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Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.

Started byGuillaume Nault <g.nault@alphalink.fr>
First post2017-04-11 12:50 +0200
Last post2017-04-11 21:20 +0200
Articles 4 — 2 participants

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  Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3,  L2 hdrs. Guillaume Nault <g.nault@alphalink.fr> - 2017-04-11 12:50 +0200
    Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs. R Parameswaran <parameswaran.r7@gmail.com> - 2017-04-11 18:50 +0200
      Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3,  L2 hdrs. Guillaume Nault <g.nault@alphalink.fr> - 2017-04-11 19:10 +0200
        Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs. R Parameswaran <parameswaran.r7@gmail.com> - 2017-04-11 21:20 +0200

#1621143 — Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.

FromGuillaume Nault <g.nault@alphalink.fr>
Date2017-04-11 12:50 +0200
SubjectRe: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.
Message-ID<tv1x0-5Qj-27@gated-at.bofh.it>
On Wed, Apr 05, 2017 at 05:00:07PM -0700, R. Parameswaran wrote:
> 
> Change-set here uses the new kernel function, kernel_sock_ip_overhead(),
> to factor the outer IP overhead on the L2TP tunnel socket (including
> IP Options, if any) when calculating the default MTU for an Ethernet
> pseudowire, along with consideration of the inner Ethernet header.
> 
I get the following warning with CONFIG_LOCKDEP when creating a new
session:
# ip l2tp add tunnel local 10.1.8.64 remote 10.1.8.32 udp_sport 1701 udp_dport 1701 tunnel_id 1 peer_tunnel_id 1
# ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1
...
[   45.524535] ------------[ cut here ]------------
[   45.524570] WARNING: CPU: 3 PID: 732 at ./include/net/sock.h:1509 kernel_sock_ip_overhead+0x54/0x1a1
[   45.524574] Modules linked in: l2tp_eth l2tp_netlink l2tp_core ip6_udp_tunnel udp_tunnel crc32c_intel ghash_clmulni_intel pcbc aesni_intel aes_x86_64 crypto_simd cryptd glue_helper evdev acpi_cpufreq processor button serio_raw ext4 crc16 jbd2 mbcache virtio_blk virtio_net virtio_pci virtio_ring virtio
[   45.524696] CPU: 3 PID: 732 Comm: ip Not tainted 4.11.0-rc5 #1
[   45.524700] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   45.524704] Call Trace:
[   45.524714]  dump_stack+0x67/0x90
[   45.524725]  __warn+0xfd/0x118
[   45.524739]  warn_slowpath_null+0x18/0x1a
[   45.524747]  kernel_sock_ip_overhead+0x54/0x1a1
[   45.524761]  l2tp_eth_create+0x1eb/0x557 [l2tp_eth]
[   45.524768]  ? __mutex_unlock_slowpath+0xb5/0x2c2
[   45.524787]  ? l2tp_eth_dev_uninit+0xd9/0xd9 [l2tp_eth]
[   45.524800]  l2tp_nl_cmd_session_create+0x521/0x56b [l2tp_netlink]
[   45.524827]  genl_family_rcv_msg+0x445/0x4b3
[   45.524857]  genl_rcv_msg+0x60/0x84
[   45.524867]  ? genl_family_rcv_msg+0x4b3/0x4b3
[   45.524875]  netlink_rcv_skb+0x95/0x102
[   45.524881]  ? down_read+0x41/0x62
[   45.524893]  genl_rcv+0x23/0x32
[   45.524901]  netlink_unicast+0x1b0/0x23b
[   45.524915]  netlink_sendmsg+0x46f/0x48f
[   45.524933]  ? netlink_unicast+0x23b/0x23b
[   45.524942]  sock_sendmsg_nosec+0x41/0x51
[   45.524953]  sock_sendmsg+0x33/0x38
[   45.524962]  ___sys_sendmsg+0x2a0/0x374
[   45.524991]  ? do_raw_spin_unlock+0xc2/0xcc
[   45.525002]  ? _raw_spin_unlock+0x22/0x25
[   45.525014]  ? match_held_lock+0x20/0x113
[   45.525027]  ? __fget_light+0x89/0xae
[   45.525045]  __sys_sendmsg+0x40/0x6b
[   45.525052]  ? __sys_sendmsg+0x40/0x6b
[   45.525075]  SyS_sendmsg+0x9/0xb
[   45.525083]  entry_SYSCALL_64_fastpath+0x18/0xad
[   45.525089] RIP: 0033:0x7fb224391690
[   45.525094] RSP: 002b:00007ffe53943dd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[   45.525104] RAX: ffffffffffffffda RBX: 00007ffe539480f0 RCX: 00007fb224391690
[   45.525108] RDX: 0000000000000000 RSI: 00007ffe53943e20 RDI: 0000000000000004
[   45.525113] RBP: ffffffff810a1e49 R08: 0000000000000000 R09: 0000000000000005
[   45.525119] R10: 0000000000000000 R11: 0000000000000246 R12: ffff88003436ff98
[   45.525124] R13: 0000000000000046 R14: 00007ffe539486a0 R15: 00007ffe53947ea0
[   45.525136]  ? trace_hardirqs_off_caller+0x121/0x12f
[   45.525157] ---[ end trace 0834023e7b30e761 ]---

