/* * Copyright (c) 2016 Cisco and/or its affiliates. * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at: * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include #include #include /** * @file * @brief Feature Subgraph Ordering. Dynamically compute feature subgraph ordering by performing a topological sort across a set of "feature A before feature B" and "feature C after feature B" constraints. Use the topological sort result to set up vnet_config_main_t's for use at runtime. Feature subgraph arcs are simple enough. They start at specific fixed nodes, and end at specific fixed nodes. In between, a per-interface current feature configuration dictates which additional nodes each packet visits. Each so-called feature node can [of course] drop any specific packet. See ip4_forward.c, ip6_forward.c in this directory to see the current rx-unicast, rx-multicast, and tx feature subgraph arc definitions. Let's say that we wish to add a new feature to the ip4 unicast feature subgraph arc, which needs to run before @c ip4-lookup. In either base code or a plugin,
    \#include 
    
and add the new feature as shown:
    VNET_FEATURE_INIT (ip4_lookup, static) =
    {
      .arc_name = "ip4-unicast",
      .node_name = "my-ip4-unicast-feature",
      .runs_before = VLIB_FEATURES ("ip4-lookup")
    };
    
Here's the standard coding pattern to enable / disable @c my-ip4-unicast-feature on an interface:

    sw_if_index = 
    vnet_feature_enable_disable ("ip4-unicast", "my-ip4-unicast-feature",
                                 sw_if_index, 1 );
    
Here's how to obtain the correct next node index in packet processing code, aka in the implementation of @c my-ip4-unicast-feature:
    vnet_feature_next (sw_if_index0, &next0, b0);

