frr/lib/command_match.c

#include "command_match.h"
#include "command_parse.h"
#include <zebra.h>
#include "memory.h"

/* matcher helper prototypes */
static int
add_nexthops(struct list *, struct graph_node *);

static struct list *
match_build_argv_r (struct graph_node *, vector, unsigned int);

static int
score_precedence (struct graph_node *);

/* token matcher prototypes */
static enum match_type
match_ipv4 (const char *);

static enum match_type
match_ipv4_prefix (const char *);

static enum match_type
match_ipv6 (const char *);

static enum match_type
match_ipv6_prefix (const char *);

static enum match_type
match_range (struct graph_node *, const char *str);

static enum match_type
match_word (struct graph_node *, enum filter_type, const char *);

static enum match_type
match_number (struct graph_node *, const char *);

static enum match_type
match_variable (struct graph_node *, const char *);

static enum match_type
match_token (struct graph_node *, char *, enum filter_type);

/* matching functions */

struct cmd_element *
match_command (struct graph_node *start, const char *line, enum filter_type filter)
{
  // get all possible completions
  struct list *completions = match_command_complete (start, line, filter);

  // one of them should be END_GN if this command matches
  struct graph_node *gn;
  struct listnode *node;
  for (ALL_LIST_ELEMENTS_RO(completions,node,gn))
  {
    if (gn->type == END_GN)
      break;
    gn = NULL;
  }
  return gn ? gn->element : NULL;
}

struct list *
match_command_complete (struct graph_node *start, const char *line, enum filter_type filter)
{
  // vectorize command line
  vector vline = cmd_make_strvec (line);

  // pointer to next input token to match
  char *token;

  struct list *current  = list_new(), // current nodes to match input token against
              *matched  = list_new(), // current nodes that match the input token
              *next     = list_new(); // possible next hops to current input token

  // pointers used for iterating lists
  struct graph_node *gn;
  struct listnode *node;

  // add all children of start node to list
  add_nexthops(next, start);

  unsigned int idx;
  for (idx = 0; idx < vector_active(vline) && next->count > 0; idx++)
  {
    list_free (current);
    current = next;
    next = list_new();

    token = vector_slot(vline, idx);

    list_delete_all_node(matched);

    for (ALL_LIST_ELEMENTS_RO(current,node,gn))
    {
      if (match_token(gn, token, filter) == exact_match) {
        listnode_add(matched, gn);
        add_nexthops(next, gn);
      }
    }
  }

  /* Variable summary
   * -----------------------------------------------------------------
   * token    = last input token processed
   * idx      = index in `command` of last token processed
   * current  = set of all transitions from the previous input token
   * matched  = set of all nodes reachable with current input
   * next     = set of all nodes reachable from all nodes in `matched`
   */
  list_free (current);
  list_free (matched);

  cmd_free_strvec(vline);

  return next;
}

/**
 * Adds all children that are reachable by one parser hop
 * to the given list. NUL_GN, SELECTOR_GN, and OPTION_GN
 * nodes are treated as transparent.
 *
 * @param[out] l the list to add the children to
 * @param[in] node the node to get the children of
 * @return the number of children added to the list
 */
static int
add_nexthops(struct list *l, struct graph_node *node)
{
  int added = 0;
  struct graph_node *child;
  for (unsigned int i = 0; i < vector_active(node->children); i++)
  {
    child = vector_slot(node->children, i);
    switch (child->type) {
      case OPTION_GN:
      case SELECTOR_GN:
      case NUL_GN:
        added += add_nexthops(l, child);
        break;
      default:
        listnode_add(l, child);
        added++;
    }
  }
  return added;
}

struct list *
match_build_argv (const char *line, struct cmd_element *element)
{
  struct list *argv = NULL;

