嵌入式netconsole源码分析3 1几个重要的数据结构

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Ntonol-43.1几个重要的数据结构·-43.1.1structconsole-43.1.2structnetpoll·······························-53.1.3·····························-5-3.1.4····························-6-3.2实现分析·--3.2.1Netconsole初始化·······························-7-3.2.2具体运行实现··--网络的方式传送到另一台主机上。这样，就可以实现某台机子的kernelpanic信息这里使用的是netcat的方式进行监视的。安装好netcat后，执行s命令：#netcat-l-p3000030000块的依赖，以及在加载时必须配置相关的端口，IPs执行命令如下：#modprobenetconsolenetconsole=6666@25/eth7,30000@20/00:0C:29:E2:87:E8–30000@20/00:0C:29:E2:87:E8：三个位段分别是，远端端口，远端IP地址及远端机子的MAC地址。也就是我们在2.1节中指定的端口30000，以及其IP地址和MAC world模块，看看我们的printk信息是怎样被发送到主机上去的。1 #include#include#include6staticint{return11static {15 47$(RM)*.o*.mod.c*.ko##insmodnetconsole:networkloggingstartedoWorldnetconsole:networkloggingstartedoWorldGoodbye核的地址等。下面，我们开始来分析内核源码的netconsole的实现。Theinterfaceforaconsole,oranyotherdevicethatwantstoconsolemessages(printerIfaconsoledriverismarkedCON_BOOTthenitwillbeauto-whenthefirstrealconsoleis Thisisforearly-printk#define #defineCON_CONSDEV (2)/*Lastonthecommandline*/#defineCON_ENABLED #define #define (16)/*Safetocallwhencpuisofflinestruct{charvoid(*write)(structconsole*,constchar*,unsigned);int(*read)(structconsole*,char*,unsigned);structtty_driver*(*device)(structconsole*,int*);void(*unblank)(void);int(*setup)(structconsole*,char*); intcflag; console构，并实现其信息捕捉函数，即write函数。structnetpoll{structnet_device*dev;指向实际的网卡chardev_name[16],*name;//名字void*rx_hook)(structnetpoll*,intchar*,int钩子函数，这里并没有用到void(*drop)(structsk_buff*skb);//函数netconsole实现的一个关键数据结构。net_device成员指向了实际的网卡，我们正是通dmesg信息，因此就必须通过实际的网卡来发送数据。实际上，这个structnet_device{Thisisthefirstfieldofthe"visible"partofthis(i.e.asseenbyusersinthe"Space.c" Itisthethe /*devicenamehashchain*/structhlist_node #ifdefCONFIG_NETPOLL#ifdef (*poll_controller)(structnet_device*dev);/*bridgestuffstruct #ifdef/*thiswillgetinitializedateachinterfacetypeinitroutine*/structdivert_blk /*class/net/nameentry*/structclass_deviceclass_dev;/*spaceforoptionalstatisticsandwirelesssysfsgroups*/structattribute_group net_device结构包含了一个网络设备相关的所有信息，这里并没有全部列出其成员，其中用粉红色标记出来的，正是和netpoll相关的结构。从这里我们可以看到，如果要支持netconsolenetpollnetpollCONFIG_NETPOLL和CONFIG_NET_POLL_CONTROLLER这两个选项。structnetpoll_info{;//inttries;//如果发送失败，指定了发送信息的次数intrx_flags;spinlock_tstructnetpoll*rx_np;/*netpollthatregisteredanrx_hook*/structsk_buff_headarp_tx;/*listofarprequeststoreplyto*/staticcharconfig[256];//定义模块加载时指定参数选项的bufmodule_param_string(netconsoleconfig,256,0定义模块参数 consolestructconsole。因此，我们/*netconsolemoduleinitialization*/staticintinit_netconsole(void){/*Theconfigisthemoduleparameter,whichcontainsthecaptureoptions);printk("netconsole:notconfigured,aborting\n");return0;}/*Setupthenetpollcaptureoperations//指定了netpollreturn-/*registernetconsolethatcangettheprintkinfo*/register_console(&netconsole);//netconsoleprintk(KERN_INFO"netconsole:networkloggingstarted\n");return0;}/*Initializetheconsolecapture...*/staticstructconsolenetconsole={.name=.flags=CON_ENABLED|staticintconfiguredstaticintoption_setup(char{/*parsetheconsolecaptureoptions*/configured=!netpoll_parse_options(&np,opt);return1;}staticstructnetpollnp=//.remote_mac={0xff,0xff,0xff,0xff,0xff,0xff},//默认的机MAC地址，实际上intnetpoll_setup(structnetpoll{structnet_device*ndev=NULL;structin_device*in_dev;unsignedlongflags;if(np->dev_name)/*findthenetworkinterfacecardndev=dev_get_by_name(np->dev_name);if(!ndev){printk(KERN_ERR"%s:%sdoesn'texist,aborting.