Re: [dtn-users] A problem with dtntunnel

[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: