book

The Sockets Networking API: UNIX® Network Programming Volume 1, Third Edition

by W. Richard Stevens, Bill Fenner, Andrew M. Rudoff

November 2003

Intermediate to advanced

1024 pages

25h 50m

English

Addison-Wesley Professional

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IntroductionChanges from the Second EditionUsing This BookSource Code and Errata AvailabilityAcknowledgments
1.1. Introduction1.2. A Simple Daytime ClientInclude our own headerCommand-line argumentsCreate TCP socketSpecify server’s IP address and portEstablish connection with serverRead and display server’s replyTerminate program1.3. Protocol Independence1.4. Error Handling: Wrapper FunctionsUnix errno Value1.5. A Simple Daytime ServerCreate a TCP socketBind server’s well-known port to socketConvert socket to listening socketAccept client connection, send replyTerminate connection1.6. Roadmap to Client/Server Examples in the Text1.7. OSI Model1.8. BSD Networking History1.9. Test Networks and HostsDiscovering Network Topology1.10. Unix StandardsBackground on POSIXBackground on The Open GroupUnification of StandardsInternet Engineering Task Force (IETF)1.11. 64-Bit Architectures1.12. SummaryExercises
2.1. Introduction2.2. The Big Picture2.3. User Datagram Protocol (UDP)2.4. Transmission Control Protocol (TCP)2.5. Stream Control Transmission Protocol (SCTP)2.6. TCP Connection Establishment and TerminationThree-Way HandshakeTCP OptionsTCP Connection TerminationTCP State Transition DiagramWatching the Packets2.7. TIME_WAIT State2.8. SCTP Association Establishment and TerminationFour-Way HandshakeAssociation TerminationSCTP State Transition DiagramWatching the PacketsSCTP Options2.9. Port NumbersSocket Pair2.10. TCP Port Numbers and Concurrent Servers2.11. Buffer Sizes and LimitationsTCP OutputUDP OutputSCTP Output2.12. Standard Internet Services2.13. Protocol Usage by Common Internet Applications2.14. SummaryExercises
3.1. Introduction3.2. Socket Address StructuresIPv4 Socket Address StructureGeneric Socket Address StructureIPv6 Socket Address StructureNew Generic Socket Address StructureComparison of Socket Address Structures3.3. Value-Result Arguments3.4. Byte Ordering Functions3.5. Byte Manipulation Functions3.6. inet_aton, inet_addr, and inet_ntoa Functions3.7. inet_pton and inet_ntop FunctionsExample3.8. sock_ntop and Related Functions3.9. readn, writen, and readline Functions3.10. SummaryExercises
4.1. Introduction4.2. socket FunctionAF_xxx Versus PF_xxx4.3. connect Function4.4. bind Function4.5. listen Function4.6. accept FunctionExample: Value-Result ArgumentsNew declarationsAccept connection and print client’s address4.7. fork and exec Functions4.8. Concurrent Servers4.9. close FunctionDescriptor Reference Counts4.10. getsockname and getpeername FunctionsExample: Obtaining the Address Family of a SocketAllocate room for largest socket address structureCall getsockname4.11. SummaryExercises

