key_write
rc = key_write(keysock, &msg, sizeof (msg));
rc = key_write(keysock, msg, sizeof (*msg));
rc = key_write(keysock, buffer,
rc = key_write(keysock, buffer, SADB_64TO8(msgp->sadb_msg_len));
rc = key_write(keysock, samsg, sizeof (*samsg));