so in this case, says (NODE-A) IP-B send INIT to IP-X (NODE-B), and then IP-Y (NODE-B) returns INIT_ACK to IP-B (NODE-A) this is also treated as a valid, am I correct? On Tue, Dec 3, 2013 at 10:03 AM, Vlad Yasevich <vyasevich@xxxxxxxxx> wrote: > On 12/02/2013 08:39 PM, Sun Paul wrote: >> Another question >> >> if a wrong source IP is used, does the association still classified as normal? > > What do you mean my wrong source IP? As long as the address is part of > the association, it can be used. > > -vlad > >> >> On Tue, Dec 3, 2013 at 9:31 AM, Sun Paul <paulrbk@xxxxxxxxx> wrote: >>> Thanks Vlad >>> >>> I checked on the route, and it looks correct. >>> >>> [root@localhost ~]# ip route get 11.1.1.1 from 110.1.1.1 >>> 11.1.1.1 from 110.1.1.1 via 110.1.1.254 dev eth1 >>> cache mtu 1500 advmss 1460 hoplimit 64 >>> >>> [root@localhost ~]# ip route get 11.1.1.1 from 120.1.1.1 >>> 11.1.1.1 from 120.1.1.1 via 120.1.1.254 dev eth2 >>> cache mtu 1500 advmss 1460 hoplimit 64 >>> >>> [root@localhost ~]# ip route get 12.1.1.1 from 120.1.1.1 >>> 12.1.1.1 from 120.1.1.1 via 120.1.1.254 dev eth2 >>> cache mtu 1500 advmss 1460 hoplimit 64 >>> >>> [root@localhost ~]# ip route get 12.1.1.1 from 110.1.1.1 >>> 12.1.1.1 from 110.1.1.1 via 110.1.1.254 dev eth1 >>> cache mtu 1500 advmss 1460 hoplimit 64 >>> >>> so, if this is not being handled in LKSCTP, is it possible to suggest >>> a way how we can achieve it? >>> >>> On Tue, Dec 3, 2013 at 12:42 AM, Vlad Yasevich <vyasevich@xxxxxxxxx> wrote: >>>> On 12/02/2013 10:45 AM, Karl Heiss wrote: >>>>> On Mon, Dec 2, 2013 at 9:38 AM, Vlad Yasevich <vyasevich@xxxxxxxxx> wrote: >>>>>> On 11/27/2013 11:03 PM, Sun Paul wrote: >>>>>>> How LKSCTP select which source address to use for the INIT_ACK or >>>>>>> HB_ACK? below is the testing result where a router is located in the >>>>>>> middle. >>>>>>> >>>>>>> Before starting the application. the packet on eth1 and eth2 are >>>>>>> >>>>>>> eth1 >>>>>>> 0 packets dropped by kernel >>>>>>> [root@localhost ~]# tcpdump -i eth1 -s 0 -nn >>>>>>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode >>>>>>> listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes >>>>>>> 11:24:14.262489 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [INIT] >>>>>>> [init tag: 28362903] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>>>>> 11:24:14.262522 IP 110.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [ABORT] >>>>>>> 11:24:14.539486 >>>>>>> 11:24:16.262488 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [INIT] >>>>>>> [init tag: 29391734] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>>>>> 11:24:16.262520 IP 110.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [ABORT] >>>>>>> >>>>>>> eth2 >>>>>>> [root@localhost ~]# tcpdump -i eth2 -s 0 -nn >>>>>>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode >>>>>>> listening on eth2, link-type EN10MB (Ethernet), capture size 65535 bytes >>>>>>> >>>>>>> When starting the application. the packet show as below. >>>>>>> >>>>>>> eth1 >>>>>>> 11:26:02.261511 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [INIT] >>>>>>> [init tag: 26256828] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>>>>> 11:26:02.263513 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [COOKIE ECHO] >>>>>>> 11:26:02.264518 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [HB REQ] >>>>>>> 11:26:02.563511 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [HB REQ] >>>>>>> >>>>>>> eth2 >>>>>>> 11:26:02.261604 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [INIT ACK] >>>>>>> [init tag: 3478239387] [rwnd: 131072] [OS: 5] [MIS: 5] [init TSN: >>>>>>> 2330749678] >>>>>>> 11:26:02.263583 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [COOKIE ACK] >>>>>>> 11:26:02.264548 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>> 11:26:02.264652 IP 11.1.1.1.2905 > 120.1.1.1.2905: sctp (1) [HB REQ] >>>>>>> 11:26:02.264705 IP 120.1.1.1.