/*
 * libebtc.c, January 2004
 *
 * Contains the functions with which to make a table in userspace.
 *
 * Author: Bart De Schuymer
 *
 *  This code is stongly inspired on the iptables code which is
 *  Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 *
 * This program 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 of the
 * License, or (at your option) any later version.
 *
 * This program 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; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include "include/ebtables_u.h"
#include "include/ethernetdb.h"
#include <unistd.h>
#include <fcntl.h>
#include <sys/wait.h>

static void decrease_chain_jumps(struct ebt_u_replace *replace);
static int iterate_entries(struct ebt_u_replace *replace, int type);

/* The standard names */
const char *ebt_hooknames[NF_BR_NUMHOOKS] =
{
       [NF_BR_PRE_ROUTING]"PREROUTING",
       [NF_BR_LOCAL_IN]"INPUT",
       [NF_BR_FORWARD]"FORWARD",
       [NF_BR_LOCAL_OUT]"OUTPUT",
       [NF_BR_POST_ROUTING]"POSTROUTING",
       [NF_BR_BROUTING]"BROUTING"
};

/* The four target names */
const char* ebt_standard_targets[NUM_STANDARD_TARGETS] =
{
       "ACCEPT",
       "DROP",
       "CONTINUE",
       "RETURN",
};

/* The lists of supported tables, matches, watchers and targets */
struct ebt_u_table *ebt_tables;
struct ebt_u_match *ebt_matches;
struct ebt_u_watcher *ebt_watchers;
struct ebt_u_target *ebt_targets;

/* Find the right structure belonging to a name */
struct ebt_u_target *ebt_find_target(const char *name)
{
       struct ebt_u_target *t = ebt_targets;

       while (t && strcmp(t->name, name))
               t = t->next;
       return t;
}

struct ebt_u_match *ebt_find_match(const char *name)
{
       struct ebt_u_match *m = ebt_matches;

       while (m && strcmp(m->name, name))
               m = m->next;
       return m;
}

struct ebt_u_watcher *ebt_find_watcher(const char *name)
{
       struct ebt_u_watcher *w = ebt_watchers;

       while (w && strcmp(w->name, name))
               w = w->next;
       return w;
}

struct ebt_u_table *ebt_find_table(const char *name)
{
       struct ebt_u_table *t = ebt_tables;

       while (t && strcmp(t->name, name))
               t = t->next;
       return t;
}

/* Prints all registered extensions */
void ebt_list_extensions()
{
       struct ebt_u_table *tbl = ebt_tables;
        struct ebt_u_target *t = ebt_targets;
        struct ebt_u_match *m = ebt_matches;
        struct ebt_u_watcher *w = ebt_watchers;

       PRINT_VERSION;
       printf("Loaded userspace extensions:\n\nLoaded tables:\n");
        while (tbl) {
               printf("%s\n", tbl->name);
                tbl = tbl->next;
       }
       printf("\nLoaded targets:\n");
        while (t) {
               printf("%s\n", t->name);
                t = t->next;
       }
       printf("\nLoaded matches:\n");
        while (m) {
               printf("%s\n", m->name);
                m = m->next;
       }
       printf("\nLoaded watchers:\n");
        while (w) {
               printf("%s\n", w->name);
                w = w->next;
       }
}

/* Get the table from the kernel or from a binary file
 * init: 1 = ask the kernel for the initial contents of a table, i.e. the
 *           way it looks when the table is insmod'ed
 *       0 = get the current data in the table */
int ebt_get_kernel_table(struct ebt_u_replace *replace, int init)
{
       if (!ebt_find_table(replace->name)) {
               ebt_print_error("Bad table name '%s'", replace->name);
               return -1;
       }
       /* Get the kernel's information */
       if (ebt_get_table(replace, init)) {
               if (ebt_errormsg[0] != '\0')
                       return -1;
               ebtables_insmod("ebtables");
               if (ebt_get_table(replace, init)) {
                       ebt_print_error("The kernel doesn't support the ebtables '%s' table", replace->name);
                       return -1;
               }
       }
       return 0;
}

/* Put sane values into a new entry */
void ebt_initialize_entry(struct ebt_u_entry *e)
{
       e->bitmask = EBT_NOPROTO;
       e->invflags = 0;
       e->ethproto = 0;
       strcpy(e->in, "");
       strcpy(e->out, "");
       strcpy(e->logical_in, "");
       strcpy(e->logical_out, "");
       e->m_list = NULL;
       e->w_list = NULL;
       e->t = (struct ebt_entry_target *)ebt_find_target(EBT_STANDARD_TARGET);
       ebt_find_target(EBT_STANDARD_TARGET)->used = 1;
       e->cnt.pcnt = e->cnt.bcnt = e->cnt_surplus.pcnt = e->cnt_surplus.bcnt = 0;

       if (!e->t)
               ebt_print_bug("Couldn't load standard target");
       ((struct ebt_standard_target *)((struct ebt_u_target *)e->t)->t)->verdict = EBT_CONTINUE;
}

