内核与用户态通信(setsockopt).docx

netfilter提供了nf_register_sockopt()和nf_unregister_sockopt()来动态登记或取消sockopt命令字；打开一个网络socket后可以使用set/getsockopt(2)可实现用户空间与内核的通信，本质和ioctl差不多，区别在于set/getsockopt不用新建设备，直接利用系统已有的socket类型就可以进行，可用setsockopt函数向内核写数据，用getsockopt向内核读数据。module.c:#include#include#include#include#include#include#include#defineSOCKET_OPS_BASE128#defineSOCKET_OPS_SET(SOCKET_OPS_BASE)#defineSOCKET_OPS_GET(SOCKET_OPS_BASE)#defineSOCKET_OPS_MAX(SOCKET_OPS_BASE+1)#defineKMSGamessagefromkernel#defineKMSG_LENsizeof(amessagefromkernel)MODULE_LICENSE(GPL);staticintrecv_msg(structsock*sk,intcmd,void_user*user,unsignedintlen)intret=0;printk(KERN_INFOsockopt:recv_msg()n);if(cmd=SOCKET_OPS_SET)charumsg64;intlen=sizeof(char)*64;memset(umsg,0,len);ret=copy_from_user(umsg,user,len);printk(recv_msg:umsg=%s.ret=%dn,umsg,ret);return0;staticintsend_msg(structsock*sk,intcmd,void_user*user,int*len)intret=0;printk(KERN_INFOsockopt:send_msg()n);if(cmd=SOCKET_OPS_GET)ret=copy_to_user(user,KMSG,KMSG_LEN);printk(send_msg:umsg=%s.ret=%d.successn,KMSG,ret);return0;staticstructnf_sockopt_opstest_sockops=.pf=PF_INET,.set_optmin=SOCKET_OPS_SET,.set_optmax=SOCKET_OPS_MAX,.set=recv_msg,.get_optmin=SOCKET_OPS_GET,.get_optmax=SOCKET_OPS_MAX,.get=send_msg,.owner=THIS_MODULE,;staticint_initinit_sockopt(void)printk(KERN_INFOsockopt:init_sockopt()n);returnnf_register_sockopt(&test_sockops);staticvoid_exitfini_sockopt(void)printk(KERN_INFOsockopt:fini_sockopt()n);nf_unregister_sockopt(&test_sockops);module_init(init_sockopt);module_exit(fini_sockopt);user.c:#include#include#include#include#include#include#defineSOCKET_OPS_BASE128#defineSOCKET_OPS_SET(SOCKET_OPS_BASE)#defineSOCKET_OPS_GET(SOCKET_OPS_BASE)#defineSOCKET_OPS_MAX(SOCKET_OPS_BASE+1)#defineUMSGamessagefromuserspace#defineUMSG_LENsizeof(amessagefromuserspace)charkmsg64;intmain(void)intsockfd;intlen;intret;sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_RAW);if(sockfd0)printf(cannotcreateasocketn);return-1;/*callfunctionrecv_msg()*/ret=setsockopt(sockfd,IPPROTO_IP,SOCKET_OPS_SET,UMSG,UMSG_LEN);printf(setsockopt:ret=%d.msg=%sn,ret,UMSG);len=sizeof(char)*64;/*callfunctionsend_msg()*/ret=getsockopt(sockfd,IPPROTO_IP,SOCKET_OPS_GET,kmsg,&len);printf(getsockopt:ret=%d.msg=%sn,ret,kmsg);if(ret!=0)printf(getsockopterror:errno=%d,errstr=%sn,errno,strerror(errno);close(sockfd);return0;Makefile:TARGET=testOBJS=test.oMDIR=drivers/miscEXTRA_CFLAGS=-DEXPORT_SYMTABCURRENT=$(shelluname-r)KDIR=/lib/modules/$(CURRENT)/buildPWD=$(shellpwd)DEST=/lib/modules/$(CURRENT)/kernel/$(MDIR)obj-m:=$(TARGET).o$(TARGET)-objs:=module.odefault:make-C$(KDIR)SUBDIRS=$(PWD)modulesgcc-ouseruser.c$(TARGET).o:$(OBJS)$(LD)$(LD_RFLAG)-r-o$(OBJS)ifneq(,$(findstring2.4.,$(CURRENT)install:su-ccp-v$(TARGET).o$(DEST)&/sbin/depmod-aelseinstall:su-ccp-v$(TARGET).ko$(DEST)&/sbin/depmod-aendifclean:-rm-rf*.o*