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[/] [openrisc/] [trunk/] [rtos/] [freertos-6.1.1/] [Demo/] [lwIP_MCF5235_GCC/] [lwip/] [src/] [core/] [tcp_in.c] - Rev 605
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/** * @file * * Transmission Control Protocol, incoming traffic * * The input processing functions of TCP. * * These functions are generally called in the order (ip_input() ->) tcp_input() -> * tcp_process() -> tcp_receive() (-> application). * */ /* * Copyright (c) 2001-2004 Swedish Institute of Computer Science. * 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. * * This file is part of the lwIP TCP/IP stack. * * Author: Adam Dunkels <adam@sics.se> * */ #include "lwip/def.h" #include "lwip/opt.h" #include "lwip/ip_addr.h" #include "lwip/netif.h" #include "lwip/mem.h" #include "lwip/memp.h" #include "lwip/inet.h" #include "lwip/tcp.h" #include "lwip/stats.h" #include "arch/perf.h" #if LWIP_TCP /* These variables are global to all functions involved in the input processing of TCP segments. They are set by the tcp_input() function. */ static struct tcp_seg inseg; static struct tcp_hdr *tcphdr; static struct ip_hdr *iphdr; static u32_t seqno, ackno; static u8_t flags; static u16_t tcplen; static u8_t recv_flags; static struct pbuf *recv_data; struct tcp_pcb *tcp_input_pcb; /* Forward declarations. */ static err_t tcp_process(struct tcp_pcb *pcb); static void tcp_receive(struct tcp_pcb *pcb); static void tcp_parseopt(struct tcp_pcb *pcb); static err_t tcp_listen_input(struct tcp_pcb_listen *pcb); static err_t tcp_timewait_input(struct tcp_pcb *pcb); /* tcp_input: * * The initial input processing of TCP. It verifies the TCP header, demultiplexes * the segment between the PCBs and passes it on to tcp_process(), which implements * the TCP finite state machine. This function is called by the IP layer (in * ip_input()). */ void tcp_input(struct pbuf *p, struct netif *inp) { struct tcp_pcb *pcb, *prev; struct tcp_pcb_listen *lpcb; u8_t hdrlen; err_t err; PERF_START; TCP_STATS_INC(tcp.recv); iphdr = p->payload; tcphdr = (struct tcp_hdr *)((u8_t *)p->payload + IPH_HL(iphdr) * 4); #if TCP_INPUT_DEBUG tcp_debug_print(tcphdr); #endif /* remove header from payload */ if (pbuf_header(p, -((s16_t)(IPH_HL(iphdr) * 4))) || (p->tot_len < sizeof(struct tcp_hdr))) { /* drop short packets */ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: short packet (%"U16_F" bytes) discarded\n", p->tot_len)); TCP_STATS_INC(tcp.lenerr); TCP_STATS_INC(tcp.drop); pbuf_free(p); return; } /* Don't even process incoming broadcasts/multicasts. */ if (ip_addr_isbroadcast(&(iphdr->dest), inp) || ip_addr_ismulticast(&(iphdr->dest))) { pbuf_free(p); return; } #if CHECKSUM_CHECK_TCP /* Verify TCP checksum. */ if (inet_chksum_pseudo(p, (struct ip_addr *)&(iphdr->src), (struct ip_addr *)&(iphdr->dest), IP_PROTO_TCP, p->tot_len) != 0) { LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: packet discarded due to failing checksum 0x%04"X16_F"\n", inet_chksum_pseudo(p, (struct ip_addr *)&(iphdr->src), (struct ip_addr *)&(iphdr->dest), IP_PROTO_TCP, p->tot_len))); #if TCP_DEBUG tcp_debug_print(tcphdr); #endif /* TCP_DEBUG */ TCP_STATS_INC(tcp.chkerr); TCP_STATS_INC(tcp.drop); pbuf_free(p); return; } #endif /* Move the payload pointer in the pbuf so that it points to the TCP data instead of the TCP header. */ hdrlen = TCPH_HDRLEN(tcphdr); pbuf_header(p, -(hdrlen * 4)); /* Convert fields in TCP header to host byte order. */ tcphdr->src = ntohs(tcphdr->src); tcphdr->dest = ntohs(tcphdr->dest); seqno = tcphdr->seqno = ntohl(tcphdr->seqno); ackno = tcphdr->ackno = ntohl(tcphdr->ackno); tcphdr->wnd = ntohs(tcphdr->wnd); flags = TCPH_FLAGS(tcphdr) & TCP_FLAGS; tcplen = p->tot_len + ((flags & TCP_FIN || flags & TCP_SYN)? 