sdaveb/avahi2dns-go
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feat: basic app

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This commit is contained in:
Louis Brunner 2021-09-07 20:04:04 +01:00
parent 3e3cac8393
commit cef21c7bc3
7 changed files with 222 additions and 2 deletions
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4
.gitignore vendored
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@ -11,5 +11,5 @@
# Output of the go coverage tool, specifically when used with LiteIDE
*.out
# Dependency directories (remove the comment below to include it)
# vendor/
vendor/
avahi2dns

41
config.go Normal file
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package main
import (
"github.com/alexflint/go-arg"
"github.com/sirupsen/logrus"
)
var defaultDomains = []string{
"home",
"internal",
"intranet",
"lan",
"local",
"private",
"test",
}
type config struct {
Domains []string `arg:"-d" help:"comma-separated list of domains to resolve"`
BindAddr string `arg:"-a,--addr" default:"localhost" help:"address to bind on" env:"BIND"`
Port uint16 `arg:"-p" default:"53" help:"port to bind on" env:"PORT"`
Debug bool `arg:"-v" default:"false" help:"also include debug information"`
}
func parseArgs(logger *logrus.Logger) (*config, error) {
cfg := &config{}
arg.MustParse(cfg)
if len(cfg.Domains) == 0 {
cfg.Domains = defaultDomains
}
configureLogger(logger, cfg)
logger.WithField("config", cfg).Debug("config parsed")
return cfg, nil
}
func configureLogger(logger *logrus.Logger, cfg *config) {
if cfg.Debug {
logger.SetReportCaller(true)
logger.SetLevel(logrus.DebugLevel)
}
}

11
go.mod Normal file
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module github.com/LouisBrunner/avahi2dns
go 1.16
require (
github.com/alexflint/go-arg v1.4.2
github.com/godbus/dbus/v5 v5.0.4
github.com/holoplot/go-avahi v1.0.0
github.com/miekg/dns v1.1.43
github.com/sirupsen/logrus v1.8.1
)

29
go.sum Normal file
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@ -0,0 +1,29 @@
github.com/alexflint/go-arg v1.4.2 h1:lDWZAXxpAnZUq4qwb86p/3rIJJ2Li81EoMbTMujhVa0=
github.com/alexflint/go-arg v1.4.2/go.mod h1:9iRbDxne7LcR/GSvEr7ma++GLpdIU1zrghf2y2768kM=
github.com/alexflint/go-scalar v1.0.0 h1:NGupf1XV/Xb04wXskDFzS0KWOLH632W/EO4fAFi+A70=
github.com/alexflint/go-scalar v1.0.0/go.mod h1:GpHzbCOZXEKMEcygYQ5n/aa4Aq84zbxjy3MxYW0gjYw=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/godbus/dbus/v5 v5.0.4 h1:9349emZab16e7zQvpmsbtjc18ykshndd8y2PG3sgJbA=
github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
github.com/holoplot/go-avahi v1.0.0 h1:PxtsRmfgj5Qkboc0YVXOrgwFPxVuX3GLo4P1swGU+ac=
github.com/holoplot/go-avahi v1.0.0/go.mod h1:qH5psEKb0DK+BRplMfc+RY4VMOlbf6mqfxgpMy6aP0M=
github.com/miekg/dns v1.1.43 h1:JKfpVSCB84vrAmHzyrsxB5NAr5kLoMXZArPSw7Qlgyg=
github.com/miekg/dns v1.1.43/go.mod h1:+evo5L0630/F6ca/Z9+GAqzhjGyn8/c+TBaOyfEl0V4=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/sirupsen/logrus v1.8.1 h1:dJKuHgqk1NNQlqoA6BTlM1Wf9DOH3NBjQyu0h9+AZZE=
github.com/sirupsen/logrus v1.8.1/go.mod h1:yWOB1SBYBC5VeMP7gHvWumXLIWorT60ONWic61uBYv0=
github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 h1:qWPm9rbaAMKs8Bq/9LRpbMqxWRVUAQwMI9fVrssnTfw=
golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210303074136-134d130e1a04 h1:cEhElsAv9LUt9ZUUocxzWe05oFLVd+AA2nstydTeI8g=
golang.org/x/sys v0.0.0-20210303074136-134d130e1a04/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=

