Hi All below is the packet trace in text format. Packet received (From client to router) [ Source IP: 192.168.206.83, Destination IP: 192.168.206.65. the IPv4 address parameter is 192.168.206.83 and 192.168.1.83 ] ====================== 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 Thu, Jan 12, 2017 at 6:53 PM, Michael Tuexen <Michael.Tuexen@xxxxxxxxxxxxxxxxx> wrote: >> On 12 Jan 2017, at 10:51, David Laight <David.Laight@xxxxxxxxxx> wrote: >> >> From: Sun Paul [mailto:paulrbk@xxxxxxxxx] >>> Sent: 12 January 2017 09:31 >>> Let me clear the understanding. below is the flow. >>> >>> 1. Client sends to Linux Router: 192.168.206.83 -> 192.168.206.56, >>> 2. Linux router sends to SERVER where the source IP is unchanged: >>> 192.168.206.83 -> 192.168.206.66 >>> >>> My question here is why SERVER cannot response this INIT chunk? >> >> Probably because the IP addresses embedded in the SCTP packet >> don't match the ones in the IP header. > I don't know if it matters on the linux implementation, but it shouldn't. > An SCTP endpoint should consider the source address of the packet containing > the INIT chunk and all the addresses listed in the INIT chunk as valid peer > addresses. > > Could we get a .pcap file of the packet containing the INIT chunk captured > at the server? I would expect an INIT-ACK or and ABORT. If that is not sent, > the checksum was wrong or some kind of packet filtering is active on the > server... > > Best regards > Michael >> >> David >> >> N‹§ēæėrļ›yúčšØbēXŽķĮ§vØ^–)Þš{.nĮ+‰·ĨŠ{ąąËiŠ{ayš ʇڙë,j ĒfĢĒ·hš‹āzđ ŪwĨĒļ Ē·Ķj:+v‰ĻŠwčjØmķŸĸū Ŧ‘ęįzZ+ƒųšŽŠÝĒj" ú! > -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html