2 * Copyright (c) 2016 Cisco and/or its affiliates.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at:
7 * http://www.apache.org/licenses/LICENSE-2.0
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
16 #include <vnet/vnet.h>
17 #include <vnet/ip/ip.h>
18 #include <vnet/mpls/mpls.h>
22 * @brief Feature Subgraph Ordering.
24 Dynamically compute feature subgraph ordering by performing a
25 topological sort across a set of "feature A before feature B" and
26 "feature C after feature B" constraints.
28 Use the topological sort result to set up vnet_config_main_t's for
31 Feature subgraph arcs are simple enough. They start at specific
32 fixed nodes, and end at specific fixed nodes. In between, a
33 per-interface current feature configuration dictates which
34 additional nodes each packet visits. Each so-called feature node
35 can [of course] drop any specific packet.
37 See ip4_forward.c, ip6_forward.c in this directory to see the
38 current rx-unicast, rx-multicast, and tx feature subgraph arc
41 Let's say that we wish to add a new feature to the ip4 unicast
42 feature subgraph arc, which needs to run before @c ip4-lookup. In
43 either base code or a plugin,
45 \#include <vnet/feature/feature.h>
48 and add the new feature as shown:
51 VNET_FEATURE_INIT (ip4_lookup, static) =
53 .arch_name = "ip4-unicast",
54 .node_name = "my-ip4-unicast-feature",
55 .runs_before = VLIB_FEATURES ("ip4-lookup")
59 Here's the standard coding pattern to enable / disable
60 @c my-ip4-unicast-feature on an interface:
64 sw_if_index = <interface-handle>
65 vnet_feature_enable_disable ("ip4-unicast", "my-ip4-unicast-feature",
69 Here's how to obtain the correct next node index in packet
70 processing code, aka in the implementation of @c my-ip4-unicast-feature:
73 vnet_feature_next (sw_if_index0, &next0, b0);
77 Nodes are free to drop or otherwise redirect packets. Packets
78 which "pass" should be enqueued via the next0 arc computed by
84 comma_split (u8 * s, u8 ** a, u8 ** b)
88 while (*s && *s != ',')
101 * @brief Initialize a feature graph arc
102 * @param vm vlib main structure pointer
103 * @param vcm vnet config main structure pointer
104 * @param feature_start_nodes names of start-nodes which use this
106 * @param num_feature_start_nodes number of start-nodes
107 * @param first_reg first element in
108 * [an __attribute__((constructor)) function built, or
109 * otherwise created] singly-linked list of feature registrations
110 * @param [out] in_feature_nodes returned vector of
111 * topologically-sorted feature node names, for use in
113 * @returns 0 on success, otherwise an error message. Errors
114 * are fatal since they invariably involve mistyped node-names, or
115 * genuinely missing node-names
118 vnet_feature_arc_init (vlib_main_t * vm,
119 vnet_config_main_t * vcm,
120 char **feature_start_nodes,
121 int num_feature_start_nodes,
122 vnet_feature_registration_t * first_reg,
123 char ***in_feature_nodes)
125 uword *index_by_name;
129 char **these_constraints;
130 char *this_constraint_c;
131 u8 **constraints = 0;
132 u8 *constraint_tuple;
134 u8 **orig, **closure;
138 int a_index, b_index;
141 vnet_feature_registration_t *this_reg = 0;
142 char **feature_nodes = 0;
144 u8 **keys_to_delete = 0;
146 index_by_name = hash_create_string (0, sizeof (uword));
147 reg_by_index = hash_create (0, sizeof (uword));
149 this_reg = first_reg;
151 /* pass 1, collect feature node names, construct a before b pairs */
154 node_name = format (0, "%s%c", this_reg->node_name, 0);
155 hash_set (reg_by_index, vec_len (node_names), (uword) this_reg);
157 hash_set_mem (index_by_name, node_name, vec_len (node_names));
159 vec_add1 (node_names, node_name);
161 these_constraints = this_reg->runs_before;
162 while (these_constraints && these_constraints[0])
164 this_constraint_c = these_constraints[0];
166 constraint_tuple = format (0, "%s,%s%c", node_name,
167 this_constraint_c, 0);
168 vec_add1 (constraints, constraint_tuple);
172 these_constraints = this_reg->runs_after;
173 while (these_constraints && these_constraints[0])
175 this_constraint_c = these_constraints[0];
177 constraint_tuple = format (0, "%s,%s%c",
178 this_constraint_c, node_name, 0);
179 vec_add1 (constraints, constraint_tuple);
183 this_reg = this_reg->next;
186 n_features = vec_len (node_names);
187 orig = clib_ptclosure_alloc (n_features);
189 for (i = 0; i < vec_len (constraints); i++)
191 this_constraint = constraints[i];
193 if (comma_split (this_constraint, &a_name, &b_name))
194 return clib_error_return (0, "comma_split failed!");
196 p = hash_get_mem (index_by_name, a_name);
198 * Note: the next two errors mean that something is
199 * b0rked. As in: if you code "A depends on B," and you forget
200 * to define a FEATURE_INIT macro for B, you lose.
201 * Nonexistent graph nodes are tolerated.
205 clib_warning ("feature node '%s' not found", a_name);
210 p = hash_get_mem (index_by_name, b_name);
213 clib_warning ("feature node '%s' not found", b_name);
218 /* add a before b to the original set of constraints */
219 orig[a_index][b_index] = 1;
220 vec_free (this_constraint);
223 /* Compute the positive transitive closure of the original constraints */
224 closure = clib_ptclosure (orig);
226 /* Compute a partial order across feature nodes, if one exists. */
228 for (i = 0; i < n_features; i++)
230 for (j = 0; j < n_features; j++)
233 goto item_constrained;
235 /* Item i can be output */
236 vec_add1 (result, i);
238 for (k = 0; k < n_features; k++)
241 * Add a "Magic" a before a constraint.
242 * This means we'll never output it again
251 /* see if we got a partial order... */
252 if (vec_len (result) != n_features)
253 return clib_error_return (0, "%d feature_init_cast no partial order!");
257 * Bind the index variables, and output the feature node name vector
258 * using the partial order we just computed. Result is in stack
259 * order, because the entry with the fewest constraints (e.g. none)
260 * is output first, etc.
263 for (i = n_features - 1; i >= 0; i--)
265 p = hash_get (reg_by_index, result[i]);
267 this_reg = (vnet_feature_registration_t *) p[0];
268 if (this_reg->feature_index_ptr)
269 *this_reg->feature_index_ptr = n_features - (i + 1);
270 this_reg->feature_index = n_features - (i + 1);
271 vec_add1 (feature_nodes, this_reg->node_name);
274 /* Set up the config infrastructure */
275 vnet_config_init (vm, vcm,
277 num_feature_start_nodes,
278 feature_nodes, vec_len (feature_nodes));
280 /* Save a copy for show command */
281 *in_feature_nodes = feature_nodes;
283 /* Finally, clean up all the shit we allocated */
285 hash_foreach_pair (hp, index_by_name,
287 vec_add1 (keys_to_delete, (u8 *)hp->key);
290 hash_free (index_by_name);
291 for (i = 0; i < vec_len (keys_to_delete); i++)
292 vec_free (keys_to_delete[i]);
293 vec_free (keys_to_delete);
294 hash_free (reg_by_index);
296 clib_ptclosure_free (orig);
297 clib_ptclosure_free (closure);
302 * fd.io coding-style-patch-verification: ON
305 * eval: (c-set-style "gnu")