[ofw] ib_portinfo_record_t padding history?

[Fab Tillier]

Smith, Stan wrote on Tue, 18 May 2010 at 14:18:09

> Indeed a problem arises in osmtest when building a fabric inventory
> file 'osmtest.dat' via 'osmtest -f c'.
> The problem is exactly that of an SA response containing an array of
> ib_portinfo_records.
> With the padding the 2nd ib_portinfo_record[1] index computation is
> incorrectly offset by 2 bytes.

Is the array being addressed as an array, or each entry being accessed using ib_get_query_result (or ib_get_query_portinfo_rec?)

Which direction are you off by 2?  Is the next entry 2 bytes too soon, or two bytes too late?

> Without the padding the index calculation is correct. This observation
> led me to the comparison of the Linux vs. Windows ib_portinfo_record_t
> definitions and subsequent removal of the padding.
> I agree the padding should not have been an issue; all things coded
> correctly.
> 
> Digging further into the issue, I find the following Windows vs. Linux
> definition:
> 
> AL_INLINE ib_net16_t AL_API
> ib_get_attr_offset(
>         IN              const   uint32_t
> attr_size )
> {
>         if( attr_size & 0x07 )
>                 return( cl_hton16( (uint16_t)(attr_size >> 3) + 1 ) );
>         else
>                 return( cl_hton16( (uint16_t)(attr_size >> 3) ) );
> }

Unpadded, sizeof(ib_portinfo_record_t) gives 58, and ib_get_attr_offset( 58 ) returns 8.  Padded it gives 64 and ib_get_attr_offset( 64 ) also returns 8.

> Linux
> 
> static inline ib_net16_t AL_API
> ib_get_attr_offset(const uint32_t attr_size )
> {
>         return( cl_hton16( (uint16_t)(attr_size >> 3) ) );
> }

Unpadded, sizeof(ib_portinfo_record_t) gives 58, and ib_get_attr_offset( 58 ) returns 7.  Padded it gives 64 and ib_get_attr_offset( 64 ) also returns 8.

> 
> 'attr_size' is passed in osmtest.c as 'sizeof(ib_portinfo_record_t)'
> when building an SA query.

You're running osmtest on Windows against OpenSM on Linux?  Or both on Windows?  Both on Linux?

> I suspect this is the root of the problem, as osmtest.c code which
> builds the SA query for all known portinfo records sets the madw
> attr_size as '(attr_size >> 3)'.

The attr_size is only valid in RMPP DATA packets.  Is the query using RMPP?  If not, the spec says that the field is ignored.

> The question becomes 'which is the correct version of
> ib_get_attr_offset()?'.

The Windows version seems correct, especially if you don't have padding in the structure.  The Linux version will tell you the next attribute will start 56 bytes after the first, giving you an off-by-two error.  So using unpadded in conjunction with the Linux ib_get_attr_offset will give you the wrong offset.

Can you check that offset is 8, not 7, in the RMPP response to the query?

-Fab