Jeremy Kerr says:

====================
MCTP tag control interface

This series implements a small interface for userspace-controlled
message tag allocation for the MCTP protocol. Rather than leaving the
kernel to allocate per-message tag values, userspace can explicitly
allocate (and release) message tags through two new ioctls:
SIOCMCTPALLOCTAG and SIOCMCTPDROPTAG.

In order to do this, we first introduce some minor changes to the tag
handling, including a couple of new tests for the route input paths.

As always, any comments/queries/etc are most welcome.

v2:
 - make mctp_lookup_prealloc_tag static
 - minor checkpatch formatting fixes
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

This change adds a couple of new ioctls for mctp sockets:
SIOCMCTPALLOCTAG and SIOCMCTPDROPTAG.  These ioctls provide facilities
for explicit allocation / release of tags, overriding the automatic
allocate-on-send/release-on-reply and timeout behaviours. This allows
userspace more control over messages that may not fit a simple
request/response model.

In order to indicate a pre-allocated tag to the sendmsg() syscall, we
introduce a new flag to the struct sockaddr_mctp.smctp_tag value:
MCTP_TAG_PREALLOC.

Additional changes from Jeremy Kerr <jk@codeconstruct.com.au>.

Contains a fix that was:
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently, we require an exact match on an incoming packet's dest
address, and the key's local_addr field.

In a future change, we may want to set up a key before packets are
routed, meaning we have no local address to match on.

This change allows key lookups to match on local_addr = MCTP_ADDR_ANY.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently, we have a couple of paths that check that an EID matches, or
the match value is MCTP_ADDR_ANY.

Rather than open coding this, add a little helper.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

This change adds a few more tests to check the key/tag lookups on route
input. We add a specific entry to the keys lists, route a packet with
specific header values, and check for key match/mismatch.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

This is a definition for the tag-owner flag, which has TO as a standard
abbreviation. We'll want to add a helper for the actual tag value in a
future change.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

-queue

Tony Nguyen says:

====================
40GbE Intel Wired LAN Driver Updates 2022-02-08

Joe Damato says:

This patch set makes several updates to the i40e driver stats collection
and reporting code to help users of i40e get a better sense of how the
driver is performing and interacting with the rest of the kernel.

These patches include some new stats (like waived and busy) which were
inspired by other drivers that track stats using the same nomenclature.

The new stats and an existing stat, rx_reuse, are now accessible with
ethtool to make harvesting this data more convenient for users.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Make sure to test that skb has a dst attached to it.

general protection fault, probably for non-canonical address 0xdffffc0000000011: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f]
CPU: 0 PID: 32650 Comm: syz-executor.4 Not tainted 5.17.0-rc2-next-20220204-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ip6_tnl_xmit+0x2140/0x35f0 net/ipv6/ip6_tunnel.c:1127
Code: 4d 85 f6 0f 85 c5 04 00 00 e8 9c b0 66 f9 48 83 e3 fe 48 b8 00 00 00 00 00 fc ff df 48 8d bb 88 00 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 07 7f 05 e8 11 25 b2 f9 44 0f b6 b3 88 00 00
RSP: 0018:ffffc900141b7310 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000c77a000
RDX: 0000000000000011 RSI: ffffffff8811f854 RDI: 0000000000000088
RBP: ffffc900141b7480 R08: 0000000000000000 R09: 0000000000000008
R10: ffffffff8811f846 R11: 0000000000000008 R12: ffffc900141b7548
R13: ffff8880297c6000 R14: 0000000000000000 R15: ffff8880351c8dc0
FS:  00007f9827ba2700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31322000 CR3: 0000000033a70000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ipxip6_tnl_xmit net/ipv6/ip6_tunnel.c:1386 [inline]
 ip6_tnl_start_xmit+0x71e/0x1830 net/ipv6/ip6_tunnel.c:1435
 __netdev_start_xmit include/linux/netdevice.h:4683 [inline]
 netdev_start_xmit include/linux/netdevice.h:4697 [inline]
 xmit_one net/core/dev.c:3473 [inline]
 dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3489
 __dev_queue_xmit+0x2a24/0x3760 net/core/dev.c:4116
 packet_snd net/packet/af_packet.c:3057 [inline]
 packet_sendmsg+0x2265/0x5460 net/packet/af_packet.c:3084
 sock_sendmsg_nosec net/socket.c:705 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:725
 sock_write_iter+0x289/0x3c0 net/socket.c:1061
 call_write_iter include/linux/fs.h:2075 [inline]
 do_iter_readv_writev+0x47a/0x750 fs/read_write.c:726
 do_iter_write+0x188/0x710 fs/read_write.c:852
 vfs_writev+0x1aa/0x630 fs/read_write.c:925
 do_writev+0x27f/0x300 fs/read_write.c:968
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f9828c2d059