I guess you neet to lock_sock(tunnel->socket) before calling
kernel_sock_ip_overhead().

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#1621470 — Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.

FromR Parameswaran <parameswaran.r7@gmail.com>
Date2017-04-11 18:50 +0200
SubjectRe: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.
Message-ID<tv79n-11Q-11@gated-at.bofh.it>
In reply to#1621143
Hi Guillaume,

On Tue, Apr 11, 2017 at 3:40 AM, Guillaume Nault <g.nault@alphalink.fr> wrote:
> On Wed, Apr 05, 2017 at 05:00:07PM -0700, R. Parameswaran wrote:
>>
>> Change-set here uses the new kernel function, kernel_sock_ip_overhead(),
>> to factor the outer IP overhead on the L2TP tunnel socket (including
>> IP Options, if any) when calculating the default MTU for an Ethernet
>> pseudowire, along with consideration of the inner Ethernet header.
>>
> I get the following warning with CONFIG_LOCKDEP when creating a new
> session:
> # ip l2tp add tunnel local 10.1.8.64 remote 10.1.8.32 udp_sport 1701 udp_dport 1701 tunnel_id 1 peer_tunnel_id 1
> # ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1
> ...

Thanks for reporting this - I'll try and put up a patch soon,
hopefully the patch can stay in while I add this. One Q - how many CPU
cores do you have? Can you give me some idea of how many tunnels and
sessions when you saw this?

I did not see this warning in my testing, possibly because
CONFIG_LOCKDEP_SUPPORT is turned off on the product build? Will
re-test with this turned on.

