xref: /freebsd/contrib/tcpdump/addrtostr.c (revision 56b17de1e8360fe131d425de20b5e75ff3ea897c)
1 /*
2  * Copyright (c) 1999 Kungliga Tekniska Högskolan
3  * (Royal Institute of Technology, Stockholm, Sweden).
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  *
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  *
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * 3. All advertising materials mentioning features or use of this software
18  *    must display the following acknowledgement:
19  *      This product includes software developed by the Kungliga Tekniska
20  *      Högskolan and its contributors.
21  *
22  * 4. Neither the name of the Institute nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  */
38 
39 #include <config.h>
40 
41 #include "netdissect-stdinc.h"
42 #include "addrtostr.h"
43 
44 #include <stdio.h>
45 #include <string.h>
46 
47 /*
48  *
49  */
50 
51 #ifndef IN6ADDRSZ
52 #define IN6ADDRSZ   16   /* IPv6 T_AAAA */
53 #endif
54 
55 #ifndef INT16SZ
56 #define INT16SZ     2    /* word size */
57 #endif
58 
59 const char *
60 addrtostr (const void *src, char *dst, size_t size)
61 {
62     const u_char *srcaddr = (const u_char *)src;
63     const char digits[] = "0123456789";
64     int i;
65     const char *orig_dst = dst;
66 
67     if (size < INET_ADDRSTRLEN) {
68 	errno = ENOSPC;
69 	return NULL;
70     }
71     for (i = 0; i < 4; ++i) {
72 	int n = *srcaddr++;
73 	int non_zerop = 0;
74 
75 	if (non_zerop || n / 100 > 0) {
76 	    *dst++ = digits[n / 100];
77 	    n %= 100;
78 	    non_zerop = 1;
79 	}
80 	if (non_zerop || n / 10 > 0) {
81 	    *dst++ = digits[n / 10];
82 	    n %= 10;
83 	    non_zerop = 1;
84 	}
85 	*dst++ = digits[n];
86 	if (i != 3)
87 	    *dst++ = '.';
88     }
89     *dst++ = '\0';
90     return orig_dst;
91 }
92 
93 /*
94  * Convert IPv6 binary address into presentation (printable) format.
95  */
96 const char *
97 addrtostr6 (const void *src, char *dst, size_t size)
98 {
99   /*
100    * Note that int32_t and int16_t need only be "at least" large enough
101    * to contain a value of the specified size.  On some systems, like
102    * Crays, there is no such thing as an integer variable with 16 bits.
103    * Keep this in mind if you think this function should have been coded
104    * to use pointer overlays.  All the world's not a VAX.
105    */
106   const u_char *srcaddr = (const u_char *)src;
107   char *dp;
108   size_t space_left, added_space;
109   int snprintfed;
110   struct {
111     int base;
112     int len;
113   } best, cur;
114   uint16_t words [IN6ADDRSZ / INT16SZ];
115   int  i;
116 
117   /* Preprocess:
118    *  Copy the input (bytewise) array into a wordwise array.
119    *  Find the longest run of 0x00's in src[] for :: shorthanding.
120    */
121   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++)
122       words[i] = (srcaddr[2*i] << 8) | srcaddr[2*i + 1];
123 
124   best.len = 0;
125   best.base = -1;
126   cur.len = 0;
127   cur.base  = -1;
128   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
129     if (words[i] == 0) {
130       if (cur.base == -1)
131            cur.base = i, cur.len = 1;
132       else cur.len++;
133     } else if (cur.base != -1) {
134       if (best.base == -1 || cur.len > best.len)
135          best = cur;
136       cur.base = -1;
137     }
138   }
139   if ((cur.base != -1) && (best.base == -1 || cur.len > best.len))
140      best = cur;
141   if (best.base != -1 && best.len < 2)
142      best.base = -1;
143 
144   /* Format the result.
145    */
146   dp = dst;
147   space_left = size;
148 #define APPEND_CHAR(c) \
149     { \
150         if (space_left == 0) { \
151             errno = ENOSPC; \
152             return (NULL); \
153         } \
154         *dp++ = c; \
155         space_left--; \
156     }
157   for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
158     /* Are we inside the best run of 0x00's?
159      */
160     if (best.base != -1 && i >= best.base && i < (best.base + best.len)) {
161       if (i == best.base)
162 	  APPEND_CHAR(':');
163       continue;
164     }
165 
166     /* Are we following an initial run of 0x00s or any real hex?
167      */
168     if (i != 0)
169        APPEND_CHAR(':');
170 
171     /* Is this address an encapsulated IPv4?
172      */
173     if (i == 6 && best.base == 0 &&
174         (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
175     {
176       if (!addrtostr(srcaddr+12, dp, space_left)) {
177         errno = ENOSPC;
178         return (NULL);
179       }
180       added_space = strlen(dp);
181       dp += added_space;
182       space_left -= added_space;
183       break;
184     }
185     snprintfed = snprintf (dp, space_left, "%x", words[i]);
186     if (snprintfed < 0)
187         return (NULL);
188     if ((size_t) snprintfed >= space_left) {
189         errno = ENOSPC;
190         return (NULL);
191     }
192     dp += snprintfed;
193     space_left -= snprintfed;
194   }
195 
196   /* Was it a trailing run of 0x00's?
197    */
198   if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
199      APPEND_CHAR(':');
200   APPEND_CHAR('\0');
201 
202   return (dst);
203 }
204