johnsonjh/gfpsgo

// Copyright 2021 Jeffrey H. Johnson <trnsz@pobox.com>
// Copyright 2018 psgo 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.

package proc

import (
    "bufio"
    "fmt"
    "io"
    "os"

    "github.com/pkg/errors"
)

// IDMap ...
type IDMap struct {
    ContainerID int
    HostID      int
    Size        int
}

// ParsePIDNamespace returns the content of /proc/$pid/ns/pid.
func ParsePIDNamespace(pid string) (string, error) {
    pidNS, err := os.Readlink(fmt.Sprintf("/proc/%s/ns/pid", pid))
    if err != nil {
        return "", err
    }
    return pidNS, nil
}

// ParseUserNamespace returns the content of /proc/$pid/ns/user.
func ParseUserNamespace(pid string) (string, error) {
    userNS, err := os.Readlink(fmt.Sprintf("/proc/%s/ns/user", pid))
    if err != nil {
        return "", err
    }
    return userNS, nil
}

// ReadMappings reads the user namespace mappings at the specified path
func ReadMappings(path string) ([]IDMap, error) {
    file, err := os.Open(path)
    if err != nil {
        return nil, errors.Wrapf(err, "cannot open %s", path)
    }
    defer file.Close()

    mappings := []IDMap{}

    buf := bufio.NewReader(file)
    for {
        line, _, err := buf.ReadLine()
        if err != nil {
            if err == io.EOF {
                return mappings, nil
            }
            return nil, errors.Wrapf(err, "cannot read line from %s", path)
        }
        if line == nil {
            return mappings, nil
        }

        containerID, hostID, size := 0, 0, 0
        if _, err := fmt.Sscanf(string(line), "%d %d %d", &containerID, &hostID, &size); err != nil {
            return nil, errors.Wrapf(err, "cannot parse %s", string(line))
        }
        mappings = append(
            mappings,
            IDMap{ContainerID: containerID, HostID: hostID, Size: size},
        )
    }
}