5.1. Introduction5.2. TCP Echo Server: main FunctionCreate socket, bind server’s well-known portWait for client connection to completeConcurrent server5.3. TCP Echo Server: str_echo FunctionRead a buffer and echo the buffer5.4. TCP Echo Client: main FunctionCreate socket, fill in Internet socket address structureConnect to server5.5. TCP Echo Client: str_cli FunctionRead a line, write to serverRead echoed line from server, write to standard outputReturn to main5.6. Normal Startup5.7. Normal Termination5.8. POSIX Signal Handlingsignal FunctionSimplify function prototype using typedefSet handlerSet signal mask for handlerSet SA_RESTART flagCall sigactionPOSIX Signal Semantics5.9. Handling SIGCHLD SignalsHandling ZombiesHandling Interrupted System Calls5.10. wait and waitpid FunctionsDifference between wait and waitpid5.11. Connection Abort before accept Returns5.12. Termination of Server Process5.13. SIGPIPE Signal5.14. Crashing of Server Host5.15. Crashing and Rebooting of Server Host5.16. Shutdown of Server Host5.17. Summary of TCP Example5.18. Data FormatExample: Passing Text Strings between Client and ServerExample: Passing Binary Structures between Client and Server5.19. SummaryExercises
6.1. Introduction6.2. I/O ModelsBlocking I/O ModelNonblocking I/O ModelI/O Multiplexing ModelSignal-Driven I/O ModelAsynchronous I/O ModelComparison of the I/O ModelsSynchronous I/O versus Asynchronous I/O6.3. select FunctionUnder What Conditions Is a Descriptor Ready?Maximum Number of Descriptors for select6.4. str_cli Function (Revisited)Call selectHandle readable socketHandle readable input6.5. Batch Input and Buffering6.6. shutdown Function6.7. str_cli Function (Revisited Again)6.8. TCP Echo Server (Revisited)Create listening socket and initialize for selectBlock in selectaccept new connectionsCheck existing connectionsDenial-of-Service Attacks6.9. pselect Function6.10. poll Function6.11. TCP Echo Server (Revisited Again)Allocate array of pollfd structuresInitializeCall poll, check for new connectionCheck for data on an existing connection6.12. SummaryExercises
7.1. Introduction7.2. getsockopt and setsockopt Functions7.3. Checking if an Option Is Supported and Obtaining the DefaultDeclare union of possible valuesDefine function prototypesDefine structure and initialize arrayGo through all optionsCreate socketCall getsockoptPrint option’s default value7.4. Socket States7.5. Generic Socket OptionsSO_BROADCAST Socket OptionSO_DEBUG Socket OptionSO_DONTROUTE Socket OptionSO_ERROR Socket OptionSO_KEEPALIVE Socket OptionSO_LINGER Socket OptionSO_OOBINLINE Socket OptionSO_RCVBUF and SO_SNDBUF Socket OptionsSO_RCVLOWAT and SO_SNDLOWAT Socket OptionsSO_RCVTIMEO and SO_SNDTIMEO Socket OptionsSO_REUSEADDR and SO_REUSEPORT Socket OptionsSO_TYPE Socket OptionSO_USELOOPBACK Socket Option7.6. IPv4 Socket OptionsIP_HDRINCL Socket OptionIP_OPTIONS Socket OptionIP_RECVDSTADDR Socket OptionIP_RECVIF Socket OptionIP_TOS Socket OptionIP_TTL Socket Option7.7. ICMPv6 Socket OptionICMP6_FILTER Socket Option7.8. IPv6 Socket OptionsIPV6_CHECKSUM Socket OptionIPV6_DONTFRAG Socket OptionIPV6_NEXTHOP Socket OptionIPV6_PATHMTU Socket OptionIPV6_RECVDSTOPTS Socket OptionIPV6_RECVHOPLIMIT Socket OptionIPV6_RECVHOPOPTS Socket OptionIPV6_RECVPATHMTU Socket OptionIPV6_RECVPKTINFO Socket OptionIPV6_RECVRTHDR Socket OptionIPV6_RECVTCLASS Socket OptionIPV6_UNICAST_HOPS Socket OptionIPV6_USE_MIN_MTU Socket OptionIPV6_V6ONLY Socket OptionIPV6_XXX Socket Options7.9. TCP Socket OptionsTCP_MAXSEG Socket OptionTCP_NODELAY Socket Option7.10. SCTP Socket OptionsSCTP_ADAPTION_LAYER Socket OptionSCTP_ASSOCINFO Socket OptionSCTP_AUTOCLOSE Socket OptionSCTP_DEFAULT_SEND_PARAM Socket OptionSCTP_DISABLE_FRAGMENTS Socket OptionSCTP_EVENTS Socket OptionSCTP_GET_PEER_ADDR_INFO Socket OptionSCTP_I_WANT_MAPPED_V4_ADDR Socket OptionSCTP_INITMSG Socket OptionSCTP_MAXBURST Socket OptionSCTP_MAXSEG Socket OptionSCTP_NODELAY Socket OptionSCTP_PEER_ADDR_PARAMS Socket OptionSCTP_PRIMARY_ADDR Socket OptionSCTP_RTOINFO Socket OptionSCTP_SET_PEER_PRIMARY_ADDR Socket OptionSCTP_STATUS Socket Option7.11. fcntl Function7.12. SummaryExercises
