[ewg] Re: [PATCH v3] libibmad: Handle MAD redirection

[Joachim Fenkes]

Hal Rosenstock <hal.rosenstock at gmail.com> wrote on 01.07.2009 15:59:41:

> > +static int redirect_port(ib_portid_t *port, uint8_t *mad)
> > +{
> > +       port->lid = mad_get_field(mad, 64, IB_CPI_REDIRECT_LID_F);
> > +       if (!port->lid) {
> > +               IBWARN("GID-based redirection is not supported");
> > +               return -1;
> > +       }
> 
> Sorry for the confusion: determination of GID redirection should be
> based on a comparison of the RedirectGID to 0. It's valid to supply
> both a non zero RedirectGID and RedirectLID.

Are you sure?

About the Redirection GID, the spec says "If redirection is not being
performed, this shall be set to zero", so if redirection _is_ being
performed, the GID may or may not be zero without any explicit 
implication.

For the LID, it says "If this value is zero, the redirect requires the
requester to use the supplied RedirectGID to request further path 
resolution
from subnet administration." To me, this explicitly states that a zero LID
means that the GID must be used.

If both LID and GID are non-zero, it is not specified whether the 
requester
should use the LID or the GID, so I choose to always use the LID as long
as it's non-zero, because that's what the code supports.

Am I talking crazy or does this make sense to you?

> > +
> > +       port->qp = mad_get_field(mad, 64, IB_CPI_REDIRECT_QP_F);
> > +       port->qkey = mad_get_field(mad, 64, IB_CPI_REDIRECT_QKEY_F);
> > +       port->sl = mad_get_field(mad, 64, IB_CPI_REDIRECT_SL_F);
> > +
> > +       /* TODO: Reverse map redirection P_Key to P_Key index */
> > +
> > +       if (ibdebug)
> > +               IBWARN("redirected to lid 0x%x, qp 0x%x, qkey 0x%x, sl 
0x%x",
> > +                      port->lid, port->qp, port->qkey, port->sl);
> 
> Unicast LIDs should be displayed in decimal rather than hex.

Couldn't you have noticed this in the first patch? ;) I'll change it.

Cheers,
  Joachim