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Hi all,

I have a setup in which both client and server are multi-homed each with
three interfaces, A,B and C. Routing is done so that only interface A of
the client can reach interface A of the server, ditto for interfaces B
and C, essentially creating three independent links.

While A is set as the primary address I am using the sendto() function
to transmit from server to client over link B, I am attempting to
measure loss and RTT on link B. Unfortunately if the quality of link B
is poor SCTP is retransmitting packets over link C.

My question is this, is there a way to force SCTP to not retransmit
packets over an alternate link?

Can the RTO for each link be modified so that it will not be reached and
no retransmission over an alternate link will take place?

Would using a different stream for each link prevent retransmissions
over an alternate link?

Thanks in advance!

Kind Regards,
John Fitzpatrick

On Wed, 2007-12-05 at 14:59 +0000,
john.fitzpatrick4 AT mail.dcu.ie
wrote:
> Solved:
>
> I was not specifiying the sstat_assoc_id in addrinfo before calling
> getsockopt.
>
> Thanks all.
>
> >-- Original Message --
> >Date: Wed, 5 Dec 2007 12:29:15 +0000
> >From:
> >john.fitzpatrick4 AT mail.dcu.ie
> >To:
> >discussion AT sctp.de
> >Subject: [SCTP-Discussion] getsockopt() returning invalid argument
> >
> >
> >Hi all,
> >
> >I am writing an application using LK-SCTP and the one-to-many style
> >sockets using SOCK_SEQPACKET. The problem I am having is when I am
> >calling getsockopt() it returns with an error saying invalid argument. I
> >have used the same call with the same parameters while using SOCK_STREAM
> >with no problems. The function call is -
> >getsockopt(sd, IPPROTO_SCTP, SCTP_STATUS, &addrinfo, &lenaddr)
> >
> >Specifically I am going to use the getsockopt function to obtain an srtt
> >value, is this possible while using UPD style one-to-many sockets.
> >
> >I have included sample code for both a Client/Server so that you can
> >recreate the problem to show the problem I am having, any help is
> >greatly appreciated.
> >
> >Kind Regards,
> >John Fitzpatrick
> >
> >//Client Start **************************************************
> >#include <stdio.h>
> >#include <sys/types.h>
> >#include <sys/socket.h>
> >#include <netinet/in.h>
> >#include <arpa/inet.h>
> >#include <stdlib.h>
> >#include <unistd.h>
> >#include <netinet/sctp.h>
> >#include <sys/uio.h>
> >
> >int main(int argc, char **argv)
> >{
> > //Define Variables
> > int sd, port;
> > struct sockaddr_in sin;
> > struct sctp_event_subscribe event;
> >
> > //Check Usage
> > if(argc != 3){
> > printf("\nUsage: <Server> <port>\n");
> > return -1;
> > }
> >
> > //Create Socket
> > sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
> > if(sd < 0){
> > perror("Socket");
> > exit(1);
> > }
> >
> > sin.sin_family = PF_INET;
> > port = atoi(argv[2]);
> > sin.sin_port = htons(port);
> > sin.sin_addr.s_addr = inet_addr(argv[1]);
> >
> > //Set Socket Options
> > /* Enable all events */
> > event.sctp_data_io_event = 1;
> > event.sctp_association_event = 1;
> > event.sctp_address_event = 1;
> > event.sctp_send_failure_event = 1;
> > event.sctp_peer_error_event = 1;
> > event.sctp_shutdown_event = 1;
> > event.sctp_partial_delivery_event = 1;
> > event.sctp_adaption_layer_event = 1;
> >
> > if (setsockopt(sd, IPPROTO_SCTP, SCTP_EVENTS, &event,
> >sizeof(event)) !=
> >0) {
> > perror("setevent failed");
> > exit(1);
> > }
> >
> > //Connect
> > if(connect(sd, (struct sockaddr *) &sin, sizeof(sin)) < 0){
> > perror("Connect");
> > exit(1);
> > }
> >
> > struct sctp_status addrinfo;
> > int lenaddr = sizeof(addrinfo);
> > int send_packet = 1;
> > int sz;
> > while(1){
> > sz = sctp_sendmsg(sd, (int *) &send_packet, sizeof(int),
> >(struct
> >sockaddr *) &sin, sizeof(struct sockaddr_in), 0, 0, 0, 100, 0);
> > send_packet++;
> >
> > if(getsockopt(sd, IPPROTO_SCTP, SCTP_STATUS, &addrinfo,
> >&lenaddr) < 0){
> > perror("getsockopt");
> > }
> > }
> >}
> >//Client End **************************************************
> >
> >//Server Start ************************************************
> >#include <stdio.h>
> >#include <sys/types.h>
> >#include <sys/socket.h>
> >#include <netinet/in.h>
> >#include <arpa/inet.h>
> >#include <stdlib.h>
> >#include <unistd.h>
> >#include <netinet/sctp.h>
> >#include <sys/uio.h>
> >
> >int main(int argc, char **argv)
> >{
> > //Define Variables
> > int sd, bound, port;
> > struct sockaddr_in cli_addr, sin;
> > struct sctp_event_subscribe event;
> >
> > //Check Usage
> > if(argc != 3){
> > printf("\nUsage: <Server> <port>\n");
> > return -1;
> > }
> >
> > //Create Socket
> > sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
> > if(sd < 0){
> > perror("Socket");
> > exit(1);
> > }
> >
> > sin.sin_family = PF_INET;
> > port = atoi(argv[2]);
> > sin.sin_port = htons(port);
> > sin.sin_addr.s_addr = inet_addr(argv[1]);
> >
> > //Bind
> > bound = bind(sd, (struct sockaddr *) &sin, sizeof(sin));
> > printf("Bound = %d\n", bound);
> > if(bound < 0){
> > perror("Bind");
> > exit(1);
> > }
> >
> > //Set Socket Options
> > /* Enable all events */
> > event.sctp_data_io_event = 1;
> > event.sctp_association_event = 1;
> > event.sctp_address_event = 1;
> > event.sctp_send_failure_event = 1;
> > event.sctp_peer_error_event = 1;
> > event.sctp_shutdown_event = 1;
> > event.sctp_partial_delivery_event = 1;
> > event.sctp_adaption_layer_event = 1;
> >
> > if (setsockopt(sd, IPPROTO_SCTP, SCTP_EVENTS, &event,
> >sizeof(event)) !=
> >0) {
> > perror("setevent failed");
> > exit(1);
> > }
> >
> > /* Listen to socket */
> > if(listen(sd, 4) < 0){
> > perror("Listen");
> > }
> >
> > //Receive Message
> > int recv;
> > int recv_packet;
> > int lenaddress = sizeof(struct sockaddr_in);
> > while(1){
> > if(sctp_recvmsg(sd, (int*)&recv_packet,
> >sizeof(recv_packet),
> >&cli_addr, &lenaddress, NULL, 0) < 0)
> > perror("sctp_recvmsg");
> > printf("Recv: %d\n", recv_packet);
> > }
> >}
> >//Server End ************************************************
> >
> >
> >_______________________________________________
> >sctp-discussion mailing list
> >sctp-discussion AT sctp.de
> >http://www.sctp.de/mailman/listinfo/sctp-discussion
>
>
> _______________________________________________
> sctp-discussion mailing list
> sctp-discussion AT sctp.de
> http://www.sctp.de/mailman/listinfo/sctp-discussion

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• [SCTP-Discussion] sendto() Retransmission, John, 01/13/2008
  • Re: [SCTP-Discussion] sendto() Retransmission, Michael Tuexen, 01/16/2008

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