sendrecv.cpp

   1 /*
   2  *  sendrecv.cpp
   3  *  most of the swift's state machine
   4  *
   5  *  Created by Victor Grishchenko on 3/6/09.
   6  *  Copyright 2009 Delft University of Technology. All rights reserved.
   7  *
   8  */
   9 #include "swift.h"
  10 #include "compat/util.h"
  11
  12
  13 using namespace swift;
  14 using namespace std;
  15
  16 /*
  17  TODO  25 Oct 18:55
  18  - range: ALL
  19  - randomized testing of advanced ops (new testcase)
  20  */
  21
  22 void    Channel::AddPeakHashes (Datagram& dgram) {
  23     for(int i=0; i<file().peak_count(); i++) {
  24         bin64_t peak = file().peak(i);
  25         dgram.Push8(SWIFT_HASH);
  26         dgram.Push32((uint32_t)peak);
  27         dgram.PushHash(file().peak_hash(i));
  28         //DLOG(INFO)<<"#"<<id<<" +pHASH"<<file().peak(i);
  29         dprintf("%s #%u +phash %s\n",tintstr(),id_,peak.str());
  30     }
  31 }
  32
  33
  34 void    Channel::AddUncleHashes (Datagram& dgram, bin64_t pos) {
  35     bin64_t peak = file().peak_for(pos);
  36     while (pos!=peak && ((NOW&3)==3 || !data_out_cap_.within(pos.parent())) &&
  37             ack_in_.get(pos.parent())==binmap_t::EMPTY  ) {
  38         bin64_t uncle = pos.sibling();
  39         dgram.Push8(SWIFT_HASH);
  40         dgram.Push32((uint32_t)uncle);
  41         dgram.PushHash( file().hash(uncle) );
  42         //DLOG(INFO)<<"#"<<id<<" +uHASH"<<uncle;
  43         dprintf("%s #%u +hash %s\n",tintstr(),id_,uncle.str());
  44         pos = pos.parent();
  45     }
  46 }
  47
  48
  49 bin64_t        Channel::DequeueHint () {
  50     if (hint_in_.empty() && last_recv_time_>NOW-rtt_avg_-TINT_SEC) {
  51         uint64_t twist = peer_channel_id_;  // got no hints, send something randomly
  52         twist &= file().peak(0); // may make it semi-seq here
  53         file().ack_out().twist(twist);
  54         ack_in_.twist(twist);
  55         bin64_t my_pick =
  56             file().ack_out().find_filtered(ack_in_,bin64_t::ALL,binmap_t::FILLED);
  57         while (my_pick.width()>max(1,(int)cwnd_))
  58             my_pick = my_pick.left();
  59         file().ack_out().twist(0);
  60         ack_in_.twist(0);
  61         if (my_pick!=bin64_t::NONE) {
  62             my_pick = my_pick.twisted(twist);
  63             hint_in_.push_back(my_pick);
  64             dprintf("%s #%u *hint %s\n",tintstr(),id_,my_pick.str());
  65         }
  66     }
  67     bin64_t send = bin64_t::NONE;
  68     while (!hint_in_.empty() && send==bin64_t::NONE) {
  69         bin64_t hint = hint_in_.front().bin;
  70         tint time = hint_in_.front().time;
  71         hint_in_.pop_front();
  72         while (!hint.is_base()) { // FIXME optimize; possible attack
  73             hint_in_.push_front(tintbin(time,hint.right()));
  74             hint = hint.left();
  75         }
  76         //if (time < NOW-TINT_SEC*3/2 )
  77         //    continue;  bad idea
  78         if (ack_in_.get(hint)!=binmap_t::FILLED)
  79             send = hint;
  80     }
  81     uint64_t mass = 0;
  82     for(int i=0; i<hint_in_.size(); i++)
  83         mass += hint_in_[i].bin.width();
  84     dprintf("%s #%u dequeued %s [%lli]\n",tintstr(),id_,send.str(),mass);
  85     return send;
  86 }
  87
  88
  89 void    Channel::AddHandshake (Datagram& dgram) {
