linux网络源码读取笔记

struct socket {
short            type;
socket_state     state;
long             flags;
struct proto_ops *ops;
void             *data;
struct socket    *conn;
struct socket    *iconn;
struct socket    *next;
struct wait_queue **wait;
struct inode      *inode;
struct   fasync_struct  *fasync_list;
}
struct proto_ops{
int family;
int (*create)(...)
...
}

struct sockaddr {
unsigned  short   sa_family;
char              sa_data[14];
}
struct   linger {
int               l_onoff;
int               l_linger;
}




int  sock_wake_sync(struct socket *sock,int how)

int  sock_register(int family,struct proto_ops *ops)
int  sock_unregister(int family)
struct socket *sock_alloc(void)
void   sock_release(struct socket *sock)


struct old_rtentry{
uunssigned      longrt_genmask;
struct sockaddr rt_dst;
struct sockaddr rt_gateway;
short           rt_flags;  
short           rt_refcnt;
unsigned        longrt_use;
char            *rt_dev;
};

struct rtentry{
unsigned        longrt_hash;
struct   sockaddr  rt_dst;
struct   sockaddr  rt_gateway;
struct   sockaddr  rt_genmask;
short              rt_flags;
short              rt_refcnt;
unsigned           longrt_use;   
struct   ifnet     *rt_ifp;
short              rt_metric;
char               *rt_dev;
unsigned           longrt_mss;
unsigned           longrt_window;
}

网络层对应的普通文件操作函数集合
struct file_operations socket_file_ops={
       sock_lseek,
	   sock_read,
	   sock-write,
	   sock_readdir,
	   sock_select,
	   sock_ioctl,
	   sock_close,
	   sock_fasync
};


int get_fd(struct inode *inode)
{
  .....
  current->files->fd[fd]=file;
  file->f_op=&socket_file_ops;
  
  return (fd);
}

socket 查询函数
inline struct socket*socki_lookup(struct inode*inode)
{
    return &inode->u.socket_i;
}
struct socket *sockfd_lookup(int fd, struct file **pfile)
{
   ...
   inode=file->f_inode;
   return socki_lookup(inode);
}
分配socket结构
struct socket *sock_alloc(void)
{  ...
   inode=get_empty_inode();
   初始化inode...
   sock=inode->u.socket_i;
   初始化sock...
   sock->inode=inode;
   ...
   return sock;
}
   
  
被socket_release调用
socket_release_peer(struct socket *peer)
{
    peer->state=SS_DISCONNECTING;
	wake_up_interruptible(peer->wait);
	sock_wake_async(peer,1);
}

sock_release(struct socket *sock)
{
   。。。
   释放sock的所有的iconn；
   。。。
   sock_ops_release(sock,peersock);
   if（sock->conn）
        sock_release_peer(sock->conn);
	iput(inode);	
}

close函数
sock_close(struct inode*inode,struct file*filp)
{
  ...
  sock=socki_llokup(inode);
  sock_fasync(inode,filp,0);
  sock_release(sock);

}


注意：sock_fasync根据第三个参数决定是申请fasync_struct还是释放


其他函数实现
int sock_lseek(struct inode *inode,struct file *file,off_t offset,int whence)
{
    return (-ESPIPE);(未实现)
}

int sock_read(struct inode*inode ,struct file*file,chaar *ubuf,int size)
{
   ...根据inode查找socket
   ....效验参数
   return(sock->ops-read)(sock,ubuf,size,(flags..))
}
int sock_write(struct inode*inode,struct file *file,char *buf,iont size))
{
   ...根据inode查找socket
   ....效验参数
   return(sock->ops->write)(sock,ubuf,size,(flags..))
}

int sock_readdir(struct inode*inode,struct file *file,char *buf,iont size))
{   
    return (EBADF);未实现
}

int sock_ioctl(struct inode*inode,struct file *file,char *buf,iont size))
{
...根据inode查找socket
   ....效验参数
   return(sock->ops->ioctl)(sock,ubuf,size,(flags..))
}


int sock_select(struct inode*inode,struct file *file,char *buf,iont size))
{
...根据inode查找socket
   ....效验参数
   return(sock->ops->select)(sock,sel_type,wait)
}

