├── .gitignore ├── Corefile ├── LICENSE ├── README.md ├── pb ├── dns.pb.go └── dns.proto └── server.go /.gitignore: -------------------------------------------------------------------------------- 1 | # Binaries for programs and plugins 2 | *.exe 3 | *.exe~ 4 | *.dll 5 | *.so 6 | *.dylib 7 | 8 | # Test binary, build with `go test -c` 9 | *.test 10 | 11 | # Output of the go coverage tool, specifically when used with LiteIDE 12 | *.out 13 | -------------------------------------------------------------------------------- /Corefile: -------------------------------------------------------------------------------- 1 | example.com.:1053 { 2 | proxy . 127.0.0.1:8053 { 3 | protocol grpc insecure 4 | } 5 | log 6 | } 7 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright [yyyy] [name of copyright owner] 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Sample gRPC backend for CoreDNS 2 | 3 | #### Generate the gRPC stubs 4 | 5 | This is only needed if [dns.proto](https://github.com/coredns/coredns/blob/master/pb/dns.proto) 6 | is updated: 7 | 8 | ``` 9 | cd proto 10 | protoc dns.proto --go_out=plugins=grpc:. 11 | ``` 12 | 13 | #### Run the server 14 | 15 | This will start the backend on port 8053 (udp/tcp): 16 | 17 | ``` 18 | go build -o main 19 | ./main 20 | ``` 21 | 22 | #### Start CoreDNS 23 | 24 | This will start coredns using the [Corefile](./Corefile) on port 1053 (udp/tcp) 25 | and proxy requests to the backend over gRPC: 26 | 27 | ``` 28 | coredns 29 | ``` 30 | 31 | #### Try it out 32 | 33 | ``` 34 | $ dig +short @localhost -p 1053 A foo.example.com 35 | 127.0.0.1 36 | 37 | $ dig +short @localhost -p 1053 AAAA foo.example.com 38 | ::1 39 | ``` 40 | -------------------------------------------------------------------------------- /pb/dns.pb.go: -------------------------------------------------------------------------------- 1 | // Code generated by protoc-gen-go. DO NOT EDIT. 2 | // source: dns.proto 3 | 4 | package pb 5 | 6 | import proto "github.com/golang/protobuf/proto" 7 | import fmt "fmt" 8 | import math "math" 9 | 10 | import ( 11 | context "golang.org/x/net/context" 12 | grpc "google.golang.org/grpc" 13 | ) 14 | 15 | // Reference imports to suppress errors if they are not otherwise used. 16 | var _ = proto.Marshal 17 | var _ = fmt.Errorf 18 | var _ = math.Inf 19 | 20 | // This is a compile-time assertion to ensure that this generated file 21 | // is compatible with the proto package it is being compiled against. 22 | // A compilation error at this line likely means your copy of the 23 | // proto package needs to be updated. 24 | const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package 25 | 26 | type DnsPacket struct { 27 | Msg []byte `protobuf:"bytes,1,opt,name=msg,proto3" json:"msg,omitempty"` 28 | XXX_NoUnkeyedLiteral struct{} `json:"-"` 29 | XXX_unrecognized []byte `json:"-"` 30 | XXX_sizecache int32 `json:"-"` 31 | } 32 | 33 | func (m *DnsPacket) Reset() { *m = DnsPacket{} } 34 | func (m *DnsPacket) String() string { return proto.CompactTextString(m) } 35 | func (*DnsPacket) ProtoMessage() {} 36 | func (*DnsPacket) Descriptor() ([]byte, []int) { 37 | return fileDescriptor_dns_a16aebd5f2a7a6b7, []int{0} 38 | } 39 | func (m *DnsPacket) XXX_Unmarshal(b []byte) error { 40 | return xxx_messageInfo_DnsPacket.Unmarshal(m, b) 41 | } 42 | func (m *DnsPacket) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) { 43 | return xxx_messageInfo_DnsPacket.Marshal(b, m, deterministic) 