in native/src/ssl.c [474:483]
void SSL_BIO_doref(BIO *bi)
{
BIO_JAVA *j;
if (bi == NULL)
return;
j = (BIO_JAVA *)BIO_get_data(bi);
if (j != NULL && BIO_test_flags(bi, SSL_BIO_FLAG_CALLBACK)) {
j->refcount++;
}
}