Re: function that resolves IP addresses

[Dennis Jenkins <dennis.jenkins@xxxxxxxxxxxxx>]

--- "Joshua D. Drake" <jd@xxxxxxxxxxxxxxxxx> wrote:
It is not fully debugged, but this is what I wrote a
few months ago for sh*ts and grins.

/* djenkins, 2005-7-22

	Implements poor-man's reverse DNS lookup tool for use
in
	Postgresql SQL functions.

CREATE FUNCTION reverse_dns_lookup(text) RETURNS text
     AS 'dns_tools.so', 'reverse_dns_lookup'
     LANGUAGE C STRICT;

CREATE FUNCTION forward_dns_lookup(text) RETURNS text
     AS 'dns_tools.so', 'forward_dns_lookup'
     LANGUAGE C STRICT;
*/

#include "postgres.h"
#include <string.h>
#include "fmgr.h"
#include <stdlib.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <syslog.h>

PG_FUNCTION_INFO_V1(forward_dns_lookup);

Datum 	forward_dns_lookup(PG_FUNCTION_ARGS)
{
	text     *t = PG_GETARG_TEXT_P(0);
	struct hostent *he = NULL;
	int ret_len = 0;
	text	*ret_text = NULL;
	char *in_str = VARDATA(t);
	int in_len = VARSIZE(t) - VARHDRSZ;
	char temp[256];

	if (!in_str || (in_len > sizeof(temp)-1))
	{
		PG_RETURN_NULL();
	}

	strncpy(temp, in_str, in_len);
	temp[in_len] = 0;
	he = gethostbyname(temp);
	if (!he)
	{
		PG_RETURN_NULL();
	}

	strncpy(temp, inet_ntoa(*((struct in_addr
*)he->h_addr)), sizeof(temp));
	ret_len = strlen(temp);

//	syslog(LOG_DEBUG, "'%s'[%d] = '%s'[%d]\n", in_str,
strlen(in_str), temp, ret_len);

	ret_text = (text*)palloc(ret_len + VARHDRSZ);
	VARATT_SIZEP(ret_text) = ret_len + VARHDRSZ;
	memcpy(VARDATA(ret_text), temp, ret_len);

	PG_RETURN_TEXT_P(ret_text);
}

PG_FUNCTION_INFO_V1(reverse_dns_lookup);

Datum 	reverse_dns_lookup(PG_FUNCTION_ARGS)
{
	text     *t = PG_GETARG_TEXT_P(0);
	struct in_addr in;
	struct hostent *he = NULL;
	unsigned long *l = (unsigned long*)((void*)&in);
	int ret_len = 0;
	text	*ret_text = NULL;
	char *in_str = VARDATA(t);
	int in_len = VARSIZE(t) - VARHDRSZ;
	char temp[16];

	if (!in_str || (in_len > sizeof(temp)-1))
	{
		PG_RETURN_NULL();
	}

	memcpy(temp, in_str, in_len);
	temp[in_len] = 0;

	// First, convert the string to IPV4 'long'
	memset(&in, 0, sizeof(in));
	if (!inet_aton(temp, &in))
	{
//		syslog(LOG_DEBUG, "inet_aton('%s'[%d]) failed: %d
{%08lx}", in_str, strlen(in_str), errno, *l);
		PG_RETURN_NULL();
	}

	he = gethostbyaddr((char*)l, 4, AF_INET);
	if (!he)
	{
//		syslog(LOG_DEBUG, "gethostbyaddr('%s') failed:
%d", in_str, errno);
		PG_RETURN_NULL();
	}

	// return string is in 'he->h_name'
	ret_len = strlen(he->h_name);
	ret_text = palloc(ret_len + VARHDRSZ);
	VARATT_SIZEP(ret_text) = ret_len + VARHDRSZ;
	memcpy(VARDATA(ret_text), he->h_name, ret_len);

	PG_RETURN_TEXT_P(ret_text);
}



Dennis Jenkins

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