thanks,

Ramkumar

> [   45.524535] ------------[ cut here ]------------
> [   45.524570] WARNING: CPU: 3 PID: 732 at ./include/net/sock.h:1509 kernel_sock_ip_overhead+0x54/0x1a1
> [   45.524574] Modules linked in: l2tp_eth l2tp_netlink l2tp_core ip6_udp_tunnel udp_tunnel crc32c_intel ghash_clmulni_intel pcbc aesni_intel aes_x86_64 crypto_simd cryptd glue_helper evdev acpi_cpufreq processor button serio_raw ext4 crc16 jbd2 mbcache virtio_blk virtio_net virtio_pci virtio_ring virtio
> [   45.524696] CPU: 3 PID: 732 Comm: ip Not tainted 4.11.0-rc5 #1
> [   45.524700] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> [   45.524704] Call Trace:
> [   45.524714]  dump_stack+0x67/0x90
> [   45.524725]  __warn+0xfd/0x118
> [   45.524739]  warn_slowpath_null+0x18/0x1a
> [   45.524747]  kernel_sock_ip_overhead+0x54/0x1a1
> [   45.524761]  l2tp_eth_create+0x1eb/0x557 [l2tp_eth]
> [   45.524768]  ? __mutex_unlock_slowpath+0xb5/0x2c2
> [   45.524787]  ? l2tp_eth_dev_uninit+0xd9/0xd9 [l2tp_eth]
> [   45.524800]  l2tp_nl_cmd_session_create+0x521/0x56b [l2tp_netlink]
> [   45.524827]  genl_family_rcv_msg+0x445/0x4b3
> [   45.524857]  genl_rcv_msg+0x60/0x84
> [   45.524867]  ? genl_family_rcv_msg+0x4b3/0x4b3
> [   45.524875]  netlink_rcv_skb+0x95/0x102
> [   45.524881]  ? down_read+0x41/0x62
> [   45.524893]  genl_rcv+0x23/0x32
> [   45.524901]  netlink_unicast+0x1b0/0x23b
> [   45.524915]  netlink_sendmsg+0x46f/0x48f
> [   45.524933]  ? netlink_unicast+0x23b/0x23b
> [   45.524942]  sock_sendmsg_nosec+0x41/0x51
> [   45.524953]  sock_sendmsg+0x33/0x38
> [   45.524962]  ___sys_sendmsg+0x2a0/0x374
> [   45.524991]  ? do_raw_spin_unlock+0xc2/0xcc
> [   45.525002]  ? _raw_spin_unlock+0x22/0x25
> [   45.525014]  ? match_held_lock+0x20/0x113
> [   45.525027]  ? __fget_light+0x89/0xae
> [   45.525045]  __sys_sendmsg+0x40/0x6b
> [   45.525052]  ? __sys_sendmsg+0x40/0x6b
> [   45.525075]  SyS_sendmsg+0x9/0xb
> [   45.525083]  entry_SYSCALL_64_fastpath+0x18/0xad
> [   45.525089] RIP: 0033:0x7fb224391690
> [   45.525094] RSP: 002b:00007ffe53943dd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> [   45.525104] RAX: ffffffffffffffda RBX: 00007ffe539480f0 RCX: 00007fb224391690
> [   45.525108] RDX: 0000000000000000 RSI: 00007ffe53943e20 RDI: 0000000000000004
> [   45.525113] RBP: ffffffff810a1e49 R08: 0000000000000000 R09: 0000000000000005
> [   45.525119] R10: 0000000000000000 R11: 0000000000000246 R12: ffff88003436ff98
> [   45.525124] R13: 0000000000000046 R14: 00007ffe539486a0 R15: 00007ffe53947ea0
> [   45.525136]  ? trace_hardirqs_off_caller+0x121/0x12f
> [   45.525157] ---[ end trace 0834023e7b30e761 ]---
>
> I guess you neet to lock_sock(tunnel->socket) before calling
> kernel_sock_ip_overhead().

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#1621473

FromGuillaume Nault <g.nault@alphalink.fr>
Date2017-04-11 19:10 +0200
Message-ID<tv7sJ-1pf-9@gated-at.bofh.it>
In reply to#1621470
On Tue, Apr 11, 2017 at 09:39:58AM -0700, R Parameswaran wrote:
> Hi Guillaume,
> 
> On Tue, Apr 11, 2017 at 3:40 AM, Guillaume Nault <g.nault@alphalink.fr> wrote:
> > On Wed, Apr 05, 2017 at 05:00:07PM -0700, R. Parameswaran wrote:
> >>
> >> Change-set here uses the new kernel function, kernel_sock_ip_overhead(),
> >> to factor the outer IP overhead on the L2TP tunnel socket (including
> >> IP Options, if any) when calculating the default MTU for an Ethernet
> >> pseudowire, along with consideration of the inner Ethernet header.
> >>
> > I get the following warning with CONFIG_LOCKDEP when creating a new
> > session:
> > # ip l2tp add tunnel local 10.1.8.64 remote 10.1.8.32 udp_sport 1701 udp_dport 1701 tunnel_id 1 peer_tunnel_id 1
> > # ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1
> > ...
> 
> Thanks for reporting this - I'll try and put up a patch soon,
> hopefully the patch can stay in while I add this. One Q - how many CPU
> cores do you have?
This is a virtual machine with 4 vcores, but that shouldn't matter.

