Ivan Shindev
V1
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mbed official
Diff: core/tcp_out.c
- Revision:
- 0:51ac1d130fd4
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/core/tcp_out.c Fri Jun 22 09:25:39 2012 +0000
@@ -0,0 +1,1468 @@
+/**
+ * @file
+ * Transmission Control Protocol, outgoing traffic
+ *
+ * The output functions of TCP.
+ *
+ */
+
+/*
+ * 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/opt.h"
+
+#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/tcp_impl.h"
+#include "lwip/def.h"
+#include "lwip/mem.h"
+#include "lwip/memp.h"
+#include "lwip/sys.h"
+#include "lwip/ip_addr.h"
+#include "lwip/netif.h"
+#include "lwip/inet_chksum.h"
+#include "lwip/stats.h"
+#include "lwip/snmp.h"
+
+#include <string.h>
+
+/* Define some copy-macros for checksum-on-copy so that the code looks
+ nicer by preventing too many ifdef's. */
+#if TCP_CHECKSUM_ON_COPY
+#define TCP_DATA_COPY(dst, src, len, seg) do { \
+ tcp_seg_add_chksum(LWIP_CHKSUM_COPY(dst, src, len), \
+ len, &seg->chksum, &seg->chksum_swapped); \
+ seg->flags |= TF_SEG_DATA_CHECKSUMMED; } while(0)
+#define TCP_DATA_COPY2(dst, src, len, chksum, chksum_swapped) \
+ tcp_seg_add_chksum(LWIP_CHKSUM_COPY(dst, src, len), len, chksum, chksum_swapped);
+#else /* TCP_CHECKSUM_ON_COPY*/
+#define TCP_DATA_COPY(dst, src, len, seg) MEMCPY(dst, src, len)
+#define TCP_DATA_COPY2(dst, src, len, chksum, chksum_swapped) MEMCPY(dst, src, len)
+#endif /* TCP_CHECKSUM_ON_COPY*/
+
+/** Define this to 1 for an extra check that the output checksum is valid
+ * (usefule when the checksum is generated by the application, not the stack) */
+#ifndef TCP_CHECKSUM_ON_COPY_SANITY_CHECK
+#define TCP_CHECKSUM_ON_COPY_SANITY_CHECK 0
+#endif
+
+/* Forward declarations.*/
+static void tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb);
+
+/** Allocate a pbuf and create a tcphdr at p->payload, used for output
+ * functions other than the default tcp_output -> tcp_output_segment
+ * (e.g. tcp_send_empty_ack, etc.)
+ *
+ * @param pcb tcp pcb for which to send a packet (used to initialize tcp_hdr)
+ * @param optlen length of header-options
+ * @param datalen length of tcp data to reserve in pbuf
+ * @param seqno_be seqno in network byte order (big-endian)
+ * @return pbuf with p->payload being the tcp_hdr
+ */
+static struct pbuf *
+tcp_output_alloc_header(struct tcp_pcb *pcb, u16_t optlen, u16_t datalen,
+ u32_t seqno_be /* already in network byte order */)
+{
+ struct tcp_hdr *tcphdr;
+ struct pbuf *p = pbuf_alloc(PBUF_IP, TCP_HLEN + optlen + datalen, PBUF_RAM);
+ if (p != NULL) {
+ LWIP_ASSERT("check that first pbuf can hold struct tcp_hdr",
+ (p->len >= TCP_HLEN + optlen));
+ tcphdr = (struct tcp_hdr *)p->payload;
+ tcphdr->src = htons(pcb->local_port);
+ tcphdr->dest = htons(pcb->remote_port);
+ tcphdr->seqno = seqno_be;
+ tcphdr->ackno = htonl(pcb->rcv_nxt);
+ TCPH_HDRLEN_FLAGS_SET(tcphdr, (5 + optlen / 4), TCP_ACK);
+ tcphdr->wnd = htons(pcb->rcv_ann_wnd);
+ tcphdr->chksum = 0;
+ tcphdr->urgp = 0;
+
+ /* If we're sending a packet, update the announced right window edge */
+ pcb->rcv_ann_right_edge = pcb->rcv_nxt + pcb->rcv_ann_wnd;
+ }
+ return p;
+}
+
+/**
+ * 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);
+}
+
+/**
+ * Create a TCP segment with prefilled header.