8.1. Introduction8.2. recvfrom and sendto Functions8.3. UDP Echo Server: main FunctionCreate UDP socket, bind server’s well-known port8.4. UDP Echo Server: dg_echo FunctionRead datagram, echo back to sender8.5. UDP Echo Client: main FunctionFill in socket address structure with server’s address8.6. UDP Echo Client: dg_cli Function8.7. Lost Datagrams8.8. Verifying Received ResponseAllocate another socket address structureCompare returned address8.9. Server Not Running8.10. Summary of UDP Example8.11. connect Function with UDPCalling connect Multiple Times for a UDP SocketPerformance8.12. dg_cli Function (Revisited)8.13. Lack of Flow Control with UDPUDP Socket Receive Buffer8.14. Determining Outgoing Interface with UDP8.15. TCP and UDP Echo Server Using selectCreate listening TCP socketCreate UDP socketEstablish signal handler for SIGCHLDPrepare for selectCall selectHandle new client connectionHandle arrival of datagram8.16. SummaryExercises
9.1. Introduction9.2. Interface ModelsThe One-to-One StyleThe One-to-Many Style9.3. sctp_bindx Function9.4. sctp_connectx Function9.5. sctp_getpaddrs Function9.6. sctp_freepaddrs Function9.7. sctp_getladdrs Function9.8. sctp_freeladdrs Function9.9. sctp_sendmsg Function9.10. sctp_recvmsg Function9.11. sctp_opt_info Function9.12. sctp_peeloff Function9.13. shutdown Function9.14. NotificationsSCTP_ASSOC_CHANGESCTP_PEER_ADDR_CHANGESCTP_REMOTE_ERRORSCTP_SEND_FAILEDSCTP_SHUTDOWN_EVENTSCTP_ADAPTION_INDICATIONSCTP_PARTIAL_DELIVERY_EVENT9.15. SummaryExercises
10.1. Introduction10.2. SCTP One-to-Many-Style Streaming Echo Server: main FunctionSet stream increment optionCreate an SCTP socketBind an addressSet up for notifications of interestEnable incoming associationsWait for messageIncrement stream number if desiredSend back response10.3. SCTP One-to-Many-Style Streaming Echo Client: main FunctionValidate arguments and create a socketSet up server addressSet up for notifications of interestCall echo processing functionFinish up10.4. SCTP Streaming Echo Client: str_cli FunctionInitialize the sri structure and enter loopValidate inputTranslate stream numberSend messageBlock while waiting for messageDisplay returned message and loopRunning the Code10.5. Exploring Head-of-Line BlockingInitialize data structures and wait for inputPre-process messageSend message to each streamRead back echoed messages and displayRunning the CodeAdd additional message number and sendChange message number and send it againRead messages and displayRunning the Modified Code10.6. Controlling the Number of StreamsInitial setupModifying the streams request10.7. Controlling TerminationSend back response, but shut down associationAbort association before closeClose socket descriptor10.8. SummaryExercises
11.1. Introduction11.2. Domain Name System (DNS)Resource RecordsResolvers and Name ServersDNS Alternatives11.3. gethostbyname FunctionExample11.4. gethostbyaddr Function11.5. getservbyname and getservbyport FunctionsExample: Using gethostbyname and getservbynameCall gethostbyname and getservbynameTry each server addressCall connectCheck for failureRead server’s reply11.6. getaddrinfo Function11.7. gai_strerror Function11.8. freeaddrinfo Function11.9. getaddrinfo Function: IPv611.10. getaddrinfo Function: Examples11.11. host_serv Function11.12. tcp_connect FunctionCall getaddrinfoTry each addrinfo structure until success or end of listExample: Daytime ClientCommand-line argumentsConnect to serverPrint server’s address11.13. tcp_listen FunctionCall getaddrinfoCreate socket and bind addressCheck for failureReturn size of socket address structureExample: Daytime ServerRequire service name or port number as command-line argumentCreate listening socketServer loopExample: Daytime Server with Protocol SpecificationHandle command-line arguments11.14. udp_client FunctionExample: Protocol-Independent Daytime Client11.15. udp_connect Function11.16. udp_server FunctionExample: Protocol-Independent Daytime Server11.17. getnameinfo Function11.18. Re-entrant Functions11.19. gethostbyname_r and gethostbyaddr_r Functions11.20. Obsolete IPv6 Address Lookup FunctionsThe RES_USE_INET6 ConstantThe gethostbyname2 FunctionThe getipnodebyname Function11.21. Other Networking Information11.22. SummaryExercises