  // parse command
  struct graph_node *start = new_node(NUL_GN);
  parse_command_format(start, element);

  vector vline = cmd_make_strvec (line);

  for (unsigned int i = 0; i < vector_active(start->children); i++)
  {
    // call recursive builder on each starting child
    argv = match_build_argv_r (vector_slot(start->children, i), vline, 0);
    // if any of them succeed, return their argv
    // since all command DFA's must begin with a word and these are deduplicated,
    // no need to check precedence
    if (argv) break;
  }

  return argv;
}

/**
 * Builds an argument list given a DFA and a matching input line.
 * This function should be passed the start node of the DFA, a matching
 * input line, and the index of the first input token in the input line.
 *
 * First the function determines if the node it is passed matches the
 * first token of input. If it does not, it returns NULL. If it does
 * match, then it saves the input token as the head of an argument list.
 *
 * The next step is to see if there is further input in the input line.
 * If there is not, the current node's children are searched to see if
 * any of them are leaves (type END_GN). If this is the case, then the
 * bottom of the recursion stack has been reached, and the argument list
 * (with one node) is returned. If it is not the case, NULL is returned,
 * indicating that there is no match for the input along this path.
 *
 * If there is further input, then the function recurses on each of the
 * current node's children, passing them the input line minus the token
 * that was just matched. For each child, the return value of the recursive
 * call is inspected. If it is null, then there is no match for the input along
 * the subgraph headed by that child. If it is not null, then there is at least
 * one input match in that subgraph (more on this in a moment).
 *
 * If a recursive call on a child returns a non-null value, then it has matched
 * the input given it on the subgraph that starts with that child. However, due
 * to the flexibility of the grammar, it is sometimes the case that two or more
 * child graphs match the same input (two or more of the recursive calls have
 * non-NULL return values). This is not a valid state, since only one
 * true match is possible. In order to resolve this conflict, the function
 * keeps a reference to the child node that most specifically matches the
 * input. This is done by assigning each node type a precedence. If a child is
 * found to match the remaining input, then the precedence values of the
 * current best-matching child and this new match are compared. The node with
 * higher precedence is kept, and the other match is discarded. Due to the
 * recursive nature of this function, it is only necessary to compare the
 * precedence of immediate children, since all subsequent children will already
 * have been disambiguated in this way.
 *
 * In the event that two children are found to match with the same precedence,
 * then this command is totally ambiguous (how did you even match it in the first
 * place?) and NULL is returned.
 *
 * The ultimate return value is an ordered linked list of nodes that comprise
 * the best match for the command, each with their `arg` fields pointing to the
 * matching token string.
 *
 * @param[out] start the start node.
 * @param[in] vline the vectorized input line.
 * @param[in] n the index of the first input token. Should be 0 for external
 * callers.
 */
static struct list *
match_build_argv_r (struct graph_node *start, vector vline, unsigned int n)
{
  // if we don't match this node, die
  if (match_token(start, vector_slot(vline, n), FILTER_STRICT) != exact_match)
    return NULL;

  // arg list for this subgraph
  struct list *argv = list_new();

  // pointers for iterating linklist
  struct graph_node *gn;
  struct listnode   *ln;

  // append current arg
  listnode_add(argv, start);

  // get all possible nexthops
  struct list *next = list_new();
  add_nexthops(next, start);

  // if we're at the end of input, need END_GN or no match
  if (n+1 == vector_active (vline)) {
    for (ALL_LIST_ELEMENTS_RO(next,ln,gn)) {
      if (gn->type == END_GN) {
        list_delete (next);
        start->arg = XSTRDUP(MTYPE_CMD_TOKENS, vector_slot(vline, n));
        if (start->type == VARIABLE_GN)
          fprintf(stderr, "Setting variable %s->arg with text %s\n", start->text, start->arg);
        return argv;
      }
    }
    list_free (next);
    return NULL;
  }

  // otherwise recurse on all nexthops
  struct list *bestmatch = NULL;
  for (ALL_LIST_ELEMENTS_RO(next,ln,gn))
    {
      if (gn->type == END_GN) // skip END_GN since we aren't at end of input
        continue;