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>> 11:26:02.563543 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>> >>>>>>> From the above result, you can see that the INIT, COOKIE ECHO and >>>>>>> HB_REQ originated from 12.1.1.1 on eth1, but the ACK (INIT_ACK, >>>>>>> COOKIE_ACK, HB_ACK) are returned on eth2 using source address >>>>>>> 120.1.1.1 instead of 110.1.1.1. >>>>>>> >>>>>>> Why LKSCTP use 120.1.1.1 as source instead of 110.1.1.1? >>>>>>> >>>>>>> For simple ICMP ping test, it is normal, but not for SCTP. >>>>>>> >>>>>>> eth1 >>>>>>> 11:30:02.824548 IP 12.1.1.1 > 110.1.1.1: ICMP echo request, id 37178, >>>>>>> seq 12, length 64 >>>>>>> 11:30:02.824559 IP 110.1.1.1 > 12.1.1.1: ICMP echo reply, id 37178, >>>>>>> seq 12, length 64 >>>>>>> 11:30:03.825551 IP 12.1.1.1 > 110.1.1.1: ICMP echo request, id 37178, >>>>>>> seq 13, length 64 >>>>>>> 11:30:03.825561 IP 110.1.1.1 > 12.1.1.1: ICMP echo reply, id 37178, >>>>>>> seq 13, length 64 >>>>>>> >>>>>>> eth2 >>>>>>> 11:30:34.027687 IP 11.1.1.1 > 120.1.1.1: ICMP echo request, id 46138, >>>>>>> seq 2, length 64 >>>>>>> 11:30:34.027697 IP 120.1.1.1 > 11.1.1.1: ICMP echo reply, id 46138, >>>>>>> seq 2, length 64 >>>>>>> 11:30:35.027686 IP 11.1.1.1 > 120.1.1.1: ICMP echo request, id 46138, >>>>>>> seq 3, length 64 >>>>>>> 11:30:35.027694 IP 120.1.1.1 > 11.1.1.1: ICMP echo reply, id 46138, >>>>>>> seq 3, length 64 >>>>>>> >>>>>>> Below is the route information >>>>>>> #route -n >>>>>>> Kernel IP routing table >>>>>>> Destination Gateway Genmask Flags Metric Ref Use Iface >>>>>>> 110.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 >>>>>>> 120.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth2 >>>>>>> >>>>>>> # ip route show >>>>>>> 110.1.1.0/24 dev eth1 proto kernel scope link src 110.1.1.1 >>>>>>> 120.1.1.0/24 dev eth2 proto kernel scope link src 120.1.1.1 >>>>>>> >>>>>>> Since we are using iproute2, so we will have dedicate routing table >>>>>>> per interface >>>>>>> >>>>>>> # ip route show table SCTP1 >>>>>>> default via 110.1.1.254 dev eth1 >>>>>>> >>>>>>> # ip route show table SCTP2 >>>>>>> default via 120.1.1.254 dev eth2 >>>>>>> >>>>>>> # ip rule ls >>>>>>> 0: from all lookup local >>>>>>> 101: from 110.1.1.1 lookup SCTP1 >>>>>>> 102: from 120.1.1.1 lookup SCTP2 >>>>>>> 32766: from all lookup main >>>>>>> 32767: from all lookup default >>>>>>> >>>>>>> How LKSCTP select source address to reply? If we know how it works, >>>>>>> then we may know what is going wrong. >>>>>> >>>>>> LKSCTP will prefer the address returned from the routing table as long >>>>>> as it is one of the addresses that is bound by the socket and are usable >>>>>> by the association. >>>>>> >>>>>> If the address returned from the route lookup is not part of the >>>>>> association, then lksctp attempts to lookup routes using one of the >>>>>> source addresses it has available. Usually the first lookup succeeds >>>>>> due to the host-model implementation in linux. >>>>>> >>>>>> You may want to change your rule set to be destination based. Then >>>>>> in the table associated with the rule, specify the source address >>>>>> you want to be used. >>>>>> >>>>>> -vlad >>>>> >>>>> I have had similar qualms myself about this behavior, and I honestly >>>>> don't know what the correct answer should be... >>>>> >>>>> In my opinion, shouldn't the source address "just work" for >>>>> acknowledgements? If the spec explicitly states that the ACK should >>>>> have a source address that matches the destination of the chunk being >>>>> ACKed, why should someone have to configure this behavior outside of >>>>> the SCTP stack by default? Is it a technical limitation, or is this >>>>> done for a particular reason? I can understand needing to override >>>>> the behavior, but why isn't the default "sane"? >>>> >>>> I think the results are sane, they simply may not match expectations. >>>> SCTP spec doesn't say anything about source address selection. It >>>> says that a response should be send back to the source of the request. >>>> This is being done in both cases, i.e. the destination address in >>>> INIT-ACK matches the source of the INIT. >>>> >>>> The spec does contain the MAY text that allows finer control of source >>>> addresses, but lksctp doesn't seem to implement that. Whenever we've >>>> tried, we couldn't get the generic mechanism working to please everyone, >>>> as everyone had slightly different configurations and expectations. So >>>> we