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test(grpc): add fuzzer (#7513)
This commit is contained in:
Ville Vesilehto
GitHub
216
plugin/grpc/fuzz.go
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216
plugin/grpc/fuzz.go
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@@ -0,0 +1,216 @@
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//go:build gofuzz
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package grpc
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import (
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"context"
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"github.com/coredns/coredns/pb"
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"github.com/coredns/coredns/plugin/pkg/fuzz"
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"github.com/coredns/coredns/plugin/test"
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"github.com/miekg/dns"
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grpcgo "google.golang.org/grpc"
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"google.golang.org/grpc/codes"
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"google.golang.org/grpc/status"
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)
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// fakeClient implements pb.DnsServiceClient without doing any network I/O.
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// Its behavior is controlled by the mode field.
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type fakeClient struct {
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mode byte
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idx int
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}
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func (f *fakeClient) Query(_ context.Context, in *pb.DnsPacket, _ ...grpcgo.CallOption) (*pb.DnsPacket, error) {
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// Derive mode deterministically from request bytes to vary behavior per call.
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m := f.mode
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if len(in.GetMsg()) > 0 {
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b := in.GetMsg()[f.idx%len(in.GetMsg())]
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f.idx++
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m = b
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}
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switch m % 12 {
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case 0:
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// Success echo: return the same bytes.
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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case 1:
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// Return NotFound to exercise NXDOMAIN conversion and optional fallthrough.
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return nil, status.Error(codes.NotFound, "not found")
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case 2:
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// Return a transient error to trigger retry/rotation.
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return nil, status.Error(codes.Unavailable, "unavailable")
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case 3:
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// Corrupt response that fails dns.Msg Unpack.
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return &pb.DnsPacket{Msg: []byte{0x00, 0x01, 0x02}}, nil
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case 4:
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// Valid DNS message with mismatched ID/qname to trigger formerr path in ServeDNS.
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var req dns.Msg
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if err := req.Unpack(in.GetMsg()); err != nil {
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// If input isn't a DNS message, just echo to avoid blocking fuzzing.
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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resp := new(dns.Msg)
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resp.SetReply(&req)
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resp.Id = req.Id + 1
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// Alter question name if present.
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if len(req.Question) > 0 {
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resp.Question[0].Name = "example.net."
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}
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packed, err := resp.Pack()
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if err != nil {
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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return &pb.DnsPacket{Msg: packed}, nil
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case 5:
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// Success with EDNS and larger answer to stress flags and sizes.
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var req dns.Msg
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if err := req.Unpack(in.GetMsg()); err != nil {
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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resp := new(dns.Msg)
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resp.SetReply(&req)
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// Set EDNS0 with varying UDP size and DO bit based on m.
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size := uint16(512)
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if (m>>1)&1 == 1 {
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size = 1232
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}
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if (m>>2)&1 == 1 {
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size = 4096
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}
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do := ((m>>3)&1 == 1)
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resp.SetEdns0(size, do)
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// Optionally set TC bit to exercise truncation handling.
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if (m>>4)&1 == 1 {
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resp.Truncated = true
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}
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// Add a few TXT records to grow the payload.
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name := "."
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if len(req.Question) > 0 {
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name = req.Question[0].Name
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}
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n := int(1 + (m % 16))
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for range n {
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resp.Answer = append(resp.Answer, &dns.TXT{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{"aaaaaaaaaaaaaaaaaaaaaaaa", "bbbbbbbbbbbbbbbbbbbbbbbb"}})
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}
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packed, err := resp.Pack()
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if err != nil {
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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return &pb.DnsPacket{Msg: packed}, nil
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case 6:
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return nil, status.Error(codes.DeadlineExceeded, "timeout")
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case 7:
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return nil, status.Error(codes.Internal, "internal")
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case 8:
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return nil, status.Error(codes.ResourceExhausted, "quota")
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case 9:
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return nil, status.Error(codes.PermissionDenied, "denied")
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case 10:
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// NODATA: NOERROR with empty Answer and SOA in Authority.
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var req dns.Msg
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if err := req.Unpack(in.GetMsg()); err != nil {
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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resp := new(dns.Msg)
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resp.SetRcode(&req, dns.RcodeSuccess)
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name := "."
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if len(req.Question) > 0 {
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name = req.Question[0].Name
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}
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resp.Ns = append(resp.Ns, &dns.SOA{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeSOA, Class: dns.ClassINET, Ttl: 60}, Ns: "ns.example.", Mbox: "hostmaster.example.", Serial: 1, Refresh: 3600, Retry: 600, Expire: 86400, Minttl: 60})
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packed, err := resp.Pack()
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if err != nil {
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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return &pb.DnsPacket{Msg: packed}, nil
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case 11:
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// TC-only: truncated response without answers.
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var req dns.Msg
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if err := req.Unpack(in.GetMsg()); err != nil {
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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resp := new(dns.Msg)
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resp.SetReply(&req)
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resp.Truncated = true
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packed, err := resp.Pack()
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if err != nil {
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return &pb.DnsPacket{Msg: in.GetMsg()}, nil
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}
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return &pb.DnsPacket{Msg: packed}, nil
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default:
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// Empty/zero-length response to exercise unpack error path.
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return &pb.DnsPacket{Msg: nil}, nil
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}
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}
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// Fuzz exercises the grpc plugin using a fake client and the shared fuzz harness.
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func Fuzz(data []byte) int {
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if len(data) == 0 {
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return 0
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}
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cfg := data[0]
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rest := data[1:]
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g := &GRPC{
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from: ".",
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Next: test.ErrorHandler(),
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}
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// Select policy based on cfg bits to vary list() ordering.
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switch cfg % 3 {
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case 0:
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g.p = &random{}
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case 1:
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g.p = &roundRobin{}
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default:
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g.p = &sequential{}
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}
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// Optionally enable fallthrough; choose scope based on input bit.
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if cfg&0x80 != 0 {
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if cfg&0x01 != 0 {
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g.Fall.SetZonesFromArgs([]string{"."})
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} else {
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g.Fall.SetZonesFromArgs([]string{g.from})
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}
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}
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// Create 0–3 fake proxies with varied behaviors.
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numProxies := int((cfg >> 4) & 0x03)
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if numProxies == 0 {
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if _, is := g.p.(*roundRobin); is {
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// Avoid divide-by-zero in roundRobin policy when pool is empty.
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g.p = &sequential{}
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}
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}
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for i := range numProxies {
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mode := byte(i)
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if len(rest) > 0 {
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mode = rest[i%len(rest)]
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}
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p := &Proxy{addr: "fake"}
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p.client = &fakeClient{mode: mode}
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g.proxies = append(g.proxies, p)
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}
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// Deterministically set a narrow from to miss match and hit Next/SERVFAIL paths.
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if cfg&0x20 != 0 {
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g.from = "_not_matching_."
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}
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// Optionally construct a tiny deterministic query to vary RD/CD flags.
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if cfg&0x08 != 0 {
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var rq dns.Msg
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rq.SetQuestion("example.org.", dns.TypeA)
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rq.RecursionDesired = (cfg&0x04 != 0)
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rq.CheckingDisabled = (cfg&0x02 != 0)
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if packed, err := rq.Pack(); err == nil {
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rest = packed
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}
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}
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return fuzz.Do(g, rest)
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}
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