/**************************************************************************** * net/tcp/tcp_input.c * Handling incoming TCP input * * Copyright (C) 2007-2014, 2017-2019, 2020 Gregory Nutt. All rights * reserved. * Author: Gregory Nutt * * Adapted for NuttX from logic in uIP which also has a BSD-like license: * * Original author Adam Dunkels * Copyright () 2001-2003, Adam Dunkels. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote * products derived from this software without specific prior * written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #if defined(CONFIG_NET) && defined(CONFIG_NET_TCP) #include #include #include #include #include #include #include #include #include #include #include "devif/devif.h" #include "utils/utils.h" #include "tcp/tcp.h" /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ #define IPv4BUF ((FAR struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)]) #define IPv6BUF ((FAR struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)]) /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: tcp_trim_head * * Description: * Trim the head of the TCP segment. * * Input Parameters: * dev - The device driver structure containing the received TCP * packet. * tcp - The TCP header. * trimlen - The length to trim in bytes. * * Returned Value: * True if nothing was left. * * Assumptions: * The network is locked. * ****************************************************************************/ static bool tcp_trim_head(FAR struct net_driver_s *dev, FAR struct tcp_hdr_s *tcp, uint32_t trimlen) { uint32_t seq = tcp_getsequence(tcp->seqno); uint16_t urg_ptr = (tcp->urgp[0] << 8) | tcp->urgp[1]; uint32_t urg_trimlen = 0; uint8_t th_flags = tcp->flags; DEBUGASSERT(trimlen > 0); ninfo("Dropping %" PRIu32 " bytes: " "seq=%" PRIu32 ", " "tcp flags=%" PRIx8 ", " "d_len=%" PRIu16 ", " "urg_ptr=%" PRIu16 "\n", trimlen, seq, th_flags, dev->d_len, urg_ptr); if ((th_flags & TCP_SYN) != 0) { ninfo("Dropping SYN\n"); seq = TCP_SEQ_ADD(seq, 1); urg_trimlen++; trimlen--; th_flags &= ~TCP_SYN; } if (trimlen > 0) { uint32_t len = trimlen; if (len > dev->d_len) { len = dev->d_len; } ninfo("Dropping %" PRIu32 " bytes app data\n", len); seq = TCP_SEQ_ADD(seq, len); urg_trimlen += len; dev->d_appdata += len; dev->d_len -= len; trimlen -= len; } if (trimlen > 0) { if ((th_flags & TCP_FIN) != 0) { ninfo("Dropping FIN\n"); seq = TCP_SEQ_ADD(seq, 1); urg_trimlen++; trimlen--; th_flags &= ~TCP_FIN; } } /* Update the header */ if ((th_flags & TCP_URG) != 0) { /* Adjust URG pointer */ if (urg_trimlen >= urg_ptr) { th_flags &= ~TCP_URG; urg_ptr = 0; } else { urg_ptr -= urg_trimlen; } ninfo("Adjusting URG pointer by %" PRIu32 ", " "new urg_ptr=%" PRIu16 "\n", urg_trimlen, urg_ptr); tcp->urgp[0] = (uint8_t)(urg_ptr >> 8); tcp->urgp[1] = (uint8_t)urg_ptr; } tcp->flags = th_flags; tcp_setsequence(tcp->seqno, seq); if ((th_flags & (TCP_SYN | TCP_FIN)) == 0 && dev->d_len == 0) { ninfo("Dropped the entire segment\n"); return true; } DEBUGASSERT(trimlen == 0); ninfo("Dropped the segment partially\n"); return false; } static void tcp_snd_wnd_init(FAR struct tcp_conn_s *conn, FAR struct tcp_hdr_s *tcp) { /* Just ensure that the next tcp_update_snd_wnd will be accepted. */ DEBUGASSERT((tcp->flags & TCP_ACK) != 0); conn->snd_wl1 = TCP_SEQ_SUB(tcp_getsequence(tcp->seqno), 1); conn->snd_wl2 = tcp_getsequence(tcp->ackno); conn->snd_wnd = 0; ninfo("snd_wnd init: wl1 %" PRIu32 "\n", conn->snd_wl1); } static void tcp_snd_wnd_update(FAR struct tcp_conn_s *conn, FAR struct tcp_hdr_s *tcp) { uint32_t ackseq = tcp_getsequence(tcp->ackno); uint32_t seq = tcp_getsequence(tcp->seqno); uint16_t unscaled_wnd = ((uint16_t)tcp->wnd[0] << 8) + tcp->wnd[1]; #ifdef CONFIG_NET_TCP_WINDOW_SCALE uint32_t wnd = (uint32_t)unscaled_wnd << conn->snd_scale; #else uint16_t wnd = unscaled_wnd; #endif uint32_t wl2 = conn->snd_wl2; DEBUGASSERT((tcp->flags & TCP_ACK) != 0); if (TCP_SEQ_LT(wl2, ackseq)) { uint32_t nacked = TCP_SEQ_SUB(ackseq, wl2); ninfo("snd_wnd acked: " "wl2 %" PRIu32 " -> %" PRIu32 " subtracting wnd %" PRIu32 " by %" PRIu32 "\n", wl2, ackseq, (uint32_t)conn->snd_wnd, nacked); if (nacked > conn->snd_wnd) { conn->snd_wnd = 0; } else { conn->snd_wnd -= nacked; } conn->snd_wl2 = ackseq; } if (TCP_SEQ_LT(conn->snd_wl1, seq) || (conn->snd_wl1 == seq && TCP_SEQ_LT(wl2, ackseq)) || (wl2 == ackseq && conn->snd_wnd < wnd)) { ninfo("snd_wnd update: " "wl1 %" PRIu32 " wl2 %" PRIu32 " wnd %" PRIu32 " -> " "wl1 %" PRIu32 " wl2 %" PRIu32 " wnd %" PRIu32 "\n", conn->snd_wl1, wl2, (uint32_t)conn->snd_wnd, seq, ackseq, (uint32_t)wnd); conn->snd_wl1 = seq; conn->snd_wl2 = ackseq; conn->snd_wnd = wnd; } } /**************************************************************************** * Name: tcp_input * * Description: * Handle incoming TCP input * * Input Parameters: * dev - The device driver structure containing the received TCP packet. * domain - IP domain (PF_INET or PF_INET6) * iplen - Length of the IP header (IPv4_HDRLEN or IPv6_HDRLEN). * * Returned Value: * None * * Assumptions: * The network is locked. * ****************************************************************************/ static void tcp_input(FAR struct net_driver_s *dev, uint8_t domain, unsigned int iplen) { FAR struct tcp_conn_s *conn = NULL; FAR struct tcp_hdr_s *tcp; union ip_binding_u uaddr; unsigned int tcpiplen; unsigned int hdrlen; uint16_t tmp16; uint16_t flags; uint16_t result; uint8_t opt; int len; int i; #ifdef CONFIG_NET_STATISTICS /* Bump up the count of TCP packets received */ g_netstats.tcp.recv++; #endif /* Get a pointer to the TCP header. The TCP header lies just after the * the link layer header and the IP header. */ tcp = (FAR struct tcp_hdr_s *)&dev->d_buf[iplen + NET_LL_HDRLEN(dev)]; /* Get the size of the IP header and the TCP header. * * REVISIT: TCP header is *not* a constant! It can be larger if the * TCP header includes options. The constant TCP_HDRLEN should be * replaced with the macro TCP_OPT_HDRLEN(n) which will calculate the * correct header length in all cases. */ tcpiplen = iplen + TCP_HDRLEN; /* Get the size of the link layer header, the IP and TCP header */ hdrlen = tcpiplen + NET_LL_HDRLEN(dev); /* Start of TCP input header processing code. */ if (tcp_chksum(dev) != 0xffff) { /* Compute and check the TCP checksum. */ #ifdef CONFIG_NET_STATISTICS g_netstats.tcp.drop++; g_netstats.tcp.chkerr++; #endif nwarn("WARNING: Bad TCP checksum\n"); goto drop; } /* Demultiplex this segment. First check any active connections. */ conn = tcp_active(dev, tcp); if (conn) { /* We found an active connection.. Check for the subsequent SYN * arriving in TCP_SYN_RCVD state after the SYNACK packet was * lost. To avoid other issues, reset any active connection * where a SYN arrives in a state != TCP_SYN_RCVD. */ if ((conn->tcpstateflags & TCP_STATE_MASK) != TCP_SYN_RCVD && (tcp->flags & TCP_CTL) == TCP_SYN) { nwarn("WARNING: SYN in TCP_SYN_RCVD\n"); goto reset; } else { goto found; } } /* If we didn't find an active connection that expected the packet, * either (1) this packet is an old duplicate, or (2) this is a SYN packet * destined for a connection in LISTEN. If the SYN flag isn't set, * it is an old packet and we send a RST. */ if ((tcp->flags & TCP_CTL) == TCP_SYN) { /* This is a SYN packet for a connection. Find the connection * listening on this port. */ tmp16 = tcp->destport; #ifdef CONFIG_NET_IPv6 # ifdef CONFIG_NET_IPv4 if (domain == PF_INET6) # endif { net_ipv6addr_copy(&uaddr.ipv6.laddr, IPv6BUF->destipaddr); } #endif #ifdef CONFIG_NET_IPv4 # ifdef