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Message-ID: <20251021133918.500380-2-a.melnychenko@vyos.io>
Date: Tue, 21 Oct 2025 15:39:18 +0200
From: Andrii Melnychenko <a.melnychenko@...s.io>
To: pablo@...filter.org,
kadlec@...filter.org,
fw@...len.de,
phil@....cc
Cc: davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
horms@...nel.org,
netfilter-devel@...r.kernel.org,
coreteam@...filter.org,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/1] nft_ct: Added nfct_seqadj_ext_add() for NAT'ed conntrack.
There is an issue with the missed seqadj extension for NAT'ed
conntrack setup with nft. Sequence adjustment may be required
for FTP traffic with PASV/EPSV modes.
The easiest way to reproduce this issue is with PASV mode.
Topoloy:
```
+-------------------+ +----------------------------------+
| FTP: 192.168.13.2 | <-> | NAT: 192.168.13.3, 192.168.100.1 |
+-------------------+ +----------------------------------+
|
+-----------------------+
| Client: 192.168.100.2 |
+-----------------------+
```
nft ruleset:
```
table inet ftp_nat {
ct helper ftp_helper {
type "ftp" protocol tcp
l3proto inet
}
chain prerouting {
type filter hook prerouting priority filter; policy accept;
tcp dport 21 ct state new ct helper set "ftp_helper"
}
}
table ip nat {
chain prerouting {
type nat hook prerouting priority dstnat; policy accept;
tcp dport 21 dnat ip prefix to ip daddr map { 192.168.100.1 : 192.168.13.2/32 }
}
chain postrouting {
type nat hook postrouting priority srcnat; policy accept;
tcp sport 21 snat ip prefix to ip saddr map { 192.168.13.2 : 192.168.100.1/32 }
}
}
```
Connecting the client:
```
Connected to 192.168.100.1.
220 Welcome to my FTP server.
Name (192.168.100.1:dev): user
331 Username ok, send password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> epsv
EPSV/EPRT on IPv4 off.
EPSV/EPRT on IPv6 off.
ftp> ls
227 Entering passive mode (192,168,100,1,209,129).
421 Service not available, remote server has closed connection.
```
Kernel logs:
```
Oct 16 10:24:44 vyos kernel: Missing nfct_seqadj_ext_add() setup call
Oct 16 10:24:44 vyos kernel: WARNING: CPU: 1 PID: 0 at net/netfilter/nf_conntrack_seqadj.c:41 nf_ct_seqadj_set+0xbf/0xe0 [nf_conntrack]
Oct 16 10:24:44 vyos kernel: Modules linked in: nf_nat_ftp(E) nft_nat(E) nf_conntrack_ftp(E) af_packet(E) nft_ct(E) nft_chain_nat(E) nf_nat(E) nf_tables(E) nfnetlink_cthelper(E) nf_conntrack(E) nf_defrag_ipv6(E) nf_defrag_ipv4(E) nfnetlink(E) binfmt_misc(E) intel_rapl_common(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) sha512_ssse3(E) sha256_ssse3(E) sha1_ssse3(E) aesni_intel(E) crypto_simd(E) cryptd(E) rapl(E) iTCO_wdt(E) iTCO_vendor_support(E) button(E) virtio_console(E) virtio_balloon(E) pcspkr(E) evdev(E) tcp_bbr(E) sch_fq_codel(E) mpls_iptunnel(E) mpls_router(E) ip_tunnel(E) br_netfilter(E) bridge(E) stp(E) llc(E) fuse(E) efi_pstore(E) configfs(E) virtio_rng(E) rng_core(E) ip_tables(E) x_tables(E) autofs4(E) usb_storage(E) ohci_hcd(E) uhci_hcd(E) ehci_hcd(E) sd_mod(E) squashfs(E) lz4_decompress(E) loop(E) overlay(E) ext4(E) crc16(E) mbcache(E) jbd2(E) nls_cp437(E) vfat(E) fat(E) efivarfs(E) nls_ascii(E) hid_generic(E) usbhid(E) hid(E) virtio_net(E) net_failover(E) virtio_blk(E) failover(E) ahci(E) libahci(E)
