nd_opt_source_link_addr
memcpy(&nd_opt_source_link_addr, &iface->hw_address,
sizeof(nd_opt_source_link_addr));
sizeof(nd_opt_hdr) + sizeof(nd_opt_source_link_addr))
struct ether_addr nd_opt_source_link_addr;
sndmhdr.msg_iov[2].iov_base = (caddr_t)&nd_opt_source_link_addr;
sndmhdr.msg_iov[2].iov_len = sizeof(nd_opt_source_link_addr);
struct nd_opt_source_link_addr *ndopt_source_link_addr;
ndopt_source_link_addr = (struct nd_opt_source_link_addr *)p;