Merge pull request #2053 from LabNConsulting/working/master/bvl-bug-degenerate-no...

[mirror_frr.git] / lib / command_match.c

/*
 * Input matching routines for CLI backend.
 *
 * --
 * Copyright (C) 2016 Cumulus Networks, Inc.
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * GNU Zebra is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>

#include "command_match.h"
#include "memory.h"

DEFINE_MTYPE_STATIC(LIB, CMD_MATCHSTACK, "Command Match Stack")

#ifdef TRACE_MATCHER
#define TM 1
#else
#define TM 0
#endif

#define trace_matcher(...)                                                     \
        do {                                                                   \
                if (TM)                                                        \
                        fprintf(stderr, __VA_ARGS__);                          \
        } while (0);

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

static enum matcher_rv command_match_r(struct graph_node *, vector,
                                       unsigned int, struct graph_node **,
                                       struct list **);

static int score_precedence(enum cmd_token_type);

static enum match_type min_match_level(enum cmd_token_type);

static void del_arglist(struct list *);

static struct cmd_token *disambiguate_tokens(struct cmd_token *,
                                             struct cmd_token *, char *);

static struct list *disambiguate(struct list *, struct list *, vector,
                                 unsigned int);

int compare_completions(const void *, const void *);

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

static enum match_type match_ipv4(const char *);

static enum match_type match_ipv4_prefix(const char *);

static enum match_type match_ipv6_prefix(const char *, bool);

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

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

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

static enum match_type match_mac(const char *, bool);

enum matcher_rv command_match(struct graph *cmdgraph, vector vline,
                              struct list **argv, const struct cmd_element **el)
{
        struct graph_node *stack[CMD_ARGC_MAX];
        enum matcher_rv status;
        *argv = NULL;

        // prepend a dummy token to match that pesky start node
        vector vvline = vector_init(vline->alloced + 1);
        vector_set_index(vvline, 0, (void *)XSTRDUP(MTYPE_TMP, "dummy"));
        memcpy(vvline->index + 1, vline->index,
               sizeof(void *) * vline->alloced);
        vvline->active = vline->active + 1;

        struct graph_node *start = vector_slot(cmdgraph->nodes, 0);
        status = command_match_r(start, vvline, 0, stack, argv);
        if (status == MATCHER_OK) { // successful match
                struct listnode *head = listhead(*argv);
                struct listnode *tail = listtail(*argv);

                assert(head);
                assert(tail);

                // delete dummy start node
                cmd_token_del((struct cmd_token *)head->data);
                list_delete_node(*argv, head);

                // get cmd_element out of list tail
                *el = listgetdata(tail);
                list_delete_node(*argv, tail);

                // now argv is an ordered list of cmd_token matching the user
                // input, with each cmd_token->arg holding the corresponding
                // input
                assert(*el);
        } else if (*argv) {
                del_arglist(*argv);
                *argv = NULL;
        }

        if (!*el) {
                trace_matcher("No match\n");
        } else {
                trace_matcher("Matched command\n->string %s\n->desc %s\n",
                              (*el)->string, (*el)->doc);
        }

        // free the leader token we alloc'd
        XFREE(MTYPE_TMP, vector_slot(vvline, 0));
        // free vector
        vector_free(vvline);

        return status;
}

/**
 * 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 (MATCHER_NO_MATCH). 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_TKN). If this is the case, then the bottom of the
 * recursion stack has been reached, the leaf is pushed onto the argument list,
 * the current node is pushed, and the resulting argument list is
 * returned (MATCHER_OK). If it is not the case, NULL is returned, indicating
 * that there is no match for the input along this path (MATCHER_INCOMPLETE).
 *
 * 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.
 *
 * @param[in] start the start node.
 * @param[in] vline the vectorized input line.
 * @param[in] n the index of the first input token.
 * @return A linked list of n elements. The first n-1 elements are pointers to
 * struct cmd_token and represent the sequence of tokens matched by the input.
 * The ->arg field of each token points to a copy of the input matched on it.
 * The final nth element is a pointer to struct cmd_element, which is the
 * command that was matched.
 *
 * If no match was found, the return value is NULL.
 */
static enum matcher_rv command_match_r(struct graph_node *start, vector vline,
                                       unsigned int n,
                                       struct graph_node **stack,
                                       struct list **currbest)
{
        assert(n < vector_active(vline));

        enum matcher_rv status = MATCHER_NO_MATCH;