Fixes: c1f55c5e ("ip6_tunnel: allow routing IPv4 traffic in NBMA mode")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Qing Deng <i@moy.cat>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

netvsc_device_remove() calls vunmap() inside which should not be
called in the interrupt context. Current code calls hv_unmap_memory()
in the free_netvsc_device() which is rcu callback and maybe called
in the interrupt context. This will trigger BUG_ON(in_interrupt())
in the vunmap(). Fix it via moving hv_unmap_memory() to netvsc_device_
remove().

Fixes: 846da38d ("net: netvsc: Add Isolation VM support for netvsc driver")
Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Tony Nguyen says:

====================
1GbE Intel Wired LAN Driver Updates 2022-02-07

Corinna Vinschen says:

Fix the kernel warning "Missing unregister, handled but fix driver"
when running, e.g.,

  $ ethtool -G eth0 rx 1024

on igc.  Remove memset hack from igb and align igb code to igc.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Document Gigabit Ethernet IP found on RZ/G2UL SoC. Gigabit Ethernet
Interface is identical to one found on the RZ/G2L SoC. No driver changes
are required as generic compatible string "renesas,rzg2l-gbeth" will be
used as a fallback.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Document Gigabit Ethernet IP found on RZ/V2L SoC. Gigabit Ethernet
Interface is identical to one found on the RZ/G2L SoC. No driver changes
are required as generic compatible string "renesas,rzg2l-gbeth" will be
used as a fallback.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20220208053210.14831-1-luizluca@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

The default values for hooks in the driver.pm are NULLs.
Hence drop unused pch_pm_ops.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220207210730.75252-6-andriy.shevchenko@linux.intel.comAcked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

This makes the error handling much more simpler than open-coding everything
and in addition makes the probe function smaller an tidier.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220207210730.75252-5-andriy.shevchenko@linux.intel.comAcked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Eliminate some boilerplate code by using module_pci_driver() instead of
init/exit, and, if needed, moving the salient bits from init into probe.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220207210730.75252-4-andriy.shevchenko@linux.intel.comAcked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

There is already helper functions to do 64-bit I/O on 32-bit machines or
buses, thus we don't need to reinvent the wheel.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220207210730.75252-3-andriy.shevchenko@linux.intel.comAcked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

There is already helper functions to do 64-bit I/O on 32-bit machines or
buses, thus we don't need to reinvent the wheel.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220207210730.75252-2-andriy.shevchenko@linux.intel.comAcked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Use mac_pton() instead of custom approach.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://lore.kernel.org/r/20220207210730.75252-1-andriy.shevchenko@linux.intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Eric Dumazet says:

====================
net: speedup netns dismantles

From: Eric Dumazet <edumazet@google.com>

In this series, I made network namespace deletions more scalable,
by 4x on the little benchmark described in this cover letter.

- Remove bottleneck on ipv6 addrconf, by replacing a global
  hash table to a per netns one.

- Rework many (struct pernet_operations)->exit() handlers to
  exit_batch() ones. This removes many rtnl acquisitions,
  and gives to cleanup_net() kind of a priority over rtnl
  ownership.

Tested on a host with 24 cpus (48 HT)

Test script:

for nr in {1..10}
do
  (for i in {1..10000}; do unshare -n /bin/bash -c "ifconfig lo up"; done) &
done
wait

for i in {1..10}
do
  sleep 1
  echo 3 >/proc/sys/vm/drop_caches
  grep net_namespace /proc/slabinfo
done

Before: We can see host struggles to clean the netns, even after there are no new creations.
Memory cost is high, because each netns consumes a good amount of memory.

time ./unshare10.sh
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      82634  82634   3968    1    1 : tunables   24   12    8 : slabdata  82634  82634      0
net_namespace      37214  37792   3968    1    1 : tunables   24   12    8 : slabdata  37214  37792    192

real	6m57.766s
user	3m37.277s
sys	40m4.826s

After: We can see the script completes much faster,
the kernel thread doing the cleanup_net() keeps up just fine.
Memory cost is not too big.

