揭开unix网络之纱8-ioctl获得网络接口

1、揭开 unix 网络之纱 8- ioctl 获得网络接口1 概述 需处理网络接口的许多程序沿用的初始步骤之一就是从内核获取配置在系统中的所有接 口。本任务由 SIOCGIFCONF 请求完成，它使用 ifconf 结构， ifconf 又使用 ifreq 结构。1.1 Ifconfig 结构<net/if.h>struct ifconfint ifc_len;unioncaddr_t ifcu_buf;struct ifreq* ifcu_req;ifc_ifcu;#define IFNAMSIZ 16Struct ifreqChar ifr_nameIFNAMSIZ;UnionS

2、truct sockaddr ifru_addr;Struct sockaddr ifru_dstaddr;Struct sockaddr ifru_broadaddr;Short ifru_flags;Int ifru_metric;Caddr_t ifru_data;ifr_ifru;2U#ifndef _UNP_IFI_H#define _UNP_IFI_H#include <net/if.h>#define IFI_NAME 16 /*same as IFNAMSIZ in <net/if.>*/ #define IFI_HADDR 8 /*allow for

3、64-bit EUI-64 in future*/ struct ifi_infochar ifi_nameIFI_NAME; /*interface name,null-terminated*/ short ifi_index;/*interface index*/short ifi_mtu;/*interface MTU*/u_char ifi_haddrIFI_HADDR; /*hardware address*/u_short ifi_hlen;short ifi_flags;short ifi_myflags;struct sockaddr *ifi_addr; struct soc

4、kaddr *ifi_brdaddr; struct sockaddr *ifi_dstaddr; struct ifi_info *ifi_next;/*#bytes in hardware address: 0,6,8*/ /*IFF_XXX constants from <net/if.h>*/ /*our own IFI_XXX flags*/*primary address*/*broadcast address*/*destination address*/*next of these structures*/ ;#define IFI_ALIAS 1 /*ifi_ad

5、dr is an alias*/ /*function prototypes*/struct ifi_info *get_ifi_info(int,int);void free_ifi_info(struct ifi_info *);#endif3 get_ifi_info#include <unistd.h> #include <sys/socket.h> #include <sys/types.h> #include <errno.h> #include <netinet/in.h> #include <sys/ioctl.

6、h> #include <sys/un.h> #include <arpa/inet.h> #include <iostream> #include <string> #include <string.h> #include <net/if.h> #define max(a,b) using namespace std;/将地址转换为字符串，不在这里讨论char *sock_ntop_host(const struct sockaddr *sa, socklen_t salen) static char str128

7、;/* Unix domain is largest */ switch (sa->sa_family) case AF_INET:struct sockaddr_in *sin = (struct sockaddr_in *) sa;if (inet_ntop(AF_INET, &sin->sin_addr, str, sizeof(str) = NULL) return(NULL);return(str);#ifdef IPV6case AF_INET6:struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) sa;if

8、(inet_ntop(AF_INET6, &sin6->sin6_addr, str, sizeof(str) = NULL) return(NULL);return(str);#endif#ifdef AF_UNIX case AF_UNIX:struct sockaddr_un *unp = (struct sockaddr_un *) sa;/* OK to have no pathname bound to the socket: happens on* every connect() unless client calls bind() first. */ if (un

9、p->sun_path0 = 0) strcpy(str, "(no pathname bound)");else snprintf(str, sizeof(str), "%s", unp->sun_path); return(str);#endif#ifdef HAVE_SOCKADDR_DL_STRUCTcase AF_LINK:struct sockaddr_dl *sdl = (struct sockaddr_dl *) sa;if (sdl->sdl_nlen > 0) snprintf(str, sizeof(str)

10、, "%*s", sdl->sdl_nlen, &sdl->sdl_data0);else snprintf(str, sizeof(str), "AF_LINK, index=%d", sdl->sdl_index);return(str);#endifdefault:snprintf(str, sizeof(str), "sock_ntop_host: unknown AF_xxx: %d, len %d", sa->sa_family, salen);return(str);return (NUL