  90     if (!peer_channel_id_) { // initiating
  91         dgram.Push8(SWIFT_HASH);
  92         dgram.Push32(bin64_t::ALL32);
  93         dgram.PushHash(file().root_hash());
  94         dprintf("%s #%u +hash ALL %s\n",
  95                 tintstr(),id_,file().root_hash().hex().c_str());
  96     }
  97     dgram.Push8(SWIFT_HANDSHAKE);
  98     int encoded = EncodeID(id_);
  99     dgram.Push32(encoded);
 100     dprintf("%s #%u +hs %x\n",tintstr(),id_,encoded);
 101     ack_out_.clear();
 102     AddAck(dgram);
 103 }
 104
 105
 106 void    Channel::Send () {
 107     Datagram dgram(socket_,peer());
 108     dgram.Push32(peer_channel_id_);
 109     bin64_t data = bin64_t::NONE;
 110     if ( is_established() ) {
 111         // FIXME: seeder check
 112         AddAck(dgram);
 113         if (!file().is_complete())
 114             AddHint(dgram);
 115         AddPex(dgram);
 116         CleanDataOut();
 117         data = AddData(dgram);
 118     } else {
 119         AddHandshake(dgram);
 120         AddAck(dgram);
 121     }
 122     dprintf("%s #%u sent %ib %s:%x\n",
 123             tintstr(),id_,dgram.size(),peer().str(),peer_channel_id_);
 124     if (dgram.size()==4) {// only the channel id; bare keep-alive
 125         data = bin64_t::ALL;
 126         //dprintf("%s #%u considering keepalive %i %f %s\n",
 127         //        tintstr(),id_,(int)data_out_.size(),cwnd_,SEND_CONTROL_MODES[send_control_]);
 128         //if (data_out_.size()<cwnd_ && send_control_!=KEEP_ALIVE_CONTROL) {
 129             //if ( cwnd_ < 1 )
 130             //    SwitchSendControl(KEEP_ALIVE_CONTROL);
 131             //else
 132             //    cwnd_ = cwnd_/2.0;
 133         //}
 134         //if (data_out_.empty() && send_control_!=KEEP_ALIVE_CONTROL)
 135         //     SwitchSendControl(KEEP_ALIVE_CONTROL);// we did our best
 136         //if (NOW<last_send_time_+MAX_SEND_INTERVAL) // no need for keepalive
 137         //    return; // don't send empty dgram
 138     }
 139     if (dgram.Send()==-1)
 140         print_error("can't send datagram");
 141     last_send_time_ = NOW;
 142     sent_since_recv_++;
 143     dgrams_sent_++;
 144 }
 145
 146
 147 void    Channel::AddHint (Datagram& dgram) {
 148
 149     tint plan_for = max(TINT_SEC,rtt_avg_*4);
 150
 151     tint timed_out = NOW - plan_for*2;
 152     while ( !hint_out_.empty() && hint_out_.front().time < timed_out ) {
 153         hint_out_size_ -= hint_out_.front().bin.width();
 154         hint_out_.pop_front();
 155     }
 156
 157     /*int peer_cwnd = (int)(rtt_avg_ / dip_avg_);
 158     if (!peer_cwnd)
 159         peer_cwnd = 1;*/
 160     int plan_pck = std::max ( (tint)1, plan_for / dip_avg_ );
 161
 162     if ( hint_out_size_ < plan_pck ) {
 163
 164         int diff = plan_pck - hint_out_size_; // TODO: aggregate
 165         bin64_t hint = transfer().picker().Pick(ack_in_,diff,NOW+plan_for*2);
 166
 167         if (hint!=bin64_t::NONE) {
 168             dgram.Push8(SWIFT_HINT);
 169             dgram.Push32(hint);
 170             dprintf("%s #%u +hint %s [%lli]\n",tintstr(),id_,hint.str(),hint_out_size_);
 171             hint_out_.push_back(hint);
 172             hint_out_size_ += hint.width();
 173         } else
 174             dprintf("%s #%u Xhint\n",tintstr(),id_);
 175
 176     }
 177 }
 178
 179
 180 bin64_t        Channel::AddData (Datagram& dgram) {
