问个raw socket使用的问题

zhoufanking

我想学着用raw socket写一个ping，有几个问题想问问：
创建socket的时候用的是socket(AF_INET,SOCK_RAW,IPPROTO_ICMP)，协议指定的是ICMP，那么构造数据包的时候还需要自己构造ip头吗？
我自己试着写了一段代码，如下。在recfrom的地方总是从socket读不出东西，一直在死等。请帮我看看是怎么回事阿！另外哪里有比较详细的raw socket的文档呢？谢谢！

#include "errexit.h" #include <sys/socket.h> #include <sys/types.h> #include <arpa/inet.h> #include <string.h> #include <errno.h> #include <linux/icmp.h> #include <linux/ip.h> #include <unistd.h> #define BUFFLENGTH    4096 void Usage()__attribute__((noreturn)); unsigned short in_cksum(unsigned short *addr, int len); char *ProgName = "rping"; char *myip = "192.168.1.3"; int main( int argc, char * argv[]) {     if( argc != 2 )         Usage();         struct sockaddr_in to, from;     char *buffer[BUFFLENGTH];     char *recvbuffer[BUFFLENGTH];     struct icmphdr *icmphd;     struct iphdr *iphd;     int res;     int tosock;     int fromlen = sizeof(struct sockaddr);     int one = 1;     int *ptr_one = &one;         to.sin_family = AF_INET;     res = inet_aton(argv[1],&to.sin_addr);     if( res < 0 )         errexit("invalid address!\n%s\n",strerror(errno));     memset(buffer,0x00,BUFFLENGTH);     memset(recvbuffer,0x00,BUFFLENGTH);         /*      * create a socket to send out the icmp echo message      */     tosock = socket(AF_INET,SOCK_RAW,IPPROTO_ICMP);     if(tosock<0)         errexit("create socket failed!\n%s\n",strerror(errno));          setsockopt(tosock, IPPROTO_IP, IP_HDRINCL,ptr_one, sizeof(one));     /*      * construct the ip header      */     iphd = ( struct iphdr *)buffer;     iphd->version = 4;     iphd->ihl = 5;     iphd->tos = 0;     iphd->id = getpid() & 0xffff;     iphd->frag_off =0;     iphd->ttl = 128;     iphd->protocol =IPPROTO_ICMP;     iphd->check = 0;     iphd->saddr = inet_addr(myip);     iphd->daddr = to.sin_addr.s_addr;             /*      * construct the icmp header      */     icmphd = (struct icmphdr *)(iphd+1);     icmphd->type = ICMP_ECHO;     icmphd->code = 10;     icmphd->checksum = in_cksum((unsigned short *)icmphd,64);     icmphd->un.echo.id = (short)(getpid()&0xffff);     icmphd->un.echo.sequence = 1;     while(1)     {         res = sendto(tosock,(void *)iphd,128,0,(struct sockaddr*)&to,sizeof(struct sockaddr));         if(res == -1)             errexit("rping error occured!\n%s\n",strerror(errno));         else if(res == 128)             break;         else if (errno == EINTR)             continue;     }         printf("done,%d bytes sent.\n",res);         //while(1)     //{         res = recvfrom(tosock,recvbuffer,BUFFLENGTH,0,(struct sockaddr*)&from,(socklen_t *)&fromlen);         if(res == -1)             errexit("rping recv failed!\n%s\n",strerror(errno));     //    else if( errno == EINTR)     //        continue;     //    else     //        break;     //}              iphd = (struct iphdr *)recvbuffer;         icmphd = (struct icmphdr*)(iphd+1);     if(icmphd->type == ICMP_ECHOREPLY)     {         printf("ping %d bytes received,seq = %d,code = %d\n",                 res,                 icmphd->un.echo.sequence & 0xffff,                 icmphd->code & 0xff);              }         return 0; } void Usage() {     printf("%s dstIPaddress\n",ProgName);     exit(-1); } unsigned short in_cksum(unsigned short *addr, int len) {     int nleft = len;     unsigned short *w = addr;     unsigned short answer;     int sum = 0;            while(nleft > 1)     {         sum+=*w++;         nleft -= 2;     }       if(nleft == 1)     {         unsigned short u = 0;                  *(unsigned short *)(&u) = *(unsigned short *)w;         sum +=u;     }     sum = ( sum >> 16 ) + (sum & 0xffff);     sum +=(sum>>16);                                answer = ~sum;                                   return ( answer );     }

