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Linux2.4网络内核源代码阅读笔记
应用层网络接口
#include<sys/types.h>
#include<sys/socket.h>
intsocket(intfamily,inttype,intprotocol)
/东服务器与客户端都调用socket。来建立socket*/
其中:(1)family指明套节字协议族,其值包括:
AF_UNIX(UNIX内部协议族)
AF_INET(Internet协议族)
AF_NS(XeroxNs协议,TCP/IP编程取该值)
AF_IMPLINK(IMP链接层)
(2)type指明套接字类型,取值有:
SOCK_STREAM(流套接字)
SOCK_DGRAM(数据报套接字)
SOCK_RAW(原始套接字)
SOCK_SEQPACKET(定序分组套接字)
股情况卜.,前两个参数的组合的可以决定所使用的协议,这时第三个参数被置为0,如果第一个参数为AFJNET
第:个参数选SOCK_STREAM,则使用的协议为TCP;第.个参数选SOCK_DGRAM,则使用的协议为UDP:
当第:个参数选SOCK_RAW时,使用的协议为IP。值得指出的是并不是所有的族和类型的组合都是合法的,
具体请查阅相关资料。该系统调用若成功则返一个类似文件描述符,称为套接口描述字,可以像文件描述符
那样用read和write对其进行I/O操作。当一个进程使用完该软插座时,需用close(<描述符〉)关闭。
intbind(intsocketfd,structsockaddrjn*localaddr,sizeof(structsockaddrjn))
/*服务器端Bind系统调用*/
其中:
(1)第一个参数socketfd是前步socket。系统调用返回的套节字描述符。
(2)笫二个参数被捆向本地地址的一种结构,该结构在sys/netinet/in.h中定义:
structsockaddr_in{
shortsin_family;/*socket。系统调用的协议族如AF_INET*/
u_shortsin_port;/*网络字节次序形式的端口号码*/
structin_addrsin_addr;/*网络字节次序形式的网络地址*/
charsin_zero[8];
):
/'一台机器上的每一个网络程序都使用一个各自独立的网络端口号。如telnet使用23端口
ftp使用21端口,我们在写程序的时候,可以通过调用getservbyname。函数从etc/services
辉文件中得到端口号,也可以使用htons(intportnum)函数k转换为网络字节次序
来得到,有些版本的unix规定1024以卜一端口只能被超级用户使用,普通用户只能使用
1025-32767之间的端I」号,网络地址可以由gethostbyname(char*hostname)函数得到
(该函数与getservbyname()一样都是以网络字节次序形式返回所有在他们结构中的数据),
参数hostname为etc/hosts文件中某个网络地址所对应的机器名,该函数返回一个类型为
hostent的结构体指针,该结构体hostent在netdb.h
*/
structhostent{
char*h_name;
char**h_aliases;
inth_addrtype;
inth」ength;/*地址长度*/
char**h_addr_list;
井defineh_addrh_addr_list[O];/*地址*/
}:
(3)笫:个参数为第.个结构参数的长度,如果调用成功,bind返回0,否则将返回一1并设置errno。
intlisten(intsockedfd,intbacklog)
/*面向连接的服务器端系统调用listen,表示服务器愿意接受连接*/
它通常是在socket。和bind。调用后,在accept。调用前执行。第二个参数指定accept
调用时系统可以等待多少个连接请求o
intnewsocket=accept(intsocketfd,structsockaddrjn*peer,int*addlen);
/*服务器调用accept,以等待客户机调用connect进行连接。*/
调用等待队列中的第一个连接请求,并建立一个与socketfd一样特征的套接字。
如果没有等待的连接请求,此调用阻塞调用者一直到连接请求到达。
连接成功后,该accept。调用将把对端的地址结构和地址长度放到到参数peer和addlen中,
如果服务器端对客户端的地址信息不感兴趣,这两个参数可以用0代替。
intconnect(intsocketfd,structsockaddrjn*servsaddr,intaddrlen)
/*客户端调用connect。与服务器建立连接*/
客户端取得套接字描述符后,用该connect。调用建立。服务器的连接,
参数socketfd为socket。调用返回的套接字描述符,第和第1个参数是指向想要连接的
目的地址的结构和地址长度。调用成功返回0,否则将返回一1并设置errno.
