lib/command_parse.y

   1 /*
   2  * Command format string parser for CLI backend.
   3  *
   4  * --
   5  * Copyright (C) 2016 Cumulus Networks, Inc.
   6  *
   7  * This file is part of GNU Zebra.
   8  *
   9  * GNU Zebra is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU General Public License as published by the
  11  * Free Software Foundation; either version 2, or (at your option) any
  12  * later version.
  13  *
  14  * GNU Zebra is distributed in the hope that it will be useful, but
  15  * WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with GNU Zebra; see the file COPYING.  If not, write to the Free
  21  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  22  * 02111-1307, USA.
  23  */
  24
  25 %{
  26 // compile with debugging facilities
  27 #define YYDEBUG 1
  28 %}
  29
  30 %locations
  31 /* define parse.error verbose */
  32 %define api.pure full
  33 /* define api.prefix {cmd_yy} */
  34
  35 /* names for generated header and parser files */
  36 %defines "lib/command_parse.h"
  37 %output  "lib/command_parse.c"
  38
  39 /* note: code blocks are output in order, to both .c and .h:
  40  *  1. %code requires
  41  *  2. %union + bison forward decls
  42  *  3. %code provides
  43  * command_lex.h needs to be included at 3.; it needs the union and YYSTYPE.
  44  * struct parser_ctx is needed for the bison forward decls.
  45  */
  46 %code requires {
  47   #include "config.h"
  48
  49   #include <stdbool.h>
  50   #include <stdlib.h>
  51   #include <string.h>
  52   #include <ctype.h>
  53
  54   #include "command_graph.h"
  55   #include "log.h"
  56
  57   DECLARE_MTYPE(LEX)
  58
  59   #define YYSTYPE CMD_YYSTYPE
  60   #define YYLTYPE CMD_YYLTYPE
  61   struct parser_ctx;
  62
  63   /* subgraph semantic value */
  64   struct subgraph {
  65     struct graph_node *start, *end;
  66   };
  67 }
  68
  69 %union {
  70   long long number;
  71   char *string;
  72   struct graph_node *node;
  73   struct subgraph subgraph;
  74 }
  75
  76 %code provides {
  77   #ifndef FLEX_SCANNER
  78   #include "command_lex.h"
  79   #endif
  80
  81   extern void set_lexer_string (yyscan_t *scn, const char *string);
  82   extern void cleanup_lexer (yyscan_t *scn);
  83
  84   struct parser_ctx {
  85     yyscan_t scanner;
  86
  87     const struct cmd_element *el;
  88
  89     struct graph *graph;
  90     struct graph_node *currnode;
  91
  92     /* pointers to copy of command docstring */
  93     char *docstr_start, *docstr;
  94   };
  95 }
  96
  97 /* union types for lexed tokens */
  98 %token <string> WORD
  99 %token <string> IPV4
 100 %token <string> IPV4_PREFIX
 101 %token <string> IPV6
 102 %token <string> IPV6_PREFIX
 103 %token <string> VARIABLE
 104 %token <string> RANGE
 105 %token <string> MAC
 106 %token <string> MAC_PREFIX
 107
 108 /* union types for parsed rules */
 109 %type <node> start
 110 %type <node> literal_token
 111 %type <node> placeholder_token
 112 %type <node> placeholder_token_real
 113 %type <node> simple_token
 114 %type <subgraph> selector
 115 %type <subgraph> selector_token
 116 %type <subgraph> selector_token_seq
 117 %type <subgraph> selector_seq_seq
 118
 119 %type <string> varname_token
 120
 121 %code {
 122
 123   /* bison declarations */
 124   void
 125   cmd_yyerror (CMD_YYLTYPE *locp, struct parser_ctx *ctx, char const *msg);
 126
 127   /* helper functions for parser */
 128   static const char *
 129   doc_next (struct parser_ctx *ctx);
 130
 131   static struct graph_node *
 132   new_token_node (struct parser_ctx *,
 133                   enum cmd_token_type type,
 134                   const char *text,
 135                   const char *doc);
 136
 137   static void
 138   terminate_graph (CMD_YYLTYPE *locp, struct parser_ctx *ctx,
 139                    struct graph_node *);
 140
 141   static void
 142   cleanup (struct parser_ctx *ctx);
 143
 144   static void loopcheck(struct parser_ctx *ctx, struct subgraph *sg);
 145
 146   #define scanner ctx->scanner
 147 }
 148
 149 /* yyparse parameters */
 150 %lex-param {yyscan_t scanner}
 151 %parse-param {struct parser_ctx *ctx}
 152
 153 /* called automatically before yyparse */
 154 %initial-action {
 155   /* clear state pointers */
 156   ctx->currnode = vector_slot (ctx->graph->nodes, 0);
 157
 158   /* copy docstring and keep a pointer to the copy */
 159   if (ctx->el->doc)
 160   {
 161     // allocate a new buffer, making room for a flag
 162     size_t length = (size_t) strlen (ctx->el->doc) + 2;
 163     ctx->docstr = malloc (length);
 164     memcpy (ctx->docstr, ctx->el->doc, strlen (ctx->el->doc));
 165     // set the flag so doc_next knows when to print a warning
 166     ctx->docstr[length - 2] = 0x03;
 167     // null terminate
 168     ctx->docstr[length - 1] = 0x00;
 169   }
 170   ctx->docstr_start = ctx->docstr;
 171 }
 172
 173 %%
 174
 175 start:
 176   cmd_token_seq
 177 {
 178   // tack on the command element
 179   terminate_graph (&@1, ctx, ctx->currnode);
 180 }
 181 | cmd_token_seq placeholder_token '.' '.' '.'
