ip6tos.c

00001 /*
00002  * Copyright (c) 2014-2015 ARM Limited. All rights reserved.
00003  * SPDX-License-Identifier: Apache-2.0
00004  * Licensed under the Apache License, Version 2.0 (the License); you may
00005  * not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  * http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00012  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #include <stdio.h>
00017 #include <string.h>
00018 #include "common_functions.h"
00019 #include "ip6string.h"
00020 
00021 /**
00022  * Print binary IPv6 address to a string.
00023  * String must contain enough room for full address, 40 bytes exact.
00024  * IPv4 tunneling addresses are not covered.
00025  * \param addr IPv6 address.
00026  * \p buffer to write string to.
00027  */
00028 uint_fast8_t ip6tos(const void *ip6addr, char *p)
00029 {
00030     char *p_orig = p;
00031     uint_fast8_t zero_start = 255, zero_len = 1;
00032     const uint8_t *addr = ip6addr;
00033     uint_fast16_t part;
00034 
00035     /* Follow RFC 5952 - pre-scan for longest run of zeros */
00036     for (uint_fast8_t n = 0; n < 8; n++) {
00037         part = *addr++;
00038         part = (part << 8) | *addr++;
00039         if (part != 0) {
00040             continue;
00041         }
00042 
00043         /* We're at the start of a run of zeros - scan to non-zero (or end) */
00044         uint_fast8_t n0 = n;
00045         for (n = n0 + 1; n < 8; n++) {
00046             part = *addr++;
00047             part = (part << 8) | *addr++;
00048             if (part != 0) {
00049                 break;
00050             }
00051         }
00052 
00053         /* Now n0->initial zero of run, n->after final zero in run. Is this the
00054          * longest run yet? If equal, we stick with the previous one - RFC 5952
00055          * S4.2.3. Note that zero_len being initialised to 1 stops us
00056          * shortening a 1-part run (S4.2.2.)
00057          */
00058         if (n - n0 > zero_len) {
00059             zero_start = n0;
00060             zero_len = n - n0;
00061         }
00062 
00063         /* Continue scan for initial zeros from part n+1 - we've already
00064          * consumed part n, and know it's non-zero. */
00065     }
00066 
00067     /* Now go back and print, jumping over any zero run */
00068     addr = ip6addr;
00069     for (uint_fast8_t n = 0; n < 8;) {
00070         if (n == zero_start) {
00071             if (n == 0) {
00072                 *p++ = ':';
00073             }
00074             *p++ = ':';
00075             addr += 2 * zero_len;
00076             n += zero_len;
00077             continue;
00078         }
00079 
00080         part = *addr++;
00081         part = (part << 8) | *addr++;
00082         n++;
00083 
00084         p += sprintf(p, "%"PRIxFAST16, part);
00085 
00086         /* One iteration writes "part:" rather than ":part", and has the
00087          * explicit check for n == 8 below, to allow easy extension for
00088          * IPv4-in-IPv6-type addresses ("xxxx::xxxx:a.b.c.d"): we'd just
00089          * run the same loop for 6 parts, and output would then finish with the
00090          * required : or ::, ready for "a.b.c.d" to be tacked on.
00091          */
00092         if (n != 8) {
00093             *p++ = ':';
00094         }
00095     }
00096     *p = '\0';
00097 
00098     // Return length of generated string, excluding the terminating null character
00099     return p - p_orig;
00100 }
00101 
00102 uint_fast8_t ip6_prefix_tos(const void *prefix, uint_fast8_t prefix_len, char *p)
00103 {
00104     char *wptr = p;
00105     uint8_t addr[16] = {0};
00106 
00107     if (prefix_len > 128) {
00108         return 0;
00109     }
00110 
00111     // Generate prefix part of the string
00112     bitcopy(addr, prefix, prefix_len);
00113     wptr += ip6tos(addr, wptr);
00114     // Add the prefix length part of the string
00115     wptr += sprintf(wptr, "/%"PRIuFAST8, prefix_len);
00116 
00117     // Return total length of generated string
00118     return wptr - p;
00119 }