Bug 217826 - Since 6.1: flow_dissector.c __skb_flow_dissect+0xa91/0x1cd0 raises WARNING in specific circumstances
Summary: Since 6.1: flow_dissector.c __skb_flow_dissect+0xa91/0x1cd0 raises WARNING in...
Status: NEW
Alias: None
Product: Networking
Classification: Unclassified
Component: Other (show other bugs)
Hardware: All Linux
: P3 low
Assignee: Stephen Hemminger
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2023-08-26 12:35 UTC by stephane.poignant
Modified: 2023-08-30 03:54 UTC (History)
2 users (show)

See Also:
Kernel Version:
Subsystem:
Regression: No
Bisected commit-id:

Attachments
pass netns pointer to flow dissector to avoid warn splat (1.94 KB, patch)
2023-08-29 18:39 UTC, Florian Westphal 		Details | Diff
Add an attachment (proposed patch, testcase, etc.)

Description stephane.poignant 2023-08-26 12:35:09 UTC 
## Overall description

After migration from kernel 5.10 to 6.1, i started to encounter the following warning although they do not seem to have any significant functional impact.
Following further investigation, it appears that the warning appears when both of the following conditions are:
 - At least one policy based routing rules with L4 selectors (among others, L3 matchers and fwmark DO NOT trigger the issue)
 - A nftable or iptable filtering policy with at least one action rejecting traffic with TCP reset (drop action, or reject with ICMP unreachable DO NOT trigger)

The first time a packet matches the reject policy, and that a RST segment is forged and sent, a kernel WARNING as follows will show up in the dmesg:
```
WARNING: CPU: 0 PID: 0 at net/core/flow_dissector.c:1016 __skb_flow_dissect+0xa91/0x1cd0
```

Traffic does not appear to be affected, including the RST segment that is reliably delivered in spite of the WARNING.


## Expected behaviour

The warning should not appear, in this particular setup the namespace of the RST packet should be resolved to the default one.


## Reproducing steps

The following minimalistic configuration will reproduce the issue:

- Running last 6.1 "vanilla" kernel at the time of writing:
```
root@v-debian12:~# uname -a
Linux v-debian12 6.1.47 #1 SMP PREEMPT_DYNAMIC Fri Aug 25 13:23:01 CEST 2023 x86_64 GNU/Linux
```
NB: Issue won't happen on different 5.10 kernels that i tried

- A routing policy with a rule that uses L4 selectors:
```
root@v-debian12:~# cat /etc/iproute2/rt_tables.d/wanalt.conf
100 wanalt

root@v-debian12:~# ip rule ls
0:	from all lookup local
100:	from all ipproto udp dport 27000-27999 lookup wanalt
32766:	from all lookup main
32767:	from all lookup default

root@v-debian12:~# ip route ls
default via 192.168.56.1 dev enp0s8
192.168.56.0/24 dev enp0s8 proto kernel scope link src 192.168.56.3

root@v-debian12:~# ip route ls table wanalt
default via 192.168.56.2 dev enp0s8
```

- A nftables or iptables rules that rejects some traffic with tcp reset:
```
root@v-debian12:~# nft list ruleset
table inet filter {
	chain input {
		type filter hook input priority filter; policy accept;
		tcp dport 12345 log reject with tcp reset
	}

	chain output {
		type filter hook output priority filter; policy accept;
		tcp sport 12345 tcp flags rst / fin,syn,rst log
	}
}
```
(NB: the rule in thhhe output chain is only for debugging purpose, it let us see what packet caused the warning in the dmesg)

- from another VM, we attempt to connect to port 12345 on the reproducing host:
```
root@v-debian11:~# nc 192.168.56.3 12345
```