    
Nodes are free to drop or otherwise redirect packets. Packets which "pass" should be enqueued via the next0 arc computed by vnet_feature_next. */ static int comma_split (u8 * s, u8 ** a, u8 ** b) { *a = s; while (*s && *s != ',') s++; if (*s == ',') *s = 0; else return 1; *b = (u8 *) (s + 1); return 0; } /** * @brief Initialize a feature graph arc * @param vm vlib main structure pointer * @param vcm vnet config main structure pointer * @param feature_start_nodes names of start-nodes which use this * feature graph arc * @param num_feature_start_nodes number of start-nodes * @param first_reg first element in * [an __attribute__((constructor)) function built, or * otherwise created] singly-linked list of feature registrations * @param first_const first element in * [an __attribute__((constructor)) function built, or * otherwise created] singly-linked list of bulk order constraints * @param [out] in_feature_nodes returned vector of * topologically-sorted feature node names, for use in * show commands * @returns 0 on success, otherwise an error message. Errors * are fatal since they invariably involve mistyped node-names, or * genuinely missing node-names */ clib_error_t * vnet_feature_arc_init (vlib_main_t * vm, vnet_config_main_t * vcm, char **feature_start_nodes, int num_feature_start_nodes, char *last_in_arc, vnet_feature_registration_t * first_reg, vnet_feature_constraint_registration_t * first_const_set, char ***in_feature_nodes) { uword *index_by_name; uword *reg_by_index; u8 **node_names = 0; u8 *node_name; char *prev_name; char **these_constraints; char *this_constraint_c; u8 **constraints = 0; u8 *constraint_tuple; u8 *this_constraint; u8 **orig, **closure; uword *p; int i, j, k; u8 *a_name, *b_name; int a_index, b_index; int n_features; u32 *result = 0; vnet_feature_registration_t *this_reg = 0; vnet_feature_constraint_registration_t *this_const_set = 0; char **feature_nodes = 0; hash_pair_t *hp; u8 **keys_to_delete = 0; index_by_name = hash_create_string (0, sizeof (uword)); reg_by_index = hash_create (0, sizeof (uword)); this_reg = first_reg; /* Autogenerate before constraints */ if (last_in_arc) { while (this_reg) { /* If this isn't the last node in the arc... */ if (clib_strcmp (this_reg->node_name, last_in_arc)) { /* * Add an explicit constraint so this feature will run * before the last node in the arc */ constraint_tuple = format (0, "%s,%s%c", this_reg->node_name, last_in_arc, 0); vec_add1 (constraints, constraint_tuple); } this_reg = this_reg->next_in_arc; } this_reg = first_reg; } /* pass 1, collect feature node names, construct a before b pairs */ while (this_reg) { node_name = format (0, "%s%c", this_reg->node_name, 0); hash_set (reg_by_index, vec_len (node_names), (uword) this_reg); hash_set_mem (index_by_name, node_name, vec_len (node_names)); vec_add1 (node_names, node_name); these_constraints = this_reg->runs_before; while (these_constraints && these_constraints[0]) { this_constraint_c = these_constraints[0]; constraint_tuple = format (0, "%s,%s%c", node_name, this_constraint_c, 0); vec_add1 (constraints, constraint_tuple); these_constraints++; } these_constraints = this_reg->runs_after; while (these_constraints && these_constraints[0]) { this_constraint_c = these_constraints[0]; constraint_tuple = format (0, "%s,%s%c", this_constraint_c, node_name, 0); vec_add1 (constraints, constraint_tuple); these_constraints++; } this_reg = this_reg->next_in_arc; } /* pass 2, collect bulk "a then b then c then d" constraints */ this_const_set = first_const_set; while (this_const_set) { these_constraints = this_const_set->node_names; prev_name = 0; /* Across the list of constraints */ while (these_constraints && these_constraints[0]) { this_constraint_c = these_constraints[0]; p = hash_get_mem (index_by_name, this_constraint_c); if (p == 0) { clib_warning ("bulk constraint feature node '%s' not found for arc '%s'", this_constraint_c); these_constraints++; continue; } if (prev_name == 0) { prev_name = this_constraint_c; these_constraints++; continue; } constraint_tuple = format (0, "%s,%s%c", prev_name, this_constraint_c, 0); vec_add1 (constraints, constraint_tuple); prev_name = this_constraint_c; these_constraints++; } this_const_set = this_const_set->next_in_arc; } n_features = vec_len (node_names); orig = clib_ptclosure_alloc (n_features); for (i = 0; i < vec_len (constraints); i++) { this_constraint = constraints[i]; if (comma_split (this_constraint, &a_name, &b_name)) return clib_error_return (0, "comma_split failed!"); p = hash_get_mem (index_by_name, a_name); /* * Note: the next two errors mean that something is * b0rked. As in: if you code "A depends on B," and you forget * to define a FEATURE_INIT macro for B, you lose. * Nonexistent graph nodes are tolerated. */ if (p == 0) { clib_warning ("feature node '%s' not found (before '%s', arc '%s')", a_name, b_name, first_reg->arc_name); continue; } a_index = p[0]; p = hash_get_mem (index_by_name, b_name); if (p == 0) { clib_warning ("feature node '%s' not found (after '%s', arc '%s')", b_name, a_name, first_reg->arc_name); continue; } b_index = p[0]; /* add a before b to the original set of constraints */ orig[a_index][b_index] = 1; vec_free (this_constraint); } /* Compute the positive transitive closure of the original constraints */ closure = clib_ptclosure (orig); /* Compute a partial order across feature nodes, if one exists. */ again: for (i = 0; i < n_features; i++) { for (j = 0; j < n_features; j++) { if (closure[i][j]) goto item_constrained; } /* Item i can be output */ vec_add1 (result, i); { for (k = 0; k < n_features; k++) closure[k][i] = 0; /* * Add a "Magic" a before a constraint. * This means we'll never output it again */ closure[i][i] = 1; goto again; } item_constrained: ; } /* see if we got a partial order... */ if (vec_len (result) != n_features) return clib_error_return (0, "Arc '%s': failed to find a suitable feature order!", first_reg->arc_name); /* * We win. * Bind the index variables, and output the feature node name vector * using the partial order we just computed. Result is in stack * order, because the entry with the fewest constraints (e.g. none) * is output first, etc. */ for (i = n_features - 1; i >= 0; i--) { p = hash_get (reg_by_index, result[i]); ASSERT (p != 0); this_reg = (vnet_feature_registration_t *) p[0]; if (this_reg->feature_index_ptr) *this_reg->feature_index_ptr = n_features - (i + 1); this_reg->feature_index = n_features - (i + 1); vec_add1 (feature_nodes, this_reg->node_name); } /* Set up the config infrastructure */ vnet_config_init (vm, vcm, feature_start_nodes, num_feature_start_nodes, feature_nodes, vec_len (feature_nodes)); /* Save a copy for show command */ *in_feature_nodes = feature_nodes; /* Finally, clean up all the shit we allocated */ hash_foreach_pair (hp, index_by_name, ({ vec_add1 (keys_to_delete, (u8 *)hp->key); })); hash_free (index_by_name); for (i = 0; i < vec_len (keys_to_delete); i++) vec_free (keys_to_delete[i]); vec_free (keys_to_delete); hash_free (reg_by_index); vec_free (result); clib_ptclosure_free (orig); clib_ptclosure_free (closure); return 0; } /* * fd.io coding-style-patch-verification: ON * * Local Variables: * eval: (c-set-style "gnu") * End: */