Re: [dpdk-dev] [PATCH 1/2] doc: add programmer's guide for the RIB library

["Walsh, Conor" <conor.walsh@intel.com>]

> From: dev <dev-bounces@dpdk.org> On Behalf Of Vladimir Medvedkin
> Sent: Monday 8 November 2021 17:37
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH 1/2] doc: add programmer's guide for the RIB
> library
> 
> Currently, programmer's guide for the RIB library is missing.
> This commit adds it.
> 
> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
> ---
>  doc/guides/prog_guide/img/rib_internals.svg | 148 +++++++++++++++++
>  doc/guides/prog_guide/img/rib_pic.svg       | 152 +++++++++++++++++
>  doc/guides/prog_guide/index.rst             |   1 +
>  doc/guides/prog_guide/rib_lib.rst           | 172 ++++++++++++++++++++
>  4 files changed, 473 insertions(+)
>  create mode 100644 doc/guides/prog_guide/img/rib_internals.svg
>  create mode 100644 doc/guides/prog_guide/img/rib_pic.svg
>  create mode 100644 doc/guides/prog_guide/rib_lib.rst
> 

<snip>

> +   RIB prefix independent convergence
> +
> +In case of a next hop failure, we need to replace an active failed next hop
> with a
> +feasible next hop for every corresponding route without waiting for the
> routing daemon
> +recalculation process to complete.
> +To achieve this we can link all existing routes with the same active next hop
> in a linked list,
> +saving the feasible next hop ID and a pointer inside the extension space of
> each ``rte_rib_node``.
> +
> +.. code-block:: c
> +
> +      struct my_route_ext {
> +         struct rte_rib_node *next;
> +         uint64_t feasible_nh;
> +      };
> +
> +      struct rte_rib_conf conf;
> +      conf.ext_sz = sizeof(struct my_route_ext);
> +      rib = rte_rib_create("test", 0, &conf);
> +      ...
> +      /* routing daemon task */
> +      struct rte_rib_node *route = rte_rib_insert(rib, RTE_IPV4(192,0,2,0), 24);
> +      rte_rib_set_nh(route, active_nh_from_rd);
> +      struct my_route_ext *ext = rte_rib_get_ext(route);
> +      ext->feasible_nh = feasible_nh_from_rd;
> +      list_insert(nh_table[active_nh_from_rd].list_head, route);
> +      ...
> +      /* dataplane monitoring thread */
> +      /* nexthop id fail_nh fails */
                ^^^^^^^

> +      route = NULL;
> +      do {
> +         route = get_next(nh_table[fail_nh].list_head, route);
> +         uint32_t ip;
> +         uint8_t depth;
> +         rte_rib_get_ip(route, &ip);
> +         rte_rib_get_depth(route, &depth);
> +         ext = rte_rib_get_ext(route);
> +         uint64_t new_nh = ext->feasible_nh;
> +         /* do update to the dataplane, for example to the fib */
> +         rte_fib_add(fib, ip, depth, new_nh);
> +         /* update nexthop if necessary */
                                 ^^^^^^^
These two comments are showing as spelling errors on aspell but I think they are ok as this is technically a code comment
and nexthop often appears in the code without a space.

> +         rte_rib_set_nh(route, new_nh);
> +      } while (route != NULL);
> +
> --
> 2.25.1

Reviewed-by: Conor Walsh <conor.walsh@intel.com>