- the following appears in the dmesg of the reproducing host:
```
# the packet that matched the reject rule
2023-08-26T14:04:35.619764+02:00 v-debian12 kernel: [ 3335.550250] IN=enp0s8 OUT= MAC=08:00:27:76:64:62:08:00:27:69:c9:e5:08:00 SRC=192.168.56.4 DST=192.168.56.3 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=30150 DF PROTO=TCP SPT=48576 DPT=12345 WINDOW=64240 RES=0x00 SYN URGP=0

# the warning showing up
2023-08-26T14:04:35.619791+02:00 v-debian12 kernel: [ 3335.550267] ------------[ cut here ]------------
2023-08-26T14:04:35.619793+02:00 v-debian12 kernel: [ 3335.550269] WARNING: CPU: 0 PID: 0 at net/core/flow_dissector.c:1016 __skb_flow_dissect+0xa91/0x1cd0
2023-08-26T14:04:35.619795+02:00 v-debian12 kernel: [ 3335.550277] Modules linked in: nf_log_syslog(E) nft_reject_inet(E) nf_reject_ipv4(E) nf_reject_ipv6(E) nft_reject(E) nft_log(E) nf_tables(E) libcrc32c(E) nfnetlink(E) intel_rapl_msr(E) intel_rapl_common(E) intel_pmc_core(E) intel_powerclamp(E) ghash_clmulni_intel(E) sha512_ssse3(E) sha512_generic(E) vmwgfx(E) aesni_intel(E) drm_ttm_helper(E) snd_pcm(E) crypto_simd(E) iTCO_wdt(E) cryptd(E) intel_pmc_bxt(E) ttm(E) iTCO_vendor_support(E) rapl(E) watchdog(E) snd_timer(E) drm_kms_helper(E) snd(E) joydev(E) soundcore(E) vboxguest(E) pcspkr(E) rng_core(E) ac(E) button(E) evdev(E) serio_raw(E) sg(E) binfmt_misc(E) drm(E) fuse(E) dm_mod(E) loop(E) efi_pstore(E) configfs(E) ip_tables(E) x_tables(E) autofs4(E) ext4(E) crc32c_generic(E) crc16(E) mbcache(E) jbd2(E) sd_mod(E) t10_pi(E) crc64_rocksoft(E) crc64(E) crc_t10dif(E) sr_mod(E) cdrom(E) crct10dif_generic(E) ata_generic(E) ahci(E) libahci(E) ata_piix(E) crct10dif_pclmul(E) crct10dif_common(E) crc32_pclmul(E) crc32c_intel(E) psmouse(E)
2023-08-26T14:04:35.619796+02:00 v-debian12 kernel: [ 3335.550336]  libata(E) scsi_mod(E) scsi_common(E) lpc_ich(E) i2c_piix4(E) e1000(E) battery(E) video(E) wmi(E)
2023-08-26T14:04:35.619797+02:00 v-debian12 kernel: [ 3335.550345] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G            E      6.1.47 #1
2023-08-26T14:04:35.619797+02:00 v-debian12 kernel: [ 3335.550348] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
2023-08-26T14:04:35.619798+02:00 v-debian12 kernel: [ 3335.550350] RIP: 0010:__skb_flow_dissect+0xa91/0x1cd0
2023-08-26T14:04:35.619799+02:00 v-debian12 kernel: [ 3335.550354] Code: 00 bf 02 00 00 00 49 89 0c 12 66 89 78 02 41 8b 55 00 e9 e7 f6 ff ff 49 8b 44 24 18 48 85 c0 74 09 4c 8b 78 30 e9 30 f7 ff ff <0f> 0b e9 f6 f7 ff ff f6 c2 20 0f 84 e4 f6 ff ff 41 0f b7 45 0e 4c
2023-08-26T14:04:35.619809+02:00 v-debian12 kernel: [ 3335.550356] RSP: 0018:ffffc130800036b0 EFLAGS: 00010246
2023-08-26T14:04:35.619810+02:00 v-debian12 kernel: [ 3335.550358] RAX: 0000000000000000 RBX: 0000000000000008 RCX: ffffc13080003810
2023-08-26T14:04:35.619811+02:00 v-debian12 kernel: [ 3335.550360] RDX: ffffffff94240e40 RSI: ffff9b53c770ee00 RDI: 0000000000000000
2023-08-26T14:04:35.619812+02:00 v-debian12 kernel: [ 3335.550361] RBP: ffffc13080003798 R08: 0000000000000000 R09: 0000000000000000
2023-08-26T14:04:35.619813+02:00 v-debian12 kernel: [ 3335.550363] R10: ffffc13080003810 R11: ffff9b53e812ba80 R12: ffff9b53c770ee00
2023-08-26T14:04:35.619814+02:00 v-debian12 kernel: [ 3335.550364] R13: ffffffff94240e40 R14: ffff9b53c6456080 R15: 0000000000000000
2023-08-26T14:04:35.619814+02:00 v-debian12 kernel: [ 3335.550366] FS:  0000000000000000(0000) GS:ffff9b53fdc00000(0000) knlGS:0000000000000000
2023-08-26T14:04:35.619815+02:00 v-debian12 kernel: [ 3335.550368] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
2023-08-26T14:04:35.619816+02:00 v-debian12 kernel: [ 3335.550369] CR2: 00007ffdda939440 CR3: 000000004d326005 CR4: 00000000000706f0
2023-08-26T14:04:35.619817+02:00 v-debian12 kernel: [ 3335.550371] Call Trace:
2023-08-26T14:04:35.619817+02:00 v-debian12 kernel: [ 3335.550374]  <IRQ>
2023-08-26T14:04:35.619818+02:00 v-debian12 kernel: [ 3335.550378]  ? __warn+0x7d/0xc0
2023-08-26T14:04:35.619819+02:00 v-debian12 kernel: [ 3335.550382]  ? __skb_flow_dissect+0xa91/0x1cd0
2023-08-26T14:04:35.619820+02:00 v-debian12 kernel: [ 3335.550385]  ? report_bug+0xe6/0x170
2023-08-26T14:04:35.619821+02:00 v-debian12 kernel: [ 3335.550388]  ? handle_bug+0x41/0x70
2023-08-26T14:04:35.619821+02:00 v-debian12 kernel: [ 3335.550391]  ? exc_invalid_op+0x13/0x60
2023-08-26T14:04:35.619822+02:00 v-debian12 kernel: [ 3335.550393]  ? asm_exc_invalid_op+0x16/0x20
2023-08-26T14:04:35.619832+02:00 v-debian12 kernel: [ 3335.550397]  ? __skb_flow_dissect+0xa91/0x1cd0
2023-08-26T14:04:35.619833+02:00 v-debian12 kernel: [ 3335.550401]  ? __inet_dev_addr_type+0xe8/0x180
2023-08-26T14:04:35.619834+02:00 v-debian12 kernel: [ 3335.550405]  ip_route_me_harder+0x143/0x330
2023-08-26T14:04:35.619835+02:00 v-debian12 kernel: [ 3335.550411]  nf_send_reset+0x17c/0x2d0 [nf_reject_ipv4]
