("get neighbors failed\n");
			return NULL;
		}

		to_lldpctl_atom_foreach(neighbors,neighbor){

			local = lldpctl_atom_get_int(port,lldpctl_k_port_index) > 0 ? 1 : 0;

			chassis = lldpctl_atom_get(port,lldpctl_k_port_chassis);
			if(chassis == NULL){
				printf("get port chassis failed\n");
				return NULL;
			}

			interface_name = lldpctl_atom_get_str(iface,lldpctl_k_interface_name);
			if(interface_name == NULL){
				printf("get interface_name failed\n");
				return NULL;
			}

			if(local == 0){
				chassis_index = lldpctl_atom_get_str(chassis,lldpctl_k_chassis_index);
				if(chassis_index == NULL){
					printf("get chassis index failed\n");
					return NULL;
				}
			}

			port_age = display_age(lldpctl_atom_get_int(port,lldpctl_k_port_age));
			if(port_age == NULL){
				printf("display_age is failed\n");
				return	NULL;
			}

			//display_chassis(w,chassis,DISPLAY_DETAILS);						
			chassis_id_subtype = lldpctl_atom_get(chassis,lldpctl_k_chassis_id_subtype);
			if(chassis_id_subtype == NULL){
				printf("get chassis_id_subtype failed\n");
				return NULL;
			}
			chassis_id = lldpctl_atom_get(chassis,lldpctl_k_chassis_id);
			if(chassis_id == NULL){
				printf("get chassis_id failed\n");
				return NULL;
			}
			chassis_name = lldpctl_atom_get(chassis,lldpctl_k_chassis_name);
			if(chassis_name == NULL){
				printf("get chassis failed\n");
				return NULL;
			}
			chassis_descr = lldpctl_atom_get(chassis,lldpctl_k_chassis_descr);
			if(chassis_descr == NULL){
				printf("get chassis_descr failed\n");
				return NULL;
			}
			
			/*management address*/
			mgmts = lldpctl_atom_get(chassis,lldpctl_k_chassis_mgmt);
			if(!mgmts){
				printf("get chassis mgmt failed\n");
				return NULL;
			}
			lldpctl_atom_foreach(mgmts,mgmt){
				mgmt_ip = lldpctl_atom_get_str(mgmt,lldpctl_k_mgmt_ip);
				if(!mgmt_ip){
					printf("get mgmt ip failed\n");
					return NULL;
				}
				printf("mgmt_ip: %s\n",mgmt_ip);
			}
			lldpctl_atom_dec_ref(mgmt);
                }

		lldpctl_atom_dec_ref(port);
		lldpctl_atom_dec_ref(neighbors);
		lldpctl_atom_dec_ref(iface);

		if(lldpctl_atom_get_str(iface,lldpctl_k_interface_name) == NULL){		 
			break;
		}

[vincentbernat]

You are iterating on neighbors, but never use neighbor. Use neighbor instead of port in the loop.

[vincentbernat]

Use a for loop instead of an iterator (otherwise, you should keep the static declarations):

iface_list = lldpctl_get_interfaces(conn);
lldpctl_atom_foreach(iface, iface_list) {
 /* ... */
}
lldpctl_atom_dec_ref(iface_list);

[vincentbernat]

You cannot build an iterator if you remove the static keyword from local variables. Don't use this pattern if you can avoid it, just use lldpctl_atom_foreach() and use iface directly in the body of the for loop. Also, "connection refused" is likely because the lldpd daemon is not running.

[HelloLady]

Thanks for your reply.I modified the code usinglldpctl_atm_foreach(iface_list,iface)(which you advise to use lldpctl_atm_foreach(iface,iface_list)) in the body, the executing result shows segmentation fault.lldpctl_atom_foreach(neighbors,neighbor) is the problem.GDB debug like below:

