During source NAT development, I got some vrouter kernel trace.
To confirm, I ran a simple test :

$ cd /opt/stack/contrail/controller/src/config/utils
$ while true; do echo -n "creating... "; python contrail_veth_port.py --subnet 10.0.0.0/24 test_vm private; echo ok; echo -n "deleting... "; python contrail_veth_port.py --delete --subnet 10.0.0.0/24 test_vm private; echo ok; done

And 12 hours later I got that kernel trace:

44321 Jul 26 23:17:32 localhost kernel: [118557.448900] RTNL: assertion failed at /build/buildd/linux-3.2.0/net/core/dev.c (3218)
44322 Jul 26 23:17:32 localhost kernel: [118557.450256] Pid: 13339, comm: contrail-vroute Tainted: G           O 3.2.0-64-virtual #97-Ubuntu
44323 Jul 26 23:17:32 localhost kernel: [118557.450259] Call Trace:
44324 Jul 26 23:17:32 localhost kernel: [118557.450272]  [<ffffffff8153f8a9>] netdev_rx_handler_unregister+0x59/0x60
44325 Jul 26 23:17:32 localhost kernel: [118557.450313]  [<ffffffffa0171fd0>] linux_if_del_tap+0x90/0xa0 [vrouter]
44326 Jul 26 23:17:32 localhost kernel: [118557.450320]  [<ffffffffa017a21b>] eth_drv_del+0x1b/0x60 [vrouter]
44327 Jul 26 23:17:32 localhost kernel: [118557.450331]  [<ffffffffa017aece>] vif_delete+0x2e/0x40 [vrouter]
44328 Jul 26 23:17:32 localhost kernel: [118557.450340]  [<ffffffffa017b53c>] vr_interface_req_process+0x13c/0x250 [vrouter]
44329 Jul 26 23:17:32 localhost kernel: [118557.450345]  [<ffffffffa016c29a>] sandesh_decode_one+0x10a/0x1d0 [vrouter]
44330 Jul 26 23:17:32 localhost kernel: [118557.450352]  [<ffffffffa016dd30>] ? thrift_binary_protocol_write_field_begin+0x80/0x80 [vrouter]
44331 Jul 26 23:17:32 localhost kernel: [118557.450358]  [<ffffffffa016cf70>] ? thrift_binary_protocol_write_message_end+0x10/0x10 [vrouter]
44332 Jul 26 23:17:32 localhost kernel: [118557.450364]  [<ffffffffa016dd50>] ? thrift_binary_protocol_write_sandesh_begin+0x20/0x20 [vrouter]
44333 Jul 26 23:17:32 localhost kernel: [118557.450369]  [<ffffffffa016cf60>] ? thrift_protocol_skip+0x240/0x240 [vrouter]
44334 Jul 26 23:17:32 localhost kernel: [118557.450374]  [<ffffffffa016cf80>] ? thrift_binary_protocol_write_sandesh_end+0x10/0x10 [vrouter]
44335 Jul 26 23:17:32 localhost kernel: [118557.450379]  [<ffffffffa016cf90>] ? thrift_binary_protocol_write_struct_begin+0x10/0x10 [vrouter]
44336 Jul 26 23:17:32 localhost kernel: [118557.450384]  [<ffffffffa016dcb0>] ? thrift_binary_protocol_write_set_begin+0x10/0x10 [vrouter]
44337 Jul 26 23:17:32 localhost kernel: [118557.450389]  [<ffffffffa016cfa0>] ? thrift_binary_protocol_write_struct_end+0x10/0x10 [vrouter]
44338 Jul 26 23:17:32 localhost kernel: [118557.450395]  [<ffffffffa016dc80>] ? thrift_binary_protocol_write_map_begin+0xa0/0xa0 [vrouter]
44339 Jul 26 23:17:32 localhost kernel: [118557.450400]  [<ffffffffa016dbe0>] ? thrift_binary_protocol_write_list_begin+0x80/0x80 [vrouter]
44340 Jul 26 23:17:32 localhost kernel: [118557.450405]  [<ffffffffa016cfb0>] ? thrift_binary_protocol_write_field_end+0x10/0x10 [vrouter]
44341 Jul 26 23:17:32 localhost kernel: [118557.450410]  [<ffffffffa016db60>] ? thrift_binary_protocol_write_bool+0x20/0x20 [vrouter]
44342 Jul 26 23:17:32 localhost kernel: [118557.450415]  [<ffffffffa016cfc0>] ? thrift_binary_protocol_write_map_end+0x10/0x10 [vrouter]