+ *
+ * Called by tcp_write and tcp_enqueue_flags.
+ *
+ * @param pcb Protocol control block for the TCP connection.
+ * @param p pbuf that is used to hold the TCP header.
+ * @param flags TCP flags for header.
+ * @param seqno TCP sequence number of this packet
+ * @param optflags options to include in TCP header
+ * @return a new tcp_seg pointing to p, or NULL.
+ * The TCP header is filled in except ackno and wnd.
+ * p is freed on failure.
+ */
+static struct tcp_seg *
+tcp_create_segment(struct tcp_pcb *pcb, struct pbuf *p, u8_t flags, u32_t seqno, u8_t optflags)
+{
+ struct tcp_seg *seg;
+ u8_t optlen = LWIP_TCP_OPT_LENGTH(optflags);
+
+ if ((seg = (struct tcp_seg *)memp_malloc(MEMP_TCP_SEG)) == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_create_segment: no memory.\n"));
+ pbuf_free(p);
+ return NULL;
+ }
+ seg->flags = optflags;
+ seg->next = NULL;
+ seg->p = p;
+ seg->len = p->tot_len - optlen;
+#if TCP_OVERSIZE_DBGCHECK
+ seg->oversize_left = 0;
+#endif /* TCP_OVERSIZE_DBGCHECK */
+#if TCP_CHECKSUM_ON_COPY
+ seg->chksum = 0;
+ seg->chksum_swapped = 0;
+ /* check optflags */
+ LWIP_ASSERT("invalid optflags passed: TF_SEG_DATA_CHECKSUMMED",
+ (optflags & TF_SEG_DATA_CHECKSUMMED) == 0);
+#endif /* TCP_CHECKSUM_ON_COPY */
+
+ /* build TCP header */
+ if (pbuf_header(p, TCP_HLEN)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_create_segment: no room for TCP header in pbuf.\n"));
+ TCP_STATS_INC(tcp.err);
+ tcp_seg_free(seg);
+ return NULL;
+ }
+ seg->tcphdr = (struct tcp_hdr *)seg->p->payload;
+ seg->tcphdr->src = htons(pcb->local_port);
+ seg->tcphdr->dest = htons(pcb->remote_port);
+ seg->tcphdr->seqno = htonl(seqno);
+ /* ackno is set in tcp_output */
+ TCPH_HDRLEN_FLAGS_SET(seg->tcphdr, (5 + optlen / 4), flags);
+ /* wnd and chksum are set in tcp_output */
+ seg->tcphdr->urgp = 0;
+ return seg;
+}
+
+/**
+ * Allocate a PBUF_RAM pbuf, perhaps with extra space at the end.
+ *
+ * This function is like pbuf_alloc(layer, length, PBUF_RAM) except
+ * there may be extra bytes available at the end.
+ *
+ * @param layer flag to define header size.
+ * @param length size of the pbuf's payload.
+ * @param max_length maximum usable size of payload+oversize.
+ * @param oversize pointer to a u16_t that will receive the number of usable tail bytes.
+ * @param pcb The TCP connection that willo enqueue the pbuf.
+ * @param apiflags API flags given to tcp_write.
+ * @param first_seg true when this pbuf will be used in the first enqueued segment.
