panic during libnetwork.(*resolver).Start

[bprodoehl]

Seeing this in Docker 1.12.0 after starting and stopping containers at random.

Aug 19 03:13:56 bpdev docker[31958]: panic: runtime error: invalid memory address or nil pointer dereference
Aug 19 03:13:56 bpdev docker[31958]: [signal 0xb code=0x1 addr=0x0 pc=0xdc714e]
Aug 19 03:13:56 bpdev docker[31958]: goroutine 707379 [running]:
Aug 19 03:13:56 bpdev docker[31958]: panic(0x1a74fa0, 0xc82000e090)
Aug 19 03:13:56 bpdev docker[31958]:         /usr/local/go/src/runtime/panic.go:481 +0x3e6
Aug 19 03:13:56 bpdev docker[31958]: github.com/miekg/dns.getUDPSocketName(0x0, 0x0, 0x0, 0x0, 0x0)
Aug 19 03:13:56 bpdev docker[31958]:         /usr/src/docker/vendor/src/github.com/miekg/dns/udp_linux.go:68 +0xce
Aug 19 03:13:56 bpdev docker[31958]: github.com/miekg/dns.setUDPSocketOptions(0x0, 0x0, 0x0)
Aug 19 03:13:56 bpdev docker[31958]:         /usr/src/docker/vendor/src/github.com/miekg/dns/udp.go:23 +0x37
Aug 19 03:13:56 bpdev docker[31958]: github.com/miekg/dns.(*Server).ActivateAndServe(0xc82394a750, 0x0, 0x0)
Aug 19 03:13:56 bpdev docker[31958]:         /usr/src/docker/vendor/src/github.com/miekg/dns/server.go:349 +0x1b7
Aug 19 03:13:56 bpdev docker[31958]: github.com/docker/libnetwork.(*resolver).Start.func1(0xc82394a750)
Aug 19 03:13:56 bpdev docker[31958]:         /usr/src/docker/vendor/src/github.com/docker/libnetwork/resolver.go:122 +0x21
Aug 19 03:13:56 bpdev docker[31958]: created by github.com/docker/libnetwork.(*resolver).Start
Aug 19 03:13:56 bpdev docker[31958]:         /usr/src/docker/vendor/src/github.com/docker/libnetwork/resolver.go:123 +0x2b1

$ docker version
Client:
 Version:      1.12.0
 API version:  1.24
 Go version:   go1.6.3
 Git commit:   8eab29e
 Built:        Thu Jul 28 22:11:10 2016
 OS/Arch:      linux/amd64

Server:
 Version:      1.12.0
 API version:  1.24
 Go version:   go1.6.3
 Git commit:   8eab29e
 Built:        Thu Jul 28 22:11:10 2016
 OS/Arch:      linux/amd64
$ 

$ docker info
Containers: 406
 Running: 0
 Paused: 0
 Stopped: 406
Images: 275
Server Version: 1.12.0
Storage Driver: aufs
 Root Dir: /var/lib/docker/aufs
 Backing Filesystem: extfs
 Dirs: 1222
 Dirperm1 Supported: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge null host overlay
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Security Options: apparmor seccomp
Kernel Version: 4.4.0-31-generic
Operating System: Ubuntu 16.04.1 LTS
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 7.796 GiB
Name: bpdev
ID: 3MHJ:WX6N:WF77:HDFF:35W6:6GPW:4LKL:ZC6A:RNJF:6S7U:6STB:VXCR
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Username: bprodoehl
Registry: https://index.docker.io/v1/
WARNING: No swap limit support
Labels:
 provider=generic
Insecure Registries:
 127.0.0.0/8
$

[bprodoehl]

I think this may be similar to #1117, but I'm seeing this in 1.12.0.

[sanimej]

@bprodoehl Can you give the specific steps you are using that results in this panic ?

[bprodoehl]

I'll try to make a shell script that reproduces it. I see it regularly with a chaos script that uses the API to start or stop a private image at random. Probably the only interesting bits from the create options are that it's a privileged container that gets attached to a bridge-type network named "internet".

  var createOpts = {name: containerName,
                    Image: 'my/privateimage',
                    Tty: true,
                    HostConfig: {Privileged: true, NetworkMode: 'internet'},
                    Hostname: containerName,
                    Env: ['MYVAR='+containerName]};

[sanimej]

@bprodoehl If you were able to recreate it with a script can you share the script ? From the decode I am not able to come up with a clear sequence that can lead to the panic.

Do you have heathcheck enabled in your images ?

[aboch]

Fixed by #1561