12.1. Introduction12.2. IPv4 Client, IPv6 Server12.3. IPv6 Client, IPv4 ServerSummary of Interoperability12.4. IPv6 Address-Testing Macros12.5. Source Code Portability12.6. SummaryExercises
13.1. Introduction13.2. syslogd Daemon13.3. syslog Function13.4. daemon_init FunctionforksetsidIgnore SIGHUP and Fork AgainSet Flag for Error FunctionsChange Working DirectoryClose any open descriptorsRedirect stdin, stdout, and stderr to /dev/nullUse syslogd for ErrorsExample: Daytime Server as a Daemon13.5. inetd Daemon13.6. daemon_inetd FunctionExample: Daytime Server as a Daemon Invoked by inetdCall getpeername13.7. SummaryExercises
14.1. Introduction14.2. Socket Timeoutsconnect with a Timeout Using SIGALRMEstablish signal handlerSet alarmCall connectTurn off alarm and restore any previous signal handlerHandle SIGALRMrecvfrom with a Timeout Using SIGALRMHandle timeout from recvfromSIGALRM signal handlerrecvfrom with a Timeout Using selectPrepare arguments for selectBlock in selectrecvfrom with a Timeout Using the SO_RCVTIMEO Socket OptionSet socket optionTest for timeout14.3. recv and send Functions14.4. readv and writev Functions14.5. recvmsg and sendmsg Functions14.6. Ancillary Data14.7. How Much Data Is Queued?14.8. Sockets and Standard I/OExample: str_echo Function Using Standard I/OConvert descriptor into input stream and output stream14.9. Advanced Polling/dev/poll InterfaceList descriptors for /dev/pollWait for workLoop through descriptorskqueue InterfaceDetermine if file pointer points to a fileSet up kevent structures for kqueueCreate kqueue and add filtersLoop forever, blocking in keventLoop through returned eventsSocket is readableInput is readableSuggestions14.10. SummaryExercises
15.1. Introduction15.2. Unix Domain Socket Address StructureExample: bind of Unix Domain SocketRemove pathname firstbind and then getsockname15.3. socketpair Function15.4. Socket Functions15.5. Unix Domain Stream Client/Server15.6. Unix Domain Datagram Client/Server15.7. Passing DescriptorsDescriptor Passing ExampleCreate stream pipefork and execParent waits for childReceive descriptorMake certain msg_control is suitably alignedCommand-line argumentsopen the filePass back descriptor15.8. Receiving Sender CredentialsExample15.9. SummaryExercises
16.1. Introduction16.2. Nonblocking Reads and Writes: str_cli Function (Revisited)Set descriptors to nonblockingInitialize buffer pointersMain loop: prepare to call selectSpecify descriptors we are interested inCall selectread from standard inputHandle nonblocking errorread returns EOFread returns dataread from socketwrite to standard outputwrite OKwrite to socketA Simpler Version of str_cliTiming of str_cli16.3. Nonblocking connect16.4. Nonblocking connect: Daytime ClientSet socket nonblockingOverlap processing with connection establishmentCheck for immediate completionCall selectHandle timeoutsCheck for readability or writabilityTurn off nonblocking and returnInterrupted connect16.5. Nonblocking connect: Web ClientDefine file structureDefine globals and function prototypesProcess command-line argumentsRead home pageInitialize globalsEstablish connection with serverSend HTTP command to server, read replyCreate socket, set to nonblockingInitiate nonblocking connectHandle connection completeBuild command and send itSet flagsInitiate another connection, if possibleselect: wait for something to happenHandle all ready descriptorsSee if descriptor has dataPerformance of Simultaneous Connections16.6. Nonblocking acceptSet SO_LINGER socket option16.7. SummaryExercises
17.1. Introduction17.2. ioctl Function17.3. Socket Operations17.4. File Operations17.5. Interface Configuration17.6. get_ifi_info FunctionCreate Internet SocketIssue SIOCGIFCONF Request in a LoopInitialize Linked List PointersStep to Next Socket Address StructureHandle AF_LINKHandle AliasesFetch Interface FlagsAllocate and Initialize ifi_info Structure17.7. Interface Operations17.8. ARP Cache OperationsExample: Print Hardware Addresses of HostGet List of Addresses and Loop Through Each OnePrint IP AddressIssue ioctl and Check for ErrorPrint Hardware Address17.9. Routing Table Operations17.10. SummaryExercises
