DAOS-17109 cart: clients URI lookup of rank0 can lead to crash

[frostedcmos]

• Cart group was incorrectly leaving gp_psr_rank field to 0, causing issues when rank=0 was being looked up.

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[github-actions]

Ticket title is 'self_test issues with tcp provider'
Status is 'Open'
https://daosio.atlassian.net/browse/DAOS-17109

[knard38]

Tested and validated on wolf cluster.

[soumagne]

how does setting it to no rank fix the issue ? the title says look up of rank 0, is rank 0 set to CRT_NO_RANK ?

[frostedcmos]

during URI_LOOKUP handling there is a following logic block:
if (base_addr == NULL && !crt_is_service()) { D_RWLOCK_RDLOCK(&grp_priv->gp_rwlock); if (tgt_ep->ep_rank == grp_priv->gp_psr_rank && dst_tag == 0) { D_STRNDUP(uri, grp_priv->gp_psr_uri, CRT_ADDR_STR_MAX_LEN); D_RWLOCK_UNLOCK(&grp_priv->gp_rwlock);

If rank being looked up (tgt_ep->ep_rank) matches a psr_rank then we can use psr's uri.
The problem is that we inialized before gp_psr_rank to 0, causing this block then to assume that psr rank has been set (to 0) and therefor gp_psr_uri is valid.

Setting gp_psr_rank to CRT_NO_RANK at init ensures 'gp_psr_rank' is treated properly in checks like above.