curl/lib/hostip4.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2018, 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 https://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.
 *
 ***************************************************************************/

#include "curl_setup.h"

/***********************************************************************
 * Only for plain IPv4 builds
 **********************************************************************/
#ifdef CURLRES_IPV4 /* plain IPv4 code coming up */

#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 __VMS
#include <in.h>
#include <inet.h>
#endif

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

#include "urldata.h"
#include "sendf.h"
#include "hostip.h"
#include "hash.h"
#include "share.h"
#include "strerror.h"
#include "url.h"
#include "inet_pton.h"
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"

/*
 * Curl_ipvalid() checks what CURL_IPRESOLVE_* requirements that might've
 * been set and returns TRUE if they are OK.
 */
bool Curl_ipvalid(struct connectdata *conn)
{
  if(conn->ip_version == CURL_IPRESOLVE_V6)
    /* An IPv6 address was requested and we can't get/use one */
    return FALSE;

  return TRUE; /* OK, proceed */
}

#ifdef CURLRES_SYNCH

/*
 * Curl_getaddrinfo() - the IPv4 synchronous version.
 *
 * The original code to this function was from the Dancer source code, written
 * by Bjorn Reese, it has since been patched and modified considerably.
 *
 * gethostbyname_r() is the thread-safe version of the gethostbyname()
 * function. When we build for plain IPv4, we attempt to use this
 * function. There are _three_ different gethostbyname_r() versions, and we
 * detect which one this platform supports in the configure script and set up
 * the HAVE_GETHOSTBYNAME_R_3, HAVE_GETHOSTBYNAME_R_5 or
 * HAVE_GETHOSTBYNAME_R_6 defines accordingly. Note that HAVE_GETADDRBYNAME
 * has the corresponding rules. This is primarily on *nix. Note that some unix
 * flavours have thread-safe versions of the plain gethostbyname() etc.
 *
 */
Curl_addrinfo *Curl_getaddrinfo(struct connectdata *conn,
                                const char *hostname,
                                int port,
                                int *waitp)
{
  Curl_addrinfo *ai = NULL;

#ifdef CURL_DISABLE_VERBOSE_STRINGS
  (void)conn;
#endif

  *waitp = 0; /* synchronous response only */

  ai = Curl_ipv4_resolve_r(hostname, port);
  if(!ai)
    infof(conn->data, "Curl_ipv4_resolve_r failed for %s\n", hostname);

  return ai;
}
#endif /* CURLRES_SYNCH */
#endif /* CURLRES_IPV4 */

#if defined(CURLRES_IPV4) && !defined(CURLRES_ARES)

/*
 * Curl_ipv4_resolve_r() - ipv4 threadsafe resolver function.
 *
 * This is used for both synchronous and asynchronous resolver builds,
 * implying that only threadsafe code and function calls may be used.
 *
 */
Curl_addrinfo *Curl_ipv4_resolve_r(const char *hostname,
                                   int port)
{
#if !defined(HAVE_GETADDRINFO_THREADSAFE) && defined(HAVE_GETHOSTBYNAME_R_3)
  int res;
#endif
  Curl_addrinfo *ai = NULL;
  struct hostent *h = NULL;
  struct in_addr in;
  struct hostent *buf = NULL;

  if(Curl_inet_pton(AF_INET, hostname, &in) > 0)
    /* This is a dotted IP address 123.123.123.123-style */
    return Curl_ip2addr(AF_INET, &in, hostname, port);

#if defined(HAVE_GETADDRINFO_THREADSAFE)
  else {
    struct addrinfo hints;
    char sbuf[12];
    char *sbufptr = NULL;

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = PF_INET;
    hints.ai_socktype = SOCK_STREAM;
    if(port) {
      msnprintf(sbuf, sizeof(sbuf), "%d", port);
      sbufptr = sbuf;
    }

    (void)Curl_getaddrinfo_ex(hostname, sbufptr, &hints, &ai);

#elif defined(HAVE_GETHOSTBYNAME_R)
  /*
   * gethostbyname_r() is the preferred resolve function for many platforms.
   * Since there are three different versions of it, the following code is
   * somewhat #ifdef-ridden.
   */
  else {
    int h_errnop;

    buf = calloc(1, CURL_HOSTENT_SIZE);
    if(!buf)
      return NULL; /* major failure */
    /*
     * The clearing of the buffer is a workaround for a gethostbyname_r bug in
     * qnx nto and it is also _required_ for some of these functions on some
     * platforms.
     */

#if defined(HAVE_GETHOSTBYNAME_R_5)
    /* Solaris, IRIX and more */
    h = gethostbyname_r(hostname,
                        (struct hostent *)buf,
                        (char *)buf + sizeof(struct hostent),
                        CURL_HOSTENT_SIZE - sizeof(struct hostent),
                        &h_errnop);

