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package network
import (
"net"
"os"
"testing"
"github.com/miekg/dns"
"gotest.tools/v3/assert"
)
const DNSRespAddr = "10.11.12.13"
// WriteTempResolvConf writes a resolv.conf that only contains a single
// nameserver line, with address addr.
// It returns the name of the temp file. The temp file will be deleted
// automatically by a t.Cleanup().
func WriteTempResolvConf(t *testing.T, addr string) string {
t.Helper()
// Not using t.TempDir() here because in rootless mode, while the temporary
// directory gets mode 0777, it's a subdir of an 0700 directory owned by root.
// So, it's not accessible by the daemon.
f, err := os.CreateTemp("", "resolv.conf")
assert.NilError(t, err)
t.Cleanup(func() { os.Remove(f.Name()) })
err = f.Chmod(0o644)
assert.NilError(t, err)
f.Write([]byte("nameserver " + addr + "\n"))
return f.Name()
}
// StartDaftDNS starts and returns a really, really daft DNS server that only
// responds to type-A requests, and always with address dnsRespAddr.
// The DNS server will be stopped automatically by a t.Cleanup().
func StartDaftDNS(t *testing.T, addr string) {
serveDNS := func(w dns.ResponseWriter, query *dns.Msg) {
if query.Question[0].Qtype == dns.TypeA {
resp := &dns.Msg{}
resp.SetReply(query)
answer := &dns.A{
Hdr: dns.RR_Header{
Name: query.Question[0].Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 600,
},
}
answer.A = net.ParseIP(DNSRespAddr)
resp.Answer = append(resp.Answer, answer)
_ = w.WriteMsg(resp)
}
}
conn, err := net.ListenUDP("udp", &net.UDPAddr{
IP: net.ParseIP(addr),
Port: 53,
})
assert.NilError(t, err)
server := &dns.Server{Handler: dns.HandlerFunc(serveDNS), PacketConn: conn}
go func() {
_ = server.ActivateAndServe()
}()
t.Cleanup(func() { server.Shutdown() })
}
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