 182 {
 183   if ((ctx->currnode = graph_add_edge (ctx->currnode, $2)) != $2)
 184     graph_delete_node (ctx->graph, $2);
 185
 186   ((struct cmd_token *)ctx->currnode->data)->allowrepeat = 1;
 187
 188   // adding a node as a child of itself accepts any number
 189   // of the same token, which is what we want for variadics
 190   graph_add_edge (ctx->currnode, ctx->currnode);
 191
 192   // tack on the command element
 193   terminate_graph (&@1, ctx, ctx->currnode);
 194 }
 195 ;
 196
 197 varname_token: '$' WORD
 198 {
 199   $$ = $2;
 200 }
 201 | /* empty */
 202 {
 203   $$ = NULL;
 204 }
 205 ;
 206
 207 cmd_token_seq:
 208   /* empty */
 209 | cmd_token_seq cmd_token
 210 ;
 211
 212 cmd_token:
 213   simple_token
 214 {
 215   if ((ctx->currnode = graph_add_edge (ctx->currnode, $1)) != $1)
 216     graph_delete_node (ctx->graph, $1);
 217 }
 218 | selector
 219 {
 220   graph_add_edge (ctx->currnode, $1.start);
 221   ctx->currnode = $1.end;
 222 }
 223 ;
 224
 225 simple_token:
 226   literal_token
 227 | placeholder_token
 228 ;
 229
 230 literal_token: WORD varname_token
 231 {
 232   $$ = new_token_node (ctx, WORD_TKN, $1, doc_next(ctx));
 233   cmd_token_varname_set ($$->data, $2);
 234   XFREE (MTYPE_LEX, $2);
 235   XFREE (MTYPE_LEX, $1);
 236 }
 237 ;
 238
 239 placeholder_token_real:
 240   IPV4
 241 {
 242   $$ = new_token_node (ctx, IPV4_TKN, $1, doc_next(ctx));
 243   XFREE (MTYPE_LEX, $1);
 244 }
 245 | IPV4_PREFIX
 246 {
 247   $$ = new_token_node (ctx, IPV4_PREFIX_TKN, $1, doc_next(ctx));
 248   XFREE (MTYPE_LEX, $1);
 249 }
 250 | IPV6
 251 {
 252   $$ = new_token_node (ctx, IPV6_TKN, $1, doc_next(ctx));
 253   XFREE (MTYPE_LEX, $1);
 254 }
 255 | IPV6_PREFIX
 256 {
 257   $$ = new_token_node (ctx, IPV6_PREFIX_TKN, $1, doc_next(ctx));
 258   XFREE (MTYPE_LEX, $1);
 259 }
 260 | VARIABLE
 261 {
 262   $$ = new_token_node (ctx, VARIABLE_TKN, $1, doc_next(ctx));
 263   XFREE (MTYPE_LEX, $1);
 264 }
 265 | RANGE
 266 {
 267   $$ = new_token_node (ctx, RANGE_TKN, $1, doc_next(ctx));
 268   struct cmd_token *token = $$->data;
 269
 270   // get the numbers out
 271   yylval.string++;
 272   token->min = strtoll (yylval.string, &yylval.string, 10);
 273   strsep (&yylval.string, "-");
 274   token->max = strtoll (yylval.string, &yylval.string, 10);
 275
 276   // validate range
 277   if (token->min > token->max) cmd_yyerror (&@1, ctx, "Invalid range.");
 278
 279   XFREE (MTYPE_LEX, $1);
 280 }
 281 | MAC
 282 {
 283   $$ = new_token_node (ctx, MAC_TKN, $1, doc_next(ctx));
 284   XFREE (MTYPE_LEX, $1);
 285 }
 286 | MAC_PREFIX
 287 {
 288   $$ = new_token_node (ctx, MAC_PREFIX_TKN, $1, doc_next(ctx));
 289   XFREE (MTYPE_LEX, $1);
 290 }
 291
 292 placeholder_token:
 293   placeholder_token_real varname_token
 294 {
 295   struct cmd_token *token = $$->data;
 296   $$ = $1;
 297   cmd_token_varname_set (token, $2);
 298   XFREE (MTYPE_LEX, $2);
 299 };
 300
 301
 302 /* <selector|set> productions */
 303 selector: '<' selector_seq_seq '>' varname_token
 304 {
 305   $$ = $2;
 306   cmd_token_varname_set ($2.end->data, $4);
 307   XFREE (MTYPE_LEX, $4);
 308 };
 309
 310 selector_seq_seq:
 311   selector_seq_seq '|' selector_token_seq
 312 {
 313   $$ = $1;
 314   graph_add_edge ($$.start, $3.start);
