This change introduces the nsfs file system. Each new namespace allocates
a new nsfs inode.
Here are reasons why we need these inodes:
* each namespace has to have an unique id.
* proc/pid/ns/ contains one entry for each namespace. Bind mounting one of
the files in this directory to somewhere else in the filesystem keeps the
corresponding namespace alive even if all processes currently in
the namespace terminate.
* setns() allows the calling process to join an existing namespace specified
by a file descriptor.
PiperOrigin-RevId: 550694515
Code to get the loopback interface's index is scattered throughout the
syscall tests. Implement the code once and use that in tests (where
applicable).
While I am here, trim the dependencies/includes for network namespace
tests.
PiperOrigin-RevId: 396718124
TCP/IP will work with netstack networking. hostinet doesn't work, and sockets
will have the same behavior as it is now.
Before the userspace is able to create device, the default loopback device can
be used to test.
/proc/net and /sys/net will still be connected to the root network stack; this
is the same behavior now.
Issue #1833
PiperOrigin-RevId: 296309389
Andrei Vagin
Nicolas Lacasse
Ghanan Gowripalan
Ting-Yu Wang
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