Breakpoint 1, main () at api_fixed.c:182
182			lldpctl_atom_foreach(neighbors,neighbor){
(gdb) n
185				chassis_neighbor = lldpctl_atom_get(neighbor,lldpctl_k_port_chassis);
(gdb) n
187				if(!chassis_neighbor){
(gdb) n
193				neighbor_chassis_id_subtype = lldpctl_atom_get_str(chassis_neighbor,lldpctl_k_chassis_id_subtype);
(gdb) n
194				neighbor_chassis_id = lldpctl_atom_get_str(chassis_neighbor,lldpctl_k_chassis_id);
(gdb) n
195				if(!neighbor_chassis_id){
(gdb) n
199				printf("mac_address: %s\r\n",neighbor_chassis_id);
(gdb) n
201				neighbor_chassis_name = lldpctl_atom_get_str(chassis_neighbor,lldpctl_k_chassis_name);
(gdb) n
202				if(!neighbor_chassis_name){
(gdb) n
206				printf("system_name: %s\r\n",neighbor_chassis_name);
(gdb) n
208				neighbor_chassis_descr = lldpctl_atom_get_str(chassis_neighbor,lldpctl_k_chassis_descr);
(gdb) n
209				if(!neighbor_chassis_descr){
(gdb) n
213				printf("system_name: %s\r\n",neighbor_chassis_descr);
(gdb) n
216				neighbor_mgmts = lldpctl_atom_get(chassis_neighbor,lldpctl_k_chassis_mgmt);
(gdb) n
217				if(!neighbor_mgmts){
(gdb) n
222				neighbor_configure = lldpctl_get_configuration(conn);
(gdb) n
224				lldpctl_atom_dec_ref(neighbor_configure);
(gdb) n
228				lldpctl_atom_foreach(neighbor_mgmts,neighbor_mgmt){
(gdb) n
229					neighbor_mgmt_ip = lldpctl_atom_get_str(neighbor_mgmt,lldpctl_k_mgmt_ip);
(gdb) n
230					if(!neighbor_mgmt_ip){
(gdb) n
234					printf("neighbor_mgmt_ip: %s\r\n",neighbor_mgmt_ip);
(gdb) n
236					lldpctl_atom_dec_ref(neighbor_mgmts);
(gdb) n
228				lldpctl_atom_foreach(neighbor_mgmts,neighbor_mgmt){
(gdb) n
229					neighbor_mgmt_ip = lldpctl_atom_get_str(neighbor_mgmt,lldpctl_k_mgmt_ip);
(gdb) n
230					if(!neighbor_mgmt_ip){
(gdb) n
234					printf("neighbor_mgmt_ip: %s\r\n",neighbor_mgmt_ip);
(gdb) n
236					lldpctl_atom_dec_ref(neighbor_mgmts);
(gdb) n
228				lldpctl_atom_foreach(neighbor_mgmts,neighbor_mgmt){
(gdb) n
240				lldpctl_atom_dec_ref(neighbors);
(gdb) n
242				lldpctl_atom_dec_ref(port);
(gdb) n
182			lldpctl_atom_foreach(neighbors,neighbor){
(gdb) n

Program received signal SIGSEGV, Segmentation fault.
_lldpctl_atom_next_ports_list (atom=0x23b18, iter=0x0) at ../../../src/lib/atoms/port.c:164
warning: Source file is more recent than executable.
164	}
(gdb) n

[vincentbernat]

You decrement the reference count for neighbors and still use it later.

[HelloLady]

I fixed like below:

lldpctl_atom_foreach(neighbors,neighbor){
// ... ...
}
lldpctl_atom_dec_ref(neighbors);
lldpctl_atom_dec_ref(port);

the result still is Segmentation fault.