Oct 16 10:24:44 vyos kernel: crc32c_intel(E) i2c_i801(E) i2c_smbus(E) libata(E) lpc_ich(E) scsi_mod(E) scsi_common(E) xhci_pci(E) xhci_hcd(E) virtio_pci(E) virtio_pci_legacy_dev(E) virtio_pci_modern_dev(E) virtio(E) virtio_ring(E)
Oct 16 10:24:44 vyos kernel: CPU: 1 PID: 0 Comm: swapper/1 Tainted: G E 6.6.108-vyos #1
Oct 16 10:24:44 vyos kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Arch Linux 1.17.0-2-2 04/01/2014
Oct 16 10:24:44 vyos kernel: RIP: 0010:nf_ct_seqadj_set+0xbf/0xe0 [nf_conntrack]
Oct 16 10:24:44 vyos kernel: Code: ea 44 89 20 89 50 08 eb db 45 85 ed 74 de 80 3d 51 6d 00 00 00 75 d5 48 c7 c7 68 57 ad c0 c6 05 41 6d 00 00 01 e8 71 28 dd dc <0f> 0b eb be be 02 00 00 00 e8 63 fc ff ff 48 89 c3 e9 66 ff ff ff
Oct 16 10:24:44 vyos kernel: RSP: 0018:ffff9a66c00e8910 EFLAGS: 00010286
Oct 16 10:24:44 vyos kernel: RAX: 0000000000000000 RBX: 0000000000000014 RCX: 000000000000083f
Oct 16 10:24:44 vyos kernel: RDX: 0000000000000000 RSI: 00000000000000f6 RDI: 000000000000083f
Oct 16 10:24:44 vyos kernel: RBP: ffff89387978fb00 R08: 0000000000000000 R09: ffff9a66c00e87a8
Oct 16 10:24:44 vyos kernel: R10: 0000000000000003 R11: ffffffff9ecbab08 R12: ffff89387978fb00
Oct 16 10:24:44 vyos kernel: R13: 0000000000000001 R14: ffff893872e18862 R15: ffff893842f8c700
Oct 16 10:24:44 vyos kernel: FS: 0000000000000000(0000) GS:ffff893bafc80000(0000) knlGS:0000000000000000
Oct 16 10:24:44 vyos kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Oct 16 10:24:44 vyos kernel: CR2: 000055fbc64ec690 CR3: 000000011de22001 CR4: 0000000000370ee0
Oct 16 10:24:44 vyos kernel: Call Trace:
Oct 16 10:24:44 vyos kernel: <IRQ>
Oct 16 10:24:44 vyos kernel: __nf_nat_mangle_tcp_packet+0x100/0x160 [nf_nat]
Oct 16 10:24:44 vyos kernel: nf_nat_ftp+0x142/0x280 [nf_nat_ftp]
Oct 16 10:24:44 vyos kernel: ? kmem_cache_alloc+0x157/0x290
Oct 16 10:24:44 vyos kernel: ? help+0x4d1/0x880 [nf_conntrack_ftp]
Oct 16 10:24:44 vyos kernel: help+0x4d1/0x880 [nf_conntrack_ftp]
Oct 16 10:24:44 vyos kernel: ? nf_confirm+0x122/0x2e0 [nf_conntrack]
Oct 16 10:24:44 vyos kernel: nf_confirm+0x122/0x2e0 [nf_conntrack]
Oct 16 10:24:44 vyos kernel: nf_hook_slow+0x3c/0xb0
Oct 16 10:24:44 vyos kernel: ip_output+0xb6/0xf0
Oct 16 10:24:44 vyos kernel: ? __pfx_ip_finish_output+0x10/0x10
Oct 16 10:24:44 vyos kernel: ip_sublist_rcv_finish+0x90/0xa0
Oct 16 10:24:44 vyos kernel: ip_sublist_rcv+0x190/0x220
