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_command_r (struct graph_node *, vector, unsigned int);

static int
score_precedence (enum graph_node_type);

static enum match_type
min_match_level(enum node_type);

static struct graph_node *
copy_node (struct graph_node *);

static void
delete_nodelist (void *);

static struct graph_node *
disambiguate (struct graph_node *, struct graph_node *, char *);

/* token matcher prototypes */
static enum match_type
match_token (struct graph_node *, char *);

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 *);

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

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

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

/* matching functions */
static enum matcher_rv matcher_result_value;

enum matcher_rv
match_command (struct graph_node *start,
               const char *line,
               struct list **argvv,
               struct cmd_element **el)
{
  matcher_result_value = MATCHER_NO_MATCH;
  // parse command
  vector vline = cmd_make_strvec (line);

  for (unsigned int i = 0; i < vector_active(start->children); i++)
  {
    // call recursive matcher on each starting child
    *argvv = match_command_r(vector_slot(start->children, i), vline, 0);
    if (*argvv) break;
  }

  if (*argvv) {
    struct listnode *ln;
    struct graph_node *gn;
    for (ALL_LIST_ELEMENTS_RO(*argvv,ln,gn))
      if (gn->type == END_GN) {
        *el = gn->element;
        break;
      }
    assert(el);
  }

  return matcher_result_value;
}

/**
 * Builds an argument list given a DFA and a matching 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 the input is ambiguous for the passed cmd_element 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_command_r (struct graph_node *start, vector vline, unsigned int n)
{
  // get the minimum match level that can count as a full match
  enum match_type minmatch = min_match_level(start->type);

  // get the current operating token
  char *token = vector_slot(vline, n);

  // if we don't match this node, die
  if (match_token(start, token) < minmatch)
    return NULL;

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

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

  // determine the best match
  int ambiguous = 0;
  struct list *bestmatch = NULL;
  for (ALL_LIST_ELEMENTS_RO(next,ln,gn))
  {
    // if we've matched all input we're looking for END_GN
    if (n+1 == vector_active (vline)) {
      if (gn->type == END_GN) {
        bestmatch = list_new();
        listnode_add(bestmatch, copy_node(gn));
        bestmatch->del = &delete_nodelist;
        break;
      }
      else continue;
    }

    // else recurse on candidate child node
    struct list *result = match_command_r (gn, vline, n+1);

    // save the best match, subtle logic at play here
    if (result) {
      if (bestmatch) {
        struct list *to_delete = result;
        struct graph_node *new = listgetdata(result->head),
                          *old = listgetdata(bestmatch->head);
        char *nextoken = vector_slot (vline, n+1);
        struct graph_node *best = disambiguate(new, old, nextoken);
        ambiguous = !best || (ambiguous && best == old);
        if (best == new) {
          to_delete = bestmatch;
          bestmatch = result;
        }
        list_delete (to_delete);
      }
      else
        bestmatch = result;
    }
  }

  if (bestmatch) {
    if (ambiguous) {
      list_delete(bestmatch);
      bestmatch = NULL;
      matcher_result_value = MATCHER_AMBIGUOUS;
    }
    else {
      // copy current node, set arg and prepend to bestmatch
      struct graph_node *curr = copy_node(start);
      curr->arg = XSTRDUP(MTYPE_CMD_TOKENS, token);
      list_add_node_prev (bestmatch, bestmatch->head, curr);
      matcher_result_value = MATCHER_OK;
    }
  }
  else {
    if (n+1 == vector_active(vline) && matcher_result_value == MATCHER_NO_MATCH)
      matcher_result_value = MATCHER_INCOMPLETE;
  }

  // cleanup
  list_delete (next);

  return bestmatch;
}

struct list *
match_command_complete (struct graph_node *start, const char *line)
{
  // 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
                 *next = list_new(); // possible next hops after 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);

    for (ALL_LIST_ELEMENTS_RO(current,node,gn))
    {
      switch (match_token(gn, token)) {
        case partly_match:
          if (idx == vector_active(vline) - 1) {
            listnode_add(next, gn);
            break;
          }
        case exact_match:
          add_nexthops(next, gn);
          break;
        default:
          break;
      }
    }
  }

  /* 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
   * next     = set of all nodes reachable from all nodes in `matched`
   */

  matcher_result_value =
     idx + 1 == vector_active(vline) && next->count ?
     MATCHER_OK :
     MATCHER_NO_MATCH;

  list_free (current);
  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;
}

/**
 * Determines the node types for which a partial match may count as a full
 * match. Enables command abbrevations.
 */
static enum match_type
min_match_level(enum node_type type)
{
  switch (type) {
    case WORD_GN:
      return partly_match;
    default:
      return exact_match;
  }
}