18.1. Introduction18.2. Datalink Socket Address Structure18.3. Reading and WritingExample: Fetch and Print a Routing Table EntryCreate routing socketFill in rt_msghdr structureFill in Internet socket address structure with destinationwrite message to kernel and read replyLoop through eight possible pointersStep to next socket address structure18.4. sysctl OperationsExample: Determine if UDP Checksums Are EnabledInclude system headersCall sysctl18.5. get_ifi_info Function (Revisited)Check if interface is upDetermine which socket address structures are presentHandle interface nameReturn IP addressesReturn broadcast and destination addresses18.6. Interface Name and Index Functionsif_nametoindex FunctionGet interface listProcess only RTM_IFINFO messagesif_indextoname Functionif_nameindex FunctionGet interface list, allocate room for resultProcess only RTM_IFINFO messagesTerminate arrayif_freenameindex Function18.7. SummaryExercises
19.1. Introduction19.2. Reading and Writing19.3. Dumping the Security Association Database (SADB)Open PF_KEY socketBuild SADB_DUMP requestDisplay and write SADB_DUMP messageRead repliesClose PF_KEY socketHandle command-line argumentsCall sadb_dump routineSample Run19.4. Creating a Static Security Association (SA)Open PF_KEY socket and save PIDBuild common message headerAppend SA extensionAppend source addressAppend destination addressAppend keyWrite messageRead replyExample19.5. Dynamically Maintaining SAsOpen PF_KEY socketStore PIDCreate SADB_REGISTER messageDisplay and write message to socketWait for replyExample19.6. SummaryExercises
20.1. Introduction20.2. Broadcast Addresses20.3. Unicast versus Broadcast20.4. dg_cli Function Using BroadcastingAllocate room for server’s address, set socket optionRead line, send to socket, read all repliesPrint each received replyIP Fragmentation and Broadcasts20.5. Race ConditionsBlocking and Unblocking the SignalDeclare signal set and initializeUnblock and block signalBlocking and Unblocking the Signal with pselectUsing sigsetjmp and siglongjmpAllocate jump bufferCall sigsetjmpHandle SIGALRM and call siglongjmpUsing IPC from Signal Handler to FunctionCreate pipeselect on both socket and read end of piperead from pipe20.6. SummaryExercises
21.1. Introduction21.2. Multicast AddressesIPv4 Class D AddressesIPv6 Multicast AddressesScope of Multicast AddressesMulticast Sessions21.3. Multicasting versus Broadcasting on a LAN21.4. Multicasting on a WAN21.5. Source-Specific Multicast21.6. Multicast Socket OptionsIP_ADD_MEMBERSHIP, IPV6_JOIN_GROUP, MCAST_JOIN_GROUPIP_DROP_MEMBERSHIP, IPV6_LEAVE_GROUP, MCAST_LEAVE_GROUPIP_BLOCK_SOURCE, MCAST_BLOCK_SOURCEIP_UNBLOCK_SOURCE, MCAST_UNBLOCK_SOURCEIP_ADD_SOURCE_MEMBERSHIP, MCAST_JOIN_SOURCE_GROUPIP_DROP_SOURCE_MEMBERSHIP, MCAST_LEAVE_SOURCE_GROUPIP_MULTICAST_IF, IPV6_MULTICAST_IFIP_MULTICAST_TTL, IPV6_MULTICAST_HOPSIP_MULTICAST_LOOP, IPV6_MULTICAST_LOOP21.7. mcast_join and Related FunctionsExample: mcast_join FunctionHandle indexCopy address and call setsockoptHandle indexHandle nameSpecify defaultCopy addressHandle index, name, or defaultExample: mcast_set_loop Function21.8. dg_cli Function Using MulticastingIP Fragmentation and Multicasts21.9. Receiving IP Multicast Infrastructure Session AnnouncementsWell-Known name and Well-Known portCreate UDP socketbind portJoin multicast groupPacket formatRead UDP datagram, print sender and contentsCheck SAP headerFind beginning of announcement and print21.10. Sending and ReceivingCreate sending socketCreate receiving socket and bind multicast address and portJoin multicast group and turn off loopbackfork and call appropriate functionsObtain hostname and form datagram contentsSend datagram, then go to sleepAllocate socket address structureRead and print datagramsExample21.11. Simple Network Time Protocol (SNTP)Get multicast IP addressBind wildcard address to socketGet interface listJoin multicast groupRead and process all NTP packetsValidate packetObtain transmit time from NTP packet21.12. SummaryExercises
