Re: [dtn-users] A problem with dtntunnel

["[e-mail]" <[e-mail]>]

Hi David,

Thanks for your patch, it works! :) Connection is cleanly terminated now.

However, there still seems to be a problem. I run dtntunnel over a link
with high latency and about 30% packet loss. The receiving nc sometimes
gets FIN packet before it receives all the data. If I understand it right,
on a lossy link bundles may come out of order. In this case the EOF bundle
may come too early. I think that the reordering procedure in dtntunnel
should be reviewed. Just for information, pure TCP performs better that DTN
over this link.

2012/12/14 David Zoller <[e-mail]>

> Hi Sergey,
> I can't stay away from a problem that is nagging at me so I made some time
> this morning. Going back to the original TCPTunnel.cc code, when a bundle
> is received that has the EOF indication, an empty bundle with the same EOF
> flag set needs to be returned to close the loop (the second FIN). There may
> still be some loose ends or clean up needed but try the code below at the
> end of the while loop.
>
> I did not do a packet capture but I saw that if the receiving nc is not
> running when you start the sender nc then the receiving dtntunnel logs an
> error on the failed connect and returns an EOF bundle which closes the
> sender nc. The EOF bundle could possibly be enhanced to include an error
> message.
>
> I agree that some applications could benefit from a "pretend to be a
> receiver" option with the default working as a bidirectional end-to-end TCP
> connection.
>
> Thanks for dragging me along kicking and screaming on this lesson in DTN
> and TCP tunneling. I've only been using dtntunnel as a one way UDP
> transmitter. I see a good fit for the TCP tunnel in an upcoming project and
> I'll try to make the pitch to use it. This is a pretty cool little app.
> Best regards,
> DZ
>
>
>
>
>
> 484             delete b_recv;
> 485
> 486             if (recv_hdr->eof_) {
> 487                 log_info("bundle had eof bit set... closing
> connection");
> 488
> 489                 if ( !sock_eof ) {
> 490                     sock_eof = true;
> 491                     // send an empty bundle back since we did not
> initiate the close
> 492                     dtn::APIBundle* b = new dtn::APIBundle();
> 493                     hdr.eof_ = 1;
> 494                     hdr.seqno_ = ntohl(send_seqno++);
> 495                     memcpy(b->payload_.buf(sizeof(hdr)), &hdr,
> sizeof(hdr));
> 496                     b->payload_.set_len(sizeof(hdr));
> 497                     int err;
> 498                     if ((err = tunnel->send_bundle(b, &dest_eid_)) !=
> DTN_SUCCESS) {
> 499                         log_err("error sending final socket closed
> packet bundle: %s",
> 500                                 dtn_strerror(err));
> 501                         tcptun_->kill_connection(this);
> 502                         exit(1);
> 503                     }
> 504                     delete b;
> 505                 }
> 506                 sock_.close();
> 507                 goto done;
> 508             }
> 509         }
> 510     }
> 511
> 512  done:
>
>


-- 
Best regards,
Sergey Sireskin