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authorRaimo Niskanen <[email protected]>2013-07-19 15:18:42 +0200
committerRaimo Niskanen <[email protected]>2013-07-19 15:18:42 +0200
commitaf112cb10613d422080785621a274a18d96567c0 (patch)
treebec1e5c8405c92489e89980646ed5085db94c01b /lib/kernel
parent184e421b08feeae294cd4e629853a45ca640937f (diff)
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Document socket option 'netns'
Diffstat (limited to 'lib/kernel')
-rw-r--r--lib/kernel/doc/src/inet.xml53
1 files changed, 53 insertions, 0 deletions
diff --git a/lib/kernel/doc/src/inet.xml b/lib/kernel/doc/src/inet.xml
index 7cd98914d1..650ab41c3e 100644
--- a/lib/kernel/doc/src/inet.xml
+++ b/lib/kernel/doc/src/inet.xml
@@ -715,6 +715,59 @@ fe80::204:acff:fe17:bf38
<p>Received <c>Packet</c> is delivered as defined by Mode.</p>
</item>
+ <tag><c>{netns, Namespace :: file:filename_all()}</c></tag>
+ <item>
+ <p>Set a network namespace for the socket. The <c>Namespace</c>
+ parameter is a filename defining the namespace for example
+ <c>"/var/run/netns/example"</c> typically created by the command
+ <c>ip netns add example</c>. This option must be used in a
+ function call that creates a socket i.e
+ <seealso marker="gen_tcp#connect/3">
+ gen_tcp:connect/3,4</seealso>,
+ <seealso marker="gen_tcp#listen/2">
+ gen_tcp:listen/2</seealso>,
+ <seealso marker="gen_udp#open/1">
+ gen_udp:open/1,2</seealso> or
+ <seealso marker="gen_sctp#open/0">
+ gen_sctp:open/0-2</seealso>.
+ </p>
+ <p>This option uses the Linux specific syscall
+ <c>setns()</c> such as in Linux kernel 3.0 or later
+ and therefore only exists when the runtime system
+ has been compiled for such an operating system.
+ </p>
+ <p>
+ The virtual machine also needs elevated privileges either
+ running as superuser or (for Linux) having the capability
+ <c>CAP_SYS_ADMIN</c> according to the documentation for setns(2).
+ However, during testing also <c>CAP_SYS_PTRACE</c>
+ and <c>CAP_DAC_READ_SEARCH</c> has proven to be necessary.
+ Example:<code>
+setcap cap_sys_admin,cap_sys_ptrace,cap_dac_read_search+epi beam.smp
+</code>
+ Note also that the filesystem containing the virtual machine
+ executable (<c>beam.smp</c> in the example above) has to be local,
+ mounted without the <c>nosetuid</c> flag,
+ support extended attributes and that
+ the kernel has to support file capabilities.
+ All this runs out of the box on at least Ubuntu 12.04 LTS,
+ except that SCTP sockets appears to not support
+ network namespaces.
+ </p>
+ <p>The <c>Namespace</c> is a file name and is encoded
+ and decoded as discussed in
+ <seealso marker="file">file</seealso>
+ except that the emulator flag <c>+fnu</c> is ignored and
+ <seealso marker="#getopts/2">getopts/2</seealso>
+ for this option will return a binary for the filename
+ if the stored filename can not be decoded,
+ which should only happen if you set the option using a binary
+ that can not be decoded with the emulator's filename encoding:
+ <seealso marker="file#native_name_encoding/0">
+ file:native_name_encoding/0</seealso>.
+ </p>
+ </item>
+
<tag><c>list</c></tag>
<item>
<p>Received <c>Packet</c> is delivered as a list.</p>