mc: guid: Implement encoding autodetection

With this commit the GUID encoding is now by default detected
automatically based on the validity of the version field,
and the timestamp (for time-based version 1 GUIDs).

The version is considered valid if it is 1 through 5.
The timestamp is considered valid if the year is past UNIX Epoch
and before the current year.

Resolves ipmitool/ipmitool#25

Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>

1 files changed, 34 insertions, 10 deletions

diff --git a/doc/ipmitool.1 b/doc/ipmitool.1
index 197c5b9..fd084e6 100644
--- a/doc/ipmitool.1
+++ b/doc/ipmitool.1
@@ -2023,11 +2023,35 @@ Display the Management Controller Globally Unique IDentifier.
 
 .RS
 .TP
-\fIsmbios\fP
+\fIauto\fP
 .br
 
-This is the default behavior for ipmitool for the sake of compatibility
-with old versions and broken BMC implementations whose number is legion.
+This is the default behavior for
+.BR ipmitool (1).
+
+Try to automatically detect the encoding based on the value of the
+version field and (for version 1) the timestamp. The version is
+considered valid if it is 1 through 5, and the timestamp is valid
+if the year is past or equal to UNIX Epoch (1970) and is before or
+equal to the current year.
+
+If multiple encodings happen to have valid version fields, then
+precedence takes the one with version 1 and a valid timestamp. If
+neither one has that, then the precedence order is as follows:
+\fIsmbios\fP, \fIipmi\fP, \fIrfc4122\fP.
+
+If neither encoding yields a valid version field, then
+.BR ipmitool (1)
+defaults to \fIdump\fP mode.
+
+If this option is in use, then
+.BR ipmitool (1)
+will also print out the detected encoding and warn
+regarding IPMI specification violation if the encoding isn't \fIipmi\fP.
+
+.TP
+\fIsmbios\fP
+.br
 
 Decode GUID as if it was sent by BMC as prescribed by SMBIOS specification.
 
@@ -2036,6 +2060,13 @@ it this way. If your BMC's GUID is shown correctly using this option, you
 may want to inform your BMC manufacturer that they have a bug.
 
 .TP
+\fIipmi\fP
+.br
+
+Decode GUID according to IPMI specification. It MUST show the correct GUID.
+If it doesn't, try other options and inform your BMC manufacturer of the bug.
+
+.TP
 \fIrfc4122\fP or \fIrfc\fP
 .br
 
@@ -2046,13 +2077,6 @@ If your BMC's GUID is shown correctly using this option, you
 may want to inform your BMC manufacturer that they have a bug.
 
 .TP
-\fIipmi\fP
-.br
-
-Decode GUID according to IPMI specification. It MUST show the correct GUID.
-If it doesn't, try other options above and inform your BMC manufacturer of the bug.
-
-.TP
 \fIdump\fP
 .br