#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_dns_service.h"

Include dependency graph for gnunet-dns-redirector.c:

Functions
static void	modify_record (const struct GNUNET_DNSPARSER_Record *record)
	Modify the given DNS record. More...

static void	modify_request (void cls, struct GNUNET_DNS_RequestHandle rh, size_t request_length, const char *request)
	Signature of a function that is called whenever the DNS service encounters a DNS request and needs to do something with it. More...

static void	do_disconnect (void *cls)
	Shutdown. More...

static void	run (void cls, char const args, const char cfgfile, const struct GNUNET_CONFIGURATION_Handle *cfg)
	Main function that will be run by the scheduler. More...

int	main (int argc, char const argv)

Variables
static struct GNUNET_DNS_Handle *	handle
	Handle to DNS service. More...

static char *	n4
	New target for A records. More...

static char *	n6
	New target for AAAA records. More...

static int	ret
	Global return value (0 success). More...

static unsigned int	verbosity
	Selected level of verbosity. More...

Function Documentation

◆ modify_record()

static void modify_record ( const struct GNUNET_DNSPARSER_Record * record )

static

Modify the given DNS record.

Parameters

record record to modify

Definition at line 63 of file gnunet-dns-redirector.c.

{
  char buf[INET6_ADDRSTRLEN];
 
  switch (record->type)
  {
  case GNUNET_DNSPARSER_TYPE_A:
    if (record->data.raw.data_len != sizeof(struct in_addr))
      return;
    if (NULL != n4)
    {
      if (verbosity > 1)
        fprintf (stderr,
                 "Changing A record from `%s' to `%s'\n",
                 inet_ntop (AF_INET, record->data.raw.data, buf, sizeof(buf)),
                 n4);
      GNUNET_assert (1 == inet_pton (AF_INET, n4, record->data.raw.data));
    }
    break;
 
  case GNUNET_DNSPARSER_TYPE_AAAA:
    if (record->data.raw.data_len != sizeof(struct in6_addr))
      return;
    if (NULL != n6)
    {
      if (verbosity > 1)
        fprintf (stderr,
                 "Changing AAAA record from `%s' to `%s'\n",
                 inet_ntop (AF_INET6, record->data.raw.data, buf, sizeof(buf)),
                 n6);
      GNUNET_assert (1 == inet_pton (AF_INET6, n6, record->data.raw.data));
    }
    break;
 
  case GNUNET_DNSPARSER_TYPE_NS:
  case GNUNET_DNSPARSER_TYPE_CNAME:
  case GNUNET_DNSPARSER_TYPE_PTR:
  case GNUNET_DNSPARSER_TYPE_SOA:
  case GNUNET_DNSPARSER_TYPE_MX:
  case GNUNET_DNSPARSER_TYPE_TXT:
    break;
 
  default:
    break;
  }
}

References GNUNET_assert, GNUNET_DNSPARSER_TYPE_A, GNUNET_DNSPARSER_TYPE_AAAA, GNUNET_DNSPARSER_TYPE_CNAME, GNUNET_DNSPARSER_TYPE_MX, GNUNET_DNSPARSER_TYPE_NS, GNUNET_DNSPARSER_TYPE_PTR, GNUNET_DNSPARSER_TYPE_SOA, GNUNET_DNSPARSER_TYPE_TXT, n4, n6, record(), and verbosity.

Referenced by modify_request().

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◆ modify_request()

static void modify_request	(	void *	cls,
		struct GNUNET_DNS_RequestHandle *	rh,
		size_t	request_length,
		const char *	request
	)

static

Signature of a function that is called whenever the DNS service encounters a DNS request and needs to do something with it.

The function has then the chance to generate or modify the response by calling one of the three "GNUNET_DNS_request_*" continuations.

When a request is intercepted, this function is called first to give the client a chance to do the complete address resolution; "rdata" will be NULL for this first call for a DNS request, unless some other client has already filled in a response.

If multiple clients exist, all of them are called before the global DNS. The global DNS is only called if all of the clients' functions call GNUNET_DNS_request_forward. Functions that call GNUNET_DNS_request_forward will be called again before a final response is returned to the application. If any of the clients' functions call GNUNET_DNS_request_drop, the response is dropped.

Parameters

cls	closure
rh	request handle to user for reply
request_length	number of bytes in request
request	udp payload of the DNS request

Definition at line 135 of file gnunet-dns-redirector.c.

