/*
 * eset_wap (ESET Web Access Protection module)
 * Copyright (C) 1992-2025 ESET, spol. s r.o.
 *
 * 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 3 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, see <https://www.gnu.org/licenses/>.
 *
 * In case of any questions, you can contact us at ESET, spol. s r.o., Einsteinova 24, 851 01 Bratislava, Slovakia.
 */

#include "ewap_pid_map.h"

#include <linux/slab.h>

#include "ewap_helpers.h"

static struct kmem_cache *ewap_pid_node_allocator = NULL;

int ewap_pid_map_allocator_init(void) {
  ewap_pid_node_allocator = kmem_cache_create(
      "ewap_pid_node_allocator", sizeof(struct ewap_pid_node),
      __alignof__(struct ewap_pid_node), SLAB_RECLAIM_ACCOUNT, NULL);

  if (!ewap_pid_node_allocator) {
    return -ENOMEM;
  }

  return 0;
}

void ewap_pid_map_allocator_deinit(void) {
  if (ewap_pid_node_allocator) {
    kmem_cache_destroy(ewap_pid_node_allocator);
  }
}

struct ewap_pid_node *ewap_pid_node_new(pid_t pid) {
  struct ewap_pid_node *node =
      kmem_cache_zalloc(ewap_pid_node_allocator, GFP_KERNEL);
  if (node == NULL) {
    return ERR_PTR(-ENOMEM);
  }

  node->pid = pid;
  INIT_LIST_HEAD(&node->connections);

  ewap_pr_log(EWAP_LOG_CONNECTIONS, "pid_node created pid: %d", node->pid);

  return node;
}

void ewap_pid_node_free(struct ewap_pid_node *node) {
  if (node) {
    ewap_pr_log(EWAP_LOG_CONNECTIONS, "pid_node deleted pid: %d", node->pid);
    kmem_cache_free(ewap_pid_node_allocator, node);
  }
}

void ewap_pid_map_init(struct ewap_pid_map *map) { map->pids = RB_ROOT; }

void ewap_pid_map_deinit(struct ewap_pid_map *map) {
  struct ewap_pid_node *tmp;
  struct ewap_pid_node *cursor;
  rbtree_postorder_for_each_entry_safe(tmp, cursor, &map->pids, node) {
    ewap_pid_node_free(tmp);
  }
}

static struct ewap_pid_node *ewap_pid_map_find_node(struct ewap_pid_map *map,
                                                    pid_t pid,
                                                    struct rb_node **parent) {
  struct rb_node *p = NULL;
  struct rb_node *node = map->pids.rb_node;
  struct ewap_pid_node *result = NULL;

  while (node) {
    struct rb_node *child;
    struct ewap_pid_node *entry = rb_entry(node, struct ewap_pid_node, node);

    if (pid < entry->pid) {
      child = node->rb_left;
    } else if (pid > entry->pid) {
      child = node->rb_right;
    } else {
      result = entry;
      break;
    }

    p = node;
    node = child;
  }

  if (parent) {
    *parent = p;
  }

  return result;
}

static void ewap_pid_map_insert_node(struct ewap_pid_map *map,
                                     struct ewap_pid_node *node,
                                     struct rb_node *parent) {
  struct rb_node **link;
  struct rb_root *root = &map->pids;

  if (RB_EMPTY_ROOT(root)) {
    link = &root->rb_node;
  } else {
    struct ewap_pid_node *parent_entry;

    if (unlikely(parent == NULL)) {
      BUG();
    }

    parent_entry = rb_entry(parent, struct ewap_pid_node, node);

    if (node->pid < parent_entry->pid) {
      link = &parent->rb_left;
    } else if (node->pid > parent_entry->pid) {
      link = &parent->rb_right;
    } else {
      BUG();
    }
  }

  rb_link_node(&node->node, parent, link);
  rb_insert_color(&node->node, root);
}

bool ewap_pid_map_add_connection(struct ewap_pid_map *map,
                                 struct ewap_pid_node *new_node,
                                 struct ewap_pid_node **out) {
  struct rb_node *parent = NULL;
  struct ewap_pid_node *node =
      ewap_pid_map_find_node(map, new_node->pid, &parent);

  if (node) {
    *out = node;
    return false;
  }

  ewap_pid_map_insert_node(map, new_node, parent);
  *out = new_node;
  return true;
}

struct ewap_pid_node *ewap_pid_map_extract_node(struct ewap_pid_map *map,
                                                pid_t pid) {
  struct ewap_pid_node *node = ewap_pid_map_find_node(map, pid, NULL);
  if (node) {
    rb_erase(&node->node, &map->pids);
  }

  return node;
}