102 lines
2.5 KiB
Go
102 lines
2.5 KiB
Go
package libcontainer
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import (
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"github.com/opencontainers/runc/libcontainer/utils"
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)
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type syncType string
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// Constants that are used for synchronisation between the parent and child
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// during container setup. They come in pairs (with procError being a generic
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// response which is followed by a &genericError).
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//
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// [ child ] <-> [ parent ]
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//
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// procHooks --> [run hooks]
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// <-- procResume
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//
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// procReady --> [final setup]
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// <-- procRun
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const (
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procError syncType = "procError"
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procReady syncType = "procReady"
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procRun syncType = "procRun"
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procHooks syncType = "procHooks"
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procResume syncType = "procResume"
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)
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type syncT struct {
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Type syncType `json:"type"`
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}
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// writeSync is used to write to a synchronisation pipe. An error is returned
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// if there was a problem writing the payload.
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func writeSync(pipe io.Writer, sync syncType) error {
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return utils.WriteJSON(pipe, syncT{sync})
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}
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// readSync is used to read from a synchronisation pipe. An error is returned
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// if we got a genericError, the pipe was closed, or we got an unexpected flag.
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func readSync(pipe io.Reader, expected syncType) error {
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var procSync syncT
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if err := json.NewDecoder(pipe).Decode(&procSync); err != nil {
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if err == io.EOF {
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return errors.New("parent closed synchronisation channel")
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}
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return fmt.Errorf("failed reading error from parent: %v", err)
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}
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if procSync.Type == procError {
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var ierr genericError
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if err := json.NewDecoder(pipe).Decode(&ierr); err != nil {
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return fmt.Errorf("failed reading error from parent: %v", err)
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}
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return &ierr
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}
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if procSync.Type != expected {
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return errors.New("invalid synchronisation flag from parent")
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}
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return nil
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}
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// parseSync runs the given callback function on each syncT received from the
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// child. It will return once io.EOF is returned from the given pipe.
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func parseSync(pipe io.Reader, fn func(*syncT) error) error {
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dec := json.NewDecoder(pipe)
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for {
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var sync syncT
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if err := dec.Decode(&sync); err != nil {
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if err == io.EOF {
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break
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}
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return err
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}
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// We handle this case outside fn for cleanliness reasons.
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var ierr *genericError
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if sync.Type == procError {
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if err := dec.Decode(&ierr); err != nil && err != io.EOF {
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return newSystemErrorWithCause(err, "decoding proc error from init")
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}
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if ierr != nil {
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return ierr
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}
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// Programmer error.
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panic("No error following JSON procError payload.")
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}
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if err := fn(&sync); err != nil {
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return err
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}
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}
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return nil
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}
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