tailcat_ssh: avoid PTY session hang on slow/interactive shells - #8
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awdemos wants to merge 1 commit into
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tailcat_ssh: avoid PTY session hang on slow/interactive shells#8awdemos wants to merge 1 commit into
awdemos wants to merge 1 commit into
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runWithPTY previously blocked on io.Copy(sess, ptmx) before calling cmd.Wait(). If the shell did not exit immediately, the function would never reach cmd.Wait(), and the deferred ptmx.Close never ran. This could hang the whole SSH session. Restructure the PTY path so cmd.Wait() and the stdout copy run concurrently. When the command exits first, cancel the window-resize goroutine and drain the remaining stdout. When the client disconnects first, kill the shell and wait for it to exit. Also close the pty slave fd after cmd.Start and set tty=nil so the deferred cleanup does not double-close it. Updates tailscale/tailcat (adversarial audit).
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Please file an issue first demonstrating the problem. And this change will need a test update that failed before the change and passes after the change. |
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whoa bradfitz! I haven't worked with you since Six Apart! Good to see you I'll get to this shortly. |
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runWithPTY previously blocked on io.Copy(sess, ptmx) before calling cmd.Wait(). If the shell did not exit immediately, the function would never reach cmd.Wait(), and the deferred ptmx.Close never ran. This could hang the whole SSH session.
Restructure the PTY path so cmd.Wait() and the stdout copy run concurrently. When the command exits first, cancel the window-resize goroutine and drain the remaining stdout. When the client disconnects first, kill the shell and wait for it to exit.
Also close the pty slave fd after cmd.Start and set tty=nil so the deferred cleanup does not double-close it.