Re: Problem on SCTP

[Neil Horman]

On Tue, Jan 10, 2017 at 09:30:39AM +0800, Sun Paul wrote:
> Packet received (From client)
> ======================
> 
> No.     Time                          Source                SPort
> Destination           Protocol DPort  Length Info
>                                       DSCP
>       1 2017-01-06 08:52:49.662142    192.168.206.83        50001
> 192.168.206.65        SCTP     3868   98     INIT
>                                       CS0
> 
> Frame 1: 98 bytes on wire (784 bits), 98 bytes captured (784 bits)
>     Encapsulation type: Ethernet (1)
>     Arrival Time: Jan  6, 2017 16:52:49.662142000 Malay Peninsula Standard Time
>     [Time shift for this packet: 0.000000000 seconds]
>     Epoch Time: 1483692769.662142000 seconds
>     [Time delta from previous captured frame: 0.000000000 seconds]
>     [Time delta from previous displayed frame: 0.000000000 seconds]
>     [Time since reference or first frame: 0.000000000 seconds]
>     Frame Number: 1
>     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: RealtekU_54:81:87 (52:54:00:54:81:87), Dst:
> Vmware_81:41:6b (00:50:56:81:41:6b)
>     Destination: 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)
>     Source: RealtekU_54:81:87 (52:54:00:54:81:87)
>         Address: RealtekU_54:81:87 (52:54:00:54:81:87)
>         .... ..1. .... .... .... .... = LG bit: Locally administered
> address (this is NOT the factory default)
>         .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
>     Type: IPv4 (0x0800)
> Internet Protocol Version 4, Src: 192.168.206.83, Dst: 192.168.206.65
>     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: 64
>     Protocol: SCTP (132)
>     Header checksum: 0x1c3e [validation disabled]
>         [Good: False]
>         [Bad: False]
>     Source: 192.168.206.83
>     Destination: 192.168.206.65
>     [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: 0xbaea49e5 (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
> 
> 
> On Tue, Jan 10, 2017 at 3:18 AM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> > On Tue, Jan 10, 2017 at 12:31:01AM +0800, Sun Paul wrote:
> >> what kind of information do you need? the whole INIT packet?
> >>
> > That would be ideal.
> >
> >> On Mon, Jan 9, 2017 at 8:25 PM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> >> > On Mon, Jan 09, 2017 at 06:00:36PM +0800, Sun Paul wrote:
> >> >> Hi
> >> >>
> >> >> the linux router just change the destination, so it can arrive on the
> >> >> the SERVER.
> >> >>
> >> > Please post the relevant snippets from the client and server tcpdump
> >> > operations
> >> >
> >> > Neil
> >> >
> >> >> On Mon, Jan 9, 2017 at 5:51 PM, David Laight <David.Laight@xxxxxxxxxx> wrote:
> >> >> > From: Sun Paul
> >> >> >> Sent: 09 January 2017 02:08
> >> >> >
> >> >> >> >> I am setting up a lab where the SCTP traffics from  client is passing
> >> >> >> >> through a linux router before reaching to the SCTP server running
> >> >> >> >> LKSCTP.
> >> >> >> >>
> >> >> >> >> The linux router did not change the source address of the client, so
> >> >> >> >> when it arrived to the SCTP server, the source address is the oriingal
> >> >> >> >> one.
> >> >> >>
> >> >> >> the INIT chunk arrive on the SERVER, but then no response. the
> >> >> >> application that using in SERVER is the same as the other test.
> >> >> >>
> >> >> >> I noticed one thing in Ethernet frame of the incoming packet on the
> >> >> >> SERVER compared to the one captured from the client is the LG bit on
> >> >> >> the source address.
> >> >> >>
> >> >> >> The LG bit is set to 0 on the request packet received in the
> >> >> >> SERVER,but it is 0 from the one originated on the client. willl it be
> >> >> >> the root cause?
> >> >> >
> >> >> > Which addresses are you talking about, and what do you mean by the LG bit?
> >> >> >
> >> >> > Is your linux 'router' just routing (ie IP forwarding) or is it doing NAT?
> >> >> > If it is changing the IP addresses then the addresses inside some SCTP
> >> >> > chunks also need changing.
> >> >> >
> >> >> >         David
> >> >> >
> >> >>
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> 

It looks like you have some destination NAT-ing going on in these packets.  In
one trace your destination address is 192.168.206.65, and in the other its
192.168.206.66.

Neil