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derp/derphttp: avoid endless reconnect race on failure 

Originally from @stablebits (Dmitry Adamushko) in:
https://github.com/tailscale/tailscale/pull/264
pull/296/head
Brad Fitzpatrick 2020-04-11 13:35:02 -07:00
parent 347a926ac4
commit 614eec174f
1 changed files with 14 additions and 4 deletions
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18
derp/derphttp/derphttp_client.go
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@ -240,7 +240,7 @@ func (c *Client) Send(dstKey key.Public, b []byte) error {
return err return err
} }
if err := client.Send(dstKey, b); err != nil { if err := client.Send(dstKey, b); err != nil {
c.closeForReconnect() c.closeForReconnect(client)
} }
return err return err
} }
@ -259,7 +259,7 @@ func (c *Client) NotePreferred(v bool) {
if client != nil { if client != nil {
if err := client.NotePreferred(v); err != nil { if err := client.NotePreferred(v); err != nil {
c.closeForReconnect() c.closeForReconnect(client)
} }
} }
} }
@ -271,7 +271,7 @@ func (c *Client) Recv(b []byte) (derp.ReceivedMessage, error) {
} }
m, err := client.Recv(b) m, err := client.Recv(b)
if err != nil { if err != nil {
c.closeForReconnect() c.closeForReconnect(client)
} }
return m, err return m, err
} }
@ -296,9 +296,19 @@ func (c *Client) Close() error {
// closeForReconnect closes the underlying network connection and // closeForReconnect closes the underlying network connection and
// zeros out the client field so future calls to Connect will // zeros out the client field so future calls to Connect will
// reconnect. // reconnect.
func (c *Client) closeForReconnect() { //
// The provided brokenClient is the client to forget. If current
// client is not brokenClient, closeForReconnect does nothing. (This
// prevents a send and receive goroutine from failing at the ~same
// time and both calling closeForReconnect and the caller goroutines
// forever calling closeForReconnect in lockstep endlessly;
// https://github.com/tailscale/tailscale/pull/264)
func (c *Client) closeForReconnect(brokenClient *derp.Client) {
c.mu.Lock() c.mu.Lock()
defer c.mu.Unlock() defer c.mu.Unlock()
if c.client != brokenClient {
return
}
if c.netConn != nil { if c.netConn != nil {
c.netConn.Close() c.netConn.Close()
c.netConn = nil c.netConn = nil