CONFIG_NET_IPv6 if (domain == PF_INET) # endif { net_ipv4addr_copy(uaddr.ipv4.laddr, net_ip4addr_conv32(IPv4BUF->destipaddr)); } #endif #if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6) if (tcp_islistener(&uaddr, tmp16, domain)) #else if (tcp_islistener(&uaddr, tmp16)) #endif { /* We matched the incoming packet with a connection in LISTEN. * We now need to create a new connection and send a SYNACK in * response. */ /* First allocate a new connection structure and see if there is * any user application to accept it. */ conn = tcp_alloc_accept(dev, tcp); if (conn) { /* The connection structure was successfully allocated and has * been initialized in the TCP_SYN_RECVD state. The expected * sequence of events is then the rest of the 3-way handshake: * * 1. We just received a TCP SYN packet from a remote host. * 2. We will send the SYN-ACK response below (perhaps * repeatedly in the event of a timeout) * 3. Then we expect to receive an ACK from the remote host * indicated the TCP socket connection is ESTABLISHED. * * Possible failure: * * 1. The ACK is never received. This will be handled by * a timeout managed by tcp_timer(). * 2. The listener "unlistens()". This will be handled by * the failure of tcp_accept_connection() when the ACK is * received. */ conn->crefs = 1; } if (!conn) { /* Either (1) all available connections are in use, or (2) * there is no application in place to accept the connection. * We drop packet and hope that the remote end will retransmit * the packet at a time when we have more spare connections * or someone waiting to accept the connection. */ #ifdef CONFIG_NET_STATISTICS g_netstats.tcp.syndrop++; #endif nerr("ERROR: No free TCP connections\n"); goto drop; } net_incr32(conn->rcvseq, 1); /* ack SYN */ /* Parse the TCP MSS option, if present. */ if ((tcp->tcpoffset & 0xf0) > 0x50) { for (i = 0; i < ((tcp->tcpoffset >> 4) - 5) << 2 ; ) { opt = dev->d_buf[hdrlen + i]; if (opt == TCP_OPT_END) { /* End of options. */ break; } else if (opt == TCP_OPT_NOOP) { /* NOP option. */ ++i; continue; } else if (opt == TCP_OPT_MSS && dev->d_buf[hdrlen + 1 + i] == TCP_OPT_MSS_LEN) { uint16_t tcp_mss = TCP_MSS(dev, iplen); /* An MSS option with the right option length. */ tmp16 = ((uint16_t)dev->d_buf[hdrlen + 2 + i] << 8) | (uint16_t)dev->d_buf[hdrlen + 3 + i]; conn->mss = tmp16 > tcp_mss ? tcp_mss : tmp16; } #ifdef CONFIG_NET_TCP_WINDOW_SCALE else if (opt == TCP_OPT_WS && dev->d_buf[hdrlen + 1 + i] == TCP_OPT_WS_LEN) { conn->snd_scale = dev->d_buf[hdrlen + 2 + i]; conn->rcv_scale = CONFIG_NET_TCP_WINDOW_SCALE_FACTOR; conn->flags |= TCP_WSCALE; } #endif else { /* All other options have a length field, so that we * easily can skip past them. */ if (dev->d_buf[hdrlen + 1 + i] == 0) { /* If the length field is zero, the options are * malformed and we don't process them further. */ break; } } i += dev->d_buf[hdrlen + 1 + i]; } } /* Our response will be a SYNACK. */ tcp_synack(dev, conn, TCP_ACK | TCP_SYN); return; } } nwarn("WARNING: SYN with no listener (or old packet) .. reset\n"); /* This is (1) an old duplicate packet or (2) a SYN packet but with * no matching listener found. Send RST packet in either case. */ reset: /* We do not send resets in response to resets. */ if ((tcp->flags & TCP_RST) != 0) { goto drop; } #ifdef CONFIG_NET_STATISTICS g_netstats.tcp.synrst++; #endif tcp_reset(dev); return; found: flags = 0; /* We do a very naive form of TCP reset processing; we just accept * any RST and kill our connection. We should in fact check if the * sequence number of this reset is within our advertised window * before we accept the reset. */ if ((tcp->flags & TCP_RST) != 0) { FAR struct tcp_conn_s *listener = NULL; /* An RST received during the 3-way connection handshake requires * little more