xfrm: pass struct net to xfrm_decode_session wrappers

Preparation patch, extra arg is not used.
No functional changes intended.

This is needed to replace the xfrm session decode functions with
the flow dissector.

skb_flow_dissect() cannot be used as-is, because it attempts to deduce the
'struct net' to use for bpf program fetch from skb->sk or skb->dev, but
xfrm code path can see skbs that have neither sk or dev filled in.

So either flow dissector needs to try harder, e.g. by also trying
skb->dst->dev, or we have to pass the struct net explicitly.

Passing the struct net doesn't look too bad to me, most places
already have it available or can derive it from the output device.

Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://lore.kernel.org/netdev/202309271628.27fd2187-oliver.sang@intel.com/
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

netfilter: nf_nat: mask out non-verdict bits when checking return value

Same as previous change: we need to mask out the non-verdict bits, as
upcoming patches may embed an errno value in NF_STOLEN verdicts too.

NF_DROP could already do this, but not all called functions do this.

Checks that only test ret vs NF_ACCEPT are fine, the 'errno parts'
are always 0 for those.

Signed-off-by: Florian Westphal <fw@strlen.de>

netfilter: nf_nat: undo erroneous tcp edemux lookup after port clash

In commit 03a3ca37e4c6 ("netfilter: nf_nat: undo erroneous tcp edemux lookup")
I fixed a problem with source port clash resolution and DNAT.

A very similar issue exists with REDIRECT (DNAT to local address) and
port rewrites.

Consider two port redirections done at prerouting hook:

-p tcp --port 1111 -j REDIRECT --to-ports 80
-p tcp --port 1112 -j REDIRECT --to-ports 80

Its possible, however unlikely, that we get two connections sharing
the same source port, i.e.

saddr:12345 -> daddr:1111
saddr:12345 -> daddr:1112

This works on sender side because destination address is
different.

After prerouting, nat will change first syn packet to
saddr:12345 -> daddr:80, stack will send a syn-ack back and 3whs
completes.

The second syn however will result in a source port clash:
after dnat rewrite, new syn has

saddr:12345 -> daddr:80

This collides with the reply direction of the first connection.

The NAT engine will handle this in the input nat hook by
also altering the source port, so we get for example

saddr:13535 -> daddr:80

This allows the stack to send back a syn-ack to that address.
Reverse NAT during POSTROUTING will rewrite the packet to
daddr:1112 -> saddr:12345 again. Tuple will be unique on-wire
and peer can process it normally.

Problem is when ACK packet comes in:

After prerouting, packet payload is mangled to saddr:12345 -> daddr:80.
Early demux will assign the 3whs-completing ACK skb to the first
connections' established socket.

This will then elicit a challenge ack from the first connections'
socket rather than complete the connection of the second.
The second connection can never complete.

Detect this condition by checking if the associated sockets port
matches the conntrack entries reply tuple.

If it doesn't, then input source address translation mangled
payload after early demux and the found sk is incorrect.

Discard this sk and let TCP stack do another lookup.

Signed-off-by: Florian Westphal <fw@strlen.de>

netfilter: nat: move nf_xfrm_me_harder to where it is used

remove the export and make it static.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_nat: undo erroneous tcp edemux lookup

Under extremely rare conditions TCP early demux will retrieve the wrong
socket.

1. local machine establishes a connection to a remote server, S, on port
p.

This gives:
laddr:lport -> S:p
... both in tcp and conntrack.

2. local machine establishes a connection to host H, on port p2.
2a. TCP stack choses same laddr:lport, so we have
laddr:lport -> H:p2 from TCP point of view.
2b). There is a destination NAT rewrite in place, translating
H:p2 to S:p. This results in following conntrack entries:

I) laddr:lport -> S:p (origin) S:p -> laddr:lport (reply)
II) laddr:lport -> H:p2 (origin) S:p -> laddr:lport2 (reply)

NAT engine has rewritten laddr:lport to laddr:lport2 to map
the reply packet to the correct origin.

When server sends SYN/ACK to laddr:lport2, the PREROUTING hook
will undo-the SNAT transformation, rewriting IP header to
S:p -> laddr:lport

This causes TCP early demux to associate the skb with the TCP socket
of the first connection.

The INPUT hook will then reverse the DNAT transformation, rewriting
the IP header to H:p2 -> laddr:lport.

Because packet ends up with the wrong socket, the new connection
never completes: originator stays in SYN_SENT and conntrack entry
remains in SYN_RECV until timeout, and responder retransmits SYN/ACK
until it gives up.