1: 0); /* Demultiplex an incoming segment. First, we check if it is destined for an active connection. */ prev = NULL; for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) { LWIP_ASSERT("tcp_input: active pcb->state != CLOSED", pcb->state != CLOSED); LWIP_ASSERT("tcp_input: active pcb->state != TIME-WAIT", pcb->state != TIME_WAIT); LWIP_ASSERT("tcp_input: active pcb->state != LISTEN", pcb->state != LISTEN); if (pcb->remote_port == tcphdr->src && pcb->local_port == tcphdr->dest && ip_addr_cmp(&(pcb->remote_ip), &(iphdr->src)) && ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest))) { /* Move this PCB to the front of the list so that subsequent lookups will be faster (we exploit locality in TCP segment arrivals). */ LWIP_ASSERT("tcp_input: pcb->next != pcb (before cache)", pcb->next != pcb); if (prev != NULL) { prev->next = pcb->next; pcb->next = tcp_active_pcbs; tcp_active_pcbs = pcb; } LWIP_ASSERT("tcp_input: pcb->next != pcb (after cache)", pcb->next != pcb); break; } prev = pcb; } if (pcb == NULL) { /* If it did not go to an active connection, we check the connections in the TIME-WAIT state. */ for(pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) { LWIP_ASSERT("tcp_input: TIME-WAIT pcb->state == TIME-WAIT", pcb->state == TIME_WAIT); if (pcb->remote_port == tcphdr->src && pcb->local_port == tcphdr->dest && ip_addr_cmp(&(pcb->remote_ip), &(iphdr->src)) && ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest))) { /* We don't really care enough to move this PCB to the front of the list since we are not very likely to receive that many segments for connections in TIME-WAIT. */ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: packed for TIME_WAITing connection.\n")); tcp_timewait_input(pcb); pbuf_free(p); return; } } /* Finally, if we still did not get a match, we check all PCBs that are LISTENing for incoming connections. */ prev = NULL; for(lpcb = tcp_listen_pcbs.listen_pcbs; lpcb != NULL; lpcb = lpcb->next) { if ((ip_addr_isany(&(lpcb->local_ip)) || ip_addr_cmp(&(lpcb->local_ip), &(iphdr->dest))) && lpcb->local_port == tcphdr->dest) { /* Move this PCB to the front of the list so that subsequent lookups will be faster (we exploit locality in TCP segment arrivals). */ if (prev != NULL) { ((struct tcp_pcb_listen *)prev)->next = lpcb->next; /* our successor is the remainder of the listening list */ lpcb->next = tcp_listen_pcbs.listen_pcbs; /* put this listening pcb at the head of the listening list */ tcp_listen_pcbs.listen_pcbs = lpcb; } LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: packed for LISTENing connection.\n")); tcp_listen_input(lpcb); pbuf_free(p); return; } prev = (struct tcp_pcb *)lpcb; } } #if TCP_INPUT_DEBUG LWIP_DEBUGF(TCP_INPUT_DEBUG, ("+-+-+-+-+-+-+-+-+-+-+-+-+-+- tcp_input: flags ")); tcp_debug_print_flags(TCPH_FLAGS(tcphdr)); LWIP_DEBUGF(TCP_INPUT_DEBUG, ("-+-+-+-+-+-+-+-+-+-+-+-+-+-+\n")); #endif /* TCP_INPUT_DEBUG */ if (pcb != NULL) { /* The incoming segment belongs to a connection. */ #if TCP_INPUT_DEBUG #if TCP_DEBUG tcp_debug_print_state(pcb->state); #endif /* TCP_DEBUG */ #endif /* TCP_INPUT_DEBUG */ /* Set up a tcp_seg structure. */ inseg.next = NULL; inseg.len = p->tot_len; inseg.dataptr = p->payload; inseg.p = p; inseg.tcphdr = tcphdr; recv_data = NULL; recv_flags = 0; tcp_input_pcb = pcb; err = tcp_process(pcb); tcp_input_pcb = NULL; /* A return value of ERR_ABRT means that tcp_abort() was called and that the pcb has been freed. If so, we don't do anything. */ if (err != ERR_ABRT) { if (recv_flags & TF_RESET) { /* TF_RESET means that the connection was reset by the other end. We then call the error callback to inform the application that the connection is dead before we deallocate the PCB. */ TCP_EVENT_ERR(pcb->errf, pcb->callback_arg, ERR_RST); tcp_pcb_remove(&tcp_active_pcbs, pcb); memp_free(MEMP_TCP_PCB, pcb); } else if (recv_flags & TF_CLOSED) { /* The connection has been closed and we will deallocate the PCB. */ tcp_pcb_remove(&tcp_active_pcbs, pcb); memp_free(MEMP_TCP_PCB, pcb); } else { err = ERR_OK; /* If the application has registered a "sent" function to be called when new send buffer space is available, we call it now. */ if (pcb->acked > 0) { TCP_EVENT_SENT(pcb, pcb->acked, err); } if (recv_data != NULL) { /* Notify application that data has been received. */ TCP_EVENT_RECV(pcb, recv_data, ERR_OK, err); } /* If a FIN segment was received, we call the callback function with a NULL buffer to indicate EOF. */ if (recv_flags & TF_GOT_FIN) { TCP_EVENT_RECV(pcb, NULL, ERR_OK, err); } /* If there were no errors, we try to send something out. */ if (err == ERR_OK) { tcp_output(pcb); } } } /* We deallocate the incoming pbuf. If it was buffered by the application, the application should have called pbuf_ref() to increase the reference counter in the pbuf. If so, the buffer isn't actually deallocated by the call to pbuf_free(), only the reference count is decreased. */ if (inseg.p != NULL) pbuf_free(inseg.p); #if TCP_INPUT_DEBUG #if TCP_DEBUG tcp_debug_print_state(pcb->state); #endif /* TCP_DEBUG */ #endif /* TCP_INPUT_DEBUG */ } else { /* If no matching PCB was found, send a TCP RST (reset) to the sender. */ LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_input: no PCB match found, resetting.