left it to the rules engine. >>>> >>>> In this setup, it just appears that the default routing is not what you >>>> expect. You can easily check this with 'ip route get' command. If it >>>> is not what you want linux allows you to change that via ip rules. >>>> >>>> -vlad >>>> >>>>> >>>>> Karl >>>>> >>>>>>> >>>>>>> On Wed, Nov 27, 2013 at 8:45 PM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote: >>>>>>>> On Wed, Nov 27, 2013 at 07:10:49AM +0800, Sun Paul wrote: >>>>>>>>> Hi Vlad >>>>>>>>> >>>>>>>>> Thank for your reply. If it is based on the destination IP to find the >>>>>>>>> best route, why the problem didn't happen on single-homing sample? >>>>>>>>> >>>>>>>> Because You only ever use one address from NODE A (12.1.1.1) >>>>>>>> >>>>>>>>> In the single-homing sample that provided in the original email, both >>>>>>>>> of the interfaces (eth1 and eth2) are presented on NODE-B during the >>>>>>>>> test. However, the LKSCTP library know to use the interface eth1 to >>>>>>>>> respond to the SCTP request. >>>>>>>>> >>>>>>>> Yes, because it does a route lookup to each of the two ip addresses to NODE B, >>>>>>>> and in both lookups, the route indicates that only one source address should be >>>>>>>> used (12.1.1.1). If you issue a ip route show command, you'll see that routes >>>>>>>> to both address on NODE B match on a rule that specifies the same src address >>>>>>>> and interface be used. >>>>>>>> >>>>>>>> Neil >>>>>>>> >>>>>>>>> - PS >>>>>>>>> >>>>>>>>> On Wed, Nov 27, 2013 at 7:09 AM, Sun Paul <paulrbk@xxxxxxxxx> wrote: >>>>>>>>>> Hi Vlad >>>>>>>>>> >>>>>>>>>> Thank for your reply. If it is based on the destination IP to find the >>>>>>>>>> best route, why the problem didn't happen on single-homing sample? >>>>>>>>>> >>>>>>>>>> In the single-homing sample that provided in the original email, both >>>>>>>>>> of the interfaces (eth1 and eth2) are presented on NODE-B during the >>>>>>>>>> test. However, the LKSCTP library know to use the interface eth1 to >>>>>>>>>> respond to the SCTP request. >>>>>>>>>> >>>>>>>>>> - PS >>>>>>>>>> >>>>>>>>>> On Tue, Nov 26, 2013 at 11:19 PM, Vlad Yasevich <vyasevich@xxxxxxxxx> wrote: >>>>>>>>>>> On 11/25/2013 08:03 PM, Sun Paul wrote: >>>>>>>>>>>> Hi >>>>>>>>>>>> >>>>>>>>>>>> we have a problem on using LKSCTP to form a 4 ways multi-homing network. >>>>>>>>>>>> >>>>>>>>>>>> Configuration >>>>>>>>>>>> - Node-A has 2 IP addresses in different subnets, known as IP-A (eth1), >>>>>>>>>>>> IP-B (eth2) >>>>>>>>>>>> - Node-B has 2 IP addresses in different subnets, known as IP-X (eth1), >>>>>>>>>>>> IP-Y (eth2) >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> First of all, this is not a 4 way multi-homed network. As far as each >>>>>>>>>>> SCTP association is concerned, it has only 2 destinations to send to >>>>>>>>>>> so it has only 2 ways to get there. The fact that you have multiple >>>>>>>>>>> local addresses doesn't mean that every local address can and should >>>>>>>>>>> be used to connect to the remote. >>>>>>>>>>> >>>>>>>>>>>> the four way paths are shown below. >>>>>>>>>>>> 1. IP-A (11.1.1.1) to IP-X (11.1.1.11) >>>>>>>>>>>> 2. IP-B (12.1.1.1) to IP-Y (12.1.1.11) >>>>>>>>>>>> 3. IP-A (11.1.1.1) to IP-Y (12.1.1.11) >>>>>>>>>>>> 4. IP-B (12.1.1.1) to IP-X (11.1.1.11) >>>>>>>>>>> >>>>>>>>>>> No, actually you only have 2 paths: one to IPX and one to IP-Y. >>>>>>>>>>> Which source address you choose is based on routing policy >>>>>>>>>>> decisions and is outside the scope of SCTP. >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> the HB/HB_ACK is normal for the paths " IP-A to IP-X" and "IP-B to >>>>>>>>>>>> IP-Y", but it is not correct for the rest of two. >>>>>>>>>>> >>>>>>>>>>> Right, because linux is using a host addressing model, not an interface >>>>>>>>>>> addressing model. SCTP stack simply finds the best source address >>>>>>>>>>> that can be used to reach IP-X and it happens to be IP-A. So that >>>>>>>>>>> is what it is going to use. >>>>>>>>>>> >>>>>>>>>>> The above explains why you are seeing what you describe below. >>>>>>>>>>> >>>>>>>>>>> In the end, linux SCTP implementation determines paths solely based >>>>>>>>>>> on the destination