ref: 75d6267a5f788162d92e7a5ae126cd8b0770aa8a
dir: /sys/src/libndb/mkptrname.c/
#include <u.h>
#include <libc.h>
#include <ip.h>
/*
* convert address into a reverse lookup address
*/
void
mkptrname(char *ip, char *rip, int rlen)
{
uchar a[IPaddrlen];
char *p, *e;
int i;
if(cistrstr(ip, "in-addr.arpa") || cistrstr(ip, "ip6.arpa") || parseip(a, ip) == -1)
snprint(rip, rlen, "%s", ip);
else if(isv4(a))
snprint(rip, rlen, "%ud.%ud.%ud.%ud.in-addr.arpa",
a[15], a[14], a[13], a[12]);
else{
p = rip;
e = rip + rlen;
for(i = 15; i >= 0; i--){
p = seprint(p, e, "%ux.", a[i]&0xf);
p = seprint(p, e, "%ux.", a[i]>>4);
}
seprint(p, e, "ip6.arpa");
}
}