To resolve this, orphan the skb after the input rewrite:
Because the source IP address changed, the socket must be incorrect.
We can't move the DNAT undo to prerouting due to backwards
compatibility, doing so will make iptables/nftables rules to no longer
match the way they did.

After orphan, the packet will be handed to the next protocol layer
(tcp, udp, ...) and that will repeat the socket lookup just like as if
early demux was disabled.

Fixes: 41063e9dd1195 ("ipv4: Early TCP socket demux.")
Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1427
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: use actual socket sk rather than skb sk when routing harder

If netfilter changes the packet mark when mangling, the packet is
rerouted using the route_me_harder set of functions. Prior to this
commit, there's one big difference between route_me_harder and the
ordinary initial routing functions, described in the comment above
__ip_queue_xmit():

/* Note: skb->sk can be different from sk, in case of tunnels */
int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,

That function goes on to correctly make use of sk->sk_bound_dev_if,
rather than skb->sk->sk_bound_dev_if. And indeed the comment is true: a
tunnel will receive a packet in ndo_start_xmit with an initial skb->sk.
It will make some transformations to that packet, and then it will send
the encapsulated packet out of a *new* socket. That new socket will
basically always have a different sk_bound_dev_if (otherwise there'd be
a routing loop). So for the purposes of routing the encapsulated packet,
the routing information as it pertains to the socket should come from
that socket's sk, rather than the packet's original skb->sk. For that
reason __ip_queue_xmit() and related functions all do the right thing.

One might argue that all tunnels should just call skb_orphan(skb) before
transmitting the encapsulated packet into the new socket. But tunnels do
*not* do this -- and this is wisely avoided in skb_scrub_packet() too --
because features like TSQ rely on skb->destructor() being called when
that buffer space is truely available again. Calling skb_orphan(skb) too
early would result in buffers filling up unnecessarily and accounting
info being all wrong. Instead, additional routing must take into account
the new sk, just as __ip_queue_xmit() notes.

So, this commit addresses the problem by fishing the correct sk out of
state->sk -- it's already set properly in the call to nf_hook() in
__ip_local_out(), which receives the sk as part of its normal
functionality. So we make sure to plumb state->sk through the various
route_me_harder functions, and then make correct use of it following the
example of __ip_queue_xmit().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: never update the UDP checksum when it's 0

If the UDP header of a local VXLAN endpoint is NAT-ed, and the VXLAN
device has disabled UDP checksums and enabled Tx checksum offloading,
then the skb passed to udp_manip_pkt() has hdr->check == 0 (outer
checksum disabled) and skb->ip_summed == CHECKSUM_PARTIAL (inner packet
checksum offloaded).

Because of the ->ip_summed value, udp_manip_pkt() tries to update the
outer checksum with the new address and port, leading to an invalid
checksum sent on the wire, as the original null checksum obviously
didn't take the old address and port into account.

So, we can't take ->ip_summed into account in udp_manip_pkt(), as it
might not refer to the checksum we're acting on. Instead, we can base
the decision to update the UDP checksum entirely on the value of
hdr->check, because it's null if and only if checksum is disabled:

* A fully computed checksum can't be 0, since a 0 checksum is
represented by the CSUM_MANGLED_0 value instead.

* A partial checksum can't be 0, since the pseudo-header always adds
at least one non-zero value (the UDP protocol type 0x11) and adding
more values to the sum can't make it wrap to 0 as the carry is then
added to the wrapped number.

* A disabled checksum uses the special value 0.

The problem seems to be there from day one, although it was probably
not visible before UDP tunnels were implemented.

Fixes: 5b1158e909ec ("[NETFILTER]: Add NAT support for nf_conntrack")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: fix error handling upon registering inet hook

A case of warning was reported by syzbot.

