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authorNicolas Lacasse <nlacasse@google.com>2018-10-01 22:05:41 -0700
committerShentubot <shentubot@google.com>2018-10-01 22:06:56 -0700
commitf1c01ed88666ea81d8f5cef7931153a9951a6e64 (patch)
tree796b9812ddda2d7b9866225dabb4b94b058c420b /g3doc
parent0400e5459288592768af12ab71609c6df6afe3d7 (diff)
runsc: Support job control signals in "exec -it".
Terminal support in runsc relies on host tty file descriptors that are imported into the sandbox. Application tty ioctls are sent directly to the host fd. However, those host tty ioctls are associated in the host kernel with a host process (in this case runsc), and the host kernel intercepts job control characters like ^C and send signals to the host process. Thus, typing ^C into a "runsc exec" shell will send a SIGINT to the runsc process. This change makes "runsc exec" handle all signals, and forward them into the sandbox via the "ContainerSignal" urpc method. Since the "runsc exec" is associated with a particular container process in the sandbox, the signal must be associated with the same container process. One big difficulty is that the signal should not necessarily be sent to the sandbox process started by "exec", but instead must be sent to the foreground process group for the tty. For example, we may exec "bash", and from bash call "sleep 100". A ^C at this point should SIGINT sleep, not bash. To handle this, tty files inside the sandbox must keep track of their foreground process group, which is set/get via ioctls. When an incoming ContainerSignal urpc comes in, we look up the foreground process group via the tty file. Unfortunately, this means we have to expose and cache the tty file in the Loader. Note that "runsc exec" now handles signals properly, but "runs run" does not. That will come in a later CL, as this one is complex enough already. Example: root@:/usr/local/apache2# sleep 100 ^C root@:/usr/local/apache2# sleep 100 ^Z [1]+ Stopped sleep 100 root@:/usr/local/apache2# fg sleep 100 ^C root@:/usr/local/apache2# PiperOrigin-RevId: 215334554 Change-Id: I53cdce39653027908510a5ba8d08c49f9cf24f39
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