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Standalone daemon process to handle async DNS lookup on Unix/Linux.

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hoa.nguyen%intel.com 1999-07-26 21:25:00 +00:00
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commit 2ff37fbe4e
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598
netwerk/dns/daemon/nsDnsAsyncLookup.cpp Normal file
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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* The contents of this file are subject to the Netscape Public License
* Version 1.0 (the "NPL"); you may not use this file except in
* compliance with the NPL. You may obtain a copy of the NPL at
* http://www.mozilla.org/NPL/
*
* Software distributed under the NPL is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
* for the specific language governing rights and limitations under the
* NPL.
*
* The Initial Developer of this code under the NPL is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All Rights
* Reserved.
*/
/*
* nsDnsAsyncLookup.cpp --- standalone lightweight process to handle
* asyncrhonous dns lookup on Unix.
*/
/* Compile-time options:
* -DGETHOSTBYNAME_DELAY=N
* to insert an artificial delay of N seconds before each
* call to gethostbyname (in order to simulate DNS lossage.)
*
* -DNO_SOCKS_NS_KLUDGE
* Set this to *disable* the $SOCKS_NS kludge. Otherwise,
* that environment variable will be consulted for use as an
* alternate DNS root. It's historical; don't ask me...
*/
#if defined(XP_UNIX) && defined(UNIX_ASYNC_DNS)
#include <sys/types.h>
#include <sys/wait.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <signal.h>
#include <assert.h>
#include <sys/un.h>
#include "unix_dns.h"
#if defined(AIX)
#include <sys/select.h> // for fd_set
#endif
#if !defined(NO_SOCKS_NS_KLUDGE)
#include <arpa/inet.h> // for in_addr (from nameser.h)
#include <arpa/nameser.h> // for MAXDNAME (from resolv.h)
#include <resolv.h> // for res_init() and _res
#endif
#if !defined(__irix)
// looks like Irix is the only one that has getdtablehi()?
#define getdtablehi() getdtablesize()
// If you find a system doesn't have getdtablesize try #define getdtablesize
// to FD_SETSIZE. And if you encounter a system that doesn't even have
// FD_SETSIZE, just grab your ankles and use 255.
#endif
#define BACKLOG 20 // maximum # of pending connections
#define ASSERT(x) assert(x)
static int listen_fd = -1;
///////////////////////////////////////////////////////////////////////////
// Name: dnsSocksKludge
//
// Description: Gross historical kludge.
// If the environment variable $SOCKS_NS is defined, stomp
// on the host that the DNS code uses for host lookup to be
// a specific ip address.
//
static void
dnsSocksKludge(void)
{
#ifndef NO_SOCKS_NS_KLUDGE
char *ns = getenv("SOCKS_NS");
if (ns && *ns)
{
// Gross hack added to Gross historical kludge - need to
// initialize resolv.h structure first with low-cost call
// to gethostbyname() before hacking _res. Subsequent call
// to gethostbyname() will then pick up $SOCKS_NS address.
//
gethostbyname("localhost");
res_init();
// _res is defined in resolv.h
_res.nsaddr_list[0].sin_addr.s_addr = inet_addr(ns);
_res.nscount = 1;
}
#endif /* !NO_SOCKS_NS_KLUDGE */
}
///////////////////////////////////////////////////////////////////////////
// Name: mySignalHandler
//
// Description: Signal handler. Close down the socket and exit.
//
static void
mySignalHandler (int sig)
{
// close down the socket.
close (listen_fd);
unlink (DNS_SOCK_NAME); //just in case close doesn't remove this
exit (0);
}
//////////////////////////////////////////////////////////////////////////
// Name: displaySysErr
//
// Description: Display system error.