        // get the minimum match level that can count as a full match
        struct cmd_token *token = start->data;
        enum match_type minmatch = min_match_level(token->type);

        /* check history/stack of tokens
         * this disallows matching the same one more than once if there is a
         * circle in the graph (used for keyword arguments) */
        if (n == CMD_ARGC_MAX)
                return MATCHER_NO_MATCH;
        if (!token->allowrepeat)
                for (size_t s = 0; s < n; s++)
                        if (stack[s] == start)
                                return MATCHER_NO_MATCH;

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

#ifdef TRACE_MATCHER
        fprintf(stdout, "\"%-20s\" matches \"%-30s\" ? ", input_token,
                token->text);
        enum match_type mt = match_token(token, input_token);
        fprintf(stdout, "type: %d ", token->type);
        fprintf(stdout, "min: %d - ", minmatch);
        switch (mt) {
        case trivial_match:
                fprintf(stdout, "trivial_match ");
                break;
        case no_match:
                fprintf(stdout, "no_match ");
                break;
        case partly_match:
                fprintf(stdout, "partly_match ");
                break;
        case exact_match:
                fprintf(stdout, "exact_match ");
                break;
        }
        if (mt >= minmatch)
                fprintf(stdout, " MATCH");
        fprintf(stdout, "\n");
#endif

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

        stack[n] = start;

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

        // get all possible nexthops
        struct list *next = list_new();
        add_nexthops(next, start, NULL, 0);

        // determine the best match
        for (ALL_LIST_ELEMENTS_RO(next, ln, gn)) {
                // if we've matched all input we're looking for END_TKN
                if (n + 1 == vector_active(vline)) {
                        struct cmd_token *tok = gn->data;
                        if (tok->type == END_TKN) {
                                // if more than one END_TKN in the follow set
                                if (*currbest) {
                                        status = MATCHER_AMBIGUOUS;
                                        break;
                                } else {
                                        status = MATCHER_OK;
                                }
                                *currbest = list_new();
                                // node should have one child node with the
                                // element
                                struct graph_node *leaf =
                                        vector_slot(gn->to, 0);
                                // last node in the list will hold the
                                // cmd_element; this is important because
                                // list_delete() expects that all nodes have
                                // the same data type, so when deleting this
                                // list the last node must be manually deleted
                                struct cmd_element *el = leaf->data;
                                listnode_add(*currbest, el);
                                (*currbest)->del =
                                        (void (*)(void *)) & cmd_token_del;
                                // do not break immediately; continue walking
                                // through the follow set to ensure that there
                                // is exactly one END_TKN
                        }
                        continue;
                }

                // else recurse on candidate child node
                struct list *result = NULL;
                enum matcher_rv rstat =
                        command_match_r(gn, vline, n + 1, stack, &result);

                // save the best match
                if (result && *currbest) {
                        // pick the best of two matches
                        struct list *newbest =
                                disambiguate(*currbest, result, vline, n + 1);

                        // current best and result are ambiguous
                        if (!newbest)
                                status = MATCHER_AMBIGUOUS;
                        // current best is still the best, but ambiguous
                        else if (newbest == *currbest
                                 && status == MATCHER_AMBIGUOUS)
                                status = MATCHER_AMBIGUOUS;
                        // result is better, but also ambiguous
                        else if (newbest == result
                                 && rstat == MATCHER_AMBIGUOUS)
                                status = MATCHER_AMBIGUOUS;
                        // one or the other is superior and not ambiguous
                        else
                                status = MATCHER_OK;

