蔡军生先生第二人生的源码分析(三十三)消息解包的实现

港控/mmm° 2022-08-27 01:23 100阅读 0赞

下面的代码是实现数据包的有效性检验，先调用函数validateMessage来检验接收数据缓冲区里是否有效的数据包，然后调用getMessageName函数来查看是否属于这个环路的数据包，最后判断数据包是否值得信任的或者是否禁止接收的数据。

\#159                     // UseCircuitCode can be a valid, off-circuit packet.

\#160                     // But we don't want to acknowledge UseCircuitCode until the circuit is

\#161                     // available, which is why the acknowledgement test is done above. JC

\#162

下面检验数据包是否有效。

\#163                     valid\_packet = mTemplateMessageReader->validateMessage(

\#164                            buffer,

\#165                            receive\_size,

\#166                            host);

\#167

\#168                     // UseCircuitCode is allowed in even from an invalid circuit, so that

判断这个数据包是否属于这个环路。

\#169                     // we can toss circuits around.

\#170                     if(

\#171                            valid\_packet &&

\#172                            !cdp &&

\#173                            (mTemplateMessageReader->getMessageName() !=

\#174                             \_PREHASH\_UseCircuitCode))

\#175                     \{

\#176                            logMsgFromInvalidCircuit( host, recv\_reliable );

\#177                            clearReceiveState();

\#178                            valid\_packet = FALSE;

\#179                     \}

\#180

判断数据包是否值得信任。

\#181                     if(

\#182                            valid\_packet &&

\#183                            cdp &&

\#184                            !cdp->getTrusted() &&

\#185                            mTemplateMessageReader->isTrusted())

\#186                     \{

\#187                            logTrustedMsgFromUntrustedCircuit( host );

\#188                            clearReceiveState();

\#189

\#190                            sendDenyTrustedCircuit(host);

\#191                            valid\_packet = FALSE;

\#192                     \}

\#193

判断数据包是否属于禁止接收的。

\#194                     if (

\#195                            valid\_packet &&

\#196                            mTemplateMessageReader->isBanned(cdp && cdp->getTrusted()))

\#197                     \{

\#198                            llwarns << "LLMessageSystem::checkMessages "

\#199                                   << "received banned message "

\#200                                   << mTemplateMessageReader->getMessageName()

\#201                                   << " from "

\#202                                   << ((cdp && cdp->getTrusted()) ? "trusted " : "untrusted ")

\#203                                   << host << llendl;

\#204                            clearReceiveState();

\#205                            valid\_packet = FALSE;

\#206                     \}

\#207

这个数据包是有效的，下面就开始读取数据包里面的内容，也就是通过消息模板来解释数据，获取所有的信息。

\#208                     if( valid\_packet )

\#209                     \{

\#210                            logValidMsg(cdp, host, recv\_reliable, recv\_resent, (BOOL)(acks>0) );

\#211

\#212                            valid\_packet = mTemplateMessageReader->readMessage(buffer, host);

\#213                     \}

\#214

\#215                     // It's possible that the circuit went away, because ANY message can disable the circuit

\#216                     // (for example, UseCircuit, CloseCircuit, DisableSimulator). Find it again.

\#217                     cdp = mCircuitInfo.findCircuit(host);

\#218

\#219                     if (valid\_packet)

\#220                     \{

\#221                            // enable this for output of message names

\#222                            //llinfos << "< /"" << mTemplateMessageReader->getMessageName()

\#223                                          //<< "/"" << llendl;

\#224

\#328

\#329                            mPacketsIn++;

\#330                            mBytesIn += mTrueReceiveSize;

\#331

\#332                            // ACK here for     valid packets that we've seen

\#333                            // for the first time.

下面通过判断这个数据包是否需要可靠性控制，如果需要就加到回应控制里面。

\#334                            if (cdp && recv\_reliable)

\#335                            \{

\#336                                   // Add to the recently received list for duplicate suppression

\#337                                   cdp->mRecentlyReceivedReliablePackets\[mCurrentRecvPacketID\] = getMessageTimeUsecs();

\#338

\#339                                   // Put it onto the list of packets to be acked

\#340                                   cdp->collectRAck(mCurrentRecvPacketID);

\#341                                   mReliablePacketsIn++;

\#342                            \}

\#343                     \}

\#344                     else

\#345                     \{

\#346                            if (mbProtected && (!cdp))

\#347                            \{

\#348                                   llwarns << "Invalid Packet from invalid circuit " << host << llendl;

\#349                                   mOffCircuitPackets++;

\#350                            \}

\#351                            else

\#352                            \{

\#353                                   mInvalidOnCircuitPackets++;

\#354                            \}

\#355                     \}

\#356

\#357                     // Code for dumping the complete contents of a message

\#358                     // delete \[\] zero\_unexpanded\_buffer;

\#359              \}

\#360       \} while (!valid\_packet && receive\_size > 0);

\#361

\#362        F64 mt\_sec = getMessageTimeSeconds();

\#363       // Check to see if we need to print debug info

\#364       if ((mt\_sec - mCircuitPrintTime) > mCircuitPrintFreq)

\#365       \{

\#366              dumpCircuitInfo();

\#367              mCircuitPrintTime = mt\_sec;

\#368       \}

\#369

\#370       if( !valid\_packet )

\#371       \{

\#372              clearReceiveState();

\#373       \}

\#374

\#375       return valid\_packet;

\#376 \}

消息解包的实现，首先要做的任务，就是判断数据包是否有效，如果无效的数据包就需要丢掉，这样也可以提高网络的安全性，也可以丢掉错误的数据包引起的其它错误。最后使用消息模板实现数据的解释，获取每个字段所表达的意思。

![o_Snapshot_039.JPG][]

//蔡军生 2008/4/10 QQ:9073204 深圳

[o_Snapshot_039.JPG]: /images/20220824/38b2dfc76a1a4e19b5cffa916a4ba942.png

蔡军生先生第二人生的源码分析(三十三)消息解包的实现

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