On Tue, Jan 23, 2018 at 9:25 AM, 陶冬冬 <tdd21151186@xxxxxxxxx> wrote:
> Dear Cephers,
>
> below is a piece of code in Message::decode_message:
> ```
> // m->header.version, if non-zero, should be populated with the
> // newest version of the encoding the code supports. If set, check
> // it against compat_version.
> if (m->get_header().version &&
> m->get_header().version < header.compat_version) {
> if (cct) {
> ldout(cct, 0) << "will not decode message of type " << type
> << " version " << header.version
> << " because compat_version " << header.compat_version
> << " > supported version " << m->get_header().version << dendl;
> if (cct->_conf->ms_die_on_bad_msg)
> ceph_abort();
> }
> m->put();
> return 0;
> }
> ```
> I know it’s checking the compatibility of the incoming message.
> but, i think it’s not sufficient, it only checked if the coming message’s compat_version is bigger than our version (if it’s true, the message is not supported)
> it should also check if the comming message’s version is smaller than our compat_version, right ?
No. A message older than us may still be understandable by us. Many of
the message decode functions branch to deal with older messages, and
we have a lot of code to communicate with older message types to older
daemons.
-Greg
> please correct me if i’m wrong.
>
> Regards,
> Dongdong--
> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