分配sock结构
int sock_socket(int family,int type,int protocol)
{
    ...
	根据family匹配pops[i]->family
	找不到返回非法值
	检查type是否合法不合法返回非法值
	分配sock结构
	初始化sock的type与ops
    获取空的fd关联sock
	返回fd
}

int sock_socketpair(int family,int type,int protocol,unsigned long usockvec[2])
{
  ...
  fd1=soco_socket(...)
  判断fd1合法
  sock1=sockfd_lookup(fd1,NULL);
  检查sock->ops->socketpair是否存在不存在返回非法值
  同样方法获取sock2
  sock1->conn=sock2
  sock2->conn=sock1
  sock1->state=SS_CONNECTED
  sock2->state=SS_CONNECTED
  赋值给usocjvew
  返回0
}


int sock_bind(int fd,struct sockaddr *umyaddr,int addrlen)
{
    参数检查
	sock=sockfd_lookup(fd,NULL);
	读取用户态地址
	i=sock->ops->bind(sock,(struct address*)umyaddr,addrlen);
	判断返回
}

int  sock_listen(int fd,int backlog)
{
    参数检查
	sock=sockfd_lookup(fd,NULL);
	判断sock->state是否为SS_UNCONNECTED不是即返回
	根据是否存在sock->ops->listen决定是否调用sock->ops->listen(sock,backlog);
	sock->flags|=SS_ACCEPTCON;
	返回0
}

int  sock_accept（int fd,struct sockaddr *upeer_sockaddr,int upeer_addrlen）
{
     参数检查
	 sock=sockfd_lookup(fd,&file);
	 判断sock->state是否等于SS_UNCONNECTED（要求等于）
	 判断sock->flags是否包含SO_ACCEPTCON（必须包含）
	 分配newsock=sock_alloc();
	 newsock->type=sock->type;
	 newsock->ops=sock->ops;ervaddr,
	 调用i=newsock->ops->accept(sock,newsock,file->f_flags);
	 判断返回值int 
	 fd=get_fd(SOCK_INODE(NEWSOCK))；
	 如果upeer_sockaddr不为空调用newsock->ops->getname)获取对端地址信息返回用户空间
	 return  fd;
}


int  sock_connect(int fd, struct sockaddr*uservaddr,int addrlen)
{
    参数检查
	sock=sockfd_lookup(fd,&file);
	从用户态读取地址
	判断当前sock->state
	如果是SS_UNCONNEECTED
	break;
	如果是SS_CONNECTED
	{ 
	      判断sock->type==SOCK_DGRAM)
		     返回错误值
		  否则break;
		  
	}
	如果是SS_CONNECTING
	      break;
    default
	      返回非法值
	调用i=sock->ops->connect(sock,(struct sockaddr*)address,addrlen,file->f_flags)；
	    return i;
	return 0;
}


获取本端地址信息（IP and port）
int  sock_getsockname(int fd, struct sockaddr *uservaddr,int uservaddrlen)
{
   参数检查
   sock=sockfd_lookup（fd,NULL）;
   sock->ops->getname(sock,(struct sockaddr*)address,&len,0);
   赋值到用户态
}


获取对端地址信息
int sock_getpeername(int fd, struct sockaddr *uservaddr,int uservaddrlen
{
   参数检查
   sock=sockfd_lookup（fd,NULL）;
   sock->ops->getname(sock,(struct sockaddr*)address,&len,1);//最后一位决定获取对端还是本端
   赋值到用户态
}

int sock_send(int fd,void*buff,int len,unsigned  flags)
{
    参数检查
	sock=sockfd_lookup(fd,NULL);
	return sock->ops->send(sock,buff,len,(file->f_flags)&O_NOBLOCK)，flags);
}

int sock_sendto(int fd,void*buff,int len,unsigned  flags,struct sockaddr &addr,int addrlen)
{
   参数检查
   sock=sockfd_lookup（fd,NULL);
   读取用户态地址
   return sock->ops->sendto(sock,buff,len,(file->f_flags)&O_NOBLOCK)，flags,sockaddr,addrlen);
  
}

int  sock_recv(int fd,void*buff，int len,unsigned flags)
{
     参数检查
	 sock=sockfd_lookup（fd,NULL);
	 return sock->ops->recv(sock,buff,len,(file->f_flags)&O_NOBLOCK)，flags);
}

int sock_recvfrom(int fd,void*buff,int len,unsigned  flags,struct sockaddr &addr,int addrlen)
{
   参数检查
   sock=sockfd_lookup（fd,NULL);
   len=sock->ops->recvfrom((sock,buff,len,(file->f_flags)&O_NOBLOCK)，flags,sockaddr,addrlen);
   若addr不为空将地址赋值给用户态
   返回len
  