//
static void
displaySysErr(char *name) {
perror ((const char *)name);
exit (1);
}
/////////////////////////////////////////////////////////////////////////
//
// The following data structure is used to hold information about a
// pending lookup request.
typedef struct dns_lookup {
long id; // id to identify this entry
pid_t pid; // process id of the helper process
int fd; // file descriptor used to get result from
int accept_fd; // file descriptor used to send hostent back
char *name; // name to lookup
struct dns_lookup *next; // pointer to the next entry
} dns_lookup;
static dns_lookup *dns_lookup_queue = 0;
////////////////////////////////////////////////////////////////////////
// Name: getNextDnsEntry
//
// Description: Return the idx entry to the caller. Bump the index up
// by 1 before the return. Similiar to an iterator.
//
static dns_lookup*
getNextDnsEntry (int *idx)
{
dns_lookup *obj = dns_lookup_queue;
if (*idx < 0)
return 0;
for (int i = 1; i < *idx; i++)
{
obj = obj->next;
if (!obj)
return 0;
}
*idx += 1;
return obj;
}
////////////////////////////////////////////////////////////////////////
// Name: addToDnsQueue
//
// Description: Add a lookup entry to the queue.
//
static void
addToDnsQueue (dns_lookup* obj)
{
dns_lookup* entry;
obj->next = 0;
if (!dns_lookup_queue)
{
dns_lookup_queue = obj;
return;
}
entry = dns_lookup_queue;
while (entry->next)
entry = entry->next;
entry->next = obj;
}
//////////////////////////////////////////////////////////////////////////
// Name: removeFromDnsQueue
//
// Description: Remove the specified entry from the queue.
//
static void
removeFromDnsQueue (dns_lookup *obj)
{
dns_lookup* entry;
if (!obj || !dns_lookup_queue)
return;
if (obj == dns_lookup_queue)
{
dns_lookup_queue = obj->next;
}
else
{
entry = dns_lookup_queue;
while (obj != entry->next)
entry = entry->next;
if (!entry || !entry->next)
return;
entry->next = obj->next;
}
if (obj->name)
{
free(obj->name);
obj->name = 0;
}
free (obj);
}
///////////////////////////////////////////////////////////////////////////
// Name: newLookupObject
//
// Description: Create a new lookup object and return a pointer to the
// object to the caller. 0 is returned on error.
//
static dns_lookup*
newLookupObject (const char *name)
{
static int dnsId = 0;
ASSERT (name);
char *str = strdup (name);
if (!str) return 0; // MK_OUT_OF_MEMORY
dns_lookup* obj = (dns_lookup *) malloc (sizeof (struct dns_lookup));
if (!obj)
{
free (str);
return 0;
}
memset( obj, 0, sizeof( struct dns_lookup ) );
obj->id = ++dnsId;
obj->name = str;
obj->fd = -1;
obj->accept_fd = -1;
addToDnsQueue (obj);
return (obj);
}
///////////////////////////////////////////////////////////////////////////
// Name: hostentToBytes
//
// Description: Pack the structure `hostent' into a character buffer.
//
//
static void
hostentToBytes (hostent *h, char *buf, int *size)
{
*size = 0;
int len = strlen (h->h_name);
char *p = buf;
*(int *)p = len; // Encode the length of the name
p += sizeof (int);
if (len > 0)
{
strcpy (p, h->h_name);
p += strlen (h->h_name);
}
int n;
// find out the number of aliases are present. The last entry in
// list is 0.
for (n = 0; h->h_aliases[n]; n++);
*(int *)p = n; // Encode the size of aliases into buf
p += sizeof (int);
int i;
// copy aliases to the buffer.
for (i = 0; i < n; i++)
{
len = strlen (h->h_aliases[i]);
*(int *)p = (int) len;
p += sizeof(int);
memcpy (p, h->h_aliases[i], (size_t) len);
p += len;
}
*(int *)p = h->h_addrtype; // Encode the member h_addrtype
p += sizeof (int);
*(int *)p = h->h_length; // Encode the member h_length
p += sizeof (int);
// find out the number of addresses in h_addr_list list.
for (n = 0; h->h_addr_list[n]; n++);
*(int *)p = n; // Encode the size of aliases into buf
p += sizeof (int);
// copy the address list into the buffer.
for (i = 0; i < n; i++)
{
len = strlen (h->h_addr_list[i]);
*(int *)p = (int) len;
p += sizeof(int);
memcpy (p, h->h_addr_list[i], (size_t) len);
p += len;
}
*size = p - buf;
}
////////////////////////////////////////////////////////////////////////
// Name: cancelLookup
//
// Description: Cancel an existing lookup request. Locate the right
// child helper process and kill it.
