Re: function that resolves IP addresses

--- "Joshua D. Drake" <jd@commandprompt.com> 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