lib/ntop.c

   1 /*
   2  * optimized ntop, about 10x faster than libc versions [as of 2019]
   3  *
   4  * Copyright (c) 2019  David Lamparter, for NetDEF, Inc.
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #ifdef HAVE_CONFIG_H
  20 #include "config.h"
  21 #endif
  22
  23 #include <stdio.h>
  24 #include <stdint.h>
  25 #include <stdbool.h>
  26 #include <string.h>
  27 #include <sys/socket.h>
  28 #include <netinet/in.h>
  29 #include <arpa/inet.h>
  30
  31 #include "compiler.h"
  32
  33 #define pos (*posx)
  34
  35 static inline void putbyte(uint8_t bytex, char **posx)
  36         __attribute__((always_inline)) OPTIMIZE;
  37
  38 static inline void putbyte(uint8_t bytex, char **posx)
  39 {
  40         bool zero = false;
  41         int byte = bytex, tmp, a, b;
  42
  43         tmp = byte - 200;
  44         if (tmp >= 0) {
  45                 *pos++ = '2';
  46                 zero = true;
  47                 byte = tmp;
  48         } else {
  49                 tmp = byte - 100;
  50                 if (tmp >= 0) {
  51                         *pos++ = '1';
  52                         zero = true;
  53                         byte = tmp;
  54                 }
  55         }
  56
  57         /* make sure the compiler knows the value range of "byte" */
  58         assume(byte < 100 && byte >= 0);
  59
  60         b = byte % 10;
  61         a = byte / 10;
  62         if (a || zero) {
  63                 *pos++ = '0' + a;
  64                 *pos++ = '0' + b;
  65         } else
  66                 *pos++ = '0' + b;
  67 }
  68
  69 static inline void puthex(uint16_t word, char **posx)
  70         __attribute__((always_inline)) OPTIMIZE;
  71
  72 static inline void puthex(uint16_t word, char **posx)
  73 {
  74         const char *digits = "0123456789abcdef";
  75         if (word >= 0x1000)
  76                 *pos++ = digits[(word >> 12) & 0xf];
  77         if (word >= 0x100)
  78                 *pos++ = digits[(word >> 8) & 0xf];
  79         if (word >= 0x10)
  80                 *pos++ = digits[(word >> 4) & 0xf];
  81         *pos++ = digits[word & 0xf];
  82 }
  83
  84 #undef pos
  85
  86 const char *frr_inet_ntop(int af, const void * restrict src,
  87                           char * restrict dst, socklen_t size)
  88         __attribute__((flatten)) OPTIMIZE;
  89
  90 const char *frr_inet_ntop(int af, const void * restrict src,
  91                           char * restrict dst, socklen_t size)
  92 {
  93         const uint8_t *b = src;
  94         /* 8 * "abcd:" for IPv6
  95          * note: the IPv4-embedded IPv6 syntax is only used for ::A.B.C.D,
  96          * which isn't longer than 40 chars either.  even with ::ffff:A.B.C.D
  97          * it's shorter.
  98          */
  99         char buf[8 * 5], *o = buf;
 100         size_t best = 0, bestlen = 0, curlen = 0, i;
 101
 102         switch (af) {
 103         case AF_INET:
 104 inet4:
 105                 putbyte(b[0], &o);
 106                 *o++ = '.';
 107                 putbyte(b[1], &o);
 108                 *o++ = '.';
 109                 putbyte(b[2], &o);
 110                 *o++ = '.';
 111                 putbyte(b[3], &o);
 112                 *o++ = '\0';
 113                 break;
 114         case AF_INET6:
 115                 for (i = 0; i < 8; i++) {
 116                         if (b[i * 2] || b[i * 2 + 1]) {
 117                                 if (curlen && curlen > bestlen) {
 118                                         best = i - curlen;
 119                                         bestlen = curlen;
 120                                 }
 121                                 curlen = 0;
 122                                 continue;
 123                         }
 124                         curlen++;
 125                 }
 126                 if (curlen && curlen > bestlen) {
 127                         best = i - curlen;
 128                         bestlen = curlen;
 129                 }
 130                 /* do we want ::ffff:A.B.C.D? */
 131                 if (best == 0 && bestlen == 6) {
 132                         *o++ = ':';
 133                         *o++ = ':';
 134                         b += 12;
 135                         goto inet4;
 136                 }
 137                 if (bestlen == 1)
 138                         bestlen = 0;
 139
 140                 for (i = 0; i < 8; i++) {
 141                         if (bestlen && i == best) {
 142                                 if (i == 0)
 143                                         *o++ = ':';
 144                                 *o++ = ':';
 145                                 continue;
 146                         }
 147                         if (i > best && i < best + bestlen) {
 148                                 continue;
 149                         }
 150                         puthex((b[i * 2] << 8) | b[i * 2 + 1], &o);
 151
 152                         if (i < 7)
 153                                 *o++ = ':';
 154                 }
 155                 *o++ = '\0';
 156                 break;
 157         default:
 158                 return NULL;
 159         }
 160
 161         i = o - buf;
 162         if (i > size)
 163                 return NULL;
 164         /* compiler might inline memcpy if it knows the length is short,
 165          * although neither gcc nor clang actually do this currently [2019]
 166          */
 167         assume(i <= 8 * 5);
 168         memcpy(dst, buf, i);
 169         return dst;
 170 }
 171
 172 #if !defined(INET_NTOP_NO_OVERRIDE) && !defined(__APPLE__)
 173 /* we want to override libc inet_ntop, but make sure it shows up in backtraces
 174  * as frr_inet_ntop (to avoid confusion while debugging)
 175  */
 176 const char *inet_ntop(int af, const void *src, char *dst, socklen_t size)
 177         __attribute__((alias ("frr_inet_ntop")));
 178 #endif