    /* If the buffer is too small, it returns NULL and sets errno to
     * ERANGE. The errno is thread safe if this is compiled with
     * -D_REENTRANT as then the 'errno' variable is a macro defined to get
     * used properly for threads.
     */

    if(h) {
      ;
    }
    else
#elif defined(HAVE_GETHOSTBYNAME_R_6)
    /* Linux */

    (void)gethostbyname_r(hostname,
                        (struct hostent *)buf,
                        (char *)buf + sizeof(struct hostent),
                        CURL_HOSTENT_SIZE - sizeof(struct hostent),
                        &h, /* DIFFERENCE */
                        &h_errnop);
    /* Redhat 8, using glibc 2.2.93 changed the behavior. Now all of a
     * sudden this function returns EAGAIN if the given buffer size is too
     * small. Previous versions are known to return ERANGE for the same
     * problem.
     *
     * This wouldn't be such a big problem if older versions wouldn't
     * sometimes return EAGAIN on a common failure case. Alas, we can't
     * assume that EAGAIN *or* ERANGE means ERANGE for any given version of
     * glibc.
     *
     * For now, we do that and thus we may call the function repeatedly and
     * fail for older glibc versions that return EAGAIN, until we run out of
     * buffer size (step_size grows beyond CURL_HOSTENT_SIZE).
     *
     * If anyone has a better fix, please tell us!
     *
     * -------------------------------------------------------------------
     *
     * On October 23rd 2003, Dan C dug up more details on the mysteries of
     * gethostbyname_r() in glibc:
     *
     * In glibc 2.2.5 the interface is different (this has also been
     * discovered in glibc 2.1.1-6 as shipped by Redhat 6). What I can't
     * explain, is that tests performed on glibc 2.2.4-34 and 2.2.4-32
     * (shipped/upgraded by Redhat 7.2) don't show this behavior!
     *
     * In this "buggy" version, the return code is -1 on error and 'errno'
     * is set to the ERANGE or EAGAIN code. Note that 'errno' is not a
     * thread-safe variable.
     */

    if(!h) /* failure */
#elif defined(HAVE_GETHOSTBYNAME_R_3)
    /* AIX, Digital Unix/Tru64, HPUX 10, more? */

    /* For AIX 4.3 or later, we don't use gethostbyname_r() at all, because of
     * the plain fact that it does not return unique full buffers on each
     * call, but instead several of the pointers in the hostent structs will
     * point to the same actual data! This have the unfortunate down-side that
     * our caching system breaks down horribly. Luckily for us though, AIX 4.3
     * and more recent versions have a "completely thread-safe"[*] libc where
     * all the data is stored in thread-specific memory areas making calls to
     * the plain old gethostbyname() work fine even for multi-threaded
     * programs.
     *
     * This AIX 4.3 or later detection is all made in the configure script.
     *
     * Troels Walsted Hansen helped us work this out on March 3rd, 2003.
     *
     * [*] = much later we've found out that it isn't at all "completely
     * thread-safe", but at least the gethostbyname() function is.
     */

    if(CURL_HOSTENT_SIZE >=
       (sizeof(struct hostent) + sizeof(struct hostent_data))) {

      /* August 22nd, 2000: Albert Chin-A-Young brought an updated version
       * that should work! September 20: Richard Prescott worked on the buffer
       * size dilemma.
       */

      res = gethostbyname_r(hostname,
                            (struct hostent *)buf,
                            (struct hostent_data *)((char *)buf +
                                                    sizeof(struct hostent)));
      h_errnop = SOCKERRNO; /* we don't deal with this, but set it anyway */
    }
    else
      res = -1; /* failure, too smallish buffer size */

    if(!res) { /* success */

      h = buf; /* result expected in h */

      /* This is the worst kind of the different gethostbyname_r() interfaces.
       * Since we don't know how big buffer this particular lookup required,
       * we can't realloc down the huge alloc without doing closer analysis of
       * the returned data. Thus, we always use CURL_HOSTENT_SIZE for every
       * name lookup. Fixing this would require an extra malloc() and then
       * calling Curl_addrinfo_copy() that subsequent realloc()s down the new
       * memory area to the actually used amount.
       */
    }
    else
#endif /* HAVE_...BYNAME_R_5 || HAVE_...BYNAME_R_6 || HAVE_...BYNAME_R_3 */
    {
      h = NULL; /* set return code to NULL */
      free(buf);
    }
#else /* HAVE_GETADDRINFO_THREADSAFE || HAVE_GETHOSTBYNAME_R */
    /*
     * Here is code for platforms that don't have a thread safe
     * getaddrinfo() nor gethostbyname_r() function or for which
     * gethostbyname() is the preferred one.
     */
  else {
    h = gethostbyname((void *)hostname);
#endif /* HAVE_GETADDRINFO_THREADSAFE || HAVE_GETHOSTBYNAME_R */
  }

  if(h) {
    ai = Curl_he2ai(h, port);

    if(buf) /* used a *_r() function */
      free(buf);
  }

  return ai;
}
#endif /* defined(CURLRES_IPV4) && !defined(CURLRES_ARES) */