Date:   Mon, 27 Feb 2017 17:01:05 +0800
From:   Sun Paul <paulrbk@...il.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     Michael Tuexen <Michael.Tuexen@...chi.franken.de>,
        David Laight <David.Laight@...lab.com>,
        Neil Horman <nhorman@...driver.com>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Problem on SCTP

Hi, can I confirm that the problem is on the Linux router itself or on
both server and client?

On Thu, Feb 23, 2017 at 2:07 PM, Xin Long <lucien.xin@...il.com> wrote:
> On Thu, Feb 23, 2017 at 1:30 PM, Sun Paul <paulrbk@...il.com> wrote:
>> does this fixed in RHEL7?
> yes, I think so.
>
>>
>> On Wed, Feb 22, 2017 at 11:03 AM, Xin Long <lucien.xin@...il.com> wrote:
>>> On Wed, Feb 22, 2017 at 10:29 AM, Sun Paul <paulrbk@...il.com> wrote:
>>>> Hi Xin
>>>>
>>>> do you mean we need to patch the kernel?
>>> Yups, pls comment on that bz if it's really needed for your env.
>>> A z-stream kernel may be available for that issue soon.
>>>
>>> Thanks.
>>>
>>>>
>>>>
>>>>
>>>> On Wed, Feb 22, 2017 at 10:00 AM, Xin Long <lucien.xin@...il.com> wrote:
>>>>> On Wed, Feb 22, 2017 at 9:12 AM, Sun Paul <paulrbk@...il.com> wrote:
>>>>>> Hi
>>>>>>
>>>>>> the router is actually is a linux running on RHEL6.8
>>>>>> (2.6.32-642.4.2.el6.x86_64). it uses iptables to do SNAT aand DNAT
>>>>>> forward.
>>>>> https://bugzilla.redhat.com/show_bug.cgi?id=1412038
>>>>>
>>>>> sctp_manip_pkt->sctp_compute_cksum:
>>>>>     struct sctphdr *sh = sctp_hdr(sub);
>>>>>
>>>>> But in rhel6, skb->transport_header is not yet set at that time.
>>>>> This patch should be backported into rhel6.
>>>>>
>>>>> commit 21d1196a35f5686c4323e42a62fdb4b23b0ab4a3
>>>>> Author: Eric Dumazet <edumazet@...gle.com>
>>>>> Date:   Mon Jul 15 20:03:19 2013 -0700
>>>>>
>>>>>     ipv4: set transport header earlier
>>>>>
>>>>>
>>>>>>
>>>>>> On Tue, Feb 21, 2017 at 11:53 PM, Xin Long <lucien.xin@...il.com> wrote:
>>>>>>> On Tue, Feb 21, 2017 at 12:26 PM, Sun Paul <paulrbk@...il.com> wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> sorry to get back late, the platform is running on KVM. and this
>>>>>>>> problem is resolved by moving to VMware environment, however,  a new
>>>>>>>> problem is coming out, we noticed that the HB REQ is being ABORT from
>>>>>>>> client.
>>>>>>>>
>>>>>>>>
>>>>>>>> 03:32:35.233572 IP 10.165.250.22.3868 > 192.168.2.13.40001: sctp (1)
>>>>>>>> [HB REQ] (from server to sctp router)
>>>>>>>> 03:32:35.233603 IP 192.168.2.14.3868 > 192.168.2.13.40001: sctp (1)
>>>>>>>> [HB REQ] (from sctp router to client)
>>>>>>>> 03:32:35.233852 IP 192.168.2.13.40001 > 192.168.2.14.3868: sctp (1)
>>>>>>>> [ABORT] (from client to sctp router)
>>>>>>>>
>>>>>>>> 03:32:37.928679 IP 10.165.250.22.3868 > 192.168.2.13.40001: sctp (1) [HB REQ]
>>>>>>>> 03:32:37.928717 IP 192.168.2.14.3868 > 192.168.2.13.40001: sctp (1) [HB REQ]
>>>>>>>> 03:32:37.929247 IP 192.168.2.13.40001 > 192.168.2.14.3868: sctp (1) [ABORT]
>>>>>>>>
>>>>>>>> For the above packet flow, 10.165.250.22 is the server and
>>>>>>>> 192.168.2.13 is the client, the server 10.165.250.22 sends HB REQ to
>>>>>>>> client 192.168.2.13 through 192.168.2.14 (the SCTP router), and the
>>>>>>>> SCTP router change the src address before forward the HB REQ to the
>>>>>>>> client.
>>>>>>>>
>>>>>>>> But somehow the client is ABORT the HB REQ, any idea? is it related to
>>>>>>>> the HEARTBEAT information? or the checksum again>?
>>>>>>> The incorrect checksum won't cause ABORT, but the abnormal HB REQ
>>>>>>> could be, if HB information was modified when calculating the checksum
>>>>>>> on router, the ABORT may be caused in client process.