/* Free up the memory of the table held in userspace, *replace can be reused */
void ebt_cleanup_replace(struct ebt_u_replace *replace)
{
       int i;
       struct ebt_u_entries *entries;
       struct ebt_cntchanges *cc1, *cc2;
       struct ebt_u_entry *u_e1, *u_e2;

       replace->name[0] = '\0';
       replace->valid_hooks = 0;
       replace->nentries = 0;
       replace->num_counters = 0;
       replace->flags = 0;
       replace->command = 0;
       replace->selected_chain = -1;
       free(replace->filename);
       replace->filename = NULL;
       free(replace->counters);
       replace->counters = NULL;

       for (i = 0; i < replace->num_chains; i++) {
               if (!(entries = replace->chains[i]))
                       continue;
               u_e1 = entries->entries->next;
               while (u_e1 != entries->entries) {
                       ebt_free_u_entry(u_e1);
                       u_e2 = u_e1->next;
                       free(u_e1);
                       u_e1 = u_e2;
               }
               free(entries->entries);
               free(entries);
               replace->chains[i] = NULL;
       }
       cc1 = replace->cc->next;
       while (cc1 != replace->cc) {
               cc2 = cc1->next;
               free(cc1);
               cc1 = cc2;
       }
       replace->cc->next = replace->cc->prev = replace->cc;
}

/* Should be called, e.g., between 2 rule adds */
void ebt_reinit_extensions()
{
       struct ebt_u_match *m;
       struct ebt_u_watcher *w;
       struct ebt_u_target *t;
       int size;

       /* The init functions should determine by themselves whether they are
        * called for the first time or not (when necessary). */
       for (m = ebt_matches; m; m = m->next) {
               if (m->used) {
                       size = EBT_ALIGN(m->size) + sizeof(struct ebt_entry_match);
                       m->m = (struct ebt_entry_match *)malloc(size);
                       if (!m->m)
                               ebt_print_memory();
                       strcpy(m->m->u.name, m->name);
                       m->m->match_size = EBT_ALIGN(m->size);
                       m->used = 0;
               }
               m->flags = 0; /* An error can occur before used is set, while flags is changed. */
               m->init(m->m);
       }
       for (w = ebt_watchers; w; w = w->next) {
               if (w->used) {
                       size = EBT_ALIGN(w->size) + sizeof(struct ebt_entry_watcher);
                       w->w = (struct ebt_entry_watcher *)malloc(size);
                       if (!w->w)
                               ebt_print_memory();
                       strcpy(w->w->u.name, w->name);
                       w->w->watcher_size = EBT_ALIGN(w->size);
                       w->used = 0;
               }
               w->flags = 0;
               w->init(w->w);
       }
       for (t = ebt_targets; t; t = t->next) {
               if (t->used) {
                       size = EBT_ALIGN(t->size) + sizeof(struct ebt_entry_target);
                       t->t = (struct ebt_entry_target *)malloc(size);
                       if (!t->t)
                               ebt_print_memory();
                       strcpy(t->t->u.name, t->name);
                       t->t->target_size = EBT_ALIGN(t->size);
                       t->used = 0;
               }
               t->flags = 0;
               t->init(t->t);
       }
}

/* This doesn't free e, because the calling function might need e->next */
void ebt_free_u_entry(struct ebt_u_entry *e)
{
       struct ebt_u_match_list *m_l, *m_l2;
       struct ebt_u_watcher_list *w_l, *w_l2;

       m_l = e->m_list;
       while (m_l) {
               m_l2 = m_l->next;
               free(m_l->m);
               free(m_l);
               m_l = m_l2;
       }
       w_l = e->w_list;
       while (w_l) {
               w_l2 = w_l->next;
               free(w_l->w);
               free(w_l);
               w_l = w_l2;
       }
       free(e->t);
}

static char *get_modprobe(void)
{
       int procfile;
       char *ret;

       procfile = open(PROC_SYS_MODPROBE, O_RDONLY);
       if (procfile < 0)
               return NULL;

       ret = malloc(1024);
       if (ret) {
               if (read(procfile, ret, 1024) == -1)
                       goto fail;
               /* The kernel adds a '\n' */
               ret[1023] = '\n';
               *strchr(ret, '\n') = '\0';
               close(procfile);
               return ret;
       }
 fail:
       free(ret);
       close(procfile);
       return NULL;
}

char *ebt_modprobe;
/* Try to load the kernel module, analogous to ip_tables.c */
int ebtables_insmod(const char *modname)
{
       char *buf = NULL;
       char *argv[3];

       /* If they don't explicitly set it, read out of /proc */
       if (!ebt_modprobe) {
               buf = get_modprobe();
               if (!buf)
                       return -1;
               ebt_modprobe = buf; /* Keep the value for possible later use */
       }

       switch (fork()) {
       case 0:
               argv[0] = (char *)ebt_modprobe;
               argv[1] = (char *)modname;
               argv[2] = NULL;
               execv(argv[0], argv);

               /* Not usually reached */
               exit(0);
       case -1:
               return -1;

       default: /* Parent */
               wait(NULL);
       }

       return 0;
}

/* Parse the chain name and return a pointer to the chain base.
 * Returns NULL on failure. */
struct ebt_u_entries *ebt_name_to_chain(const struct ebt_u_replace *replace, const char* arg)
{
       int i;
       struct ebt_u_entries *chain;

       for (i = 0; i < replace->num_chains; i++) {
               if (!(chain = replace->chains[i]))
                       continue;
               if (!strcmp(arg, chain->name))
                       return chain;
       }
       return NULL;
}