+ * @param
+ */
+#if TCP_OVERSIZE
+static struct pbuf *
+tcp_pbuf_prealloc(pbuf_layer layer, u16_t length, u16_t max_length,
+ u16_t *oversize, struct tcp_pcb *pcb, u8_t apiflags,
+ u8_t first_seg)
+{
+ struct pbuf *p;
+ u16_t alloc = length;
+
+#if LWIP_NETIF_TX_SINGLE_PBUF
+ LWIP_UNUSED_ARG(max_length);
+ LWIP_UNUSED_ARG(pcb);
+ LWIP_UNUSED_ARG(apiflags);
+ LWIP_UNUSED_ARG(first_seg);
+ /* always create MSS-sized pbufs */
+ alloc = TCP_MSS;
+#else /* LWIP_NETIF_TX_SINGLE_PBUF */
+ if (length < max_length) {
+ /* Should we allocate an oversized pbuf, or just the minimum
+ * length required? If tcp_write is going to be called again
+ * before this segment is transmitted, we want the oversized
+ * buffer. If the segment will be transmitted immediately, we can
+ * save memory by allocating only length. We use a simple
+ * heuristic based on the following information:
+ *
+ * Did the user set TCP_WRITE_FLAG_MORE?
+ *
+ * Will the Nagle algorithm defer transmission of this segment?
+ */
+ if ((apiflags & TCP_WRITE_FLAG_MORE) ||
+ (!(pcb->flags & TF_NODELAY) &&
+ (!first_seg ||
+ pcb->unsent != NULL ||
+ pcb->unacked != NULL))) {
+ alloc = LWIP_MIN(max_length, LWIP_MEM_ALIGN_SIZE(length + TCP_OVERSIZE));
+ }
+ }
+#endif /* LWIP_NETIF_TX_SINGLE_PBUF */
+ p = pbuf_alloc(layer, alloc, PBUF_RAM);
+ if (p == NULL) {
+ return NULL;
+ }
+ LWIP_ASSERT("need unchained pbuf", p->next == NULL);
+ *oversize = p->len - length;
+ /* trim p->len to the currently used size */
+ p->len = p->tot_len = length;
+ return p;
+}
+#else /* TCP_OVERSIZE */
+#define tcp_pbuf_prealloc(layer, length, mx, os, pcb, api, fst) pbuf_alloc((layer), (length), PBUF_RAM)
+#endif /* TCP_OVERSIZE */
+
+#if TCP_CHECKSUM_ON_COPY
+/** Add a checksum of newly added data to the segment */
+static void
+tcp_seg_add_chksum(u16_t chksum, u16_t len, u16_t *seg_chksum,
+ u8_t *seg_chksum_swapped)
+{
+ u32_t helper;
+ /* add chksum to old chksum and fold to u16_t */
+ helper = chksum + *seg_chksum;
+ chksum = FOLD_U32T(helper);
+ if ((len & 1) != 0) {
+ *seg_chksum_swapped = 1 - *seg_chksum_swapped;
+ chksum = SWAP_BYTES_IN_WORD(chksum);
+ }
+ *seg_chksum = chksum;
+}
+#endif /* TCP_CHECKSUM_ON_COPY */
+
+/** Checks if tcp_write is allowed or not (checks state, snd_buf and snd_queuelen).
+ *
+ * @param pcb the tcp pcb to check for
+ * @param len length of data to send (checked agains snd_buf)
+ * @return ERR_OK if tcp_write is allowed to proceed, another err_t otherwise
+ */
+static err_t
+tcp_write_checks(struct tcp_pcb *pcb, u16_t len)
+{
+ /* connection is in invalid state for data transmission? */
+ if ((pcb->state != ESTABLISHED) &&
+ (pcb->state != CLOSE_WAIT) &&
+ (pcb->state != SYN_SENT) &&
+ (pcb->state != SYN_RCVD)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_STATE | LWIP_DBG_LEVEL_SEVERE, ("tcp_write() called in invalid state\n"));
+ return ERR_CONN;
+ } else if (len == 0) {
+ return ERR_OK;
+ }
+
+ /* fail on too much data */
+ if (len > pcb->snd_buf) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_write: too much data (len=%"U16_F" > snd_buf=%"U16_F")\n",
+ len, pcb->snd_buf));
+ pcb->flags |= TF_NAGLEMEMERR;
+ return ERR_MEM;
+ }
+
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_write: queuelen: %"U16_F"\n", (u16_t)pcb->snd_queuelen));
+
+ /* If total number of pbufs on the unsent/unacked queues exceeds the
+ * configured maximum, return an error */
+ /* check for configured max queuelen and possible overflow */
+ if ((pcb->snd_queuelen >= TCP_SND_QUEUELEN) || (pcb->snd_queuelen > TCP_SNDQUEUELEN_OVERFLOW)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_write: too long queue %"U16_F" (max %"U16_F")\n",
+ pcb->snd_queuelen, TCP_SND_QUEUELEN));
+ TCP_STATS_INC(tcp.memerr);
+ pcb->flags |= TF_NAGLEMEMERR;
+ return ERR_MEM;
+ }
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_write: pbufs on queue => at least one queue non-empty",
+ pcb->unacked != NULL || pcb->unsent != NULL);
+ } else {
+ LWIP_ASSERT("tcp_write: no pbufs on queue => both queues empty",
+ pcb->unacked == NULL && pcb->unsent == NULL);
+ }
+ return ERR_OK;
+}
+
+/**
+ * Write data for sending (but does not send it immediately).