/*通过建立的socket发送和接收数据*/
一旦建立连接,就可以通过调用read()和write像普通文件一样向网络上发送和接收数据。
intread(intsockfd,char*buff,intnbytes)
Read。有三个参数:一个是套接字描述符,个为数据将被加入的数据缓冲区,还仃一个整数指明要要接受的数据的长度,
Read。返Ml实际接收到的了节数,出错返回-1,遇到文件尾则返回0。
intwrite(intsockfd,char*buff,intnbytes)
Write。有三个参数:•个是套接字描述符,个为指向需要发送的数据的缓冲区,还有一个整数为要写入到文件中的字节个数,
它返回实际写入的字」数,出错返回-10
intsend(intsockfd,char*buff,intnbytes,intflags);
intrecv(intsockfd,char*buff,intnbytes,intflags);
也可以调用send和recv来对套节字进行读写,其调用与基本的read和write系统调用相似,只是多了一个发送方式参数flags,
intsendto(intsockfd,char*buff,intnbytes,intflags,structsockaddr*to,intaddrlen);
intrecvfrom(intsockfd,char*buff,intnbytes,intflags,structsockaddr*from,intaddrlen);
对于使用无连接协议的服务器程序和客户端程序的流程,
客户端程序并不和服务器程序建迂连接,它是通过使用服务器地址作为参数的sendto()系统调用,
发送一个数据报给服务器的。同样,服务器并不接受客户端的连接,而是川recvfrom()调用等待从客户端来的数据。
这些调用与标准的系统调用read()^11write。相似。
这些调用需要附加的参数.Flag参数可以是。或者下列常数:
MSG_OOB接受或发送绑定外的数据
MSG_PEEK监视进入信息
MSG_DONTROUTE绕过路由
intclose(socketfd)
/*退出程序时,应按正常方式关闭套节字号
Socket及协议管理层
include\linux\fs.h
描述:ljsocket相关的文件系统部分结构体
Structinode
structinode{
structIist_headi_hash;
structlist_headUist;
structlist_headi_dentry;
structlist_headi_dirty_buffers;
structlist_headi_dirty_data_buffers;
unsignedlongLino;
atomic_ti_count;
kdev_ti_dev;
umode_ti_mode;
nlink_ti.nlink;
uid_tLuid;
gid_ti_gid;
kdev_ti_rdev;
lofOi_size;
time_ti_atime;
i_mtime;
time_ti_ctime;
unsignedinti_blkbits;
unsignedlongi_blksize;
unsignedlongi_blocks;
unsignedlongi_version;
structsemaphorei_sem;
structsemaphorei_zombie;
structinode_operations*i_op;
structfile_operations*i_fop;/*former->i_op->default_file_ops*/
structsuper_block*i_sb;
wait_queue_head_ti_wait;
structfile_lock*i_flock;
structaddress_space*i_mapping;
structaddress_spacei_data;
structdquot*i_dquot[MAXQUOTAS];
/*Thesethreeshouldprobablybeaunion*/
structlist_headi_devices;
structpipe_inode_info*i_pipe;
structblock_device*i_bdev;
structchar_device*i_cdev;
unsignedlongi_dnotify_mask;/*Directorynotifyevents*/
structdnotify_struct*i_dnotify;/*fordirectorynotifications*/
unsignedlongi_state;
unsignedintijlags;
unsignedchari_sock;
atomic_ti_writecount;
unsignedinti_attr_flags;
_u32Lgeneration;
union{
structminix_inode_infominix__i;
structext2_inode_infoext2_i;
structext3_inode_infoext3_i;
structhpfs_inode_infohpfs_i;
structntfs_inode_infontfs_i;
structmsdos_inode_infomsdos_i;
structumsdos_inode_infbumsdos_i;
structiso_inode_infoisofis_i;
structnfs_inode_infonfs_i;
structsysv_inode_infosysv_i;
structaffs_inode_infoaffs_i;
structufs_inode_infoufs_i;
structefs_inode_infoefs_i;
structromfs_inode_inforomfs_i;
structshmem_inode_infbshmem_i
structcoda_inode_infocoda_i;
structsmb_inode_infosmbfs_i;
structhfs_inode_infohfs_i;
structadfs_inode_infoadfs_i;
structqnx4_inode_infbqnx4_i;
structreiserfs_inode_inforeiserfs_i;
structbfs_inode_infobfs_i;
structudf_inode_infoudU;
structncp_inode_infoncpfs_i;
structproc_inode_infoproc_i;
structsocketsocket_i;
structusbdev_inode_infousbdev_i
structjffis2_inode_infojffs2_i;
void*generic_ip;
}u;
);
structfile
structfile{
structlist_headfjist;
structdentry*f_dentry;
structvfsmount*Cvfsmnt;
structfileoperations*f,op;
atomic_tf_count;
unsignedintLflags;
mode_tf_mode;
lofLtf_pos;
unsignedlongJreada,匚ramax,Jraend,匚ralen,Lrawin;
structfbwn__structf_owner;
unsignedintLuid,fLgid;
intCerror;
unsignedlongCversion;
/*neededforttydriver,andmaybeothers*/
void*private_data;
/*preallocatedhelperkiobuftospeedupO_DIRECT*/
structkiobuf*Mobuf;
longCiobuf_lock;
);
structfile_operations
/*
*NOTE:
*read,write,polkfsync,readv,writevcanbecalled
*withoutthebigkernellockheldinallfilesystems.