Oct 16 10:24:44 vyos kernel: ? __pfx_ip_rcv_finish+0x10/0x10
Oct 16 10:24:44 vyos kernel: ip_list_rcv+0x134/0x160
Oct 16 10:24:44 vyos kernel: __netif_receive_skb_list_core+0x299/0x2c0
Oct 16 10:24:44 vyos kernel: netif_receive_skb_list_internal+0x1a7/0x2d0
Oct 16 10:24:44 vyos kernel: napi_complete_done+0x69/0x1a0
Oct 16 10:24:44 vyos kernel: virtnet_poll+0x3c0/0x540 [virtio_net]
Oct 16 10:24:44 vyos kernel: __napi_poll+0x26/0x1a0
Oct 16 10:24:44 vyos kernel: net_rx_action+0x141/0x2c0
Oct 16 10:24:44 vyos kernel: ? lock_timer_base+0x5c/0x80
Oct 16 10:24:44 vyos kernel: handle_softirqs+0xd5/0x280
Oct 16 10:24:44 vyos kernel: __irq_exit_rcu+0x95/0xb0
Oct 16 10:24:44 vyos kernel: common_interrupt+0x7a/0xa0
Oct 16 10:24:44 vyos kernel: </IRQ>
Oct 16 10:24:44 vyos kernel: <TASK>
Oct 16 10:24:44 vyos kernel: asm_common_interrupt+0x22/0x40
Oct 16 10:24:44 vyos kernel: RIP: 0010:pv_native_safe_halt+0xb/0x10
Oct 16 10:24:44 vyos kernel: Code: 0b 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 90 0f 00 2d 29 9a 3e 00 fb f4 <c3> cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 8b
Oct 16 10:24:44 vyos kernel: RSP: 0018:ffff9a66c009bed8 EFLAGS: 00000252
Oct 16 10:24:44 vyos kernel: RAX: ffff893bafcaaca8 RBX: 0000000000000001 RCX: 0000000000000001
Oct 16 10:24:44 vyos kernel: RDX: 0000000000000000 RSI: 0000000000000083 RDI: 0000000000064cec
Oct 16 10:24:44 vyos kernel: RBP: ffff8938401f2200 R08: 0000000000000001 R09: 0000000000000000
Oct 16 10:24:44 vyos kernel: R10: 000000000001ffc0 R11: 0000000000000000 R12: 0000000000000000
Oct 16 10:24:44 vyos kernel: R13: 0000000000000000 R14: ffff8938401f2200 R15: 0000000000000000
Oct 16 10:24:44 vyos kernel: default_idle+0x5/0x20
Oct 16 10:24:44 vyos kernel: default_idle_call+0x28/0xb0
Oct 16 10:24:44 vyos kernel: do_idle+0x1ec/0x230
Oct 16 10:24:44 vyos kernel: cpu_startup_entry+0x21/0x30
Oct 16 10:24:44 vyos kernel: start_secondary+0x11a/0x140
Oct 16 10:24:44 vyos kernel: secondary_startup_64_no_verify+0x178/0x17b
Oct 16 10:24:44 vyos kernel: </TASK>
```
Fixes: 1a64edf54f55 ("netfilter: nft_ct: add helper set support")
Signed-off-by: Andrii Melnychenko <a.melnychenko@...s.io>
---
net/netfilter/nft_ct.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
index d526e69a2..73d0590fb 100644
--- a/net/netfilter/nft_ct.c
+++ b/net/netfilter/nft_ct.c
@@ -22,6 +22,7 @@
#include <net/netfilter/nf_conntrack_timeout.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_conntrack_seqadj.h>
struct nft_ct_helper_obj {
struct nf_conntrack_helper *helper4;
@@ -1173,6 +1174,9 @@ static void nft_ct_helper_obj_eval(struct nft_object *obj,
if (help) {
rcu_assign_pointer(help->helper, to_assign);
set_bit(IPS_HELPER_BIT, &ct->status);
+
+ if ((ct->status & IPS_NAT_MASK) && !nfct_seqadj(ct))
+ nfct_seqadj_ext_add(ct);
}
}
--
2.43.0
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