+ *
+ * It waits in the expectation of more data being sent soon (as
+ * it can send them more efficiently by combining them together).
+ * To prompt the system to send data now, call tcp_output() after
+ * calling tcp_write().
+ *
+ * @param pcb Protocol control block for the TCP connection to enqueue data for.
+ * @param arg Pointer to the data to be enqueued for sending.
+ * @param len Data length in bytes
+ * @param apiflags combination of following flags :
+ * - TCP_WRITE_FLAG_COPY (0x01) data will be copied into memory belonging to the stack
+ * - TCP_WRITE_FLAG_MORE (0x02) for TCP connection, PSH flag will be set on last segment sent,
+ * @return ERR_OK if enqueued, another err_t on error
+ */
+err_t
+tcp_write(struct tcp_pcb *pcb, const void *arg, u16_t len, u8_t apiflags)
+{
+ struct pbuf *concat_p = NULL;
+ struct tcp_seg *last_unsent = NULL, *seg = NULL, *prev_seg = NULL, *queue = NULL;
+ u16_t pos = 0; /* position in 'arg' data */
+ u16_t queuelen;
+ u8_t optlen = 0;
+ u8_t optflags = 0;
+#if TCP_OVERSIZE
+ u16_t oversize = 0;
+ u16_t oversize_used = 0;
+#endif /* TCP_OVERSIZE */
+#if TCP_CHECKSUM_ON_COPY
+ u16_t concat_chksum = 0;
+ u8_t concat_chksum_swapped = 0;
+ u16_t concat_chksummed = 0;
+#endif /* TCP_CHECKSUM_ON_COPY */
+ err_t err;
+
+#if LWIP_NETIF_TX_SINGLE_PBUF
+ /* Always copy to try to create single pbufs for TX */
+ apiflags |= TCP_WRITE_FLAG_COPY;
+#endif /* LWIP_NETIF_TX_SINGLE_PBUF */
+
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_write(pcb=%p, data=%p, len=%"U16_F", apiflags=%"U16_F")\n",
+ (void *)pcb, arg, len, (u16_t)apiflags));
+ LWIP_ERROR("tcp_write: arg == NULL (programmer violates API)",
+ arg != NULL, return ERR_ARG;);
+
+ err = tcp_write_checks(pcb, len);
+ if (err != ERR_OK) {
+ return err;
+ }
+ queuelen = pcb->snd_queuelen;
+
+#if LWIP_TCP_TIMESTAMPS
+ if ((pcb->flags & TF_TIMESTAMP)) {
+ optflags = TF_SEG_OPTS_TS;
+ optlen = LWIP_TCP_OPT_LENGTH(TF_SEG_OPTS_TS);
+ }
+#endif /* LWIP_TCP_TIMESTAMPS */
+
+
+ /*
+ * TCP segmentation is done in three phases with increasing complexity:
+ *
+ * 1. Copy data directly into an oversized pbuf.
+ * 2. Chain a new pbuf to the end of pcb->unsent.
+ * 3. Create new segments.