\n")); if (!(TCPH_FLAGS(tcphdr) & TCP_RST)) { TCP_STATS_INC(tcp.proterr); TCP_STATS_INC(tcp.drop); tcp_rst(ackno, seqno + tcplen, &(iphdr->dest), &(iphdr->src), tcphdr->dest, tcphdr->src); } pbuf_free(p); } LWIP_ASSERT("tcp_input: tcp_pcbs_sane()", tcp_pcbs_sane()); PERF_STOP("tcp_input"); } /* tcp_listen_input(): * * Called by tcp_input() when a segment arrives for a listening * connection. */ static err_t tcp_listen_input(struct tcp_pcb_listen *pcb) { struct tcp_pcb *npcb; u32_t optdata; /* In the LISTEN state, we check for incoming SYN segments, creates a new PCB, and responds with a SYN|ACK. */ if (flags & TCP_ACK) { /* For incoming segments with the ACK flag set, respond with a RST. */ LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_listen_input: ACK in LISTEN, sending reset\n")); tcp_rst(ackno + 1, seqno + tcplen, &(iphdr->dest), &(iphdr->src), tcphdr->dest, tcphdr->src); } else if (flags & TCP_SYN) { LWIP_DEBUGF(TCP_DEBUG, ("TCP connection request %"U16_F" -> %"U16_F".\n", tcphdr->src, tcphdr->dest)); npcb = tcp_alloc(pcb->prio); /* If a new PCB could not be created (probably due to lack of memory), we don't do anything, but rely on the sender will retransmit the SYN at a time when we have more memory available. */ if (npcb == NULL) { LWIP_DEBUGF(TCP_DEBUG, ("tcp_listen_input: could not allocate PCB\n")); TCP_STATS_INC(tcp.memerr); return ERR_MEM; } /* Set up the new PCB. */ ip_addr_set(&(npcb->local_ip), &(iphdr->dest)); npcb->local_port = pcb->local_port; ip_addr_set(&(npcb->remote_ip), &(iphdr->src)); npcb->remote_port = tcphdr->src; npcb->state = SYN_RCVD; npcb->rcv_nxt = seqno + 1; npcb->snd_wnd = tcphdr->wnd; npcb->ssthresh = npcb->snd_wnd; npcb->snd_wl1 = seqno - 1;/* initialise to seqno-1 to force window update */ npcb->callback_arg = pcb->callback_arg; #if LWIP_CALLBACK_API npcb->accept = pcb->accept; #endif /* LWIP_CALLBACK_API */ /* inherit socket options */ npcb->so_options = pcb->so_options & (SOF_DEBUG|SOF_DONTROUTE|SOF_KEEPALIVE|SOF_OOBINLINE|SOF_LINGER); /* Register the new PCB so that we can begin receiving segments for it. */ TCP_REG(&tcp_active_pcbs, npcb); /* Parse any options in the SYN. */ tcp_parseopt(npcb); /* Build an MSS option. */ optdata = htonl(((u32_t)2 << 24) | ((u32_t)4 << 16) | (((u32_t)npcb->mss / 256) << 8) | (npcb->mss & 255)); /* Send a SYN|ACK together with the MSS option. */ tcp_enqueue(npcb, NULL, 0, TCP_SYN | TCP_ACK, 0, (u8_t *)&optdata, 4); return tcp_output(npcb); } return ERR_OK; } /* tcp_timewait_input(): * * Called by tcp_input() when a segment arrives for a connection in * TIME_WAIT. */ static err_t tcp_timewait_input(struct tcp_pcb *pcb) { if (TCP_SEQ_GT(seqno + tcplen, pcb->rcv_nxt)) { pcb->rcv_nxt = seqno + tcplen; } if (tcplen > 0) { tcp_ack_now(pcb); } return tcp_output(pcb); } /* tcp_process * * Implements the TCP state machine. Called by tcp_input. In some * states tcp_receive() is called to receive data. The tcp_seg * argument will be freed by the caller (tcp_input()) unless the * recv_data pointer in the pcb is set. */ static err_t tcp_process(struct tcp_pcb *pcb) { struct tcp_seg *rseg; u8_t acceptable = 0; err_t err; err = ERR_OK; /* Process incoming RST segments. */ if (flags & TCP_RST) { /* First, determine if the reset is acceptable. */ if (pcb->state == SYN_SENT) { if (ackno == pcb->snd_nxt) { acceptable = 1; } } else { /*if (TCP_SEQ_GEQ(seqno, pcb->rcv_nxt) && TCP_SEQ_LEQ(seqno, pcb->rcv_nxt + pcb->rcv_wnd)) { */ if (TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, pcb->rcv_nxt+pcb->rcv_wnd)) { acceptable = 1; } } if (acceptable) { LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_process: Connection RESET\n")); LWIP_ASSERT("tcp_input: pcb->state != CLOSED", pcb->state != CLOSED); recv_flags = TF_RESET; pcb->flags &= ~TF_ACK_DELAY; return ERR_RST; } else { LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_process: unacceptable reset seqno %"U32_F" rcv_nxt %"U32_F"\n", seqno, pcb->rcv_nxt)); LWIP_DEBUGF(TCP_DEBUG, ("tcp_process: unacceptable reset seqno %"U32_F" rcv_nxt %"U32_F"\n", seqno, pcb->rcv_nxt)); return