Implements client-side DNS proxy server code. More...

#include "core/or/or.h"
#include "feature/client/dnsserv.h"
#include "app/config/config.h"
#include "core/mainloop/connection.h"
#include "core/or/connection_edge.h"
#include "feature/control/control_events.h"
#include "core/mainloop/mainloop.h"
#include "core/mainloop/netstatus.h"
#include "core/or/policies.h"
#include "feature/control/control_connection_st.h"
#include "core/or/entry_connection_st.h"
#include "core/or/listener_connection_st.h"
#include "core/or/socks_request_st.h"
#include "lib/evloop/compat_libevent.h"
#include <event2/dns.h>
#include <event2/dns_compat.h>
#include <event2/dns_struct.h>

Functions
static void	evdns_server_callback (struct evdns_server_request req, void data_)

int	dnsserv_launch_request (const char name, int reverse, control_connection_t control_conn)

void	dnsserv_reject_request (entry_connection_t *conn)

static const char *	evdns_get_orig_address (const struct evdns_server_request req, int rtype, const char addr)

void	dnsserv_resolved (entry_connection_t conn, int answer_type, size_t answer_len, const char answer, int ttl)

void	dnsserv_configure_listener (connection_t *conn)

void	dnsserv_close_listener (connection_t *conn)

Detailed Description

Implements client-side DNS proxy server code.

When a user enables the DNSPort configuration option to have their local Tor client handle DNS requests, this module handles it. It functions as a "DNS Server" on the client side, which client applications use.

Inbound DNS requests are represented as entry_connection_t here (since that's how Tor represents client-side streams), which are kept associated with an evdns_server_request structure as exposed by Libevent's evdns code.

Upon receiving a DNS request, libevent calls our evdns_server_callback() function here, which causes this module to create an entry_connection_t request as appropriate. Later, when that request is answered, connection_edge.c calls dnsserv_resolved() so we can finish up and tell the DNS client.

Definition in file dnsserv.c.

Function Documentation

◆ dnsserv_close_listener()

void dnsserv_close_listener ( connection_t * conn )

Free the evdns server port for conn, which must be an AP_DNS_LISTENER.

Definition at line 407 of file dnsserv.c.

◆ dnsserv_configure_listener()

void dnsserv_configure_listener ( connection_t * conn )

Set up the evdns server port for the UDP socket on conn, which must be an AP_DNS_LISTENER

Definition at line 391 of file dnsserv.c.

◆ dnsserv_launch_request()

int dnsserv_launch_request	(	const char *	name,
		int	reverse,
		control_connection_t *	control_conn
	)

Helper function: called whenever the client sends a resolve request to our controller. We need to eventually answer the request req. Returns 0 if the controller will be getting (or has gotten) an event in response; -1 if we couldn't launch the request.

Definition at line 210 of file dnsserv.c.

◆ dnsserv_reject_request()

void dnsserv_reject_request ( entry_connection_t * conn )

If there is a pending request on conn that's waiting for an answer, send back an error and free the request.

Definition at line 289 of file dnsserv.c.

◆ dnsserv_resolved()

void dnsserv_resolved	(	entry_connection_t *	conn,
		int	answer_type,
		size_t	answer_len,
		const char *	answer,
		int	ttl
	)

Tell the dns request waiting for an answer on conn that we have an answer of type answer_type (RESOLVE_TYPE_IPV4/IPV6/ERR), of length answer_len, in answer, with TTL ttl. Doesn't do any caching; that's handled elsewhere.

Definition at line 339 of file dnsserv.c.

◆ evdns_get_orig_address()

static const char* evdns_get_orig_address	(	const struct evdns_server_request *	req,
		int	rtype,
		const char *	addr
	)

static

Look up the original name that corresponds to 'addr' in req. We use this to preserve case in order to facilitate clients using 0x20-hacks to avoid DNS poisoning.

Definition at line 302 of file dnsserv.c.

Referenced by dnsserv_resolved().

◆ evdns_server_callback()

static void evdns_server_callback	(	struct evdns_server_request *	req,
		void *	data_
	)