3. 

        <meter id="pryje"><nav id="pryje"><delect id="pryje"></delect></nav></meter>
          <label id="pryje"></label>
          
	
	
          
		
			
		
          
    
    	
          
  		
          
		    
          
		      
		      
		      
		    
          
  		
          
  		
          
	
          


	


          
		
          
		            
            
        		
          
		
          







          


          
	
	
          
		
          新聞中心
          
	
          
	
          
	
          EEPW首頁 
	 > 嵌入式系統(tǒng) > 設(shè)計(jì)應(yīng)用 > linux內(nèi)核中的文件描述符(二)--socket和文件描述符
          
    
          

          

          


	
	
	

          
	
          
		
          
			
          linux內(nèi)核中的文件描述符(二)--socket和文件描述符
          
						
          
				作者：
				時(shí)間：2016-11-22
				來源：網(wǎng)絡(luò)
				
				
				
				
				收藏
			
          

			
          
				
				
			
          

			
          
			
			
          
			
			
          
				
				
			
          
                
			Kernel version：2.6.14
          CPU architecture：ARM920T
          本文引用地址：http://www.ex-cimer.com/article/201611/319998.htm
          Author：ce123(http://blog.csdn.net/ce123)
          socket和文件系統(tǒng)緊密相關(guān)，我們可以通過文件系統(tǒng)的open、read、write和close等操作socket。下面是一個(gè)簡單的例子。
          [plain]view plaincopy
          print?
          1. /****************************************************************************/
          2. /*簡介：TCPServer示例*/
          3. /****************************************************************************/
          4. #include
          5. #include
          6. #include
          7. #include
          8. #include
          9. #include
          10. #include
          11. #include
          12. intmain(intargc,char*argv[])
          13. {
          14. intsockfd,new_fd;
          15. structsockaddr_inserver_addr;
          16. structsockaddr_inclient_addr;
          17. intsin_size,portnumber;
          18. constcharhello[]="Hellon";
          20. if(argc!=2)
          21. {
          22. fprintf(stderr,"Usage:%sportnumberan",argv[0]);
          23. exit(1);
          24. }
          25. if((portnumber=atoi(argv[1]))<0)
          26. {
          27. fprintf(stderr,"Usage:%sportnumberan",argv[0]);
          28. exit(1);
          29. }
          30. /*服務(wù)器端開始建立socket描述符*/
          31. if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
          32. {
          33. fprintf(stderr,"Socketerror:%sna",strerror(errno));
          34. exit(1);
          35. }
          36. /*服務(wù)器端填充sockaddr結(jié)構(gòu)*/
          37. bzero(&server_addr,sizeof(structsockaddr_in));
          38. server_addr.sin_family=AF_INET;
          39. server_addr.sin_addr.s_addr=htonl(INADDR_ANY);
          40. server_addr.sin_port=htons(portnumber);
          41. /*捆綁sockfd描述符*/
          42. if(bind(sockfd,(structsockaddr*)(&server_addr),sizeof(structsockaddr))==
          43. -1)
          44. {
          45. fprintf(stderr,"Binderror:%sna",strerror(errno));
          46. exit(1);
          47. }
          48. /*監(jiān)聽sockfd描述符*/
          49. if(listen(sockfd,5)==-1)
          50. {
          51. fprintf(stderr,"Listenerror:%sna",strerror(errno));
          52. exit(1);
          53. }
          54. while(1)
          55. {
          56. /*服務(wù)器阻塞,直到客戶程序建立連接*/
          57. sin_size=sizeof(structsockaddr_in);
          58. if((new_fd=accept(sockfd,(structsockaddr*)(&client_addr),&sin_size))==-1)
          59. {
          60. fprintf(stderr,"Accepterror:%sna",strerror(errno));
          61. exit(1);
          62. }
          63. fprintf(stderr,"Servergetconnectionfrom%sn",
          64. inet_ntoa(client_addr.sin_addr));
          65. if(write(new_fd,hello,strlen(hello))==-1)
          66. {
          67. fprintf(stderr,"WriteError:%sn",strerror(errno));
          68. exit(1);
          69. }
          70. /*這個(gè)通訊已經(jīng)結(jié)束*/
          71. close(new_fd);
          72. /*循環(huán)下一個(gè)*/
          73. }
          74. close(sockfd);
          75. exit(0);
          76. }
          下圖說明了socket和fd是怎樣聯(lián)系起來的。
          下面通過來具體分析一下。sys_socket是socket相關(guān)函數(shù)的總?cè)肟凇?/p>
          [plain]view plaincopy
          print?
          1. net/socket.c
          2. /*
          3. *Systemcallvectors.
          4. *
          5. *Argumentcheckingcleanedup.Saved20%insize.
          6. *Thisfunctiondoesntneedtosetthekernellockbecause
          7. *itissetbythecallees.
          8. */
          10. asmlinkagelongsys_socketcall(intcall,unsignedlong__user*args)
          11. {
          12. unsignedlonga[6];
          13. unsignedlonga0,a1;
          14. interr;
          16. if(call<1||call>SYS_RECVMSG)
          17. return-EINVAL;
          19. /*copy_from_usershouldbeSMPsafe.*/
          20. if(copy_from_user(a,args,nargs[call]))
          21. return-EFAULT;
          23. err=audit_socketcall(nargs[call]/sizeof(unsignedlong),a);
          24. if(err)
          25. returnerr;
          27. a0=a[0];
          28. a1=a[1];
          30. switch(call)
          31. {
          32. caseSYS_SOCKET:
          33. err=sys_socket(a0,a1,a[2]);
          34. break;
          35. caseSYS_BIND:
          36. err=sys_bind(a0,(structsockaddr__user*)a1,a[2]);
          37. break;
          38. caseSYS_CONNECT:
          39. err=sys_connect(a0,(structsockaddr__user*)a1,a[2]);
          40. break;
          41. caseSYS_LISTEN:
          42. err=sys_listen(a0,a1);
          43. break;
          44. caseSYS_ACCEPT:
          45. err=sys_accept(a0,(structsockaddr__user*)a1,(int__user*)a[2]);
          46. break;
          47. caseSYS_GETSOCKNAME:
          48. err=sys_getsockname(a0,(structsockaddr__user*)a1,(int__user*)a[2]);
          49. break;
          50. caseSYS_GETPEERNAME:
          51. err=sys_getpeername(a0,(structsockaddr__user*)a1,(int__user*)a[2]);
          52. break;
          53. caseSYS_SOCKETPAIR:
          54. err=sys_socketpair(a0,a1,a[2],(int__user*)a[3]);
          55. break;
          56. caseSYS_SEND:
          57. err=sys_send(a0,(void__user*)a1,a[2],a[3]);
          58. break;
          59. caseSYS_SENDTO:
          60. err=sys_sendto(a0,(void__user*)a1,a[2],a[3],
          61. (structsockaddr__user*)a[4],a[5]);
          62. break;
          63. caseSYS_RECV:
          64. err=sys_recv(a0,(void__user*)a1,a[2],a[3]);
          65. break;
          66. caseSYS_RECVFROM:
          67. err=sys_recvfrom(a0,(void__user*)a1,a[2],a[3],
          68. (structsockaddr__user*)a[4],(int__user*)a[5]);
          69. break;
          70. caseSYS_SHUTDOWN:
          71. err=sys_shutdown(a0,a1);
          72. break;
          73. caseSYS_SETSOCKOPT:
          74. err=sys_setsockopt(a0,a1,a[2],(char__user*)a[3],a[4]);
          75. break;
          76. caseSYS_GETSOCKOPT:
          77. err=sys_getsockopt(a0,a1,a[2],(char__user*)a[3],(int__user*)a[4]);
          78. break;
          79. caseSYS_SENDMSG:
          80. err=sys_sendmsg(a0,(structmsghdr__user*)a1,a[2]);
          81. break;
          82. caseSYS_RECVMSG:
          83. err=sys_recvmsg(a0,(structmsghdr__user*)a1,a[2]);
          84. break;
          85. default:
          86. err=-EINVAL;
          87. break;
          88. }
          89. returnerr;
          90. }/*Itmaybealreadyanotherdescriptor8)Notkernelproblem.*/
          91. returnretval;
          93. out_release:
          94. sock_release(sock);
          95. returnretval;
          96. }
          當(dāng)應(yīng)用程序使用socket()創(chuàng)建一個(gè)socket時(shí)，會(huì)執(zhí)行sys_socket，其定義如下
          [plain]view plaincopy
          print?
          1. asmlinkagelongsys_socket(intfamily,inttype,intprotocol)
          2. {
          3. intretval;
          4. structsocket*sock;
          6. retval=sock_create(family,type,protocol,&sock);//創(chuàng)建socket
          7. if(retval<0)
          8. gotoout;
          10. retval=sock_map_fd(sock);//分配一個(gè)未使用的文件描述符fd，并將socket和fd建立聯(lián)系
          11. if(retval<0)
          12. gotoout_release;
          14. out:
          15. /*Itmaybealreadyanotherdescriptor8)Notkernelproblem.*/
          16. returnretval;
          18. out_release:
          19. sock_release(sock);
          20. returnretval;
          21. }
          結(jié)構(gòu)體socket的定義如下(includelinuxnet.h)：
          [plain]view plaincopy
          print?
          1. structsocket{
          2. socket_statestate;
          3. unsignedlongflags;
          4. structproto_ops*ops;
          5. structfasync_struct*fasync_list;
          6. structfile*file;//通過這個(gè)和文件描述符建立聯(lián)系
          7. structsock*sk;
          8. wait_queue_head_twait;
          9. shorttype;
          10. };
          下面我們?cè)賮砜纯磗ock_map_fd函數(shù)
          [plain]view plaincopy
          print?
          1. intsock_map_fd(structsocket*sock)
          2. {
          3. intfd;
          4. structqstrthis;
          5. charname[32];
          7. /*
          8. *Findafiledescriptorsuitableforreturntotheuser.
          9. */
          11. fd=get_unused_fd();//分配一個(gè)未使用的fd
          12. if(fd>=0){
          13. structfile*file=get_empty_filp();
          15. if(!file){
          16. put_unused_fd(fd);
          17. fd=-ENFILE;
          18. gotoout;
          19. }
          21. this.len=sprintf(name,"[%lu]",SOCK_INODE(sock)->i_ino);
          22. this.name=name;
          23. this.hash=SOCK_INODE(sock)->i_ino;
          25. file->f_dentry=d_alloc(sock_mnt->mnt_sb->s_root,&this);
          26. if(!file->f_dentry){
          27. put_filp(file);
          28. put_unused_fd(fd);
          29. fd=-ENOMEM;
          30. gotoout;
          31. }
          32. file->f_dentry->d_op=&sockfs_dentry_operations;
          33. d_add(file->f_dentry,SOCK_INODE(sock));
          34. file->f_vfsmnt=mntget(sock_mnt);
          35. file->f_mapping=file->f_dentry->d_inode->i_mapping;
          37. sock->file=file;//建立聯(lián)系
          38. file->f_op=SOCK_INODE(sock)->i_fop=&socket_file_ops;//socket操作函數(shù)，當(dāng)使用文件系統(tǒng)的IO函數(shù)時(shí)，其實(shí)使用的是socket的IO函數(shù)
          39. file->f_mode=FMODE_READ|FMODE_WRITE;
          40. file->f_flags=O_RDWR;
          41. file->f_pos=0;
          42. file->private_data=sock;
          43. fd_install(fd,file);
          44. }
          46. out:
          47. returnfd;
          48. }
          50. staticstructfile_operationssocket_file_ops={
          51. .owner=THIS_MODULE,
          52. .llseek=no_llseek,
          53. .aio_read=sock_aio_read,
          54. .aio_write=sock_aio_write,
          55. .poll=sock_poll,
          56. .unlocked_ioctl=sock_ioctl,
          57. .mmap=sock_mmap,
          58. .open=sock_no_open,/*specialopencodetodisallowopenvia/proc*/
          59. .release=sock_close,
          60. .fasync=sock_fasync,
          61. .readv=sock_readv,
          62. .writev=sock_writev,
          63. .sendpage=sock_sendpage
          64. }; 

