Ignore the root container when calculating oom_score_adj for the sandbox.

This is done because the root container for CRI is the infrastructure (pause)
container and always gets a low oom_score_adj. We do this to ensure that only
the oom_score_adj of user containers is used to calculated the sandbox
oom_score_adj.

Implemented in runsc rather than the containerd shim as it's a bit cleaner to
implement here (in the shim it would require overwriting the oomScoreAdj and
re-writing out the config.json again). This processing is Kubernetes(CRI)
specific but we are currently only supporting CRI for multi-container support
anyway.

PiperOrigin-RevId: 267507706

1 files changed, 39 insertions, 0 deletions

diff --git a/runsc/specutils/specutils.go b/runsc/specutils/specutils.go
index 2eec92349..df435f88d 100644
--- a/runsc/specutils/specutils.go
+++ b/runsc/specutils/specutils.go
@@ -23,6 +23,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"syscall"
 	"time"
@@ -503,3 +504,41 @@ func RetryEintr(f func() (uintptr, uintptr, error)) (uintptr, uintptr, error) {
 		}
 	}
 }
+
+// GetOOMScoreAdj reads the given process' oom_score_adj
+func GetOOMScoreAdj(pid int) (int, error) {
+	data, err := ioutil.ReadFile(fmt.Sprintf("/proc/%d/oom_score_adj", pid))
+	if err != nil {
+		return 0, err
+	}
+	return strconv.Atoi(strings.TrimSpace(string(data)))
+}
+
+// GetParentPid gets the parent process ID of the specified PID.
+func GetParentPid(pid int) (int, error) {
+	data, err := ioutil.ReadFile(fmt.Sprintf("/proc/%d/stat", pid))
+	if err != nil {
+		return 0, err
+	}
+
+	var cpid string
+	var name string
+	var state string
+	var ppid int
+	// Parse after the binary name.
+	_, err = fmt.Sscanf(string(data),
+		"%v %v %v %d",
+		// cpid is ignored.
+		&cpid,
+		// name is ignored.
+		&name,
+		// state is ignored.
+		&state,
+		&ppid)
+
+	if err != nil {
+		return 0, err
+	}
+
+	return ppid, nil
+}