 315   graph_add_edge ($3.end, $$.end);
 316 }
 317 | selector_token_seq
 318 {
 319   $$.start = new_token_node (ctx, FORK_TKN, NULL, NULL);
 320   $$.end   = new_token_node (ctx, JOIN_TKN, NULL, NULL);
 321   ((struct cmd_token *)$$.start->data)->forkjoin = $$.end;
 322   ((struct cmd_token *)$$.end->data)->forkjoin = $$.start;
 323
 324   graph_add_edge ($$.start, $1.start);
 325   graph_add_edge ($1.end, $$.end);
 326 }
 327 ;
 328
 329 /* {keyword} productions */
 330 selector: '{' selector_seq_seq '}' varname_token
 331 {
 332   $$ = $2;
 333   graph_add_edge ($$.end, $$.start);
 334   /* there is intentionally no start->end link, for two reasons:
 335    * 1) this allows "at least 1 of" semantics, which are otherwise impossible
 336    * 2) this would add a start->end->start loop in the graph that the current
 337    *    loop-avoidal fails to handle
 338    * just use [{a|b}] if neccessary, that will work perfectly fine, and reason
 339    * #1 is good enough to keep it this way. */
 340
 341   loopcheck(ctx, &$$);
 342   cmd_token_varname_set ($2.end->data, $4);
 343   XFREE (MTYPE_LEX, $4);
 344 };
 345
 346
 347 selector_token:
 348   simple_token
 349 {
 350   $$.start = $$.end = $1;
 351 }
 352 | selector
 353 ;
 354
 355 selector_token_seq:
 356   selector_token_seq selector_token
 357 {
 358   graph_add_edge ($1.end, $2.start);
 359   $$.start = $1.start;
 360   $$.end   = $2.end;
 361 }
 362 | selector_token
 363 ;
 364
 365 /* [option] productions */
 366 selector: '[' selector_seq_seq ']' varname_token
 367 {
 368   $$ = $2;
 369   graph_add_edge ($$.start, $$.end);
 370   cmd_token_varname_set ($2.end->data, $4);
 371   XFREE (MTYPE_LEX, $4);
 372 }
 373 ;
 374
 375 %%
 376
 377 #undef scanner
 378
 379 DEFINE_MTYPE(LIB, LEX, "Lexer token (temporary)")
 380
 381 void
 382 cmd_graph_parse (struct graph *graph, const struct cmd_element *cmd)
 383 {
 384   struct parser_ctx ctx = { .graph = graph, .el = cmd };
 385
 386   // set to 1 to enable parser traces
 387   yydebug = 0;
 388
 389   set_lexer_string (&ctx.scanner, cmd->string);
 390
 391   // parse command into DFA
 392   cmd_yyparse (&ctx);
 393
 394   /* cleanup lexer */
 395   cleanup_lexer (&ctx.scanner);
 396
 397   // cleanup
 398   cleanup (&ctx);
 399 }
 400
 401 /* parser helper functions */
 402
 403 static bool loopcheck_inner(struct graph_node *start, struct graph_node *node,
 404                             struct graph_node *end, size_t depth)
 405 {
 406         size_t i;
 407         bool ret;
 408
 409         /* safety check */
 410         if (depth++ == 64)
 411                 return true;
 412
 413         for (i = 0; i < vector_active(node->to); i++) {
 414                 struct graph_node *next = vector_slot(node->to, i);
 415                 struct cmd_token *tok = next->data;
 416
 417                 if (next == end || next == start)
 418                         return true;
 419                 if (tok->type < SPECIAL_TKN)
 420                         continue;
 421                 ret = loopcheck_inner(start, next, end, depth);
 422                 if (ret)
 423                         return true;
 424         }
 425         return false;
 426 }
 427
 428 static void loopcheck(struct parser_ctx *ctx, struct subgraph *sg)
 429 {