      // get the result of the next node
      for (unsigned int i = 0; i < n; i++) fprintf(stderr, "\t");
      fprintf(stderr, "Recursing on node %s for token %s\n", gn->text, (char*) vector_slot(vline, n+1));
      struct list *result = match_build_argv_r (gn, vline, n+1);

      // compare to our current best match, and save if it's better
      if (result) {
        if (bestmatch) {
          int currprec = score_precedence (listgetdata(listhead(bestmatch)));
          int rsltprec = score_precedence (gn);
          if (currprec < rsltprec)
            list_delete (result);
          if (currprec > rsltprec) {
            for (unsigned int i = 0; i < n; i++) fprintf(stderr, "\t");
            fprintf(stderr, ">> Overwriting bestmatch with: %s\n", gn->text);
            list_delete (bestmatch);
            bestmatch = result;
          }
          if (currprec == rsltprec) {
            fprintf(stderr, ">> Ambiguous match. Abort.\n");
            list_delete (bestmatch);
            list_delete (result);
            list_delete (argv);
            return NULL;
          }
        }
        else {
          bestmatch = result;
          for (unsigned int i = 0; i < n; i++) fprintf(stderr, "\t");
          fprintf(stderr, ">> Setting bestmatch with: %s\n", gn->text);
        }
      }
    }

  if (bestmatch) {
    list_add_list(argv, bestmatch);
    list_delete (bestmatch);
    start->arg = XSTRDUP(MTYPE_CMD_TOKENS, vector_slot(vline, n));
    if (start->type == VARIABLE_GN)
      fprintf(stderr, "Setting variable %s->arg with text %s\n", start->text, start->arg);
    return argv;
  }
  else {
    list_delete (argv);
    return NULL;
  }
}

/* matching utility functions */

static int
score_precedence (struct graph_node *node)
{
  switch (node->type)
  {
    // these should be mutually exclusive
    case IPV4_GN:
    case IPV4_PREFIX_GN:
    case IPV6_GN:
    case IPV6_PREFIX_GN:
    case RANGE_GN:
    case NUMBER_GN:
      return 1;
    case WORD_GN:
      return 2;
    case VARIABLE_GN:
      return 3;
    default:
      return 10;
  }
}

static enum match_type
match_token (struct graph_node *node, char *token, enum filter_type filter)
{
  switch (node->type) {
    case WORD_GN:
      return match_word (node, filter, token);
    case IPV4_GN:
      return match_ipv4 (token);
    case IPV4_PREFIX_GN:
      return match_ipv4_prefix (token);
    case IPV6_GN:
      return match_ipv6 (token);
    case IPV6_PREFIX_GN:
      return match_ipv6_prefix (token);
    case RANGE_GN:
      return match_range (node, token);
    case NUMBER_GN:
      return match_number (node, token);
    case VARIABLE_GN:
      return match_variable (node, token);
    case END_GN:
    default:
      return no_match;
  }
}

#define IPV4_ADDR_STR   "0123456789."
#define IPV4_PREFIX_STR "0123456789./"

static enum match_type
match_ipv4 (const char *str)
{
  struct sockaddr_in sin_dummy;

  if (str == NULL)
    return partly_match;

  if (strspn (str, IPV4_ADDR_STR) != strlen (str))
    return no_match;

  if (inet_pton(AF_INET, str, &sin_dummy.sin_addr) != 1)
    return no_match;

  return exact_match;
}

static enum match_type
match_ipv4_prefix (const char *str)
{
  struct sockaddr_in sin_dummy;
  const char *delim = "/\0";
  char *dupe, *prefix, *mask, *context, *endptr;
  int nmask = -1;

  if (str == NULL)
    return partly_match;

  if (strspn (str, IPV4_PREFIX_STR) != strlen (str))
    return no_match;