44343 Jul 26 23:17:32 localhost kernel: [118557.450420]  [<ffffffffa016dca0>] ? thrift_binary_protocol_write_field_stop+0x20/0x20 [vrouter]
44344 Jul 26 23:17:32 localhost kernel: [118557.450425]  [<ffffffffa016cfd0>] ? thrift_binary_protocol_write_list_end+0x10/0x10 [vrouter]
44345 Jul 26 23:17:32 localhost kernel: [118557.450430]  [<ffffffffa016db40>] ? thrift_binary_protocol_write_string+0x50/0x50 [vrouter]
44346 Jul 26 23:17:32 localhost kernel: [118557.450435]  [<ffffffffa016dac0>] ? thrift_binary_protocol_write_i16+0x40/0x40 [vrouter]
44347 Jul 26 23:17:32 localhost kernel: [118557.450440]  [<ffffffffa016da80>] ? thrift_binary_protocol_write_i32+0x30/0x30 [vrouter]
44348 Jul 26 23:17:32 localhost kernel: [118557.450445]  [<ffffffffa016da50>] ? thrift_binary_protocol_write_i64+0x60/0x60 [vrouter]
44349 Jul 26 23:17:32 localhost kernel: [118557.450450]  [<ffffffffa016d9f0>] ? thrift_binary_protocol_write_u16+0x40/0x40 [vrouter]
44350 Jul 26 23:17:32 localhost kernel: [118557.450455]  [<ffffffffa016d9b0>] ? thrift_binary_protocol_write_ipv4+0x10/0x10 [vrouter]
44351 Jul 26 23:17:32 localhost kernel: [118557.450460]  [<ffffffffa016d970>] ? thrift_binary_protocol_write_u64+0x60/0x60 [vrouter]
44352 Jul 26 23:17:32 localhost kernel: [118557.450465]  [<ffffffffa016d910>] ? thrift_binary_protocol_write_binary+0x90/0x90 [vrouter]
44353 Jul 26 23:17:32 localhost kernel: [118557.450469]  [<ffffffffa016d9a0>] ? thrift_binary_protocol_write_u32+0x30/0x30 [vrouter]
44354 Jul 26 23:17:32 localhost kernel: [118557.450474]  [<ffffffffa016cfe0>] ? thrift_binary_protocol_write_set_end+0x10/0x10 [vrouter]
44355 Jul 26 23:17:32 localhost kernel: [118557.450479]  [<ffffffffa016daf0>] ? thrift_binary_protocol_write_byte+0x30/0x30 [vrouter]
44356 Jul 26 23:17:32 localhost kernel: [118557.450484]  [<ffffffffa016d880>] ? thrift_binary_protocol_read_message_begin+0x100/0x100 [vrouter]
44357 Jul 26 23:17:32 localhost kernel: [118557.450489]  [<ffffffffa016daf0>] ? thrift_binary_protocol_write_byte+0x30/0x30 [vrouter]
44358 Jul 26 23:17:32 localhost kernel: [118557.450494]  [<ffffffffa016d760>] ? thrift_binary_protocol_read_field_begin+0xa0/0xa0 [vrouter]
44359 Jul 26 23:17:32 localhost kernel: [118557.450500]  [<ffffffffa016d000>] ? thrift_binary_protocol_read_message_end+0x10/0x10 [vrouter]
44360 Jul 26 23:17:32 localhost kernel: [118557.450504]  [<ffffffffa016d780>] ? thrift_binary_protocol_read_sandesh_begin+0x20/0x20 [vrouter]
44361 Jul 26 23:17:32 localhost kernel: [118557.450510]  [<ffffffffa016cff0>] ? thrift_binary_protocol_write_double+0x10/0x10 [vrouter]
44362 Jul 26 23:17:32 localhost kernel: [118557.450515]  [<ffffffffa016d010>] ? thrift_binary_protocol_read_sandesh_end+0x10/0x10 [vrouter]
44363 Jul 26 23:17:32 localhost kernel: [118557.450520]  [<ffffffffa016d030>] ? thrift_binary_protocol_read_struct_begin+0x20/0x20 [vrouter]
44364 Jul 26 23:17:32 localhost kernel: [118557.450525]  [<ffffffffa016d6c0>] ? thrift_binary_protocol_read_map_begin+0xd0/0xd0 [vrouter]
44365 Jul 26 23:17:32 localhost kernel: [118557.450530]  [<ffffffffa016d040>] ? thrift_binary_protocol_read_struct_end+0x10/0x10 [vrouter]
44366 Jul 26 23:17:32 localhost kernel: [118557.450535]  [<ffffffffa016d5f0>] ? thrift_binary_protocol_read_list_begin+0xb0/0xb0 [vrouter]