22
main.go Normal file
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package main
import (
"os"
"github.com/sirupsen/logrus"
)
func main() {
logger := logrus.New()
cfg, err := parseArgs(logger)
if err != nil {
os.Exit(1)
}
// TODO: add warning if current process doesn't have CAP_NET_BIND_SERVICE?
err = runServer(logger, cfg)
if err != nil {
logger.WithError(err).Fatal("server failed to start")
}
}

64
query.go Normal file
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package main
import (
"fmt"
"log"
"github.com/holoplot/go-avahi"
"github.com/miekg/dns"
"github.com/sirupsen/logrus"
)
func createDNSReply(logger *logrus.Entry, aserver *avahi.Server, r *dns.Msg) *dns.Msg {
m := new(dns.Msg)
m.Compress = false
switch r.Opcode {
case dns.OpcodeQuery:
for _, q := range m.Question {
switch q.Qtype {
case dns.TypeA:
rr, err := avahiToRecord(logger, aserver, q.Name, avahi.ProtoInet, "A")
if err != nil {
logger.WithError(err).Error("avahi A lookup failed, skipping query...")
continue
}
m.Answer = append(m.Answer, rr)
case dns.TypeAAAA:
rr, err := avahiToRecord(logger, aserver, q.Name, avahi.ProtoInet6, "AAAA")
if err != nil {
logger.WithError(err).Error("avahi AAAA lookup failed, skipping query...")
continue
}
m.Answer = append(m.Answer, rr)
default:
logger.WithField("type", q.Qtype).Warning("unsupported question")
}
}
default:
logger.WithField("opcode", r.Opcode).Warning("unsupported opcode")
}
return m
}
func avahiToRecord(logger *logrus.Entry, aserver *avahi.Server, name string, proto int32, recordType string) (dns.RR, error) {
logger.WithFields(logrus.Fields{
"name": name,
"type": recordType,
"protocol": proto,
}).Info("forwarding query to avahi")
hn, err := aserver.ResolveHostName(avahi.InterfaceUnspec, proto, name, avahi.ProtoUnspec, 0)
if err != nil {
return nil, fmt.Errorf("avahi resolve failure: %w", err)
}
log.Println("ResolveHostName:", hn)
rr, err := dns.NewRR(fmt.Sprintf("%s %s %s", name, recordType, hn.Address))
if err != nil {
return nil, fmt.Errorf("failured to create record: %w", err)
}
return rr, err
}

53
server.go Normal file
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package main
import (
"fmt"
"github.com/godbus/dbus/v5"
"github.com/holoplot/go-avahi"
"github.com/miekg/dns"
"github.com/sirupsen/logrus"
)
func runServer(logger *logrus.Logger, cfg *config) error {
// connect to dbus
logger.Debug("connection to dbus...")
conn, err := dbus.SystemBus()
if err != nil {
return fmt.Errorf("connection to dbus failed: %w", err)
}
// connect to avahi server
logger.Debug("connection to avahi through dbus...")
aserver, err := avahi.ServerNew(conn)
if err != nil {
return fmt.Errorf("connection to avahi failed: %w", err)
}
// add dns handlers
handler := func(w dns.ResponseWriter, r *dns.Msg) {
rlogger := logger.WithField("component", "main")
rlogger.WithField("request", r).Debug("received request")
m := createDNSReply(rlogger, aserver, r)
rlogger.WithField("reply", m).Debug("sending reply")
m.SetReply(r)
w.WriteMsg(m)
}
for _, domain := range cfg.Domains {
logger.WithField("domain", domain).Debug("adding dns handler")
dns.HandleFunc(fmt.Sprintf("%s.", domain), handler)
}
// start DNS server
dserver := &dns.Server{
Addr: fmt.Sprintf("%s:%d", cfg.BindAddr, cfg.Port),
Net: "udp",
}
logger.WithField("addr", dserver.Addr).Info("starting DNS server")
err = dserver.ListenAndServe()
defer dserver.Shutdown()
if err != nil {
return fmt.Errorf("failed to start DNS server: %w", err)
}
return nil
}