clean-up. */ if ((conn->tcpstateflags & TCP_STATE_MASK) == TCP_SYN_RCVD) { conn->tcpstateflags = TCP_CLOSED; nwarn("WARNING: RESET in TCP_SYN_RCVD\n"); /* Notify the listener for the connection of the reset event */ #ifdef CONFIG_NET_IPv6 # ifdef CONFIG_NET_IPv4 if (domain == PF_INET6) # endif { net_ipv6addr_copy(&uaddr.ipv6.laddr, IPv6BUF->destipaddr); } #endif #ifdef CONFIG_NET_IPv4 # ifdef CONFIG_NET_IPv6 if (domain == PF_INET) # endif { net_ipv4addr_copy(uaddr.ipv4.laddr, net_ip4addr_conv32(IPv4BUF->destipaddr)); } #endif #if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6) listener = tcp_findlistener(&uaddr, conn->lport, domain); #else listener = tcp_findlistener(&uaddr, conn->lport); #endif /* We must free this TCP connection structure; this connection * will never be established. There should only be one reference * on this connection when we allocated for the connection. */ DEBUGASSERT(conn->crefs == 1); conn->crefs = 0; tcp_free(conn); } else { conn->tcpstateflags = TCP_CLOSED; nwarn("WARNING: RESET TCP state: TCP_CLOSED\n"); /* Notify this connection of the reset event */ listener = conn; } /* Perform the TCP_ABORT callback and drop the packet */ if (listener != NULL) { tcp_callback(dev, listener, TCP_ABORT); } goto drop; } /* Calculated the length of the data, if the application has sent * any data to us. */ len = (tcp->tcpoffset >> 4) << 2; /* d_appdata should remove the tcp specific option field. */ if ((tcp->tcpoffset & 0xf0) > 0x50) { if (dev->d_len >= len) { dev->d_appdata += len - TCP_HDRLEN; } } /* d_len will contain the length of the actual TCP data. This is * calculated by subtracting the length of the TCP header (in * len) and the length of the IP header. */ dev->d_len -= (len + iplen); /* Check if the sequence number of the incoming packet is what we are * expecting next. If not, we send out an ACK with the correct numbers * in, unless we are in the SYN_RCVD state and receive a SYN, in which * case we should retransmit our SYNACK (which is done further down). */ if (!((((conn->tcpstateflags & TCP_STATE_MASK) == TCP_SYN_SENT) && ((tcp->flags & TCP_CTL) == (TCP_SYN | TCP_ACK))) || (((conn->tcpstateflags & TCP_STATE_MASK) == TCP_SYN_RCVD) && ((tcp->flags & TCP_CTL) == TCP_SYN)))) { uint32_t seq; uint32_t rcvseq; seq = tcp_getsequence(tcp->seqno); rcvseq = tcp_getsequence(conn->rcvseq); if (seq != rcvseq) { /* Trim the head of the segment */ if (TCP_SEQ_LT(seq, rcvseq)) { uint32_t trimlen = TCP_SEQ_SUB(rcvseq, seq); if (tcp_trim_head(dev, tcp, trimlen)) { /* The segment was completely out of the window. * E.g. a retransmit which was not necessary. * E.g. a keep-alive segment. */ tcp_send(dev, conn, TCP_ACK, tcpiplen); return; } } else { /* We never queue out-of-order segments. */ tcp_send(dev, conn, TCP_ACK, tcpiplen); return; } } } /* Check if the incoming segment acknowledges any outstanding data. If so, * we update the sequence number, reset the length of the outstanding * data, calculate RTT estimations, and reset the retransmission timer. */ if ((tcp->flags & TCP_ACK) != 0 && conn->tx_unacked > 0) { uint32_t unackseq; uint32_t ackseq; /* The next sequence number is equal to the current sequence * number (sndseq) plus the size of the outstanding, unacknowledged * data (tx_unacked). */ #if defined(CONFIG_NET_TCP_WRITE_BUFFERS) && !defined(CONFIG_NET_SENDFILE) unackseq = conn->sndseq_max; #elif defined(CONFIG_NET_TCP_WRITE_BUFFERS) && defined(CONFIG_NET_SENDFILE) if (!conn->sendfile) { unackseq = conn->sndseq_max; } else { unackseq = tcp_getsequence(conn->sndseq); } #else unackseq = tcp_getsequence(conn->sndseq); #endif /* Get the sequence number of that has just been acknowledged by this * incoming packet. */ ackseq = tcp_getsequence(tcp->ackno); /* Check how many of the