github.com/Lephar/snapd@v0.0.0-20210825215435-c7fba9cef4d2/overlord/snapstate/devicectx.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2018-2019 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package snapstate
    21  
    22  import (
    23  	"github.com/snapcore/snapd/asserts"
    24  	"github.com/snapcore/snapd/boot"
    25  	"github.com/snapcore/snapd/overlord/state"
    26  )
    27  
    28  // A DeviceContext provides for operating as a given device and with
    29  // its brand store either for normal operation or over a remodeling.
    30  type DeviceContext interface {
    31  	// GroundContext returns a context corresponding to the
    32  	// original model of the device for a remodel, or a context
    33  	// equivalent to this one otherwise, except in both cases
    34  	// Store cannot be used and must panic.
    35  	GroundContext() DeviceContext
    36  
    37  	// Store returns the store service to use under this context or nil if the snapstate store is appropriate.
    38  	Store() StoreService
    39  
    40  	// ForRemodeling returns whether this context is for use over a remodeling.
    41  	ForRemodeling() bool
    42  
    43  	// SystemMode returns the system  mode (run,install,recover,...).
    44  	SystemMode() string
    45  
    46  	// DeviceContext should be usable as boot.Device
    47  	boot.Device
    48  }
    49  
    50  // Hook setup by devicestate to pick a device context from state,
    51  // optional task or an optionally pre-provided one. It's expected to
    52  // return ErrNoState if a model assertion is not yet known.
    53  var (
    54  	DeviceCtx func(st *state.State, task *state.Task, providedDeviceCtx DeviceContext) (DeviceContext, error)
    55  )
    56  
    57  // Hook setup by devicestate to know whether a remodeling is in progress.
    58  var (
    59  	Remodeling func(st *state.State) bool
    60  )
    61  
    62  // ModelFromTask returns a model assertion through the device context for the task.
    63  func ModelFromTask(task *state.Task) (*asserts.Model, error) {
    64  	deviceCtx, err := DeviceCtx(task.State(), task, nil)
    65  	if err != nil {
    66  		return nil, err
    67  	}
    68  	return deviceCtx.Model(), nil
    69  }
    70  
    71  // DevicePastSeeding returns a device context if a model assertion is
    72  // available and the device is seeded, at that point the device store
    73  // is known and seeding done. Otherwise it returns a
    74  // ChangeConflictError about being too early unless a pre-provided
    75  // DeviceContext is passed in. It will again return a conflict error
    76  // during remodeling unless the providedDeviceCtx is for it.
    77  func DevicePastSeeding(st *state.State, providedDeviceCtx DeviceContext) (DeviceContext, error) {
    78  	var seeded bool
    79  	err := st.Get("seeded", &seeded)
    80  	if err != nil && err != state.ErrNoState {
    81  		return nil, err
    82  	}
    83  	if Remodeling(st) {
    84  		// a remodeling is in progress and this is not called
    85  		// as part of it. The 2nd check should not be needed
    86  		// in practice.
    87  		if providedDeviceCtx == nil || !providedDeviceCtx.ForRemodeling() {
    88  			return nil, &ChangeConflictError{
    89  				Message: "remodeling in progress, no other " +
    90  					"changes allowed until this is done",
    91  				ChangeKind: "remodel",
    92  			}
    93  		}
    94  	}
    95  	devCtx, err := DeviceCtx(st, nil, providedDeviceCtx)
    96  	if err != nil && err != state.ErrNoState {
    97  		return nil, err
    98  	}
    99  	// when seeded devCtx should not be nil except in the rare
   100  	// case of upgrades from a snapd before the introduction of
   101  	// the fallback generic/generic-classic model
   102  	if !seeded || devCtx == nil {
   103  		return nil, &ChangeConflictError{
   104  			Message: "too early for operation, device not yet" +
   105  				" seeded or device model not acknowledged",
   106  			ChangeKind: "seed",
   107  		}
   108  	}
   109  
   110  	return devCtx, nil
   111  }
   112  
   113  // DeviceCtxFromState returns a device context if a model assertion is
   114  // available. Otherwise it returns a ChangeConflictError about being
   115  // too early unless an pre-provided DeviceContext is passed in.
   116  func DeviceCtxFromState(st *state.State, providedDeviceCtx DeviceContext) (DeviceContext, error) {
   117  	deviceCtx, err := DeviceCtx(st, nil, providedDeviceCtx)
   118  	if err != nil {
   119  		if err == state.ErrNoState {
   120  			return nil, &ChangeConflictError{
   121  				Message:    "too early for operation, device model not yet acknowledged",
   122  				ChangeKind: "seed",
   123  			}
   124  		}
   125  		return nil, err
   126  	}
   127  	return deviceCtx, nil
   128  }