 181
 182     if (!file().size()) // know nothing
 183         return bin64_t::NONE;
 184
 185     bin64_t tosend = bin64_t::NONE;
 186     tint luft = send_interval_>>4; // may wake up a bit earlier
 187     if (data_out_.size()<cwnd_ &&
 188             last_data_out_time_+send_interval_<=NOW+luft) {
 189         tosend = DequeueHint();
 190         if (tosend==bin64_t::NONE) {
 191             dprintf("%s #%u sendctrl no idea what to send\n",tintstr(),id_);
 192             if (send_control_!=KEEP_ALIVE_CONTROL)
 193                 SwitchSendControl(KEEP_ALIVE_CONTROL);
 194         }
 195     } else
 196         dprintf("%s #%u sendctrl wait cwnd %f data_out %i next %s\n",
 197                 tintstr(),id_,cwnd_,data_out_.size(),tintstr(last_data_out_time_+NOW-send_interval_));
 198
 199     if (tosend==bin64_t::NONE)// && (last_data_out_time_>NOW-TINT_SEC || data_out_.empty()))
 200         return bin64_t::NONE; // once in a while, empty data is sent just to check rtt FIXED
 201
 202     if (ack_in_.is_empty() && file().size())
 203         AddPeakHashes(dgram);
 204     AddUncleHashes(dgram,tosend);
 205     if (!ack_in_.is_empty()) // TODO: cwnd_>1
 206         data_out_cap_ = tosend;
 207
 208     if (dgram.size()>254) {
 209         dgram.Send(); // kind of fragmentation
 210         dgram.Push32(peer_channel_id_);
 211     }
 212
 213     dgram.Push8(SWIFT_DATA);
 214     dgram.Push32(tosend.to32());
 215
 216     uint8_t buf[1024];
 217     size_t r = pread(file().file_descriptor(),buf,1024,tosend.base_offset()<<10);
 218     // TODO: corrupted data, retries, caching
 219     if (r<0) {
 220         print_error("error on reading");
 221         return bin64_t::NONE;
 222     }
 223     assert(dgram.space()>=r+4+1);
 224     dgram.Push(buf,r);
 225
 226     last_data_out_time_ = NOW;
 227     data_out_.push_back(tosend);
 228     dprintf("%s #%u +data %s\n",tintstr(),id_,tosend.str());
 229
 230     return tosend;
 231 }
 232
 233
 234 void    Channel::AddTs (Datagram& dgram) {
 235     dgram.Push8(SWIFT_TS);
 236     dgram.Push64(data_in_.time);
 237     dprintf("%s #%u +ts %s\n",tintstr(),id_,tintstr(data_in_.time));
 238 }
 239
 240
 241 void    Channel::AddAck (Datagram& dgram) {
 242     if (data_in_dbl_!=bin64_t::NONE) { // TODO: do redundancy better
 243         dgram.Push8(SWIFT_ACK);
 244         dgram.Push32(data_in_dbl_.to32());
 245         data_in_dbl_=bin64_t::NONE;
 246     }
 247     if (data_in_.time!=TINT_NEVER) { // TODO: ACK NONE for corrupted data
 248         AddTs(dgram);
 249         bin64_t pos = data_in_.bin; // be precise file().ack_out().cover(data_in_.bin);
 250         dgram.Push8(SWIFT_ACK);
 251         dgram.Push32(pos.to32());
 252         //dgram.Push64(data_in_.time);
 253         ack_out_.set(pos);
 254         dprintf("%s #%u +ack %s %s\n",tintstr(),id_,pos.str(),tintstr(data_in_.time));
 255         data_in_ = tintbin(TINT_NEVER,bin64_t::NONE);
 256         if (pos.layer()>2)
 257             data_in_dbl_ = pos;
 258     }
 259     for(int count=0; count<4; count++) {
 260         bin64_t ack = file().ack_out().find_filtered(ack_out_, bin64_t::ALL, binmap_t::FILLED);
 261         if (ack==bin64_t::NONE)
 262             break;
 263         ack = file().ack_out().cover(ack);
 264         ack_out_.set(ack);
 265         dgram.Push8(SWIFT_ACK);