*/
structfile_operations{
structmodule"owner;
loff_t(*llseek)(structfile*,loff_t,int);
ssize_t(*read)(structfile*,char*,size_t,lofLt*);
ssize_t(*write)(structfile*,constchar*,size_t,lofO*);
int(*readdir)(structfile*,void*,filldir_t);
unsignedint(*poH)(structfile*,structpoll_table_struct*);
int(*ioctl)(structinode*,structfile*,unsignedint,unsignedlong);
int(*mmap)(structfile*,structvm_area_struct*);
int(*open)(structinode*,structfile*);
int(*flush)(structfile*);
int(*release)(structinode*,structfile*);
int(*fsync)(structfile*,structdentry*,intdatasync);
int(*fasync)(int,structfile*,int);
int(*lock)(structfile*,int,structfile_lock*);
ssize_t(*readv)(structfile*,conststructiovec*,unsignedlong,lofO*);
ssize_t(*writev)(structfile*,conststructiovec*,unsignedlong,lofLt*);
ssize_t(*sendpage)(structfile*,stmctpage*,int,size_t,loffLt*,int);
unsignedlong(*get_unmapped_area)(structfile*,unsignedlong,unsignedlong,unsigned
long,unsignedlong);
);
include\linux\skbuff.h
structsk_buff_head
structsk_buff_head{
/*Thesetwomembersmustbefirst.*/
structsk_buff*next;
structsk_buff*prev;
―u32qlen;
spinlock_tlock;
);
structsk_buff
structsk_buff{
/*Thesetwomembersmustbefirst.*/
structsk_buff*next;/*Nextbufferinlist*/
structsk_buff*prev;/*Previousbufferinlist*/
structsk_bufLhead*list;/*Listweareon*/
structsock*sk;/*Socketweareownedby*/
structtimevalstamp;/*Timewearrived*/
structnet_device*dev;/*Devicewearrivedon/areleavingby*1
/*Transportlayerheader传输层头部结构体*/
union
(
structtcphdr*th;
structudphdr*uh;
structicmphdr*icmph;
structigmphdr*igmph;
structiphdr*ipiph;
structspxhdr*spxh;
unsignedchar*raw;
}h;
/*Networklayerheader网络层头部结构体*/
union
(
structiphdr*iph;
structipv6hdr*ipv6h;
structarphdr*arph;
structipxhdr*ipxh;
unsignedchar*raw;
}nh;
/*Linklayerheader数据链路层头部结构体*/
union
(
structethhdr*ethemet;
unsignedchar*raw;
}mac;
/*该数据报的传输路由信息结构体*/
structdst_entry*dst;
*Thisisthecontrolbuffer.Itisfreetouseforevery
*layer.Pleaseputyourprivatevariablesthere.Ifyou
*wanttokeepthemacrosslayersyouhavetodoaskb_clone()
*first.ThisisownedbywhoeverhastheskbqueuedATM.