44 | } 45 | func (dst *DnsPacket) XXX_Merge(src proto.Message) { 46 | xxx_messageInfo_DnsPacket.Merge(dst, src) 47 | } 48 | func (m *DnsPacket) XXX_Size() int { 49 | return xxx_messageInfo_DnsPacket.Size(m) 50 | } 51 | func (m *DnsPacket) XXX_DiscardUnknown() { 52 | xxx_messageInfo_DnsPacket.DiscardUnknown(m) 53 | } 54 | 55 | var xxx_messageInfo_DnsPacket proto.InternalMessageInfo 56 | 57 | func (m *DnsPacket) GetMsg() []byte { 58 | if m != nil { 59 | return m.Msg 60 | } 61 | return nil 62 | } 63 | 64 | func init() { 65 | proto.RegisterType((*DnsPacket)(nil), "coredns.dns.DnsPacket") 66 | } 67 | 68 | // Reference imports to suppress errors if they are not otherwise used. 69 | var _ context.Context 70 | var _ grpc.ClientConn 71 | 72 | // This is a compile-time assertion to ensure that this generated file 73 | // is compatible with the grpc package it is being compiled against. 74 | const _ = grpc.SupportPackageIsVersion4 75 | 76 | // DnsServiceClient is the client API for DnsService service. 77 | // 78 | // For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream. 79 | type DnsServiceClient interface { 80 | Query(ctx context.Context, in *DnsPacket, opts ...grpc.CallOption) (*DnsPacket, error) 81 | } 82 | 83 | type dnsServiceClient struct { 84 | cc *grpc.ClientConn 85 | } 86 | 87 | func NewDnsServiceClient(cc *grpc.ClientConn) DnsServiceClient { 88 | return &dnsServiceClient{cc} 89 | } 90 | 91 | func (c *dnsServiceClient) Query(ctx context.Context, in *DnsPacket, opts ...grpc.CallOption) (*DnsPacket, error) { 92 | out := new(DnsPacket) 93 | err := c.cc.Invoke(ctx, "/coredns.dns.DnsService/Query", in, out, opts...) 94 | if err != nil { 95 | return nil, err 96 | } 97 | return out, nil 98 | } 99 | 100 | // DnsServiceServer is the server API for DnsService service. 101 | type DnsServiceServer interface { 102 | Query(context.Context, *DnsPacket) (*DnsPacket, error) 103 | } 104 | 105 | func RegisterDnsServiceServer(s *grpc.Server, srv DnsServiceServer) { 106 | s.RegisterService(&_DnsService_serviceDesc, srv) 107 | } 108 | 109 | func _DnsService_Query_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) { 110 | in := new(DnsPacket) 111 | if err := dec(in); err != nil { 112 | return nil, err 113 | } 114 | if interceptor == nil { 115 | return srv.(DnsServiceServer).Query(ctx, in) 116 | } 117 | info := &grpc.UnaryServerInfo{ 118 | Server: srv, 119 | FullMethod: "/coredns.dns.DnsService/Query", 120 | } 121 | handler := func(ctx context.Context, req interface{}) (interface{}, error) { 122 | return srv.(DnsServiceServer).Query(ctx, req.(*DnsPacket)) 123 | } 124 | return interceptor(ctx, in, info, handler) 125 | } 126 | 127 | var _DnsService_serviceDesc = grpc.ServiceDesc{ 128 | ServiceName: "coredns.dns.DnsService", 129 | HandlerType: (*DnsServiceServer)(nil), 130 | Methods: []grpc.MethodDesc{ 131 | { 132 | MethodName: "Query", 133 | Handler: _DnsService_Query_Handler, 134 | }, 135 | }, 136 | Streams: []grpc.StreamDesc{}, 137 | Metadata: "dns.proto", 138 | } 139 | 140 | func init() { proto.RegisterFile("dns.proto", fileDescriptor_dns_a16aebd5f2a7a6b7) } 141 | 142 | var fileDescriptor_dns_a16aebd5f2a7a6b7 = []byte{ 143 | // 120 bytes of a gzipped FileDescriptorProto 144 | 0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0xe2, 0x4c, 0xc9, 0x2b, 0xd6, 145 | 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0xe2, 0x4e, 0xce, 0x2f, 0x4a, 0x05, 0x71, 0x53, 0xf2, 