Make containerd work with read-only root
This makes containerd work with a read-only root. There were a few config mistakes on our side which
caused it to write to the rootfs (mostly leftovers from the switch to /ephemeral) and a semi-hardcoded path
in /var/lib/cni from containernetworking/cni. This is technically configurable, but it would require patching
three different repos (see diff message) and getting all of them to agree to take the change and wait for
it to propagate to all repos (containerd is known to be slow to release stuff). So let's just hack in
this one-line diff for the time being.
Test Plan: Should be covered by existing tests
X-Origin-Diff: phab/D694
GitOrigin-RevId: 0e8f5dbfb216539c16e64130af9fe1023722ae1b
diff --git a/third_party/go/patches/containerd-netns-statedir.patch b/third_party/go/patches/containerd-netns-statedir.patch
new file mode 100644
index 0000000..a693eb7
--- /dev/null
+++ b/third_party/go/patches/containerd-netns-statedir.patch
@@ -0,0 +1,96 @@
+Copyright 2020 The Monogon Project Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+
+From 3e7a8cebf9d40487adc7d4a22b5c628add5e7eac Mon Sep 17 00:00:00 2001
+From: Lorenz Brun <lorenz@nexantic.com>
+Date: Wed, 27 Jan 2021 13:05:30 +0100
+Subject: [PATCH] Move netns directory into StateDir
+
+---
+ pkg/netns/netns_unix.go | 12 +++++-------
+ pkg/server/sandbox_run.go | 3 ++-
+ 2 files changed, 7 insertions(+), 8 deletions(-)
+
+diff --git a/pkg/netns/netns_unix.go b/pkg/netns/netns_unix.go
+index 7449e235..b31716cb 100644
+--- a/pkg/netns/netns_unix.go
++++ b/pkg/netns/netns_unix.go
+@@ -48,14 +48,12 @@ import (
+ osinterface "github.com/containerd/cri/pkg/os"
+ )
+
+-const nsRunDir = "/var/run/netns"
+-
+ // Some of the following functions are migrated from
+ // https://github.com/containernetworking/plugins/blob/master/pkg/testutils/netns_linux.go
+
+ // newNS creates a new persistent (bind-mounted) network namespace and returns the
+ // path to the network namespace.
+-func newNS() (nsPath string, err error) {
++func newNS(baseDir string) (nsPath string, err error) {
+ b := make([]byte, 16)
+ if _, err := rand.Reader.Read(b); err != nil {
+ return "", errors.Wrap(err, "failed to generate random netns name")
+@@ -64,13 +62,13 @@ func newNS() (nsPath string, err error) {
+ // Create the directory for mounting network namespaces
+ // This needs to be a shared mountpoint in case it is mounted in to
+ // other namespaces (containers)
+- if err := os.MkdirAll(nsRunDir, 0755); err != nil {
++ if err := os.MkdirAll(baseDir, 0755); err != nil {
+ return "", err
+ }
+
+ // create an empty file at the mount point
+ nsName := fmt.Sprintf("cni-%x-%x-%x-%x-%x", b[0:4], b[4:6], b[6:8], b[8:10], b[10:])
+- nsPath = path.Join(nsRunDir, nsName)
++ nsPath = path.Join(baseDir, nsName)
+ mountPointFd, err := os.Create(nsPath)
+ if err != nil {
+ return "", err
+@@ -164,8 +162,8 @@ type NetNS struct {
+ }
+
+ // NewNetNS creates a network namespace.
+-func NewNetNS() (*NetNS, error) {
+- path, err := newNS()
++func NewNetNS(baseDir string) (*NetNS, error) {
++ path, err := newNS(baseDir)
+ if err != nil {
+ return nil, errors.Wrap(err, "failed to setup netns")
+ }
+diff --git a/pkg/server/sandbox_run.go b/pkg/server/sandbox_run.go
+index dd4c51e3..32a2d6e8 100644
+--- a/pkg/server/sandbox_run.go
++++ b/pkg/server/sandbox_run.go
+@@ -19,6 +19,7 @@ package server
+ import (
+ "encoding/json"
+ "math"
++ "path/filepath"
+ goruntime "runtime"
+ "strings"
+
+@@ -117,7 +118,7 @@ func (c *criService) RunPodSandbox(ctx context.Context, r *runtime.RunPodSandbox
+ // handle. NetNSPath in sandbox metadata and NetNS is non empty only for non host network
+ // namespaces. If the pod is in host network namespace then both are empty and should not
+ // be used.
+- sandbox.NetNS, err = netns.NewNetNS()
++ sandbox.NetNS, err = netns.NewNetNS(filepath.Join(c.config.StateDir, "netns"))
+ if err != nil {
+ return nil, errors.Wrapf(err, "failed to create network namespace for sandbox %q", id)
+ }
+--
+2.25.1
+