*1
/*这个字符数组是一个控制缓冲区,每一层都可以自由使用。
请把你的私有变量存放在这儿。如果你想要这个数组的数据
在每一层都可以使用,那么你必须调用skb_clone()函数。
*/
charcb(48];
unsignedintlen;/*Lengthofactualdata整个数据报的实际长度*/
unsignedintdata_len;
unsignedintcsum;/*Checksum*/
unsignedchar_unused,/*Deadfield,maybereused*/
cloned,/*headmaybecloned(checkrefcnttobesure).*/
pkt_type,/*Packetclass*/
ip_summed;/*DriverfedusanIPchecksum*/
_u32priority;/*Packetqueueingpriority*/
atomic_tusers;/*Usercount-seedatagram.c,tcp.c*/
unsignedshortprotocol;/*Packetprotocolfromdriver.*1
unsignedshortsecurity;/*Securitylevelofpacket列
unsignedinttruesize;/*Buffersize整个缓冲区的大小*/
unsignedchar*head;/*Headofbuffer缓冲区起始地址*/
unsignedchar*data;/*Dataheadpointer协议数据报的起始地址*/
unsignedchar*tail;/*Tailpointer协议数据报尾地址*/
unsignedchar*end;/*Endpointer整个缓冲区的尾地址*/
void(*destructor)(structsk_buff*);/*Destructfunction*/
#ifdefCONFIG_NETFILTER
/*Canbeusedforcommunicationbetweenhooks.*/
unsignedlongnfmark;
/*Cacheinfo*/
_u32nfcache;
/*Associatedconnection,ifany*/
structnfLct_info*nfct;
#ifdefCONFIG_NETFIETER_DEBUG
unsignedintnCdebug;
#endif
#endif/*CONFIGNETFILTER*/
#ifdefined(CONF!G_HIPPI)
union{
—u32ifield;
}private;
#endif
#ifdefCONFIG_NET_SCHED
―u32tc_index;/*trafficcontrolindex*/
#endif
);
include\net\sock.h
structinet_opt
structinet_opt{
intttl;/*TTLsetting*/
inttos;/*TOS*/
unsignedcmsg_flags;
structip_options*opt;
unsignedcharhdrincl;/*Includeheaders?*1
_u8/*MulticastingTTL*/
_u8mc_loop;/*Loopback*/
unsignedrecverr:1,
freebind:1;
_ul6id;1*IDcounterforDFpkts*/
_u8pmtudisc;
intmc_index;/*Multicastdeviceindex*/
_u32mc_addr;
structip_mc_socklist/*Grouparray*/
);
structtcp_opt
描述:Linux_2.4.1网络套接字内部包含了一个由tcp_opt结构
组成的共计420个字节的传输控制块
structtcp_opt{
inttcp_header_len;/*Bytesoftcpheadertosend*/
/*
*Headerpredictionflags
*0x5?10«16+snd_wndinnetbyteorder
*/
,u32pred_flags;
*RFC793variablesbytheirpropernames.Thismeansyoucan
*readthecodeandthespecsidebyside(andlaugh...)
*SeeRFC793andRFC1122.TheRFCwritestheseincapitals.
