Re: Problem on SCTP

From: Neil Horman
Date: Wed Jan 11 2017 - 07:58:19 EST

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@xxxxxxxxxxxxx> 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@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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> >> >>
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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
> >
>