 266         dgram.Push32(ack.to32());
 267         dprintf("%s #%u +ack %s\n",tintstr(),id_,ack.str());
 268     }
 269 }
 270
 271
 272 void    Channel::Recv (Datagram& dgram) {
 273     dprintf("%s #%u recvd %i\n",tintstr(),id_,dgram.size()+4);
 274     peer_send_time_ = 0; // has scope of 1 datagram
 275     dgrams_rcvd_++;
 276     if (last_send_time_ && rtt_avg_==TINT_SEC && dev_avg_==0) {
 277         rtt_avg_ = NOW - last_send_time_;
 278         dev_avg_ = rtt_avg_;
 279         dip_avg_ = rtt_avg_;
 280         dprintf("%s #%u sendctrl rtt init %lli\n",tintstr(),id_,rtt_avg_);
 281     }
 282     bin64_t data = dgram.size() ? bin64_t::NONE : bin64_t::ALL;
 283     while (dgram.size()) {
 284         uint8_t type = dgram.Pull8();
 285         switch (type) {
 286             case SWIFT_HANDSHAKE: OnHandshake(dgram); break;
 287             case SWIFT_DATA:      data=OnData(dgram); break;
 288             case SWIFT_TS:        OnTs(dgram); break;
 289             case SWIFT_ACK:       OnAck(dgram); break;
 290             case SWIFT_HASH:      OnHash(dgram); break;
 291             case SWIFT_HINT:      OnHint(dgram); break;
 292             case SWIFT_PEX_ADD:   OnPex(dgram); break;
 293             default:
 294                 eprintf("%s #%u ?msg id unknown %i\n",tintstr(),id_,(int)type);
 295                 return;
 296         }
 297     }
 298     last_recv_time_ = NOW;
 299     sent_since_recv_ = 0;
 300 }
 301
 302
 303 void    Channel::OnHash (Datagram& dgram) {
 304     bin64_t pos = dgram.Pull32();
 305     Sha1Hash hash = dgram.PullHash();
 306     file().OfferHash(pos,hash);
 307     //DLOG(INFO)<<"#"<<id<<" .HASH"<<(int)pos;
 308     dprintf("%s #%u -hash %s\n",tintstr(),id_,pos.str());
 309 }
 310
 311
 312 void    Channel::CleanHintOut (bin64_t pos) {
 313     int hi = 0;
 314     while (hi<hint_out_.size() && !pos.within(hint_out_[hi].bin))
 315         hi++;
 316     if (hi==hint_out_.size())
 317         return; // something not hinted or hinted in far past
 318     while (hi--) { // removing likely snubbed hints
 319         hint_out_size_ -= hint_out_.front().bin.width();
 320         hint_out_.pop_front();
 321     }
 322     while (hint_out_.front().bin!=pos) {
 323         tintbin f = hint_out_.front();
 324         f.bin = f.bin.towards(pos);
 325         hint_out_.front().bin = f.bin.sibling();
 326         hint_out_.push_front(f);
 327     }
 328     hint_out_.pop_front();
 329     hint_out_size_--;
 330 }
 331
 332
 333 bin64_t Channel::OnData (Datagram& dgram) {
 334     bin64_t pos = dgram.Pull32();
 335     uint8_t *data;
 336     int length = dgram.Pull(&data,1024);
 337     bool ok = (pos==bin64_t::NONE) || file().OfferData(pos, (char*)data, length) ;
 338     dprintf("%s #%u %cdata %s\n",tintstr(),id_,ok?'-':'!',pos.str());
 339     data_in_ = tintbin(NOW,bin64_t::NONE);
 340     if (!ok)
 341         return bin64_t::NONE;
 342     data_in_.bin = pos;
 343     if (pos!=bin64_t::NONE) {
 344         if (last_data_in_time_) {
 345             tint dip = NOW - last_data_in_time_;
 346             dip_avg_ = ( dip_avg_*3 + dip ) >> 2;
 347         }
 348         last_data_in_time_ = NOW;
 349     }
 350     CleanHintOut(pos);
 351     return pos;
 352 }
 353
 354
 355 void    Channel::CleanDataOut (bin64_t ackd_pos) { // TODO: isn't it too long?