}



int  sock_setsockopt(int fd,int level,int optname,char *optval，int optlen)
{
   参数检查
   sock=sockfd_lookup（fd,NULL);
   return sock->ops->setsockopt(sock,level,optname,optval,optlen);
}

int  sock_getsockopt(int fd,int level,int optname,char *optval,int *optlen)
{
   参数检查
   sock=sockfd_lookup（fd,NULL);
   return sock->ops->getsockopt(sock,leveloptname,optval.optlen)；
}

int  sock_shutdown(int fd,int how)
{
   参数检查
   sock=sockfd_lookup(fd,NULL);
   return sock->ops->shutdown(sock,how);  
}

int sock_fcntl(struct file*filp,unsigned int cmd,unsigned long arg)
{
   sock=sockfd_lookup（filp->i_inode);
   return sock->ops->fcntl(sock,cmd,arg)；
}


sys_socketcall(int call, unsigned long *args)
{
   根据call分发调用对应函数
   
}
注册协议
int sock_register(int family,struct proto_ops *ops)
{
    遍历pops数组找个空闲位置插入ops
	pops[i]=ops;
	pops[i]->family=family；
	return i;
}

int  sock_unregister(int family)
{
   查找pops[i]->family=family；
   pops[i]=NULL;
   return i;
       
}

获取当前使用的套接字总数
sock_get_info(char *buff,char **start,off_t offset,int length)
{
   ....
   socket_in_uses计数
   ...
}



struct sock {

struct options *opt;//IP选项缓存于此处
//当前写缓冲区大小
volatile unsigned long wmem_alloc;
//当前读缓冲区大小
volitile  unsigned long rmem_alloc;
//写序列
unsigned long write_seq;
//已发送序列
unsigned long sent_seq;
//已确认序列
unsigned long acked_seq;
//已接收单未读取的数据第一个字节
unsigned long copied_seq;
//表示远端对本地已经应答acked的序列号
unsigned long rcv_ack_seq;
//窗口的大小
unsigned long window_seq;
//当接收到对方fin数据包的最后一个字节+1
unsigned long fin_seq;
//紧急数据最大序列号
unsigned long urg_seq;
//紧急数据
unsigned long urg_data;

volatile char inuse，//inuse=1表示其他进程在使用sock
              dead,   //dead=1表示此sock已经被释放
              urginline，//=1表示紧急数据当做普通数据处理
			  intr,
			  blog,  //=1 表示sock处于节制状态，接受的数据包都被丢弃
			  done,
			  reuse,
			  keepopen,//=1表示使用保活定时器
			  linger,//=1表示在关闭套接字时需要等待
			           一段时间以确认其关闭
			  delay_acks,//=1表示延迟应答，可一次对多个数据包应答
			  destroy, //=1表示该sock等待销毁
			  ack_timed,
			  no_check,
			  zapped,//当本地接受到远端发送的复位数据包置1
			  broadcast,
			  bonagle；//=1表示不使用nagle算法
			  
unsigned long lingertime;//表示等待关闭的时间
int proc;//该sock结构所属进程的进程号
struct sock *next;
struct sock *prev;
struct sock *pair;
//send_head、send_tail用于tcp协议重发队列
struct sk_buff *volitile send_head;
struct sk_buff *volitile send_tail;
//back_log为接收的数据包缓存队列
struct sk_buff_head back_log;
//partial为用于创建最大长度待发送数据包（聚合数据包）
struct sk_buff *partial
//partial_timer用于按时发送partial指向的数据包
struct time_list partial_timer；
long  retransmits;//表示重发次数
/*write_queue表示待发送数据包，
struct sk_buff *receive_queue表示待被应用程序读取的数据包队列
   从back_log中取下放在此队列供应用程序读取
*/   
struct sk_buff_head write_queue,receive_queue;
struct proto *prot;//指向传输层处理函数集
struct wait_queue **sleep;//进程等待队列
unsigned long daddr;//sock结构所代表套接字的远端地址
unsigned long  saddr;//本地地址
unsigned short max_unacked;//最大未处理请求连接数
unsigned short window;//远端窗口大小
unsigned short bytes_rcv;//已接收未应答字节总数
unsigned short mtu;//协商的mtu大小
volatile unsigned short mss;//mss=mtu-ip以及tcp首部长度
volatile unsigned usre_mss;//用户指定mss
volatile unsigned short max_window;//最大窗口大小
unsigned long window_clamp;//窗口大小钳制值

unsigned shrot  num;//本地端口号

volatile unsigned short cong_window;
volatile unsigned short cong_count;
volatile unsigned short ssthresh;