+ *
+ * We may run out of memory at any point. In that case we must
+ * return ERR_MEM and not change anything in pcb. Therefore, all
+ * changes are recorded in local variables and committed at the end
+ * of the function. Some pcb fields are maintained in local copies:
+ *
+ * queuelen = pcb->snd_queuelen
+ * oversize = pcb->unsent_oversize
+ *
+ * These variables are set consistently by the phases:
+ *
+ * seg points to the last segment tampered with.
+ *
+ * pos records progress as data is segmented.
+ */
+
+ /* Find the tail of the unsent queue. */
+ if (pcb->unsent != NULL) {
+ u16_t space;
+ u16_t unsent_optlen;
+
+ /* @todo: this could be sped up by keeping last_unsent in the pcb */
+ for (last_unsent = pcb->unsent; last_unsent->next != NULL;
+ last_unsent = last_unsent->next);
+
+ /* Usable space at the end of the last unsent segment */
+ unsent_optlen = LWIP_TCP_OPT_LENGTH(last_unsent->flags);
+ space = pcb->mss - (last_unsent->len + unsent_optlen);
+
+ /*
+ * Phase 1: Copy data directly into an oversized pbuf.
+ *
+ * The number of bytes copied is recorded in the oversize_used
+ * variable. The actual copying is done at the bottom of the
+ * function.
+ */
+#if TCP_OVERSIZE
+#if TCP_OVERSIZE_DBGCHECK
+ /* check that pcb->unsent_oversize matches last_unsent->unsent_oversize */
+ LWIP_ASSERT("unsent_oversize mismatch (pcb vs. last_unsent)",
+ pcb->unsent_oversize == last_unsent->oversize_left);
+#endif /* TCP_OVERSIZE_DBGCHECK */
+ oversize = pcb->unsent_oversize;
+ if (oversize > 0) {
+ LWIP_ASSERT("inconsistent oversize vs. space", oversize_used <= space);
+ seg = last_unsent;
+ oversize_used = oversize < len ? oversize : len;
+ pos += oversize_used;
+ oversize -= oversize_used;
+ space -= oversize_used;
+ }
+ /* now we are either finished or oversize is zero */
+ LWIP_ASSERT("inconsistend oversize vs. len", (oversize == 0) || (pos == len));
+#endif /* TCP_OVERSIZE */
+
+ /*
+ * Phase 2: Chain a new pbuf to the end of pcb->unsent.
+ *
+ * We don't extend segments containing SYN/FIN flags or options
+ * (len==0). The new pbuf is kept in concat_p and pbuf_cat'ed at
+ * the end.
+ */
+ if ((pos < len) && (space > 0) && (last_unsent->len > 0)) {
+ u16_t seglen = space < len - pos ? space : len - pos;
+ seg = last_unsent;
+
+ /* Create a pbuf with a copy or reference to seglen bytes. We
+ * can use PBUF_RAW here since the data appears in the middle of
+ * a segment. A header will never be prepended. */
+ if (apiflags & TCP_WRITE_FLAG_COPY) {
+ /* Data is copied */
+ if ((concat_p = tcp_pbuf_prealloc(PBUF_RAW, seglen, space, &oversize, pcb, apiflags, 1)) == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2,
+ ("tcp_write : could not allocate memory for pbuf copy size %"U16_F"\n",
+ seglen));
+ goto memerr;
+ }
+#if TCP_OVERSIZE_DBGCHECK
+ last_unsent->oversize_left = oversize;
+#endif /* TCP_OVERSIZE_DBGCHECK */
+ TCP_DATA_COPY2(concat_p->payload, (u8_t*)arg + pos, seglen, &concat_chksum, &concat_chksum_swapped);
+#if TCP_CHECKSUM_ON_COPY
+ concat_chksummed += seglen;
+#endif /* TCP_CHECKSUM_ON_COPY */
+ } else {
+ /* Data is not copied */
+ if ((concat_p = pbuf_alloc(PBUF_RAW, seglen, PBUF_ROM)) == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2,
+ ("tcp_write: could not allocate memory for zero-copy pbuf\n"));
+ goto memerr;
+ }
+#if TCP_CHECKSUM_ON_COPY
+ /* calculate the checksum of nocopy-data */
+ tcp_seg_add_chksum(~inet_chksum((u8_t*)arg + pos, seglen), seglen,
+ &concat_chksum, &concat_chksum_swapped);
+ concat_chksummed += seglen;
+#endif /* TCP_CHECKSUM_ON_COPY */
+ /* reference the non-volatile payload data */
+ concat_p->payload = (u8_t*)arg + pos;
+ }
+
+ pos += seglen;
+ queuelen += pbuf_clen(concat_p);
+ }
+ } else {
+#if TCP_OVERSIZE
+ LWIP_ASSERT("unsent_oversize mismatch (pcb->unsent is NULL)",
+ pcb->unsent_oversize == 0);
+#endif /* TCP_OVERSIZE */
+ }
+
+ /*
+ * Phase 3: Create new segments.