/* Parse the chain name and return the corresponding chain nr
 * returns -1 on failure */
int ebt_get_chainnr(const struct ebt_u_replace *replace, const char* arg)
{
       int i;

       for (i = 0; i < replace->num_chains; i++) {
               if (!replace->chains[i])
                       continue;
               if (!strcmp(arg, replace->chains[i]->name))
                       return i;
       }
       return -1;
}

     /*
************
************
**COMMANDS**
************
************
     */

/* Change the policy of selected_chain.
 * Handing a bad policy to this function is a bug. */
void ebt_change_policy(struct ebt_u_replace *replace, int policy)
{
       struct ebt_u_entries *entries = ebt_to_chain(replace);

       if (policy < -NUM_STANDARD_TARGETS || policy == EBT_CONTINUE)
               ebt_print_bug("Wrong policy: %d", policy);
       entries->policy = policy;
}

void ebt_delete_cc(struct ebt_cntchanges *cc)
{
       if (cc->type == CNT_ADD) {
               cc->prev->next = cc->next;
               cc->next->prev = cc->prev;
               free(cc);
       }
       cc->type = CNT_DEL;
}

void ebt_empty_chain(struct ebt_u_entries *entries)
{
       struct ebt_u_entry *u_e = entries->entries->next, *tmp;
       while (u_e != entries->entries) {
               ebt_delete_cc(u_e->cc);
               ebt_free_u_entry(u_e);
               tmp = u_e->next;
               free(u_e);
               u_e = tmp;
       }
       entries->entries->next = entries->entries->prev = entries->entries;
       entries->nentries = 0;
}

/* Flush one chain or the complete table
 * If selected_chain == -1 then flush the complete table */
void ebt_flush_chains(struct ebt_u_replace *replace)
{
       int i, numdel;
       struct ebt_u_entries *entries = ebt_to_chain(replace);

       /* Flush whole table */
       if (!entries) {
               if (replace->nentries == 0)
                       return;
               replace->nentries = 0;

               /* Free everything and zero (n)entries */
               for (i = 0; i < replace->num_chains; i++) {
                       if (!(entries = replace->chains[i]))
                               continue;
                       entries->counter_offset = 0;
                       ebt_empty_chain(entries);
               }
               return;
       }

       if (entries->nentries == 0)
               return;
       replace->nentries -= entries->nentries;
       numdel = entries->nentries;

       /* Update counter_offset */
       for (i = replace->selected_chain+1; i < replace->num_chains; i++) {
               if (!(entries = replace->chains[i]))
                       continue;
               entries->counter_offset -= numdel;
       }

       entries = ebt_to_chain(replace);
       ebt_empty_chain(entries);
}

#define OPT_COUNT      0x1000 /* This value is also defined in ebtables.c */
/* Returns the rule number on success (starting from 0), -1 on failure
 *
 * This function expects the ebt_{match,watcher,target} members of new_entry
 * to contain pointers to ebt_u_{match,watcher,target} */
int ebt_check_rule_exists(struct ebt_u_replace *replace,
                         struct ebt_u_entry *new_entry)
{
       struct ebt_u_entry *u_e;
       struct ebt_u_match_list *m_l, *m_l2;
       struct ebt_u_match *m;
       struct ebt_u_watcher_list *w_l, *w_l2;
       struct ebt_u_watcher *w;
       struct ebt_u_target *t = (struct ebt_u_target *)new_entry->t;
       struct ebt_u_entries *entries = ebt_to_chain(replace);
       int i, j, k;

       u_e = entries->entries->next;
       /* Check for an existing rule (if there are duplicate rules,
        * take the first occurance) */
       for (i = 0; i < entries->nentries; i++, u_e = u_e->next) {
               if (u_e->ethproto != new_entry->ethproto)
                       continue;
               if (strcmp(u_e->in, new_entry->in))
                       continue;
               if (strcmp(u_e->out, new_entry->out))
                       continue;
               if (strcmp(u_e->logical_in, new_entry->logical_in))
                       continue;
               if (strcmp(u_e->logical_out, new_entry->logical_out))
                       continue;
               if (new_entry->bitmask & EBT_SOURCEMAC &&
                   memcmp(u_e->sourcemac, new_entry->sourcemac, ETH_ALEN))
                       continue;
               if (new_entry->bitmask & EBT_DESTMAC &&
                   memcmp(u_e->destmac, new_entry->destmac, ETH_ALEN))
                       continue;
               if (new_entry->bitmask != u_e->bitmask ||
                   new_entry->invflags != u_e->invflags)
                       continue;
               if (replace->flags & OPT_COUNT && (new_entry->cnt.pcnt !=
                   u_e->cnt.pcnt || new_entry->cnt.bcnt != u_e->cnt.bcnt))
                       continue;
               /* Compare all matches */
               m_l = new_entry->m_list;
               j = 0;
               while (m_l) {
                       m = (struct ebt_u_match *)(m_l->m);
                       m_l2 = u_e->m_list;
                       while (m_l2 && strcmp(m_l2->m->u.name, m->m->u.name))
                               m_l2 = m_l2->next;
                       if (!m_l2 || !m->compare(m->m, m_l2->m))
                               goto letscontinue;
                       j++;
                       m_l = m_l->next;
               }
               /* Now be sure they have the same nr of matches */
               k = 0;
               m_l = u_e->m_list;
               while (m_l) {
                       k++;
                       m_l = m_l->next;
               }
               if (j != k)
                       continue;

