watchtower/wtdb: create embedded ClientSessionBody

This commit splits out the portions of the ClientSession into an
embedded ClientSessionBody, since these fields will be serialized
together on-disk.

watchtower/wtclient/backup_task.go

@@ -126,8 +126,7 @@ func (t *backupTask) inputs() map[wire.OutPoint]input.Input {
 // SessionInfo's policy. If no error is returned, the task has been bound to the
 // session and can be queued to upload to the tower. Otherwise, the bind failed
 // and should be rescheduled with a different session.
-func (t *backupTask) bindSession(session *wtdb.ClientSession) error {
+func (t *backupTask) bindSession(session *wtdb.ClientSessionBody) error {
-
 	// First we'll begin by deriving a weight estimate for the justice
 	// transaction. The final weight can be different depending on whether
 	// the watchtower is taking a reward.

watchtower/wtclient/backup_task_internal_test.go

@@ -69,7 +69,7 @@ type backupTaskTest struct {
 	expSweepAmt      int64
 	expRewardAmt     int64
 	expRewardScript  []byte
-	session          *wtdb.ClientSession
+	session          *wtdb.ClientSessionBody
 	bindErr          error
 	expSweepScript   []byte
 	signer           input.Signer
@@ -205,7 +205,7 @@ func genTaskTest(
 		expSweepAmt:      expSweepAmt,
 		expRewardAmt:     expRewardAmt,
 		expRewardScript:  rewardScript,
-		session: &wtdb.ClientSession{
+		session: &wtdb.ClientSessionBody{
 			Policy: wtpolicy.Policy{
 				BlobType:     blobType,
 				SweepFeeRate: sweepFeeRate,

watchtower/wtclient/session_negotiator.go

@@ -417,14 +417,15 @@ func (n *sessionNegotiator) tryAddress(privKey *btcec.PrivateKey,
 			privKey.PubKey(),
 		)
 		clientSession := &wtdb.ClientSession{
-			TowerID:        tower.ID,
+			ClientSessionBody: wtdb.ClientSessionBody{
+				TowerID:        tower.ID,
+				KeyIndex:       keyIndex,
+				Policy:         n.cfg.Policy,
+				RewardPkScript: rewardPkScript,
+			},
 			Tower:          tower,
-			KeyIndex:       keyIndex,
 			SessionPrivKey: privKey,
 			ID:             sessionID,
-			Policy:         n.cfg.Policy,
-			SeqNum:         0,
-			RewardPkScript: rewardPkScript,
 		}
 
 		err = n.cfg.DB.CreateClientSession(clientSession)

watchtower/wtclient/session_queue.go

@@ -215,7 +215,7 @@ func (q *sessionQueue) AcceptTask(task *backupTask) (reserveStatus, bool) {
 	//
 	// TODO(conner): queue backups and retry with different session params.
 	case reserveAvailable:
-		err := task.bindSession(q.cfg.ClientSession)
+		err := task.bindSession(&q.cfg.ClientSession.ClientSessionBody)
 		if err != nil {
 			q.queueCond.L.Unlock()
 			log.Debugf("SessionQueue %s rejected backup chanid=%s "+

watchtower/wtdb/client_session.go

@@ -46,8 +46,48 @@ var (
 type ClientSession struct {
 	// ID is the client's public key used when authenticating with the
 	// tower.
+	//
+	// NOTE: This value is not serialized with the body of the struct, it
+	// should be set and recovered as the ClientSession's key.
 	ID SessionID
 