*/
_u32rcv_nxt;/*Whatwewanttoreceivenext*/
_u32snd_nxt;/*Nextsequencewesend*/
_u32snd_una;/*Firstbytewewantanackfor*/
_u32snd_sml;/*Lastbyteofthemostrecentlytransmittedsmallpacket*/
_u32rcv_tstamp;/*timestampoflastreceivedACK(forkeepalives)*/
_u32Isndtime;/*timestampoflastsentdatapacket(forrestartwindow)*/
/*DelayedACKcontroldata*/
struct{
一u8pending;/*ACKispending*/
一u8quick;/*Schedulednumberofquickacks*/
_u8pingpong;/*Thesessionisinteractive*/
_u8blocked;/*DelayedACKwasblockedbysocketlock*/
_u32ato;/*Predictedtickofsoftclock*/
unsignedlongtimeout;/*Currentlyscheduledtimeout*/
_u32Ircvtime;/*timestampoflastreceiveddatapacket*/
—u16last_seg_size;/*Sizeoflastincomingsegment*/
—ul6rcv_mss;/*MSSusedfordelayedACKdecisions*1
}ack;
/*Datafordirectcopytouser*/
struct{
structskbuffheadprequeue;
structtask__struct*task;
structiovec*iov;
intmemory;
intlen;
}ucopy;
—u32snd_wl1;/*Sequenceforwindowupdate*/
—u32snd_wnd;/*Thewindowweexpecttoreceive*/
―u32max_window;/*Maximalwindoweverseenfrompeer*/
_u32pmtu_cookie;/*Lastpmtuseenbysocket*/
_ul6mss_cache;/*Cachedeffectivemss,notincludingSACKS*/
_u!6mss_clamp;/*Maximalmss,negotiatedatconnectionsetup*/
—ul6ext_header_len;/*Networkprotocoloverhead(IP/IPv6options)*/
_u8ca_state;/*Stateoffast-retransmitmachine*/
一u8retransmits;/*NumberofunrecoveredRTOtimeouts.*/
_u8reordering;/*Packetreorderingmetric.*/
一u8queue_shrunk;/*Writequeuehasbeenshrunkrecently.*/
一u8defer_accept;/*Userwaitsforsomedataafteraccept()*/
/*RTTmeasurement*/
_u8backoff;/*backoff*/
_u32srtt;/*smothedroundtriptime«3*/
_u32mdev;/*mediumdeviation*/
_u32mdev_max;/*maximalmdevforthelastrttperiod*/
_u32rttvar;/*smoothedmdev_max*/
_u32rtt_seq;/*sequencenumbertoupdaterttvar*/
_u32rto;/*retransmittimeout*/
_u32packets_out:/*Packetswhichare"inflight"*/
_u32left_out;/*Packetswhichleavednetwork*/
_u32retrans_out;/*Retransmittedpacketsout*/
*Slowstartandcongestioncontrol(seealsoNagle,andKam&Partridge)
*/
—u32snd_ssthresh;/*Slowstartsizethreshold*/
―u32snd_cwnd;/*Sendingcongestionwindow*/
_ul6snd_cwnd_cnt;/*Linearincreasecounter*/
_ul6snd_cwnd_clamp;/*Donotallowsnd_cwndtogrowabovethis*/
_u32snd_cwnd_used;
―u32snd_cwnd_stamp;
/*Twocommonlyusedtimersinbothsenderandreceiverpaths.*/
unsignedlongtimeout;
structtimer_listretransmit_timer;/*Resend(noack)*/
structtimerjistdelack_timer;/*Ackdelay*/
/*out_of_order_queue用于接收无序得tcp包*/
structsk_bufLheadout_oLorder_queue;/*Outofordersegmentsgohere*/
/*OperationswhichareAF_INET{4,6}specific*/
structtcp_func^af_specific;
structsk_buff*send_head;/*Frontofstufftotransmit*/
structpage*sndmsg_page;/*Cachedpageforsendmsg*/
u32sndmsg_off;/*Cachedoffsetforsendmsg*/
—u32rcv_wnd;/*Currentreceiverwindow*/
—u32rcv_wup;/*rcv_nxtonlastwindowupdatesent*/
—u32write_seq;/*Tail(+1)ofdataheldintcpsendbuffer
_u32pushed_seq;/*Lastpushedseq,requiredtotalktowindows*/
―u32copied_seq;/*Headofyetunreaddata*/
Optionsreceived(usuallyonlastpacket,someonlyonSYNpackets).