22.1. Introduction22.2. Receiving Flags, Destination IP Address, and Interface IndexInclude filesFunction argumentsImplemenation differencesFill in msghdr structure and call recvmsgReturn if no control informationProcess ancillary dataProcess IP_RECVDSTADDRProcess IP_RECVIFExample: Print Destination IP Address and Datagram-Truncated FlagChange MAXLINESet IP_RECVDSTADDR and IP_RECVIF socket optionsRead datagram, print source IP address and portPrint destination IP addressPrint name of received interfaceTest various flags22.3. Datagram Truncation22.4. When to Use UDP Instead of TCP22.5. Adding Reliability to a UDP ApplicationExampleDefine msghdr structures and hdr structureInitialize first time we are calledFill in msghdr structuresEstablish signal handlerSend datagramEstablish jump bufferHandle timeoutCall recvmsg, compare sequence numbersTurn off alarm and update RTT estimatorsSIGALRM handlerrtt_info structure22.6. Binding Interface AddressesCall get_ifi_info, to obtain interface informationCreate UDP socket and bind unicast addressfork child for this addressBind broadcast addressfork childCreate socket and bind wildcard addressmain function terminatesNew argumentRead datagram and echo reply22.7. Concurrent UDP Servers22.8. IPv6 Packet InformationOutgoing and Arriving InterfaceSource and Destination IPv6 AddressesSpecifying and Receiving the Hop LimitSpecifying the Next-Hop AddressSpecifying and Receiving the Traffic Class22.9. IPv6 Path MTU ControlSending with Minimum MTUReceiving Path MTU Change IndicationsDetermining the Current Path MTUAvoiding Fragmentation22.10. SummaryExercises
23.1. Introduction23.2. An Autoclosing One-to-Many-Style ServerSet autoclose option23.3. Partial DeliveryPrepare static bufferRead messageHandle initial read errorWhile there is more data for this messageSee if we need to grow static bufferReceive more dataMove forwardAt loop endRead messageVerify we read something23.4. NotificationsCast and switchProcess association changePeer address changeRemote errorFailed messageAdaption layer indicationPartial delivery notificationShutdown notificationSet up to receive notificationsNormal receive codeHandle notificationRunning the Code23.5. Unordered DataSend data using unordered service23.6. Binding a Subset of AddressesAllocate space for bind argumentsProcess argumentsCall binding functionReturn successServer code using IPv6Use the new sctp_bind_arg_list function23.7. Determining Peer and Local Address InformationSet events and call echo functionLoop waiting for messageCheck for notificationsLoop while waiting for dataDisplay messageCheck if it is notification we wantGather and print peer addressesGather and print local addressesProcess each addressPrint addressDetermine address sizeMove address pointerRunning the Code23.8. Finding an Association ID Given an IP AddressInitializeCopy addressCall socket option23.9. Heartbeating and Address FailureZero sctp_paddrparams struct and copy intervalSet up addressPerform action23.10. Peeling Off an AssociationReceive and process first message from clientTranslate address to association IDExtract associationDelegate work to child23.11. Controlling Timing23.12. When to Use SCTP Instead of TCP23.13. SummaryExercises
24.1. Introduction24.2. TCP Out-of-Band DataSimple Example Using SIGURGEstablish signal handler and socket ownerSIGURG handlerSimple Example Using select24.3. sockatmark FunctionExampleSet SO_OOBINLINE socket optionsleep after connection acceptedRead all data from senderExampleExample24.4. TCP Out-of-Band Data Recap24.5. SummaryExercises
25.1. Introduction25.2. Signal-Driven I/O for SocketsSIGIO with UDP SocketsSIGIO with TCP Sockets25.3. UDP Echo Server Using SIGIOQueue of received datagramsArray indexesInitialize queue of received datagramsEstablish signal handlers and set socket flagsInitialize signal setsBlock SIGIO and wait for something to doUnblock SIGIO and send replyBlock SIGIOCheck for queue overflowRead datagramIncrement counters and index25.4. SummaryExercises
