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tailcat: clean up partially-initialized backends on startup errors #11

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awdemos wants to merge 1 commit into from
+51 −3
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tailcat: clean up partially-initialized backends on startup errors #11

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54 changes: 51 additions & 3 deletions tailcat.go
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Original file line number Diff line number Diff line change
Expand Up @@ -341,7 +341,7 @@ type Server struct {
// first picking defaults for any unset configuration fields: a new
// ephemeral key, log.Printf for logging, and the nearest region of
// the default DERP map.
func (s *Server) Start() error {
func (s *Server) Start() (err error) {
if s.lb != nil {
return errors.New("tailcat: Server.Start called twice")
}
Expand Down Expand Up @@ -392,6 +392,11 @@ func (s *Server) Start() error {
return fmt.Errorf("netmon.New: %w", err)
}
sys.Set(netMon)
defer func() {
if err != nil {
netMon.Close()
}
}()

dialer := &tsdial.Dialer{Logf: logf} // mutated below (before used)
sys.Set(dialer)
Expand Down Expand Up @@ -425,10 +430,23 @@ func (s *Server) Start() error {
if err := createEngine(logf, lb); err != nil {
return fmt.Errorf("createEngine: %w", err)
}
defer func() {
if err != nil {
if e, ok := sys.Engine.GetOK(); ok {
e.Close()
}
}
}()

ns, err := newNetstack(logf, sys)
if err != nil {
return fmt.Errorf("newNetstack: %w", err)
}
defer func() {
if err != nil {
ns.Close()
}
}()
ns.ProcessLocalIPs = true
ns.ProcessSubnets = true
ns.GetTCPHandlerForFlow = func(src, dst netip.AddrPort) (handler func(net.Conn), intercept bool) {
Expand Down Expand Up @@ -466,8 +484,16 @@ func (s *Server) Start() error {
sys.Tun.Get().Start()

s.lb = lb
defer func() {
if err != nil {
s.lb = nil
}
}()
sys.Engine.Get().SetFilter(s.buildFilter())
return lb.Start()
if err := lb.Start(); err != nil {
return fmt.Errorf("lb.Start: %w", err)
}
return nil
}

var allTCPPorts = filter.PortRange{First: 0, Last: 65535}
Expand Down Expand Up @@ -1440,7 +1466,7 @@ func NewClient(server ConnBlob) *Client {
// netstack) on first use, with defaults for unset config fields. It
// does no network access; that happens in ensureStarted, its caller.
// c.startMu must be held.
func (c *Client) initLocked() error {
func (c *Client) initLocked() (err error) {
if c.lb != nil {
return nil
}
Expand Down Expand Up @@ -1470,6 +1496,11 @@ func (c *Client) initLocked() error {
return fmt.Errorf("netmon.New: %w", err)
}
sys.Set(netMon)
defer func() {
if err != nil {
netMon.Close()
}
}()

dialer := &tsdial.Dialer{Logf: logf} // mutated below (before used)
sys.Set(dialer)
Expand Down Expand Up @@ -1498,10 +1529,23 @@ func (c *Client) initLocked() error {
if err := createEngine(logf, lb); err != nil {
return fmt.Errorf("createEngine: %w", err)
}
defer func() {
if err != nil {
if e, ok := sys.Engine.GetOK(); ok {
e.Close()
}
}
}()

ns, err := newNetstack(logf, sys)
if err != nil {
return fmt.Errorf("newNetstack: %w", err)
}
defer func() {
if err != nil {
ns.Close()
}
}()
ns.ProcessLocalIPs = true // required to even reply to TCP SYNs client sends out
ns.GetTCPHandlerForFlow = func(src, dst netip.AddrPort) (handler func(net.Conn), intercept bool) {
return nil, true // don't accept any incoming connections to client
Expand Down Expand Up @@ -1594,6 +1638,10 @@ func (c *Client) ensureStarted(ctx context.Context) error {
mak.Set(&c.lb.dm.Regions, r.RegionID, r)
}
if err := c.lb.Start(); err != nil {
// Start failed; discard the partially-initialized backend so the
// next call retries from scratch rather than reusing a broken one.
c.lb.Close()
c.lb = nil
return err
}
c.started = true
Expand Down