                        // delete the unnecessary result
                        struct list *todelete =
                                ((newbest && newbest == result) ? *currbest
                                                                : result);
                        del_arglist(todelete);

                        *currbest = newbest ? newbest : *currbest;
                } else if (result) {
                        status = rstat;
                        *currbest = result;
                } else if (!*currbest) {
                        status = MAX(rstat, status);
                }
        }
        if (*currbest) {
                // copy token, set arg and prepend to currbest
                struct cmd_token *token = start->data;
                struct cmd_token *copy = cmd_token_dup(token);
                copy->arg = XSTRDUP(MTYPE_CMD_ARG, input_token);
                listnode_add_before(*currbest, (*currbest)->head, copy);
        } else if (n + 1 == vector_active(vline) && status == MATCHER_NO_MATCH)
                status = MATCHER_INCOMPLETE;

        // cleanup
        list_delete_and_null(&next);

        return status;
}

static void stack_del(void *val)
{
        XFREE(MTYPE_CMD_MATCHSTACK, val);
}

enum matcher_rv command_complete(struct graph *graph, vector vline,
                                 struct list **completions)
{
        // pointer to next input token to match
        char *input_token;

        struct list *
                current =
                       list_new(), // current nodes to match input token against
                *next = list_new(); // possible next hops after current input
                                    // token
        current->del = next->del = stack_del;

        // pointers used for iterating lists
        struct graph_node **gstack, **newstack;
        struct listnode *node;

        // add all children of start node to list
        struct graph_node *start = vector_slot(graph->nodes, 0);
        add_nexthops(next, start, &start, 0);

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

                input_token = vector_slot(vline, idx);

                int exact_match_exists = 0;
                for (ALL_LIST_ELEMENTS_RO(current, node, gstack))
                        if (!exact_match_exists)
                                exact_match_exists =
                                        (match_token(gstack[0]->data,
                                                     input_token)
                                         == exact_match);
                        else
                                break;

                for (ALL_LIST_ELEMENTS_RO(current, node, gstack)) {
                        struct cmd_token *token = gstack[0]->data;

                        if (token->attr == CMD_ATTR_HIDDEN
                            || token->attr == CMD_ATTR_DEPRECATED)
                                continue;

                        enum match_type minmatch = min_match_level(token->type);
                        trace_matcher("\"%s\" matches \"%s\" (%d) ? ",
                                      input_token, token->text, token->type);

                        unsigned int last_token =
                                (vector_active(vline) - 1 == idx);
                        enum match_type matchtype =
                                match_token(token, input_token);
                        switch (matchtype) {
                        // occurs when last token is whitespace
                        case trivial_match:
                                trace_matcher("trivial_match\n");
                                assert(last_token);
                                newstack = XMALLOC(MTYPE_CMD_MATCHSTACK,
                                                   sizeof(struct graph_node *));
                                /* we're not recursing here, just the first
                                 * element is OK */
                                newstack[0] = gstack[0];
                                listnode_add(next, newstack);
                                break;
                        case partly_match:
                                trace_matcher("trivial_match\n");
                                if (exact_match_exists && !last_token)
                                        break;
                        /* fallthru */
                        case exact_match:
                                trace_matcher("exact_match\n");
                                if (last_token) {
                                        newstack = XMALLOC(
                                                MTYPE_CMD_MATCHSTACK,
                                                sizeof(struct graph_node *));
                                        /* same as above, not recursing on this
                                         */
                                        newstack[0] = gstack[0];
                                        listnode_add(next, newstack);
                                } else if (matchtype >= minmatch)
                                        add_nexthops(next, gstack[0], gstack,
                                                     idx + 1);
                                break;
                        default:
                                trace_matcher("no_match\n");
                                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`
         */

        enum matcher_rv mrv = idx == vector_active(vline) && next->count
                                      ? MATCHER_OK
                                      : MATCHER_NO_MATCH;

