What's the problem? Help me!

[zam_ustc@xxxxxxx]

hi,everybody!
I want to use raw socket to send my ipv6 packets.I want to fill the
ipv6 header myself. But I cannot succeed. My programme goes as follows:

#include<signal.h>
#include<sys/socket.h>
#include<netinet/ip6.h>
#include<netinet/icmp6.h>
#include<stdio.h>
#include<netdb.h>
#include<netinet/in.h>

void sigalrm(int );
void SendEchoRequest(void);

#define MAX_BUFF_LEN 1000

void *buff;
struct sockaddr *sendaddr;
int sendlen,sockfd;
int seq=0;
struct addrinfo hints,*res;

main()
{int on=1;
 buff=malloc(MAX_BUFF_LEN);
 hints.ai_flags=AI_CANONNAME;
 hints.ai_family=0;
 hints.ai_socktype=0;
 getaddrinfo("3ffe:3216:2101:601:101::6",NULL,&hints,&res);
 sendaddr=res->ai_addr;
 sendlen=res->ai_addrlen;
 signal(SIGALRM,sigalrm);
 if((sockfd=socket(sendaddr->sa_family,SOCK_RAW,1))<0)
    perror("socket");
 if(setsockopt(sockfd,IPPROTO_IPV6,IP_HDRINCL,&on,sizeof(on))<0)
     perror("setsockopt");
 sigalrm(SIGALRM);
 while(1);
}

void sigalrm(int signo)
{SendEchoRequest();
 seq++;
 alarm(3);
 return;
void SendEchoRequest(void)
{struct ip6_hdr *ip6;
 struct icmp6_hdr *icmp6;
 int len=0;
 ip6=(struct ip6_hdr*)buff;
 ip6->ip6_vfc=6<<4;
 ip6->ip6_vfc|=1;
 ip6->ip6_flow=ip6->ip6_vfc;
 ip6->ip6_flow<<=24;
 ip6->ip6_flow|=1;
 ip6->ip6_nxt=58;
 ip6->ip6_hlim=2;
 len+=sizeof(struct ip6_hdr);
 icmp6=(struct icmp6_hdr *)(buff+sizeof(struct ip6_hdr));
 icmp6->icmp6_type=ICMP6_ECHO_REQUEST;
 icmp6->icmp6_code=0;
 icmp6->icmp6_id=0x8888;
 icmp6->icmp6_seq=seq%1000;
 len+=sizeof(struct icmp6_hdr);
 icmp6->icmp6_seq=seq%1000;
 len+=sizeof(struct icmp6_hdr);
 len+=8;
 if(sendto(sockfd,buff,len,0,sendaddr,sendlen)!=len)
         perror("sendto");
}

  This is just a  programme to test the setsockopt() using IP_HDRINCL.
 The packets I receive is not what I want to send. Why?
 Thanks for any help.

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