//
static void
cancelLookup (int id)
{
dns_lookup *obj = dns_lookup_queue;
while (obj)
{
if (id == obj->id)
break;
obj = obj->next;
}
if (obj && obj->pid)
{
kill (obj->pid, SIGQUIT);
pid_t pid2 = waitpid (obj->pid, 0, 0);
ASSERT ((obj->pid == pid2));
removeFromDnsQueue (obj);
}
}
//////////////////////////////////////////////////////////////////////////
// Name: blockingGethostbyname
//
// Description: Calls the blocking gethostbyname to perform the lookup.
// When done, pack the hostent struct into a character
// buffer and sent it back to the parent process via pipe.
//
static void
blockingGethostbyname (const char *name, int out_fd)
{
static int firstTime = true;
if (firstTime)
{
firstTime = 0;
dnsSocksKludge();
}
#ifdef GETHOSTBYNAME_DELAY
int i = GETHOSTBYNAME_DELAY;
sleep(i);
#endif // GETHOSTBYNAME_DELAY
int size = 0;
char buf[BUFSIZ];
struct hostent *h = gethostbyname(name);
if (h)
{
*(int *)&buf[0] = (int) DNS_STATUS_GETHOSTBYNAME_OK;
char *p = buf + sizeof (int);
hostentToBytes (h, p, &size);
size = size + sizeof (int);
}
else
{
*(int *)&buf[0] = (int) DNS_STATUS_GETHOSTBYNAME_FAILED;
size = sizeof (int);
}
// Send response back to parent.
write(out_fd, buf, size);
}
//////////////////////////////////////////////////////////////////////////
// Name: spawnHelperProcess
//
// Description: Spawns a child helper process to do the standard Unix
// blocking dns lookup.
//
dns_lookup*
spawnHelperProcess (const char *name)
{
pid_t forked;
int fds[2];
dns_lookup* obj = newLookupObject (name);
if (!obj) return 0;
if (pipe(fds))
{
fprintf (stderr, "Can't make pipe\n");
return 0;
}
obj->fd = fds[0];
switch (forked = fork())
{
case -1:
fprintf (stderr, "Can't fork\n");
removeFromDnsQueue (obj);
break;
case 0: /* This is the forked process. */
close (fds[0]);
blockingGethostbyname (name, fds[1]);
/* Close the file and exit the process. */
close (fds[1]);
exit (0);
break;
default:
close (fds[1]);
obj->pid = forked;
return obj;
break;
}
// shouldn't get here
ASSERT (0);
return 0;
}
////////////////////////////////////////////////////////////////////////////
int main (int argc, char **argv)
{
signal (SIGINT, mySignalHandler); // trap SIGINT
// TODO: more signals need to be trapped. Will do...
// Create a socket of type PF_UNIX to listen for dns lookup requests
listen_fd = socket (PF_UNIX, SOCK_STREAM, 0);
if (listen_fd == -1)
displaySysErr (argv[0]);
struct saddr_un {
sa_family_t sun_family;
char sun_path[108];
} unix_addr;
unix_addr.sun_family = AF_UNIX;
strcpy (unix_addr.sun_path, DNS_SOCK_NAME);
if (bind (listen_fd, (struct sockaddr*)&unix_addr, sizeof(unix_addr)) == -1)
displaySysErr (argv[0]);
if (listen (listen_fd, BACKLOG) == -1)
displaySysErr (argv[0]);
int accept_fd = -1;
/////////////////////////////////////////////////////////////////////////
// Loop to process incoming DNS lookup/cancel reqeusts. When lookup is
// is completed by the helper child process, a "hostent" structure will
// be sent back to the client.
