/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2004, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * $Id: hostip.c,v 1.163 2004/10/10 03:32:01 bagder Exp $
 ***************************************************************************/

#include "setup.h"

#include <string.h>
#include <errno.h>

#define _REENTRANT

#if defined( WIN32 ) && !defined( __GNUC__ ) || defined( __MINGW32__ )
#include <malloc.h>
#else
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>     /* required for free() prototypes */
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>     /* for the close() proto */
#endif
#ifdef  VMS
#include <in.h>
#include <inet.h>
#include <stdlib.h>
#endif
#endif

#ifdef HAVE_SETJMP_H
#include <setjmp.h>
#endif

#ifdef WIN32
#include <process.h>
#endif

#if ( defined( NETWARE ) && defined( __NOVELL_LIBC__ ) )
#undef in_addr_t
#define in_addr_t unsigned long
#endif

#include "urldata.h"
#include "sendf.h"
#include "hostip.h"
#include "hash.h"
#include "share.h"
#include "strerror.h"
#include "url.h"
#include "inet_ntop.h"

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>

#if defined( HAVE_INET_NTOA_R ) && !defined( HAVE_INET_NTOA_R_DECL )
#include "inet_ntoa_r.h"
#endif

#include "memory.h"
/* The last #include file should be: */
#include "memdebug.h"

/*
 * hostip.c explained
 * ==================
 *
 * The main COMPILE-TIME DEFINES to keep in mind when reading the host*.c
 * source file are these:
 *
 * CURLRES_IPV6 - this host has getaddrinfo() and family, and thus we use
 * that. The host may not be able to resolve IPv6, but we don't really have to
 * take that into account. Hosts that aren't IPv6-enabled have CURLRES_IPV4
 * defined.
 *
 * CURLRES_ARES - is defined if libcurl is built to use c-ares for
 * asynchronous name resolves. It cannot have ENABLE_IPV6 defined at the same
 * time, as c-ares has no ipv6 support. This can be Windows or *nix.
 *
 * CURLRES_THREADED - is defined if libcurl is built to run under (native)
 * Windows, and then the name resolve will be done in a new thread, and the
 * supported API will be the same as for ares-builds.
 *
 * If any of the two previous are defined, CURLRES_ASYNCH is defined too. If
 * libcurl is not built to use an asynchronous resolver, CURLRES_SYNCH is
 * defined.
 *
 * The host*.c sources files are split up like this:
 *
 * hostip.c   - method-independent resolver functions and utility functions
 * hostasyn.c - functions for asynchronous name resolves
 * hostsyn.c  - functions for synchronous name resolves
 * hostares.c - functions for ares-using name resolves
 * hostthre.c - functions for threaded name resolves
 * hostip4.c  - ipv4-specific functions
 * hostip6.c  - ipv6-specific functions
 *
 * The hostip.h is the united header file for all this. It defines the
 * CURLRES_* defines based on the config*.h and setup.h defines.
 */

/* These two symbols are for the global DNS cache */
static curl_hash hostname_cache;
static int host_cache_initialized;

static void freednsentry( void *freethis );

/*
 * Curl_global_host_cache_init() initializes and sets up a global DNS cache.
 * Global DNS cache is general badness. Do not use. This will be removed in
 * a future version. Use the share interface instead!
 */
void Curl_global_host_cache_init( void ) {
	if ( !host_cache_initialized ) {
		Curl_hash_init( &hostname_cache, 7, freednsentry );
		host_cache_initialized = 1;
	}
}

/*
 * Return a pointer to the global cache
 */
curl_hash *Curl_global_host_cache_get( void ) {
	return &hostname_cache;
}

/*
 * Destroy and cleanup the global DNS cache
 */
void Curl_global_host_cache_dtor( void ) {
	if ( host_cache_initialized ) {
		Curl_hash_clean( &hostname_cache );
		host_cache_initialized = 0;
	}
}

/*
 * Return # of adresses in a Curl_addrinfo struct
 */
int Curl_num_addresses( const Curl_addrinfo *addr ) {
	int i;
	for ( i = 0; addr; addr = addr->ai_next, i++ ) ;
	return i;
}

/*
 * Curl_printable_address() returns a printable version of the 1st address
 * given in the 'ip' argument. The result will be stored in the buf that is
 * bufsize bytes big.
 *
 * If the conversion fails, it returns NULL.
 */
const char *Curl_printable_address( const Curl_addrinfo *ip,
									char *buf, size_t bufsize ) {
	const void *ip4 = &( (const struct sockaddr_in*)ip->ai_addr )->sin_addr;
	int af = ip->ai_family;
#ifdef CURLRES_IPV6
	const void *ip6 = &( (const struct sockaddr_in6*)ip->ai_addr )->sin6_addr;
#else
	const void *ip6 = NULL;
#endif

	return Curl_inet_ntop( af, af == AF_INET ? ip4 : ip6, buf, bufsize );
}

/*
 * Return a hostcache id string for the providing host + port, to be used by
 * the DNS caching.
 */
static char *
create_hostcache_id( char *server, int port ) {
	/* create and return the new allocated entry */
	return aprintf( "%s:%d", server, port );
}

struct hostcache_prune_data {
	int cache_timeout;
	time_t now;
};

