Re: network namespace and kernel bind issue

Stephen Hemminger [off-list ref] writes:

On Mon, 1 Oct 2012 14:16:09 -0700
Stephen Hemminger [off-list ref] wrote:

quoted

When testing VXLAN I noticed that the kernel bind seems to be a problem for
network tunnels. The init_net function is called repeatedly for the same
network namespace!

It definitely should not be.

quoted

1. Create vxlan device:
 # ip li add vxlan0 type vxlan id 11 group 239.1.1.1 dev eth0
 # dmesg | tail
[11580.671016] vxlan: vxlan_init_net in net 1

Net 1?  What are you printing out?  It isn't the net_id by any chance?

quoted

2. Start Chrome (or other application using namespaces)
 
  dmesg | tail
[11587.371195] vxlan: vxlan_init_net in net 1
[11587.371211] vxlan: bind for UDP socket 0.0.0.0:8472 (-98)


Isn't init_net supposed to be unique. The current semantics also break
L2TP.

The init method should be called exactly once per network namespace.

The timing of the init methods you report seems correct.

The vxlan code isn't in net-next or I would take a look.

I took a quick look at l2tp and the code is doing some weird things.
There are a bunch of references to &init_net that I would expect
to references to either sk_net() or dev_net().  

Adding support for multiple network namespaces and then reaching
out to the initial network namespace for things is definitely a recipe
for getting confused.

So my blind guess would be that someone half implemented network
namespace support for l2tp and vxlan copied the bugs.

Eric

quoted

This is with 3.6.0-rc7-net-next

Here is back trace from where duplicate network namespace init gets done.

[13532.579900] vxlan: bind for UDP socket 0.0.0.0:8472 (-98)
[13532.579903] ------------[ cut here ]------------
[13532.579906] WARNING: at drivers/net/vxlan.c:1148 vxlan_init_net+0xc9/0x126 [vxlan]()
[13532.579907] Hardware name: System Product Name
[13532.579908] Modules linked in: vxlan nfnetlink_log nfnetlink ip6table_filter ip6_tables ebtable_nat ebtables ipt_MASQUERADE iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle xt_tcpudp iptable_filter ip_tables x_tables tun bridge stp llc cpufreq_stats cpufreq_powersave cpufreq_conservative cpufreq_userspace binfmt_misc fuse loop snd_hda_codec_hdmi snd_hda_codec_realtek i915 hid_belkin hid_generic snd_hda_intel evdev snd_hda_codec drm_kms_helper snd_hwdep drm snd_pcm_oss snd_pcm psmouse microcode snd_page_alloc serio_raw pcspkr i2c_i801 snd_timer i2c_algo_bit i2c_core acpi_cpufreq mperf processor video button btrfs libcrc32c lzo_compress zlib_deflate crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 ablk_hel

 per cryptd usbhid hid ixgbe r8169 mii mdio thermal [last unloaded: vxlan]

[13532.579965] Pid: 7130, comm: chromium-sandbo Not tainted 3.6.0-rc7-net-next+ #10
[13532.579966] Call Trace:
[13532.579972]  [<ffffffff8106674e>] warn_slowpath_common+0x83/0x9c
[13532.579974]  [<ffffffff81066781>] warn_slowpath_null+0x1a/0x1c
[13532.579976]  [<ffffffffa03ea87d>] vxlan_init_net+0xc9/0x126 [vxlan]
[13532.579980]  [<ffffffff8136b4dd>] ops_init+0xcd/0xfc
[13532.579982]  [<ffffffff8136b824>] setup_net+0x51/0xd8
[13532.579984]  [<ffffffff8136bd37>] copy_net_ns+0x6c/0xd7
[13532.579987]  [<ffffffff810882bb>] create_new_namespaces+0xd8/0x14f
[13532.579989]  [<ffffffff81088417>] copy_namespaces+0x69/0x9e
[13532.579991]  [<ffffffff81065b10>] copy_process.part.27+0x12ae/0x12f5
[13532.579994]  [<ffffffff8144170f>] ? do_page_fault+0x2fb/0x37c
[13532.579997]  [<ffffffff8111d4d8>] ? might_fault+0x5c/0xac
[13532.579998]  [<ffffffff81065cb2>] do_fork+0x120/0x2fc
[13532.580001]  [<ffffffff810e7343>] ? time_hardirqs_off+0x15/0x2a
[13532.580004]  [<ffffffff8143ea53>] ? error_sti+0x5/0x6
[13532.580007]  [<ffffffff810a7204>] ? trace_hardirqs_off_caller+0x3f/0x9e
[13532.580009]  [<ffffffff8143e646>] ? retint_swapgs+0xe/0x13
[13532.580012]  [<ffffffff8103e541>] sys_clone+0x28/0x2a
[13532.580014]  [<ffffffff814450e3>] stub_clone+0x13/0x20
[13532.580016]  [<ffffffff81444d92>] ? system_call_fastpath+0x16/0x1b
[13532.580018] ---[ end trace 2c2b222e23a4d880 ]---
[13573.765721] vxlan: bind for UDP socket 0.0.0.0:8472 (-98)