------------[ cut here ]------------
WARNING: CPU: 0 PID: 19934 at net/netfilter/nf_nat_core.c:1106
nf_nat_unregister_fn+0x532/0x5c0 net/netfilter/nf_nat_core.c:1106
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 19934 Comm: syz-executor.5 Not tainted 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x35 kernel/panic.c:582
report_bug+0x27b/0x2f0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:175 [inline]
fixup_bug arch/x86/kernel/traps.c:170 [inline]
do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:nf_nat_unregister_fn+0x532/0x5c0 net/netfilter/nf_nat_core.c:1106
Code: ff df 48 c1 ea 03 80 3c 02 00 75 75 48 8b 44 24 10 4c 89 ef 48 c7 00 00 00 00 00 e8 e8 f8 53 fb e9 4d fe ff ff e8 ee 9c 16 fb <0f> 0b e9 41 fe ff ff e8 e2 45 54 fb e9 b5 fd ff ff 48 8b 7c 24 20
RSP: 0018:ffffc90005487208 EFLAGS: 00010246
RAX: 0000000000040000 RBX: 0000000000000004 RCX: ffffc9001444a000
RDX: 0000000000040000 RSI: ffffffff865c94a2 RDI: 0000000000000005
RBP: ffff88808b5cf000 R08: ffff8880a2620140 R09: fffffbfff14bcd79
R10: ffffc90005487208 R11: fffffbfff14bcd78 R12: 0000000000000000
R13: 0000000000000001 R14: 0000000000000001 R15: 0000000000000000
nf_nat_ipv6_unregister_fn net/netfilter/nf_nat_proto.c:1017 [inline]
nf_nat_inet_register_fn net/netfilter/nf_nat_proto.c:1038 [inline]
nf_nat_inet_register_fn+0xfc/0x140 net/netfilter/nf_nat_proto.c:1023
nf_tables_register_hook net/netfilter/nf_tables_api.c:224 [inline]
nf_tables_addchain.constprop.0+0x82e/0x13c0 net/netfilter/nf_tables_api.c:1981
nf_tables_newchain+0xf68/0x16a0 net/netfilter/nf_tables_api.c:2235
nfnetlink_rcv_batch+0x83a/0x1610 net/netfilter/nfnetlink.c:433
nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:543 [inline]
nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:561
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6bf/0x7e0 net/socket.c:2362
___sys_sendmsg+0x100/0x170 net/socket.c:2416
__sys_sendmsg+0xec/0x1b0 net/socket.c:2449
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3

and to quiesce it, unregister NFPROTO_IPV6 hook instead of NFPROTO_INET
in case of failing to register NFPROTO_IPV4 hook.

Reported-by: syzbot <syzbot+33e06702fd6cffc24c40@syzkaller.appspotmail.com>
Fixes: d164385ec572 ("netfilter: nat: add inet family nat support")
Cc: Florian Westphal <fw@strlen.de>
Cc: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: fix ICMP header corruption on ICMP errors

Commit 8303b7e8f018 ("netfilter: nat: fix spurious connection timeouts")
made nf_nat_icmp_reply_translation() use icmp_manip_pkt() as the l4
manipulation function for the outer packet on ICMP errors.

However, icmp_manip_pkt() assumes the packet has an 'id' field which
is not correct for all types of ICMP messages.

This is not correct for ICMP error packets, and leads to bogus bytes
being written the ICMP header, which can be wrongfully regarded as
'length' bytes by RFC 4884 compliant receivers.

Fix by assigning the 'id' field only for ICMP messages that have this
semantic.

Reported-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Fixes: 8303b7e8f018 ("netfilter: nat: fix spurious connection timeouts")
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_nat_proto: make tables static

Sparse warns about two tables not being declared.

CHECK net/netfilter/nf_nat_proto.c
net/netfilter/nf_nat_proto.c:725:26: warning: symbol 'nf_nat_ipv4_ops' was not declared. Should it be static?
net/netfilter/nf_nat_proto.c:964:26: warning: symbol 'nf_nat_ipv6_ops' was not declared. Should it be static?

And in fact they can indeed be static.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: Fix remainder of pseudo-header protocol 0

Since v5.1-rc1, some types of packets do not get unreachable reply with the
following iptables setting. Fox example,

$ iptables -A INPUT -p icmp --icmp-type 8 -j REJECT
$ ping 127.0.0.1 -c 1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
— 127.0.0.1 ping statistics —
1 packets transmitted, 0 received, 100% packet loss, time 0ms

We should have got the following reply from command line, but we did not.
From 127.0.0.1 icmp_seq=1 Destination Port Unreachable

Yi Zhao reported it and narrowed it down to:
7fc38225363d ("netfilter: reject: skip csum verification for protocols that don't support it"),

This is because nf_ip_checksum still expects pseudo-header protocol type 0 for
packets that are of neither TCP or UDP, and thus ICMP packets are mistakenly
treated as TCP/UDP.

This patch corrects the conditions in nf_ip_checksum and all other places that
still call it with protocol 0.