*/
chartstamp_ok,/*TIMESTAMPseenonSYNpacket*/
wscale_ok,/*WscaleseenonSYNpacket*/
sack_ok;/*SACKseenonSYNpacket*/
charsaw_tstamp;/*SawTIMESTAMPonlastpacket*/
_u8snd_wscale;/*Windowscalingreceivedfromsender*/
一u8rcv_wscale;/*Windowscalingtosendtoreceiver*/
一u8nonagle;/*DisableNaglealgorithm?*/
_u8keepalive_probes;/*numofallowedkeepaliveprobes*/
PAWS/RTTMdata*/
_u32rcv_tsval;/*Timestampvalue*/
―u32rcv_tsecr;/*Timestampechoreply*/
_u32ts_recent;/*Timestamptoechonext*/
longts_recent_stamp;/*Timewestoredts_recent(foraging)*1
SACKsdata*/
_u16user_mss;/*mssrequestedbyuserinioctl*/
_u8dsack;/*D-SACKisscheduled*/
_u8eff_sacks;/*SizeofSACKarraytosendwithnextpacket*/
structtcp_sack_blockduplicate_sack[1];/*D-SACKblock*/
structtcp_sack_blockselective_acks[4];/*TheSACKSthemselves*/
―u32window_clamp;/*Maximalwindowtoadvertise*/
―u32rcv_ssthresh;/*Currentwindowclamp*/
一u8probes_out;/*unanswered0windowprobes*/
一u8num_sacks;/*NumberofSACKblocks*/
—ul6advmss;/*AdvertisedMSS*/
_u8syn_retries;/*numofallowedsynretries*/
_u8ecn_flags;/*ECNstatusbits.*/
_ul6prior_ssthresh;/*ssthreshsavedatrecoverystart*/
―u32lost_out;/*Lostpackets*/
―u32sacked_out;/*SACK'dpackets*/
―u32fackets_out;/*FACK'dpackets*/
―u32high_seq;/*snd_nxtatonsetofcongestion*/
―u32retrans_stamp;/*Timestampofthelastretransmit,
*alsousedinSYN-SENTtorememberstampof
*thefirstSYN.*/
―u32undo_marker;/*trackingretransstartedhere.*/
intundo_retrans;/*numberofundoableretransmissions.*/
_u32urg_seq;/*Seqofreceivedurgentpointer*/
一u!6urg_data;/*SavedoctetofOOBdataandcontrolflags*/
_u8pending;/*Scheduledtimerevent*/
_u8urg_mode;/*Inurgentmode*/
_u32snd_up;/*Urgentpointer*/
/*Thesyn_wait_lockisnecessaryonlytoavoidtcp_get_infohaving
*tograbthemainlocksockwhilebrowsingthelisteninghash
*(otherwiseit'sdeadlockprone).
*Thislockisacquiredinreadmodeonlyfromtcp_get_info()and
*it'sacquiredinwritemode_only_fromcodethatisactively
*changingthesyn_wait_queue.Allreadersthatareholding
*themastersocklockdon'tneedtograbthislockinreadmode
*tooasthesyn_wait_queuewritesarealwaysprotectedfrom
*themainsocklock.
*/
rwlock_tsyn_wait_lock;
structtcplistenopt*listen_opt;
/*FIFOofestablishedchildren*/
structopen_request^acceptjqueue;
structopenjrequest^acceptjqueueJail;
intwrite_pending;/*Awritetosocketwaitstostart.*1
unsignedintkeepalive_time;/*timebeforekeepalivetakesplace*/
unsignedintkeepalive_intvl;/*timeintervalbetweenkeepaliveprobes*/
intlinger2;
unsignedlonglast_synq_overflow;
);
structsock
structsock{
/*Socketdemultiplexcomparisonsonincomingpackets.*/
_u32daddr;/*ForeignIPv4addr*/
_u32rcv_saddr;/*BoundlocalIPv4addr*/
—u!6dport;/*Destinationport*/
unsignedshortnum;/*Localport*/
intbound_dev_if;/*Bounddeviceindexif!=0*/
/*Mainhashlinkageforvariousprotocollookuptables.*/
structsock*next;
structsock**pprev;
structsock*bind_next;
structsock**bind_pprev;
volatileunsignedcharstate,/*Connectionstate*/
zapped;/*Inax25&ipxmeansnotlinked*/
_ul6sport;/*Sourceport*/
unsignedshortfamily;/*Addressfamily*/
unsignedcharreuse;/*SO_REUSEADDRsetting*/
unsignedcharshutdown;
atomic_trefcnt;/*Referencecount*/
socket_lock_tlock;/*Synchronizer...*/
/*接收缓冲区字节长度*/
intrcvbuf;/*Sizeofreceivebufferinbytes*/
wait_queue_head_t*sleep;/*Sockwaitqueue*/
structdst_entry*dst_cache;/*Destinationcache*/
rwlock_tdst_lock;
/*接收队列已经提交的字节数*/
atomic_trmem_alloc;/*Receivequeuebytescommitted*/
/*接收的数据报的队列号
structsk_buff_headreceive_queue;/*Incomingpackets*/
/*发送队列已提交的字节数*/
atomic_twniem_alloc;/*Transmitqueuebytescommitted*/
/*发送数据报的队列*/
structsk_bufL_headwrile_queue;/*Packetsendingqueue*/
atomic_tomem_alloc;/*nonis"option"or"other"*/
intwmem_queued;/*Persistentqueuesize*/
intfbrward_alloc;/*Spaceallocatedforward.*/
—u32saddr;/*Sendingsource*/
unsignedintallocation;/*Allocationmode*/
/*发送缓冲区的字节长度刃
intsndbuf;/*Sizeofsendbufferinbytes*/
structsock*prev;
/*Notallarevolatile,butsomeare,sowemightaswellsaytheyallare.
