dotcloud/docker

//go:build linux

package daemon // import "github.com/docker/docker/daemon"

import (
    "os"
    "strconv"
    "strings"
)

const (
    rootKeyFile   = "/proc/sys/kernel/keys/root_maxkeys"
    rootBytesFile = "/proc/sys/kernel/keys/root_maxbytes"
    rootKeyLimit  = 1000000
    // it is standard configuration to allocate 25 bytes per key
    rootKeyByteMultiplier = 25
)

// modifyRootKeyLimit checks to see if the root key limit is set to
// at least 1000000 and changes it to that limit along with the maxbytes
// allocated to the keys at a 25 to 1 multiplier.
func modifyRootKeyLimit() error {
    value, err := readRootKeyLimit(rootKeyFile)
    if err != nil {
        return err
    }
    if value < rootKeyLimit {
        return setRootKeyLimit(rootKeyLimit)
    }
    return nil
}

func setRootKeyLimit(limit int) error {
    keys, err := os.OpenFile(rootKeyFile, os.O_WRONLY, 0)
    if err != nil {
        return err
    }
    defer keys.Close()
    _, err = keys.WriteString(strconv.Itoa(limit))
    if err != nil {
        return err
    }
    bytes, err := os.OpenFile(rootBytesFile, os.O_WRONLY, 0)
    if err != nil {
        return err
    }
    defer bytes.Close()
    _, err = bytes.WriteString(strconv.Itoa(limit * rootKeyByteMultiplier))
    return err
}

func readRootKeyLimit(path string) (int, error) {
    data, err := os.ReadFile(path)
    if err != nil {
        return -1, err
    }
    return strconv.Atoi(strings.Trim(string(data), "\n"))
}