I noticed that under certain circumstances, GID 0 for some interfaces is reported as all 0s, or empty.
This seems to be correlated with code in drivers/infiniband/core/roce_gid_mgmt.c in the routine
ndev_event_link(), which does this:
/*
* When a lower netdev is linked to its upper bonding
* netdev, delete lower slave netdev's default GIDs.
*/
cmds[0] = bonding_default_del_cmd;
cmds[0].ndev = event_ndev;
cmds[0].filter_ndev = changeupper_info->upper_dev;
bonding_default_del_cmd will result in a call to del_default_gids().
However, given version 1.2.1 of the IB spec, looking at page 145, line 20:
4.1.1 GID USAGE AND PROPERTIES
1) Each endport shall be assigned at least one unicast GID. The first unicast GID assigned shall be
created using the manufacturer assigned EUI-64 identifier. This GID is referred to as GID index 0
and is formed by techniques 3(a) or 3(b) described below.
2) The default GID prefix shall be (0xFE80::0). A packet using the default GID prefix and either a
manufacturer assigned or SM assigned EUI-64 must always be accepted by an endnode. A packet
containing a GRH with a destination GID with this prefix must never be forwarded by a router,
i.e. it is restricted to the local subnet.
3) A unicast GID shall be created using one or more of the following mechanisms:
a) Concatenation of the default GID prefix with the manufacturer as
signed EUI-64 identifier associated with an endport. This GID is
referred to as the default GID.
b) Concatenation of a subnet manager assigned 64-bit GID prefix and the
manufacturer assigned EUI-64 identifier associated with an endport.
c) Assignment of a GID by the subnet manager. The subnet manager creates a
GID by concatenating the GID prefix (default or assigned) with a set of
locally assigned EUI-64 values (at GID index 1 or above).
Each endport must be assigned at least one unicast GID using (a). Additional
GIDs may be assigned using (b) and/or (c). Note: A subnet 2 shall only have
one assigned GID prefix (non default) at any given time.
make_default_gid()and add default_gids() seem to have that all taken care of.
What concerns me is the code that removes GID index 0, as page 436, line 35, states:
C10-2: For each GID Table, the first entry in the table shall contain the read-only invariant value of GID index 0.
So is it actually OK to remove GID 0 when removing default GIDs via del_default_gids(), or should it be preserving GID index 0 at all times?
This is because it appears a call to rdma_query_gid() (as in ib_find_gid()) will return -EINVAL for a table if GID 0 has been deleted.
Am I misreading the spec, or is there a bug here?
Thanks,
William Kucharski
