For historical reasons, when bridge device is in promisc mode, packets
that are directed to the taps follow bridge input hook path. This patch
adds a workaround to reset conntrack for these packets.

Jianbo Liu reports warning splats in their test infrastructure where
cloned packets reach the br_netfilter input hook to confirm the
conntrack object.

Scratch one bit from BR_INPUT_SKB_CB to annotate that this packet has
reached the input hook because it is passed up to the bridge device to
reach the taps.

[   57.571874] WARNING: CPU: 1 PID: 0 at net/bridge/br_netfilter_hooks.c:616 br_nf_local_in+0x157/0x180 [br_netfilter]
[   57.572749] Modules linked in: xt_MASQUERADE nf_conntrack_netlink nfnetlink iptable_nat xt_addrtype xt_conntrack nf_nat br_netfilter rpcsec_gss_krb5 auth_rpcgss oid_registry overlay rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_isc si ib_umad rdma_cm ib_ipoib iw_cm ib_cm mlx5_ib ib_uverbs ib_core mlx5ctl mlx5_core
[   57.575158] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.8.0+ #19
[   57.575700] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[   57.576662] RIP: 0010:br_nf_local_in+0x157/0x180 [br_netfilter]
[   57.577195] Code: fe ff ff 41 bd 04 00 00 00 be 04 00 00 00 e9 4a ff ff ff be 04 00 00 00 48 89 ef e8 f3 a9 3c e1 66 83 ad b4 00 00 00 04 eb 91 <0f> 0b e9 f1 fe ff ff 0f 0b e9 df fe ff ff 48 89 df e8 b3 53 47 e1
[   57.578722] RSP: 0018:ffff88885f845a08 EFLAGS: 00010202
[   57.579207] RAX: 0000000000000002 RBX: ffff88812dfe8000 RCX: 0000000000000000
[   57.579830] RDX: ffff88885f845a60 RSI: ffff8881022dc300 RDI: 0000000000000000
[   57.580454] RBP: ffff88885f845a60 R08: 0000000000000001 R09: 0000000000000003
[   57.581076] R10: 00000000ffff1300 R11: 0000000000000002 R12: 0000000000000000
[   57.581695] R13: ffff8881047ffe00 R14: ffff888108dbee00 R15: ffff88814519b800
[   57.582313] FS:  0000000000000000(0000) GS:ffff88885f840000(0000) knlGS:0000000000000000
[   57.583040] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   57.583564] CR2: 000000c4206aa000 CR3: 0000000103847001 CR4: 0000000000370eb0
[   57.584194] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[   57.584820] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[   57.585440] Call Trace:
[   57.585721]  <IRQ>
[   57.585976]  ? __warn+0x7d/0x130
[   57.586323]  ? br_nf_local_in+0x157/0x180 [br_netfilter]
[   57.586811]  ? report_bug+0xf1/0x1c0
[   57.587177]  ? handle_bug+0x3f/0x70
[   57.587539]  ? exc_invalid_op+0x13/0x60
[   57.587929]  ? asm_exc_invalid_op+0x16/0x20
[   57.588336]  ? br_nf_local_in+0x157/0x180 [br_netfilter]
[   57.588825]  nf_hook_slow+0x3d/0xd0
[   57.589188]  ? br_handle_vlan+0x4b/0x110
[   57.589579]  br_pass_frame_up+0xfc/0x150
[   57.589970]  ? br_port_flags_change+0x40/0x40
[   57.590396]  br_handle_frame_finish+0x346/0x5e0
[   57.590837]  ? ipt_do_table+0x32e/0x430
[   57.591221]  ? br_handle_local_finish+0x20/0x20
[   57.591656]  br_nf_hook_thresh+0x4b/0xf0 [br_netfilter]
[   57.592286]  ? br_handle_local_finish+0x20/0x20
[   57.592802]  br_nf_pre_routing_finish+0x178/0x480 [br_netfilter]
[   57.593348]  ? br_handle_local_finish+0x20/0x20
[   57.593782]  ? nf_nat_ipv4_pre_routing+0x25/0x60 [nf_nat]
[   57.594279]  br_nf_pre_routing+0x24c/0x550 [br_netfilter]
[   57.594780]  ? br_nf_hook_thresh+0xf0/0xf0 [br_netfilter]
[   57.595280]  br_handle_frame+0x1f3/0x3d0
[   57.595676]  ? br_handle_local_finish+0x20/0x20
[   57.596118]  ? br_handle_frame_finish+0x5e0/0x5e0
[   57.596566]  __netif_receive_skb_core+0x25b/0xfc0
[   57.597017]  ? __napi_build_skb+0x37/0x40
[   57.597418]  __netif_receive_skb_list_core+0xfb/0x220

Fixes: 62e7151a ("netfilter: bridge: confirm multicast packets before passing them up the stack")
Reported-by: Jianbo Liu <jianbol@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>