/*
 * This function is set as a callback to be called for every entry in the DNS
 * cache when we want to prune old unused entries.
 *
 * Returning non-zero means remove the entry, return 0 to keep it in the
 * cache.
 */
static int
hostcache_timestamp_remove( void *datap, void *hc ) {
	struct hostcache_prune_data *data =
		(struct hostcache_prune_data *) datap;
	struct Curl_dns_entry *c = (struct Curl_dns_entry *) hc;

	if ( ( data->now - c->timestamp < data->cache_timeout ) ||
		 c->inuse ) {
		/* please don't remove */
		return 0;
	}

	/* fine, remove */
	return 1;
}

/*
 * Prune the DNS cache. This assumes that a lock has already been taken.
 */
static void
hostcache_prune( curl_hash *hostcache, int cache_timeout, time_t now ) {
	struct hostcache_prune_data user;

	user.cache_timeout = cache_timeout;
	user.now = now;

	Curl_hash_clean_with_criterium( hostcache,
									(void *) &user,
									hostcache_timestamp_remove );
}

/*
 * Library-wide function for pruning the DNS cache. This function takes and
 * returns the appropriate locks.
 */
void Curl_hostcache_prune( struct SessionHandle *data ) {
	time_t now;

	if ( ( data->set.dns_cache_timeout == -1 ) || !data->hostcache ) {
		/* cache forever means never prune, and NULL hostcache means
		   we can't do it */
		return;
	}

	if ( data->share ) {
		Curl_share_lock( data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE );
	}

	time( &now );

	/* Remove outdated and unused entries from the hostcache */
	hostcache_prune( data->hostcache,
					 data->set.dns_cache_timeout,
					 now );

	if ( data->share ) {
		Curl_share_unlock( data, CURL_LOCK_DATA_DNS );
	}
}

#ifdef HAVE_SIGSETJMP
/* Beware this is a global and unique instance. This is used to store the
   return address that we can jump back to from inside a signal handler. This
   is not thread-safe stuff. */
sigjmp_buf curl_jmpenv;
#endif


/*
 * Curl_cache_addr() stores a 'Curl_addrinfo' struct in the DNS cache.
 *
 * When calling Curl_resolv() has resulted in a response with a returned
 * address, we call this function to store the information in the dns
 * cache etc
 *
 * Returns the Curl_dns_entry entry pointer or NULL if the storage failed.
 */
struct Curl_dns_entry *
Curl_cache_addr( struct SessionHandle *data,
				 Curl_addrinfo *addr,
				 char *hostname,
				 int port ) {
	char *entry_id;
	size_t entry_len;
	struct Curl_dns_entry *dns;
	struct Curl_dns_entry *dns2;
	time_t now;

	/* Create an entry id, based upon the hostname and port */
	entry_id = create_hostcache_id( hostname, port );
	/* If we can't create the entry id, fail */
	if ( !entry_id ) {
		return NULL;
	}
	entry_len = strlen( entry_id );

	/* Create a new cache entry */
	dns = (struct Curl_dns_entry *) malloc( sizeof( struct Curl_dns_entry ) );
	if ( !dns ) {
		free( entry_id );
		return NULL;
	}

	dns->inuse = 0; /* init to not used */
	dns->addr = addr; /* this is the address(es) */

	/* Store the resolved data in our DNS cache. This function may return a
	   pointer to an existing struct already present in the hash, and it may
	   return the same argument we pass in. Make no assumptions. */
	dns2 = Curl_hash_add( data->hostcache, entry_id, entry_len + 1, (void *)dns );
	if ( !dns2 ) {
		/* Major badness, run away. */
		free( dns );
		free( entry_id );
		return NULL;
	}
	time( &now );
	dns = dns2;

	dns->timestamp = now; /* used now */
	dns->inuse++;       /* mark entry as in-use */

	/* free the allocated entry_id again */
	free( entry_id );

	return dns;
}

/*
 * Curl_resolv() is the main name resolve function within libcurl. It resolves
 * a name and returns a pointer to the entry in the 'entry' argument (if one
 * is provided). This function might return immediately if we're using asynch
 * resolves. See the return codes.
 *
 * The cache entry we return will get its 'inuse' counter increased when this
 * function is used. You MUST call Curl_resolv_unlock() later (when you're
 * done using this struct) to decrease the counter again.
 *
 * Return codes:
 *
 * CURLRESOLV_ERROR   (-1) = error, no pointer
 * CURLRESOLV_RESOLVED (0) = OK, pointer provided
 * CURLRESOLV_PENDING  (1) = waiting for response, no pointer
 */

int Curl_resolv( struct connectdata *conn,
				 char *hostname,
				 int port,
				 struct Curl_dns_entry **entry ) {
	char *entry_id = NULL;
	struct Curl_dns_entry *dns = NULL;
	size_t entry_len;
	int wait;
	struct SessionHandle *data = conn->data;
	CURLcode result;
	int rc;
	*entry = NULL;