26.1. Introduction26.2. Basic Thread Functions: Creation and Terminationpthread_create Functionpthread_join Functionpthread_self Functionpthread_detach Functionpthread_exit Function26.3. str_cli Function Using Threadsunpthread.h headerSave arguments in externalsCreate new threadMain thread loop: copy socket to standard outputTerminatecopyto thread26.4. TCP Echo Server Using ThreadsCreate threadThread functionPassing Arguments to New ThreadsThread-Safe Functions26.5. Thread-Specific DataExample: readline Function Using Thread-Specific DataDestructorOne-time functionRline structuremy_read functionAllocate thread-specific dataFetch thread-specific data pointer26.6. Web Client and Simultaneous Connections (Continued)GlobalsIf possible, create another threadWait for any thread to terminateCreate TCP socket, establish connectionWrite request to serverRead server’s reply26.7. Mutexes: Mutual Exclusion26.8. Condition Variables26.9. Web Client and Simultaneous Connections (Continued)If possible, create another threadWait for thread to terminateHandle terminated thread26.10. SummaryExercises
27.1. Introduction27.2. IPv4 Options27.3. IPv4 Source Route OptionsInitializeArgumentCheck for overflowObtain binary IP address and store in routeSave first IP address, skip any NOPsCheck for source route optionExampleProcess command-line argumentsHandle destination address and create socketDeleting Received Source Route27.4. IPv6 Extension Headers27.5. IPv6 Hop-by-Hop Options and Destination Options27.6. IPv6 Routing HeaderCreate source routeLook up destination and create socketSet sticky IPV6_RTHDR option and call worker functionTurn on IPV6_RECVRTHDR option and set up msghdr structSet up modifiable fields and call recvmsgFind and process route headerEcho packetDetermine number of segments in routeLoop through each segment27.7. IPv6 Sticky Options27.8. Historical IPv6 Advanced API27.9. SummaryExercises
28.1. Introduction28.2. Raw Socket Creation28.3. Raw Socket OutputIPv6 DifferencesIPV6_CHECKSUM Socket Option28.4. Raw Socket InputICMPv6 Type Filtering28.5. ping ProgramInclude IPv4 and ICMPv4 headersDefine proto structureInclude IPv6 and ICMPv6 headersDefine proto structures for IPv4 and IPv6Length of optional dataHandle command-line optionsProcess hostname argumentCreate socketPerform protocol-specific initializationSet socket receive buffer sizeSend first packetSet up msghdr for recvmsgInfinite loop reading all ICMP messagesGet pointer to ICMP headerCheck for ICMP echo replyPrint all received ICMP messages if verbose option specifiedSet ICMPv6 receive filterRequest IPV6_HOPLIMIT ancillary dataGet pointer to ICMPv6 headerCheck for ICMP echo replyPrint all received ICMP messages if verbose option specifiedBuild ICMPv4 messageCalculate ICMP checksumSend datagramInternet checksum algorithm28.6. traceroute ProgramDefine proto structureInclude IPv6 headersDefine proto structuresSet defaultsProcess command-line argumentsProcess hostname or IP address argument and finish initializationCreate raw socketSet ICMPv6 receive filterCreate UDP socket and bind source portEstablish signal handler for SIGALRMMain loop; set TTL or hop limit and send three probesSet destination port and send UDP datagramRead ICMP messagePrint replySet alarm and read each ICMP messageGet pointer to ICMP headerProcess ICMP “time exceeded in transit” messageProcess ICMP “port unreachable” messageHandle other ICMP messagesExample28.7. An ICMP Message DaemonUDP Echo Client That Uses Our icmpd Daemonbind wildcard address and ephemeral portEstablish Unix domain connection to daemonSend UDP socket to daemon, await daemon’s replyCall selectPrint server’s replyHandle ICMP errorUDP Echo Client Examplesicmpd Daemonclient arrayInitialize client arrayCreate socketsCheck listening Unix domain socketCheck raw ICMP socketsCheck connected Unix domain socketsRead client data and possibly a descriptorGet port number bound to UDP socketIndicate success to clientclose client’s UDP socketHandle errors and termination of clientCheck message type, notify applicationCheck for UDP error, find clientBuild icmpd_err structure28.8. SummaryExercises