//本地已发送但是未得到应答的数据包数目
volatile unsigned short packets_out;

volatile unsigned short shutdown;//本地关闭标志位

volatile unsigned long rtt;//RTTS
volatile unsigned long mdev;//RTTD绝对偏差
volatile unsigned long  rto;//算法算出延迟时间
volatile   unsigned long backoff;//退避算法度量值
volatile short err;//错误标志值
unsigned char protocol;//传输层协议值
volatile unsigned char state;//套接字状态值
volatile unsigned char ack_backlog;//缓存未应答数据包个数
volatile char max_ack_backlog;//缓存未应答的数据包最大的个数
unsigned char priority;//该套接字优先级
unsigned char  debug;

unsigned short  rcvbuf;//最大接收缓冲区大小
unsigned short  sndbuf;//最大发送缓冲区大小
unsigned short  type;//套接字类型

unsigned char  localroute；//表示只是用本地路由

int ip_ttl;//ttl值
int ip_tos；//TOS值
//用于缓存tcp首部，在tcp中创建发送一个数据包时可利用此字段快速创建
struct tcphdr dummy_th;
struct time_list keepalive_timer;//保活定时器
struct time_list restransmit_timer；//重发定时器，用于数据包重发
struct time_list ack_timer；//设置定时器发送应答数据包

int  ip_xmit_timeout；//用于定时器超时原因
struct time_list timer;//

struct timeval stamp;//时间戳

struct socket *socket;

void (*state_change)(struct sock*sk);
void (*data_ready)(struct sock*sk,int bytes);
void (*write_sapce)(struct sock *sk);
void (*error_report)(struct sock *sk);
}

struct proto {
   ...
    操作函数指针
    ...
unsigned short max_header;
unsigned long retransmits;
//num%256插入对应的sock_array链表
struct sock sock_array[SOCK_ARRAY_SIZE];

char  name[80];
int   inuse，highestinuse;
}





检测端口号是否被使用
int sk_inuse(struct proto *prot,int num)
{
   ...
   sk=prot->sock_array[num&(SOCK_ARRAY_SIZE-1)]；
    if（sk->num==num）
	   return 1;
	 
    遍历完了查不到	 
	return 0;
   
}



分配端口号
get_new_socknum(struct proto *prot,unsigned short base)
{
    ...
	根据base查找端口号是否未使用若未使用直接返回
	否则查找一个未使用
	确认是否在使用中
	返回端口号
}



//将一个确定端口号的sock加入sock_array[]
数组
put_sock(unsigned short num,struct sock *sk)
{
   。。。
   sk->proto->inuse+=1;
   ....
   sk->next=sk->prot->sock_array[num];
   sk->prot->sock_array[num]=sk;
   ...
   
}

//从sock_array中删除指定的sock
remove_sock(struct sock *sk)
{
   ...
    sk->prot->inuse-=1;
	....
	sk2->next=sk->next；
	...
}


//销毁一个连接包括sock
destroy_sock(struct sock*sk)
{
    ...
	sk->inuse=1;
	..检查sk->dead
	remove_sock（sk）;
	delete_timer(sk);
	del_timer(&sk->retransmits_timer)；
	释放partial数据包
	清空写队列clean  sk->write_queue
	判断sk->dead标志
    清空待读取的数据包队列sk->receive_queue
    判断是否是监听套接字若是skb->sk->dead=1;skb->sk->prot->close(skb->sk,0)
    清空重发对列 sk->send_head
    清空数据包缓存队列sk->back_log
    判断sk->pair 若存在则sk->pair->dead=1;sk->pair->prot->close(sk->pair,0);sk->pair=NULL;
    若sk->dead标志设置且sk->rmem_allpc==0&&sk->wmem_alloc==0,释放sk
    否则设置个定时器等其他进程释放缓冲区后释放sk	
	 
}

			

int   inet_fcntl(struct socket *sock,unsigned int cmd,unsigned long arg)
{
   ....
   sk=(struct sock*)sock->data;
   //仅仅提供设置和读取套接字属主的功能
   ...

