ref: 9eb192f586316361a78cf399b410716ee20ed132
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"); } }