2023-08-26T14:04:35.619835+02:00 v-debian12 kernel: [ 3335.550417]  nft_reject_inet_eval+0xa9/0xf2 [nft_reject_inet]
2023-08-26T14:04:35.619836+02:00 v-debian12 kernel: [ 3335.550422]  nft_do_chain+0x198/0x5d0 [nf_tables]
2023-08-26T14:04:35.619837+02:00 v-debian12 kernel: [ 3335.550439]  nft_do_chain_inet+0xa4/0x110 [nf_tables]
2023-08-26T14:04:35.619838+02:00 v-debian12 kernel: [ 3335.550454]  nf_hook_slow+0x41/0xc0
2023-08-26T14:04:35.619838+02:00 v-debian12 kernel: [ 3335.550458]  ip_local_deliver+0xce/0x110
2023-08-26T14:04:35.619839+02:00 v-debian12 kernel: [ 3335.550461]  ? ip_protocol_deliver_rcu+0x230/0x230
2023-08-26T14:04:35.619840+02:00 v-debian12 kernel: [ 3335.550464]  ip_sublist_rcv_finish+0x7e/0x90
2023-08-26T14:04:35.619840+02:00 v-debian12 kernel: [ 3335.550466]  ip_sublist_rcv+0x183/0x230
2023-08-26T14:04:35.619841+02:00 v-debian12 kernel: [ 3335.550468]  ? __netif_receive_skb_core.constprop.0+0xaf/0xf00
2023-08-26T14:04:35.619842+02:00 v-debian12 kernel: [ 3335.550472]  ip_list_rcv+0x139/0x170
2023-08-26T14:04:35.619843+02:00 v-debian12 kernel: [ 3335.550475]  __netif_receive_skb_list_core+0x29e/0x2c0
2023-08-26T14:04:35.619843+02:00 v-debian12 kernel: [ 3335.550479]  netif_receive_skb_list_internal+0x1cd/0x300
2023-08-26T14:04:35.619844+02:00 v-debian12 kernel: [ 3335.550483]  ? e1000_clean_rx_irq+0x369/0x500 [e1000]
2023-08-26T14:04:35.619845+02:00 v-debian12 kernel: [ 3335.550492]  napi_complete_done+0x6d/0x1a0
2023-08-26T14:04:35.619845+02:00 v-debian12 kernel: [ 3335.550495]  e1000_clean+0x296/0x6a0 [e1000]
2023-08-26T14:04:35.619846+02:00 v-debian12 kernel: [ 3335.550505]  ? vbg_heartbeat_host_config+0x90/0x90 [vboxguest]
2023-08-26T14:04:35.619847+02:00 v-debian12 kernel: [ 3335.550512]  __napi_poll+0x2b/0x160
2023-08-26T14:04:35.619848+02:00 v-debian12 kernel: [ 3335.550515]  net_rx_action+0x2a5/0x360
2023-08-26T14:04:35.619848+02:00 v-debian12 kernel: [ 3335.550518]  ? __napi_schedule+0x8e/0xb0
2023-08-26T14:04:35.619849+02:00 v-debian12 kernel: [ 3335.550521]  __do_softirq+0xf0/0x2fe
2023-08-26T14:04:35.619850+02:00 v-debian12 kernel: [ 3335.550525]  __irq_exit_rcu+0xc7/0x130
2023-08-26T14:04:35.619850+02:00 v-debian12 kernel: [ 3335.550528]  common_interrupt+0xb9/0xd0
2023-08-26T14:04:35.619851+02:00 v-debian12 kernel: [ 3335.550531]  </IRQ>
2023-08-26T14:04:35.619852+02:00 v-debian12 kernel: [ 3335.550532]  <TASK>
2023-08-26T14:04:35.619852+02:00 v-debian12 kernel: [ 3335.550533]  asm_common_interrupt+0x22/0x40
2023-08-26T14:04:35.619853+02:00 v-debian12 kernel: [ 3335.550535] RIP: 0010:mwait_idle+0x54/0x80
2023-08-26T14:04:35.619854+02:00 v-debian12 kernel: [ 3335.550539] Code: 31 d2 48 89 d1 65 48 8b 04 25 c0 fb 01 00 0f 01 c8 48 8b 00 a8 08 75 14 66 90 0f 00 2d 05 f5 5c 00 31 c0 48 89 c1 fb 0f 01 c9 <eb> 06 fb 0f 1f 44 00 00 65 48 8b 04 25 c0 fb 01 00 3e 80 60 02 df
2023-08-26T14:04:35.619855+02:00 v-debian12 kernel: [ 3335.550540] RSP: 0018:ffffffff94003e98 EFLAGS: 00000246
2023-08-26T14:04:35.619855+02:00 v-debian12 kernel: [ 3335.550542] RAX: 0000000000000000 RBX: ffffffff9401aa40 RCX: 0000000000000000
2023-08-26T14:04:35.619856+02:00 v-debian12 kernel: [ 3335.550544] RDX: 0000000000000000 RSI: ffffffff9399cba6 RDI: ffffffff939761d1
2023-08-26T14:04:35.619857+02:00 v-debian12 kernel: [ 3335.550545] RBP: 0000000000000000 R08: 000003a6bb03287e R09: 0000000000000000
2023-08-26T14:04:35.619857+02:00 v-debian12 kernel: [ 3335.550546] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
2023-08-26T14:04:35.619858+02:00 v-debian12 kernel: [ 3335.550547] R13: 0000000000000000 R14: ffffffff9401a118 R15: 0000000000000000
2023-08-26T14:04:35.619859+02:00 v-debian12 kernel: [ 3335.550550]  ? default_idle+0x10/0x10
2023-08-26T14:04:35.619859+02:00 v-debian12 kernel: [ 3335.550553]  default_idle_call+0x36/0xf0
2023-08-26T14:04:35.619860+02:00 v-debian12 kernel: [ 3335.550556]  do_idle+0x225/0x2b0
2023-08-26T14:04:35.619861+02:00 v-debian12 kernel: [ 3335.550560]  cpu_startup_entry+0x19/0x20
2023-08-26T14:04:35.619862+02:00 v-debian12 kernel: [ 3335.550562]  rest_init+0xcb/0xd0
2023-08-26T14:04:35.619862+02:00 v-debian12 kernel: [ 3335.550565]  arch_call_rest_init+0xa/0x14
2023-08-26T14:04:35.619863+02:00 v-debian12 kernel: [ 3335.550572]  start_kernel+0x6fe/0x727
2023-08-26T14:04:35.619873+02:00 v-debian12 kernel: [ 3335.550575]  secondary_startup_64_no_verify+0xe5/0xeb
2023-08-26T14:04:35.619875+02:00 v-debian12 kernel: [ 3335.550580]  </TASK>
2023-08-26T14:04:35.619875+02:00 v-debian12 kernel: [ 3335.550581] ---[ end trace 0000000000000000 ]---

# the RST packet that caused the warning
2023-08-26T14:04:35.619876+02:00 v-debian12 kernel: [ 3335.550593] IN= OUT=enp0s8 SRC=192.168.56.3 DST=192.168.56.4 LEN=40 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=TCP SPT=12345 DPT=48576 WINDOW=0 RES=0x00 ACK RST URGP=0
```