        *completions = NULL;
        if (!MATCHER_ERROR(mrv)) {
                // extract cmd_token into list
                *completions = list_new();
                for (ALL_LIST_ELEMENTS_RO(next, node, gstack)) {
                        listnode_add(*completions, gstack[0]->data);
                }
        }

        list_delete_and_null(&current);
        list_delete_and_null(&next);

        return mrv;
}

/**
 * Adds all children that are reachable by one parser hop to the given list.
 * special tokens except END_TKN are treated as transparent.
 *
 * @param[in] list to add the nexthops to
 * @param[in] node to start calculating nexthops from
 * @param[in] stack listing previously visited nodes, if non-NULL.
 * @param[in] stackpos how many valid entries are in stack
 * @return the number of children added to the list
 *
 * NB: non-null "stack" means that new stacks will be added to "list" as
 * output, instead of direct node pointers!
 */
static int add_nexthops(struct list *list, struct graph_node *node,
                        struct graph_node **stack, size_t stackpos)
{
        int added = 0;
        struct graph_node *child;
        struct graph_node **nextstack;
        for (unsigned int i = 0; i < vector_active(node->to); i++) {
                child = vector_slot(node->to, i);
                size_t j;
                struct cmd_token *token = child->data;
                if (!token->allowrepeat && stack) {
                        for (j = 0; j < stackpos; j++)
                                if (child == stack[j])
                                        break;
                        if (j != stackpos)
                                continue;
                }
                if (token->type >= SPECIAL_TKN && token->type != END_TKN) {
                        added += add_nexthops(list, child, stack, stackpos);
                } else {
                        if (stack) {
                                nextstack = XMALLOC(
                                        MTYPE_CMD_MATCHSTACK,
                                        (stackpos + 1)
                                                * sizeof(struct graph_node *));
                                nextstack[0] = child;
                                memcpy(nextstack + 1, stack,
                                       stackpos * sizeof(struct graph_node *));

                                listnode_add(list, nextstack);
                        } else
                                listnode_add(list, child);
                        added++;
                }
        }

        return added;
}

/**
 * Determines the node types for which a partial match may count as a full
 * match. Enables command abbrevations.
 *
 * @param[in] type node type
 * @return minimum match level needed to for a token to fully match
 */
static enum match_type min_match_level(enum cmd_token_type type)
{
        switch (type) {
        // anything matches a start node, for the sake of recursion
        case START_TKN:
                return no_match;
        // allowing words to partly match enables command abbreviation
        case WORD_TKN:
                return partly_match;
        default:
                return exact_match;
        }
}

/**
 * Assigns precedence scores to node types.
 *
 * @param[in] type node type to score
 * @return precedence score
 */
static int score_precedence(enum cmd_token_type type)
{
        switch (type) {
        // some of these are mutually exclusive, so they share
        // the same precedence value
        case IPV4_TKN:
        case IPV4_PREFIX_TKN:
        case IPV6_TKN:
        case IPV6_PREFIX_TKN:
        case MAC_TKN:
        case MAC_PREFIX_TKN:
        case RANGE_TKN:
                return 2;
        case WORD_TKN:
                return 3;
        case VARIABLE_TKN:
                return 4;
        default:
                return 10;
        }
}

/**
 * Picks the better of two possible matches for a token.
 *
 * @param[in] first candidate node matching token
 * @param[in] second candidate node matching token
 * @param[in] token the token being matched
 * @return the best-matching node, or NULL if the two are entirely ambiguous
 */
static struct cmd_token *disambiguate_tokens(struct cmd_token *first,
                                             struct cmd_token *second,
                                             char *input_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, input_token);
        enum match_type smtype = match_token(second, input_token);
        if (fmtype != smtype)
                return fmtype > smtype ? first : second;

        return NULL;
}

/**
 * Picks the better of two possible matches for an input line.
 *
 * @param[in] first candidate list of cmd_token matching vline
 * @param[in] second candidate list of cmd_token matching vline
 * @param[in] vline the input line being matched
 * @param[in] n index into vline to start comparing at
 * @return the best-matching list, or NULL if the two are entirely ambiguous
 */
static struct list *disambiguate(struct list *first, struct list *second,
                                 vector vline, unsigned int n)
{
        // doesn't make sense for these to be inequal length
        assert(first->count == second->count);
        assert(first->count == vector_active(vline) - n + 1);

        struct listnode *fnode = listhead(first), *snode = listhead(second);
        struct cmd_token *ftok = listgetdata(fnode), *stok = listgetdata(snode),
                         *best = NULL;

