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brutella / dnssd

This library implements Multicast DNS (mDNS) and DNS-Based Service Discovery (DNS-SD) for Zero Configuration Networking in Go.
MIT License
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Race condition uncovered during tests #10

Closed daenney closed 4 years ago

daenney commented 5 years ago

I'm using dnssd in a project of mine and I run my tests with the race detector. This surfaced a race in dnssd:

==================
WARNING: DATA RACE
Write at 0x00c00029e0b7 by goroutine 31:
  github.com/brutella/dnssd.(*mdnsConn).readInto.func3()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/mdns.go:260 +0x63

Previous read at 0x00c00029e0b7 by goroutine 29:
  github.com/brutella/dnssd.(*mdnsConn).readInto.func1()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/mdns.go:188 +0x7f

Goroutine 31 (running) created at:
  github.com/brutella/dnssd.(*mdnsConn).readInto()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/mdns.go:258 +0xc7
  github.com/brutella/dnssd.(*mdnsConn).Drain()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/mdns.go:178 +0x1e3
  github.com/brutella/dnssd.probeAtInterface()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:163 +0x9fa
  github.com/brutella/dnssd.probe()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:114 +0x441
  github.com/brutella/dnssd.probeService()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:61 +0x3ae
  github.com/brutella/dnssd.ProbeService()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:38 +0x43d
  github.com/brutella/dnssd.(*responder).register()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/responder.go:185 +0x481
  github.com/brutella/dnssd.(*responder).Respond()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/responder.go:104 +0x20b
  github.com/hemtjanst/fargton/bridge.(*Server).Start.func4()
      /home/daenney/Development/github.com/hemtjanst/fargton/bridge/server.go:226 +0x6e

Goroutine 29 (running) created at:
  github.com/brutella/dnssd.(*mdnsConn).readInto()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/mdns.go:185 +0x13a
  github.com/brutella/dnssd.(*mdnsConn).Drain()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/mdns.go:178 +0x1e3
  github.com/brutella/dnssd.probeAtInterface()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:163 +0x9fa
  github.com/brutella/dnssd.probe()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:114 +0x441
  github.com/brutella/dnssd.probeService()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:61 +0x3ae
  github.com/brutella/dnssd.ProbeService()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/probe.go:38 +0x43d
  github.com/brutella/dnssd.(*responder).register()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/responder.go:185 +0x481
  github.com/brutella/dnssd.(*responder).Respond()
      /home/daenney/Development/go/pkg/mod/github.com/brutella/dnssd@v1.1.0/responder.go:104 +0x20b
  github.com/hemtjanst/fargton/bridge.(*Server).Start.func4()
      /home/daenney/Development/github.com/hemtjanst/fargton/bridge/server.go:226 +0x6e
==================

This happens b/c the isReading var in readInto needs a lock around it to ensure it can safely be modified.

brutella commented 4 years ago

Should be fixed now