}			
			  
int  inet_setsockopt(struct socket *sock,int level,int optname,char *optval,int optlen)
{
    ...
	sk=(struct sock*)sock->data;
	...
	判断sk->prot->setsockopt是否存在存在则调用（sk,level,optname,optval,optlen）;
	否则返回EOPNOTSUPP

}

int inet_getsockopt(struct socket *sock,int level,int optname,char *optval,int optlen)
{
    ...
	sk=(struct sock*)sock->data;
	...
	判断sk->prot->getsockopt是否存在存在则调用（sk,level,optname,optval,optlen）;
	否则返回EOPNOTSUPP

}


int inet_autobind(struct sock *sk)
{
    ...
	if(sk->num==0)
	 sk->num=get_new_socknum(sk->prot,0);
	 如果分配失败返回EAGAIN错误
	 put_sock(sk->num,sk);
	 sk->dummy_th.source=ntohs(sk->num)；
	 return 0;
}


int inet_listen(struct socket *sock,int backlog)
{
    struct sock *sk=(struct sock *)sock->data;
	if(inet_autobind(sk)!=0)
	   return -EAGAIN;
	判断参数合法
	sk->max_ack_backlog=backlog；
	如果sk->state！=TCP_LISTEN
	   sk->ack_backlog=0;
	   sk->state=TCP_LISTEN;
	return 0;

}


//事件通知回调函数
void def_callback1(struct sock *sk)
{
	 if(!sk->dead)
	   wake_up_interruptible(sk->sleep)；//唤醒睡眠在sk->sleep上的进程
      	 
}


void def_callback2(struct sock *sk,int len)
{
      if(!sk->dead)
	  {
	      wake_up_interruptible(sk->sleep);
		  sock_wake_async(sk->socket,1);//注意传参不同
	  }
}


void def_callback3(struct sock *sk)
{
       if(!sk->dead)
	   {
	      wake_up_interruptible(sk->sleep);
		  sock_wake_async(sk->socket,2);
	   }
}

//sock创建以及初始化
int inet_create(struct socket *sock,int protocol)
{
     。。。
	 分配个sk
	 。。。判断
	 初始化sk->num=0、sk->reuse=0;
	 根据sock->type判断protocol是否为对应的IPPROTO_TCP\IPPROTO_UDP\IPPROTO_RAW\IPPROTO_PACKET;
	 初始化sk->proto为对应的tcp_proto\udp_proto\raw_proto\packet_proto
	 tcp_proto:sk->no_check=TCP_NO_CHECK；
	 udp_proto:sk->no_check=UDP_NO_CHECK;
     raw_proto:sk->no_check=0;sk->reuse=1;sk->num=protocol;
     pckets_proto:sk->reuse=1;sk->no_check=0;sk->num=protocol;
	 