{
  struct GNUNET_DNSPARSER_Packet *p;
  unsigned int i;
  char *buf;
  size_t len;
  int ret;
 
  p = GNUNET_DNSPARSER_parse (request, request_length);
  if (NULL == p)
  {
    fprintf (stderr, "Received malformed DNS packet, leaving it untouched\n");
    GNUNET_DNS_request_forward (rh);
    return;
  }
  for (i = 0; i < p->num_answers; i++)
    modify_record (&p->answers[i]);
  buf = NULL;
  ret = GNUNET_DNSPARSER_pack (p, 1024, &buf, &len);
  GNUNET_DNSPARSER_free_packet (p);
  if (GNUNET_OK != ret)
  {
    if (GNUNET_NO == ret)
      fprintf (stderr,
               "Modified DNS response did not fit, keeping old response\n");
    else
      GNUNET_break (0);  /* our modifications should have been sane! */
    GNUNET_DNS_request_forward (rh);
  }
  else
  {
    if (verbosity > 0)
      fprintf (stdout,
               "Injecting modified DNS response\n");
    GNUNET_DNS_request_answer (rh, len, buf);
  }
  GNUNET_free (buf);
}

References GNUNET_break, GNUNET_DNS_request_answer(), GNUNET_DNS_request_forward(), GNUNET_DNSPARSER_free_packet(), GNUNET_DNSPARSER_pack(), GNUNET_DNSPARSER_parse(), GNUNET_free, GNUNET_NO, GNUNET_OK, modify_record(), p, request, ret, and verbosity.

Referenced by run().

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◆ do_disconnect()

static void do_disconnect ( void * cls )

static

Shutdown.

Definition at line 182 of file gnunet-dns-redirector.c.

{
  if (NULL != handle)
  {
    GNUNET_DNS_disconnect (handle);
    handle = NULL;
  }
}

References GNUNET_DNS_disconnect(), and handle.

Referenced by run().

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◆ run()

static void run	(	void *	cls,
		char const	args,
		const char *	cfgfile,
		const struct GNUNET_CONFIGURATION_Handle *	cfg
	)

static

Main function that will be run by the scheduler.

Parameters

cls	closure
args	remaining command-line arguments
cfgfile	name of the configuration file used (for saving, can be NULL!)
cfg	configuration

Definition at line 201 of file gnunet-dns-redirector.c.

{
  struct in_addr i4;
  struct in6_addr i6;
 
  if ((n4 != NULL) &&
      (1 != inet_pton (AF_INET, n4, &i4)))
  {
    fprintf (stderr,
             "`%s' is nto a valid IPv4 address!\n",
             n4);
    return;
  }
  if ((n6 != NULL) &&
      (1 != inet_pton (AF_INET6, n6, &i6)))
  {
    fprintf (stderr,
             "`%s' is nto a valid IPv6 address!\n",
             n6);
    return;
  }
 
  handle =
    GNUNET_DNS_connect (cfg,
                        GNUNET_DNS_FLAG_POST_RESOLUTION,
                        &modify_request,
                        NULL);
  GNUNET_SCHEDULER_add_shutdown (&do_disconnect, NULL);
}

References cfg, do_disconnect(), GNUNET_DNS_connect(), GNUNET_DNS_FLAG_POST_RESOLUTION, GNUNET_SCHEDULER_add_shutdown(), handle, modify_request(), n4, and n6.

Referenced by main().

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◆ main()

int main	(	int	argc,
		char const	argv
	)

Definition at line 234 of file gnunet-dns-redirector.c.

{
  struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_option_string ('4',
                                 "ipv4",
                                 "IPV4",
                                 gettext_noop ("set A records"),
                                 &n4),
 
    GNUNET_GETOPT_option_string ('6',
                                 "ipv4",
                                 "IPV6",
                                 gettext_noop ("set AAAA records"),
                                 &n6),
 
    GNUNET_GETOPT_option_verbose (&verbosity),
    GNUNET_GETOPT_OPTION_END
  };
 
  if (GNUNET_OK != GNUNET_STRINGS_get_utf8_args (argc, argv, &argc, &argv))
    return 2;
 
  ret = (GNUNET_OK ==
         GNUNET_PROGRAM_run (argc, argv, "gnunet-dns-redirector",
                             gettext_noop
                               ("Change DNS replies to point elsewhere."),
                             options,
                             &run, NULL)) ? ret : 1;
  GNUNET_free_nz ((void *) argv);
  return ret;
}