ERR_OK; } } /* Update the PCB (in)activity timer. */ pcb->tmr = tcp_ticks; pcb->keep_cnt = 0; /* Do different things depending on the TCP state. */ switch (pcb->state) { case SYN_SENT: LWIP_DEBUGF(TCP_INPUT_DEBUG, ("SYN-SENT: ackno %"U32_F" pcb->snd_nxt %"U32_F" unacked %"U32_F"\n", ackno, pcb->snd_nxt, ntohl(pcb->unacked->tcphdr->seqno))); /* received SYN ACK with expected sequence number? */ if ((flags & TCP_ACK) && (flags & TCP_SYN) && ackno == ntohl(pcb->unacked->tcphdr->seqno) + 1) { pcb->snd_buf++; pcb->rcv_nxt = seqno + 1; pcb->lastack = ackno; pcb->snd_wnd = tcphdr->wnd; pcb->snd_wl1 = seqno - 1; /* initialise to seqno - 1 to force window update */ pcb->state = ESTABLISHED; pcb->cwnd = pcb->mss; --pcb->snd_queuelen; LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_process: SYN-SENT --queuelen %"U16_F"\n", (u16_t)pcb->snd_queuelen)); rseg = pcb->unacked; pcb->unacked = rseg->next; tcp_seg_free(rseg); /* Parse any options in the SYNACK. */ tcp_parseopt(pcb); /* Call the user specified function to call when sucessfully * connected. */ TCP_EVENT_CONNECTED(pcb, ERR_OK, err); tcp_ack(pcb); } /* received ACK? possibly a half-open connection */ else if (flags & TCP_ACK) { /* send a RST to bring the other side in a non-synchronized state. */ tcp_rst(ackno, seqno + tcplen, &(iphdr->dest), &(iphdr->src), tcphdr->dest, tcphdr->src); } break; case SYN_RCVD: if (flags & TCP_ACK && !(flags & TCP_RST)) { /* expected ACK number? */ if (TCP_SEQ_BETWEEN(ackno, pcb->lastack+1, pcb->snd_nxt)) { pcb->state = ESTABLISHED; LWIP_DEBUGF(TCP_DEBUG, ("TCP connection established %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest)); #if LWIP_CALLBACK_API LWIP_ASSERT("pcb->accept != NULL", pcb->accept != NULL); #endif /* Call the accept function. */ TCP_EVENT_ACCEPT(pcb, ERR_OK, err); if (err != ERR_OK) { /* If the accept function returns with an error, we abort * the connection. */ tcp_abort(pcb); return ERR_ABRT; } /* If there was any data contained within this ACK, * we'd better pass it on to the application as well. */ tcp_receive(pcb); pcb->cwnd = pcb->mss; } /* incorrect ACK number */ else { /* send RST */ tcp_rst(ackno, seqno + tcplen, &(iphdr->dest), &(iphdr->src), tcphdr->dest, tcphdr->src); } } break; case CLOSE_WAIT: /* FALLTHROUGH */ case ESTABLISHED: tcp_receive(pcb); if (flags & TCP_FIN) { tcp_ack_now(pcb); pcb->state = CLOSE_WAIT; } break; case FIN_WAIT_1: tcp_receive(pcb); if (flags & TCP_FIN) { if (flags & TCP_ACK && ackno == pcb->snd_nxt) { LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest)); tcp_ack_now(pcb); tcp_pcb_purge(pcb); TCP_RMV(&tcp_active_pcbs, pcb); pcb->state = TIME_WAIT; TCP_REG(&tcp_tw_pcbs, pcb); } else { tcp_ack_now(pcb); pcb->state = CLOSING; } } else if (flags & TCP_ACK && ackno == pcb->snd_nxt) { pcb->state = FIN_WAIT_2; } break; case FIN_WAIT_2: tcp_receive(pcb); if (flags & TCP_FIN) { LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest)); tcp_ack_now(pcb); tcp_pcb_purge(pcb); TCP_RMV(&tcp_active_pcbs, pcb); pcb->state = TIME_WAIT; TCP_REG(&tcp_tw_pcbs, pcb); } break; case CLOSING: tcp_receive(pcb); if (flags & TCP_ACK && ackno == pcb->snd_nxt) { LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest)); tcp_ack_now(pcb); tcp_pcb_purge(pcb); TCP_RMV(&tcp_active_pcbs, pcb); pcb->state = TIME_WAIT; TCP_REG(&tcp_tw_pcbs, pcb); } break; case LAST_ACK: tcp_receive(pcb); if (flags & TCP_ACK && ackno == pcb->snd_nxt) { LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest)); pcb->state = CLOSED; recv_flags = TF_CLOSED; } break; default: break; } return ERR_OK; } /* tcp_receive: * * Called by tcp_process. Checks if the given segment is an ACK for outstanding * data, and if so frees the memory of the buffered data. Next, is places the * segment on any of the receive queues (pcb->recved or pcb->ooseq). If the segment * is buffered, the pbuf is referenced by pbuf_ref so that it will not be freed until * i it has been removed from the buffer. * * If the incoming segment constitutes an ACK for a segment that was used for RTT * estimation, the RTT is estimated here as well. */ static void tcp_receive(struct tcp_pcb *pcb) { struct tcp_seg *next; #if TCP_QUEUE_OOSEQ struct tcp_seg *prev, *cseg; #endif struct pbuf *p; s32_t off; s16_t m; u32_t right_wnd_edge; u16_t new_tot_len; if (flags & TCP_ACK) { right_wnd_edge = pcb->snd_wnd + pcb->snd_wl1; /* Update window. */ if (TCP_SEQ_LT(pcb->snd_wl1, seqno) || (pcb->snd_wl1 == seqno && TCP_SEQ_LT(pcb->snd_wl2, ackno)) || (pcb->snd_wl2 == ackno && tcphdr->wnd > pcb->snd_wnd)) { pcb->snd_wnd = tcphdr->wnd; pcb->snd_wl1 = seqno; pcb->snd_wl2 = ackno; LWIP_DEBUGF(TCP_WND_DEBUG, ("tcp_receive: window update %"U32_F"\n", pcb->snd_wnd)); #if TCP_WND_DEBUG } else { if (pcb->snd_wnd != tcphdr->wnd) { LWIP_DEBUGF(TCP_WND_DEBUG, ("tcp_receive: no window update lastack %"U32_F" snd_max %"U32_F" ackno %"U32_F" wl1 %"U32_F" seqno %"U32_F" wl2 %"U32_F"\n", pcb->lastack, pcb->snd_max, ackno, pcb->snd_wl1, seqno, pcb->snd_wl2)); } #endif /* TCP_WND_DEBUG */ } if (pcb->lastack == ackno) { pcb->acked = 0; if (pcb->snd_wl1 + pcb->snd_wnd == right_wnd_edge){ ++pcb->dupacks; if (pcb->dupacks >= 3 && pcb->unacked != NULL) { if (!(pcb->flags & TF_INFR)) { /* This is fast retransmit. Retransmit the first unacked segment. */ LWIP_DEBUGF(TCP_FR_DEBUG, ("tcp_receive: dupacks %"U16_F" (%"U32_F"), fast retransmit %"U32_F"\n", (u16_t)pcb->dupacks, pcb->lastack, ntohl(pcb->unacked->tcphdr->seqno))); tcp_rexmit(pcb); /* Set ssthresh to max (FlightSize / 2, 2*SMSS) */ /*pcb->ssthresh = LWIP_MAX((pcb->snd_max - pcb->lastack) / 2, 2 * pcb->mss);*/ /* Set ssthresh to half of the minimum of the currenct cwnd and the advertised window */ if(pcb->cwnd > pcb->snd_wnd) pcb->ssthresh = pcb->snd_wnd / 2; else pcb->ssthresh = pcb->cwnd / 2; pcb->cwnd = pcb->ssthresh + 3 * pcb->mss; pcb->flags |= TF_INFR; } else { /* Inflate the congestion window, but not if it means that the value overflows. */ if ((u16_t)(pcb->cwnd + pcb->mss) > pcb->cwnd) { pcb->cwnd += pcb->mss; } } } } else { LWIP_DEBUGF(TCP_FR_DEBUG, ("tcp_receive: dupack averted %"U32_F" %"U32_F"\n", pcb->snd_wl1 + pcb->snd_wnd, right_wnd_edge)); } } else /*if (TCP_SEQ_LT(pcb->lastack, ackno) && TCP_SEQ_LEQ(ackno, pcb->snd_max)) { */ if(TCP_SEQ_BETWEEN(ackno, pcb->lastack+1, pcb->snd_max)){ /* We come here when the ACK acknowledges new data. */ /* Reset the "IN Fast Retransmit" flag, since we are no longer in fast retransmit. Also reset the congestion window to the slow start threshold. */ if (pcb->flags & TF_INFR) { pcb->flags &= ~TF_INFR; pcb->cwnd = pcb->ssthresh; } /* Reset the number of retransmissions. */ pcb->nrtx = 0; /* Reset the retransmission time-out. */ pcb->rto = (pcb->sa >> 3) + pcb->sv; /* Update the send buffer space. */ pcb->acked = ackno - pcb->lastack; pcb->snd_buf += pcb->acked; /* Reset the fast retransmit variables. */ pcb->dupacks = 0; pcb->lastack = ackno; /* Update the congestion control variables (cwnd and ssthresh). */ if (pcb->state >= ESTABLISHED) { if (pcb->cwnd < pcb->ssthresh) { if ((u16_t)(pcb->cwnd + pcb->mss) > pcb->cwnd) { pcb->cwnd += pcb->mss; } LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_receive: slow start cwnd %"U16_F"\n", pcb->cwnd)); } else { u16_t new_cwnd = (pcb->cwnd + pcb->mss * pcb->mss / pcb->cwnd); if (new_cwnd > pcb->cwnd) { pcb->cwnd = new_cwnd; } LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_receive: congestion avoidance cwnd %"U16_F"\n", pcb->cwnd)); } } LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: ACK for %"U32_F", unacked->seqno %"U32_F":%"U32_F"\n", ackno, pcb->unacked != NULL? ntohl(pcb->unacked->tcphdr->seqno): 0, pcb->unacked != NULL? ntohl(pcb->unacked->tcphdr->seqno) + TCP_TCPLEN(pcb->unacked): 0)); /* Remove segment from the unacknowledged list if the incoming ACK acknowlegdes them. */ while (pcb->unacked != NULL && TCP_SEQ_LEQ(ntohl(pcb->unacked->tcphdr->seqno) + TCP_TCPLEN(pcb->unacked), ackno)) { LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: removing %"U32_F":%"U32_F" from pcb->unacked\n", ntohl(pcb->unacked->tcphdr->seqno), ntohl(pcb->unacked->tcphdr->seqno) + TCP_TCPLEN(pcb->unacked))); next = pcb->unacked; pcb->unacked = pcb->unacked->next; LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_receive: queuelen %"U16_F" ... ", (u16_t)pcb->snd_queuelen)); pcb->snd_queuelen -= pbuf_clen(next->p); tcp_seg_free(next); LWIP_DEBUGF(TCP_QLEN_DEBUG, ("%"U16_F" (after freeing unacked)\n", (u16_t)pcb->snd_queuelen)); if (pcb->snd_queuelen != 0) { LWIP_ASSERT("tcp_receive: valid queue length", pcb->unacked != NULL || pcb->unsent != NULL); } } pcb->polltmr = 0; } /* We go through the ->unsent list to see if any of the segments on the list are acknowledged