Breakpoint 1, main () at api_fixed.c:182
182			lldpctl_atom_foreach(neighbors,neighbor){
... ...
216				neighbor_mgmts = lldpctl_atom_get(chassis_neighbor,lldpctl_k_chassis_mgmt);
(gdb) n
217				if(!neighbor_mgmts){
(gdb) n
222				neighbor_configure = lldpctl_get_configuration(conn);
(gdb) n
224				lldpctl_atom_dec_ref(neighbor_configure);
(gdb) n
228				lldpctl_atom_foreach(neighbor_mgmts,neighbor_mgmt){
(gdb) n
229					neighbor_mgmt_ip = lldpctl_atom_get_str(neighbor_mgmt,lldpctl_k_mgmt_ip);
(gdb) n
230					if(!neighbor_mgmt_ip){
(gdb) n
234					printf("neighbor_mgmt_ip: %s\r\n",neighbor_mgmt_ip);				
(gdb) n
228				lldpctl_atom_foreach(neighbor_mgmts,neighbor_mgmt){
(gdb) n
229					neighbor_mgmt_ip = lldpctl_atom_get_str(neighbor_mgmt,lldpctl_k_mgmt_ip);
(gdb) n
230					if(!neighbor_mgmt_ip){
(gdb) n
234					printf("neighbor_mgmt_ip: %s\r\n",neighbor_mgmt_ip);				
(gdb) n
228				lldpctl_atom_foreach(neighbor_mgmts,neighbor_mgmt){
(gdb) n
239				lldpctl_atom_dec_ref(neighbor_mgmts);
(gdb) n
182			lldpctl_atom_foreach(neighbors,neighbor){
(gdb) n

Program received signal SIGSEGV, Segmentation fault.
_lldpctl_atom_next_ports_list (atom=0x23b18, iter=0x0) at ../../../src/lib/atoms/port.c:164
warning: Source file is more recent than executable.
164	}
(gdb) 

[vincentbernat]

No clue here. Are you sure you did recompile (see last warning)?

[HelloLady]

I am sure .And I execute below code:

	/*get default transport name*/
	ctlname = lldpctl_get_default_transport();
	/*make a connection*/
	conn = lldpctl_new_name(ctlname,NULL,NULL,NULL);
	if(conn == NULL){
		printf("make a new connection failed\n");
		return NULL;
	}

	iface_list = lldpctl_get_interfaces(conn);
	if(iface_list == NULL){
			printf("get iface_list failed\n");
			return NULL;
	}

	lldpctl_atom_foreach(iface_list, iface){

		port = lldpctl_get_port(iface);
		if(port == NULL){
			printf("get port failed\n");
			return NULL;
		}

		/* need to add part1 */
		printf("need to add part1\r\n");

		neighbors = lldpctl_atom_get(port,lldpctl_k_port_neighbors);

		if(neighbors == NULL){
			printf("get neighbors failed\r\n");
			return NULL;

		}

		lldpctl_atom_foreach(neighbors,neighbor){
	
			/*add neighbor information*/
			chassis_neighbor = lldpctl_atom_get(neighbor,lldpctl_k_port_chassis);

			if(!chassis_neighbor){
				printf("get neighbor chassis failed\r\n");
				return NULL;
			}

			/* need to add part2 */
			printf("need to add part2\r\n");
		}

		lldpctl_atom_dec_ref(neighbors);

		lldpctl_atom_dec_ref(port);

		 
		printf("out: lldpctl_atom_foreach(neighbors,neighbor)\r\n");
		
	}

	lldpctl_atom_dec_ref(iface_list);

The terminal shows ::

need to add part1
need to add part2
out: lldpctl_atom_foreach(neighbors,neighbor)
Segmentation fault

[vincentbernat]

It looks like it segault on the outer for loop, not the inner. This doesn't match your gdb session. I don't see anything wrong with your code.

[HelloLady]

I cropped the code and just reserve the main framework to make sure the main framework is correct.But it still occured segmentation fault.

[HelloLady]

I found that if one lldpctl_atom_foreach() include another lldpctl_atom_foreach(),when out the first loop it occurs segmentation fault.

[vincentbernat]

That's odd.

Could you try to add:

#define lldpctl_atom_foreach2(atom, value)				\
	for (lldpctl_atom_iter_t *iter2 = lldpctl_atom_iter(atom);	\
	     iter2 && (value = lldpctl_atom_iter_value(atom, iter2));	\
	     iter2 = lldpctl_atom_iter_next(atom, iter2),			\
		 lldpctl_atom_dec_ref(value))

And use lldpctl_atom_foreach2 for the inner loop.

[HelloLady]

It works by modified lldpctl_atom_foreach2.

[vincentbernat]

That's quite odd. Which compiler are you using? Which version?

[HelloLady]

GCC: (crosstool-NG crosstool-ng-1.23.0-280-g01e3290) 7.3.0.

[vincentbernat]

I have committed your fix some time ago. Let's close this issue.