lib/ntop.c

   1 // SPDX-License-Identifier: ISC
   2 /*
   3  * optimized ntop, about 10x faster than libc versions [as of 2019]
   4  *
   5  * Copyright (c) 2019  David Lamparter, for NetDEF, Inc.
   6  */
   7
   8 #ifdef HAVE_CONFIG_H
   9 #include "config.h"
  10 #endif
  11
  12 #include <stdio.h>
  13 #include <stdint.h>
  14 #include <stdbool.h>
  15 #include <string.h>
  16 #include <sys/socket.h>
  17 #include <netinet/in.h>
  18 #include <arpa/inet.h>
  19
  20 #include "compiler.h"
  21
  22 #define pos (*posx)
  23
  24 static inline void putbyte(uint8_t bytex, char **posx)
  25         __attribute__((always_inline)) OPTIMIZE;
  26
  27 static inline void putbyte(uint8_t bytex, char **posx)
  28 {
  29         bool zero = false;
  30         int byte = bytex, tmp, a, b;
  31
  32         tmp = byte - 200;
  33         if (tmp >= 0) {
  34                 *pos++ = '2';
  35                 zero = true;
  36                 byte = tmp;
  37         } else {
  38                 tmp = byte - 100;
  39                 if (tmp >= 0) {
  40                         *pos++ = '1';
  41                         zero = true;
  42                         byte = tmp;
  43                 }
  44         }
  45
  46         /* make sure the compiler knows the value range of "byte" */
  47         assume(byte < 100 && byte >= 0);
  48
  49         b = byte % 10;
  50         a = byte / 10;
  51         if (a || zero) {
  52                 *pos++ = '0' + a;
  53                 *pos++ = '0' + b;
  54         } else
  55                 *pos++ = '0' + b;
  56 }
  57
  58 static inline void puthex(uint16_t word, char **posx)
  59         __attribute__((always_inline)) OPTIMIZE;
  60
  61 static inline void puthex(uint16_t word, char **posx)
  62 {
  63         const char *digits = "0123456789abcdef";
  64         if (word >= 0x1000)
  65                 *pos++ = digits[(word >> 12) & 0xf];
  66         if (word >= 0x100)
  67                 *pos++ = digits[(word >> 8) & 0xf];
  68         if (word >= 0x10)
  69                 *pos++ = digits[(word >> 4) & 0xf];
  70         *pos++ = digits[word & 0xf];
  71 }
  72
  73 #undef pos
  74
  75 const char *frr_inet_ntop(int af, const void * restrict src,
  76                           char * restrict dst, socklen_t size)
  77         __attribute__((flatten)) OPTIMIZE;
  78
  79 const char *frr_inet_ntop(int af, const void * restrict src,
  80                           char * restrict dst, socklen_t size)
  81 {
  82         const uint8_t *b = src;
  83         /* 8 * "abcd:" for IPv6
  84          * note: the IPv4-embedded IPv6 syntax is only used for ::A.B.C.D,
  85          * which isn't longer than 40 chars either.  even with ::ffff:A.B.C.D
  86          * it's shorter.
  87          */
  88         char buf[8 * 5], *o = buf;
  89         size_t best = 0, bestlen = 0, curlen = 0, i;
  90
  91         switch (af) {
  92         case AF_INET:
  93 inet4:
  94                 putbyte(b[0], &o);
  95                 *o++ = '.';
  96                 putbyte(b[1], &o);
  97                 *o++ = '.';
  98                 putbyte(b[2], &o);
  99                 *o++ = '.';
 100                 putbyte(b[3], &o);
 101                 *o++ = '\0';
 102                 break;
 103         case AF_INET6:
 104                 for (i = 0; i < 8; i++) {
 105                         if (b[i * 2] || b[i * 2 + 1]) {
 106                                 if (curlen && curlen > bestlen) {
 107                                         best = i - curlen;
 108                                         bestlen = curlen;
 109                                 }
 110                                 curlen = 0;
 111                                 continue;
 112                         }
 113                         curlen++;
 114                 }
 115                 if (curlen && curlen > bestlen) {
 116                         best = i - curlen;
 117                         bestlen = curlen;
 118                 }
 119                 /* do we want ::ffff:A.B.C.D? */
 120                 if (best == 0 && bestlen == 6) {
 121                         *o++ = ':';
 122                         *o++ = ':';
 123                         b += 12;
 124                         goto inet4;
 125                 }
 126                 if (bestlen == 1)
 127                         bestlen = 0;
 128
 129                 for (i = 0; i < 8; i++) {
 130                         if (bestlen && i == best) {
 131                                 if (i == 0)
 132                                         *o++ = ':';
 133                                 *o++ = ':';
 134                                 continue;
 135                         }
 136                         if (i > best && i < best + bestlen) {
 137                                 continue;
 138                         }
 139                         puthex((b[i * 2] << 8) | b[i * 2 + 1], &o);
 140
 141                         if (i < 7)
 142                                 *o++ = ':';
 143                 }
 144                 *o++ = '\0';
 145                 break;
 146         default:
 147                 return NULL;
 148         }
 149
 150         i = o - buf;
 151         if (i > size)
 152                 return NULL;
 153         /* compiler might inline memcpy if it knows the length is short,
 154          * although neither gcc nor clang actually do this currently [2019]
 155          */
 156         assume(i <= 8 * 5);
 157         memcpy(dst, buf, i);
 158         return dst;
 159 }
 160
 161 #if !defined(INET_NTOP_NO_OVERRIDE) && !defined(__APPLE__)
 162 /* we want to override libc inet_ntop, but make sure it shows up in backtraces
 163  * as frr_inet_ntop (to avoid confusion while debugging)
 164  */
 165 const char *inet_ntop(int af, const void *src, char *dst, socklen_t size)
 166         __attribute__((alias ("frr_inet_ntop")));
 167 #endif