+ *
+ * The new segments are chained together in the local 'queue'
+ * variable, ready to be appended to pcb->unsent.
+ */
+ while (pos < len) {
+ struct pbuf *p;
+ u16_t left = len - pos;
+ u16_t max_len = pcb->mss - optlen;
+ u16_t seglen = left > max_len ? max_len : left;
+#if TCP_CHECKSUM_ON_COPY
+ u16_t chksum = 0;
+ u8_t chksum_swapped = 0;
+#endif /* TCP_CHECKSUM_ON_COPY */
+
+ if (apiflags & TCP_WRITE_FLAG_COPY) {
+ /* If copy is set, memory should be allocated and data copied
+ * into pbuf */
+ if ((p = tcp_pbuf_prealloc(PBUF_TRANSPORT, seglen + optlen, pcb->mss, &oversize, pcb, apiflags, queue == NULL)) == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_write : could not allocate memory for pbuf copy size %"U16_F"\n", seglen));
+ goto memerr;
+ }
+ LWIP_ASSERT("tcp_write: check that first pbuf can hold the complete seglen",
+ (p->len >= seglen));
+ TCP_DATA_COPY2((char *)p->payload + optlen, (u8_t*)arg + pos, seglen, &chksum, &chksum_swapped);
+ } else {
+ /* Copy is not set: First allocate a pbuf for holding the data.
+ * Since the referenced data is available at least until it is
+ * sent out on the link (as it has to be ACKed by the remote
+ * party) we can safely use PBUF_ROM instead of PBUF_REF here.
+ */
+ struct pbuf *p2;
+#if TCP_OVERSIZE
+ LWIP_ASSERT("oversize == 0", oversize == 0);
+#endif /* TCP_OVERSIZE */
+ if ((p2 = pbuf_alloc(PBUF_TRANSPORT, seglen, PBUF_ROM)) == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_write: could not allocate memory for zero-copy pbuf\n"));
+ goto memerr;
+ }
+#if TCP_CHECKSUM_ON_COPY
+ /* calculate the checksum of nocopy-data */
+ chksum = ~inet_chksum((u8_t*)arg + pos, seglen);
+#endif /* TCP_CHECKSUM_ON_COPY */
+ /* reference the non-volatile payload data */
+ p2->payload = (u8_t*)arg + pos;
+
+ /* Second, allocate a pbuf for the headers. */
+ if ((p = pbuf_alloc(PBUF_TRANSPORT, optlen, PBUF_RAM)) == NULL) {
+ /* If allocation fails, we have to deallocate the data pbuf as
+ * well. */
+ pbuf_free(p2);
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_write: could not allocate memory for header pbuf\n"));
+ goto memerr;
+ }
+ /* Concatenate the headers and data pbufs together. */
+ pbuf_cat(p/*header*/, p2/*data*/);
+ }
+
+ queuelen += pbuf_clen(p);
+
+ /* Now that there are more segments queued, we check again if the
+ * length of the queue exceeds the configured maximum or
+ * overflows. */
+ if ((queuelen > TCP_SND_QUEUELEN) || (queuelen > TCP_SNDQUEUELEN_OVERFLOW)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_write: queue too long %"U16_F" (%"U16_F")\n", queuelen, TCP_SND_QUEUELEN));
+ pbuf_free(p);
+ goto memerr;
+ }
+
+ if ((seg = tcp_create_segment(pcb, p, 0, pcb->snd_lbb + pos, optflags)) == NULL) {
+ goto memerr;
+ }
+#if TCP_OVERSIZE_DBGCHECK
+ seg->oversize_left = oversize;
+#endif /* TCP_OVERSIZE_DBGCHECK */