## Known workarounds

The issue is benign and does not prevent the traffic from being sent correctly so there is no strict necessity for a workaround.
On my affected setup i could prevent the warning from showing up by marking traffic for the alternate uplink using nftables and rewriting the routing policy to only use L3 and fwmark selectors.
Comment 1 Bagas Sanjaya 2023-08-28 00:24:19 UTC 
(In reply to stephane.poignant from comment #0)
> ## Overall description
> 
> After migration from kernel 5.10 to 6.1, i started to encounter the
> following warning although they do not seem to have any significant
> functional impact.
> Following further investigation, it appears that the warning appears when
> both of the following conditions are:
>  - At least one policy based routing rules with L4 selectors (among others,
> L3 matchers and fwmark DO NOT trigger the issue)
>  - A nftable or iptable filtering policy with at least one action rejecting
> traffic with TCP reset (drop action, or reject with ICMP unreachable DO NOT
> trigger)
> 
> The first time a packet matches the reject policy, and that a RST segment is
> forged and sent, a kernel WARNING as follows will show up in the dmesg:
> ```
> WARNING: CPU: 0 PID: 0 at net/core/flow_dissector.c:1016
> __skb_flow_dissect+0xa91/0x1cd0
> ```
> 
> Traffic does not appear to be affected, including the RST segment that is
> reliably delivered in spite of the WARNING.
> 
> 
> ## Expected behaviour
> 
> The warning should not appear, in this particular setup the namespace of the
> RST packet should be resolved to the default one.
> 
> 
> ## Reproducing steps
> 
> The following minimalistic configuration will reproduce the issue:
> 
> - Running last 6.1 "vanilla" kernel at the time of writing:
> ```
> root@v-debian12:~# uname -a
> Linux v-debian12 6.1.47 #1 SMP PREEMPT_DYNAMIC Fri Aug 25 13:23:01 CEST 2023
> x86_64 GNU/Linux
> ```
> NB: Issue won't happen on different 5.10 kernels that i tried
> 
> - A routing policy with a rule that uses L4 selectors:
> ```
> root@v-debian12:~# cat /etc/iproute2/rt_tables.d/wanalt.conf
> 100 wanalt
> 
> root@v-debian12:~# ip rule ls
> 0:    from all lookup local
> 100:  from all ipproto udp dport 27000-27999 lookup wanalt
> 32766:        from all lookup main
> 32767:        from all lookup default
> 
> root@v-debian12:~# ip route ls
> default via 192.168.56.1 dev enp0s8
> 192.168.56.0/24 dev enp0s8 proto kernel scope link src 192.168.56.3
> 
> root@v-debian12:~# ip route ls table wanalt
> default via 192.168.56.2 dev enp0s8
> ```
> 
> - A nftables or iptables rules that rejects some traffic with tcp reset:
> ```
> root@v-debian12:~# nft list ruleset
> table inet filter {
>       chain input {
>               type filter hook input priority filter; policy accept;
>               tcp dport 12345 log reject with tcp reset
>       }
> 
>       chain output {
>               type filter hook output priority filter; policy accept;
>               tcp sport 12345 tcp flags rst / fin,syn,rst log
>       }
> }
> ```
> (NB: the rule in thhhe output chain is only for debugging purpose, it let us
> see what packet caused the warning in the dmesg)
> 
> - from another VM, we attempt to connect to port 12345 on the reproducing
> host:
> ```
> root@v-debian11:~# nc 192.168.56.3 12345
> ```
> 
> - the following appears in the dmesg of the reproducing host:
> ```
> # the packet that matched the reject rule
> 2023-08-26T14:04:35.619764+02:00 v-debian12 kernel: [ 3335.550250] IN=enp0s8
> OUT= MAC=08:00:27:76:64:62:08:00:27:69:c9:e5:08:00 SRC=192.168.56.4
> DST=192.168.56.3 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=30150 DF PROTO=TCP
> SPT=48576 DPT=12345 WINDOW=64240 RES=0x00 SYN URGP=0
> 
> # the warning showing up
> 2023-08-26T14:04:35.619791+02:00 v-debian12 kernel: [ 3335.550267]
> ------------[ cut here ]------------
> 2023-08-26T14:04:35.619793+02:00 v-debian12 kernel: [ 3335.550269] WARNING:
> CPU: 0 PID: 0 at net/core/flow_dissector.c:1016
> __skb_flow_dissect+0xa91/0x1cd0
> 2023-08-26T14:04:35.619795+02:00 v-debian12 kernel: [ 3335.550277] Modules
> linked in: nf_log_syslog(E) nft_reject_inet(E) nf_reject_ipv4(E)
> nf_reject_ipv6(E) nft_reject(E) nft_log(E) nf_tables(E) libcrc32c(E)
> nfnetlink(E) intel_rapl_msr(E) intel_rapl_common(E) intel_pmc_core(E)
> intel_powerclamp(E) ghash_clmulni_intel(E) sha512_ssse3(E) sha512_generic(E)
> vmwgfx(E) aesni_intel(E) drm_ttm_helper(E) snd_pcm(E) crypto_simd(E)
> iTCO_wdt(E) cryptd(E) intel_pmc_bxt(E) ttm(E) iTCO_vendor_support(E) rapl(E)
> watchdog(E) snd_timer(E) drm_kms_helper(E) snd(E) joydev(E) soundcore(E)
> vboxguest(E) pcspkr(E) rng_core(E) ac(E) button(E) evdev(E) serio_raw(E)
> sg(E) binfmt_misc(E) drm(E) fuse(E) dm_mod(E) loop(E) efi_pstore(E)
> configfs(E) ip_tables(E) x_tables(E) autofs4(E) ext4(E) crc32c_generic(E)
> crc16(E) mbcache(E) jbd2(E) sd_mod(E) t10_pi(E) crc64_rocksoft(E) crc64(E)
> crc_t10dif(E) sr_mod(E) cdrom(E) crct10dif_generic(E) ata_generic(E) ahci(E)
> libahci(E) ata_piix(E) crct10dif_pclmul(E) crct10dif_common(E)
> crc32_pclmul(E) crc32c_intel(E) psmouse(E)
> 2023-08-26T14:04:35.619796+02:00 v-debian12 kernel: [ 3335.550336] 
> libata(E) scsi_mod(E) scsi_common(E) lpc_ich(E) i2c_piix4(E) e1000(E)
> battery(E) video(E) wmi(E)
> 2023-08-26T14:04:35.619797+02:00 v-debian12 kernel: [ 3335.550345] CPU: 0
> PID: 0 Comm: swapper/0 Tainted: G            E      6.1.47 #1
> 2023-08-26T14:04:35.619797+02:00 v-debian12 kernel: [ 3335.550348] Hardware
> name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> 2023-08-26T14:04:35.619798+02:00 v-debian12 kernel: [ 3335.550350] RIP:
> 0010:__skb_flow_dissect+0xa91/0x1cd0
> 2023-08-26T14:04:35.619799+02:00 v-debian12 kernel: [ 3335.550354] Code: 00
> bf 02 00 00 00 49 89 0c 12 66 89 78 02 41 8b 55 00 e9 e7 f6 ff ff 49 8b 44
> 24 18 48 85 c0 74 09 4c 8b 78 30 e9 30 f7 ff ff <0f> 0b e9 f6 f7 ff ff f6 c2
> 20 0f 84 e4 f6 ff ff 41 0f b7 45 0e 4c
> 2023-08-26T14:04:35.619809+02:00 v-debian12 kernel: [ 3335.550356] RSP:
> 0018:ffffc130800036b0 EFLAGS: 00010246
> 2023-08-26T14:04:35.619810+02:00 v-debian12 kernel: [ 3335.550358] RAX:
> 0000000000000000 RBX: 0000000000000008 RCX: ffffc13080003810
> 2023-08-26T14:04:35.619811+02:00 v-debian12 kernel: [ 3335.550360] RDX:
> ffffffff94240e40 RSI: ffff9b53c770ee00 RDI: 0000000000000000
> 2023-08-26T14:04:35.619812+02:00 v-debian12 kernel: [ 3335.550361] RBP:
> ffffc13080003798 R08: 0000000000000000 R09: 0000000000000000
> 2023-08-26T14:04:35.619813+02:00 v-debian12 kernel: [ 3335.550363] R10:
> ffffc13080003810 R11: ffff9b53e812ba80 R12: ffff9b53c770ee00
> 2023-08-26T14:04:35.619814+02:00 v-debian12 kernel: [ 3335.550364] R13:
> ffffffff94240e40 R14: ffff9b53c6456080 R15: 0000000000000000
> 2023-08-26T14:04:35.619814+02:00 v-debian12 kernel: [ 3335.550366] FS: 
> 0000000000000000(0000) GS:ffff9b53fdc00000(0000) knlGS:0000000000000000
