ip6_scan.c

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#include "scan.h"
#include "ip4.h"
#include "ip6.h"

/*
 * IPv6 addresses are really ugly to parse.
 * Syntax: (h = hex digit)
 *   1. hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh
 *   2. any number of 0000 may be abbreviated as "::", but only once
 *   3. The last two words may be written as IPv4 address
 */

unsigned int ip6_scan(const char *s,char ip[16])
{
  unsigned int i;
  unsigned int len=0;
  unsigned long u;
//  const unsigned char V4mappedprefix[12] = {0,0,0,0,0,0,0,0,0,0,0xff,0xff};

  char suffix[16];
  int prefixlen=0;
  int suffixlen=0;

  if ((i=ip4_scan(s,ip+12))) {
    for (len=0; len<12; ++len) ip[len]=V4mappedprefix[len];
    return i;
  }
  for (i=0; i<16; i++) ip[i]=0;
  for (;;) {
    if (*s == ':') {
      len++;
      if (s[1] == ':') {        /* Found "::", skip to part 2 */
        s+=2;
        len++;
        break;
      }
      s++;
    }
    i = scan_xlong(s,&u);
    if (!i) return 0;
    if (prefixlen==12 && s[i]=='.') {
      /* the last 4 bytes may be written as IPv4 address */
      i=ip4_scan(s,ip+12);
      if (i)
        return i+len;
      else
        return 0;
    }
    ip[prefixlen++] = (u >> 8);
    ip[prefixlen++] = (u & 255);
    s += i; len += i;
    if (prefixlen == 16)
      return len;
  }

/* part 2, after "::" */
  for (;;) {
    if (*s == ':') {
      if (suffixlen==0)
        break;
      s++;
      len++;
    } else if (suffixlen!=0)
      break;
    i = scan_xlong(s,&u);
    if (!i) {
      len--;
      break;
    }
    if (suffixlen+prefixlen<=12 && s[i]=='.') {
      int j=ip4_scan(s,suffix+suffixlen);
      if (j) {
        suffixlen += 4;
        len += j;
        break;
      } else
        prefixlen = 12-suffixlen;       /* make end-of-loop test true */
    }
    suffix[suffixlen++] = (u >> 8);
    suffix[suffixlen++] = (u & 255);
    s += i; len += i;
    if (prefixlen+suffixlen == 16)
      break;
  }
  for (i=0; i<suffixlen; i++)
    ip[16-suffixlen+i] = suffix[i];
  return len;
}