Cannot connect() setting SO_BINDTODEVICE to another interface (2.4.17 / libc6 2.2.4)

[Tuxisuau]

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Hi.

I've been trying to code some client program that allow me to specify
the interface i want to connect through. I've tried to do something
like:

setsockopt(ifd, SOL_SOCKET, SO_BINDTODEVICE, interface, strlen(interface)+1=
);

Ok, it worked perfecly for raw sockets in some experiment i did in the
past... only sending.
But when i try to do that with a TCP socket, the syn is sent and the syn
& ack received in the correct interface. But then connection does not
continue.
The connection completes perfecly if the interface i use is the default rou=
te.
Then I tried to bind the source adress before, etc without good results.

I'm using libc6 2.2.4-7 Debian Unstable package, and kernel 2.4.17.

Here's a example:

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
int main()
{
        int ifd;
        char *interface;
        struct sockaddr_in server,client;

        interface =3D (char *)malloc(4);
        strncpy(interface, "ppp0\0",5);

        server.sin_family =3D AF_INET;
        server.sin_port =3D htons(21);
        server.sin_addr.s_addr =3D inet_addr("10.0.0.1"); /* ftp server add=
ress */
        bzero(&(server.sin_zero),8);

        client.sin_port =3D htons(0);
        client.sin_addr.s_addr =3D inet_addr("172.16.0.1"); /* my ppp0 addr=
ess */

        if((ifd =3D socket(AF_INET, SOCK_STREAM, 0))=3D=3D-1)
        {
                perror("socket()");
                exit(-1);
        }
        if((setsockopt(ifd, SOL_SOCKET, SO_BINDTODEVICE, interface, strlen(=
interface)+1))=3D=3D-1)
        {
                perror("setsockopt() SO_BINDTODEVICE");
                exit(-1);
        }

        if((bind(ifd, (struct sockaddr *)&client,sizeof(struct sockaddr)))=
=3D=3D-1) /* it's really required? */
        {
                perror("bind()");
                exit(-1);
        }

        if((connect(ifd, (struct sockaddr *)&server,sizeof(struct sockaddr)=
))=3D=3D-1)
        {
                perror("connect()");
                exit(-1);
        }

        return 0;
}

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tuxisuau. [e-mail]
http://tuxisuau.7a69ezine.org

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