	 sk->sock=sock;
	 //初始化sk->nonagle=1\0;
	 sk->type=sock->type;
	 sk->stamp.tv_sec=0;
	 sk->protocol=protocol;
	 //初始化sk_wmem\rmerm_alloc=0;
	 //初始化sk->sndbuf\rcvbuf=SK_WMEME_MAX\SK_RMEM_MAX;
	 sk->[air=NULL;
	 sk->opt=NULL;
	 sk->write_seq=0;
	 sk->acked_seq=0;
	 sk->copied_seq=0;
	 sk->fin_seq=0;
	 sk->urg_seq=0;
	 sk->urg_data=0;
	 sk->proc=0;
	 sk->rtt=0;
	 sk->rto=TCP_TIMEOUT_INET;
	 sk->mdev=0;
	 sk->backoff=0;
	 sk->packets_out=0;
	 sk->cong_window=1;
	 sk->cong_count=0;
	 sk->ssthresh=0;
	 sk->max_window=0;
	 sk->urgline=0;
	 sk->intr=0;
	 sk->linger=0;
	 sk->destroy=0;
	 sk->priority=1;
	 sk->shutdown=0;
	 sk->keepopen=0;
	 sk->zapped=0;
	 sk->done=0;
	 sk->ack_backlog=0;
	 sk->window=0;
	 sk->bytes=0;
	 sk->state=TCP_CLOSE;
	 sk->dead=0;
	 sk->ack_timed=0;
	 sk->partial=NULL;
	 sk->user_mss=0;
	 sk->debug=0;
	 sk->unacked=2048;
	 sk->max_ack_backoff=0;
	 sk->inuse=0;
	 sk->delay_acks=0
	 skb_queue_head_init(&sk->write_queue);
	 skb_queue_head_init(&sk->receive_queue);
	 sk->mtu=576;
	 sk->prot=prot;//前面已初始化
	 sk->sleep=sock->wait;
	 sk->daddr=0;
	 sk->saddr=0;
	 sk->err=0;
	 sk->next=NULL;
	 sk->pair=NULL;
	 sk->sendtail=NULL;
	 sk->send_head=NULL;
	 sk->timeout=0;
	 sk->broadcast=0;
	 sk->localroute=0;
	 init_timer(&sk->timer);
	 init_timer(&sk->restransmit_time);
	 sk->timer.data=(unsigned long )sk;
	 sk->timer.funcation=&net_timer;
	 skb_queue_head_init(&sk->back_log);
	 sk->blog=0;
	 sock->data=(void*)sk;
	 
	 //tcp初始化
	 sk->dummy_th.doff=sizeof(sk->dummy_th)/4;
	 sk->dummy_th.res1=0;
	 sk->dummy_th.res2=0;
	 sk->dummy_th.urg_prt=0;
	 sk->dummy_th.fin=0;
	 sk->dummy_th.syn=0;
	 sk->dummy_th.rst=0;
	 sk->dummy_th.psh=0;
	 sk->dummy_th.ack=0;
	 sk->dummy_th.urg=0;
	 sk->dummy_th.dest=0;
	 sk->ip_tos=0;
	 sk->ip_ttl=64;
	 //多播初始化
	 sk->ip_mc_loop=1;
	 sk->ip_mc_ttl=1;
	 sk->ipmc_name=0;
	 sk->ip_mc_list=NULL;
	 //初始化回调函数
	 sk->state_change=def_callback1;
	 sk->data_ready=def_callback2;
	 sk->write_sapce=def_callback3;
	 sk->error_report=def_callback1;
	 //如果定义了num
	 put_sock(sk->num,sk);
	 sk->dummy_th.source=ntos(sk->num);
	 //若定义了sk->prot->init
	 则调用sk->prot->init(sk);
	 return 0;
	}
	 
}


//赋值sk
int inet_dup(struct socket *newsock,struct socket*oldsock)
{
   rteturn (inet_create(newsock,((struct sock*)oldsock->data)->protocol));
}

//套接字状态检测

inline int closing(struct sock *sk)
{
  判断sk->state是否为TCP_FIN_WAITE1\
  TCP_CLOSING;
  TCP_LAST_ACK;
  也就是还有数据没有发送完
  return 1;
  否则return 0;
}

//套接字释放
int inet_release(struct socket*sock,struct socket*peer)
{
    sk=(struct sock*)socket->data;
	sk->state_change(sk);
	//判断sk->lingertime是否为0
	若为0则sk->prot->close(sk,0);
	否则sk->prot_close(sk,0);并将当前进程处于睡眠中时间为lingertime；
	while(closing(sk)&&timeout>0)
	 可中断睡眠
	 自然超时
	 sk->dead=1;
	 sk->inuse=1;
	 release_sock(sk);
	 sock->data=NULL;
	 sk->socket=NULL;
	 return(0);
	 	 
}

int inet_bind(struct socket*sock,struct sockaddr*uaddr,int addr_len)
{
    sk=(struct sock*)sock_data;
	//判断ssk->state是否为TCP_CLOSE;
	若sock->type不为SOCK_RAW;
	判定传入端口是否为0 为0 自动分配一个snum；
	检查地址是否为本地网卡地址且不是多播地址则出错
	进行端口检查以及地址检查
	然后
	//以下包括raw套接字
	remove_sock(sk);
	put_sock(snum,sk);
	sk->dummy_th.source=ntos(sk->num);
	sk->daddr=0;
	sk->dummy_th.dest=0;
	