 356
 357     int max_ack_off = 0;
 358
 359     if (ackd_pos!=bin64_t::NONE) {
 360         for (int i=0; i<data_out_.size(); i++) {
 361             if (data_out_[i]!=tintbin() && data_out_[i].bin.within(ackd_pos)) {
 362                 if (peer_send_time_)
 363                     for(tbqueue::iterator j=data_out_tmo_.begin(); j!=data_out_tmo_.end(); j++)
 364                         if (j->bin==data_out_[i].bin)
 365                             peer_send_time_=0; // possibly retransmit
 366                 if (peer_send_time_) { // well, it is sorta ACK ACK
 367                     tint rtt = NOW-data_out_[i].time;
 368                     rtt_avg_ = (rtt_avg_*7 + rtt) >> 3;
 369                     dev_avg_ = ( dev_avg_*3 + abs(rtt-rtt_avg_) ) >> 2;
 370                     assert(data_out_[i].time!=TINT_NEVER);
 371                     tint owd = peer_send_time_ - data_out_[i].time;
 372                     owd_cur_bin_ = (owd_cur_bin_+1) & 3;
 373                     owd_current_[owd_cur_bin_] = owd;
 374                     if ( owd_min_bin_start_+TINT_SEC*30 < NOW ) {
 375                         owd_min_bin_start_ = NOW;
 376                         owd_min_bin_ = (owd_min_bin_+1) & 3;
 377                         owd_min_bins_[owd_min_bin_] = TINT_NEVER;
 378                     }
 379                     if (owd_min_bins_[owd_min_bin_]>owd)
 380                         owd_min_bins_[owd_min_bin_] = owd;
 381                     peer_send_time_ = 0;
 382                 }
 383                 dprintf("%s #%u sendctrl rtt %lli dev %lli based on %s\n",
 384                         tintstr(),id_,rtt_avg_,dev_avg_,data_out_[i].bin.str());
 385                 bin64_t pos = data_out_[i].bin;
 386                 ack_rcvd_recent_++;
 387                 data_out_[i]=tintbin();
 388                 max_ack_off = i;
 389                 if (ackd_pos==pos)
 390                     break;
 391             }
 392         }
 393         while (!data_out_.empty() && data_out_.front().bin==bin64_t::NONE) {
 394             data_out_.pop_front();
 395             max_ack_off--;
 396         }
 397         static const int MAX_REORDERING = 2;  // the triple-ACK principle
 398         if (max_ack_off>MAX_REORDERING) {
 399             while (max_ack_off && (data_out_.front().bin==bin64_t::NONE
 400                                    || ack_in_.is_filled(data_out_.front().bin)) ) {
 401                 data_out_.pop_front();
 402                 max_ack_off--;
 403             }
 404             while (max_ack_off>MAX_REORDERING) {
 405                 ack_not_rcvd_recent_++;
 406                 data_out_tmo_.push_back(data_out_.front().bin);
 407                 dprintf("%s #%u Rdata %s\n",tintstr(),id_,data_out_.front().bin.str());
 408                 data_out_.pop_front();
 409                 max_ack_off--;
 410                 data_out_cap_ = bin64_t::ALL;
 411             }
 412         }
 413         peer_send_time_ = 0;
 414     }
 415     tint timeout = NOW - rtt_avg_ - 4*std::max(dev_avg_,TINT_MSEC*50);
 416     while (!data_out_.empty() && data_out_.front().time<timeout) {
 417         if (data_out_.front().bin!=bin64_t::NONE && ack_in_.is_empty(data_out_.front().bin)) {
 418             ack_not_rcvd_recent_++;
 419             data_out_cap_ = bin64_t::ALL;
 420             data_out_tmo_.push_back(data_out_.front().bin);
 421             dprintf("%s #%u Tdata %s\n",tintstr(),id_,data_out_.front().bin.str());
 422         }
 423         data_out_.pop_front();
 424     }
 425     while (!data_out_.empty() && data_out_.front().bin==bin64_t::NONE)