>>>>>>>
>>>>>>> is your SCTP router linux ? if yes, what's the kernel version ?
>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, Jan 13, 2017 at 9:19 PM, Michael Tuexen
>>>>>>>> <Michael.Tuexen@...chi.franken.de> wrote:
>>>>>>>>>> On 13 Jan 2017, at 10:43, Michael Tuexen <Michael.Tuexen@...chi.franken.de> wrote:
>>>>>>>>>>
>>>>>>>>>> Your router does NOT change any field in the SCTP packet, but the
>>>>>>>>>> SCTP checksum was modified from
>>>>>>>>>>   Checksum: 0xbaea49e5 (not verified)
>>>>>>>>>> to
>>>>>>>>>>   Checksum: 0xa9a86d3f (not verified)
>>>>>>>>>> At least one of these is wrong. Read the tracefiles in wireshark and
>>>>>>>>>> enable checksum validation and wireshark will tell you which one is
>>>>>>>>>> correct. (That is why I asked for .pcap file instead of a .txt).
>>>>>>>>>>
>>>>>>>>>> My guess is that the initial checksum is correct and your box middlebox
>>>>>>>>>> not only changes the destination address and ttl field and header
>>>>>>>>>> checksum in the IP-header (which is expected) but also incorrectly the
>>>>>>>>>> SCTP checksum. Since no field in the SCTP packet has changed, the checksum
>>>>>>>>>> must be the same.
>>>>>>>>> At the server have a look at the SNMP counters:
>>>>>>>>> cat /proc/net/sctp/snmp
>>>>>>>>> You should find a line staring with
>>>>>>>>> SctpChecksumErrors
>>>>>>>>> If the number reported there is positive, the node received packets
>>>>>>>>> with checksum errors.
>>>>>>>>>
>>>>>>>>> Best regards
>>>>>>>>> Michael
>>>>>>>>>>
>>>>>>>>>> Best regards
>>>>>>>>>> Michael
>>>>>>>>>>> On 13 Jan 2017, at 04:29, Sun Paul <paulrbk@...il.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>> Frame 2: 98 bytes on wire (784 bits), 98 bytes captured (784 bits)
>>>>>>>>>>>   Encapsulation type: Ethernet (1)
>>>>>>>>>>>   Arrival Time: Jan  6, 2017 16:52:49.662321000 Malay Peninsula Standard Time
>>>>>>>>>>>   [Time shift for this packet: 0.000000000 seconds]
>>>>>>>>>>>   Epoch Time: 1483692769.662321000 seconds
>>>>>>>>>>>   [Time delta from previous captured frame: 0.000179000 seconds]
>>>>>>>>>>>   [Time delta from previous displayed frame: 0.000179000 seconds]
>>>>>>>>>>>   [Time since reference or first frame: 0.000179000 seconds]
>>>>>>>>>>>   Frame Number: 2
>>>>>>>>>>>   Frame Length: 98 bytes (784 bits)
>>>>>>>>>>>   Capture Length: 98 bytes (784 bits)
>>>>>>>>>>>   [Frame is marked: False]
>>>>>>>>>>>   [Frame is ignored: False]
>>>>>>>>>>>   [Protocols in frame: eth:ethertype:ip:sctp]
>>>>>>>>>>> Ethernet II, Src: Vmware_81:41:6b (00:50:56:81:41:6b), Dst:
>>>>>>>>>>> Vmware_81:a6:a3 (00:50:56:81:a6:a3)
>>>>>>>>>>>   Destination: Vmware_81:a6:a3 (00:50:56:81:a6:a3)
>>>>>>>>>>>       Address: Vmware_81:a6:a3 (00:50:56:81:a6:a3)
>>>>>>>>>>>       .... ..0. .... .... .... .... = LG bit: Globally unique
>>>>>>>>>>> address (factory default)
>>>>>>>>>>>       .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
>>>>>>>>>>>   Source: Vmware_81:41:6b (00:50:56:81:41:6b)
>>>>>>>>>>>       Address: Vmware_81:41:6b (00:50:56:81:41:6b)
>>>>>>>>>>>       .... ..0. .... .... .... .... = LG bit: Globally unique
>>>>>>>>>>> address (factory default)
>>>>>>>>>>>       .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
>>>>>>>>>>>   Type: IPv4 (0x0800)
>>>>>>>>>>> Internet Protocol Version 4, Src: 192.168.206.83, Dst: 192.168.206.66
>>>>>>>>>>>   0100 .... = Version: 4
>>>>>>>>>>>   .... 0101 = Header Length: 20 bytes (5)
>>>>>>>>>>>   Differentiated Services Field: 0x02 (DSCP: CS0, ECN: ECT(0))
>>>>>>>>>>>       0000 00.. = Differentiated Services Codepoint: Default (0)