*XXXMakethisaflagword-DaveM
*/
volatilechardead,
done,
urginline,
keepopen,
linger,
destroy,
no_check,
broadcast,
bsdism;
unsignedchardebug;
unsignedcharrcvtstamp;
unsignedcharuse_write_queue;
unsignedcharuserlocks;
/*Holeof3bytes.Trytopack.*/
introute_caps;
intproc;
unsignedlonglingertime;
inthashent;
structsock*pair;
/*Thebacklogqueueisspecial,itisalwaysusedwith
*theper-socketspinlockheldandrequireslowlatency
*access.Thereforewespecialcaseit'simplementation.
*/
/*backlog是一个队列,用于将该sock接收到的skb但是不能被及时处理的skb连接成
一个链表。
*/
struct{
structsk_buff*head;
structsk_buff
}backlog;
rwlock_tcallback_lock;
/*Errorqueue,rarelyused.*/
structsk_bufLheaderror_queue;
/*
sk结构的操作指针prot注册为与具体协议相关的
操作函数集structproto,实现了在协议上的抽象。
UDP协议为udp_prot»TCP为tcp_proto
*/
/*指定协议簇的内部的协议处理函数,它是套接口层与传输层之间的一个接口,
提供如bind,accept,close等操作*/
structproto*prot:
#ifdefined(CONFIG_IPV6)IIdefined(CONFIG_IPV6_MODULE)
union{
structipv6_pinfoaf_inet6;
}net_pinfo;
#endif
union{
structtcpoptaf_tcp;/*TCP传输控制结构*/
#ifdefined(CONFIGJNET)IIdefined(CONFIG_INET_MODULE)
structraw_opttp_raw4;
#endif
#ifdefined(CONFIG」PV6)IIdefined(CONFIG_IPV6_MODULE)
structraw6_opttp_raw;
#endif/*CONFIG_IPV6*/
#ifdefined(CONHG_SPX)IIdefined(CONFIG_SPX_MODULE)
structspx_optaCspx;
#endif/*CONFIG_SPX*/
}tp_pinfo;r-传输协议控制块联合结构*1
interr,err_soft;/*Softholdserrorsthatdon't
causefailurebutarethecause
ofapersistentfailurenotjust
,timedout'*/
/*表示当前的监听队列*/
unsignedshortack_backlog;
/*表示最大的监听队列*/
unsignedshortmax_ack_backlog;
u32priority;
unsignedshorttype;
unsignedcharlocalroute;/*Routelocallyonly*/
unsignedcharprotocol;
structucredpeercred;
rcvlowat;
rcvtimeo;
sndtimeo;
#ifdefCONFIG.FILTER
/*SocketFilteringInstructions*/
structsk_filter*filter;
#endif/*CONFIG_FILTER*/
/*Thisiswherealltheprivate(optional)areasthatdon't
*overlapwilleventuallylive.
*/
union{
void*destruct_hook;
structunix_optafLunix;
#ifdefined(CONFIG」NET)IIdefined(CONFIG」NET_MODULE)
structinetoptaMnet;
#endif
#ifdefined(CONFIG_ATALK)IIdefined(CONFIG_ATALK_MODULE)
structatalk_sockaflat;
#endif
#ifdefined(CONFIG_IPX)IIdefined(CONFIG_IPX_MODULE)
structipx_opta匚ipx;
#endif
#ifdefined(CONFIG_DECNET)IIdefined(CONFIG_DECNET_MODULE)
structdn_scpdn;
#endif
#ifdefined(CONFIG_PACKET)IIdefined(CONFIG_PACKET_MODULE)
structpacket_opt*af_packet;
#endif
#ifdefined(CONFIG_X25)IIdefi
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