From: dev <redacted> 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 <redacted>
---
 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 <redacted>