package daemon import ( "fmt" "os" "runtime" "syscall" "github.com/criyle/go-sandbox/pkg/unixsocket" ) type containerServer struct { socket *unixsocket.Socket containerConfig } // ContainerConfig set the container config type containerConfig struct { Cred bool } // Init is called for container init process // it will check if pid == 1, otherwise it is noop // Init will do infinite loop on socket commands, // and exits when at socket close, use it in init function func Init() (err error) { // noop if self is not container init process // Notice: docker init is also 1, additional check for args[1] == init if os.Getpid() != 1 || len(os.Args) != 2 || os.Args[1] != initArg { return nil } // exit process (with whole container) upon exit this function // possible reason: // 1. socket broken (parent exit) // 2. panic // 3. undefined cmd (possible race condition) defer func() { if err2 := recover(); err2 != nil { fmt.Fprintf(os.Stderr, "container_panic: %v\n", err) os.Exit(1) } if err != nil { fmt.Fprintf(os.Stderr, "container_exit: %v\n", err) os.Exit(1) } fmt.Fprintf(os.Stderr, "container_exit\n") os.Exit(0) }() // limit container resource usage runtime.GOMAXPROCS(containerMaxProc) // new_master shared the socket at fd 3 (marked close_exec) const defaultFd = 3 soc, err := unixsocket.NewSocket(defaultFd) if err != nil { return fmt.Errorf("container_init: failed to new socket(%v)", err) } // serve forever cs := &containerServer{socket: soc} return cs.serve() } func (c *containerServer) serve() error { for { cmd, msg, err := c.recvCmd() if err != nil { return fmt.Errorf("serve: %v", err) } if err := c.handleCmd(cmd, msg); err != nil { return fmt.Errorf("serve: failed to execute cmd %v", err) } } } func (c *containerServer) handleCmd(cmd *Cmd, msg *unixsocket.Msg) error { switch cmd.Cmd { case cmdPing: return c.handlePing() case cmdConf: return c.handleConf(cmd.ConfCmd) case cmdOpen: return c.handleOpen(cmd.OpenCmd) case cmdDelete: return c.handleDelete(cmd.DeleteCmd) case cmdReset: return c.handleReset() case cmdExecve: return c.handleExecve(cmd.ExecCmd, msg) } return fmt.Errorf("unknown command: %v", cmd.Cmd) } func (c *containerServer) handlePing() error { return c.sendReply(&Reply{}, nil) } func (c *containerServer) handleConf(conf *ConfCmd) error { if conf != nil { c.containerConfig = conf.Conf } return c.sendReply(&Reply{}, nil) } func (c *containerServer) handleOpen(open []OpenCmd) error { if len(open) == 0 { return c.sendErrorReply("open: no open parameter received") } // open files fds := make([]int, 0, len(open)) for _, o := range open { outFile, err := os.OpenFile(o.Path, o.Flag, o.Perm) if err != nil { return c.sendErrorReply("open: %v", err) } defer outFile.Close() fds = append(fds, int(outFile.Fd())) } return c.sendReply(&Reply{}, &unixsocket.Msg{Fds: fds}) } func (c *containerServer) handleDelete(delete *DeleteCmd) error { if delete == nil { return c.sendErrorReply("delete: no parameter provided") } if err := os.Remove(delete.Path); err != nil { return c.sendErrorReply("delete: %v", err) } return c.sendReply(&Reply{}, nil) } func (c *containerServer) handleReset() error { if err := removeContents("/tmp"); err != nil { return c.sendErrorReply("reset: /tmp %v", err) } if err := removeContents("/w"); err != nil { return c.sendErrorReply("reset: /w %v", err) } return c.sendReply(&Reply{}, nil) } func (c *containerServer) recvCmd() (*Cmd, *unixsocket.Msg, error) { cmd := new(Cmd) msg, err := (*socket)(c.socket).RecvMsg(cmd) if err != nil { return nil, nil, err } return cmd, msg, nil } func (c *containerServer) sendReply(reply *Reply, msg *unixsocket.Msg) error { return (*socket)(c.socket).SendMsg(reply, msg) } // sendErrorReply sends error reply func (c *containerServer) sendErrorReply(ft string, v ...interface{}) error { errorReply := &ErrorReply{ Msg: fmt.Sprintf(ft, v...), } // store errno if len(v) == 1 { if errno, ok := v[0].(syscall.Errno); ok { errorReply.Errno = &errno } } return c.sendReply(&Reply{Error: errorReply}, nil) }