Re: [Lksctp-developers] problem with sctp multihoming

[Vlad Y. <vla...@hp...>]

On 08/19/2010 02:42 AM, Prasanth Pillai wrote:
> Hi all,
> 
> I am planning to use multihoming feature in my sctp server. Both my server
> and client
> machines are configured with multiple ip addresses on different interfaces.
> I am able to
> see multiple ip addresses getting passed in init ack through tcpdump. The
> data flows
> fine through one of the interaces, untill the interface goes down (I removed
> the network
> cable manually).  When the interface goes down, the server is not able to
> receive the
> data through the other interface. I am able to see the data coming to the
> other interface
> ip in tcpdump, as soon as the interface is down. But my server is not able
> to receive it.
> 

When you capturing with tcpdump, pay attention to the TSN and SSN numbers
in the DATA you receive.  My guess is that when you unplug the interface,
you might receive some TSNs out of order.

Also, do you see SACKs leaving the server on the 'up' interface?

It should work correctly even though RHEL5 is running a rather old kernel.

-vlad

> server code (system calls only)
> 
> *socket (AF_INET, SOCK_STREAM, IPPROTO_SCTP)*
> *  *
> *bind(listen_sctp_fd, (struct sockaddr *) &sctpser, sizeof (sctpser)))  //
> server first interface ip*
> *  *
> *sctp_bindx(listen_sctp_fd, (struct sockaddr *) addresses, count,
> SCTP_BINDX_ADD_ADDR)) // second interface ip*
> *  *
> *listen(listen_sctp_fd, 5)*
> *  *
> *id = accept(listen_sctp_fd, (struct sockaddr *) &peer_info,  (socklen_t *)
> & peer_info_len))*
> *  *
> *sctp_recvmsg( client_fd, (void *) buffer, sizeof (buffer), (struct sockaddr
> *) NULL, 0, &srInfo, &flags))*
> 
> 
> client code (system calls only)
> 
> 
> *socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP);*
> *  *
> *sctp_connectx(sock_fd, (struct sockaddr *) addresses, 2);*
> *  *
> *sctp_sendmsg(sock_fd, (void *) buffer, strlen(buffer) + 1, NULL, 0, 0, 0,
> 0, 0, 0);*
> 
> 
> I am using Redhat Linux and it uses SCTP implementation of Linux Kernel
> 2.6.18-92 el5.
> Can someone help me, why my code is not working? Is there anything missing
> in my code?
> 
> 
> Waiting for your valuable comments.
> Prasanth
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