               /* Compare all watchers */
               w_l = new_entry->w_list;
               j = 0;
               while (w_l) {
                       w = (struct ebt_u_watcher *)(w_l->w);
                       w_l2 = u_e->w_list;
                       while (w_l2 && strcmp(w_l2->w->u.name, w->w->u.name))
                               w_l2 = w_l2->next;
                       if (!w_l2 || !w->compare(w->w, w_l2->w))
                               goto letscontinue;
                       j++;
                       w_l = w_l->next;
               }
               k = 0;
               w_l = u_e->w_list;
               while (w_l) {
                       k++;
                       w_l = w_l->next;
               }
               if (j != k)
                       continue;
               if (strcmp(t->t->u.name, u_e->t->u.name))
                       continue;
               if (!t->compare(t->t, u_e->t))
                       continue;
               return i;
letscontinue:;
       }
       return -1;
}

/* Add a rule, rule_nr is the rule to update
 * rule_nr specifies where the rule should be inserted
 * rule_nr > 0 : insert the rule right before the rule_nr'th rule
 *               (the first rule is rule 1)
 * rule_nr < 0 : insert the rule right before the (n+rule_nr+1)'th rule,
 *               where n denotes the number of rules in the chain
 * rule_nr == 0: add a new rule at the end of the chain
 *
 * This function expects the ebt_{match,watcher,target} members of new_entry
 * to contain pointers to ebt_u_{match,watcher,target} and updates these
 * pointers so that they point to ebt_{match,watcher,target}, before adding
 * the rule to the chain. Don't free() the ebt_{match,watcher,target} and
 * don't reuse the new_entry after a successful call to ebt_add_rule() */
void ebt_add_rule(struct ebt_u_replace *replace, struct ebt_u_entry *new_entry, int rule_nr)
{
       int i;
       struct ebt_u_entry *u_e;
       struct ebt_u_match_list *m_l;
       struct ebt_u_watcher_list *w_l;
       struct ebt_u_entries *entries = ebt_to_chain(replace);
       struct ebt_cntchanges *cc, *new_cc;

       if (rule_nr <= 0)
               rule_nr += entries->nentries;
       else
               rule_nr--;
       if (rule_nr > entries->nentries || rule_nr < 0) {
               ebt_print_error("The specified rule number is incorrect");
               return;
       }
       /* Go to the right position in the chain */
       if (rule_nr == entries->nentries)
               u_e = entries->entries;
       else {
               u_e = entries->entries->next;
               for (i = 0; i < rule_nr; i++)
                       u_e = u_e->next;
       }
       /* We're adding one rule */
       replace->nentries++;
       entries->nentries++;
       /* Insert the rule */
       new_entry->next = u_e;
       new_entry->prev = u_e->prev;
       u_e->prev->next = new_entry;
       u_e->prev = new_entry;
       new_cc = (struct ebt_cntchanges *)malloc(sizeof(struct ebt_cntchanges));
       if (!new_cc)
               ebt_print_memory();
       new_cc->type = CNT_ADD;
       new_cc->change = 0;
       if (new_entry->next == entries->entries) {
               for (i = replace->selected_chain+1; i < replace->num_chains; i++)
                       if (!replace->chains[i] || replace->chains[i]->nentries == 0)
                               continue;
                       else
                               break;
               if (i == replace->num_chains)
                       cc = replace->cc;
               else
                       cc = replace->chains[i]->entries->next->cc;
       } else
               cc = new_entry->next->cc;
       new_cc->next = cc;
       new_cc->prev = cc->prev;
       cc->prev->next = new_cc;
       cc->prev = new_cc;
       new_entry->cc = new_cc;

       /* Put the ebt_{match, watcher, target} pointers in place */
       m_l = new_entry->m_list;
       while (m_l) {
               m_l->m = ((struct ebt_u_match *)m_l->m)->m;
               m_l = m_l->next;
       }
       w_l = new_entry->w_list;
       while (w_l) {
               w_l->w = ((struct ebt_u_watcher *)w_l->w)->w;
               w_l = w_l->next;
       }
       new_entry->t = ((struct ebt_u_target *)new_entry->t)->t;
       /* Update the counter_offset of chains behind this one */
       for (i = replace->selected_chain+1; i < replace->num_chains; i++) {
               entries = replace->chains[i];
               if (!(entries = replace->chains[i]))
                       continue;
               entries->counter_offset++;
       }
}

/* If *begin==*end==0 then find the rule corresponding to new_entry,
 * else make the rule numbers positive (starting from 0) and check
 * for bad rule numbers. */
static int check_and_change_rule_number(struct ebt_u_replace *replace,
   struct ebt_u_entry *new_entry, int *begin, int *end)
{
       struct ebt_u_entries *entries = ebt_to_chain(replace);

       if (*begin < 0)
               *begin += entries->nentries + 1;
       if (*end < 0)
               *end += entries->nentries + 1;

       if (*begin < 0 || *begin > *end || *end > entries->nentries) {
               ebt_print_error("Sorry, wrong rule numbers");
               return -1;
       }

       if ((*begin * *end == 0) && (*begin + *end != 0))
               ebt_print_bug("begin and end should be either both zero, "
                             "either both non-zero");
       if (*begin != 0) {
               (*begin)--;
               (*end)--;
       } else {
               *begin = ebt_check_rule_exists(replace, new_entry);
               *end = *begin;
               if (*begin == -1) {
                       ebt_print_error("Sorry, rule does not exist");
                       return -1;
               }
       }
       return 0;
}