#ifdef HAVE_SIGSETJMP
	/* this allows us to time-out from the name resolver, as the timeout
	   will generate a signal and we will siglongjmp() from that here */
	if ( !data->set.no_signal && sigsetjmp( curl_jmpenv, 1 ) ) {
		/* this is coming from a siglongjmp() */
		failf( data, "name lookup timed out" );
		return CURLRESOLV_ERROR;
	}
#endif

	/* Create an entry id, based upon the hostname and port */
	entry_id = create_hostcache_id( hostname, port );
	/* If we can't create the entry id, fail */
	if ( !entry_id ) {
		return CURLRESOLV_ERROR;
	}

	entry_len = strlen( entry_id );

	if ( data->share ) {
		Curl_share_lock( data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE );
	}

	/* See if its already in our dns cache */
	dns = Curl_hash_pick( data->hostcache, entry_id, entry_len + 1 );

	if ( data->share ) {
		Curl_share_unlock( data, CURL_LOCK_DATA_DNS );
	}

	/* free the allocated entry_id again */
	free( entry_id );

	rc = CURLRESOLV_ERROR; /* default to failure */

	if ( !dns ) {
		/* The entry was not in the cache. Resolve it to IP address */

		Curl_addrinfo *addr;

		/* Check what IP specifics the app has requested and if we can provide it.
		 * If not, bail out. */
		if ( !Curl_ipvalid( data ) ) {
			return CURLRESOLV_ERROR;
		}

		/* If Curl_getaddrinfo() returns NULL, 'wait' might be set to a non-zero
		   value indicating that we need to wait for the response to the resolve
		   call */
		addr = Curl_getaddrinfo( conn, hostname, port, &wait );

		if ( !addr ) {
			if ( wait ) {
				/* the response to our resolve call will come asynchronously at
				   a later time, good or bad */
				/* First, check that we haven't received the info by now */
				result = Curl_is_resolved( conn, &dns );
				if ( result ) { /* error detected */
					return CURLRESOLV_ERROR;
				}
				if ( dns ) {
					rc = CURLRESOLV_RESOLVED; /* pointer provided */
				} else {
					rc = CURLRESOLV_PENDING; /* no info yet */
				}
			}
		} else {
			if ( data->share ) {
				Curl_share_lock( data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE );
			}

			/* we got a response, store it in the cache */
			dns = Curl_cache_addr( data, addr, hostname, port );

			if ( data->share ) {
				Curl_share_unlock( data, CURL_LOCK_DATA_DNS );
			}

			if ( !dns ) {
				/* returned failure, bail out nicely */
				Curl_freeaddrinfo( addr );
			} else {
				rc = CURLRESOLV_RESOLVED;
			}
		}
	} else {
		if ( data->share ) {
			Curl_share_lock( data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE );
		}
		dns->inuse++; /* we use it! */
		if ( data->share ) {
			Curl_share_unlock( data, CURL_LOCK_DATA_DNS );
		}
		rc = CURLRESOLV_RESOLVED;
	}

	*entry = dns;

	return rc;
}

/*
 * Curl_resolv_unlock() unlocks the given cached DNS entry. When this has been
 * made, the struct may be destroyed due to pruning. It is important that only
 * one unlock is made for each Curl_resolv() call.
 */
void Curl_resolv_unlock( struct SessionHandle *data, struct Curl_dns_entry *dns ) {
	curlassert( dns && ( dns->inuse > 0 ) );

	if ( data->share ) {
		Curl_share_lock( data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE );
	}

	dns->inuse--;

	if ( data->share ) {
		Curl_share_unlock( data, CURL_LOCK_DATA_DNS );
	}
}

/*
 * File-internal: free a cache dns entry.
 */
static void freednsentry( void *freethis ) {
	struct Curl_dns_entry *p = (struct Curl_dns_entry *) freethis;

	Curl_freeaddrinfo( p->addr );

	free( p );
}

/*
 * Curl_mk_dnscache() creates a new DNS cache and returns the handle for it.
 */
curl_hash *Curl_mk_dnscache( void ) {
	return Curl_hash_alloc( 7, freednsentry );
}

#ifdef CURLRES_ADDRINFO_COPY

/* align on even 64bit boundaries */
#define MEMALIGN( x ) ( ( x ) + ( 8 - ( ( (unsigned long)( x ) )& 0x7 ) ) )

/*
 * Curl_addrinfo_copy() performs a "deep" copy of a hostent into a buffer and
 * returns a pointer to the malloc()ed copy. You need to call free() on the
 * returned buffer when you're done with it.
 */
Curl_addrinfo *Curl_addrinfo_copy( void *org, int port ) {
	struct hostent *orig = org;

	return Curl_he2ai( orig, port );
}
#endif /* CURLRES_ADDRINFO_COPY */