11、L);/关键struct ifi_info* get_ifi_info(int family,int doaliases)/struct ifi_info *ifi,*ifihead,*ifipnext;int sockfd,len,lastlen,flags,myflags,idx=0,hlen=0;char *ptr,*buf,lastnameIFNAMSIZ,*cptr,*haddr,*sdlname;/<net/if.h> 中定义struct ifconf ifc;struct ifreq *ifr,ifrcopy;/地址struct sockaddr_in *sinptr

12、;struct sockaddr_in6 *sin6ptr;/ 创立 socket 套接字，数据报sockfd = socket(AF_INET,SOCK_DGRAM,0); lastlen=0;len=100*sizeof(struct ifreq); /取出网络接口信息 for(;)/开辟 100 fireq 的空间 buf=(char*)malloc(len); ifc.ifc_len=len;ifc.ifc_buf=buf; if(ioctl(sockfd,SIOCGIFCONF,&ifc)<0)if(errno != EINV AL | lastlen != 0) co

13、ut<<"ioctl error"<<endl; exit(0); elseif(ifc.ifc_len = lastlen);break; lastlen=ifc.ifc_len;len+=10*(sizeof(struct ifreq); free(buf);ifihead=NULL; ifipnext=&ifihead;lastname0=0; sdlname=NULL;for(ptr=buf;ptr<buf+ifc.ifc_len;)ifr=(struct ifreq*)ptr;#ifdef HA VE_SOCKADDR_SA_

14、LENlen = max(sizeof(struct sockaddr),ifr->ifr_addr.sa_len);#elseswitch(ifr->ifr_addr.sa_family)#ifdef IPV6case AF_INET6: len=sizeof(struct sockaddr_in6); break;#endifcase AF_INET:default: len=sizeof(struct sockaddr); break;#endif ptr+=sizeof(ifr->ifr_name)+len;#ifdef HA VE_SOCKADDR_DL_STRUC

15、T if(ifr->ifr_addr.sa_family=AF_LINE)struct sockaddr_dl *sdl=(struct sockaddr_dl*)&ifr->ifr_addr; sdlname=ifr->ifr_name;idx=sdl->sdl_index; haddr=sdl->sdl_data + sdl->sdl_nlen; hlen=sdl->sdl_alen;#endifif(ifr->ifr_addr.sa_family != family) continue;myflags=0; if(cptr=strc

16、hr(ifr->ifr_name,':')!=NULL) *cptr=0;if(strncmp(lastname,ifr->ifr_name,IFNAMSIZ) =0)if(doaliases=0)continue;myflags=IFI_ALIAS;memcpy(lastname,ifr->ifr_name,IFNAMSIZ);ifrcopy = *ifr;ioctl(sockfd,SIOCGIFFLAGS,&ifrcopy);flags=ifrcopy.ifr_flags;if(flags & IFF_UP)=0)continue;ifi=

17、(ifi_info*)calloc(1,sizeof(struct ifi_info);*ifipnext=ifi;ifipnext=&ifi->ifi_next;ifi->ifi_flags=flags;ifi->ifi_myflags=myflags;#if defined(SIOCGIFMTU) && defined(HA VE_STRUCT_IFREQ_IFR_MTU) ioctl(sockfd,SIOCGIFMTU,&ifrcopy);ifi->ifi_mtu=ifrcopy.ifr_mtu;#elseifi->ifi_m

18、tu=0;#endifmemcpy(ifi->ifi_name,ifr->ifr_name,IFI_NAME);ifi->ifi_nameIFI_NAME-1='0'if(sdlname=NULL | strcmp(sdlname,ifr->ifr_name) != 0)idx=hlen=0;ifi->ifi_index=idx;ifi->ifi_hlen=hlen;if(ifi->ifi_hlen > IFI_HADDR)ifi->ifi_hlen=IFI_HADDR;if(hlen)memcpy(ifi->ifi_

