RAW socket when sendto() always return -1(ENOBUFS) ???????

I create a raw packet socket and bind

it to a isdn device. It seems ok.

but I call sendto() but always return -1

the errno is 105 means no buffer space available

why?

I call like this:

struct sockaddr_ll sl;
memset(&sl,0,sizeof(sl));
sl.sll_family = AF_PACKET;
//other member of sl is not needed because
//it is a raw packet socket
sendto(s,buf,len,0,(struct sockaddr*)sl,sizeof(sl));