time ./unshare10.sh
net_namespace       9945   9945   4096    1    1 : tunables   24   12    8 : slabdata   9945   9945      0
net_namespace       4087   4665   4096    1    1 : tunables   24   12    8 : slabdata   4087   4665    192
net_namespace       4082   4607   4096    1    1 : tunables   24   12    8 : slabdata   4082   4607    192
net_namespace        234    761   4096    1    1 : tunables   24   12    8 : slabdata    234    761    192
net_namespace        224    751   4096    1    1 : tunables   24   12    8 : slabdata    224    751    192
net_namespace        218    745   4096    1    1 : tunables   24   12    8 : slabdata    218    745    192
net_namespace        193    667   4096    1    1 : tunables   24   12    8 : slabdata    193    667    172
net_namespace        167    609   4096    1    1 : tunables   24   12    8 : slabdata    167    609    152
net_namespace        167    609   4096    1    1 : tunables   24   12    8 : slabdata    167    609    152
net_namespace        157    609   4096    1    1 : tunables   24   12    8 : slabdata    157    609    152

real    1m43.876s
user    3m39.728s
sys 7m36.342s
====================

Link: https://lore.kernel.org/r/20220208045038.2635826-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

For some reason default_device_ops kept two exit method:

1) default_device_exit() is called for each netns being dismantled in
a cleanup_net() round. This acquires rtnl for each invocation.

2) default_device_exit_batch() is called once with the list of all netns
int the batch, allowing for a single rtnl invocation.

Get rid of the .exit() method to handle the logic from
default_device_exit_batch(), to decrease the number of rtnl acquisition
to one.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

cleanup_net() is competing with other rtnl users.

Batching bond_net_exit() factorizes all rtnl acquistions
to a single one, giving chance for cleanup_net()
to progress much faster, holding rtnl a bit longer.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

cleanup_net() is competing with other rtnl users.

Avoiding to acquire rtnl for each netns before calling
cgw_remove_all_jobs() gives chance for cleanup_net()
to progress much faster, holding rtnl a bit longer.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

cleanup_net() is competing with other rtnl users.

Avoiding to acquire rtnl for each netns before calling
ipmr_rules_exit() gives chance for cleanup_net()
to progress much faster, holding rtnl a bit longer.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

cleanup_net() is competing with other rtnl users.

Avoiding to acquire rtnl for each netns before calling
ip6mr_rules_exit() gives chance for cleanup_net()
to progress much faster, holding rtnl a bit longer.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

cleanup_net() is competing with other rtnl users.

fib6_rules_net_exit() seems a good candidate for exit_batch(),
as this gives chance for cleanup_net() to progress much faster,
holding rtnl a bit longer.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

cleanup_net() is competing with other rtnl users.

Instead of acquiring rtnl at each fib_net_exit() invocation,
add fib_net_exit_batch() so that rtnl is acquired once.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

cleanup_net() is competing with other rtnl users.

nexthop_net_exit() seems a good candidate for exit_batch(),
as this gives chance for cleanup_net() to progress much faster,
holding rtnl a bit longer.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

IPv6 does not scale very well with the number of IPv6 addresses.
It uses a global (shared by all netns) hash table with 256 buckets.

Some functions like addrconf_verify_rtnl() and addrconf_ifdown()
have to iterate all addresses in the hash table.

I have seen addrconf_verify_rtnl() holding the cpu for 10ms or more.

Switch to the per netns hashtable (and spinlock) added
in prior patches.

This considerably speeds up netns dismantle times on hosts
with thousands of netns. This also has an impact
on regular (fast path) IPv6 processing.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Next step for using per netns inet6_addr_lst
is to have per netns work item to ultimately
call addrconf_verify_rtnl() and addrconf_verify()
with a new 'struct net*' argument.

Everything is still using the global inet6_addr_lst[] table.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add a per netns hash table and a dedicated spinlock,
first step to get rid of the global inet6_addr_lst[] one.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Convert one dev_hold()/dev_put() pair in register_netdevice()
and unregister_netdevice_many() to dev_hold_track()
and dev_put_track().

This would allow to detect a rogue dev_put() a bit earlier.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20220207184107.1401096-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

This NIC does not support TSO, it is very unlikely it would
have to send packets with many fragments.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20220208004855.1887345-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Nguyen, Anthony L says:

====================
iwl-next Intel Wired LAN Driver Updates 2022-02-07

Dave adds support for ice driver to provide DSCP QoS mappings to irdma
driver.

[1] https://lore.kernel.org/netdev/20220202191921.1638-1-shiraz.saleem@intel.com/

* 'iwl-next' of git://git.kernel.org/pub/scm/linux/kernel/git/tnguy/linux:
  ice: add support for DSCP QoS for IDC
====================

Link: https://lore.kernel.org/r/20220207235921.1303522-1-anthony.l.nguyen@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

In some cases, pages cannot be reused by i40e because the page is busy. Add
a counter for this event.