  /* tokenize to address + mask */
  dupe = XMALLOC(MTYPE_TMP, strlen(str)+1);
  strncpy(dupe, str, strlen(str)+1);
  prefix = strtok_r(dupe, delim, &context);
  mask   = strtok_r(NULL, delim, &context);

  if (!mask)
    return partly_match;

  /* validate prefix */
  if (inet_pton(AF_INET, prefix, &sin_dummy.sin_addr) != 1)
    return no_match;

  /* validate mask */
  nmask = strtol (mask, &endptr, 10);
  if (*endptr != '\0' || nmask < 0 || nmask > 32)
    return no_match;

  XFREE(MTYPE_TMP, dupe);

  return exact_match;
}

#ifdef HAVE_IPV6
#define IPV6_ADDR_STR   "0123456789abcdefABCDEF:."
#define IPV6_PREFIX_STR "0123456789abcdefABCDEF:./"

static enum match_type
match_ipv6 (const char *str)
{
  struct sockaddr_in6 sin6_dummy;
  int ret;

  if (str == NULL)
    return partly_match;

  if (strspn (str, IPV6_ADDR_STR) != strlen (str))
    return no_match;

  ret = inet_pton(AF_INET6, str, &sin6_dummy.sin6_addr);

  if (ret == 1)
    return exact_match;

  return no_match;
}

static enum match_type
match_ipv6_prefix (const char *str)
{
  struct sockaddr_in6 sin6_dummy;
  const char *delim = "/\0";
  char *dupe, *prefix, *mask, *context, *endptr;
  int nmask = -1;

  if (str == NULL)
    return partly_match;

  if (strspn (str, IPV6_PREFIX_STR) != strlen (str))
    return no_match;

  /* tokenize to address + mask */
  dupe = XMALLOC(MTYPE_TMP, strlen(str)+1);
  strncpy(dupe, str, strlen(str)+1);
  prefix = strtok_r(dupe, delim, &context);
  mask   = strtok_r(NULL, delim, &context);

  if (!mask)
    return partly_match;

  /* validate prefix */
  if (inet_pton(AF_INET6, prefix, &sin6_dummy.sin6_addr) != 1)
    return no_match;

  /* validate mask */
  nmask = strtol (mask, &endptr, 10);
  if (*endptr != '\0' || nmask < 0 || nmask > 128)
    return no_match;

  XFREE(MTYPE_TMP, dupe);

  return exact_match;
}
#endif

static enum match_type
match_range (struct graph_node *rangenode, const char *str)
{
  char *endptr = NULL;
  signed long val;

  if (str == NULL)
    return 1;

  val = strtoll (str, &endptr, 10);
  if (*endptr != '\0')
    return 0;
  val = llabs(val);

  if (val < rangenode->min || val > rangenode->max)
    return no_match;
  else
    return exact_match;
}

static enum match_type
match_word(struct graph_node *wordnode,
           enum filter_type filter,
           const char *word)
{
  if (filter == FILTER_RELAXED)
  {
    if (!word || !strlen(word))
      return partly_match;
    else if (!strncmp(wordnode->text, word, strlen(word)))
      return !strcmp(wordnode->text, word) ? exact_match : partly_match;
    else
      return no_match;
  }
  else
  {
     if (!word)
       return no_match;
     else
       return !strcmp(wordnode->text, word) ? exact_match : no_match;
  }
}

static enum match_type
match_number(struct graph_node *numnode, const char *word)
{
  if (!strcmp("\0", word)) return no_match;
  char *endptr;
  long num = strtol(word, &endptr, 10);
  if (endptr != '\0') return no_match;
  return num == numnode->value ? exact_match : no_match;
}

#define VARIABLE_ALPHABET "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890"

static enum match_type
match_variable(struct graph_node *varnode, const char *word)
{
  return strlen(word) == strspn(word, VARIABLE_ALPHABET) && isalpha(word[0]) ?
     exact_match : no_match;
}