/** * Called by tcp_close() to send a segment including FIN flag but not data. * * @param pcb the tcp_pcb over which to send a segment * @return ERR_OK if sent, another err_t otherwise */ err_t tcp_send_fin(struct tcp_pcb *pcb) { /* first, try to add the fin to the last unsent segment */ if (pcb->unsent != NULL) { struct tcp_seg *last_unsent; for (last_unsent = pcb->unsent; last_unsent->next != NULL; last_unsent = last_unsent->next); if ((TCPH_FLAGS(last_unsent->tcphdr) & (TCP_SYN | TCP_FIN | TCP_RST)) == 0) { /* no SYN/FIN/RST flag in the header, we can add the FIN flag */ TCPH_SET_FLAG(last_unsent->tcphdr, TCP_FIN); return ERR_OK; } } /* no data, no length, flags, copy=1, no optdata */ return tcp_enqueue_flags(pcb, TCP_FIN); }
/** * Connects to another host. The function given as the "connected" * argument will be called when the connection has been established. * * @param pcb the tcp_pcb used to establish the connection * @param ipaddr the remote ip address to connect to * @param port the remote tcp port to connect to * @param connected callback function to call when connected (or on error) * @return ERR_VAL if invalid arguments are given * ERR_OK if connect request has been sent * other err_t values if connect request couldn't be sent */ err_t tcp_connect(struct tcp_pcb *pcb, ip_addr_t *ipaddr, u16_t port, tcp_connected_fn connected) { err_t ret; u32_t iss; u16_t old_local_port; LWIP_ERROR("tcp_connect: can only connect from state CLOSED", pcb->state == CLOSED, return ERR_ISCONN); LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port)); if (ipaddr != NULL) { pcb->remote_ip = *ipaddr; } else { return ERR_VAL; } pcb->remote_port = port; /* check if we have a route to the remote host */ if (ip_addr_isany(&(pcb->local_ip))) { /* no local IP address set, yet. */ struct netif *netif = ip_route(&(pcb->remote_ip)); if (netif == NULL) { /* Don't even try to send a SYN packet if we have no route since that will fail. */ return ERR_RTE; } /* Use the netif's IP address as local address. */ ip_addr_copy(pcb->local_ip, netif->ip_addr); } old_local_port = pcb->local_port; if (pcb->local_port == 0) { pcb->local_port = tcp_new_port(); } #if SO_REUSE if ((pcb->so_options & SOF_REUSEADDR) != 0) { /* Since SOF_REUSEADDR allows reusing a local address, we have to make sure now that the 5-tuple is unique. */ struct tcp_pcb *cpcb; int i; /* Don't check listen- and bound-PCBs, check active- and TIME-WAIT PCBs. */ for (i = 2; i < NUM_TCP_PCB_LISTS; i++) { for(cpcb = *tcp_pcb_lists[i]; cpcb != NULL; cpcb = cpcb->next) { if ((cpcb->local_port == pcb->local_port) && (cpcb->remote_port == port) && ip_addr_cmp(&cpcb->local_ip, &pcb->local_ip) && ip_addr_cmp(&cpcb->remote_ip, ipaddr)) { /* linux returns EISCONN here, but ERR_USE should be OK for us */ return ERR_USE; } } } } #endif /* SO_REUSE */ iss = tcp_next_iss(); pcb->rcv_nxt = 0; pcb->snd_nxt = iss; pcb->lastack = iss - 1; pcb->snd_lbb = iss - 1; pcb->rcv_wnd = TCP_WND; pcb->rcv_ann_wnd = TCP_WND; pcb->rcv_ann_right_edge = pcb->rcv_nxt; pcb->snd_wnd = TCP_WND; /* As initial send MSS, we use TCP_MSS but limit it to 536. The send MSS is updated when an MSS option is received. */ pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS; #if TCP_CALCULATE_EFF_SEND_MSS pcb->mss = tcp_eff_send_mss(pcb->mss, ipaddr); #endif /* TCP_CALCULATE_EFF_SEND_MSS */ pcb->cwnd = 1; pcb->ssthresh = pcb->mss * 10; #if LWIP_CALLBACK_API pcb->connected = connected; #else /* LWIP_CALLBACK_API */ LWIP_UNUSED_ARG(connected); #endif /* LWIP_CALLBACK_API */ /* Send a SYN together with the MSS option. */ ret = tcp_enqueue_flags(pcb, TCP_SYN); if (ret == ERR_OK) { /* SYN segment was enqueued, changed the pcbs state now */ pcb->state = SYN_SENT; if (old_local_port != 0) { TCP_RMV(&tcp_bound_pcbs, pcb); } TCP_REG(&tcp_active_pcbs, pcb); snmp_inc_tcpactiveopens(); tcp_output(pcb); } return ret; }