        // compare each token, if one matches better use that one
        for (unsigned int i = n; i < vector_active(vline); i++) {
                char *token = vector_slot(vline, i);
                if ((best = disambiguate_tokens(ftok, stok, token)))
                        return best == ftok ? first : second;
                fnode = listnextnode(fnode);
                snode = listnextnode(snode);
                ftok = listgetdata(fnode);
                stok = listgetdata(snode);
        }

        return NULL;
}

/*
 * Deletion function for arglist.
 *
 * Since list->del for arglists expects all listnode->data to hold cmd_token,
 * but arglists have cmd_element as the data for the tail, this function
 * manually deletes the tail before deleting the rest of the list as usual.
 *
 * The cmd_element at the end is *not* a copy. It is the one and only.
 *
 * @param list the arglist to delete
 */
static void del_arglist(struct list *list)
{
        // manually delete last node
        struct listnode *tail = listtail(list);
        tail->data = NULL;
        list_delete_node(list, tail);

        // delete the rest of the list as usual
        list_delete_and_null(&list);
}

/*---------- token level matching functions ----------*/

static enum match_type match_token(struct cmd_token *token, char *input_token)
{
        // nothing trivially matches everything
        if (!input_token)
                return trivial_match;

        switch (token->type) {
        case WORD_TKN:
                return match_word(token, input_token);
        case IPV4_TKN:
                return match_ipv4(input_token);
        case IPV4_PREFIX_TKN:
                return match_ipv4_prefix(input_token);
        case IPV6_TKN:
                return match_ipv6_prefix(input_token, false);
        case IPV6_PREFIX_TKN:
                return match_ipv6_prefix(input_token, true);
        case RANGE_TKN:
                return match_range(token, input_token);
        case VARIABLE_TKN:
                return match_variable(token, input_token);
        case MAC_TKN:
                return match_mac(input_token, false);
        case MAC_PREFIX_TKN:
                return match_mac(input_token, true);
        case END_TKN:
        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];

        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];

        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;
}


#define IPV6_ADDR_STR   "0123456789abcdefABCDEF:."
#define IPV6_PREFIX_STR "0123456789abcdefABCDEF:./"
#define STATE_START     1
#define STATE_COLON     2
#define STATE_DOUBLE    3
#define STATE_ADDR      4
#define STATE_DOT       5
#define STATE_SLASH     6
#define STATE_MASK      7

static enum match_type match_ipv6_prefix(const char *str, bool prefix)
{
        int state = STATE_START;
        int colons = 0, nums = 0, double_colon = 0;
        int mask;
        const char *sp = NULL, *start = str;
        char *endptr = NULL;

        if (str == NULL)
                return partly_match;

        if (strspn(str, prefix ? IPV6_PREFIX_STR : IPV6_ADDR_STR)
            != strlen(str))
                return no_match;

        while (*str != '\0' && state != STATE_MASK) {
                switch (state) {
                case STATE_START:
                        if (*str == ':') {
                                if (*(str + 1) != ':' && *(str + 1) != '\0')
                                        return no_match;
                                colons--;
                                state = STATE_COLON;
                        } else {
                                sp = str;
                                state = STATE_ADDR;
                        }

                        continue;
                case STATE_COLON:
                        colons++;
                        if (*(str + 1) == '/')
                                return no_match;
                        else if (*(str + 1) == ':')
                                state = STATE_DOUBLE;
                        else {
                                sp = str + 1;
                                state = STATE_ADDR;
                        }
                        break;
                case STATE_DOUBLE:
                        if (double_colon)
                                return no_match;