/* Precedence score used to disambiguate matches. */
static int
score_precedence (enum graph_node_type type)
{
  switch (type)
  {
    // some of these are mutually exclusive, so they share
    // the same precedence value
    case IPV4_GN:
    case IPV4_PREFIX_GN:
    case IPV6_GN:
    case IPV6_PREFIX_GN:
    case NUMBER_GN:
      return 1;
    case RANGE_GN:
      return 2;
    case WORD_GN:
      return 3;
    case VARIABLE_GN:
      return 4;
    default:
      return 10;
  }
}

/* Disambiguation logic to pick the best of two possible matches */
static struct graph_node *
disambiguate (struct graph_node *first, struct graph_node *second, char *token)
{
  // if the types are different, simply go off of type precedence
  if (first->type != second->type) {
    int firstprec = score_precedence(first->type);
    int secndprec = score_precedence(second->type);
    if (firstprec != secndprec)
      return firstprec < secndprec ? first : second;
    else
      return NULL;
  }

  // if they're the same, return the more exact match
  enum match_type fmtype = match_token (first, token);
  enum match_type smtype = match_token (second, token);
  if (fmtype != smtype)
    return fmtype > smtype ? first : second;

  return NULL;
}

static struct graph_node *
copy_node (struct graph_node *node)
{
  struct graph_node *new = new_node(node->type);
  new->children = NULL;
  new->is_start = node->is_start;
  new->end      = NULL;
  new->text     = node->text ? XSTRDUP(MTYPE_CMD_TOKENS, node->text) : NULL;
  new->value    = node->value;
  new->min      = node->min;
  new->max      = node->max;
  new->element  = node->element ? copy_cmd_element(node->element) : NULL;
  new->arg      = node->arg ? XSTRDUP(MTYPE_CMD_TOKENS, node->arg) : NULL;
  new->refs     = 0;
  return new;
}

/* Linked list data deletion callback */
static void
delete_nodelist (void *node)
{
  free_node ((struct graph_node *) node);
}


/* token level matching functions */

static enum match_type
match_token (struct graph_node *node, char *token)
{
  switch (node->type) {
    case WORD_GN:
      return match_word (node, 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)
{
  const char *sp;
  int dots = 0, nums = 0;
  char buf[4];

  if (str == NULL)
    return partly_match;

  for (;;)
    {
      memset (buf, 0, sizeof (buf));
      sp = str;
      while (*str != '\0')
        {
          if (*str == '.')
            {
              if (dots >= 3)
                return no_match;

              if (*(str + 1) == '.')
                return no_match;

              if (*(str + 1) == '\0')
                return partly_match;

              dots++;
              break;
            }
          if (!isdigit ((int) *str))
            return no_match;

          str++;
        }

      if (str - sp > 3)
        return no_match;

      strncpy (buf, sp, str - sp);
      if (atoi (buf) > 255)
        return no_match;

      nums++;

      if (*str == '\0')
        break;

      str++;
    }

  if (nums < 4)
    return partly_match;

  return exact_match;
}

static enum match_type
match_ipv4_prefix (const char *str)
{
  const char *sp;
  int dots = 0;
  char buf[4];

  if (str == NULL)
    return partly_match;

  for (;;)
    {
      memset (buf, 0, sizeof (buf));
      sp = str;
      while (*str != '\0' && *str != '/')
        {
          if (*str == '.')
            {
              if (dots == 3)
                return no_match;

              if (*(str + 1) == '.' || *(str + 1) == '/')
                return no_match;

              if (*(str + 1) == '\0')
                return partly_match;

              dots++;
              break;
            }

          if (!isdigit ((int) *str))
            return no_match;

          str++;
        }

      if (str - sp > 3)
        return no_match;

      strncpy (buf, sp, str - sp);
      if (atoi (buf) > 255)
        return no_match;

      if (dots == 3)
        {
          if (*str == '/')
            {
              if (*(str + 1) == '\0')
                return partly_match;

              str++;
              break;
            }
          else if (*str == '\0')
            return partly_match;
        }

      if (*str == '\0')
        return partly_match;

      str++;
    }

  sp = str;
  while (*str != '\0')
    {
      if (!isdigit ((int) *str))
        return no_match;

      str++;
    }

  if (atoi (sp) > 32)
    return no_match;

  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 = strtoimax (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 int val;

  if (str == NULL)
    return 1;

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

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

static enum match_type
match_word(struct graph_node *wordnode, const char *word)
{
  // if the passed token is null or 0 length, partly match
  if (!word || !strlen(word))
    return partly_match;

  // if the passed token is strictly a prefix of the full word, partly match
  if (strlen(word) < strlen(wordnode->text))
    return !strncmp(wordnode->text, word, strlen(word)) ? partly_match : no_match;

  // if they are the same length and exactly equal, exact match
  else if (strlen(word) == strlen(wordnode->text))
    return !strncmp(wordnode->text, word, strlen(word)) ? exact_match : no_match;

  return no_match;
}

static enum match_type
match_number(struct graph_node *numnode, const char *word)
{
  if (!strcmp("\0", word)) return no_match;
  char *endptr;
  int num = strtoimax(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) ?
     exact_match : no_match;
}