derp/derphttp: fix nil pointer dereference when closing a netcheck client

NewNetcheckClient only initializes a subset of fields of derphttp.Client,
and the Close() call added by #5707 was result in a nil pointer dereference.
Make Close() safe to call when using NewNetcheckClient() too.

Fixes #5919

Signed-off-by: Mihai Parparita <mihai@tailscale.com>
pull/5926/head
Mihai Parparita 2 years ago committed by Mihai Parparita
parent 4ec6d41682
commit b2855cfd86

@ -96,7 +96,7 @@ func NewRegionClient(privateKey key.NodePrivate, logf logger.Logf, getRegion fun
return c
}
// NewNetcheckClient returns a Client that's only able to have its DialRegion method called.
// NewNetcheckClient returns a Client that's only able to have its DialRegionTLS method called.
// It's used by the netcheck package.
func NewNetcheckClient(logf logger.Logf) *Client {
return &Client{logf: logf}
@ -985,7 +985,9 @@ func (c *Client) isClosed() bool {
// Close closes the client. It will not automatically reconnect after
// being closed.
func (c *Client) Close() error {
if c.cancelCtx != nil {
c.cancelCtx() // not in lock, so it can cancel Connect, which holds mu
}
c.mu.Lock()
defer c.mu.Unlock()

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