by the ACK. This may seem strange since an "unsent" segment shouldn't be acked. The rationale is that lwIP puts all outstanding segments on the ->unsent list after a retransmission, so these segments may in fact have been sent once. */ while (pcb->unsent != NULL && /*TCP_SEQ_LEQ(ntohl(pcb->unsent->tcphdr->seqno) + TCP_TCPLEN(pcb->unsent), ackno) && TCP_SEQ_LEQ(ackno, pcb->snd_max)*/ TCP_SEQ_BETWEEN(ackno, ntohl(pcb->unsent->tcphdr->seqno) + TCP_TCPLEN(pcb->unsent), pcb->snd_max) ) { LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: removing %"U32_F":%"U32_F" from pcb->unsent\n", ntohl(pcb->unsent->tcphdr->seqno), ntohl(pcb->unsent->tcphdr->seqno) + TCP_TCPLEN(pcb->unsent))); next = pcb->unsent; pcb->unsent = pcb->unsent->next; LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_receive: queuelen %"U16_F" ... ", (u16_t)pcb->snd_queuelen)); pcb->snd_queuelen -= pbuf_clen(next->p); tcp_seg_free(next); LWIP_DEBUGF(TCP_QLEN_DEBUG, ("%"U16_F" (after freeing unsent)\n", (u16_t)pcb->snd_queuelen)); if (pcb->snd_queuelen != 0) { LWIP_ASSERT("tcp_receive: valid queue length", pcb->unacked != NULL || pcb->unsent != NULL); } if (pcb->unsent != NULL) { pcb->snd_nxt = htonl(pcb->unsent->tcphdr->seqno); } } /* End of ACK for new data processing. */ LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_receive: pcb->rttest %"U32_F" rtseq %"U32_F" ackno %"U32_F"\n", pcb->rttest, pcb->rtseq, ackno)); /* RTT estimation calculations. This is done by checking if the incoming segment acknowledges the segment we use to take a round-trip time measurement. */ if (pcb->rttest && TCP_SEQ_LT(pcb->rtseq, ackno)) { m = tcp_ticks - pcb->rttest; LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_receive: experienced rtt %"U16_F" ticks (%"U16_F" msec).\n", m, m * TCP_SLOW_INTERVAL)); /* This is taken directly from VJs original code in his paper */ m = m - (pcb->sa >> 3); pcb->sa += m; if (m < 0) { m = -m; } m = m - (pcb->sv >> 2); pcb->sv += m; pcb->rto = (pcb->sa >> 3) + pcb->sv; LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_receive: RTO %"U16_F" (%"U16_F" miliseconds)\n", pcb->rto, pcb->rto * TCP_SLOW_INTERVAL)); pcb->rttest = 0; } } /* If the incoming segment contains data, we must process it further. */ if (tcplen > 0) { /* This code basically does three things: +) If the incoming segment contains data that is the next in-sequence data, this data is passed to the application. This might involve trimming the first edge of the data. The rcv_nxt variable and the advertised window are adjusted. +) If the incoming segment has data that is above the next sequence number expected (->rcv_nxt), the segment is placed on the ->ooseq queue. This is done by finding the appropriate place in the ->ooseq queue (which is ordered by sequence number) and trim the segment in both ends if needed. An immediate ACK is sent to indicate that we received an out-of-sequence segment. +) Finally, we check if the first segment on the ->ooseq queue now is in sequence (i.e., if rcv_nxt >= ooseq->seqno). If rcv_nxt > ooseq->seqno, we must trim the first edge of the segment on ->ooseq before we adjust rcv_nxt. The data in the segments that are now on sequence are chained onto the incoming segment so that we only need to call the application once. */ /* First, we check if we must trim the first edge. We have to do this if the sequence number of the incoming segment is less than rcv_nxt, and the sequence number plus the length of the segment is larger than rcv_nxt. */ /* if (TCP_SEQ_LT(seqno, pcb->rcv_nxt)){ if (TCP_SEQ_LT(pcb->rcv_nxt, seqno + tcplen)) {*/ if(TCP_SEQ_BETWEEN(pcb->rcv_nxt, seqno+1, seqno+tcplen-1)){ /* Trimming the first edge is done by pushing the payload pointer in the pbuf downwards. This is somewhat tricky since we do not want to discard the full contents of the pbuf up to the new starting point of the data since we have to keep the TCP header which is present in the first pbuf in the chain. What is done is really quite a nasty hack: the first pbuf in the pbuf chain is pointed to by inseg.p. Since we need to be able to deallocate the whole pbuf, we cannot change this inseg.p pointer to point to any of the later pbufs in the chain. Instead, we point the ->payload pointer in the first pbuf to data in one of the later pbufs. We also set the inseg.data pointer to point to the right place. This way, the ->p pointer will still point to the first pbuf, but the ->p->payload pointer will point to data in another pbuf. After we are done with adjusting the pbuf pointers we must adjust the ->data pointer in the seg and the segment length.