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authorEduard Zingerman <eddyz87@gmail.com>2026-09-04 17:05:56 -0700
committerAlexei Starovoitov <ast@kernel.org>2026-09-04 18:17:30 -0700
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tree0b07297409b68d2333fb4f0eae7f3b072eb68d4c /Documentation/networking/alias.rst
downloadlinux-stable-506ada89629ec7059b96ecfb0dc7d33ece0103ca.tar.gz
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bpf: mark a NULL kfunc argument precisegrafted
check_kfunc_arg() allows bpf_register_is_null() for nullable arguments w/o marking the underlying scalar register precise. Hence a checkpoint created on such a path would prune against arbitrary scalar value. Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)") Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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+.. SPDX-License-Identifier: GPL-2.0
+
+===========
+IP-Aliasing
+===========
+
+IP-aliases are an obsolete way to manage multiple IP-addresses/masks
+per interface. Newer tools such as iproute2 support multiple
+address/prefixes per interface, but aliases are still supported
+for backwards compatibility.
+
+An alias is formed by adding a colon and a string when running ifconfig.
+This string is usually numeric, but this is not a must.
+
+
+Alias creation
+==============
+
+Alias creation is done by 'magic' interface naming: eg. to create a
+200.1.1.1 alias for eth0 ...
+::
+
+ # ifconfig eth0:0 200.1.1.1 etc,etc....
+ ~~ -> request alias #0 creation (if not yet exists) for eth0
+
+The corresponding route is also set up by this command. Please note:
+The route always points to the base interface.
+
+
+Alias deletion
+==============
+
+The alias is removed by shutting the alias down::
+
+ # ifconfig eth0:0 down
+ ~~~~~~~~~~ -> will delete alias
+
+
+Alias (re-)configuring
+======================
+
+Aliases are not real devices, but programs should be able to configure
+and refer to them as usual (ifconfig, route, etc).
+
+
+Relationship with main device
+=============================
+
+If the base device is shut down the added aliases will be deleted too.