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nspawn: add comments explaining the namespacing situation and the inner/outer children

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This commit is contained in:
Lennart Poettering 2018-07-26 17:26:18 +02:00 committed by Zbigniew Jędrzejewski-Szmek
parent e1a7ab0952
commit b37469d7d1
1 changed files with 16 additions and 0 deletions
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16
src/nspawn/nspawn.c
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@ -2575,6 +2575,17 @@ static int inner_child(
_cleanup_strv_free_ char **env_use = NULL;
int r;
/* This is the "inner" child process, i.e. the one forked off by the "outer" child process, which is the one
* the container manager itself forked off. At the time of clone() it gained its own CLONE_NEWNS, CLONE_NEWPID,
* CLONE_NEWUTS, CLONE_NEWIPC, CLONE_NEWUSER namespaces. Note that it has its own CLONE_NEWNS namespace,
* separate from the CLONE_NEWNS created for the "outer" child, and also separate from the host's CLONE_NEWNS
* namespace. The reason for having two levels of CLONE_NEWNS namespaces is that the "inner" one is owned by
* the CLONE_NEWUSER namespace of the container, while the "outer" one is owned by the host's CLONE_NEWUSER
* namespace.
*
* Note at this point we have no CLONE_NEWNET namespace yet. We'll acquire that one later through
* unshare(). See below. */
assert(barrier);
assert(directory);
assert(kmsg_socket >= 0);
@ -2859,6 +2870,11 @@ static int outer_child(
pid_t pid;
ssize_t l;
/* This is the "outer" child process, i.e the one forked off by the container manager itself. It already has
* its own CLONE_NEWNS namespace (which was created by the clone()). It still lives in the host's CLONE_NEWPID,
* CLONE_NEWUTS, CLONE_NEWIPC, CLONE_NEWUSER and CLONE_NEWNET namespaces. After it completed a number of
* initializations a second child (the "inner" one) is forked off it, and it exits. */
assert(barrier);
assert(directory);
assert(console);