I want to improve packet transmitting performance. Before that I used raw sockets and now I study packet_mmap. I have packets(frames) which I already captured from kernel module from another PC, put to current PC and now I want to retransmit them to local interface with following forwarding. I have got example of packet_mmap, integrated it to my project, but I send fd_socket = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); memset(&my_addr, 0, sizeof(struct sockaddr_ll)); my_addr.sll_family = PF_PACKET; my_addr.sll_protocol = htons(ETH_P_ALL); strcpy(str_devname, "eth0"); strncpy(s_ifr.ifr_name, str_devname, sizeof(s_ifr.ifr_name)); ec = ioctl(fd_socket, SIOCGIFINDEX, &s_ifr); i_ifindex = s_ifr.ifr_ifindex; memset(&my_addr, 0, sizeof(struct sockaddr_ll)); my_addr.sll_family = AF_PACKET; my_addr.sll_protocol = ETH_P_ALL; my_addr.sll_ifindex = i_ifindex; bind(fd_socket, (struct sockaddr *) &my_addr, sizeof(struct sockaddr_ll) s_packet_req.tp_block_size = c_buffer_sz; s_packet_req.tp_frame_size = c_buffer_sz; s_packet_req.tp_block_nr = c_buffer_nb; s_packet_req.tp_frame_nr = c_buffer_nb; size = s_packet_req.tp_block_size * s_packet_req.tp_block_nr; if (setsockopt(fd_socket, SOL_PACKET, PACKET_TX_RING, (char *) &s_packet_req, sizeof(s_packet_req)) < 0) { perror("setsockopt: PACKET_TX_RING"); return; } if (c_sndbuf_sz) { printf("send buff size = %d\n", c_sndbuf_sz); if (setsockopt(fd_socket, SOL_SOCKET, SO_SNDBUF, &c_sndbuf_sz, sizeof(c_sndbuf_sz)) < 0){ perror("getsockopt: SO_SNDBUF"); exit(1); } } data_offset = TPACKET_HDRLEN - sizeof(struct sockaddr_ll); printf("data offset = %d bytes\n", data_offset); ps_header_start = (tpacket_hdr *) mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_socket, 0); if (ps_header_start == (void*) -1) { perror("mmap"); exit(1); } Then I fill data ps_header = ((struct tpacket_hdr *) ((char *) ps_header_start + (c_buffer_sz * i_index))); if (!ps_header) { perror("ps_header") ; return NULL; } data = ((char*) ps_header) + data_offset; switch ((volatile uint32_t) ps_header->tp_status) { case TP_STATUS_AVAILABLE: printf("TP_STATUS_AVAILABLE, index=%d\n",i_index) ; memcpy(data, packet_data, size); pthread_mutex_lock(&index_locker) ; i_index++; pthread_mutex_unlock(&index_locker) ; if (i_index >= c_buffer_nb) { i_index = 0; first_loop = 0; } /* update packet len */ ps_header->tp_len = size; /* set header flag to USER (trigs xmit)*/ ps_header->tp_status = TP_STATUS_SEND_REQUEST; then I send ec_send = sendto(fd_socket, NULL, 0, 0, (struct sockaddr *) ps_sockaddr, sizeof(struct sockaddr_ll)); I have got no errors, ec_send=not null size of sended data. But there are no data routed to destination host. So, I ask - what data I should pass to ring buffer, now I include headers ip,tcp, should I include MAC header? - May be I have to set additional flags to route my packets.