Fixes: 7fc38225363d ("netfilter: reject: skip csum verification for protocols that don't support it")
Reported-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

Based on 2 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

netfilter: conntrack, nat: prefer skb_ensure_writable

like previous patches -- convert conntrack to use the core helper.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_tables: merge route type into core

very little code, so it really doesn't make sense to have extra
modules or even a kconfig knob for this.

Merge them and make functionality available unconditionally.
The merge makes inet family route support trivial, so add it
as well here.

Before:
text data bss dec hex filename
835 832 0 1667 683 nft_chain_route_ipv4.ko
870 832 0 1702 6a6 nft_chain_route_ipv6.ko
111568 2556 529 114653 1bfdd nf_tables.ko

After:
text data bss dec hex filename
113133 2556 529 116218 1c5fa nf_tables.ko

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: add inet family nat support

We need minimal support from the nat core for this, as we do not
want to register additional base hooks.

When an inet hook is registered, interally register ipv4 and ipv6
hooks for them and unregister those when inet hooks are removed.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove nf_nat_l3proto.h and nf_nat_core.h

The l3proto name is gone, its header file is the last trace.
While at it, also remove nf_nat_core.h, its very small and all users
include nf_nat.h too.

before:
text data bss dec hex filename
22948 1612 4136 28696 7018 nf_nat.ko

after removal of l3proto register/unregister functions:
text data bss dec hex filename
22196 1516 4136 27848 6cc8 nf_nat.ko

checkpatch complains about overly long lines, but line breaks
do not make things more readable and the line length gets smaller
here, not larger.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove l3proto struct

All l3proto function pointers have been removed.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove csum_recalc hook

We can now use direct calls.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove csum_update hook

We can now use direct calls.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove l3 manip_pkt hook

We can now use direct calls.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove nf_nat_l4proto.h

after ipv4/6 nat tracker merge, there are no external callers, so
make last function static and remove the header.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: merge nf_nat_ipv4,6 into nat core

before:
text data bss dec hex filename
16566 1576 4136 22278 5706 nf_nat.ko
3598 844 0 4442 115a nf_nat_ipv6.ko
3187 844 0 4031 fbf nf_nat_ipv4.ko

after:
text data bss dec hex filename
22948 1612 4136 28696 7018 nf_nat.ko

... with ipv4/v6 nat now provided directly via nf_nat.ko.

Also changes:
ret = nf_nat_ipv4_fn(priv, skb, state);
if (ret != NF_DROP && ret != NF_STOLEN &&
into
if (ret != NF_ACCEPT)
return ret;

everywhere.

The nat hooks never should return anything other than
ACCEPT or DROP (and the latter only in rare error cases).

The original code uses multi-line ANDing including assignment-in-if:
if (ret != NF_DROP && ret != NF_STOLEN &&
!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
(ct = nf_ct_get(skb, &ctinfo)) != NULL) {

I removed this while moving, breaking those in separate conditionals
and moving the assignments into extra lines.

checkpatch still generates some warnings:
1. Overly long lines (of moved code).
Breaking them is even more ugly. so I kept this as-is.
2. use of extern function declarations in a .c file.
This is necessary evil, we must call
nf_nat_l3proto_register() from the nat core now.
All l3proto related functions are removed later in this series,
those prototypes are then removed as well.

v2: keep empty nf_nat_ipv6_csum_update stub for CONFIG_IPV6=n case.
v3: remove IS_ENABLED(NF_NAT_IPV4/6) tests, NF_NAT_IPVx toggles
are removed here.
v4: also get rid of the assignments in conditionals.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove nf_nat_l4proto struct

This removes the (now empty) nf_nat_l4proto struct, all its instances
and all the no longer needed runtime (un)register functionality.

nf_nat_need_gre() can be axed as well: the module that calls it (to
load the no-longer-existing nat_gre module) also calls other nat core
functions. GRE nat is now always available if kernel is built with it.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: remove l4proto->manip_pkt

This removes the last l4proto indirection, the two callers, the l3proto
packet mangling helpers for ipv4 and ipv6, now call the
nf_nat_l4proto_manip_pkt() helper.

nf_nat_proto_{dccp,tcp,sctp,gre,icmp,icmpv6} are left behind, even though
they contain no functionality anymore to not clutter this patch.

Next patch will remove the empty files and the nf_nat_l4proto
struct.

nf_nat_proto_udp.c is renamed to nf_nat_proto.c, as it now contains the
other nat manip functionality as well, not just udp and udplite.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>