> Can you give me some idea of how many tunnels and
> sessions when you saw this?
> 
Creating one session is enough. I simply used the following command:
# ip l2tp add tunnel local 10.1.8.64 remote 10.1.8.32 udp_sport 1701 udp_dport 1701 tunnel_id 1 peer_tunnel_id 1
# ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1

> I did not see this warning in my testing, possibly because
> CONFIG_LOCKDEP_SUPPORT is turned off on the product build? Will
> re-test with this turned on.
> 
Yes, enabling lockdep should let you reproduce the problem.

The issue goes away if the tunnel's socket is locked while calling
kernel_sock_ip_overhead():
+	lock_sock(tunnel->sock);
	kernel_sock_ip_overhead(tunnel->sock);
+	release_sock(tunnel->sock);

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#1621569 — Re: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.

FromR Parameswaran <parameswaran.r7@gmail.com>
Date2017-04-11 21:20 +0200
SubjectRe: [PATCH net-next v5 2/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.
Message-ID<tv9ux-2HL-5@gated-at.bofh.it>
In reply to#1621473
Hi Guillaume,

Please see inline:

On Tue, Apr 11, 2017 at 10:05 AM, Guillaume Nault <g.nault@alphalink.fr> wrote:
> On Tue, Apr 11, 2017 at 09:39:58AM -0700, R Parameswaran wrote:
>> Hi Guillaume,
>>
>> On Tue, Apr 11, 2017 at 3:40 AM, Guillaume Nault <g.nault@alphalink.fr> wrote:
>> > On Wed, Apr 05, 2017 at 05:00:07PM -0700, R. Parameswaran wrote:
>> >>
>> >> Change-set here uses the new kernel function, kernel_sock_ip_overhead(),
>> >> to factor the outer IP overhead on the L2TP tunnel socket (including
>> >> IP Options, if any) when calculating the default MTU for an Ethernet
>> >> pseudowire, along with consideration of the inner Ethernet header.
>> >>
>> > I get the following warning with CONFIG_LOCKDEP when creating a new
>> > session:
>> > # ip l2tp add tunnel local 10.1.8.64 remote 10.1.8.32 udp_sport 1701 udp_dport 1701 tunnel_id 1 peer_tunnel_id 1
>> > # ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1
>> > ...
>>
>> Thanks for reporting this - I'll try and put up a patch soon,
>> hopefully the patch can stay in while I add this. One Q - how many CPU
>> cores do you have?
> This is a virtual machine with 4 vcores, but that shouldn't matter.
>
>> Can you give me some idea of how many tunnels and
>> sessions when you saw this?
>>
> Creating one session is enough. I simply used the following command:
> # ip l2tp add tunnel local 10.1.8.64 remote 10.1.8.32 udp_sport 1701 udp_dport 1701 tunnel_id 1 peer_tunnel_id 1
> # ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1
>
>> I did not see this warning in my testing, possibly because
>> CONFIG_LOCKDEP_SUPPORT is turned off on the product build? Will
>> re-test with this turned on.
>>
> Yes, enabling lockdep should let you reproduce the problem.
>
> The issue goes away if the tunnel's socket is locked while calling
> kernel_sock_ip_overhead():
> +       lock_sock(tunnel->sock);
>         kernel_sock_ip_overhead(tunnel->sock);
> +       release_sock(tunnel->sock);

Ack, thanks - was thinking along this line, since I see similar code
at other places in L2TP. I'll try and have a preliminary
patch out by tonight.

regards,

Ramkumar

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