19、haddr,haddr,ifi->ifi_hlen);switch(ifr->ifr_addr.sa_family)case AF_INET:sinptr=(struct sockaddr_in*)&ifr->ifr_addr;ifi->ifi_addr=(struct sockaddr*)calloc(1,sizeof(struct sockaddr_in); memcpy(ifi->ifi_addr,sinptr,sizeof(struct sockaddr_in);#ifdef SIOCGIFBRDADDRif(flags & IFF_BRO

20、ADCAST) ioctl(sockfd,SIOCGIFBRDADDR,&ifrcopy); sinptr=(struct sockaddr_in*)&ifrcopy.ifr_broadaddr; ifi->ifi_brdaddr=(struct sockaddr*)calloc(1,sizeof(structsockaddr_in);memcpy(ifi->ifi_brdaddr,sinptr,sizeof(struct sockaddr_in);#endif#ifdef SIOCGIFDSTADDRif(flags & IFF_POINTOPOINT)

21、ioctl(sockfd,SIOCGIFDSTADDR,&ifrcopy); sin6ptr=(struct sockaddr_in6*)&ifrcopy.ifr_dstaddr; ifi->ifi_dstaddr=(struct sockaddr*)calloc(1,sizeof(struct sockaddr_in6);memcpy(ifi->ifi_dstaddr,sin6ptr,sizeof(struct sockaddr_in6);#endifbreak;default:break;free(buf); return(ifihead);void free_

22、ifi_info(struct ifi_info *ifihead)struct ifi_info *ifi,*ifinext;for(ifi = ifihead;ifi != NULL;ifi=ifinext) if(ifi->ifi_addr != NULL) free(ifi->ifi_addr);if(ifi->ifi_dstaddr != NULL) free(ifi->ifi_brdaddr);if(ifi->ifi_dstaddr != NULL) free(ifi->ifi_dstaddr);ifinext=ifi->ifi_next;

23、free(ifi);int main(int argc,char* argv)struct ifi_info *ifi,*ifihead;struct sockaddr* sa; u_char *ptr;int i,family,doaliases;if(argc != 3)cout<<"usage: prifinfo <inet4 | inet6 > <doaliases>"<<endl; exit(0);if(strcmp(argv1,"inet4")=0)family=AF_INET;else if(

24、strcmp(argv1,"inet6")=0)family=AF_INET6;elsecout<<"invalid <address-family>"<<endl;exit(0);doaliases=atoi(argv2);for(ifihead = ifi = get_ifi_info(family,doaliases);ifi != NULL;ifi=ifi->ifi_next) printf("%s: ",ifi->ifi_name);if(ifi->ifi_index !

25、= 0)printf("(%d) ",ifi->ifi_index);printf("<");if(ifi->ifi_flags & IFF_UP) printf("UP ");if(ifi->ifi_flags & IFF_BROADCAST) printf("BCAST ");if(ifi->ifi_flags & IFF_MULTICAST) printf("MCAST ");if(ifi->ifi_flags & IFF

26、_LOOPBACK) printf("LOOP ");if(ifi->ifi_flags & IFF_POINTOPOINT) printf("P2P ");printf(">n");if(i=ifi->ifi_hlen) >0)ptr=ifi->ifi_haddr;doprintf("%s%x", (i = ifi->ifi_hlen) ? " ": ":",*ptr+);while(-i>0);printf("n");if(ifi->ifi_mtu != 0)printf(" MTU: %dn",ifi->ifi_mtu);if(sa = ifi->ifi_addr) != NULL)printf(" IP addr: %sn",sock_ntop_host(sa,sizeof(*sa);if(sa = ifi->ifi_brdaddr) != NULL)printf(" broadcast addr: %sn",sock_ntop_host(sa,sizeof(*sa); if(s