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-rw-r--r--Documentation/admin-guide/sysctl/net.rst52
1 files changed, 50 insertions, 2 deletions
diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index 19408da2390b..c10530624f1e 100644
--- a/Documentation/admin-guide/sysctl/net.rst
+++ b/Documentation/admin-guide/sysctl/net.rst
@@ -40,8 +40,8 @@ Table : Subdirectories in /proc/sys/net
bridge Bridging rose X.25 PLP layer
core General parameter tipc TIPC
ethernet Ethernet protocol unix Unix domain sockets
- ipv4 IP version 4 x25 X.25 protocol
- ipv6 IP version 6
+ ipv4 IP version 4 vsock VSOCK sockets
+ ipv6 IP version 6 x25 X.25 protocol
========= =================== = ========== ===================
1. /proc/sys/net/core - Network core options
@@ -551,3 +551,51 @@ originally may have been issued in the correct sequential order.
If named_timeout is nonzero, failed topology updates will be placed on a defer
queue until another event arrives that clears the error, or until the timeout
expires. Value is in milliseconds.
+
+6. /proc/sys/net/vsock - VSOCK sockets
+--------------------------------------
+
+VSOCK sockets (AF_VSOCK) provide communication between virtual machines and
+their hosts. The behavior of VSOCK sockets in a network namespace is determined
+by the namespace's mode (``global`` or ``local``), which controls how CIDs
+(Context IDs) are allocated and how sockets interact across namespaces.
+
+ns_mode
+-------
+
+Read-only. Reports the current namespace's mode, set at namespace creation
+and immutable thereafter.
+
+Values:
+
+ - ``global`` - the namespace shares system-wide CID allocation and
+ its sockets can reach any VM or socket in any global namespace.
+ Sockets in this namespace cannot reach sockets in local
+ namespaces.
+ - ``local`` - the namespace has private CID allocation and its
+ sockets can only connect to VMs or sockets within the same
+ namespace.
+
+The init_net mode is always ``global``.
+
+child_ns_mode
+-------------
+
+Controls what mode newly created child namespaces will inherit. At namespace
+creation, ``ns_mode`` is inherited from the parent's ``child_ns_mode``. The
+initial value matches the namespace's own ``ns_mode``.
+
+Values:
+
+ - ``global`` - child namespaces will share system-wide CID allocation
+ and their sockets will be able to reach any VM or socket in any
+ global namespace.
+ - ``local`` - child namespaces will have private CID allocation and
+ their sockets will only be able to connect within their own
+ namespace.
+
+Changing ``child_ns_mode`` only affects namespaces created after the change;
+it does not modify the current namespace or any existing children.
+
+A namespace with ``ns_mode`` set to ``local`` cannot change
+``child_ns_mode`` to ``global`` (returns ``-EPERM``).