此结构体中定义了各个回调函数，在函数init_ksm（E:\code\net-snmp-5.4.2.1\snmplib）中进行了初始化。

void init_ksm(void)

{

struct snmp_secmod_def *def;

// 申请内存

def = SNMP_MALLOC_STRUCT(snmp_secmod_def);

// 初始化回调函数

def->encode_reverse = ksm_rgenerate_out_msg;

def->decode = ksm_process_in_msg;

def->session_open = ksm_session_init;

def->pdu_free_state_ref = ksm_free_state_ref;

def->pdu_free = ksm_free_pdu;

def->pdu_clone = ksm_clone_pdu;

// 注册

register_sec_mod(NETSNMP_KSM_SECURITY_MODEL, "ksm", def);

}