[ds6-devel] why I MUST set a value to scope_id?

[guo zhenglin]

thanks very much!!

My linux machine have TWO ethernet adapters.
now I config ip address on one adapter to 3ffe:2400:xxxx,
then from another linux machine ,CAN connect to it
without set  scope_id=3 value ( default scope_id=0)  !!




----- Original Message ----- 
From: "Eva M. Castro" <eva at gsyc.escet.urjc.es>
To: "guo zhenglin" <guo364 at oki.com>
Cc: <ds6-devel at deepspace6.net>
Sent: Tuesday, August 19, 2003 4:12 PM
Subject: Re: [ds6-devel] why I MUST set a value to scope_id?


> Suppose you have multiple ethernet adapters, if you use a link local
> address as destination, your host does not know which ethernet adapter
> use to send the packet. It is an ambiguos destination address if you
> dont use the scope identifier in order to specify which ethernet adapter
> should be used.
>
> IMHO you should avoid using link local addresses from applications.
>
> regards,
>
> eva
>
> guo zhenglin wrote:
>
> >1) I use "getaddrinfo" ,
> > then socket(),
> >then connect()
> >it return "Inavlid argument" error
> >
> >2) then I use:
> >
> >((struct sockaddr_in6 *)(res1->ai_addr))->sin6_scope_id =3
> > /* 3 is my eth0 index */
> >
> >then connect() is ok ,and send,recv also ok
> >
> >3) I have test it on linux kernel 2.4.7-10 and 2.4.20
> >   both linux kernel have this problem.
> >
> >4) my client program is following:
> >
> >#include <stdio.h>
> >
> >#include <sys/socket.h>
> >#include <sys/types.h>
> >#include <netdb.h>
> >#include <errno.h>
> >
> >int main(void)
> >{
> > int mysock, myerr;
> > int  i;
> > struct addrinfo hints, *res0, *res1;
> > char rcvmsg[100];
> > char sndmsg[100];
> > int rcvlen;
> >
> > memset(&hints, 0, sizeof(hints));
> > hints.ai_family = PF_UNSPEC;
> > hints.ai_socktype = SOCK_STREAM;
> >
> > myerr = getaddrinfo("fe80::210:5cff:fed7:46c6","5001", &hints, &res0);
> > if(myerr) return -1;
> >
> > printf("\n getaddrinfo success");
> >
> > for(res1 = res0; res1; res1 = res1->ai_next)
> > {
> >  printf("\n--------------------------------");
> >  printf("\n ai_flags:%d", res1->ai_flags);
> >  printf("\n ai_family:%d", res1->ai_family);
> >  printf("\n ai_socktype:%d", res1->ai_socktype);
> >  printf("\n ai_protocol:%d", res1->ai_protocol);
> >  printf("\n ai_addrlen:%d",  res1->ai_addrlen);
> >  printf("\n ai_cannonname:%s", res1->ai_canonname);
> >  printf("\n ai_next:%p",  res1->ai_next);
> >  printf("\n ai_addr:");
> >  for(i=0; i<res1->ai_addrlen; i++)
> >   printf("%02X ",(*((char *)(res1->ai_addr)+i))&0xFF);
> >  printf("\n IP:%d", (res1->ai_family==PF_INET6)? 6:4);
> >
> >  printf("\n------------------------------------");
> >
> >  mysock = socket(res1->ai_family, res1->ai_socktype, res1->ai_protocol);
> >  if(mysock<0){ printf("\n socket fail"); continue;}
> >  printf("\n socket success");
> >
> >  ((struct sockaddr_in6 *)(res1->ai_addr))->sin6_scope_id =3 ;  /* ??? */
> >
> >  printf("\n connecting...\n");
> >  if(connect(mysock, res1->ai_addr, res1->ai_addrlen)<0)
> >  {
> >   perror("\n connect fail");
> >   close(mysock);
> >   continue;
> >  }
> >  printf("\n connect succ");
> >  memset(rcvmsg, 0, 100);
> >  rcvlen = recv(mysock, rcvmsg, 100, 0);
> >  printf("\n recvlen:%d", rcvlen);
> >  printf("\n recvmsg:%s", rcvmsg);
> >  strcpy(sndmsg, "THIS is a MSG from CLIENT side");
> >  send(mysock, sndmsg, strlen(sndmsg),0);
> >
> > }
> > close(mysock);
> > printf("\n bye \n");
> >
> >}
> >
> >
> >_______________________________________________
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> >ds6-devel at deepspace6.net
> >http://lists.deepspace6.net/listinfo/ds6-devel
> >
> >
> >
>
>
>