 426         data_out_.pop_front();
 427     assert(data_out_.empty() || data_out_.front().time!=TINT_NEVER);
 428     while (!data_out_tmo_.empty() && data_out_tmo_.front().time<NOW-MAX_POSSIBLE_RTT)
 429         data_out_tmo_.pop_front();
 430
 431 }
 432
 433
 434 void    Channel::OnAck (Datagram& dgram) {
 435     bin64_t ackd_pos = dgram.Pull32();
 436     if (ackd_pos==bin64_t::NONE)
 437         return; // likely, brocken packet / insufficient hashes
 438     if (file().size() && ackd_pos.base_offset()>=file().packet_size()) {
 439         eprintf("invalid ack: %s\n",ackd_pos.str());
 440         return;
 441     }
 442     dprintf("%s #%u -ack %s\n",tintstr(),id_,ackd_pos.str());
 443     ack_in_.set(ackd_pos);
 444     CleanDataOut(ackd_pos); // FIXME do AFTER all ACKs
 445 }
 446
 447
 448 void Channel::OnTs (Datagram& dgram) {
 449     peer_send_time_ = dgram.Pull64();
 450     dprintf("%s #%u -ts %lli\n",tintstr(),id_,peer_send_time_);
 451 }
 452
 453
 454 void    Channel::OnHint (Datagram& dgram) {
 455     bin64_t hint = dgram.Pull32();
 456     hint_in_.push_back(hint);
 457     //ack_in_.set(hint,binmap_t::EMPTY);
 458     //RequeueSend(cc_->OnHintRecvd(hint));
 459     dprintf("%s #%u -hint %s\n",tintstr(),id_,hint.str());
 460 }
 461
 462
 463 void Channel::OnHandshake (Datagram& dgram) {
 464     peer_channel_id_ = dgram.Pull32();
 465     dprintf("%s #%u -hs %x\n",tintstr(),id_,peer_channel_id_);
 466     // self-connection check
 467     if (!SELF_CONN_OK) {
 468         uint32_t try_id = DecodeID(peer_channel_id_);
 469         if (channel(try_id) && !channel(try_id)->peer_channel_id_) {
 470             peer_channel_id_ = 0;
 471             Close();
 472             return; // this is a self-connection
 473         }
 474     }
 475     // FUTURE: channel forking
 476 }
 477
 478
 479 void Channel::OnPex (Datagram& dgram) {
 480     uint32_t ipv4 = dgram.Pull32();
 481     uint16_t port = dgram.Pull16();
 482     Address addr(ipv4,port);
 483     dprintf("%s #%u -pex %s\n",tintstr(),id_,addr.str());
 484     transfer().OnPexIn(addr);
 485 }
 486
 487
 488 void    Channel::AddPex (Datagram& dgram) {
 489     int chid = transfer().RevealChannel(pex_out_);
 490     if (chid==-1 || chid==id_)
 491         return;
 492     Address a = channels[chid]->peer();
 493     dgram.Push8(SWIFT_PEX_ADD);
 494     dgram.Push32(a.ipv4());
 495     dgram.Push16(a.port());
 496     dprintf("%s #%u +pex %s\n",tintstr(),id_,a.str());
 497 }
 498
 499
 500 Channel*    Channel::RecvDatagram (int socket) {
 501     Datagram data(socket);
 502     data.Recv();
 503     const Address& addr = data.address();
 504 #define return_log(...) { printf(__VA_ARGS__); return NULL; }
 505     if (data.size()<4)
 506         return_log("datagram shorter than 4 bytes %s\n",addr.str());
 507     uint32_t mych = data.Pull32();
 508     Sha1Hash hash;
 509     Channel* channel = NULL;
 510     if (!mych) { // handshake initiated
 511         if (data.size()<1+4+1+4+Sha1Hash::SIZE)
 512             return_log ("%s #0 incorrect size %i initial handshake packet %s\n",
 513                         tintstr(),data.size(),addr.str());
 514         uint8_t hashid = data.Pull8();
 515         if (hashid!=SWIFT_HASH)
 516             return_log ("%s #0 no hash in the initial handshake %s\n",
 517                         tintstr(),addr.str());
 518         bin64_t pos = data.Pull32();
 519         if (pos!=bin64_t::ALL)
 520             return_log ("%s #0 that is not the root hash %s\n",tintstr(),addr.str());