Busy page count is accessible via ethtool.
Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

In some cases, pages can not be reused because they are not associated with
the correct NUMA zone. Knowing how often pages are waived helps users to
understand the interaction between the driver's memory usage and their
system.

Pass rx_stats through to i40e_can_reuse_rx_page to allow tracking when
pages are waived.

The page waive count is accessible via ethtool.
Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Add a counter for new page allocations in the i40e RX path. This stat is
accessible with ethtool.
Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

rx page reuse was already being tracked by the i40e driver per RX ring.
Aggregate the counts and make them accessible via ethtool.
Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Page reuse was being tracked from two locations:
  - i40e_reuse_rx_page (via 40e_clean_rx_irq), and
  - i40e_alloc_mapped_page

Remove the double count and only count reuse from i40e_alloc_mapped_page
when the page is about to be reused.
Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Guillaume Nault says:

====================
inet: Separate DSCP from ECN bits using new dscp_t type

The networking stack currently doesn't clearly distinguish between DSCP
and ECN bits. The entire DSCP+ECN bits are stored in u8 variables (or
structure fields), and each part of the stack handles them in their own
way, using different macros. This has created several bugs in the past
and some uncommon code paths are still unfixed.

Such bugs generally manifest by selecting invalid routes because of ECN
bits interfering with FIB routes and rules lookups (more details in the
LPC 2021 talk[1] and in the RFC of this series[2]).

This patch series aims at preventing the introduction of such bugs (and
detecting existing ones), by introducing a dscp_t type, representing
"sanitised" DSCP values (that is, with no ECN information), as opposed
to plain u8 values that contain both DSCP and ECN information. dscp_t
makes it clear for the reader what we're working on, and Sparse can
flag invalid interactions between dscp_t and plain u8.

This series converts only a few variables and structures:

  * Patch 1 converts the tclass field of struct fib6_rule. It
    effectively forbids the use of ECN bits in the tos/dsfield option
    of ip -6 rule. Rules now match packets solely based on their DSCP
    bits, so ECN doesn't influence the result any more. This contrasts
    with the previous behaviour where all 8 bits of the Traffic Class
    field were used. It is believed that this change is acceptable as
    matching ECN bits wasn't usable for IPv4, so only IPv6-only
    deployments could be depending on it. Also the previous behaviour
    made DSCP-based ip6-rules fail for packets with both a DSCP and an
    ECN mark, which is another reason why any such deploy is unlikely.

  * Patch 2 converts the tos field of struct fib4_rule. This one too
    effectively forbids defining ECN bits, this time in ip -4 rule.
    Before that, setting ECN bit 1 was accepted, while ECN bit 0 was
    rejected. But even when accepted, the rule would never match, as
    the packets would have their ECN bits cleared before doing the
    rule lookup.

  * Patch 3 converts the fc_tos field of struct fib_config. This is
    equivalent to patch 2, but for IPv4 routes. Routes using a
    tos/dsfield option with any ECN bit set is now rejected. Before
    this patch, they were accepted but, as with ip4 rules, these routes
    couldn't match any packet, since their ECN bits are cleared before
    the lookup.

  * Patch 4 converts the fa_tos field of struct fib_alias. This one is
    pure internal u8 to dscp_t conversion. While patches 1-3 had user
    facing consequences, this patch shouldn't have any side effect and
    is there to give an overview of what future conversion patches will
    look like. Conversions are quite mechanical, but imply some code
    churn, which is the price for the extra clarity a possibility of
    type checking.

To summarise, all the behaviour changes required for the dscp_t type
approach to work should be contained in patches 1-3. These changes are
edge cases of ip-route and ip-rule that don't currently work properly.
So they should be safe. Also, a kernel selftest is added for each of
them.

Finally, this work also paves the way for allowing the usage of the 3
high order DSCP bits in IPv4 (a few call paths already handle them, but
in general the stack clears them before IPv4 rule and route lookups).

References:
  [1] LPC 2021 talk:
        - https://linuxplumbersconf.org/event/11/contributions/943/
        - Direct link to slide deck:
            https://linuxplumbersconf.org/event/11/contributions/943/attachments/901/1780/inet_tos_lpc2021.pdf
  [2] RFC version of this series:
      - https://lore.kernel.org/netdev/cover.1638814614.git.gnault@redhat.com/
====================

Link: https://lore.kernel.org/r/cover.1643981839.git.gnault@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>