NetworkInador/common/resolv_conf_parser.c

/*
 * resolv_conf_parser.c
 * This file is part of NetworkInador
 *
 * Copyright (C) 2023 - Félix Arreola Rodríguez
 *
 * NetworkInador 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.
 *
 * NetworkInador 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 NetworkInador; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, 
 * Boston, MA  02110-1301  USA
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>

#include "resolv_conf_defs.h"
#include "resolv_conf_parser.h"
#include "utils.h"
#include "flist.h"

static const char *resolv_conf_keywords[NUM_RESOLV_TYPES] = {
	"nameserver",
	"domain",
	"search",
	"sortlist",
	"options"
};

int resolv_conf_parse_line (const char *line, int *ns_family, struct_addr *nameserver, char *value, const size_t value_size) {
	int g, len;
	int af;
	struct_addr temp_addr;
	int ret;
	
	/* Recorrer cada palabra clave posible de los resolv.conf */
	for (g = 0; g < NUM_RESOLV_TYPES; g++) {
		len = strlen (resolv_conf_keywords[g]);
		if (strncmp (line, resolv_conf_keywords[g], len) == 0 && line[len] == ' ') {
			if (g == RESOLV_TYPE_NAMESERVER) {
				/* Los nameserver solo pueden ser direcciones IP de IPv4 o IPv6 */
				af = AF_INET;
				ret = inet_pton (AF_INET, &line[len + 1], &temp_addr);
				if (ret == 0) {
					af = AF_INET6;
					ret = inet_pton (AF_INET6, &line[len + 1], &temp_addr);
				}
				
				if (ret == 0) {
					/* No es una dirección IP, ignorar */
					break;
				}
			} else {
				/* Revisar por posibles restricciones en otros tipos */
			}
			
			strncpy (value, &line[len + 1], value_size);
			value[value_size - 1] = 0;
			
			if (g == RESOLV_TYPE_NAMESERVER) {
				*ns_family = af;
				memcpy (nameserver, &temp_addr, sizeof (temp_addr));
			} else {
				*ns_family = AF_UNSPEC;
				memset (nameserver, 0, sizeof (temp_addr));
			}
			
			return g;
		}
	}
	
	/* No es alguna linea válida */
	return -1;
}

FList * resolv_parser_search_entry (FList *all_entries, const int resolv_type, const int ns_family, const struct_addr *nameserver, const char *value, int skip_tagged) {
	FList *g;
	ResolvConfEntry *entry;
	
	g = all_entries;
	while (g != NULL) {
		entry = (ResolvConfEntry *) g->data;
		
		if (resolv_type != entry->resolv_type) {
			/* Pasar a la siguiente entrada, no es del mismo tipo */
			g = g->next;
			continue;
		}
		
		if (skip_tagged == 1 && entry->tagged == 1) {
			/* Pasar a la siguiente entrada, nos pidieron omitir las marcadas en el archivo */
			g = g->next;
			continue;
		}
		
		/* Comparar dependiendo del tipo */
		if (resolv_type == RESOLV_TYPE_NAMESERVER) {
			if (ns_family == AF_INET && entry->ns_family == AF_INET) {
				if (memcmp (nameserver, &entry->nameserver, sizeof (struct in_addr)) == 0) {
					/* Es la entrada que andamos buscando */
					return g;
				}
			} else if (ns_family == AF_INET6 && entry->ns_family == AF_INET6) {
				if (memcmp (nameserver, &entry->nameserver, sizeof (struct in6_addr)) == 0) {
					return g;
				}
			}
		} else {
			/* TODO: Revisar si las otras entradas requieren otro tipo de comparación */
			if (strcmp (value, entry->value) == 0) {
				return g;
			}
		}
		
		g = g->next;
	}
	
	return NULL;
}

FList * resolv_parser_parse_local_file (FList *all_entries, FILE *fd, int origin) {
	char buffer[8192], value[2048];
	ResolvConfEntry *entry = NULL;
	FList *pos, *next;
	int g, len;
	struct_addr direccion;
	int type;
	int family;
	int order;
	
	order = 1;
	while (fgets (buffer, sizeof (buffer), fd), feof (fd) == 0) {
		utils_trim (buffer);
		utils_trim_comment (buffer);
		if (buffer[0] == 0) continue;
		
		type = resolv_conf_parse_line (buffer, &family, &direccion, value, sizeof (value));
		
		if (type == -1) {
			/* Linea no válida de acuerdo al parser, ignorar */
			continue;
		}
		/* Tenemos una linea buena, buscar si esta linea ya existe en nuestra lista de entradas */
		pos = resolv_parser_search_entry (all_entries, type, family, &direccion, value, 1);
		
		if (pos != NULL) {
			/* Ya existe, refrescar que está en el archivo */
			entry = (ResolvConfEntry *) pos->data;
		} else {
			/* Como no existe, crear y anexar al final de la lista */
			entry = (ResolvConfEntry *) malloc (sizeof (ResolvConfEntry));
			
			entry->resolv_type = type;
			entry->origin = origin;
			entry->for_purge = 0;
			
			entry->ns_family = family;
			memcpy (&entry->nameserver, &direccion, sizeof (direccion));
			strncpy (entry->value, value, sizeof (entry->value));
			
			entry->owner_interface_index = 0;
			entry->owner_prog[0] = 0;
			
			all_entries = f_list_append (all_entries, entry);
		}
		entry->tagged = 1;
		entry->file_order = order++;
	}
	
	return all_entries;
}