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ofp-errors: Explain the whole "expected duplications" thing.

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That way I won't have to figure it out again the next time.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Thomas Graf <tgraf@noironetworks.com>
This commit is contained in:
Ben Pfaff
2015-01-22 09:07:36 -08:00
parent a78f446a94
commit 4ba1522163
1 changed files with 30 additions and 2 deletions
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32
lib/ofp-errors.h
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@@ -45,7 +45,8 @@ struct ofpbuf;
#define OFPERR_OFS (1 << 30)
/* OpenFlow error codes.
/* OpenFlow error codes
* --------------------
*
* The comments below are parsed by the extract-ofp-errors program at build
* time and used to determine the mapping between "enum ofperr" constants and
@@ -71,7 +72,34 @@ struct ofpbuf;
* - Additional text is a human-readable description of the meaning of each
* error, used to explain the error to the user. Any text enclosed in
* square brackets is omitted; this can be used to explain rationale for
* choice of error codes in the case where this is desirable. */
* choice of error codes in the case where this is desirable.
*
*
* Expected duplications
* ---------------------
*
* Occasionally, in one version of OpenFlow a single named error can indicate
* two or more distinct errors, then a later version of OpenFlow splits those
* meanings into different error codes. When that happens, both errors are
* assigned the same value in the earlier version. That is ordinarily a
* mistake, so the build system reports an error. When that happens, add the
* error message to the list of "Expected duplications" below to suppress the
* error. In such a case, the named error defined earlier is how OVS
* interprets the earlier, merged form of the error.
*
* For example, OpenFlow 1.1 defined (3,5) as OFPBIC_UNSUP_EXP_INST, then
* OpenFlow 1.2 broke this error into OFPBIC_BAD_EXPERIMENTER as (3,5) and
* OFPBIC_BAD_EXT_TYPE as (3,6). To allow the OVS code to report just a single
* error code, instead of protocol version dependent errors, this list of
* errors only lists the latter two errors, giving both of them the same code
* (3,5) for OpenFlow 1.1. Then, when OVS serializes either error into
* OpenFlow 1.1, it uses the same code (3,5). In the other direction, when OVS
* deserializes (3,5) from OpenFlow 1.1, it translates it into
* OFPBIC_BAD_EXPERIMENTER (because its definition precedes that of
* OFPBIC_BAD_EXT_TYPE below). See the "encoding OFPBIC_* experimenter errors"
* and "decoding OFPBIC_* experimenter errors" tests in tests/ofp-errors.at for
* full details.
*/
enum ofperr {
/* Expected duplications. */