29.1. Introduction29.2. BSD Packet Filter (BPF)29.3. Datalink Provider Interface (DLPI)29.4. Linux: SOCK_PACKET and PF_PACKET29.5. libpcap: Packet Capture Library29.6. libnet: Packet Creation and Injection Library29.7. Examining the UDP Checksum FieldProcess command-line optionsProcess destination name and portProcess local name and portCreate raw socket and open packet capture deviceChange permissions and establish signal handlersPerform test and cleanupChoose packet capture deviceOpen deviceObtain network address and subnet maskCompile packet filterLoad filter programDetermine datalink typevolatile variablesEstablish signal handler and jump bufferHandle siglongjmpSend DNS query and read replyExamine received UDP checksumAllocate buffer and initialize pointerBuild DNS queryWrite UDP datagramDeclare raw socket descriptorCreate raw socket and enable IP_HDRINCLInitialize packet header pointersZero headerUpdate lengthsFill in UDP header and calculate UDP checksumFill in IP headerFetch and print packet capture statisticsExamplelibnet Output FunctionsDeclare libnet descriptorInitialize libnetBuild DNS queryFill in UDP header and arrange for UDP checksum calculationFill in IP headerWrite UDP datagram29.8. SummaryExercises
30.1. Introduction30.2. TCP Client Alternatives30.3. TCP Test Client30.4. TCP Iterative Server30.5. TCP Concurrent Server, One Child per Client30.6. TCP Preforked Server, No Locking Around accept4.4BSD ImplementationEffect of Too Many ChildrenDistribution of Connections to the Childrenselect Collisions30.7. TCP Preforked Server, File Locking Around acceptEffect of Too Many ChildrenDistribution of Connections to the Children30.8. TCP Preforked Server, Thread Locking Around accept30.9. TCP Preforked Server, Descriptor PassingTurn off listening socket if no available childrenaccept new connectionHandle any newly available childrenWait for descriptor from parentTell parent we are ready30.10. TCP Concurrent Server, One Thread per ClientMain thread loopPer-thread function30.11. TCP Prethreaded Server, per-Thread acceptCreate thread30.12. TCP Prethreaded Server, Main Thread acceptDefine shared array to hold connected socketsCreate pool of threadsWait for each client connectionWait for client descriptor to service30.13. SummaryExercises
31.1. Introduction31.2. OverviewMessage Types31.3. getmsg and putmsg Functions31.4. getpmsg and putpmsg Functions31.5. ioctl Function31.6. Transport Provider Interface (TPI)Open transport provider, bind local addressFill in server’s address, establish connectionRead data from server, copy to standard outputFill in T_bind_req structureCall putmsgCall getmsg to read high-priority messageProcess replyFill in request structure and send to providerRead responseWait for connection to be establishedRead control and data; process replySend orderly release to peer31.7. SummaryExercises
A.1. IntroductionA.2. IPv4 HeaderA.3. IPv6 HeaderA.4. IPv4 AddressesSubnet AddressesLoopback AddressesUnspecified AddressPrivate AddressesMultihoming and Address AliasesA.5. IPv6 AddressesGlobal Unicast Addresses6 bone Test AddressesIPv4-Mapped IPv6 AddressesIPv4-Compatible IPv6 AddressesLoopback AddressUnspecified AddressLink-Local AddressSite-Local AddressA.6. Internet Control Message Protocols (ICMPv4 and ICMPv6)
B.1. IntroductionB.2. The MBoneB.3. The 6boneB.4. IPv6 Transition: 6to4
C.1. System Call TracingBSD Kernel SocketsSolaris 9 Kernel SocketsC.2. Standard Internet ServicesC.3. sock ProgramC.4. Small Test ProgramsC.5. tcpdump ProgramC.6. netstat ProgramC.7. lsof Program
D.1. unp.h HeaderD.2. config.h HeaderD.3. Standard Error Functions
Chapter 1Chapter 2Chapter 3Chapter 4Chapter 5Chapter 6Chapter 7Chapter 8Chapter 9Chapter 10Chapter 11Chapter 12Chapter 13Chapter 14Chapter 15Chapter 16Chapter 17Chapter 18Chapter 20Chapter 21Chapter 22Chapter 24Chapter 25Chapter 26Chapter 27Chapter 28Chapter 29Chapter 30Chapter 31

Content preview from The Sockets Networking API: UNIX® Network Programming Volume 1, Third Edition

Chapter 29. Datalink Access

Introduction

Providing access to the datalink layer for an application is a powerful feature that is available with most current operating systems. This provides the following capabilities:

The ability to watch the packets received by the datalink layer, allowing programs such as tcpdump to be run on normal computer systems (as opposed to dedicated hardware devices to watch packets). When combined with the capability of the network interface to go into a promiscuous mode, this allows an application to watch all the packets on the local cable, not just the packets destined for the host on which the program is running.
- This ability is less useful in switched networks, which have become quite common. This is because the switch ...

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