 430         if (loopcheck_inner(sg->start, sg->start, sg->end, 0))
 431                 zlog_err("FATAL: '%s': {} contains an empty path! Use [{...}]",
 432                          ctx->el->string);
 433 }
 434
 435 void
 436 yyerror (CMD_YYLTYPE *loc, struct parser_ctx *ctx, char const *msg)
 437 {
 438   char *tmpstr = strdup(ctx->el->string);
 439   char *line, *eol;
 440   char spacing[256];
 441   int lineno = 0;
 442
 443   zlog_notice ("%s: FATAL parse error: %s", __func__, msg);
 444   zlog_notice ("%s: %d:%d-%d of this command definition:", __func__, loc->first_line, loc->first_column, loc->last_column);
 445
 446   line = tmpstr;
 447   do {
 448     lineno++;
 449     eol = strchr(line, '\n');
 450     if (eol)
 451       *eol++ = '\0';
 452
 453     zlog_notice ("%s: | %s", __func__, line);
 454     if (lineno == loc->first_line && lineno == loc->last_line
 455         && loc->first_column < (int)sizeof(spacing) - 1
 456         && loc->last_column < (int)sizeof(spacing) - 1) {
 457
 458       int len = loc->last_column - loc->first_column;
 459       if (len == 0)
 460         len = 1;
 461
 462       memset(spacing, ' ', loc->first_column - 1);
 463       memset(spacing + loc->first_column - 1, '^', len);
 464       spacing[loc->first_column - 1 + len] = '\0';
 465       zlog_notice ("%s: | %s", __func__, spacing);
 466     }
 467   } while ((line = eol));
 468   free(tmpstr);
 469 }
 470
 471 static void
 472 cleanup (struct parser_ctx *ctx)
 473 {
 474   /* free resources */
 475   free (ctx->docstr_start);
 476
 477   /* clear state pointers */
 478   ctx->currnode = NULL;
 479   ctx->docstr_start = ctx->docstr = NULL;
 480 }
 481
 482 static void
 483 terminate_graph (CMD_YYLTYPE *locp, struct parser_ctx *ctx,
 484                  struct graph_node *finalnode)
 485 {
 486   // end of graph should look like this
 487   // * -> finalnode -> END_TKN -> cmd_element
 488   const struct cmd_element *element = ctx->el;
 489   struct graph_node *end_token_node =
 490     new_token_node (ctx, END_TKN, CMD_CR_TEXT, "");
 491   struct graph_node *end_element_node =
 492     graph_new_node (ctx->graph, (void *)element, NULL);
 493
 494   if (ctx->docstr && strlen (ctx->docstr) > 1) {
 495     zlog_debug ("Excessive docstring while parsing '%s'", ctx->el->string);
 496     zlog_debug ("----------");
 497     while (ctx->docstr && ctx->docstr[1] != '\0')
 498       zlog_debug ("%s", strsep(&ctx->docstr, "\n"));
 499     zlog_debug ("----------\n");
 500   }
 501
 502   graph_add_edge (finalnode, end_token_node);
 503   graph_add_edge (end_token_node, end_element_node);
 504 }
 505
 506 static const char *
 507 doc_next (struct parser_ctx *ctx)
 508 {
 509   const char *piece = ctx->docstr ? strsep (&ctx->docstr, "\n") : "";
 510   if (*piece == 0x03)
 511   {
 512     zlog_debug ("Ran out of docstring while parsing '%s'", ctx->el->string);
 513     piece = "";
 514   }
 515
 516   return piece;
 517 }
 518
 519 static struct graph_node *
 520 new_token_node (struct parser_ctx *ctx, enum cmd_token_type type,
 521                 const char *text, const char *doc)
 522 {
 523   struct cmd_token *token = cmd_token_new (type, ctx->el->attr, text, doc);
 524   return graph_new_node (ctx->graph, token, (void (*)(void *)) &cmd_token_del);
 525 }