44367 Jul 26 23:17:32 localhost kernel: [118557.450540]  [<ffffffffa016d050>] ? thrift_binary_protocol_read_field_end+0x10/0x10 [vrouter]
44368 Jul 26 23:17:32 localhost kernel: [118557.450545]  [<ffffffffa016d540>] ? thrift_binary_protocol_read_set_begin+0x10/0x10 [vrouter]
44369 Jul 26 23:17:32 localhost kernel: [118557.450550]  [<ffffffffa016d060>] ? thrift_binary_protocol_read_map_end+0x10/0x10 [vrouter]
44370 Jul 26 23:17:32 localhost kernel: [118557.450554]  [<ffffffffa016d530>] ? thrift_binary_protocol_read_string+0xd0/0xd0 [vrouter]
44371 Jul 26 23:17:32 localhost kernel: [118557.450559]  [<ffffffffa016d070>] ? thrift_binary_protocol_read_list_end+0x10/0x10 [vrouter]
44372 Jul 26 23:17:32 localhost kernel: [118557.450564]  [<ffffffffa016d1e0>] ? thrift_binary_protocol_read_byte+0x50/0x50 [vrouter]
44373 Jul 26 23:17:32 localhost kernel: [118557.450569]  [<ffffffffa016d190>] ? thrift_binary_protocol_read_i64+0x80/0x80 [vrouter]
44374 Jul 26 23:17:32 localhost kernel: [118557.450574]  [<ffffffffa016d330>] ? thrift_binary_protocol_read_i32+0x50/0x50 [vrouter]
44375 Jul 26 23:17:32 localhost kernel: [118557.450579]  [<ffffffffa016d2e0>] ? thrift_binary_protocol_read_u16+0x50/0x50 [vrouter]
44376 Jul 26 23:17:32 localhost kernel: [118557.450584]  [<ffffffffa016d110>] ? thrift_binary_protocol_read_u64+0x80/0x80 [vrouter]
44377 Jul 26 23:17:32 localhost kernel: [118557.450589]  [<ffffffffa016d290>] ? thrift_binary_protocol_read_ipv4+0x10/0x10 [vrouter]
44378 Jul 26 23:17:32 localhost kernel: [118557.450593]  [<ffffffffa016d230>] ? thrift_binary_protocol_read_bool+0x50/0x50 [vrouter]
44379 Jul 26 23:17:32 localhost kernel: [118557.450598]  [<ffffffffa016d090>] ? thrift_binary_protocol_read_double+0x10/0x10 [vrouter]
44380 Jul 26 23:17:32 localhost kernel: [118557.450603]  [<ffffffffa016d280>] ? thrift_binary_protocol_read_u32+0x50/0x50 [vrouter]
44381 Jul 26 23:17:32 localhost kernel: [118557.450608]  [<ffffffffa016d080>] ? thrift_binary_protocol_read_set_end+0x10/0x10 [vrouter]
44382 Jul 26 23:17:32 localhost kernel: [118557.450613]  [<ffffffffa016d460>] ? thrift_binary_protocol_read_binary+0xe0/0xe0 [vrouter]
44383 Jul 26 23:17:32 localhost kernel: [118557.450618]  [<ffffffffa016d380>] ? thrift_binary_protocol_read_i16+0x50/0x50 [vrouter]
44384 Jul 26 23:17:32 localhost kernel: [118557.450622]  [<ffffffffa016d460>] ? thrift_binary_protocol_read_binary+0xe0/0xe0 [vrouter]
44385 Jul 26 23:17:32 localhost kernel: [118557.450628]  [<ffffffffa016e130>] ? thrift_transport_flush+0x20/0x20 [vrouter]
44386 Jul 26 23:17:32 localhost kernel: [118557.450634]  [<ffffffffa016e140>] ? thrift_memory_buffer_is_open+0x10/0x10 [vrouter]
44387 Jul 26 23:17:32 localhost kernel: [118557.450639]  [<ffffffffa016e150>] ? thrift_memory_buffer_open+0x10/0x10 [vrouter]
44388 Jul 26 23:17:32 localhost kernel: [118557.450644]  [<ffffffffa016e190>] ? thrift_memory_buffer_flush+0x10/0x10 [vrouter]
44389 Jul 26 23:17:32 localhost kernel: [118557.450649]  [<ffffffffa016e160>] ? thrift_memory_buffer_close+0x10/0x10 [vrouter]
44390 Jul 26 23:17:32 localhost kernel: [118557.450654]  [<ffffffffa016e220>] ? thrift_memory_buffer_read+0x90/0x90 [vrouter]
44391 Jul 26 23:17:32 localhost kernel: [118557.450659]  [<ffffffffa016e170>] ? thrift_memory_buffer_read_end+0x10/0x10 [vrouter]