/* Delete a rule or rules
 * begin == end == 0: delete the rule corresponding to new_entry
 *
 * The first rule has rule nr 1, the last rule has rule nr -1, etc.
 * This function expects the ebt_{match,watcher,target} members of new_entry
 * to contain pointers to ebt_u_{match,watcher,target}. */
void ebt_delete_rule(struct ebt_u_replace *replace,
                    struct ebt_u_entry *new_entry, int begin, int end)
{
       int i,  nr_deletes;
       struct ebt_u_entry *u_e, *u_e2, *u_e3;
       struct ebt_u_entries *entries = ebt_to_chain(replace);

       if (check_and_change_rule_number(replace, new_entry, &begin, &end))
               return;
       /* We're deleting rules */
       nr_deletes = end - begin + 1;
       replace->nentries -= nr_deletes;
       entries->nentries -= nr_deletes;
       /* Go to the right position in the chain */
       u_e = entries->entries->next;
       for (i = 0; i < begin; i++)
               u_e = u_e->next;
       u_e3 = u_e->prev;
       /* Remove the rules */
       for (i = 0; i < nr_deletes; i++) {
               u_e2 = u_e;
               ebt_delete_cc(u_e2->cc);
               u_e = u_e->next;
               /* Free everything */
               ebt_free_u_entry(u_e2);
               free(u_e2);
       }
       u_e3->next = u_e;
       u_e->prev = u_e3;
       /* Update the counter_offset of chains behind this one */
       for (i = replace->selected_chain+1; i < replace->num_chains; i++) {
               if (!(entries = replace->chains[i]))
                       continue;
               entries->counter_offset -= nr_deletes;
       }
}

/* Change the counters of a rule or rules
 * begin == end == 0: change counters of the rule corresponding to new_entry
 *
 * The first rule has rule nr 1, the last rule has rule nr -1, etc.
 * This function expects the ebt_{match,watcher,target} members of new_entry
 * to contain pointers to ebt_u_{match,watcher,target}.
 * The mask denotes the following:
 *    pcnt: mask % 3 = 0 : change; = 1: increment; = 2: decrement
 *    bcnt: mask / 3 = 0 : change; = 1: increment = 2: increment
 * In daemon mode, mask==0 must hold */
void ebt_change_counters(struct ebt_u_replace *replace,
                    struct ebt_u_entry *new_entry, int begin, int end,
                    struct ebt_counter *cnt, int mask)
{
       int i;
       struct ebt_u_entry *u_e;
       struct ebt_u_entries *entries = ebt_to_chain(replace);

       if (check_and_change_rule_number(replace, new_entry, &begin, &end))
               return;
       u_e = entries->entries->next;
       for (i = 0; i < begin; i++)
               u_e = u_e->next;
       for (i = end-begin+1; i > 0; i--) {
               if (mask % 3 == 0) {
                       u_e->cnt.pcnt = (*cnt).pcnt;
                       u_e->cnt_surplus.pcnt = 0;
               } else {
#ifdef EBT_DEBUG
                       if (u_e->cc->type != CNT_NORM)
                               ebt_print_bug("cc->type != CNT_NORM");
#endif
                       u_e->cnt_surplus.pcnt = (*cnt).pcnt;
               }

               if (mask / 3 == 0) {
                       u_e->cnt.bcnt = (*cnt).bcnt;
                       u_e->cnt_surplus.bcnt = 0;
               } else {
#ifdef EBT_DEBUG
                       if (u_e->cc->type != CNT_NORM)
                               ebt_print_bug("cc->type != CNT_NORM");
#endif
                       u_e->cnt_surplus.bcnt = (*cnt).bcnt;
               }
               if (u_e->cc->type != CNT_ADD)
                       u_e->cc->type = CNT_CHANGE;
               u_e->cc->change = mask;
               u_e = u_e->next;
       }
}

/* If selected_chain == -1 then zero all counters,
 * otherwise, zero the counters of selected_chain */
void ebt_zero_counters(struct ebt_u_replace *replace)
{
       struct ebt_u_entries *entries = ebt_to_chain(replace);
       struct ebt_u_entry *next;
       int i;

       if (!entries) {
               for (i = 0; i < replace->num_chains; i++) {
                       if (!(entries = replace->chains[i]))
                               continue;
                       next = entries->entries->next;
                       while (next != entries->entries) {
                               if (next->cc->type == CNT_NORM)
                                       next->cc->type = CNT_CHANGE;
                               next->cnt.bcnt = next->cnt.pcnt = 0;
                               next->cc->change = 0;
                               next = next->next;
                       }
               }
       } else {
               if (entries->nentries == 0)
                       return;

               next = entries->entries->next;
               while (next != entries->entries) {
                       if (next->cc->type == CNT_NORM)
                               next->cc->type = CNT_CHANGE;
                       next->cnt.bcnt = next->cnt.pcnt = 0;
                       next = next->next;
               }
       }
}

