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-rw-r--r--main.go52
1 files changed, 51 insertions, 1 deletions
diff --git a/main.go b/main.go
index 2096965..7f9f8b8 100644
--- a/main.go
+++ b/main.go
@@ -8,6 +8,10 @@ import (
"strings"
)
+var (
+ txt = flag.Bool("txt", false, "also look up TXT records")
+)
+
func main() {
flag.Parse()
for _, arg := range flag.Args() {
@@ -19,10 +23,20 @@ func main() {
ip := ipnet.IP
for ipnet.Contains(ip) {
if names, err := net.LookupAddr(ip.String()); err != nil {
- fmt.Fprintf(os.Stderr, "%s\t# error: %s\n", ip, err)
+ fmt.Fprintf(os.Stderr, "%s\t# PTR error: %s\n", ip, err)
} else {
fmt.Printf("%s\t%s\n", ip, strings.Join(names, " "))
}
+ if *txt {
+ recs, err := net.LookupTXT(arpa(ip))
+ if err != nil {
+ fmt.Fprintf(os.Stderr, "%s\t# TXT error: %s\n", ip, err)
+ } else {
+ for _, rec := range recs {
+ fmt.Printf("%s\tTXT %q\n", ip, rec)
+ }
+ }
+ }
ip = next(ip)
}
}
@@ -30,6 +44,42 @@ func main() {
}
}
+// arpa returns the .in-addr.arpa or .ip6.arpa name corresponding with the given IP.
+func arpa(ip net.IP) string {
+ if ip4 := ip.To4(); ip4 != nil {
+ return fmt.Sprintf(
+ "%d.%d.%d.%d.in-addr.arpa",
+ ip4[3], ip4[2], ip4[1], ip4[0],
+ )
+ } else if ip6 := ip.To16(); ip6 != nil {
+ return fmt.Sprintf(
+ "%x.%x.%x.%x.%x.%x.%x.%x."+
+ "%x.%x.%x.%x.%x.%x.%x.%x."+
+ "%x.%x.%x.%x.%x.%x.%x.%x."+
+ "%x.%x.%x.%x.%x.%x.%x.%x."+
+ "ip6.arpa",
+ ip6[15]&0xf, ip6[15]&0xf0>>4,
+ ip6[14]&0xf, ip6[14]&0xf0>>4,
+ ip6[13]&0xf, ip6[13]&0xf0>>4,
+ ip6[12]&0xf, ip6[12]&0xf0>>4,
+ ip6[11]&0xf, ip6[11]&0xf0>>4,
+ ip6[10]&0xf, ip6[10]&0xf0>>4,
+ ip6[9]&0xf, ip6[9]&0xf0>>4,
+ ip6[8]&0xf, ip6[8]&0xf0>>4,
+ ip6[7]&0xf, ip6[7]&0xf0>>4,
+ ip6[6]&0xf, ip6[6]&0xf0>>4,
+ ip6[5]&0xf, ip6[5]&0xf0>>4,
+ ip6[4]&0xf, ip6[4]&0xf0>>4,
+ ip6[3]&0xf, ip6[3]&0xf0>>4,
+ ip6[2]&0xf, ip6[2]&0xf0>>4,
+ ip6[1]&0xf, ip6[1]&0xf0>>4,
+ ip6[0]&0xf, ip6[0]&0xf0>>4,
+ )
+ } else {
+ panic("non-ip4 non-ip6 ip? " + ip.String())
+ }
+}
+
// next returns the next IP address after ip, or nil if there is no such address.
func next(ip net.IP) net.IP {
next := make(net.IP, len(ip))