*/ off = pcb->rcv_nxt - seqno; p = inseg.p; if (inseg.p->len < off) { new_tot_len = inseg.p->tot_len - off; while (p->len < off) { off -= p->len; /* KJM following line changed (with addition of new_tot_len var) to fix bug #9076 inseg.p->tot_len -= p->len; */ p->tot_len = new_tot_len; p->len = 0; p = p->next; } pbuf_header(p, -off); } else { pbuf_header(inseg.p, -off); } /* KJM following line changed to use p->payload rather than inseg->p->payload to fix bug #9076 */ inseg.dataptr = p->payload; inseg.len -= pcb->rcv_nxt - seqno; inseg.tcphdr->seqno = seqno = pcb->rcv_nxt; } else{ if(TCP_SEQ_LT(seqno, pcb->rcv_nxt)){ /* the whole segment is < rcv_nxt */ /* must be a duplicate of a packet that has already been correctly handled */ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: duplicate seqno %"U32_F"\n", seqno)); tcp_ack_now(pcb); } } /* The sequence number must be within the window (above rcv_nxt and below rcv_nxt + rcv_wnd) in order to be further processed. */ /*if (TCP_SEQ_GEQ(seqno, pcb->rcv_nxt) && TCP_SEQ_LT(seqno, pcb->rcv_nxt + pcb->rcv_wnd)) {*/ if(TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, pcb->rcv_nxt + pcb->rcv_wnd - 1)){ if (pcb->rcv_nxt == seqno) { /* The incoming segment is the next in sequence. We check if we have to trim the end of the segment and update rcv_nxt and pass the data to the application. */ #if TCP_QUEUE_OOSEQ if (pcb->ooseq != NULL && TCP_SEQ_LEQ(pcb->ooseq->tcphdr->seqno, seqno + inseg.len)) { /* We have to trim the second edge of the incoming segment. */ inseg.len = pcb->ooseq->tcphdr->seqno - seqno; pbuf_realloc(inseg.p, inseg.len); } #endif /* TCP_QUEUE_OOSEQ */ tcplen = TCP_TCPLEN(&inseg); /* First received FIN will be ACKed +1, on any successive (duplicate) * FINs we are already in CLOSE_WAIT and have already done +1. */ if (pcb->state != CLOSE_WAIT) { pcb->rcv_nxt += tcplen; } /* Update the receiver's (our) window. */ if (pcb->rcv_wnd < tcplen) { pcb->rcv_wnd = 0; } else { pcb->rcv_wnd -= tcplen; } /* If there is data in the segment, we make preparations to pass this up to the application. The ->recv_data variable is used for holding the pbuf that goes to the application. The code for reassembling out-of-sequence data chains its data on this pbuf as well. If the segment was a FIN, we set the TF_GOT_FIN flag that will be used to indicate to the application that the remote side has closed its end of the connection. */ if (inseg.p->tot_len > 0) { recv_data = inseg.p; /* Since this pbuf now is the responsibility of the application, we delete our reference to it so that we won't (mistakingly) deallocate it. */ inseg.p = NULL; } if (TCPH_FLAGS(inseg.tcphdr) & TCP_FIN) { LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: received FIN.\n")); recv_flags = TF_GOT_FIN; } #if TCP_QUEUE_OOSEQ /* We now check if we have segments on the ->ooseq queue that is now in sequence. */ while (pcb->ooseq != NULL && pcb->ooseq->tcphdr->seqno == pcb->rcv_nxt) { cseg = pcb->ooseq; seqno = pcb->ooseq->tcphdr->seqno; pcb->rcv_nxt += TCP_TCPLEN(cseg); if (pcb->rcv_wnd < TCP_TCPLEN(cseg)) { pcb->rcv_wnd = 0; } else { pcb->rcv_wnd -= TCP_TCPLEN(cseg); } if (cseg->p->tot_len > 0) { /* Chain this pbuf onto the pbuf that we will pass to the application. */ if (recv_data) { pbuf_cat(recv_data, cseg->p); } else { recv_data = cseg->p; } cseg->p = NULL; } if (TCPH_FLAGS(cseg->tcphdr) & TCP_FIN) { LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: dequeued FIN.\n")); recv_flags = TF_GOT_FIN; } pcb->ooseq = cseg->next; tcp_seg_free(cseg); } #endif /* TCP_QUEUE_OOSEQ */ /* Acknowledge the segment(s). */ tcp_ack(pcb); } else { /* We get here if the incoming segment is out-of-sequence. */ tcp_ack_now(pcb); #if TCP_QUEUE_OOSEQ /* We queue the segment on the ->ooseq queue. */ if (pcb->ooseq == NULL) { pcb->ooseq = tcp_seg_copy(&inseg); } else { /* If the queue is not empty, we walk through the queue and try to find a place where the sequence number of the incoming segment is between the sequence numbers of the previous and the next segment on the ->ooseq queue. That is the place where we put the incoming segment. If needed, we trim the