outstanding bytes have been acknowledged. For * most send operations, this should always be true. However, * the send() API sends data ahead when it can without waiting for * the ACK. In this case, the 'ackseq' could be less than then the * new sequence number. */ if (TCP_SEQ_LTE(ackseq, unackseq)) { /* Calculate the new number of outstanding, unacknowledged bytes */ conn->tx_unacked = unackseq - ackseq; } else { /* What would it mean if ackseq > unackseq? The peer has ACKed * more bytes than we think we have sent? Someone has lost it. * Complain and reset the number of outstanding, unacknowledged * bytes */ if ((conn->tcpstateflags & TCP_STATE_MASK) == TCP_ESTABLISHED) { nwarn("WARNING: ackseq > unackseq\n"); nwarn("sndseq=%" PRIu32 " tx_unacked=%" PRIu32 " unackseq=%" PRIu32 " ackseq=%" PRIu32 "\n", tcp_getsequence(conn->sndseq), (uint32_t)conn->tx_unacked, unackseq, ackseq); conn->tx_unacked = 0; } } #ifdef CONFIG_NET_TCP_WRITE_BUFFERS #ifdef CONFIG_NET_SENDFILE if (!conn->sendfile) #endif { /* Update sequence number to the unacknowledge sequence number. If * there is still outstanding, unacknowledged data, then this will * be beyond ackseq. */ uint32_t sndseq = tcp_getsequence(conn->sndseq); if (TCP_SEQ_LT(sndseq, ackseq)) { ninfo("sndseq: %08" PRIx32 "->%08" PRIx32 " unackseq: %08" PRIx32 " new tx_unacked: %" PRIu32 "\n", tcp_getsequence(conn->sndseq), ackseq, unackseq, (uint32_t)conn->tx_unacked); tcp_setsequence(conn->sndseq, ackseq); conn->nrtx = 0; } } #endif /* Do RTT estimation, unless we have done retransmissions. */ if (conn->nrtx == 0) { signed char m; m = conn->rto - conn->timer; /* This is taken directly from VJs original code in his paper */ m = m - (conn->sa >> 3); conn->sa += m; if (m < 0) { m = -m; } m = m - (conn->sv >> 2); conn->sv += m; conn->rto = (conn->sa >> 3) + conn->sv; } /* Set the acknowledged flag. */ flags |= TCP_ACKDATA; /* Reset the retransmission timer. */ tcp_update_retrantimer(conn, conn->rto); } /* Update the connection's window size */ if ((tcp->flags & TCP_ACK) != 0 && (conn->tcpstateflags & TCP_STATE_MASK) != TCP_SYN_RCVD) { tcp_snd_wnd_update(conn, tcp); } /* Do different things depending on in what state the connection is. */ switch (conn->tcpstateflags & TCP_STATE_MASK) { /* CLOSED and LISTEN are not handled here. CLOSE_WAIT is not * implemented, since we force the application to close when the * peer sends a FIN (hence the application goes directly from * ESTABLISHED to LAST_ACK). */ case TCP_SYN_RCVD: /* In SYN_RCVD we have sent out a SYNACK in response to a SYN, and * we are waiting for an ACK that acknowledges the data we sent * out the last time. Therefore, we want to have the TCP_ACKDATA * flag set. If so, we enter the ESTABLISHED state. */ if ((flags & TCP_ACKDATA) != 0) { /* The three way handshake is complete and the TCP connection * is now in the ESTABLISHED state. */ conn->tcpstateflags = TCP_ESTABLISHED; /* Wake up any listener waiting for a connection on this port */ if (tcp_accept_connection(dev, conn, tcp->destport) != OK) { /* No more listener for current port. We can free conn here * because it has not been shared with upper layers yet as * handshake is not complete */ nwarn("WARNING: Listen canceled while waiting for ACK on " "port %d\n", NTOHS(tcp->destport)); /* Free the connection structure */ conn->crefs = 0; tcp_free(conn); conn = NULL; /* And send a reset packet to the remote host. */ goto reset; } #ifdef CONFIG_NET_TCP_WRITE_BUFFERS conn->isn = tcp_getsequence(tcp->ackno); tcp_setsequence(conn->sndseq, conn->isn); conn->sent = 0; conn->sndseq_max = 0; #endif conn->tx_unacked = 0; tcp_snd_wnd_init(conn, tcp); tcp_snd_wnd_update(conn, tcp); flags = TCP_CONNECTED; ninfo("TCP state: TCP_ESTABLISHED\n"); if (dev->d_len > 0) { flags |= TCP_NEWDATA; } dev->d_sndlen = 0; result = tcp_callback(dev, conn, flags); tcp_appsend(dev, conn, result); return; } /* We need to retransmit the SYNACK */ if ((tcp->flags & TCP_CTL) == TCP_SYN) { #if !defined(CONFIG_NET_TCP_WRITE_BUFFERS) tcp_setsequence(conn->sndseq, conn->rexmit_seq); #else /* REVISIT for the buffered mode */ #endif tcp_synack(dev, conn, TCP_ACK | TCP_SYN); return; } goto drop; case TCP_SYN_SENT: /* In SYN_SENT, we wait for a SYNACK that is sent in response to * our SYN. The rcvseq is set to sequence number in the SYNACK * plus one, and we send an ACK. We move into the ESTABLISHED * state. */ if ((flags & TCP_ACKDATA) != 0 && (tcp->flags & TCP_CTL) == (TCP_SYN | TCP_ACK)) { /* Parse the TCP MSS option, if present. */ if ((tcp->tcpoffset & 0xf0) > 0x50) { for (i = 0; i < ((tcp->tcpoffset >> 4) - 5) << 2 ; ) { opt = dev->d_buf[hdrlen + i]; if (opt == TCP_OPT_END) { /* End of options. */ break; } else if (opt == TCP_OPT_NOOP) { /* NOP option. */ ++i; continue; } else if (opt == TCP_OPT_MSS && dev->d_buf[hdrlen + 1 + i] == TCP_OPT_MSS_LEN) { uint16_t tcp_mss = TCP_MSS(dev, iplen); /* An MSS option with the right option length. */ tmp16 = (dev->d_buf[hdrlen + 2 + i] << 8) | dev->d_buf[hdrlen + 3 + i]; conn->mss = tmp16 > tcp_mss ? tcp_mss : tmp16; } #ifdef CONFIG_NET_TCP_WINDOW_SCALE else if (opt == TCP_OPT_WS && dev->d_buf[hdrlen + 1 + i] == TCP_OPT_WS_LEN) { conn->snd_scale = dev->d_buf[hdrlen + 2 + i]; conn->rcv_scale = CONFIG_NET_TCP_WINDOW_SCALE_FACTOR; conn->flags |= TCP_WSCALE; } #endif else { /* All other options have a length field, so that we * easily can skip past them. */ if (dev->d_buf[hdrlen + 1 + i] == 0) { /* If the length field is zero, the options are * malformed and we don't process them further. */ break; } } i += dev->d_buf[hdrlen + 1 + i]; } } conn->tcpstateflags = TCP_ESTABLISHED; memcpy(conn->rcvseq, tcp->seqno, 4); conn->rcv_adv = tcp_getsequence(conn->rcvseq); tcp_snd_wnd_init(conn, tcp); tcp_snd_wnd_update(conn, tcp); net_incr32(conn->rcvseq, 1); /* ack SYN */ conn->tx_unacked = 0; #ifdef CONFIG_NET_TCP_WRITE_BUFFERS conn->isn = tcp_getsequence(tcp->ackno); tcp_setsequence(conn->sndseq, conn->isn); #endif dev->d_len = 0; dev->d_sndlen = 0; ninfo("TCP state: TCP_ESTABLISHED\n"); result = tcp_callback(dev, conn, TCP_CONNECTED | TCP_NEWDATA); tcp_appsend(dev, conn, result); return; } /* Inform the application that the connection failed */ tcp_callback(dev, conn, TCP_ABORT); /* The connection is closed after we send the RST */ conn->tcpstateflags = TCP_CLOSED; ninfo("Connection failed - TCP state: TCP_CLOSED\n"); /* We do not send resets in response to resets. */ if ((tcp->flags & TCP_RST) != 0) { goto drop; } tcp_reset(dev); return; case TCP_ESTABLISHED: /* In the ESTABLISHED state, we call upon the application to feed * data into the d_buf. If the TCP_ACKDATA flag is set, the * application should put new data into the buffer, otherwise we are * retransmitting an old segment, and the application should put that * data into the buffer. * * If the incoming packet is a FIN, we should close the connection on * this side as well, and we send out a FIN and enter the LAST_ACK * state. We require that there is no outstanding data; otherwise * the sequence numbers will be screwed up. */ if ((tcp->flags & TCP_FIN) != 0 && (conn->tcpstateflags & TCP_STOPPED) == 0) { /* Needs to be investigated further. * Windows often sends FIN packets together with the last ACK for * the received data. So the socket layer has to get this ACK * even if the connection is going to be closed. */ #if 0 if (conn->tx_unacked > 0) { goto drop; } #endif /* Update the sequence number and indicate that the connection * has been closed. */ flags |= TCP_CLOSE; if (dev->d_len > 0) { flags |= TCP_NEWDATA; } result = tcp_callback(dev, conn, flags); if ((result & TCP_CLOSE) != 0) { conn->tcpstateflags = TCP_LAST_ACK; conn->tx_unacked = 1; conn->nrtx = 0; net_incr32(conn->rcvseq, 1); /* ack FIN */ #ifdef CONFIG_NET_TCP_WRITE_BUFFERS conn->sndseq_max = tcp_getsequence(conn->sndseq) + 1; #endif ninfo("TCP state: TCP_LAST_ACK\n"); tcp_send(dev, conn, TCP_FIN | TCP_ACK, tcpiplen); } else { ninfo("TCP: Dropped a FIN\n"); tcp_appsend(dev, conn, result); } return; } #ifdef CONFIG_NET_TCPURGDATA /* Check the URG flag. If this is set, the segment carries urgent * data that we must pass to the application. */ if ((tcp->flags & TCP_URG) != 0) { dev->d_urglen = (tcp->urgp[0] << 8) | tcp->urgp[1]; if (dev->d_urglen > dev->d_len) { /* There is more urgent data in the next segment to come. */ dev->d_urglen = dev->d_len; } /* The d_len field contains the length of the incoming data. * d_urgdata points to the "urgent" data at the beginning of * the payload; d_appdata field points to the any "normal" data * that may follow the urgent data. * * NOTE: If the urgent data continues in the next packet, then * d_len will be zero and d_appdata will point past the end of * the payload (which is OK). */ net_incr32(conn->rcvseq, dev->d_urglen); dev->d_len -= dev->d_urglen; dev->d_urgdata = dev->d_appdata; dev->d_appdata += dev->d_urglen; } else { /* No urgent data */ dev->d_urglen = 0; } #else /* CONFIG_NET_TCPURGDATA */ /* Check the URG flag. If this is set, We must gracefully ignore * and discard the urgent data. */ if ((tcp->flags & TCP_URG) != 0) { uint16_t urglen = (tcp->urgp[0] << 8) | tcp->urgp[1]; if (urglen > dev->d_len) { /* There is more urgent data in the next segment to come. */ urglen = dev->d_len; } /* The d_len field contains the length of the incoming data; * The d_appdata field points to the any "normal" data that * may follow the urgent data. * * NOTE: If the urgent data continues in the next packet, then * d_len will be zero and d_appdata will point past the end of * the payload (which is OK). */ net_incr32(conn->rcvseq, urglen); dev->d_len -= urglen; dev->d_appdata += urglen; } #endif /* CONFIG_NET_TCPURGDATA */ #ifdef CONFIG_NET_TCP_KEEPALIVE /* If the established socket receives an ACK or any kind of data * from the remote peer (whether we accept it or not), then reset * the keep alive timer. */ if (conn->keepalive && (dev->d_len > 0 || (tcp->flags & TCP_ACK) != 0)) { /* Reset the "alive" timer. */ tcp_update_keeptimer(conn, conn->keepidle); conn->keepretries = 0; } #endif /* If d_len > 0 we have TCP data in the packet, and we flag this * by setting the TCP_NEWDATA flag. If the application has stopped * the data flow using TCP_STOPPED, we must not accept any data * packets from the remote host. */ if (dev->d_len > 0 && (conn->tcpstateflags & TCP_STOPPED) == 0) { flags |= TCP_NEWDATA; } /* If this packet constitutes an ACK for outstanding data (flagged * by the TCP_ACKDATA flag), we should call the application since it * might want to send more data. If the incoming packet had data * from the peer (as flagged by the TCP_NEWDATA flag), the * application must also be notified. * * When the application is called, the d_len field * contains the length of the incoming data. The application can * access the incoming data through the global pointer * d_appdata, which usually points hdrlen bytes into the d_buf * array. * * If the application wishes to send any data, this data should be * put into the d_appdata and the length of the data should be * put into d_len. If the application don't have any data to * send, d_len must be set to 0. */ if ((flags & (TCP_NEWDATA | TCP_ACKDATA)) != 0) { dev->d_sndlen = 0; /* Provide the packet to the application */ result = tcp_callback(dev, conn, flags); /* Send the response, ACKing the