Fix successfully unmarshalled nil raw result

[brandond]

Properly handle "null" as plugin output. This successfully unmarshals to a nil map, which crashes later when assigning confVersion to the map. This regression was introduced in #896.

Found when attempting to update multus to v1.1.1; its tests use a dummy plugin output of "null" which causes a panic rather than an error.

  Test Panicked
  assignment to entry in nil map
  /usr/lib/go-1.18/src/runtime/map_faststr.go:205

  Full Stack Trace
  github.com/containernetworking/cni/pkg/invoke.fixupResultVersion({0xc000598000?, 0x18?, 0x1a?}, {0xc000430888, 0x4, 0x8})
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/vendor/github.com/containernetworking/cni/pkg/invoke/exec.go:65 +0x199
  github.com/containernetworking/cni/pkg/invoke.ExecPluginWithResult({0x18e5bc0, 0xc000138000}, {0xc0003a2228, 0x18}, {0xc000598000, 0xc1, 0xd0}, {0x18cf360?, 0xc0002d8780?}, {0x18db748, ...})
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/vendor/github.com/containernetworking/cni/pkg/invoke/exec.go:125 +0x119
  github.com/containernetworking/cni/libcni.(*CNIConfig).addNetwork(0xc0003c6b88, {0x18e5bc0, 0xc000138000}, {0xc0004302f0, 0xe}, {0xc0004302b0, 0x5}, 0xc00038e0e0, {0x0, 0x0}, ...)
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/vendor/github.com/containernetworking/cni/libcni/api.go:414 +0x385
  github.com/containernetworking/cni/libcni.(*CNIConfig).AddNetworkList(0xc00058e000?, {0x18e5bc0, 0xc000138000}, 0xc00034e8a0, 0x0?)
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/vendor/github.com/containernetworking/cni/libcni/api.go:422 +0x10b
  gopkg.in/k8snetworkplumbingwg/multus-cni.v3/pkg/multus.conflistAdd(0xc00034e5a0, {0xc00058e000, 0x76, 0x80}, 0xc00058a000, {0x18db748, 0xc0003e2060})
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/pkg/multus/multus.go:241 +0x30e
  gopkg.in/k8snetworkplumbingwg/multus-cni.v3/pkg/multus.delegateAdd({0x18db748?, 0xc0003e2060}, 0x0, 0x0, 0xc0002b2000, 0xc00034e5a0, 0x1?)
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/pkg/multus/multus.go:331 +0x545
  gopkg.in/k8snetworkplumbingwg/multus-cni.v3/pkg/multus.CmdAdd(0xc000450cb0, {0x18db748?, 0xc0003e2060}, 0x0)
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/pkg/multus/multus.go:626 +0x8ec
  gopkg.in/k8snetworkplumbingwg/multus-cni.v3/pkg/multus.glob..func1.21()
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/pkg/multus/multus_test.go:1283 +0x1a8
  gopkg.in/k8snetworkplumbingwg/multus-cni.v3/pkg/multus.TestMultus(0x0?)
        /var/lib/repos/go/src/github.com/k8snetworkplumbingwg/multus-cni/pkg/multus/multus_test.go:53 +0x90
  testing.tRunner(0xc00038a9c0, 0x178beb0)
        /usr/lib/go-1.18/src/testing/testing.go:1439 +0x102
  created by testing.(*T).Run
        /usr/lib/go-1.18/src/testing/testing.go:1486 +0x35f

Signed-off-by: Brad Davidson [email protected]

[coveralls]

Coverage decreased (-0.06%) to 72.211% when pulling 1c7c696 on brandond:fix_null_output into 812a8cf on containernetworking:main.

[dcbw]

/lgtm

[MikeZappa87]

/lgtm

[brandond]

Anyone have access to merge? Maybe tag a new release?

[MikeZappa87]

@brandond do you need plugins as well? I can get to this later/tomorrow.

[brandond]

I'm honestly not sure! This is my first time contributing.

[dcbw]

@brandond released https://github.com/containernetworking/cni/releases/tag/v1.1.2 with your fix. Thanks!

Runtimes should revendor libcni to get the fix.

[s1061123]

@brandond Thank you for the fix! multus will include it in 4.0.