address. >>>>>>>>>>> >>>>>>>>>>> -vlad >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> First of all, we are using iproute2 to form 2 table such that when >>>>>>>>>>>> IP-B arrives on IP-X, it will know how to route back to IP-B on the >>>>>>>>>>>> same interface, i.e (eth1). Same logic for the path "IP-A to IP-X". >>>>>>>>>>>> >>>>>>>>>>>> What we observed here is that when 12.1.1.1 sends INIT to 11.1.1.11, >>>>>>>>>>>> LKSCTP will send back the INIT_ACK to 12.1.1.1 using 12.1.1.11 but not >>>>>>>>>>>> using the IP 11.1.1.11. >>>>>>>>>>>> >>>>>>>>>>>> The above operation makes the subsequence HB/HB_ACK in using wrong IP address. >>>>>>>>>>>> >>>>>>>>>>>> TCP trace on eth1 >>>>>>>>>>>> 18:02:41.058640 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [INIT] >>>>>>>>>>>> [init tag: 19933036] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>>>>>>>>>> 18:02:41.061634 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [COOKIE ECHO] >>>>>>>>>>>> 18:02:41.062642 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:02:41.062846 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>>>>> 18:02:41.361811 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>>>>> 18:02:41.661791 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>>>>> 18:02:41.961791 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>>>>> >>>>>>>>>>>> TCP trace on eth2 >>>>>>>>>>>> 18:02:41.058755 IP 12.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [INIT ACK] >>>>>>>>>>>> [init tag: 424726157] [rwnd: 131072] [OS: 5] [MIS: 5] [init TSN: >>>>>>>>>>>> 3340756356] >>>>>>>>>>>> 18:02:41.061696 IP 12.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [COOKIE ACK] >>>>>>>>>>>> 18:02:41.062663 IP 12.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>>>>> 18:02:41.062791 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:02:41.361777 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:02:41.661772 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:02:41.961772 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:02:42.161771 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:02:42.461770 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:02:42.675770 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> If we are using single homing, there is no problem on the SCTP >>>>>>>>>>>> communication. Below is the TCP trace on eth1 using sctp_test >>>>>>>>>>>> >>>>>>>>>>>> 18:09:55.356727 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [INIT] >>>>>>>>>>>> [init tag: 32516609] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>>>>>>>>>> 18:09:55.356811 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [INIT ACK] >>>>>>>>>>>> [init tag: 3168861995] [rwnd: 131072] [OS: 10] [MIS: 16] [init TSN: >>>>>>>>>>>> 1877695021] >>>>>>>>>>>> 18:09:55.357727 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [COOKIE ECHO] >>>>>>>>>>>> 18:09:55.357788 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [COOKIE ACK] >>>>>>>>>>>> 18:09:55.358724 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:09:55.358740 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>>>>> 18:09:55.379715 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [DATA] >>>>>>>>>>>> (B)(E) [TSN: 0] [SID: 0] [SSEQ 0] [PPID 0x3] >>>>>>>>>>>> 18:09:55.379735 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [SACK] >>>>>>>>>>>> [cum ack 0] [a_rwnd 131064] [#gap acks 0] [#dup tsns 0] >>>>>>>>>>>> 18:09:55.657716 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>>>>> 18:09:55.657732 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>>>>> >>>>>>>>>>>> From the observations, it seems that the LKSCTP library is not able to >>>>>>>>>>>> use the original local address when multi-homing is being used. Is >>>>>>>>>>>> there anyway can be resolved it? >>>>>>>>>>>> >>>>>>>>>>>> Thanks >>>>>>>>>>>> >>>>>>>>>>>> PS >>>>>>>>>>>> -- >>>>>>>>>>>> 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 >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>> -- >>>>>>>>> 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 >>>>>>>>> >>>>>> >>>>>> -- >>>>>> 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 >>>> > -- 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