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exec: expose --preserve-fds #1995

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Merged
mrunalp merged 1 commit into from
Feb 26, 2019
Merged

exec: expose --preserve-fds #1995

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5 changes: 5 additions & 0 deletions exec.go
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,10 @@ following will output a list of processes running in the container:
Usage: "disable the use of the subreaper used to reap reparented processes",
Hidden: true,
},
cli.IntFlag{
Name: "preserve-fds",
Usage: "Pass N additional file descriptors to the container (stdio + $LISTEN_FDS + N in total)",
},
},
Action: func(context *cli.Context) error {
if err := checkArgs(context, 1, minArgs); err != nil {
Expand Down Expand Up @@ -141,6 +145,7 @@ func execProcess(context *cli.Context) (int, error) {
pidFile: context.String("pid-file"),
action: CT_ACT_RUN,
init: false,
preserveFDs: context.Int("preserve-fds"),
}
return r.run(p)
}
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1 change: 1 addition & 0 deletions man/runc-exec.8.md
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Expand Up @@ -28,3 +28,4 @@ following will output a list of processes running in the container:
--no-new-privs set the no new privileges value for the process
--cap value, -c value add a capability to the bounding set for the process
--no-subreaper disable the use of the subreaper used to reap reparented processes
--preserve-fds value pass N additional file descriptors to the container (stdio + $LISTEN_FDS + N in total) (default: 0)
11 changes: 11 additions & 0 deletions tests/integration/exec.bats
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Expand Up @@ -127,3 +127,14 @@ function teardown() {

[[ ${output} == "uid=1000 gid=1000 groups=99(nogroup),100(users)" ]]
}

@test "runc exec --preserve-fds" {
# run busybox detached
runc run -d --console-socket $CONSOLE_SOCKET test_busybox
[ "$status" -eq 0 ]

run bash -c "cat hello > preserve-fds.test; exec 3<preserve-fds.test; $RUNC --log /proc/self/fd/2 --root $ROOT exec --preserve-fds=1 test_busybox cat /proc/self/fd/3"
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@kolyshkin kolyshkin Oct 22, 2020

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What I don't understand is why cat hello is not failing. There is no such file named hello.

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@giuseppe giuseppe Oct 22, 2020

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I guess the error is just ignored but the file is still created by the shell. I guess it had to be echo but too long ago to remember :)

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@kolyshkin kolyshkin Oct 22, 2020

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I mean, yes, cat hello should fail and this is ignored by bash since it does not run with set -e.

What I don't understand is how the check below (that checks that $output contains hello works at all.

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@kolyshkin kolyshkin Oct 22, 2020 •
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@giuseppe pointed out that cat hello produces the message like cat: hello: no such file or directory, and thus the check for hello in the $output succeeds!

[ "$status" -eq 0 ]

[[ "${output}" == *"hello"* ]]
}