ipv4: Fix user space build failure due to header change

RT_TOS() from include/uapi/linux/in_route.h is defined using
IPTOS_TOS_MASK from include/uapi/linux/ip.h. This is problematic for
files such a

ipv4: Fix user space build failure due to header change

RT_TOS() from include/uapi/linux/in_route.h is defined using
IPTOS_TOS_MASK from include/uapi/linux/ip.h. This is problematic for
files such as include/net/ip_fib.h that want to use RT_TOS() as without
including both header files kernel compilation fails:

In file included from ./include/net/ip_fib.h:25,
from ./include/net/route.h:27,
from ./include/net/lwtunnel.h:9,
from net/core/dst.c:24:
./include/net/ip_fib.h: In function ‘fib_dscp_masked_match’:
./include/uapi/linux/in_route.h:31:32: error: ‘IPTOS_TOS_MASK’ undeclared (first use in this function)
31 | #define RT_TOS(tos) ((tos)&IPTOS_TOS_MASK)
| ^~~~~~~~~~~~~~
./include/net/ip_fib.h:440:45: note: in expansion of macro ‘RT_TOS’
440 | return dscp == inet_dsfield_to_dscp(RT_TOS(fl4->flowi4_tos));

Therefore, cited commit changed linux/in_route.h to include linux/ip.h.
However, as reported by David, this breaks iproute2 compilation due
overlapping definitions between linux/ip.h and
/usr/include/netinet/ip.h:

In file included from ../include/uapi/linux/in_route.h:5,
from iproute.c:19:
../include/uapi/linux/ip.h:25:9: warning: "IPTOS_TOS" redefined
25 | #define IPTOS_TOS(tos) ((tos)&IPTOS_TOS_MASK)
| ^~~~~~~~~
In file included from iproute.c:17:
/usr/include/netinet/ip.h:222:9: note: this is the location of the previous definition
222 | #define IPTOS_TOS(tos) ((tos) & IPTOS_TOS_MASK)

Fix by changing include/net/ip_fib.h to include linux/ip.h. Note that
usage of RT_TOS() should not spread further in the kernel due to recent
work in this area.

Fixes: 1fa3314c14c6 ("ipv4: Centralize TOS matching")
Reported-by: David Ahern <[email protected]>
Closes: https://lore.kernel.org/netdev/[email protected]/
Signed-off-by: Ido Schimmel <[email protected]>
Reviewed-by: David Ahern <[email protected]>
Reviewed-by: Guillaume Nault <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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ipv4: Centralize TOS matching

The TOS field in the IPv4 flow information structure ('flowi4_tos') is
matched by the kernel against the TOS selector in IPv4 rules and routes.
The field is initialized

ipv4: Centralize TOS matching

The TOS field in the IPv4 flow information structure ('flowi4_tos') is
matched by the kernel against the TOS selector in IPv4 rules and routes.
The field is initialized differently by different call sites. Some treat
it as DSCP (RFC 2474) and initialize all six DSCP bits, some treat it as
RFC 1349 TOS and initialize it using RT_TOS() and some treat it as RFC
791 TOS and initialize it using IPTOS_RT_MASK.

What is common to all these call sites is that they all initialize the
lower three DSCP bits, which fits the TOS definition in the initial IPv4
specification (RFC 791).

Therefore, the kernel only allows configuring IPv4 FIB rules that match
on the lower three DSCP bits which are always guaranteed to be
initialized by all call sites:

# ip -4 rule add tos 0x1c table 100
# ip -4 rule add tos 0x3c table 100
Error: Invalid tos.

While this works, it is unlikely to be very useful. RFC 791 that
initially defined the TOS and IP precedence fields was updated by RFC
2474 over twenty five years ago where these fields were replaced by a
single six bits DSCP field.

Extending FIB rules to match on DSCP can be done by adding a new DSCP
selector while maintaining the existing semantics of the TOS selector
for applications that rely on that.

A prerequisite for allowing FIB rules to match on DSCP is to adjust all
the call sites to initialize the high order DSCP bits and remove their
masking along the path to the core where the field is matched on.

However, making this change alone will result in a behavior change. For
example, a forwarded IPv4 packet with a DS field of 0xfc will no longer
match a FIB rule that was configured with 'tos 0x1c'.

This behavior change can be avoided by masking the upper three DSCP bits
in 'flowi4_tos' before comparing it against the TOS selectors in FIB
rules and routes.

Implement the above by adding a new function that checks whether a given
DSCP value matches the one specified in the IPv4 flow information
structure and invoke it from the three places that currently match on
'flowi4_tos'.

Use RT_TOS() for the masking of 'flowi4_tos' instead of IPTOS_RT_MASK
since the latter is not uAPI and we should be able to remove it at some
point.

Include <linux/ip.h> in <linux/in_route.h> since the former defines
IPTOS_TOS_MASK which is used in the definition of RT_TOS() in
<linux/in_route.h>.

No regressions in FIB tests:

# ./fib_tests.sh
[...]
Tests passed: 218
Tests failed: 0

And FIB rule tests:

# ./fib_rule_tests.sh
[...]
Tests passed: 116
Tests failed: 0

Signed-off-by: Ido Schimmel <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>

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License cleanup: add SPDX license identifier to uapi header files with no license

Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine

License cleanup: add SPDX license identifier to uapi header files with no license

Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.

By default are files without license information under the default
license of the kernel, which is GPLV2. Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:

NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".

otherwise syscall usage would not be possible.

Update the files which contain no license information with an SPDX
license identifier. The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception. SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart <[email protected]>
Reviewed-by: Philippe Ombredanne <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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UAPI: (Scripted) Disintegrate include/linux

Signed-off-by: David Howells <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Acked-by: Michae

UAPI: (Scripted) Disintegrate include/linux

Signed-off-by: David Howells <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Acked-by: Michael Kerrisk <[email protected]>
Acked-by: Paul E. McKenney <[email protected]>
Acked-by: Dave Jones <[email protected]>

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