44392 Jul 26 23:17:32 localhost kernel: [118557.450664]  [<ffffffffa016e180>] ? thrift_memory_buffer_write_end+0x10/0x10 [vrouter]
44393 Jul 26 23:17:32 localhost kernel: [118557.450669]  [<ffffffffa016c170>] ? sandesh_hdr_free+0x10/0x10 [vrouter]
44394 Jul 26 23:17:32 localhost kernel: [118557.450674]  [<ffffffffa016c426>] sandesh_decode+0x46/0x80 [vrouter]
44395 Jul 26 23:17:32 localhost kernel: [118557.450681]  [<ffffffffa01746e4>] sandesh_proto_decode+0x24/0x30 [vrouter]
44396 Jul 26 23:17:32 localhost kernel: [118557.450688]  [<ffffffffa0174130>] vr_message_request+0x40/0x50 [vrouter]
44397 Jul 26 23:17:32 localhost kernel: [118557.450694]  [<ffffffffa0173b1c>] netlink_trans_request+0x5c/0x210 [vrouter]
44398 Jul 26 23:17:32 localhost kernel: [118557.450699]  [<ffffffff8156ea8f>] ? genl_family_find_byid+0x2f/0x60
44399 Jul 26 23:17:32 localhost kernel: [118557.450702]  [<ffffffff8156ef65>] genl_rcv_msg+0x1d5/0x250
44400 Jul 26 23:17:32 localhost kernel: [118557.450705]  [<ffffffff8156e0fe>] ? netlink_unicast+0x2be/0x300
44401 Jul 26 23:17:32 localhost kernel: [118557.450708]  [<ffffffff8156ed90>] ? genl_rcv+0x40/0x40
44402 Jul 26 23:17:32 localhost kernel: [118557.450710]  [<ffffffff8156e829>] netlink_rcv_skb+0xa9/0xd0
44403 Jul 26 23:17:32 localhost kernel: [118557.450713]  [<ffffffff8156ed75>] genl_rcv+0x25/0x40
44404 Jul 26 23:17:32 localhost kernel: [118557.450716]  [<ffffffff8156e0f0>] netlink_unicast+0x2b0/0x300
44405 Jul 26 23:17:32 localhost kernel: [118557.450719]  [<ffffffff8153688c>] ? __alloc_skb+0x8c/0x240
44406 Jul 26 23:17:32 localhost kernel: [118557.450722]  [<ffffffff8156e41e>] netlink_sendmsg+0x2de/0x390
44407 Jul 26 23:17:32 localhost kernel: [118557.450726]  [<ffffffff8152c99e>] sock_sendmsg+0x10e/0x130
44408 Jul 26 23:17:32 localhost kernel: [118557.450730]  [<ffffffff8105668d>] ? set_next_entity+0xad/0xd0
44409 Jul 26 23:17:32 localhost kernel: [118557.450733]  [<ffffffff8105682a>] ? finish_task_switch+0x4a/0xf0
44410 Jul 26 23:17:32 localhost kernel: [118557.450737]  [<ffffffff8152efc4>] ? move_addr_to_kernel+0x64/0x70
44411 Jul 26 23:17:32 localhost kernel: [118557.450740]  [<ffffffff8153a4c2>] ? verify_iovec+0x52/0xd0
44412 Jul 26 23:17:32 localhost kernel: [118557.450743]  [<ffffffff8152e01f>] ___sys_sendmsg+0x3bf/0x3e0
44413 Jul 26 23:17:32 localhost kernel: [118557.450752]  [<ffffffff8106074e>] ? try_to_wake_up+0x18e/0x200
44414 Jul 26 23:17:32 localhost kernel: [118557.450755]  [<ffffffff81060ae0>] ? wake_up_state+0x10/0x20
44415 Jul 26 23:17:32 localhost kernel: [118557.450764]  [<ffffffff8109e466>] ? wake_futex+0x76/0xa0
44416 Jul 26 23:17:32 localhost kernel: [118557.450767]  [<ffffffff8109f7c3>] ? futex_wake+0x113/0x130
44417 Jul 26 23:17:32 localhost kernel: [118557.450771]  [<ffffffff8152ff39>] __sys_sendmsg+0x49/0x90
44418 Jul 26 23:17:32 localhost kernel: [118557.450774]  [<ffffffff8152ff99>] sys_sendmsg+0x19/0x20
44419 Jul 26 23:17:32 localhost kernel: [118557.450780]  [<ffffffff81665842>] system_call_fastpath+0x16/0x1b

I got that trace 12 hours later again, but the test continue to work 2 days more without any errors.
I remark another problem. 3 days after I started the test, the loop test take 30 seconds more to run (ie. 5-6 seconds at the beginning and 35 seconds 3 days after).