/* Add a new chain and specify its policy */
void ebt_new_chain(struct ebt_u_replace *replace, const char *name, int policy)
{
       struct ebt_u_entries *new;

       if (replace->num_chains == replace->max_chains)
               ebt_double_chains(replace);
       new = (struct ebt_u_entries *)malloc(sizeof(struct ebt_u_entries));
       if (!new)
               ebt_print_memory();
       replace->chains[replace->num_chains++] = new;
       new->nentries = 0;
       new->policy = policy;
       new->counter_offset = replace->nentries;
       new->hook_mask = 0;
       strcpy(new->name, name);
       new->entries = (struct ebt_u_entry *)malloc(sizeof(struct ebt_u_entry));
       if (!new->entries)
               ebt_print_memory();
       new->entries->next = new->entries->prev = new->entries;
       new->kernel_start = NULL;
}

/* returns -1 if the chain is referenced, 0 on success */
static int ebt_delete_a_chain(struct ebt_u_replace *replace, int chain, int print_err)
{
       int tmp = replace->selected_chain;
       /* If the chain is referenced, don't delete it,
        * also decrement jumps to a chain behind the
        * one we're deleting */
       replace->selected_chain = chain;
       if (ebt_check_for_references(replace, print_err))
               return -1;
       decrease_chain_jumps(replace);
       ebt_flush_chains(replace);
       replace->selected_chain = tmp;
       free(replace->chains[chain]->entries);
       free(replace->chains[chain]);
       memmove(replace->chains+chain, replace->chains+chain+1, (replace->num_chains-chain-1)*sizeof(void *));
       replace->num_chains--;
       return 0;
}

/* Selected_chain == -1: delete all non-referenced udc
 * selected_chain < NF_BR_NUMHOOKS is illegal */
void ebt_delete_chain(struct ebt_u_replace *replace)
{
       if (replace->selected_chain != -1 && replace->selected_chain < NF_BR_NUMHOOKS)
               ebt_print_bug("You can't remove a standard chain");
       if (replace->selected_chain == -1) {
               int i = NF_BR_NUMHOOKS;

               while (i < replace->num_chains)
                       if (ebt_delete_a_chain(replace, i, 0))
                               i++;
       } else
               ebt_delete_a_chain(replace, replace->selected_chain, 1);
}

/* Rename an existing chain. */
void ebt_rename_chain(struct ebt_u_replace *replace, const char *name)
{
       struct ebt_u_entries *entries = ebt_to_chain(replace);

       if (!entries)
               ebt_print_bug("ebt_rename_chain: entries == NULL");
       strcpy(entries->name, name);
}


           /*
*************************
*************************
**SPECIALIZED*FUNCTIONS**
*************************
*************************
            */


void ebt_double_chains(struct ebt_u_replace *replace)
{
       struct ebt_u_entries **new;

       replace->max_chains *= 2;
       new = (struct ebt_u_entries **)malloc(replace->max_chains*sizeof(void *));
       if (!new)
               ebt_print_memory();
       memcpy(new, replace->chains, replace->max_chains/2*sizeof(void *));
       free(replace->chains);
       replace->chains = new;
}

/* Executes the final_check() function for all extensions used by the rule
 * ebt_check_for_loops should have been executed earlier, to make sure the
 * hook_mask is correct. The time argument to final_check() is set to 1,
 * meaning it's the second time the final_check() function is executed. */
void ebt_do_final_checks(struct ebt_u_replace *replace, struct ebt_u_entry *e,
                        struct ebt_u_entries *entries)
{
       struct ebt_u_match_list *m_l;
       struct ebt_u_watcher_list *w_l;
       struct ebt_u_target *t;
       struct ebt_u_match *m;
       struct ebt_u_watcher *w;

       m_l = e->m_list;
       w_l = e->w_list;
       while (m_l) {
               m = ebt_find_match(m_l->m->u.name);
               m->final_check(e, m_l->m, replace->name,
                  entries->hook_mask, 1);
               if (ebt_errormsg[0] != '\0')
                       return;
               m_l = m_l->next;
       }
       while (w_l) {
               w = ebt_find_watcher(w_l->w->u.name);
               w->final_check(e, w_l->w, replace->name,
                  entries->hook_mask, 1);
               if (ebt_errormsg[0] != '\0')
                       return;
               w_l = w_l->next;
       }
       t = ebt_find_target(e->t->u.name);
       t->final_check(e, e->t, replace->name,
          entries->hook_mask, 1);
}

/* Returns 1 (if it returns) when the chain is referenced, 0 when it isn't.
 * print_err: 0 (resp. 1) = don't (resp. do) print error when referenced */
int ebt_check_for_references(struct ebt_u_replace *replace, int print_err)
{
       if (print_err)
               return iterate_entries(replace, 1);
       else
               return iterate_entries(replace, 2);
}

/* chain_nr: nr of the udc (>= NF_BR_NUMHOOKS)
 * Returns 1 (if it returns) when the chain is referenced, 0 when it isn't.
 * print_err: 0 (resp. 1) = don't (resp. do) print error when referenced */
int ebt_check_for_references2(struct ebt_u_replace *replace, int chain_nr,
                              int print_err)
{
       int tmp = replace->selected_chain, ret;

       replace->selected_chain = chain_nr;
       if (print_err)
               ret = iterate_entries(replace, 1);
       else
               ret = iterate_entries(replace, 2);
       replace->selected_chain = tmp;
       return ret;
}

struct ebt_u_stack
{
       int chain_nr;
       int n;
       struct ebt_u_entry *e;
       struct ebt_u_entries *entries;
};