> 2023-08-26T14:04:35.619815+02:00 v-debian12 kernel: [ 3335.550368] CS:  0010
> DS: 0000 ES: 0000 CR0: 0000000080050033
> 2023-08-26T14:04:35.619816+02:00 v-debian12 kernel: [ 3335.550369] CR2:
> 00007ffdda939440 CR3: 000000004d326005 CR4: 00000000000706f0
> 2023-08-26T14:04:35.619817+02:00 v-debian12 kernel: [ 3335.550371] Call
> Trace:
> 2023-08-26T14:04:35.619817+02:00 v-debian12 kernel: [ 3335.550374]  <IRQ>
> 2023-08-26T14:04:35.619818+02:00 v-debian12 kernel: [ 3335.550378]  ?
> __warn+0x7d/0xc0
> 2023-08-26T14:04:35.619819+02:00 v-debian12 kernel: [ 3335.550382]  ?
> __skb_flow_dissect+0xa91/0x1cd0
> 2023-08-26T14:04:35.619820+02:00 v-debian12 kernel: [ 3335.550385]  ?
> report_bug+0xe6/0x170
> 2023-08-26T14:04:35.619821+02:00 v-debian12 kernel: [ 3335.550388]  ?
> handle_bug+0x41/0x70
> 2023-08-26T14:04:35.619821+02:00 v-debian12 kernel: [ 3335.550391]  ?
> exc_invalid_op+0x13/0x60
> 2023-08-26T14:04:35.619822+02:00 v-debian12 kernel: [ 3335.550393]  ?
> asm_exc_invalid_op+0x16/0x20
> 2023-08-26T14:04:35.619832+02:00 v-debian12 kernel: [ 3335.550397]  ?
> __skb_flow_dissect+0xa91/0x1cd0
> 2023-08-26T14:04:35.619833+02:00 v-debian12 kernel: [ 3335.550401]  ?
> __inet_dev_addr_type+0xe8/0x180
> 2023-08-26T14:04:35.619834+02:00 v-debian12 kernel: [ 3335.550405] 
> ip_route_me_harder+0x143/0x330
> 2023-08-26T14:04:35.619835+02:00 v-debian12 kernel: [ 3335.550411] 
> nf_send_reset+0x17c/0x2d0 [nf_reject_ipv4]
> 2023-08-26T14:04:35.619835+02:00 v-debian12 kernel: [ 3335.550417] 
> nft_reject_inet_eval+0xa9/0xf2 [nft_reject_inet]
> 2023-08-26T14:04:35.619836+02:00 v-debian12 kernel: [ 3335.550422] 
> nft_do_chain+0x198/0x5d0 [nf_tables]
> 2023-08-26T14:04:35.619837+02:00 v-debian12 kernel: [ 3335.550439] 
> nft_do_chain_inet+0xa4/0x110 [nf_tables]
> 2023-08-26T14:04:35.619838+02:00 v-debian12 kernel: [ 3335.550454] 
> nf_hook_slow+0x41/0xc0
> 2023-08-26T14:04:35.619838+02:00 v-debian12 kernel: [ 3335.550458] 
> ip_local_deliver+0xce/0x110
> 2023-08-26T14:04:35.619839+02:00 v-debian12 kernel: [ 3335.550461]  ?
> ip_protocol_deliver_rcu+0x230/0x230
> 2023-08-26T14:04:35.619840+02:00 v-debian12 kernel: [ 3335.550464] 
> ip_sublist_rcv_finish+0x7e/0x90
> 2023-08-26T14:04:35.619840+02:00 v-debian12 kernel: [ 3335.550466] 
> ip_sublist_rcv+0x183/0x230
> 2023-08-26T14:04:35.619841+02:00 v-debian12 kernel: [ 3335.550468]  ?
> __netif_receive_skb_core.constprop.0+0xaf/0xf00
> 2023-08-26T14:04:35.619842+02:00 v-debian12 kernel: [ 3335.550472] 
> ip_list_rcv+0x139/0x170
> 2023-08-26T14:04:35.619843+02:00 v-debian12 kernel: [ 3335.550475] 
> __netif_receive_skb_list_core+0x29e/0x2c0
> 2023-08-26T14:04:35.619843+02:00 v-debian12 kernel: [ 3335.550479] 
> netif_receive_skb_list_internal+0x1cd/0x300
> 2023-08-26T14:04:35.619844+02:00 v-debian12 kernel: [ 3335.550483]  ?
> e1000_clean_rx_irq+0x369/0x500 [e1000]
> 2023-08-26T14:04:35.619845+02:00 v-debian12 kernel: [ 3335.550492] 
> napi_complete_done+0x6d/0x1a0
> 2023-08-26T14:04:35.619845+02:00 v-debian12 kernel: [ 3335.550495] 
> e1000_clean+0x296/0x6a0 [e1000]
> 2023-08-26T14:04:35.619846+02:00 v-debian12 kernel: [ 3335.550505]  ?
> vbg_heartbeat_host_config+0x90/0x90 [vboxguest]
> 2023-08-26T14:04:35.619847+02:00 v-debian12 kernel: [ 3335.550512] 
> __napi_poll+0x2b/0x160
> 2023-08-26T14:04:35.619848+02:00 v-debian12 kernel: [ 3335.550515] 
> net_rx_action+0x2a5/0x360
> 2023-08-26T14:04:35.619848+02:00 v-debian12 kernel: [ 3335.550518]  ?
> __napi_schedule+0x8e/0xb0
> 2023-08-26T14:04:35.619849+02:00 v-debian12 kernel: [ 3335.550521] 
> __do_softirq+0xf0/0x2fe
> 2023-08-26T14:04:35.619850+02:00 v-debian12 kernel: [ 3335.550525] 
> __irq_exit_rcu+0xc7/0x130
> 2023-08-26T14:04:35.619850+02:00 v-debian12 kernel: [ 3335.550528] 
> common_interrupt+0xb9/0xd0
> 2023-08-26T14:04:35.619851+02:00 v-debian12 kernel: [ 3335.550531]  </IRQ>
> 2023-08-26T14:04:35.619852+02:00 v-debian12 kernel: [ 3335.550532]  <TASK>
> 2023-08-26T14:04:35.619852+02:00 v-debian12 kernel: [ 3335.550533] 
> asm_common_interrupt+0x22/0x40
> 2023-08-26T14:04:35.619853+02:00 v-debian12 kernel: [ 3335.550535] RIP:
> 0010:mwait_idle+0x54/0x80
> 2023-08-26T14:04:35.619854+02:00 v-debian12 kernel: [ 3335.550539] Code: 31
> d2 48 89 d1 65 48 8b 04 25 c0 fb 01 00 0f 01 c8 48 8b 00 a8 08 75 14 66 90
> 0f 00 2d 05 f5 5c 00 31 c0 48 89 c1 fb 0f 01 c9 <eb> 06 fb 0f 1f 44 00 00 65
> 48 8b 04 25 c0 fb 01 00 3e 80 60 02 df
> 2023-08-26T14:04:35.619855+02:00 v-debian12 kernel: [ 3335.550540] RSP:
> 0018:ffffffff94003e98 EFLAGS: 00000246
> 2023-08-26T14:04:35.619855+02:00 v-debian12 kernel: [ 3335.550542] RAX:
> 0000000000000000 RBX: ffffffff9401aa40 RCX: 0000000000000000
> 2023-08-26T14:04:35.619856+02:00 v-debian12 kernel: [ 3335.550544] RDX:
> 0000000000000000 RSI: ffffffff9399cba6 RDI: ffffffff939761d1
> 2023-08-26T14:04:35.619857+02:00 v-debian12 kernel: [ 3335.550545] RBP:
> 0000000000000000 R08: 000003a6bb03287e R09: 0000000000000000
> 2023-08-26T14:04:35.619857+02:00 v-debian12 kernel: [ 3335.550546] R10:
> 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> 2023-08-26T14:04:35.619858+02:00 v-debian12 kernel: [ 3335.550547] R13:
> 0000000000000000 R14: ffffffff9401a118 R15: 0000000000000000
> 2023-08-26T14:04:35.619859+02:00 v-debian12 kernel: [ 3335.550550]  ?
> default_idle+0x10/0x10
> 2023-08-26T14:04:35.619859+02:00 v-debian12 kernel: [ 3335.550553] 
> default_idle_call+0x36/0xf0
> 2023-08-26T14:04:35.619860+02:00 v-debian12 kernel: [ 3335.550556] 
> do_idle+0x225/0x2b0
> 2023-08-26T14:04:35.619861+02:00 v-debian12 kernel: [ 3335.550560] 
> cpu_startup_entry+0x19/0x20
> 2023-08-26T14:04:35.619862+02:00 v-debian12 kernel: [ 3335.550562] 
> rest_init+0xcb/0xd0
> 2023-08-26T14:04:35.619862+02:00 v-debian12 kernel: [ 3335.550565] 
> arch_call_rest_init+0xa/0x14
> 2023-08-26T14:04:35.619863+02:00 v-debian12 kernel: [ 3335.550572] 
> start_kernel+0x6fe/0x727
> 2023-08-26T14:04:35.619873+02:00 v-debian12 kernel: [ 3335.550575] 
> secondary_startup_64_no_verify+0xe5/0xeb
> 2023-08-26T14:04:35.619875+02:00 v-debian12 kernel: [ 3335.550580]  </TASK>
> 2023-08-26T14:04:35.619875+02:00 v-debian12 kernel: [ 3335.550581] ---[ end
> trace 0000000000000000 ]---
> 
> # the RST packet that caused the warning
> 2023-08-26T14:04:35.619876+02:00 v-debian12 kernel: [ 3335.550593] IN=
> OUT=enp0s8 SRC=192.168.56.3 DST=192.168.56.4 LEN=40 TOS=0x00 PREC=0x00
> TTL=64 ID=0 DF PROTO=TCP SPT=12345 DPT=48576 WINDOW=0 RES=0x00 ACK RST URGP=0
> ```
> 
> 
> ## Known workarounds
> 
> The issue is benign and does not prevent the traffic from being sent
> correctly so there is no strict necessity for a workaround.
> On my affected setup i could prevent the warning from showing up by marking
> traffic for the alternate uplink using nftables and rewriting the routing
> policy to only use L3 and fwmark selectors.

