Another question if a wrong source IP is used, does the association still classified as normal? 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