	return 0;
	}
	
	//获取错误
	int inet_error(struct sock *sk)
	{
	   err=sk->err;
	   sk->err=0;
	   return -err;
	}
	
	enum{
	TCP_ESTABLISHED=1;
	TCP_SYN_SENT,
	TCP_SYN_RECV,
	TCP_FIN_WAIT1,
	TCP_FIN_WAIT2,
	TCP_TIME_WAIT,
	TCP_CLOSE,
	TCP_CLOSE_WAIT,
	TCP_LAST_ACK,
	TCP_LISTEN,
	TCP_CLOSING};
	
	
	int inet_connect(struct socket *sock,struct sockaddr *uaddr,int addr_len,int flags)
	{
	   sk=(struct sock *)sock->data;
	   if(sock->state==SS_CONNECTING&&tcp_connected(sk->state))
	       直接将sock->state==SS_CONNECTED;
		   return 0;
	   if(sock->state==SS_CONNECTING&&SK->PROTOCOL==IPPROTO_TCP&&(flags&O_NONBLOCK))
           return -EALREADY;//正在连接非阻塞直接返回
	   if(sock->state!=SS_CONNECTING)
           inet_autobind(sk);//绑定sk
		   sk->prot->connect(sk,(struct sockaddr_in*)uaddr,addr_len)//调用prot->connect
			//将sock->state==SS_CONNECTING
        
		if(sk->state>TCP_FIN_WAIT2&&sock->state==SS_CONNECTING)
             //将sock->state==SS_UNCONNECTED;
             err=sk->err//获取错误
             return err;			 
        if(sk->state!=TCP_ESTABLISHED&&(flags&O_NONBLOCK))
           return -EINPROGRESS;//返回进行中		
		while(sk->state==TCP_SYN_SENT||sk->state==TCP_SYN_RECV)
        {
		     可中断睡眠在sk->sleep上
			 //下面为唤醒
			 if(sk->err&&sk->0protocol==IPPROTO_TCP)
			      sock->state==SS_UNCONNECTED
				  err=-sk->err;
				  return err;
		}  
		//这一步说明是握手完成
		sock->state==SS_CONNECTED;
		//排除sk->state非TCP_ESTABLEISHED异常情况
		if(sk->state!=TCP_ESTABLISHED&&sk->err)
		   sock->state==SS_UNCONNECTED;
		   err=-sk->err;
		   return err;
		return 0;   
		
}
2.6不支持inet_socketpair

accept的inet层实现
int inet_accept(struct socket &sock,struct socket*newsock,int flags)
{
    sk1=(struct sock*)sock->data;
	//判断newsock的sk存在则释放
	if(newsock->data)
	{
	   sk=(struct sock*)newsock->data;
	   newsock->data=NULL;
	   sk->dead=1;
	   destroy_sock(sk);
	}
    //判断sk1->prot->accept是否存在不存咋则返回
	if(sk1->pair!=NULL)
	  sk2=sk1->pair;
	  sk1->pair=NULL;
	else
	   sk2=-sk1->prot->accept(sk1,flags);
	   if(sk2==NULL)
	      //出错
		  err=sk1->err;
		  sk1->err=0;
		  return -err;
		
	}
	//没有出错
	newsock0->data=(void*)sk2;
	//初始化新的sk2的值
	sk2->sleep=newsock->wait;
	sk2->socket=newsock;
	newsock->conn=NULL;
    //如果非阻塞直接返回0
	if(flags&O_NONBLOCK)
	   return 0;
	while(sk2->state==TCP_SYN_RECV)
    {
	    可中断睡眠在sk2->sleep注意是新的sk2 
	}	
	if(sk2->state!=TCP_ESTABLISHED&&sk2->err>0)
	{
	   err=-sk2->err;
	   sk2->err=0;
	   sk2->dead=1;
	   destroy_sock(sk2);
	   newsock->data=NULL;
	   return err;
	}
	newsock->state==SS_CONNECTED;
    return 0;	
	
