{"action":"closed","issue":{"url":"https://api.github.com/repos/multipath-tcp/mptcp/issues/74","labels_url":"https://api.github.com/repos/multipath-tcp/mptcp/issues/74/labels{/name}","comments_url":"https://api.github.com/repos/multipath-tcp/mptcp/issues/74/comments","events_url":"https://api.github.com/repos/multipath-tcp/mptcp/issues/74/events","html_url":"https://github.com/multipath-tcp/mptcp/issues/74","id":59315719,"number":74,"title":"kernel BUG at net/ipv4/tcp_input.c:4621!","user":{"login":"pRiVi","id":375391,"avatar_url":"https://avatars.githubusercontent.com/u/375391?v=3","gravatar_id":"","url":"https://api.github.com/users/pRiVi","html_url":"https://github.com/pRiVi","followers_url":"https://api.github.com/users/pRiVi/followers","following_url":"https://api.github.com/users/pRiVi/following{/other_user}","gists_url":"https://api.github.com/users/pRiVi/gists{/gist_id}","starred_url":"https://api.github.com/users/pRiVi/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/pRiVi/subscriptions","organizations_url":"https://api.github.com/users/pRiVi/orgs","repos_url":"https://api.github.com/users/pRiVi/repos","events_url":"https://api.github.com/users/pRiVi/events{/privacy}","received_events_url":"https://api.github.com/users/pRiVi/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/multipath-tcp/mptcp/labels/bug","name":"bug","color":"fc2929"},{"url":"https://api.github.com/repos/multipath-tcp/mptcp/labels/Level:%20Critical","name":"Level: Critical","color":"e11d21"}],"state":"closed","locked":false,"assignee":null,"milestone":null,"comments":17,"created_at":"2015-02-28T00:49:40Z","updated_at":"2015-12-26T20:55:00Z","closed_at":"2015-12-26T20:55:00Z","body":"### Description\r\n\r\nA simple OpenVPN MPTCP Tunnel, transfering data via a single tcp connection over NAT from Internet. The flow of data increases (tcp slowstart?) and then, after some seconds, it just drops to 0. In this situation also no PING is possible between the two systems. But running SSH conntions work! For about 20 seconds no data at all gets transfered. The tcp connection is not reseted, just paused. Then again there is tcp slowstart.\r\n\r\nThis runs into a loop (dropping to 0, stay at 0 for 20 seconds, slowstart, dropinng to 0,  stay at 0 for 20 seconds, slowstart, ...).\r\n\r\nThen, after some minutes running this loop, you get this crash.\r\n\r\nInternet <-> XEN MPTCP with OpenVPN Server and NAT (this crashes) <-> Internet <-> MPTCP Client (no Xen) with OpenVPN Client <-> Client downloading\r\n\r\nAs the system is just a test system at hetzner, I can give you access to the system if it might be helpfull.\r\n\r\n### XEN Host\r\n- Host is Debian Jessie\r\n- XEN 4.4 installed on Host via \"apt get install xen-hypervisor\"\r\n\r\n### XEN Guest (MPTCP)\r\n- Guest is Debian Wheezy\r\n- MPTCP Kernel Installed via http://multipath-tcp.org/pmwiki.php/Users/AptRepository\r\n- Started system paravirtualised; config is:\r\n```\r\nmemory=4096\r\nkernel=\"/mnt/xen-current/mpvpn/boot/vmlinuz-3.14.33.wheezymptcp\"\r\nramdisk=\"/mnt/xen-current/mpvpn/boot/initrd.img-3.14.33.wheezymptcp\"\r\nextra=\"ip=192.0.0.23:::255.255.255.0::eth0: nfsroot=192.0.0.1:/mnt/xen-current/mpvpn/,v3,tcp root=/dev/nfs xencons=tty\"\r\nvif=[\"bridge=br255\",\"bridge=br1\",\"bridge=br0\"]\r\nname=\"mpvpn\"\r\nvcpus=4\r\ncpus=\"0-7\"\r\non_crash=\"preserve\"\r\nvnclisten=\"127.0.0.1\"\r\n```\r\n\r\nIPtables is the following:\r\n```\r\n*filter\r\n:INPUT ACCEPT [1063:961625]\r\n:FORWARD ACCEPT [0:0]\r\n:OUTPUT ACCEPT [1129:168324]\r\n-A FORWARD -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu\r\nCOMMIT\r\n# Completed on Sat Feb 28 01:55:29 2015\r\n# Generated by iptables-save v1.4.14 on Sat Feb 28 01:55:29 2015\r\n*nat\r\n:PREROUTING ACCEPT [112:32280]\r\n:INPUT ACCEPT [112:32280]\r\n:OUTPUT ACCEPT [18:1360]\r\n:POSTROUTING ACCEPT [0:0]\r\n-A POSTROUTING -j MASQUERADE\r\nCOMMIT\r\n```\r\n\r\n### Crash\r\n\r\n```\r\n[31612.783126] ------------[ cut here ]------------\r\n[31612.783137] kernel BUG at net/ipv4/tcp_input.c:4621!