0x8a, 146 | 0x95, 0x64, 0xb9, 0x38, 0x5d, 0xf2, 0x8a, 0x03, 0x12, 0x93, 0xb3, 0x53, 0x4b, 0x84, 0x04, 0xb8, 147 | 0x98, 0x73, 0x8b, 0xd3, 0x25, 0x18, 0x15, 0x18, 0x35, 0x78, 0x82, 0x40, 0x4c, 0x23, 0x57, 0x2e, 148 | 0x2e, 0x97, 0xbc, 0xe2, 0xe0, 0xd4, 0xa2, 0xb2, 0xcc, 0xe4, 0x54, 0x21, 0x73, 0x2e, 0xd6, 0xc0, 149 | 0xd2, 0xd4, 0xa2, 0x4a, 0x21, 0x31, 0x3d, 0x24, 0x33, 0xf4, 0xe0, 0x06, 0x48, 0xe1, 0x10, 0x77, 150 | 0x62, 0x89, 0x62, 0x2a, 0x48, 0x4a, 0x62, 0x03, 0xdb, 0x6f, 0x0c, 0x08, 0x00, 0x00, 0xff, 0xff, 151 | 0xf5, 0xd1, 0x3f, 0x26, 0x8c, 0x00, 0x00, 0x00, 152 | } 153 | -------------------------------------------------------------------------------- /pb/dns.proto: -------------------------------------------------------------------------------- 1 | syntax = "proto3"; 2 | 3 | package coredns.dns; 4 | option go_package = "pb"; 5 | 6 | message DnsPacket { 7 | bytes msg = 1; 8 | } 9 | 10 | service DnsService { 11 | rpc Query (DnsPacket) returns (DnsPacket); 12 | } 13 | -------------------------------------------------------------------------------- /server.go: -------------------------------------------------------------------------------- 1 | // Copyright 2018 Google Inc. 2 | // 3 | // Licensed under the Apache License, Version 2.0 (the "License"); 4 | // you may not use this file except in compliance with the License. 5 | // You may obtain a copy of the License at 6 | // 7 | // https://www.apache.org/licenses/LICENSE-2.0 8 | // 9 | // Unless required by applicable law or agreed to in writing, software 10 | // distributed under the License is distributed on an "AS IS" BASIS, 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | // See the License for the specific language governing permissions and 13 | // limitations under the License. 14 | 15 | package main 16 | 17 | import ( 18 | "context" 19 | "fmt" 20 | "log" 21 | "net" 22 | 23 | "github.com/ahmetb/coredns-grpc-backend-sample/pb" 24 | "github.com/miekg/dns" 25 | "google.golang.org/grpc" 26 | ) 27 | 28 | type dnsServer struct{} 29 | 30 | func (d *dnsServer) Query(ctx context.Context, in *pb.DnsPacket) (*pb.DnsPacket, error) { 31 | m := new(dns.Msg) 32 | if err := m.Unpack(in.Msg); err != nil { 33 | return nil, fmt.Errorf("failed to unpack msg: %v", err) 34 | } 35 | r := new(dns.Msg) 36 | r.SetReply(m) 37 | r.Authoritative = true 38 | 39 | // TODO: query a database and provide real answers here! 40 | for _, q := range r.Question { 41 | hdr := dns.RR_Header{Name: q.Name, Rrtype: q.Qtype, Class: q.Qclass} 42 | switch q.Qtype { 43 | case dns.TypeA: 44 | r.Answer = append(r.Answer, &dns.A{Hdr: hdr, A: net.IPv4(127, 0, 0, 1)}) 45 | case dns.TypeAAAA: 46 | r.Answer = append(r.Answer, &dns.AAAA{Hdr: hdr, AAAA: net.IPv6loopback}) 47 | default: 48 | return nil, fmt.Errorf("only A/AAAA supported, got qtype=%d", q.Qtype) 49 | } 50 | } 51 | 52 | if len(r.Answer) == 0 { 53 | r.Rcode = dns.RcodeNameError 54 | } 55 | 56 | out, err := r.Pack() 57 | if err != nil { 58 | return nil, fmt.Errorf("failed to pack msg: %v", err) 59 | } 60 | return &pb.DnsPacket{Msg: out}, nil 61 | } 62 | 63 | func main() { 64 | lis, err := net.Listen("tcp", ":8053") 65 | if err != nil { 66 | log.Fatalf("failed to listen: %v", err) 67 | } 68 | grpcServer := grpc.NewServer() 69 | pb.RegisterDnsServiceServer(grpcServer, &dnsServer{}) 70 | panic(grpcServer.Serve(lis)) 71 | } 72 | --------------------------------------------------------------------------------