>>>>>>>>>>>       .... ..10 = Explicit Congestion Notification: ECN-Capable
>>>>>>>>>>> Transport codepoint '10' (2)
>>>>>>>>>>>   Total Length: 84
>>>>>>>>>>>   Identification: 0x0000 (0)
>>>>>>>>>>>   Flags: 0x02 (Don't Fragment)
>>>>>>>>>>>       0... .... = Reserved bit: Not set
>>>>>>>>>>>       .1.. .... = Don't fragment: Set
>>>>>>>>>>>       ..0. .... = More fragments: Not set
>>>>>>>>>>>   Fragment offset: 0
>>>>>>>>>>>   Time to live: 63
>>>>>>>>>>>   Protocol: SCTP (132)
>>>>>>>>>>>   Header checksum: 0x1d3d [validation disabled]
>>>>>>>>>>>       [Good: False]
>>>>>>>>>>>       [Bad: False]
>>>>>>>>>>>   Source: 192.168.206.83
>>>>>>>>>>>   Destination: 192.168.206.66
>>>>>>>>>>>   [Source GeoIP: Unknown]
>>>>>>>>>>>   [Destination GeoIP: Unknown]
>>>>>>>>>>> Stream Control Transmission Protocol, Src Port: 50001 (50001), Dst
>>>>>>>>>>> Port: 3868 (3868)
>>>>>>>>>>>   Source port: 50001
>>>>>>>>>>>   Destination port: 3868
>>>>>>>>>>>   Verification tag: 0x00000000
>>>>>>>>>>>   [Assocation index: 0]
>>>>>>>>>>>   Checksum: 0xa9a86d3f (not verified)
>>>>>>>>>>>
>>>>>>>>>>>   INIT chunk (Outbound streams: 3000, inbound streams: 3000)
>>>>>>>>>>>       Chunk type: INIT (1)
>>>>>>>>>>>           0... .... = Bit: Stop processing of the packet
>>>>>>>>>>>           .0.. .... = Bit: Do not report
>>>>>>>>>>>       Chunk flags: 0x00
>>>>>>>>>>>       Chunk length: 52
>>>>>>>>>>>       Initiate tag: 0xe79f40cb
>>>>>>>>>>>       Advertised receiver window credit (a_rwnd): 62464
>>>>>>>>>>>       Number of outbound streams: 3000
>>>>>>>>>>>       Number of inbound streams: 3000
>>>>>>>>>>>       Initial TSN: 176990880
>>>>>>>>>>>       IPv4 address parameter (Address: 192.168.206.83)
>>>>>>>>>>>           Parameter type: IPv4 address (0x0005)
>>>>>>>>>>>               0... .... .... .... = Bit: Stop processing of chunk
>>>>>>>>>>>               .0.. .... .... .... = Bit: Do not report
>>>>>>>>>>>           Parameter length: 8
>>>>>>>>>>>           IP Version 4 address: 192.168.206.83
>>>>>>>>>>>       IPv4 address parameter (Address: 192.168.1.83)
>>>>>>>>>>>           Parameter type: IPv4 address (0x0005)
>>>>>>>>>>>               0... .... .... .... = Bit: Stop processing of chunk
>>>>>>>>>>>               .0.. .... .... .... = Bit: Do not report
>>>>>>>>>>>           Parameter length: 8
>>>>>>>>>>>           IP Version 4 address: 192.168.1.83
>>>>>>>>>>>       Supported address types parameter (Supported types: IPv6, IPv4)
>>>>>>>>>>>           Parameter type: Supported address types (0x000c)
>>>>>>>>>>>               0... .... .... .... = Bit: Stop processing of chunk
>>>>>>>>>>>               .0.. .... .... .... = Bit: Do not report
>>>>>>>>>>>           Parameter length: 8
>>>>>>>>>>>           Supported address type: IPv6 address (6)
>>>>>>>>>>>           Supported address type: IPv4 address (5)
>>>>>>>>>>>       ECN parameter
>>>>>>>>>>>           Parameter type: ECN (0x8000)
>>>>>>>>>>>               1... .... .... .... = Bit: Skip parameter and continue
>>>>>>>>>>> processing of the chunk
>>>>>>>>>>>               .0.. .... .... .... = Bit: Do not report
>>>>>>>>>>>           Parameter length: 4
>>>>>>>>>>>       Forward TSN supported parameter
>>>>>>>>>>>           Parameter type: Forward TSN supported (0xc000)
>>>>>>>>>>>               1... .... .... .... = Bit: Skip parameter and continue
>>>>>>>>>>> processing of the chunk
>>>>>>>>>>>               .1.. .... .... .... = Bit: Do report
>>>>>>>>>>>           Parameter length: 4
>>>>>>>>>>
>>>>>>>>>> --
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>>>>>>>>>
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