Can you bisect between v5.10 and v6.1?
Comment 2 Artem S. Tashkinov 2023-08-28 07:50:44 UTC 
> Can you bisect between v5.10 and v6.1?

You're not joking, right?
Comment 3 Bagas Sanjaya 2023-08-28 14:07:25 UTC 
On 28/08/2023 14:50, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=217826
> 
> --- Comment #2 from Artem S. Tashkinov (aros@gmx.com) ---
>> Can you bisect between v5.10 and v6.1?
> 
> You're not joking, right?
> 

Oops, I thought it was regression.
Comment 4 stephane.poignant 2023-08-28 19:54:29 UTC 
Hi, thanks for the replies. I did a few tests with other kernel versions (using the Debian packages).
Both the older 6.1.12 and 6.4.11 are reproducing.
Here is the output obtained with 6.4.11:
```
2023-08-28T21:25:09.311710+02:00 v-debian kernel: [   40.586788] IN=ens33 OUT= MAC=00:0c:29:ef:12:dc:00:0c:29:6a:e2:37:08:00 SRC=192.168.8.81 DST=192.168.8.88 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=61393 DF PROTO=TCP SPT=55436 DPT=12345 WINDOW=64106 RES=0x00 SYN URGP=0
2023-08-28T21:25:09.311865+02:00 v-debian kernel: [   40.586975] ------------[ cut here ]------------
2023-08-28T21:25:09.311867+02:00 v-debian kernel: [   40.587004] WARNING: CPU: 1 PID: 0 at net/core/flow_dissector.c:1018 __skb_flow_dissect+0x7ad/0x1b60
2023-08-28T21:25:09.312315+02:00 v-debian kernel: [   40.587016] Modules linked in: nf_log_syslog nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_log nf_tables libcrc32c nfnetlink binfmt_misc intel_rapl_msr vsock_loopback intel_rapl_common vmw_vsock_virtio_transport_common ghash_clmulni_intel sha512_ssse3 sha512_generic vmw_vsock_vmci_transport vsock aesni_intel crypto_simd cryptd rapl vmwgfx vmw_balloon drm_ttm_helper ttm pcspkr drm_kms_helper vmw_vmci button ac joydev sg evdev serio_raw drm loop fuse dm_mod efi_pstore configfs ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 crc32c_generic sd_mod t10_pi crc64_rocksoft crc64 crc_t10dif crct10dif_generic hid_generic usbhid hid sr_mod cdrom ata_generic ata_piix crct10dif_pclmul crct10dif_common mptspi mptscsih crc32_pclmul mptbase libata ehci_pci uhci_hcd crc32c_intel ehci_hcd scsi_transport_spi psmouse i2c_piix4 usbcore scsi_mod e1000 usb_common scsi_common
2023-08-28T21:25:09.312318+02:00 v-debian kernel: [   40.587462] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.4.0-3-amd64 #1  Debian 6.4.11-1
2023-08-28T21:25:09.312323+02:00 v-debian kernel: [   40.587470] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
2023-08-28T21:25:09.312326+02:00 v-debian kernel: [   40.587477] RIP: 0010:__skb_flow_dissect+0x7ad/0x1b60
2023-08-28T21:25:09.312724+02:00 v-debian kernel: [   40.587485] Code: 00 00 8b 45 18 2b 45 10 83 f8 07 0f 8e 5a 0b 00 00 48 63 45 10 4c 01 f8 74 09 80 38 11 0f 84 1c 04 00 00 31 c9 e9 11 ff ff ff <0f> 0b e9 ad fa ff ff 66 41 81 fd 89 2f 0f 84 84 01 00 00 66 41 81
2023-08-28T21:25:09.312727+02:00 v-debian kernel: [   40.587494] RSP: 0018:ffffaa10804e87f0 EFLAGS: 00010246
2023-08-28T21:25:09.312728+02:00 v-debian kernel: [   40.587505] RAX: 0000000000000000 RBX: ffff9ddb796c3800 RCX: ffffaa10804e8950
2023-08-28T21:25:09.312728+02:00 v-debian kernel: [   40.587512] RDX: 0000000000000028 RSI: ffff9ddb796c3800 RDI: 0000000000000000
2023-08-28T21:25:09.312729+02:00 v-debian kernel: [   40.587518] RBP: ffffaa10804e88d8 R08: 0000000000000000 R09: 0000000000000000
2023-08-28T21:25:09.312729+02:00 v-debian kernel: [   40.587525] R10: 0000000000000000 R11: ffff9ddb79473a80 R12: ffffffffa6843c20
2023-08-28T21:25:09.312730+02:00 v-debian kernel: [   40.587531] R13: 0000000000000008 R14: ffffaa10804e8950 R15: ffff9ddb45349200
2023-08-28T21:25:09.312730+02:00 v-debian kernel: [   40.587538] FS:  0000000000000000(0000) GS:ffff9ddc75e40000(0000) knlGS:0000000000000000
2023-08-28T21:25:09.312731+02:00 v-debian kernel: [   40.587545] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
2023-08-28T21:25:09.312731+02:00 v-debian kernel: [   40.587552] CR2: 00007f12a2b8bbbc CR3: 0000000138f3a001 CR4: 00000000001706e0
2023-08-28T21:25:09.312732+02:00 v-debian kernel: [   40.587560] Call Trace:
2023-08-28T21:25:09.312732+02:00 v-debian kernel: [   40.587566]  <IRQ>
2023-08-28T21:25:09.312732+02:00 v-debian kernel: [   40.587572]  ? __skb_flow_dissect+0x7ad/0x1b60
2023-08-28T21:25:09.312733+02:00 v-debian kernel: [   40.587579]  ? __warn+0x81/0x130
2023-08-28T21:25:09.312733+02:00 v-debian kernel: [   40.587591]  ? __skb_flow_dissect+0x7ad/0x1b60
2023-08-28T21:25:09.312734+02:00 v-debian kernel: [   40.587600]  ? report_bug+0x191/0x1c0
2023-08-28T21:25:09.312734+02:00 v-debian kernel: [   40.587612]  ? handle_bug+0x3c/0x80
2023-08-28T21:25:09.312734+02:00 v-debian kernel: [   40.587621]  ? exc_invalid_op+0x17/0x70
2023-08-28T21:25:09.312735+02:00 v-debian kernel: [   40.587631]  ? asm_exc_invalid_op+0x1a/0x20
2023-08-28T21:25:09.312735+02:00 v-debian kernel: [   40.587643]  ? __skb_flow_dissect+0x7ad/0x1b60