 521         hash = data.PullHash();
 522         FileTransfer* file = FileTransfer::Find(hash);
 523         if (!file)
 524             return_log ("%s #0 hash %s unknown, no such file %s\n",tintstr(),hash.hex().c_str(),addr.str());
 525         dprintf("%s #0 -hash ALL %s\n",tintstr(),hash.hex().c_str());
 526         for(binqueue::iterator i=file->hs_in_.begin(); i!=file->hs_in_.end(); i++)
 527             if (channels[*i] && channels[*i]->peer_==data.address() &&
 528                 channels[*i]->last_recv_time_>NOW-TINT_SEC*2)
 529                 return_log("%s #0 have a channel already to %s\n",tintstr(),addr.str());
 530         channel = new Channel(file, socket, data.address());
 531     } else {
 532         mych = DecodeID(mych);
 533         if (mych>=channels.size())
 534             return_log("%s invalid channel #%u, %s\n",tintstr(),mych,addr.str());
 535         channel = channels[mych];
 536         if (!channel)
 537             return_log ("%s #%u is already closed\n",tintstr(),mych,addr.str());
 538         if (channel->peer() != addr)
 539             return_log ("%s #%u invalid peer address %s!=%s\n",
 540                         tintstr(),mych,channel->peer().str(),addr.str());
 541         channel->own_id_mentioned_ = true;
 542     }
 543     //dprintf("recvd %i bytes for %i\n",data.size(),channel->id);
 544     channel->Recv(data);
 545     return channel;
 546 }
 547
 548
 549 void    Channel::Loop (tint howlong) {
 550
 551     tint limit = Datagram::Time() + howlong;
 552
 553     do {
 554
 555         tint send_time(TINT_NEVER);
 556         Channel* sender(NULL);
 557         while (!sender && !send_queue.is_empty()) { // dequeue
 558             tintbin next = send_queue.pop();
 559             sender = channel((int)next.bin);
 560             send_time = next.time;
 561             if (sender && sender->next_send_time_!=send_time &&
 562                      sender->next_send_time_!=TINT_NEVER )
 563                 sender = NULL; // it was a stale entry
 564         }
 565
 566         if ( sender!=NULL && send_time<=NOW ) { // it's time
 567
 568             dprintf("%s #%u sch_send %s\n",tintstr(),sender->id(),
 569                     tintstr(send_time));
 570             sender->Send();
 571             sender->Reschedule();
 572
 573         } else {  // it's too early, wait
 574
 575             tint towait = min(limit,send_time) - NOW;
 576             dprintf("%s #0 waiting %lliusec\n",tintstr(),towait);
 577             int rd = Datagram::Wait(socket_count,sockets,towait);
 578             if (rd!=INVALID_SOCKET) { // in meantime, received something
 579                 Channel* receiver = RecvDatagram(rd);
 580                 if (receiver) // receiver's state may have changed
 581                     receiver->Reschedule();
 582             }
 583             if (sender)  // get back to that later
 584                 send_queue.push(tintbin(send_time,sender->id()));
 585
 586         }
 587
 588     } while (NOW<limit);
 589
 590 }
 591
 592
 593 void Channel::Close () {
 594     this->SwitchSendControl(CLOSE_CONTROL);
 595 }
 596
 597
 598 void Channel::Reschedule () {
 599     next_send_time_ = NextSendTime();
 600     if (next_send_time_!=TINT_NEVER) {
 601         assert(next_send_time_<NOW+TINT_MIN);
 602         send_queue.push(tintbin(next_send_time_,id_));
 603         dprintf("%s #%u requeue for %s\n",tintstr(),id_,tintstr(next_send_time_));
 604     } else {
 605         dprintf("%s #%u closed\n",tintstr(),id_);
 606         delete this;
 607     }
 608 }