          
				
            
                
			
							
          
                
			              
              
            
          
		
          
		
          
		
          
		
          
		
          
			
            
				
          • 
					
					
			  	
            • 
			  	
          • 
					
					
			  	
            • 
			  	
          • 
					
					
			  	
            • 
				
          • 
					
					
				
            • 
				
          • 
					
					
				
            • 
			
          
			
          
		
          
		
		
          
		
          
			
			
		
          
        
			
		

	

          
	
	
          
		
          
			
          評(píng)論
          					
		
          
		
          
			
          
			
				
          
					
					
          
						
                        
					
          
				
          
                		
						
						
			
          
		
          
		
          
		
          
            
			
            
		
          
	
          
	
          
	
          
		
		

          


	
          
	
          
		
		
	
          


    
          
        
          技術(shù)專區(qū)
          
      
          
      
          
			
      
           
       

          

   











          
	
          
	    關(guān)閉
	
          
	
	

          







	
	





          



          


看屁屁www成人影院,亚洲人妻成人图片,亚洲精品成人午夜在线,日韩在线 欧美成人

(function(){
    var bp = document.createElement('script');
    var curProtocol = window.location.protocol.split(':')[0];
    if (curProtocol === 'https') {
        bp.src = 'https://zz.bdstatic.com/linksubmit/push.js';
    }
    else {
        bp.src = 'http://push.zhanzhang.baidu.com/push.js';
    }
    var s = document.getElementsByTagName("script")[0];
    s.parentNode.insertBefore(bp, s);
})();