/* Checks for loops
 * As a by-product, the hook_mask member of each chain is filled in
 * correctly. The check functions of the extensions need this hook_mask
 * to know from which standard chains they can be called. */
void ebt_check_for_loops(struct ebt_u_replace *replace)
{
       int chain_nr , i, j , k, sp = 0, verdict;
       struct ebt_u_entries *entries, *entries2;
       struct ebt_u_stack *stack = NULL;
       struct ebt_u_entry *e;

       /* Initialize hook_mask to 0 */
       for (i = 0; i < replace->num_chains; i++) {
               if (!(entries = replace->chains[i]))
                       continue;
               if (i < NF_BR_NUMHOOKS)
                       /* (1 << NF_BR_NUMHOOKS) implies it's a standard chain
                        * (usefull in the final_check() funtions) */
                       entries->hook_mask = (1 << i) | (1 << NF_BR_NUMHOOKS);
               else
                       entries->hook_mask = 0;
       }
       if (replace->num_chains == NF_BR_NUMHOOKS)
               return;
       stack = (struct ebt_u_stack *)malloc((replace->num_chains - NF_BR_NUMHOOKS) * sizeof(struct ebt_u_stack));
       if (!stack)
               ebt_print_memory();

       /* Check for loops, starting from every base chain */
       for (i = 0; i < NF_BR_NUMHOOKS; i++) {
               if (!(entries = replace->chains[i]))
                       continue;
               chain_nr = i;

               e = entries->entries->next;
               for (j = 0; j < entries->nentries; j++) {
                       if (strcmp(e->t->u.name, EBT_STANDARD_TARGET))
                               goto letscontinue;
                       verdict = ((struct ebt_standard_target *)(e->t))->verdict;
                       if (verdict < 0)
                               goto letscontinue;
                       /* Now see if we've been here before */
                       for (k = 0; k < sp; k++)
                               if (stack[k].chain_nr == verdict + NF_BR_NUMHOOKS) {
                                       ebt_print_error("Loop from chain '%s' to chain '%s'",
                                          replace->chains[chain_nr]->name,
                                          replace->chains[stack[k].chain_nr]->name);
                                       goto free_stack;
                               }
                       entries2 = replace->chains[verdict + NF_BR_NUMHOOKS];
                       /* check if we've dealt with this chain already */
                       if (entries2->hook_mask & (1<<i))
                               goto letscontinue;
                       entries2->hook_mask |= entries->hook_mask;
                       /* Jump to the chain, make sure we know how to get back */
                       stack[sp].chain_nr = chain_nr;
                       stack[sp].n = j;
                       stack[sp].entries = entries;
                       stack[sp].e = e;
                       sp++;
                       j = -1;
                       e = entries2->entries->next;
                       chain_nr = verdict + NF_BR_NUMHOOKS;
                       entries = entries2;
                       continue;
letscontinue:
                       e = e->next;
               }
               /* We are at the end of a standard chain */
               if (sp == 0)
                       continue;
               /* Go back to the chain one level higher */
               sp--;
               j = stack[sp].n;
               chain_nr = stack[sp].chain_nr;
               e = stack[sp].e;
               entries = stack[sp].entries;
               goto letscontinue;
       }
free_stack:
       free(stack);
       return;
}

/* The user will use the match, so put it in new_entry. The ebt_u_match
 * pointer is put in the ebt_entry_match pointer. ebt_add_rule will
 * fill in the final value for new->m. Unless the rule is added to a chain,
 * the pointer will keep pointing to the ebt_u_match (until the new_entry
 * is freed). I know, I should use a union for these 2 pointer types... */
void ebt_add_match(struct ebt_u_entry *new_entry, struct ebt_u_match *m)
{
       struct ebt_u_match_list **m_list, *new;

       for (m_list = &new_entry->m_list; *m_list; m_list = &(*m_list)->next);
       new = (struct ebt_u_match_list *)
          malloc(sizeof(struct ebt_u_match_list));
       if (!new)
               ebt_print_memory();
       *m_list = new;
       new->next = NULL;
       new->m = (struct ebt_entry_match *)m;
}

void ebt_add_watcher(struct ebt_u_entry *new_entry, struct ebt_u_watcher *w)
{
       struct ebt_u_watcher_list **w_list;
       struct ebt_u_watcher_list *new;

       for (w_list = &new_entry->w_list; *w_list; w_list = &(*w_list)->next);
       new = (struct ebt_u_watcher_list *)
          malloc(sizeof(struct ebt_u_watcher_list));
       if (!new)
               ebt_print_memory();
       *w_list = new;
       new->next = NULL;
       new->w = (struct ebt_entry_watcher *)w;
}


