proxy: Reset the token status when a shim quits

We close the shim connection when something bad happens:
  - We receive an error trying to write to the socket (most likely
  because the shim died or exited).
  - We have an other kind of unrecoverable error for that client (we
  don't have one right now but we will in the near future)

We now want to progress a bit on the recovery side of things. If the
shim dies, we want to allow it to reconnect and re-claim the session.
This commit does just that.

This is tested by a subsequent unit test: TestShimSendStdinAfterExeccmd

Updates: clearcontainers#4

Signed-off-by: Damien Lespiau <[email protected]>

proxy.go

@@ -548,6 +548,17 @@ func (proxy *proxy) serveNewClient(proto *protocol, newConn net.Conn) {
 		newClient.infof(1, "error serving client: %v", err)
 	}
 
+	// The client was a shim with a session still alive. This means DisconnectShim
+	// hasn't been called and we're closing the connection because of an error
+	// (either us or the shim has closed the connection). We want to keep the
+	// session alive and hope a shim will reconnect claiming the same token.
+	if newClient.session != nil {
+		proxy.Lock()
+		info := proxy.tokenToVM[newClient.token]
+		info.state = tokenStateAllocated
+		proxy.Unlock()
+	}
+
 	newConn.Close()
 	newClient.info(1, "connection closed")
 }