@sky

要，RAW就是要自己构造IP头

zhoufanking

如果不设置IP_HDRINCL的话，是不是就不用自己构造ip头了

zhoufanking

我把代码改了一下，现在可以ping通自己了，但是在ping别的主机是，在recfrom的地方还是一直在死等。请帮我看看是怎么回事阿！另外哪里有比较详细的raw socket的文档呢？谢谢！

#define BUFFLENGTH    4096 void Usage()__attribute__((noreturn)); unsigned short in_cksum(unsigned short *addr, int len); char *ProgName = "rping"; char *myip = "192.168.1.3"; int main( int argc, char * argv[]) {     if( argc != 2 )         Usage();         struct sockaddr_in to, from;     char *buffer[BUFFLENGTH];     char *recvbuffer[BUFFLENGTH];     struct icmphdr *icmphd;     struct iphdr *iphd;     int res;     int tosock;     int fromlen = sizeof(struct sockaddr);     int one = 1;     int *ptr_one = &one;         to.sin_family = AF_INET;     res = inet_aton(argv[1],&to.sin_addr);     if( res < 0 )         errexit("invalid address!\n%s\n",strerror(errno));         memset(buffer,0x00,BUFFLENGTH);     memset(recvbuffer,0x00,BUFFLENGTH);         /*      * create a socket to send out the icmp echo message      */     tosock = socket(AF_INET,SOCK_RAW,IPPROTO_ICMP);     if(tosock<0)         errexit("create socket failed!\n%s\n",strerror(errno));         res = setsockopt(tosock, IPPROTO_IP, IP_HDRINCL,ptr_one, sizeof(one));     if(res < 0)         errexit("setsockopt failed!\n%s\n",strerror(errno));     /*      * construct the ip header      */     iphd = ( struct iphdr *)buffer;     iphd->version = 4;     iphd->ihl = 5;     iphd->tos = 0;     iphd->tot_len = 84;     iphd->id = getpid() & 0xffff;     iphd->frag_off =0;     iphd->ttl = 32;     iphd->protocol =IPPROTO_ICMP;     iphd->check = 0;     iphd->saddr = inet_addr(myip);     iphd->daddr = to.sin_addr.s_addr;              /*      * construct the icmp header      */     icmphd = (struct icmphdr *)(iphd+1);     icmphd->type = ICMP_ECHO;     icmphd->code = 5;     icmphd->checksum = in_cksum((unsigned short *)icmphd,64);     icmphd->un.echo.id = (short)(getpid()&0xffff);     icmphd->un.echo.sequence = 1;     while(1)     {         res = sendto(tosock,(void *)buffer,84,0,(struct sockaddr*)&to,sizeof(struct sockaddr));         if(res == -1)             errexit("rping error occured!\n%s\n",strerror(errno));         else if(res == 84)             break;         else if (errno == EINTR)             continue;     }         printf("done,%d bytes sent.\n",res);         char *addr = (char *)&(iphd->saddr);             printf("src ip address is :%d.%d.%d.%d\n",                     addr[0]&0xff,addr[1]&0xff,addr[2]&0xff,addr[3]&0xff);         while(1)     {         res = recvfrom(tosock,recvbuffer,BUFFLENGTH,0,(struct sockaddr*)&from,(socklen_t *)&fromlen);         if(res == -1)             errexit("rping recv failed!\n%s\n",strerror(errno));         else if( errno == EINTR)             continue;                  iphd = (struct iphdr *)recvbuffer;             char *saddr = (char *)&(iphd->saddr);                  icmphd = (struct icmphdr*)(iphd+1);         if(icmphd->type == ICMP_ECHO)             continue;         if(icmphd->type == ICMP_ECHOREPLY)         {             printf("ping %d bytes received,seq = %d,code = %d\n",                     res,                     icmphd->un.echo.sequence & 0xffff,                     icmphd->code & 0xff);             printf("src ip address is :%d.%d.%d.%d\n",                     saddr[0]&0xff,saddr[1]&0xff,saddr[2]&0xff,saddr[3]&0xff);             break;                  }     }     return 0; }

[ 本帖最后由 zhoufanking 于 2008-8-27 23:19 编辑 ]

gawk

上google搜一下ping的源代码看看，比较一下

zhoufanking

我用TCPDUMP看了一下，对方收到了我发送的echo request但没有发出echo reply.这是怎么回事呢？