                        if (*(str + 1) == ':')
                                return no_match;
                        else {
                                if (*(str + 1) != '\0' && *(str + 1) != '/')
                                        colons++;
                                sp = str + 1;

                                if (*(str + 1) == '/')
                                        state = STATE_SLASH;
                                else
                                        state = STATE_ADDR;
                        }

                        double_colon++;
                        nums += 1;
                        break;
                case STATE_ADDR:
                        if (*(str + 1) == ':' || *(str + 1) == '.'
                            || *(str + 1) == '\0' || *(str + 1) == '/') {
                                if (str - sp > 3)
                                        return no_match;

                                for (; sp <= str; sp++)
                                        if (*sp == '/')
                                                return no_match;

                                nums++;

                                if (*(str + 1) == ':')
                                        state = STATE_COLON;
                                else if (*(str + 1) == '.') {
                                        if (colons || double_colon)
                                                state = STATE_DOT;
                                        else
                                                return no_match;
                                } else if (*(str + 1) == '/')
                                        state = STATE_SLASH;
                        }
                        break;
                case STATE_DOT:
                        state = STATE_ADDR;
                        break;
                case STATE_SLASH:
                        if (*(str + 1) == '\0')
                                return partly_match;

                        state = STATE_MASK;
                        break;
                default:
                        break;
                }

                if (nums > 11)
                        return no_match;

                if (colons > 7)
                        return no_match;

                str++;
        }

        if (!prefix) {
                struct sockaddr_in6 sin6_dummy;
                int ret = inet_pton(AF_INET6, start, &sin6_dummy.sin6_addr);
                return ret == 1 ? exact_match : partly_match;
        }

        if (state < STATE_MASK)
                return partly_match;

        mask = strtol(str, &endptr, 10);
        if (*endptr != '\0')
                return no_match;

        if (mask < 0 || mask > 128)
                return no_match;

        return exact_match;
}

static enum match_type match_range(struct cmd_token *token, const char *str)
{
        assert(token->type == RANGE_TKN);

        char *endptr = NULL;
        long long val;

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

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

static enum match_type match_word(struct cmd_token *token, const char *word)
{
        assert(token->type == WORD_TKN);

        // if the passed token is 0 length, partly match
        if (!strlen(word))
                return partly_match;

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

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

        return no_match;
}

static enum match_type match_variable(struct cmd_token *token, const char *word)
{
        assert(token->type == VARIABLE_TKN);
        return exact_match;
}

#define MAC_CHARS "ABCDEFabcdef0123456789:"

static enum match_type match_mac(const char *word, bool prefix)
{
        /* 6 2-digit hex numbers separated by 5 colons */
        size_t mac_explen = 6 * 2 + 5;
        /* '/' + 2-digit integer */
        size_t mask_len = 1 + 2;
        unsigned int i;
        char *eptr;
        unsigned int maskval;

        /* length check */
        if (strlen(word) > mac_explen + (prefix ? mask_len : 0))
                return no_match;

        /* address check */
        for (i = 0; i < mac_explen; i++) {
                if (word[i] == '\0' || !strchr(MAC_CHARS, word[i]))
                        break;
                if (((i + 1) % 3 == 0) != (word[i] == ':'))
                        return no_match;
        }

        /* incomplete address */
        if (i < mac_explen && word[i] == '\0')
                return partly_match;
        else if (i < mac_explen)
                return no_match;

        /* mask check */
        if (prefix && word[i] == '/') {
                if (word[++i] == '\0')
                        return partly_match;

                maskval = strtoul(&word[i], &eptr, 10);
                if (*eptr != '\0' || maskval > 48)
                        return no_match;
        } else if (prefix && word[i] == '\0') {
                return partly_match;
        } else if (prefix) {
                return no_match;
        }

        return exact_match;
}