2023-08-28T21:25:09.312736+02:00 v-debian kernel: [   40.587655]  ? __inet_dev_addr_type+0xe8/0x180
2023-08-28T21:25:09.312736+02:00 v-debian kernel: [   40.587669]  ip_route_me_harder+0x147/0x340
2023-08-28T21:25:09.312736+02:00 v-debian kernel: [   40.587686]  nf_send_reset+0x183/0x2e0 [nf_reject_ipv4]
2023-08-28T21:25:09.312737+02:00 v-debian kernel: [   40.587703]  nft_reject_inet_eval+0xd5/0x100 [nft_reject_inet]
2023-08-28T21:25:09.312742+02:00 v-debian kernel: [   40.587716]  nft_do_chain+0x101/0x600 [nf_tables]
2023-08-28T21:25:09.313930+02:00 v-debian kernel: [   40.587895]  nft_do_chain_inet+0x54/0x130 [nf_tables]
2023-08-28T21:25:09.313933+02:00 v-debian kernel: [   40.588100]  nf_hook_slow+0x42/0xc0
2023-08-28T21:25:09.313934+02:00 v-debian kernel: [   40.588113]  ip_local_deliver+0xd0/0x120
2023-08-28T21:25:09.313934+02:00 v-debian kernel: [   40.588124]  ? __pfx_ip_local_deliver_finish+0x10/0x10
2023-08-28T21:25:09.313935+02:00 v-debian kernel: [   40.588136]  ip_sublist_rcv_finish+0x7e/0x90
2023-08-28T21:25:09.313935+02:00 v-debian kernel: [   40.588147]  ip_sublist_rcv+0x186/0x230
2023-08-28T21:25:09.313936+02:00 v-debian kernel: [   40.588158]  ? __netif_receive_skb_core.constprop.0+0x316/0xf40
2023-08-28T21:25:09.313936+02:00 v-debian kernel: [   40.588168]  ip_list_rcv+0x13d/0x170
2023-08-28T21:25:09.313936+02:00 v-debian kernel: [   40.588181]  __netif_receive_skb_list_core+0x29d/0x2c0
2023-08-28T21:25:09.313936+02:00 v-debian kernel: [   40.588193]  netif_receive_skb_list_internal+0x1d1/0x310
2023-08-28T21:25:09.313937+02:00 v-debian kernel: [   40.588202]  ? e1000_clean_rx_irq+0x356/0x4f0 [e1000]
2023-08-28T21:25:09.313937+02:00 v-debian kernel: [   40.588239]  napi_complete_done+0x72/0x1a0
2023-08-28T21:25:09.313938+02:00 v-debian kernel: [   40.588249]  e1000_clean+0x291/0x940 [e1000]
2023-08-28T21:25:09.313938+02:00 v-debian kernel: [   40.588311]  ? check_preempt_curr+0x37/0x70
2023-08-28T21:25:09.313938+02:00 v-debian kernel: [   40.588323]  ? ttwu_do_activate+0x5d/0x1f0
2023-08-28T21:25:09.313939+02:00 v-debian kernel: [   40.588335]  __napi_poll+0x28/0x1b0
2023-08-28T21:25:09.313939+02:00 v-debian kernel: [   40.588344]  net_rx_action+0x2ab/0x390
2023-08-28T21:25:09.313939+02:00 v-debian kernel: [   40.588356]  __do_softirq+0xf1/0x301
2023-08-28T21:25:09.313939+02:00 v-debian kernel: [   40.588367]  __irq_exit_rcu+0xb5/0x130
2023-08-28T21:25:09.313940+02:00 v-debian kernel: [   40.588378]  common_interrupt+0xbd/0xe0
2023-08-28T21:25:09.313940+02:00 v-debian kernel: [   40.588388]  </IRQ>
2023-08-28T21:25:09.313940+02:00 v-debian kernel: [   40.588447]  <TASK>
2023-08-28T21:25:09.313941+02:00 v-debian kernel: [   40.588454]  asm_common_interrupt+0x26/0x40
2023-08-28T21:25:09.313941+02:00 v-debian kernel: [   40.588463] RIP: 0010:pv_native_safe_halt+0xf/0x20
2023-08-28T21:25:09.313941+02:00 v-debian kernel: [   40.588472] Code: 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d e5 f9 26 00 fb f4 <c3> cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
2023-08-28T21:25:09.313942+02:00 v-debian kernel: [   40.588479] RSP: 0018:ffffaa10800bbe58 EFLAGS: 00000246
2023-08-28T21:25:09.313942+02:00 v-debian kernel: [   40.588490] RAX: 0000000000004000 RBX: 0000000000000001 RCX: 0000000000000020
2023-08-28T21:25:09.313943+02:00 v-debian kernel: [   40.588497] RDX: ffff9ddc75e40000 RSI: ffff9ddb4123f800 RDI: ffff9ddb4123f864
2023-08-28T21:25:09.313943+02:00 v-debian kernel: [   40.588529] RBP: ffff9ddb42386800 R08: ffff9ddc75e64560 R09: 0000000000000007
2023-08-28T21:25:09.313943+02:00 v-debian kernel: [   40.588535] R10: ffff9ddc75e71d84 R11: 0000000000008601 R12: ffffffffa67a2e00
2023-08-28T21:25:09.313944+02:00 v-debian kernel: [   40.588542] R13: ffff9ddb4123f864 R14: 0000000000000001 R15: 0000000000000000
2023-08-28T21:25:09.313944+02:00 v-debian kernel: [   40.588555]  acpi_safe_halt+0x15/0x30
2023-08-28T21:25:09.313944+02:00 v-debian kernel: [   40.588565]  acpi_idle_enter+0xa3/0x100
2023-08-28T21:25:09.313945+02:00 v-debian kernel: [   40.588576]  cpuidle_enter_state+0x81/0x440
2023-08-28T21:25:09.313945+02:00 v-debian kernel: [   40.588586]  cpuidle_enter+0x2d/0x40
2023-08-28T21:25:09.313945+02:00 v-debian kernel: [   40.588598]  do_idle+0x217/0x270
2023-08-28T21:25:09.313945+02:00 v-debian kernel: [   40.588609]  cpu_startup_entry+0x1d/0x20
2023-08-28T21:25:09.313946+02:00 v-debian kernel: [   40.588617]  start_secondary+0x134/0x160
2023-08-28T21:25:09.313946+02:00 v-debian kernel: [   40.588628]  secondary_startup_64_no_verify+0x10b/0x10b
2023-08-28T21:25:09.313946+02:00 v-debian kernel: [   40.588643]  </TASK>
2023-08-28T21:25:09.313947+02:00 v-debian kernel: [   40.588649] ---[ end trace 0000000000000000 ]---
2023-08-28T21:25:09.313947+02:00 v-debian kernel: [   40.588671] IN= OUT=ens33 SRC=192.168.8.88 DST=192.168.8.81 LEN=40 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=TCP SPT=12345 DPT=55436 WINDOW=0 RES=0x00 ACK RST URGP=0
```