+	ClientSessionBody
+
+	// CommittedUpdates is a sorted list of unacked updates. These updates
+	// can be resent after a restart if the updates failed to send or
+	// receive an acknowledgment.
+	//
+	// NOTE: This list is serialized in it's own bucket, separate from the
+	// body of the ClientSession. The representation on disk is a key value
+	// map from sequence number to CommittedUpdateBody to allow efficient
+	// insertion and retrieval.
+	CommittedUpdates []CommittedUpdate
+
+	// AckedUpdates is a map from sequence number to backup id to record
+	// which revoked states were uploaded via this session.
+	//
+	// NOTE: This map is serialized in it's own bucket, separate from the
+	// body of the ClientSession.
+	AckedUpdates map[uint16]BackupID
+
+	// Tower holds the pubkey and address of the watchtower.
+	//
+	// NOTE: This value is not serialized. It is recovered by looking up the
+	// tower with TowerID.
+	Tower *Tower
+
+	// SessionPrivKey is the ephemeral secret key used to connect to the
+	// watchtower.
+	//
+	// NOTE: This value is not serialized. It is derived using the KeyIndex
+	// on startup to avoid storing private keys on disk.
+	SessionPrivKey *btcec.PrivateKey
+}
+
+// ClientSessionBody represents the primary components of a ClientSession that
+// are serialized together within the database. The CommittedUpdates and
+// AckedUpdates are serialized in buckets separate from the body.
+type ClientSessionBody struct {
 	// SeqNum is the next unallocated sequence number that can be sent to
 	// the tower.
 	SeqNum uint16
@@ -59,25 +99,12 @@ type ClientSession struct {
 	// Tower with which the session is negotiated.
 	TowerID TowerID
 
-	// Tower holds the pubkey and address of the watchtower.
-	//
-	// NOTE: This value is not serialized. It is recovered by looking up the
-	// tower with TowerID.
-	Tower *Tower
-
 	// KeyIndex is the index of key locator used to derive the client's
 	// session key so that it can authenticate with the tower to update its
 	// session. In order to rederive the private key, the key locator should
 	// use the keychain.KeyFamilyTowerSession key family.
 	KeyIndex uint32
 
-	// SessionPrivKey is the ephemeral secret key used to connect to the
-	// watchtower.
-	//
-	// NOTE: This value is not serialized. It is derived using the KeyIndex
-	// on startup to avoid storing private keys on disk.
-	SessionPrivKey *btcec.PrivateKey
-
 	// Policy holds the negotiated session parameters.
 	Policy wtpolicy.Policy
 
@@ -86,14 +113,7 @@ type ClientSession struct {
 	// specifies a reward output.
 	RewardPkScript []byte
 
-	// CommittedUpdates is a sorted list of unacked updates. These updates
-	// can be resent after a restart if the updates failed to send or
-	// receive an acknowledgment.
-	CommittedUpdates []CommittedUpdate
 
-	// AckedUpdates is a map from sequence number to backup id to record
-	// which revoked states were uploaded via this session.
-	AckedUpdates map[uint16]BackupID
 }
 
 // BackupID identifies a particular revoked, remote commitment by channel id and

watchtower/wtmock/client_db.go

@@ -122,13 +122,15 @@ func (m *ClientDB) CreateClientSession(session *wtdb.ClientSession) error {
 	delete(m.indexes, session.TowerID)
 
 	m.activeSessions[session.ID] = &wtdb.ClientSession{
-		TowerID:          session.TowerID,
+		ID: session.ID,
-		KeyIndex:         session.KeyIndex,
+		ClientSessionBody: wtdb.ClientSessionBody{
-		ID:               session.ID,
+			SeqNum:           session.SeqNum,
-		Policy:           session.Policy,
+			TowerLastApplied: session.TowerLastApplied,
-		SeqNum:           session.SeqNum,
+			TowerID:          session.TowerID,
-		TowerLastApplied: session.TowerLastApplied,
+			KeyIndex:         session.KeyIndex,
-		RewardPkScript:   cloneBytes(session.RewardPkScript),
+			Policy:           session.Policy,
+			RewardPkScript:   cloneBytes(session.RewardPkScript),
+		},
 		CommittedUpdates: make([]wtdb.CommittedUpdate, 0),
 		AckedUpdates:     make(map[uint16]wtdb.BackupID),
 	}