giplib: separate functions in lib and app

Signed-off-by: Nagy Károly Gábriel <k@jpi.io>
2019-01-19 22:15:36 +02:00
parent 8471fcd3de
commit af71b64160
2 changed files with 107 additions and 32 deletions
@@ -0,0 +1,142 @@
+package giplib
+
+import (
+	"github.com/miekg/dns"
+)
+
+/*
+dig {-4,-6} +short myip.opendns.com @resolver1.opendns.com
+dig {-4,-6} TXT +short o-o.myaddr.l.google.com @ns1.google.com
+*/
+
+func GetIPv4() string {
+	o4 := getO4()
+	g4 := getG4()
+	if o4 == g4 {
+		return o4
+	}
+	return ""
+}
+
+func GetIPv6() string {
+	o6 := getO6()
+	g6 := getG6()
+	if o6 == g6 {
+		return o6
+	}
+	return ""
+}
+
+func getO4() string {
+	var ipv4 string
+	nameserver := dns.Fqdn("resolver1.opendns.com") + ":53"
+
+	c := new(dns.Client)
+	m := &dns.Msg{
+		MsgHdr: dns.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: make([]dns.Question, 1),
+	}
+	c.Net = "udp4"
+	m.SetQuestion("myip.opendns.com.", dns.TypeA)
+	r4, _, e4 := c.Exchange(m, nameserver)
+
+	if e4 != nil {
+		ipv4 = ""
+	} else {
+		ipv4 = getIP(r4.Answer)
+	}
+
+	return ipv4
+}
+
+func getO6() string {
+	var ipv6 string
+	nameserver := dns.Fqdn("resolver1.opendns.com") + ":53"
+
+	c := new(dns.Client)
+	m := &dns.Msg{
+		MsgHdr: dns.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: make([]dns.Question, 1),
+	}
+	c.Net = "udp6"
+	m.SetQuestion("myip.opendns.com.", dns.TypeAAAA)
+	r6, _, e6 := c.Exchange(m, nameserver)
+
+	if e6 != nil {
+		ipv6 = ""
+	} else {
+		ipv6 = getIP(r6.Answer)
+	}
+
+	return ipv6
+}
+
+func getG4() string {
+	var ipv4 string
+	nameserver := dns.Fqdn("ns1.google.com") + ":53"
+
+	c := new(dns.Client)
+	m := &dns.Msg{
+		MsgHdr: dns.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: make([]dns.Question, 1),
+	}
+	c.Net = "udp4"
+	m.SetQuestion("o-o.myaddr.l.google.com.", dns.TypeTXT)
+	r4, _, e4 := c.Exchange(m, nameserver)
+
+	if e4 != nil {
+		ipv4 = ""
+	} else {
+		ipv4 = getIP(r4.Answer)
+	}
+
+	return ipv4
+}
+
+func getG6() string {
+	var ipv6 string
+	nameserver := dns.Fqdn("ns1.google.com") + ":53"
+
+	c := new(dns.Client)
+	m := &dns.Msg{
+		MsgHdr: dns.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: make([]dns.Question, 1),
+	}
+	c.Net = "udp6"
+	m.SetQuestion("o-o.myaddr.l.google.com.", dns.TypeTXT)
+	r6, _, e6 := c.Exchange(m, nameserver)
+
+	if e6 != nil {
+		ipv6 = ""
+	} else {
+		ipv6 = getIP(r6.Answer)
+	}
+
+	return ipv6
+}
+
+func getIP(ra []dns.RR) string {
+	//the answer will always be one IP or none
+	var ip string
+	for _, ansa := range ra {
+		switch ansb := ansa.(type) {
+		case *dns.A:
+			ip = ansb.A.String()
+		case *dns.AAAA:
+			ip = ansb.AAAA.String()
+		case *dns.TXT:
+			// we always expect only one IP in the field
+			ip = ansb.Txt[0]
+		}
+	}
+
+	return ip
+}