Also the issue only happens with packets generated by nftables or iptables reject. Sending the same RST segment using hping3, or simply trying to connect to a closed port, does not trigger the issue.

Some additional observations in case this may help.

It does not look like it is an ebpf issue, especially the relevant parts of __skb_flow_dissect haven't changed between reproducing and not reproducing versions. It appears that __skb_flow_dissect is called with net being NULL and the namespace cannot be deduced from the skb->dev or skb->sk.

The issue does not happens when rejecting with ICMP unreachable (default) because contrary to nf_send_reset, nf_send_unreach does not call ip_route_me_harder.

One change between both version is that 5.10 would pass nskb->sk to ip_route_me_harder (the sk_buff allocated inside nf_send_reset to hold the RST packet information), whereas in 6.1 and 6.4 we pass the original sk (in my understanding, from the packet that was rejected).

5.10.x, not reproducing:
```
void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook)
{
        struct net_device *br_indev __maybe_unused;
        struct sk_buff *nskb;
...
        nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
                         LL_MAX_HEADER, GFP_ATOMIC);
...
        if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
                goto free_nskb;
```

6.1.x, reproducing:
```
void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
                   int hook)
{
        struct net_device *br_indev __maybe_unused;
        struct sk_buff *nskb;
...
        nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
                         LL_MAX_HEADER, GFP_ATOMIC);
...
        if (ip_route_me_harder(net, sk, nskb, RTN_UNSPEC))
                goto free_nskb;
```

Is there a reason for this? It seems to me we are passing the wrong packet information, but i don't have the background on this to be sure.

Best regards,
Comment 5 Florian Westphal 2023-08-29 18:39:10 UTC 
Created attachment 304984 [details]
pass netns pointer to flow dissector to avoid warn splat

Could you please test the attached patch? Thanks.
Comment 6 stephane.poignant 2023-08-30 03:54:10 UTC 
Sure. I just tested and i'm not able to reproduce anymore on 6.1.47 with the patch applied. TCP reset is still sent reliably and i haven't seen any other issue.
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