data or not, as appropriate */ tcp_appsend(dev, conn, result); return; } goto drop; case TCP_LAST_ACK: /* We can close this connection if the peer has acknowledged our * FIN. This is indicated by the TCP_ACKDATA flag. */ if ((flags & TCP_ACKDATA) != 0) { conn->tcpstateflags = TCP_CLOSED; ninfo("TCP_LAST_ACK TCP state: TCP_CLOSED\n"); tcp_callback(dev, conn, TCP_CLOSE); } break; case TCP_FIN_WAIT_1: /* The application has closed the connection, but the remote host * hasn't closed its end yet. Thus we stay in the FIN_WAIT_1 state * until we receive a FIN from the remote. */ if (dev->d_len > 0) { net_incr32(conn->rcvseq, dev->d_len); } if ((tcp->flags & TCP_FIN) != 0) { if ((flags & TCP_ACKDATA) != 0 && conn->tx_unacked == 0) { conn->tcpstateflags = TCP_TIME_WAIT; tcp_update_retrantimer(conn, TCP_TIME_WAIT_TIMEOUT * HSEC_PER_SEC); ninfo("TCP state: TCP_TIME_WAIT\n"); } else { conn->tcpstateflags = TCP_CLOSING; ninfo("TCP state: TCP_CLOSING\n"); } net_incr32(conn->rcvseq, 1); /* ack FIN */ tcp_callback(dev, conn, TCP_CLOSE); tcp_send(dev, conn, TCP_ACK, tcpiplen); return; } else if ((flags & TCP_ACKDATA) != 0 && conn->tx_unacked == 0) { conn->tcpstateflags = TCP_FIN_WAIT_2; ninfo("TCP state: TCP_FIN_WAIT_2\n"); goto drop; } if (dev->d_len > 0) { tcp_send(dev, conn, TCP_ACK, tcpiplen); return; } goto drop; case TCP_FIN_WAIT_2: if (dev->d_len > 0) { net_incr32(conn->rcvseq, dev->d_len); } if ((tcp->flags & TCP_FIN) != 0) { conn->tcpstateflags = TCP_TIME_WAIT; tcp_update_retrantimer(conn, TCP_TIME_WAIT_TIMEOUT * HSEC_PER_SEC); ninfo("TCP state: TCP_TIME_WAIT\n"); net_incr32(conn->rcvseq, 1); /* ack FIN */ tcp_callback(dev, conn, TCP_CLOSE); tcp_send(dev, conn, TCP_ACK, tcpiplen); return; } if (dev->d_len > 0) { tcp_send(dev, conn, TCP_ACK, tcpiplen); return; } goto drop; case TCP_TIME_WAIT: tcp_send(dev, conn, TCP_ACK, tcpiplen); return; case TCP_CLOSING: if ((flags & TCP_ACKDATA) != 0) { conn->tcpstateflags = TCP_TIME_WAIT; tcp_update_retrantimer(conn, TCP_TIME_WAIT_TIMEOUT * HSEC_PER_SEC); ninfo("TCP state: TCP_TIME_WAIT\n"); } default: break; } drop: dev->d_len = 0; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: tcp_ipv4_input * * Description: * Handle incoming TCP input with IPv4 header * * Input Parameters: * dev - The device driver structure containing the received TCP packet. * * Returned Value: * None * * Assumptions: * Called from the Ethernet driver with the network stack locked * ****************************************************************************/ #ifdef CONFIG_NET_IPv4 void tcp_ipv4_input(FAR struct net_driver_s *dev) { FAR struct ipv4_hdr_s *ipv4 = IPv4BUF; uint16_t iphdrlen; /* Configure to receive an TCP IPv4 packet */ tcp_ipv4_select(dev); /* Get the IP header length (accounting for possible options). */ iphdrlen = (ipv4->vhl & IPv4_HLMASK) << 2; /* Then process in the TCP IPv4 input */ tcp_input(dev, PF_INET, iphdrlen); } #endif /**************************************************************************** * Name: tcp_ipv6_input * * Description: * Handle incoming TCP input with IPv4 header * * Input Parameters: * dev - The device driver structure containing the received TCP packet. * iplen - The size of the IPv6 header. This may be larger than * IPv6_HDRLEN the IPv6 header if IPv6 extension headers are * present. * * Returned Value: * None * * Assumptions: * Called from the Ethernet driver with the network stack locked * ****************************************************************************/ #ifdef CONFIG_NET_IPv6 void tcp_ipv6_input(FAR struct net_driver_s *dev, unsigned int iplen) { /* Configure to receive an TCP IPv6 packet */ tcp_ipv6_select(dev); /* Then process in the TCP IPv6 input */ tcp_input(dev, PF_INET6, iplen); } #endif #endif /* CONFIG_NET && CONFIG_NET_TCP */