Disable DSUSP (Ctrl+Y) on macOS/BSD to prevent session termination (#29)#143
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Disable DSUSP (Ctrl+Y) on macOS/BSD to prevent session termination (#29)#143nix-tkobayashi wants to merge 1 commit into
nix-tkobayashi wants to merge 1 commit into
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On BSD-derived systems, including macOS, the terminal driver treats Ctrl+Y as the DSUSP (delayed suspend) special character even in cbreak mode. While a shell/SSM session is connected, pressing Ctrl+Y triggers a delayed suspend that makes the Stdin read fail with "read /dev/stdin: resource temporarily unavailable", terminating the session. Linux does not implement DSUSP, so it is unaffected. Disable the DSUSP control character (equivalent to the documented `stty dsusp undef` workaround) on darwin/freebsd/netbsd/openbsd via a new per-OS disableDelayedSuspend(), called from disableEchoAndInputBuffering. It is a no-op on linux, where stty rejects the `dsusp` operand. setState now splits its buffer with strings.Fields so multi-token operands like "dsusp undef" are passed to stty as separate arguments; existing callers pass single tokens and are unaffected. Fixes aws#29 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Issue
Fixes #29
On BSD-derived systems, including macOS, pressing Ctrl+Y while a shell / SSM
session is connected terminates the session with:
This also affects
aws ecs execute-command --interactive, which uses SessionManager under the hood. Linux and Windows are not affected.
Root cause
disableEchoAndInputBufferingputs the terminal intocbreak -echo, but on BSDterminals the driver still acts on the DSUSP (delayed suspend) special
character, whose default binding is Ctrl+Y. When pressed, the kernel performs a
delayed suspend and the plugin's
Stdinread fails withEAGAIN("resource temporarily unavailable"), which tears down the session.
The documented workaround in #29 is to run
stty dsusp undeflocally beforeconnecting. This PR applies the equivalent setting from within the plugin.
Change
disableDelayedSuspend():shellsession_bsd.go): runsstty dsusp undef.shellsession_linux.go): no-op, because Linux does not implementDSUSP and
sttyrejects thedsuspoperand.disableEchoAndInputBuffering(BSD/macOS only).setStatenow splits its buffer withstrings.Fields, so multi-token operandssuch as
dsusp undefare passed tosttyas separate arguments. Existingcallers pass single tokens (
cbreak,-echo,echo, and thestty -gblob),so their behavior is unchanged.
Windows is untouched (separate
shellsession_windows.go).Testing
go buildfor linux, darwin (amd64/arm64), freebsd, netbsd, openbsd — all pass.go vetandgofmtclean.go test ./src/sessionmanagerplugin/session/shellsession/passes.Licensing
I confirm this contribution is made under the terms of the Apache 2.0 license.