\r\n[31612.783140] invalid opcode: 0000 [#1] SMP\r\n[31612.783143] Modules linked in: xt_TCPMSS xt_tcpudp iptable_filter ipt_MASQUERADE iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack ip_tables x_tables tun nfsd auth_rpcgss oid_registry x86_pkg_temp_thermal thermal_sys intel_rapl coretemp crct10dif_pclmul crct10dif_common crc32_pclmul crc32c_intel evdev ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd snd_pcm snd_timer snd soundcore pcspkr nfsv3 nfs_acl nfs lockd sunrpc fscache xen_netfront\r\n[31612.783178] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.14.33.wheezymptcp #38\r\n[31612.783181] task: ffffffff81813480 ti: ffffffff81800000 task.ti: ffffffff81800000\r\n[31612.783185] RIP: e030:[<ffffffff81454337>]  [<ffffffff81454337>] tcp_collapse+0x367/0x370\r\n[31612.783192] RSP: e02b:ffff8800ff203ad8  EFLAGS: 00010287\r\n[31612.783195] RAX: ffffffff8188bd20 RBX: ffff880003036dc0 RCX: 0000284900000000\r\n[31612.783198] RDX: 0000000000001100 RSI: ffff8800f8864096 RDI: ffff880002dcb096\r\n[31612.783201] RBP: ffff880002c8c040 R08: 00000000000015df R09: 00000000fffff450\r\n[31612.783204] R10: 0000000000000880 R11: 0000000000000059 R12: 0000000064f2ec50\r\n[31612.783207] R13: ffff8800f8a03e00 R14: 0000000000000000 R15: ffff8800f8a03800\r\n[31612.783213] FS:  00007fbf5ba6d700(0000) GS:ffff8800ff200000(0000) knlGS:0000000000000000\r\n[31612.783216] CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033\r\n[31612.783219] CR2: ffffffffff600400 CR3: 00000000f8fb4000 CR4: 0000000000042660\r\n[31612.783222] Stack:\r\n[31612.783224]  0000000000004100 0000000000000096 0000000000000096 64f3022f00000e2a\r\n[31612.783229]  a17fc79900000000 ffff8800f8a03e00 0000000000001380 ffff88000310e580\r\n[31612.783233]  ffff8800f8a03800 ffff8800f8a03e00 ffff8800f7f3f85a ffffffff81454dc0\r\n[31612.783238] Call Trace:\r\n[31612.783240]  <IRQ>\r\n[31612.783242]  [<ffffffff81454dc0>] ? tcp_try_rmem_schedule+0x150/0x3b0\r\n[31612.783248]  [<ffffffff814592de>] ? tcp_data_queue+0x28e/0xdb0\r\n[31612.783252]  [<ffffffff81459f39>] ? tcp_rcv_established+0x139/0x710\r\n[31612.783256]  [<ffffffffa0217296>] ? nf_nat_ipv4_fn+0x216/0x310 [iptable_nat]\r\n[31612.783262]  [<ffffffff81465c37>] ? tcp_v4_do_rcv+0x257/0x420\r\n[31612.783266]  [<ffffffffa0211e2e>] ? ipv4_confirm+0x6e/0xf0 [nf_conntrack_ipv4]\r\n[31612.783271]  [<ffffffff814402c0>] ? ip_rcv_finish+0x370/0x370\r\n[31612.783275]  [<ffffffff8146667f>] ? tcp_v4_rcv+0x70f/0x8d0\r\n[31612.783278]  [<ffffffff81439bde>] ? nf_hook_slow+0x6e/0x130\r\n[31612.783282]  [<ffffffff814402c0>] ? ip_rcv_finish+0x370/0x370\r\n[31612.783285]  [<ffffffff81440356>] ? ip_local_deliver_finish+0x96/0x1f0\r\n[31612.783290]  [<ffffffff8140991b>] ? __netif_receive_skb_core+0x63b/0x800\r\n[31612.783294]  [<ffffffff81409cf4>] ? netif_receive_skb_internal+0x24/0x80\r\n[31612.783299]  [<ffffffff81409ed2>] ? napi_gro_flush+0x62/0x80\r\n[31612.783304]  [<ffffffffa0001f96>] ? xennet_poll+0xa26/0xb70 [xen_netfront]\r\n[31612.783308]  [<ffffffff8140a088>] ? net_rx_action+0x138/0x240\r\n[31612.783313]  [<ffffffff81068887>] ? __do_softirq+0xf7/0x280\r\n[31612.783319]  [<ffffffff81068c45>] ? irq_exit+0x95/0xa0\r\n[31612.783326]  [<ffffffff81347107>] ? xen_evtchn_do_upcall+0x27/0x40\r\n[31612.783332]  [<ffffffff8151a1fe>] ? xen_do_hypervisor_callback+0x1e/0x30\r\n[31612.783335]  <EOI>\r\n[31612.783336]  [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20\r\n[31612.783342]  [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20\r\n[31612.783347]  [<ffffffff8100a15c>] ? xen_safe_halt+0xc/0x20\r\n[31612.783352]  [<ffffffff8101d8ad>] ? default_idle+0x1d/0xb0\r\n[31612.783356]  [<ffffffff810b75a1>] ? cpu_startup_entry+0x91/0x240\r\n[31612.783360]  [<ffffffff818ccf22>] ? start_kernel+0x424/0x42f\r\n[31612.783363]  [<ffffffff818cc915>] ? repair_env_string+0x5b/0x5b\r\n[31612.783368]  [<ffffffff810b3da3>] ? __add_preferred_console+0xb3/0xe0\r\n[31612.783372]  [<ffffffff818ced5f>] ? xen_start_kernel+0x515/0x51d\r\n[31612.783374] Code: fe ff ff e9 93 fd ff ff 0f 1f 40 00 48 89 de 4c 89 ea 4c 89 ff e8 0a f8 ff ff 48 85 c0 48 89 c3 0f 85 c0 fc ff ff e9 70 fd ff ff <0f> 0b 0f 0b 0f 1f 44 00 00 41 57 41 56 4c 8d b6 20 01 00 00 41\r\n[31612.783405] RIP  [<ffffffff81454337>] tcp_collapse+0x367/0x370\r\n[31612.783409]  RSP <ffff8800ff203ad8>\r\n[31612.783420] ---[ end trace 39dabca8449f41fc ]---\r\n[31612.783423] Kernel panic - not syncing: Fatal exception in interrupt\r\n```\r\n"}}