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/* -*- c-file-style: "java"; indent-tabs-mode: nil; tab-width: 4; fill-column: 78 -*-
*
* Copyright 2005 Google Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* 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, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*/
/* don't blame me, I was in a hurry */
#include <config.h>
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/poll.h>
#include <sys/time.h>
#include "rslave.h"
/*--------------------------------------------------------------------------
Class to provide asynchronous DNS lookup.
To use, first call rslave_init() very early in your program to fork the
dns slave processes.
Then call rslave_write() any time you need a DNS name resolved
and rslave_read() to retrieve the next result. Order of lookup requests
is not preserved.
Call rslave_getfd() and select on that fd for readability if you
want to only call rslave_read() once it won't block.
The slaves will shut down when their input file descriptor is closed,
which normally happens when your program exits.
--------------------------------------------------------------------------*/
int rslave_getfd_fromSlaves(struct rslave_s *rslave)
{
return rslave->pipeFromSlaves[0];
}
int rslave_getfd_toSlaves(struct rslave_s *rslave)
{
return rslave->pipeToSlaves[1];
}
void rslave_request_init(struct rslave_request_s *buf, const char *hostname, int id)
{
memset(buf, 0, sizeof(*buf));
strncpy(buf->hname, hostname, rslave_HOSTLEN);
buf->id = id;
}
int rslave_writeRequest(struct rslave_s *rslave, const struct rslave_request_s *req)
{
if (write(rslave->pipeToSlaves[1], req, sizeof(*req)) != sizeof(*req))
return -1;
return 0;
}
int rslave_gethostbyname(struct rslave_s *rslave, const char *hostname, int id)
{
struct rslave_request_s buf;
rslave_request_init(&buf, hostname, id);
return rslave_writeRequest(rslave, &buf);
}
int rslave_readRequest(struct rslave_s *rslave, struct rslave_request_s *req)
{
if (read(rslave->pipeToSlaves[0], req, sizeof(*req)) != sizeof(*req))
return -1;
return 0;
}
int rslave_writeResult(struct rslave_s *rslave, struct rslave_result_s *result)
{
if (write(rslave->pipeFromSlaves[1], result, sizeof(*result)) != sizeof(*result))
return -1;
return 0;
}
int rslave_readResult(struct rslave_s *rslave, struct rslave_result_s *result)
{
if (read(rslave->pipeFromSlaves[0], result, sizeof(*result)) != sizeof(*result))
return -1;
return 0;
}
void be_a_dnsslave(struct rslave_s *rslave);
void be_a_dnsslave(struct rslave_s *rslave)
{
struct rslave_request_s req;
while (rslave_readRequest(rslave, &req) == 0) {
struct rslave_result_s result;
struct hostent *h;
/* fprintf(stderr, "Calling gethostbyname on %s\n", req.hname); */
h = gethostbyname(req.hname);
memset(&result, 0, sizeof(result));
result.id = req.id;
result.err = h_errno;
if (h && (h->h_length == sizeof(result.addr))) {
memcpy(result.addr, h->h_addr_list[0], (unsigned) h->h_length);
result.err = 0;
}
if (rslave_writeResult(rslave, &result))
break;
}
exit(0);
}
/*--------------------------------------------------------------------------
Initialize an rslave_s and fork slave processes.
Returns 0 on success, -1 on error.
--------------------------------------------------------------------------*/
int rslave_init(struct rslave_s *rslave)
{
int err;
int i;
int nslaves = rslave_NSLAVES;
memset(rslave, 0, sizeof(*rslave));
err = pipe(rslave->pipeToSlaves);
if (err == -1)
return -1;
err = pipe(rslave->pipeFromSlaves);
if (err == -1)
return -1;
for (i=0; i<nslaves; i++) {
pid_t childpid;
childpid = fork();
switch (childpid) {
case -1:
return -1;
break;
case 0: /* child */
close(rslave->pipeToSlaves[1]);
close(rslave->pipeFromSlaves[0]);
be_a_dnsslave(rslave);
break;
default: /* parent */
rslave->pids[i] = childpid; /* Save pid so we can kill it later */
break;
}
}
close(rslave->pipeToSlaves[0]);
close(rslave->pipeFromSlaves[1]);
rslave->nslaves = nslaves;
return 0;
}
/* TODO: add rslave_shutdown() that kills all the slaves by iterating through rslave->pids[] */
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