Date:   Wed, 11 Jan 2017 07:57:08 -0500
From:   Neil Horman <nhorman@...driver.com>
To:     Sun Paul <paulrbk@...il.com>
Cc:     David Laight <David.Laight@...lab.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

On Wed, Jan 11, 2017 at 04:39:29PM +0800, Sun Paul wrote:
> yes. whenever the INIT packet send to 192.168.206.65, it will forward
> to 192.168.206.66. My question is when this packet arrive to
> 192.168.206.66, why LKSCTP never pass to user level.
> 

Yes....soo, unlike what you said before, there is some address translation to
take into account here.  You need to be prepared for that:

https://docs.google.com/viewer?url=http://www.sigcomm.org/sites/default/files/ccr/papers/2009/January/1496091-1496095.pdf

Neil

> On Tue, Jan 10, 2017 at 10:33 PM, Neil Horman <nhorman@...driver.com> wrote:
> > 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@...driver.com> 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@...driver.com> 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@...lab.com> 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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> >> >>
> >> --
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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
> >
> 

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