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

     /*
      * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
      * Copyright (c) 1996-1999 by Internet Software Consortium.
      *
      * Permission to use, copy, modify, and distribute this software for any
      * purpose with or without fee is hereby granted, provided that the above
      * copyright notice and this permission notice appear in all copies.
      *
      * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
     * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
     * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
     * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     */
    
    #if defined(LIBC_SCCS) && !defined(lint)
    static const char rcsid[] = "$Id: inet_ntop.c,v 1.3.18.2 2005/11/03 23:02:22 marka Exp $";
    #endif /* LIBC_SCCS and not lint */
    
    #include <sys/param.h>
    #include <sys/socket.h>
    #include <sys/systm.h>
    
    #include <netinet/in.h>
    
    /*%
     * WARNING: Don't even consider trying to compile this on a system where
     * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
     */
    
    static char     *inet_ntop4(const u_char *src, char *dst, socklen_t size);
    static char     *inet_ntop6(const u_char *src, char *dst, socklen_t size);
    
    /* char *
     * inet_ntop(af, src, dst, size)
     *      convert a network format address to presentation format.
     * return:
     *      pointer to presentation format address (`dst'), or NULL (see errno).
     * author:
     *      Paul Vixie, 1996.
     */
    const char *
    inet_ntop(int af, const void *src, char *dst, socklen_t size)
    {
            switch (af) {
            case AF_INET:
                    return inet_ntop4(src, dst, size);
            case AF_INET6:
                    return inet_ntop6(src, dst, size);
            default:
                    return NULL;
            }
            /* NOTREACHED */
    }
    
    /* const char *
     * inet_ntop4(src, dst, size)
     *      format an IPv4 address
     * return:
     *      `dst' (as a const)
     * notes:
     *      (1) uses no statics
     *      (2) takes a u_char* not an in_addr as input
     * author:
     *      Paul Vixie, 1996.
     */
    static char *
    inet_ntop4(const u_char *src, char *dst, socklen_t size)
    {
            static const char fmt[] = "%u.%u.%u.%u";
            char tmp[sizeof "255.255.255.255"];
            int l;
    
            l = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
            if (l <= 0 || (socklen_t) l >= size) {
                    return NULL;
            }
            strlcpy(dst, tmp, size);
            return dst;
    }
    
    /* const char *
     * inet_ntop6(src, dst, size)
     *      convert IPv6 binary address into presentation (printable) format
     * author:
     *      Paul Vixie, 1996.
     */
    static char *
    inet_ntop6(const u_char *src, char *dst, socklen_t size)
    {
            /*
             * Note that int32_t and int16_t need only be "at least" large enough
             * to contain a value of the specified size.  On some systems, like
             * Crays, there is no such thing as an integer variable with 16 bits.
             * Keep this in mind if you think this function should have been coded
             * to use pointer overlays.  All the world's not a VAX.
             */
           char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
           struct { int base, len; } best, cur;
   #define NS_IN6ADDRSZ    16
   #define NS_INT16SZ      2
           u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
           int i;
   
           /*
            * Preprocess:
            *      Copy the input (bytewise) array into a wordwise array.
            *      Find the longest run of 0x00's in src[] for :: shorthanding.
            */
           memset(words, '\0', sizeof words);
           for (i = 0; i < NS_IN6ADDRSZ; i++) {
                   words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
           }
           best.base = -1;
           best.len = 0;
           cur.base = -1;
           cur.len = 0;
           for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
                   if (words[i] == 0) {
                           if (cur.base == -1) {
                                   cur.base = i;
                                   cur.len = 1;
                           } else {
                                   cur.len++;
                           }
                   } else {
                           if (cur.base != -1) {
                                   if (best.base == -1 || cur.len > best.len) {
                                           best = cur;
                                   }
                                   cur.base = -1;
                           }
                   }
           }
           if (cur.base != -1) {
                   if (best.base == -1 || cur.len > best.len) {
                           best = cur;
                   }
           }
           if (best.base != -1 && best.len < 2) {
                   best.base = -1;
           }
   
           /*
            * Format the result.
            */
           tp = tmp;
           for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
                   /* Are we inside the best run of 0x00's? */
                   if (best.base != -1 && i >= best.base &&
                       i < (best.base + best.len)) {
                           if (i == best.base) {
                                   *tp++ = ':';
                           }
                           continue;
                   }
                   /* Are we following an initial run of 0x00s or any real hex? */
                   if (i != 0) {
                           *tp++ = ':';
                   }
                   /* Is this address an encapsulated IPv4? */
                   if (i == 6 && best.base == 0 && (best.len == 6 ||
                       (best.len == 7 && words[7] != 0x0001) ||
                       (best.len == 5 && words[5] == 0xffff))) {
                           if (!inet_ntop4(src + 12, tp,
                               (socklen_t)(sizeof tmp - (tp - tmp)))) {
                                   return NULL;
                           }
                           tp += strlen(tp);
                           break;
                   }
                   tp += scnprintf(tp, sizeof(tmp), "%x", words[i]);
           }
           /* Was it a trailing run of 0x00's? */
           if (best.base != -1 && (best.base + best.len) ==
               (NS_IN6ADDRSZ / NS_INT16SZ)) {
                   *tp++ = ':';
           }
           *tp++ = '\0';
   
           /*
            * Check for overflow, copy, and we're done.
            */
           if ((socklen_t)(tp - tmp) > size) {
                   return NULL;
           }
           strlcpy(dst, tmp, size);
           return dst;
   }
   
   /*! \file */

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