It took some effort to figure out how to make SNMP work with LWIP and private
MIB. I left a little code in bug 1001789, but here is working code that does
not have memory leaks and seems to work consistently. I don't know for sure if
the callback is required, but it does ensure the trap runs on the tcpip thread,
and from what I have read, this needs to be the case.
This works on kinetis K60 with the lwip sequential interface enbled.
#ifndef SNMP_H_
#define SNMP_H_
#include "lwip/snmp_structs.h"
#include "lwip/tcpip.h"
#include <stdint.h>
#include "pmbus.h"
#define SNMP_SEND_TRAP 1
typedef struct snmp_message
{
uint32_t COMMAND;
struct ip_addr ADDRESS;
unsigned char TRAP;
char *message;
} SNMP_MESSAGE, *SNMP_MESSAGE_PTR;
extern void snmp_thread_entry(void *arg);
extern void send_trap(struct ip_addr addr, unsigned char trap, char *message);
#endif /* SNMP_H_ */
#include "private_mib.h"
#include "lwip/snmp.h"
#include "lwip/snmp_msg.h"
#include "lwip/snmp_asn1.h"
#include "lwip/snmp_structs.h"
#include "lwip/mem.h"
#include "snmp.h"
extern struct snmp_msg_trap trap_msg;
// Private MIB code from python script here
void
lwip_privmib_init(void)
{
}
void send_trap_callback( void * parameters )
{
struct snmp_obj_id eoid;
// There should be a way to do this directly.
eoid.id[0] = enterprises_ids[1];
eoid.len = 1;
snmp_send_trap(SNMP_GENTRAP_ENTERPRISESPC, &eoid, 1);
snmp_varbind_list_free(&trap_msg.outvb);
}
void snmp_thread_entry(void *arg)
{
SNMP_MESSAGE_PTR snmp_message;
struct snmp_obj_id objid;
// There should be a better way to initialize this.
objid.len = 1;
objid.id[0] = private_ids[0];
snmp_init();
cyg_mbox_create(&snmp_mailbox_handle, &snmp_mailbox);
while (1)
{
snmp_message = (SNMP_MESSAGE_PTR)
cyg_mbox_get(snmp_mailbox_handle);
if (snmp_message->COMMAND == SNMP_SEND_TRAP)
{
struct ip_addr addr;
// Reverse the bytes because snmp_trap_dst_ip_set
reverses them again.
addr.addr = htonl(snmp_message->ADDRESS.addr);
snmp_trap_dst_ip_set(0,&addr);
snmp_trap_dst_enable(0,snmp_message->TRAP);
struct snmp_varbind *vb = snmp_varbind_alloc(&objid,
SNMP_ASN1_OPAQUE, strlen(snmp_message->message)+1);
if (vb == NULL)
{
diag_printf("SNMP failure to allocate
memory\n");
continue;
}
strcpy (vb->value, snmp_message->message);
snmp_varbind_tail_add(&trap_msg.outvb,vb);
tcpip_callback(send_trap_callback, NULL);
}
free(snmp_message->message);
free(snmp_message);
}
}
void send_trap(struct ip_addr addr, unsigned char trap, char *message)
{
SNMP_MESSAGE_PTR snmp_message = (SNMP_MESSAGE_PTR)
malloc(sizeof(SNMP_MESSAGE));
snmp_message->COMMAND = SNMP_SEND_TRAP;
snmp_message->TRAP = trap;
snmp_message->ADDRESS = addr;
snmp_message->message = (char*) malloc(strlen(message)+1);
strcpy(snmp_message->message, message);
cyg_mbox_put(snmp_mailbox_handle, (void *) snmp_message);
}
Code to start the snmp thread:
void start_network(cyg_addrword_t p)
{
struct ip_addr ipaddr, netmask, gw;
struct netif *netif;
/* Set network address variables */
IP_GATEWAY(&gw);
IP_ADDRESS(&ipaddr);
IP_MASK(&netmask);
//tcpip_init(NULL, NULL);
// Check return for null
//netif_result = netif_add(&netif, &ipaddr, &netmask, &gw, NULL,
init_ip, tcpip_input);
//netif_set_up(&netif);
cyg_lwip_sequential_init();
netif = netif_find("et0");
netif_set_ipaddr(netif, &ipaddr);
netif_set_netmask(netif, &netmask);
netif_set_gw(netif, &gw);
netif_set_up(netif);
cyg_lwip_thread_new("snmp", snmp_thread_entry, NULL,
snmp_stack, STACK_SIZE, 7);
cyg_thread_exit();
}
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