}

//用于获取本段和对端的地址
int inet_getname(struct socket *sock,struct sockaddr*uaddr,int uaddr_len,int peer)
{
    sin=(struct sockaddr_in*)uaddr;
	sin->sin_family=AF_INET;
	sk=(struct sock*)sock->data;
	if(peer)
	{
	   //获取对端地址信息
	   //判定是否是连接状态否则返回
	   if(!tcp_connected(sk->state))
	      return -ENOTCONN;
		sin->sin_port=sk->dummy_th.dest;
		sin->sin_addr.s_addr=sk->daddr;
	}
	else
	{
	 //获取本端地址信息
	 sin->sin_port=sk->dummy_th.source;
	 if(sk->saddr==0)
	   sin->sin_addr.s_addr=ip_my_addr();
	 else
	   sin->sin_addr.s_addr=sk->saddr;   
	}
	 *uaddr_len=sizeof(*sin);
	 return 0;
	
}

//获取本机源ip地址
unsigned long ip_my_addr(void)
{ 
   //遍历所有设备
   for(dev=dev_base;devf!=NULL;dev=dev->next)
       if(dev->flags&IFF_LOOPBACK)
	       return(dev->pa_addr);
	return 0;
}

recvfrom调用

int inet_recvfrom（struct socket*sock,void*buf,int size,int noblock,
   unsigned flags,struct sockaddr*sin,int *addr_len ）
   {
      sk=(struct sock*)sock->data;
	  //判定sk->prot->recvfrom是否存在不存在则返回
      //判断sk->err若不为0则inet_error(sk);
      inet_autobind(sk);
      return(sk->prot->recvfrom(sk,(unsigned char*)ubuf,size,boblock,flags,
	         (struct sockaddr_in*)sin,addr_len));	  
   }
   
recv调用
int inet_recv(struct socket*sock,void*ubuf,int size,int noblock,unsigned falgs)
{
   return inet_recvfrom(sock,ufbu,size,noblock,falgs,NULL,NULL);
}


read调用

int inet_read(struct sockedt*sock,char*ubuf,int size,int noblock)
{
   sk=(struct sock*)sock->data;
   //检查sk->err;
   inet_autobind(sk);
   return sk->prot_read(sk,(unsigned char*)ubuf,size,noblock,0);
}
  
int inet_send(struct socket*sock,void*ubuf，int size,int noblock,unsigned falgs)
{
   sk=(struct sock*)sock->data;
   if(sk->shutdown&SEND_SHUTDOWN)
   {
      SEND_SIG(sigpipe,curreent,1);
	  return (-EPIPE);	  
   }
    //判定sk->err
	inet_autobind(sk);
	return sk->prot->write(sk,(unsigned cahr*)ubuf,size,noblock,flags);	
}
int inet_write(struct socket*sock,char *ubuf,int size,int noblock)
{
   return inet_send(sock,ubuf,size,noblock,0);
}

int inet_sendto(struct socket*sock，void*ubuf,int szie,
  int noblock,unsigned flags,struct sockaddr*sin,int addr_len)
  {
      sk=(struct sock*)sock->data;
	  if(sk->shutdown&SEND_SHUTDOWN)
      {
        SEND_SIG(sigpipe,curreent,1);
	    return (-EPIPE);	  
      }
	  //判定prot->sendto是否存在
	  //判定sk->err
	  inet_autobind(sk)
	  return sk->prot_sendto(sk,(unsigned char *)ubuf,size,noblock,flags
	       (struct sockaddr_in*)sin,addr_len);
 }
int inet_shutdown(struct socket*sock,int how)
{
   //how表示半关闭还是全关闭
   sk=(struct sock*)sock->data;
   how++;
   如果sock->state==SS_CONNECTING&&sk->state==TCP_ESTABLISHED
     sock->state==SS_CONNECTED;
   检查tcp_connected(sk->state)若不是连接状态
      return -ENOTCONN；
	sk->shutdown!=how;
	如果sk->prot->shutdown存在
	则sk->prot->shutdown(sk,how);
	return 0;
	
}
  
int inet_select(struct socket *sock,int sel_type,select_table*wait)
{
   sk=(struct sock*)sock->data;
   //判定select存在
   return sk->prot->select(sk,sel_type,wait);   
} 
int inet_ioctl(...)
{
   ...
   
}

struct sock*get_sock(struct proto *prot,unsigned short num,unsigned long raddr,unsigned short rnum,unsigned long laddr)
{
   。。。
   从proto中读取sock检索匹配的sock；
   。。。
}

struct sock* get_sock_raw(struct sock*sk,unsigned short num,unsigned long raddr,unsigned long laddr)
{
   。。。
   遍历sk->next找到匹配的sk返回。
   。。。
   
}