The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/libkern/inet_ntop.c

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    1 /*
    2  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
    3  * Copyright (c) 1996-1999 by Internet Software Consortium.
    4  *
    5  * Permission to use, copy, modify, and distribute this software for any
    6  * purpose with or without fee is hereby granted, provided that the above
    7  * copyright notice and this permission notice appear in all copies.
    8  *
    9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
   10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   11  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
   12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
   15  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   16  */
   17 
   18 #if defined(LIBC_SCCS) && !defined(lint)
   19 static const char rcsid[] = "$Id: inet_ntop.c,v 1.3.18.2 2005/11/03 23:02:22 marka Exp $";
   20 #endif /* LIBC_SCCS and not lint */
   21 #include <sys/cdefs.h>
   22 __FBSDID("$FreeBSD: releng/10.0/sys/libkern/inet_ntop.c 213103 2010-09-24 15:01:45Z attilio $");
   23 
   24 #include <sys/param.h>
   25 #include <sys/socket.h>
   26 #include <sys/systm.h>
   27 
   28 #include <netinet/in.h>
   29 
   30 /*%
   31  * WARNING: Don't even consider trying to compile this on a system where
   32  * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
   33  */
   34 
   35 static char     *inet_ntop4(const u_char *src, char *dst, socklen_t size);
   36 static char     *inet_ntop6(const u_char *src, char *dst, socklen_t size);
   37 
   38 /* char *
   39  * inet_ntop(af, src, dst, size)
   40  *      convert a network format address to presentation format.
   41  * return:
   42  *      pointer to presentation format address (`dst'), or NULL (see errno).
   43  * author:
   44  *      Paul Vixie, 1996.
   45  */
   46 char *
   47 inet_ntop(int af, const void *src, char *dst, socklen_t size)
   48 {
   49         switch (af) {
   50         case AF_INET:
   51                 return (inet_ntop4(src, dst, size));
   52         case AF_INET6:
   53                 return (inet_ntop6(src, dst, size));
   54         default:
   55                 return (NULL);
   56         }
   57         /* NOTREACHED */
   58 }
   59 
   60 /* const char *
   61  * inet_ntop4(src, dst, size)
   62  *      format an IPv4 address
   63  * return:
   64  *      `dst' (as a const)
   65  * notes:
   66  *      (1) uses no statics
   67  *      (2) takes a u_char* not an in_addr as input
   68  * author:
   69  *      Paul Vixie, 1996.
   70  */
   71 static char *
   72 inet_ntop4(const u_char *src, char *dst, socklen_t size)
   73 {
   74         static const char fmt[] = "%u.%u.%u.%u";
   75         char tmp[sizeof "255.255.255.255"];
   76         int l;
   77 
   78         l = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
   79         if (l <= 0 || (socklen_t) l >= size) {
   80                 return (NULL);
   81         }
   82         strlcpy(dst, tmp, size);
   83         return (dst);
   84 }
   85 
   86 /* const char *
   87  * inet_ntop6(src, dst, size)
   88  *      convert IPv6 binary address into presentation (printable) format
   89  * author:
   90  *      Paul Vixie, 1996.
   91  */
   92 static char *
   93 inet_ntop6(const u_char *src, char *dst, socklen_t size)
   94 {
   95         /*
   96          * Note that int32_t and int16_t need only be "at least" large enough
   97          * to contain a value of the specified size.  On some systems, like
   98          * Crays, there is no such thing as an integer variable with 16 bits.
   99          * Keep this in mind if you think this function should have been coded
  100          * to use pointer overlays.  All the world's not a VAX.
  101          */
  102         char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
  103         struct { int base, len; } best, cur;
  104 #define NS_IN6ADDRSZ    16
  105 #define NS_INT16SZ      2
  106         u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
  107         int i;
  108 
  109         /*
  110          * Preprocess:
  111          *      Copy the input (bytewise) array into a wordwise array.
  112          *      Find the longest run of 0x00's in src[] for :: shorthanding.
  113          */
  114         memset(words, '\0', sizeof words);
  115         for (i = 0; i < NS_IN6ADDRSZ; i++)
  116                 words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
  117         best.base = -1;
  118         best.len = 0;
  119         cur.base = -1;
  120         cur.len = 0;
  121         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
  122                 if (words[i] == 0) {
  123                         if (cur.base == -1)
  124                                 cur.base = i, cur.len = 1;
  125                         else
  126                                 cur.len++;
  127                 } else {
  128                         if (cur.base != -1) {
  129                                 if (best.base == -1 || cur.len > best.len)
  130                                         best = cur;
  131                                 cur.base = -1;
  132                         }
  133                 }
  134         }
  135         if (cur.base != -1) {
  136                 if (best.base == -1 || cur.len > best.len)
  137                         best = cur;
  138         }
  139         if (best.base != -1 && best.len < 2)
  140                 best.base = -1;
  141 
  142         /*
  143          * Format the result.
  144          */
  145         tp = tmp;
  146         for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
  147                 /* Are we inside the best run of 0x00's? */
  148                 if (best.base != -1 && i >= best.base &&
  149                     i < (best.base + best.len)) {
  150                         if (i == best.base)
  151                                 *tp++ = ':';
  152                         continue;
  153                 }
  154                 /* Are we following an initial run of 0x00s or any real hex? */
  155                 if (i != 0)
  156                         *tp++ = ':';
  157                 /* Is this address an encapsulated IPv4? */
  158                 if (i == 6 && best.base == 0 && (best.len == 6 ||
  159                     (best.len == 7 && words[7] != 0x0001) ||
  160                     (best.len == 5 && words[5] == 0xffff))) {
  161                         if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp)))
  162                                 return (NULL);
  163                         tp += strlen(tp);
  164                         break;
  165                 }
  166                 tp += sprintf(tp, "%x", words[i]);
  167         }
  168         /* Was it a trailing run of 0x00's? */
  169         if (best.base != -1 && (best.base + best.len) == 
  170             (NS_IN6ADDRSZ / NS_INT16SZ))
  171                 *tp++ = ':';
  172         *tp++ = '\0';
  173 
  174         /*
  175          * Check for overflow, copy, and we're done.
  176          */
  177         if ((socklen_t)(tp - tmp) > size) {
  178                 return (NULL);
  179         }
  180         strcpy(dst, tmp);
  181         return (dst);
  182 }
  183 
  184 /*! \file */

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