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Alternate order of packet emission in unite().

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This commit is contained in:
Adam Ierymenko 2014-01-29 12:11:01 -08:00
parent 4e85213473
commit 372566295e
1 changed files with 43 additions and 27 deletions
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70
node/Switch.cpp
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@ -263,35 +263,51 @@ bool Switch::unite(const Address &p1,const Address &p2,bool force)
TRACE("unite: %s(%s) <> %s(%s)",p1.toString().c_str(),cg.second.toString().c_str(),p2.toString().c_str(),cg.first.toString().c_str());
{ // tell p1 where to find p2
Packet outp(p1,_r->identity.address(),Packet::VERB_RENDEZVOUS);
outp.append((unsigned char)0);
p2.appendTo(outp);
outp.append((uint16_t)cg.first.port());
if (cg.first.isV6()) {
outp.append((unsigned char)16);
outp.append(cg.first.rawIpData(),16);
/* Tell P1 where to find P2 and vice versa, sending the packets to P1 and
* P2 in randomized order in terms of which gets sent first. This is done
* since in a few cases NAT-t can be sensitive to slight timing differences
* in terms of when the two peers initiate. Normally this is accounted for
* by the nearly-simultaneous RENDEZVOUS kickoff from the supernode, but
* given that supernodes are hosted on cloud providers this can in some
* cases have a few ms of latency between packet departures. By randomizing
* the order we make each attempted NAT-t favor one or the other going
* first, meaning if it doesn't succeed the first time it might the second
* and so forth. */
unsigned int alt = _r->prng->next32() & 1;
unsigned int completed = alt + 2;
while (alt != completed) {
if ((alt & 1) == 0) {
// Tell p1 where to find p2.
Packet outp(p1,_r->identity.address(),Packet::VERB_RENDEZVOUS);
outp.append((unsigned char)0);
p2.appendTo(outp);
outp.append((uint16_t)cg.first.port());
if (cg.first.isV6()) {
outp.append((unsigned char)16);
outp.append(cg.first.rawIpData(),16);
} else {
outp.append((unsigned char)4);
outp.append(cg.first.rawIpData(),4);
}
outp.armor(p1p->key(),true);
p1p->send(_r,outp.data(),outp.size(),now);
} else {
outp.append((unsigned char)4);
outp.append(cg.first.rawIpData(),4);
// Tell p2 where to find p1.
Packet outp(p2,_r->identity.address(),Packet::VERB_RENDEZVOUS);
outp.append((unsigned char)0);
p1.appendTo(outp);
outp.append((uint16_t)cg.second.port());
if (cg.second.isV6()) {
outp.append((unsigned char)16);
outp.append(cg.second.rawIpData(),16);
} else {
outp.append((unsigned char)4);
outp.append(cg.second.rawIpData(),4);
}
outp.armor(p2p->key(),true);
p2p->send(_r,outp.data(),outp.size(),now);
}
outp.armor(p1p->key(),true);
p1p->send(_r,outp.data(),outp.size(),now);
}
{ // tell p2 where to find p1
Packet outp(p2,_r->identity.address(),Packet::VERB_RENDEZVOUS);
outp.append((unsigned char)0);
p1.appendTo(outp);
outp.append((uint16_t)cg.second.port());
if (cg.second.isV6()) {
outp.append((unsigned char)16);
outp.append(cg.second.rawIpData(),16);
} else {
outp.append((unsigned char)4);
outp.append(cg.second.rawIpData(),4);
}
outp.armor(p2p->key(),true);
p2p->send(_r,outp.data(),outp.size(),now);
++alt; // counts up and also flips LSB
}
return true;