\n",np->name,np->dev_name);return-}np->devndev;npnpinfo=kmalloc(sizeof(*npinfo),GFP_KERNEL);if(!npinfo)gotonpinfo->rx_flags=npinfo->poll_owner=-1;//暂时无npinfo->triesMAX_RETRIES设定如果发送失败的话，重复的最大次数}npinfo=ndev-if(!ndev->poll_controller){//netdevpoll_controller，否则将不能支持printk(KERN_ERR"%s:%sdoesn'tsupportpolling,aborting.\n",np->name,np->dev_name);goto}ifnetif_running(ndev检查网卡是否启动unsignedlongatmost,atleast;printk(KERN_INFO"%s:device%snotupyet,forcingit\n",np->name,np->dev_name);if(dev_change_flags(ndev,ndev->flags|IFF_UP)<{printk(KERN_ERR"%s:failedtoopen%s\n",np->name,np->dev_name);gotorelease;}atleast=jiffies+HZ/10;atmost=jiffies+while(!netif_carrier_ok(ndev)){{"%s:timeoutwaitingforcarrier\n",}}/*Ifcarrierappearstocomeupinstantly,wetrustitandpausesothatwedon'tpumpallqueuedconsolemessagesintotheif(time_before(jiffies,{printk(KERN_NOTICE"%s:carrierdetect"untrustworthy,waiting4seconds\n",}}/*initializethelocalmac,thatwhyweneednotsetthelocalmacfortheoptions这里要进行本地mac地址的初始化。if(is_zero_ether_addr(np->local_mac)&&ndev->dev_addr)memcpy(np->local_mac,ndev->dev_addr,6);in_dev if(!in_dev||!in_dev-{printk(KERN_ERR"%s:noIPaddressfor%s,aborting\n",np->name,np->dev_name);goto}np->local_ip=ntohl(in_dev->ifa_list->ifa_local);printk(KERN_INFO"%s:localIP%d.%d.%d.%d\n",np->name,HIPQUAD(np->local_ip));}if(np->rx_hook)spin_lock_irqsave(&npinfo->rx_lock,flags);npinfo->rx_flags|=NETPOLL_RX_ENABLED;npinfo->rx_np=np;spin_unlock_irqrestore(&npinfo->rx_lock,flags);}/*filluptheskbqueue*//*lastthingtodoislinkittothenetdevicestructure*/ndev->npinfo=npinfo;/*avoidracingwithNAPIreadingnpinfo*/returnif(!ndev->npinfo) np->dev=NULL;return-1;}netconsolewrite函数的初始化，正是这个函数实现了对终端信息的捕捉。下面，我们就来分析一下write_msg()staticvoidwrite_msg(structconsole*con,constchar*msg,unsignedint{intfrag,left;unsignedlongflags;iffor(left=len;left;)/*thetransport msgshouldNOTlargerthanMAX_PRINT_CHUNK*/frag=min(left,MAX_PRINT_CHUNK);netpoll_send_udp(&np,msg,frag);/*sendthemsg*/msg+=frag;left-=}}voidnetpoll_send_udp(structnetpoll*np,constchar*msg,intlen){inttotal_len,eth_len,ip_len,udp_len;structsk_buff*skb;structudphdr*udph;structiphdr*iph;structethhdr*eth;udp_len=len+ip_len=eth_len=udp_len+total_len=eth_len+ETH_HLEN+skb=find_skb(np,total_len,total_len-len);if(!skb)memcpy(skb->data,msg,len);skb->len+=len;udph=(structudphdr*)skb_push(skb,sizeof(*udph));udph->source=htons(np->local_port);udph->dest=htons(np->remote_port);udph->len=htons(udp_len);udph->check=iph=(structiphdr*)skb_push(skb,/*iph->version=4;iph->ihl=5;*/put_unaligned(0x45,(unsignedchar*)iph); =0; =0; = =0;put_unaligned(htonl(np->local_ip),&(iph->saddr));put_unaligned(htonl(np->remote_ip),&(iph->daddr)); =ip_fast_csum((unsignedchar*)iph,iph-eth=(structethhdr*)skb_push(skb,eth->h_proto=htons(ETH_P_IP);memcpy(eth->h_dest,np->remote_mac,6);skb->dev=np->dev;}这个函数看起来并不复杂，主要是对一些控制信息的设置，最后调用了来发送数据。接下来看看netpoll_send_skp()是怎样实现的：staticvoidnetpoll_send_skb(structnetpoll*np,structsk_buff*skb){intif(!np||!np->dev||!netif_running(np->dev)){ }npinfo=np->dev-/*avoidrecursion/*forourowncpu我们