/////////////////////////////////////////////////////////////////////////
while (1) {
fd_set readfds;
FD_ZERO (&readfds);
FD_SET (listen_fd, &readfds);
if (accept_fd > 0)
FD_SET (accept_fd, &readfds);
int idx = 0;
dns_lookup* obj;
while ((obj = getNextDnsEntry (&idx)))
FD_SET(obj->fd, &readfds);
// Select will return if any one of the fd is ready for read.
// Meaning either a request has arrived from Mozilla client or
// a helper process has sent the lookup result back to us.
int n = select (getdtablehi(), &readfds, 0, 0, 0);
if (n == -1)
continue;
if (FD_ISSET (listen_fd, &readfds))
{
struct sockaddr_in from;
int fromlen = sizeof (from);
accept_fd = accept (listen_fd, (struct sockaddr *)&from,
(socklen_t *)&fromlen);
if (accept_fd == -1)
displaySysErr (argv[0]);
}
int r;
char buffer[BUFSIZ];
if (accept_fd > 0 && FD_ISSET (accept_fd, &readfds))
{
// Read the request from client.
r = recv (accept_fd, buffer, sizeof(buffer), 0);
if (r > 0 && r < (int) sizeof(buffer)) {
buffer[r] = 0;
if (!(strncmp (buffer, "shutdown:", 9)))
break;
char *name = index (buffer, ' ');
if (name && *name)
name++;
if (!name)
continue;
if (!strncmp (buffer, "kill:", 5))
{
// On kill, the name is really an id number
int id = (int) (*(int *)name);
cancelLookup (id);
close (accept_fd);
accept_fd = -1;
}
else if (!strncmp (buffer, "lookup:", 7))
{
obj = spawnHelperProcess (name);
obj->accept_fd = accept_fd;
char hId[5];
*(int *)&hId[0] = (int) obj->id;
if (!obj)
fprintf (stderr, "spawn Error\n");
else
{
send (obj->accept_fd, hId, sizeof (int), 0);
}
}
}
accept_fd = -1;
}
idx = 0;
while ((obj = getNextDnsEntry (&idx)))
{
// Check to see if any of the helper process is done with
// the lookup operation.
if (FD_ISSET(obj->fd, &readfds))
{
r = read (obj->fd, buffer, BUFSIZ);
int status;
wait(&status);
close (obj->fd);
// Send the reponse "hostent" back to client.
send (obj->accept_fd, buffer, r, 0);
close (obj->accept_fd);
removeFromDnsQueue (obj);
}
}
}
close (listen_fd);
unlink (DNS_SOCK_NAME);
exit (0);
}
#endif // XP_UNIX && UNIX_ASYNC_DNS

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netwerk/dns/daemon/unix_dns.h Normal file
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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* The contents of this file are subject to the Netscape Public License
* Version 1.0 (the "NPL"); you may not use this file except in
* compliance with the NPL. You may obtain a copy of the NPL at
* http://www.mozilla.org/NPL/
*
* Software distributed under the NPL is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
* for the specific language governing rights and limitations under the
* NPL.
*
* The Initial Developer of this code under the NPL is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All Rights
* Reserved.
*/
#ifndef __UNIX_DNS_H__
#define __UNIX_DNS_H__
#define DNS_SOCK_NAME "/tmp/netscape_dns_lookup" // Name of unix socket
/* The internal status codes that are used; these follow the basic
SMTP/NNTP model of three-digit codes.
*/
#define DNS_STATUS_GETHOSTBYNAME_OK 101
#define DNS_STATUS_LOOKUP_OK 102
#define DNS_STATUS_KILLED_OK 103
#define DNS_STATUS_LOOKUP_STARTED 201
#define DNS_STATUS_GETHOSTBYNAME_FAILED 501
#define DNS_STATUS_LOOKUP_FAILED 502
#define DNS_STATUS_LOOKUP_NOT_STARTED 503
#define DNS_STATUS_KILL_FAILED 504
#define DNS_STATUS_UNIMPLEMENTED 601
#define DNS_STATUS_INTERNAL_ERROR 602
#endif /* __UNIX_DNS_H__ */