        /*
*******************
*******************
**OTHER*FUNCTIONS**
*******************
*******************
         */


/* type = 0 => update chain jumps
 * type = 1 => check for reference, print error when referenced
 * type = 2 => check for reference, don't print error when referenced
 *
 * Returns 1 when type == 1 and the chain is referenced
 * returns 0 otherwise */
static int iterate_entries(struct ebt_u_replace *replace, int type)
{
       int i, j, chain_nr = replace->selected_chain - NF_BR_NUMHOOKS;
       struct ebt_u_entries *entries;
       struct ebt_u_entry *e;

       if (chain_nr < 0)
               ebt_print_bug("iterate_entries: udc = %d < 0", chain_nr);
       for (i = 0; i < replace->num_chains; i++) {
               if (!(entries = replace->chains[i]))
                       continue;
               e = entries->entries->next;
               for (j = 0; j < entries->nentries; j++) {
                       int chain_jmp;

                       if (strcmp(e->t->u.name, EBT_STANDARD_TARGET)) {
                               e = e->next;
                               continue;
                       }
                       chain_jmp = ((struct ebt_standard_target *)e->t)->
                                   verdict;
                       switch (type) {
                       case 1:
                       case 2:
                       if (chain_jmp == chain_nr) {
                               if (type == 2)
                                       return 1;
                               ebt_print_error("Can't delete the chain '%s', it's referenced in chain '%s', rule %d",
                                               replace->chains[chain_nr + NF_BR_NUMHOOKS]->name, entries->name, j);
                               return 1;
                       }
                       break;
                       case 0:
                       /* Adjust the chain jumps when necessary */
                       if (chain_jmp > chain_nr)
                               ((struct ebt_standard_target *)e->t)->verdict--;
                       break;
                       } /* End switch */
                       e = e->next;
               }
       }
       return 0;
}

static void decrease_chain_jumps(struct ebt_u_replace *replace)
{
       iterate_entries(replace, 0);
}

/* Used in initialization code of modules */
void ebt_register_match(struct ebt_u_match *m)
{
       int size = EBT_ALIGN(m->size) + sizeof(struct ebt_entry_match);
       struct ebt_u_match **i;

       m->m = (struct ebt_entry_match *)malloc(size);
       if (!m->m)
               ebt_print_memory();
       strcpy(m->m->u.name, m->name);
       m->m->match_size = EBT_ALIGN(m->size);
       m->init(m->m);

       for (i = &ebt_matches; *i; i = &((*i)->next));
       m->next = NULL;
       *i = m;
}

void ebt_register_watcher(struct ebt_u_watcher *w)
{
       int size = EBT_ALIGN(w->size) + sizeof(struct ebt_entry_watcher);
       struct ebt_u_watcher **i;

       w->w = (struct ebt_entry_watcher *)malloc(size);
       if (!w->w)
               ebt_print_memory();
       strcpy(w->w->u.name, w->name);
       w->w->watcher_size = EBT_ALIGN(w->size);
       w->init(w->w);

       for (i = &ebt_watchers; *i; i = &((*i)->next));
       w->next = NULL;
       *i = w;
}

void ebt_register_target(struct ebt_u_target *t)
{
       int size = EBT_ALIGN(t->size) + sizeof(struct ebt_entry_target);
       struct ebt_u_target **i;

       t->t = (struct ebt_entry_target *)malloc(size);
       if (!t->t)
               ebt_print_memory();
       strcpy(t->t->u.name, t->name);
       t->t->target_size = EBT_ALIGN(t->size);
       t->init(t->t);

       for (i = &ebt_targets; *i; i = &((*i)->next));
       t->next = NULL;
       *i = t;
}

void ebt_register_table(struct ebt_u_table *t)
{
       t->next = ebt_tables;
       ebt_tables = t;
}

void ebt_iterate_matches(void (*f)(struct ebt_u_match *))
{
       struct ebt_u_match *i;

       for (i = ebt_matches; i; i = i->next)
               f(i);
}

void ebt_iterate_watchers(void (*f)(struct ebt_u_watcher *))
{
       struct ebt_u_watcher *i;

       for (i = ebt_watchers; i; i = i->next)
               f(i);
}

void ebt_iterate_targets(void (*f)(struct ebt_u_target *))
{
       struct ebt_u_target *i;

       for (i = ebt_targets; i; i = i->next)
               f(i);
}

/* Don't use this function, use ebt_print_bug() */
void __ebt_print_bug(char *file, int line, char *format, ...)
{
       va_list l;

       va_start(l, format);
       fprintf(stderr, PROGNAME" v"PROGVERSION":%s:%d:--BUG--: \n", file, line);
       vfprintf(stderr, format, l);
       fprintf(stderr, "\n");
       va_end(l);
       exit (-1);
}

/* The error messages are put in here when ebt_silent == 1
 * ebt_errormsg[0] == '\0' implies there was no error */
char ebt_errormsg[ERRORMSG_MAXLEN];
/* When error messages should not be printed on the screen, after which
 * the program exit()s, set ebt_silent to 1. */
int ebt_silent;
/* Don't use this function, use ebt_print_error() */
void __ebt_print_error(char *format, ...)
{
       va_list l;

       va_start(l, format);
       if (ebt_silent && ebt_errormsg[0] == '\0') {
               vsnprintf(ebt_errormsg, ERRORMSG_MAXLEN, format, l);
               va_end(l);
       } else {
               vfprintf(stderr, format, l);
               fprintf(stderr, ".\n");
               va_end(l);
               exit (-1);
       }
}
