dns.h

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/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2022-2025 OpenVPN Inc <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  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/>.
 */
 
#ifndef DNS_H
#define DNS_H
 
#include "buffer.h"
#include "env_set.h"
#include "tun.h"
 
enum dns_security
{
    DNS_SECURITY_UNSET,
    DNS_SECURITY_NO,
    DNS_SECURITY_YES,
    DNS_SECURITY_OPTIONAL
};
 
enum dns_server_transport
{
    DNS_TRANSPORT_UNSET,
    DNS_TRANSPORT_PLAIN,
    DNS_TRANSPORT_HTTPS,
    DNS_TRANSPORT_TLS
};
 
enum dns_updown_flags
{
    DNS_UPDOWN_NO_FLAGS,
    DNS_UPDOWN_USER_SET,
    DNS_UPDOWN_FORCED
};
 
struct dns_domain
{
    struct dns_domain *next;
    const char *name;
};
 
struct dns_server_addr
{
    union
    {
        struct in_addr a4;
        struct in6_addr a6;
    } in;
    sa_family_t family;
    in_port_t port;
};
 
struct dns_server
{
    struct dns_server *next;
    long priority;
    size_t addr_count;
    struct dns_server_addr addr[8];
    struct dns_domain *domains;
    enum dns_security dnssec;
    enum dns_server_transport transport;
    const char *sni;
};
 
struct dns_updown_runner_info
{
    bool required;
    int fds[2];
#if !defined(_WIN32)
    pid_t pid;
#endif
};
 
#ifndef N_DHCP_ADDR
#define N_DHCP_ADDR 4
#endif
 
#ifndef N_SEARCH_LIST_LEN
#define N_SEARCH_LIST_LEN 10
#endif
 
struct dhcp_options
{
    in_addr_t dns[N_DHCP_ADDR];
    int dns_len;
 
    struct in6_addr dns6[N_DHCP_ADDR];
    int dns6_len;
 
    const char *domain;
    const char *domain_search_list[N_SEARCH_LIST_LEN];
    int domain_search_list_len;
};
 
struct dns_options
{
    struct dhcp_options from_dhcp;
    struct dns_domain *search_domains;
    struct dns_server *servers_prepull;
    struct dns_server *servers;
    struct gc_arena gc;
    const char *updown;
    enum dns_updown_flags updown_flags;
};
 
bool dns_server_priority_parse(long *priority, const char *str, bool pulled);
 
struct dns_server *dns_server_get(struct dns_server **entry, long priority, struct gc_arena *gc);
 
void dns_domain_list_append(struct dns_domain **entry, char **domains, struct gc_arena *gc);
 
bool dns_server_addr_parse(struct dns_server *server, const char *addr);
 
bool dns_options_verify(int msglevel, const struct dns_options *o);
 
struct dns_options clone_dns_options(const struct dns_options *o, struct gc_arena *gc);
 
void dns_options_preprocess_pull(struct dns_options *o);
 
void dns_options_postprocess_pull(struct dns_options *o);
 
void run_dns_up_down(bool up, struct options *o, const struct tuntap *tt,
                     struct dns_updown_runner_info *duri);
 
void show_dns_options(const struct dns_options *o);
 
static inline bool
dns_updown_user_set(const struct dns_options *o)
{
    return o->updown_flags == DNS_UPDOWN_USER_SET;
}
 
static inline bool
dns_updown_forced(const struct dns_options *o)
{
    return o->updown_flags == DNS_UPDOWN_FORCED;
}
 
#endif /* ifndef DNS_H */