second edges of the previous and the incoming segment so that it will fit into the sequence. If the incoming segment has the same sequence number as a segment on the ->ooseq queue, we discard the segment that contains less data. */ prev = NULL; for(next = pcb->ooseq; next != NULL; next = next->next) { if (seqno == next->tcphdr->seqno) { /* The sequence number of the incoming segment is the same as the sequence number of the segment on ->ooseq. We check the lengths to see which one to discard. */ if (inseg.len > next->len) { /* The incoming segment is larger than the old segment. We replace the old segment with the new one. */ cseg = tcp_seg_copy(&inseg); if (cseg != NULL) { cseg->next = next->next; if (prev != NULL) { prev->next = cseg; } else { pcb->ooseq = cseg; } } break; } else { /* Either the lenghts are the same or the incoming segment was smaller than the old one; in either case, we ditch the incoming segment. */ break; } } else { if (prev == NULL) { if (TCP_SEQ_LT(seqno, next->tcphdr->seqno)) { /* The sequence number of the incoming segment is lower than the sequence number of the first segment on the queue. We put the incoming segment first on the queue. */ if (TCP_SEQ_GT(seqno + inseg.len, next->tcphdr->seqno)) { /* We need to trim the incoming segment. */ inseg.len = next->tcphdr->seqno - seqno; pbuf_realloc(inseg.p, inseg.len); } cseg = tcp_seg_copy(&inseg); if (cseg != NULL) { cseg->next = next; pcb->ooseq = cseg; } break; } } else /*if (TCP_SEQ_LT(prev->tcphdr->seqno, seqno) && TCP_SEQ_LT(seqno, next->tcphdr->seqno)) {*/ if(TCP_SEQ_BETWEEN(seqno, prev->tcphdr->seqno+1, next->tcphdr->seqno-1)){ /* The sequence number of the incoming segment is in between the sequence numbers of the previous and the next segment on ->ooseq. We trim and insert the incoming segment and trim the previous segment, if needed. */ if (TCP_SEQ_GT(seqno + inseg.len, next->tcphdr->seqno)) { /* We need to trim the incoming segment. */ inseg.len = next->tcphdr->seqno - seqno; pbuf_realloc(inseg.p, inseg.len); } cseg = tcp_seg_copy(&inseg); if (cseg != NULL) { cseg->next = next; prev->next = cseg; if (TCP_SEQ_GT(prev->tcphdr->seqno + prev->len, seqno)) { /* We need to trim the prev segment. */ prev->len = seqno - prev->tcphdr->seqno; pbuf_realloc(prev->p, prev->len); } } break; } /* If the "next" segment is the last segment on the ooseq queue, we add the incoming segment to the end of the list. */ if (next->next == NULL && TCP_SEQ_GT(seqno, next->tcphdr->seqno)) { next->next = tcp_seg_copy(&inseg); if (next->next != NULL) { if (TCP_SEQ_GT(next->tcphdr->seqno + next->len, seqno)) { /* We need to trim the last segment. */ next->len = seqno - next->tcphdr->seqno; pbuf_realloc(next->p, next->len); } } break; } } prev = next; } } #endif /* TCP_QUEUE_OOSEQ */ } } else { /*if (TCP_SEQ_GT(pcb->rcv_nxt, seqno) || TCP_SEQ_GEQ(seqno, pcb->rcv_nxt + pcb->rcv_wnd)) {*/ if(!TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, pcb->rcv_nxt + pcb->rcv_wnd-1)){ tcp_ack_now(pcb); } } } else { /* Segments with length 0 is taken care of here. Segments that fall out of the window are ACKed. */ /*if (TCP_SEQ_GT(pcb->rcv_nxt, seqno) || TCP_SEQ_GEQ(seqno, pcb->rcv_nxt + pcb->rcv_wnd)) {*/ if(!TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, pcb->rcv_nxt + pcb->rcv_wnd-1)){ tcp_ack_now(pcb); } } } /* * tcp_parseopt: * * Parses the options contained in the incoming segment. (Code taken * from uIP with only small changes.) * */ static void tcp_parseopt(struct tcp_pcb *pcb) { u8_t c; u8_t *opts, opt; u16_t mss; opts = (u8_t *)tcphdr + TCP_HLEN; /* Parse the TCP MSS option, if present. */ if(TCPH_HDRLEN(tcphdr) > 0x5) { for(c = 0; c < (TCPH_HDRLEN(tcphdr) - 5) << 2 ;) { opt = opts[c]; if (opt == 0x00) { /* End of options. */ break; } else if (opt == 0x01) { ++c; /* NOP option. */ } else if (opt == 0x02 && opts[c + 1] == 0x04) { /* An MSS option with the right option length. */ mss = (opts[c + 2] << 8) | opts[c + 3]; pcb->mss = mss > TCP_MSS? TCP_MSS: mss; /* And we are done processing options. */ break; } else { if (opts[c + 1] == 0) { /* If the length field is zero, the options are malformed and we don't process them further. */ break; } /* All other options have a length field, so that we easily can skip past them. */ c += opts[c + 1]; } } } } #endif /* LWIP_TCP */
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