Linux网络通信详解

8LinuxLinuxInternet()WorldWideWeb()LinuxLinuxTCP/IPTCP/IP/(TransmissionControlProtocol/InternetProtocol)TCP/IPARPANET1988ARPANETNSFNETNSFNET(Internet)(WorldWideWeb)ARPAnetTCP/IPUNIXARPANET4.3BSD(BerkeleySoftwareDistribution)BSD()TCP/IPLinuxLinux4.3BSDLinuxUNIX8.1TCP/IPTCP/IPTCP/IP32IPIPIP0x81124C15(16)129.18.76.21IP(network)(host)IPB(IP128191)IPB6553665536IP()(subnetwork)IP16.42.0.916.42.016.42.0.916.42ACME16.42.0016.42.11IPIPIPIP(DamainNameService,DNS)IPIPIP893()DNSIPLinux/etc/hosts(DistributedNameServer,DNS)DNSIP/etc/resolv.confWebIPIPIPIPIPIPIP(1-8-1)IPIPIP(PainttoPointProtocal,PPP)IP(IDENTIFICATION)(FLAG)(FRAGMENTOFFSET)1-8-1IP(Gateway)()16.42.1.016.42.0.016.42.1.016.42.0.0IPnetstat1-8-2dai%netstat-rnKernelroutingtableDestinatonGatevayaddressFlagsRefcntUseIfacenet/address16.42.0.016.42.0.12UN01432eth0default16.42.0.1UGN01432eth017.0.0.117.0.0.1UH012to16.42.0.1217.0.0.1UH012to1-8-2netstat94Linux16.42.016.42.0.12IPFlagsUupNRefcntUseIfaceeth0loloopback16.42.0.116.42.016.42.0.117.0.0.1loopbackTCP/IPloloopback(eth0)16.42.0.12IP17.0.0.1(1-8-3)16.42.0.10916.42.1.4Destinationnet/addressGatewayaddressFlagsRefcntUseIface16.42.0.016.42.0.109UN01432eth016.42.1.016.42.1.4UN01432eth1default16.42.1.43UGN01432eth117.0.0.117.0.0.1UH012to16.42.0.10917.0.0.1UH012to1-8-3netstateth016.42.0eth116.42.116.42.016.42.0.10916.42.0.10916.42.1.43IPTCPIPTCP(UserDatagramProtocol,UDP)IPIPIPIP()IP(1-8-1)(PROTOCOL)TCP/UDP(protocolport)Web80/etc/servicesTCPUDPIPIPIP89548hardwareaddressphysicaladdress6(IEEE)(48)IPIPIPIPIPLinux(AddressResolutionProtocol,ARP)(ReverseAddressResolutionProtocol,RARP)ARPIPRARPIPABIPIBAARPIPIBPB(B)ARPBIBAARPPBARPFDDIRARPIPARP8.2LinuxTCP/IP1-8-4Linux1-8-4LinuxIPLinuxNetworkApplicationsBSDSocketsINETSocketsTCPUDPIPNetworkDevicesProtocolLayersSocketInterfacePPPSLIPEthernetUserKernelARPBSDSocketINETIPTCPUDPTCPUDPUDPLinuxTCPIPIPIPTCPUDPIPLinux(PointtoPointProtocol,PPP)Linuxmknod/dev/eth0ARPIP8.3BSDLinuxUNIXUnixINETTCP/IPAX25X25IPXIPXAPPLETALKAPPLETALKX25X25LinuxTCP/IPLinuxBSD•StreamINETTCP•Datagram(message)INETUDP•RawRawIP•ReliableDeliveredMessagesDatagram•SequencedPacketsStream•PacketLinuxBSD96LinuxWebWebWebWebsockaddrINETIPWeb80/etc/servicesINETIPBSDTCP/IPX.25LinuxBSDBSDBSDBSDBSDBSD(protocolvector)INETpopspopsproto_opsproto_opspopsINET28.4INETINET(socket)TCP/IPINETAddressFamilyLinuxTCP/IPINETINETBSDpopsBSDINETproto_opsINETBSDBSDINETINETBSDTCP/IPsockBSDsocket1-8-5BSDsocketdata()sockBSDsocketINET897TCPTCPTCP1-8-5LinuxBSD8.4.1BSDsocket()popskerneldBSDVFS(VirtualFileSystem)VFSVFSBSDVFSBSDproto_opsSOCK_STREAMSOCK_DGRAMproto_opsfd(Filedescriptor)file()BSDBSD98Linuxfiles_structf_modef_posf_flagsf_countf_ownerf_opf_nodef_versioninodeBSDlseekreadwriteselectioctlclosefasyncSOCK_STREAMsockettypeopsdatasockSOCK_STREAMtypeprotocolsocketcountclose_on_execopen_fsfd[0]fd[1]fd[255]8998.4.2INETBSDSocketINETTCPUDPTCP_CLOSEIP()IPINET(ifconfig)IP10IPrecv_addrsaddrIP10241024INETBSDTCPUDP(hash)IPBSDIPTCPTCPUDPUDPsockUDPsocksocknextTCPTCP(bind)sock(listen)TCP8.4.3INETBSDSocketUDPTCPINETBSDSS_UNCONNECTEDUDPBSDUDPINETBSDIP(cache)BSD()INETsockip_route_cacheBSDUDPsockTCP_ESTABLISHEDTCPBSDTCPIPTCPLinux100Linuxsocktcp_listening_hashsockTCP8.4.4INETBSDSocket(INET)TCP_LISTENUDPTCPsocktcp_bound_hashtcp_listonry_hashTCPTCPsocksockTCPsk_buffsockreceive_queuesk_buffsock8.4.5UDPINETTCPINET(UDP)INETTCPTCPsk_buffsockINET(fd)INETBSD8.5IP8.5.1Linuxsk_buffsk_buff1-8-6sk_buffsk_buffsk_buff48101•headsk_buff•datask_buff•taildatask_buff•endsk_buffa.lenb.truesize1-8-6sk_buffsk_buffdatataillen•pushdatalen•pulldataendlen•puttailendlenend•trimtaillensk_buffsk_buffsk_buffsk_buffsk_buff8.5.2IP6Linuxdev_base102Linuxsk_buffsk_buffbacklogbacklogsk_buffsk_buffbottomhalfbottomhalfsk_buffbacklogLinuxpacket_typeptype_allptype_basepacket-typepacket_type()ptype_allptype_basebottomhalfsk_buffsk_buff8.5.3IPsk_buffsk_buffIPmodemPPPPPPmodemIPIPrtableIPIP1-8-7IPIPIPARPIPARP1-8-78.5.4ETHERNETFRAME8103IPIPIPIP(MaximumTransferUnit,MTU)MTUIPIPsk_buffIPIPsk_buff1-8-8241600MTU7001-8-8IPa)1600b)IPIPIPipqipqueueipqipfragipqIPIPsk_buffipqipqipfrag8.6(AddressResolutionProtocol,ARP)IP()IPIPLinuxARPIPARPARPARPARPIPIP1231231(700)2(700)3(200)1(0)2(700)3(1400)a)b)LinuxARParp_tablearp_tableIPIParp_tablelastusedARPlastupdatedARPflagsIPaddressIPhardwareaddresshardwareheadertimertimer_listARPretriesARPsk_buffqueuesk_buffARPARParp_tablesIPARPIPLinuxhh_cachearp_tableIParp_tableARPARPARParp_tablearp_tablesk_buffsk_buffARPARParp_tablesk_buffsk_buffUDPTCParp_tablesk_buffsk_buffARPIPARP(ETH_P_ARP)packet_typeARPARPdeviceIPIPARPARPARParp_tablearp_tableARPARPARP8.7IPIP(ForwardingInformationDatabase)IP104Linux(ip_rt_hash_table)rtableIPrtableIPIP111(1-8-9)IP1-8-98105fib_zoneIPfib_zonesfib_zoneIPfib_zonefib_listfib_listfib_nodefib_infofib_nodeIPIP(hop)IP106Linux