+#if TCP_CHECKSUM_ON_COPY
+ seg->chksum = chksum;
+ seg->chksum_swapped = chksum_swapped;
+ seg->flags |= TF_SEG_DATA_CHECKSUMMED;
+#endif /* TCP_CHECKSUM_ON_COPY */
+
+ /* first segment of to-be-queued data? */
+ if (queue == NULL) {
+ queue = seg;
+ } else {
+ /* Attach the segment to the end of the queued segments */
+ LWIP_ASSERT("prev_seg != NULL", prev_seg != NULL);
+ prev_seg->next = seg;
+ }
+ /* remember last segment of to-be-queued data for next iteration */
+ prev_seg = seg;
+
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_TRACE, ("tcp_write: queueing %"U32_F":%"U32_F"\n",
+ ntohl(seg->tcphdr->seqno),
+ ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg)));
+
+ pos += seglen;
+ }
+
+ /*
+ * All three segmentation phases were successful. We can commit the
+ * transaction.
+ */
+
+ /*
+ * Phase 1: If data has been added to the preallocated tail of
+ * last_unsent, we update the length fields of the pbuf chain.
+ */
+#if TCP_OVERSIZE
+ if (oversize_used > 0) {
+ struct pbuf *p;
+ /* Bump tot_len of whole chain, len of tail */
+ for (p = last_unsent->p; p; p = p->next) {
+ p->tot_len += oversize_used;
+ if (p->next == NULL) {
+ TCP_DATA_COPY((char *)p->payload + p->len, arg, oversize_used, last_unsent);
+ p->len += oversize_used;
+ }
+ }
+ last_unsent->len += oversize_used;
+#if TCP_OVERSIZE_DBGCHECK
+ last_unsent->oversize_left -= oversize_used;
+#endif /* TCP_OVERSIZE_DBGCHECK */
+ }
+ pcb->unsent_oversize = oversize;
+#endif /* TCP_OVERSIZE */
+
+ /*
+ * Phase 2: concat_p can be concatenated onto last_unsent->p
+ */
+ if (concat_p != NULL) {
+ LWIP_ASSERT("tcp_write: cannot concatenate when pcb->unsent is empty",
+ (last_unsent != NULL));
+ pbuf_cat(last_unsent->p, concat_p);
+ last_unsent->len += concat_p->tot_len;
+#if TCP_CHECKSUM_ON_COPY
+ if (concat_chksummed) {
+ tcp_seg_add_chksum(concat_chksum, concat_chksummed, &last_unsent->chksum,
+ &last_unsent->chksum_swapped);
+ last_unsent->flags |= TF_SEG_DATA_CHECKSUMMED;
+ }
+#endif /* TCP_CHECKSUM_ON_COPY */
+ }
+
+ /*
+ * Phase 3: Append queue to pcb->unsent. Queue may be NULL, but that
+ * is harmless
+ */
+ if (last_unsent == NULL) {
+ pcb->unsent = queue;
+ } else {
+ last_unsent->next = queue;
+ }
+
+ /*
+ * Finally update the pcb state.
+ */
+ pcb->snd_lbb += len;
+ pcb->snd_buf -= len;
+ pcb->snd_queuelen = queuelen;
+
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_write: %"S16_F" (after enqueued)\n",
+ pcb->snd_queuelen));
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_write: valid queue length",
+ pcb->unacked != NULL || pcb->unsent != NULL);
+ }
+
+ /* Set the PSH flag in the last segment that we enqueued. */
+ if (seg != NULL && seg->tcphdr != NULL && ((apiflags & TCP_WRITE_FLAG_MORE)==0)) {
+ TCPH_SET_FLAG(seg->tcphdr, TCP_PSH);
+ }
+
+ return ERR_OK;
+memerr:
+ pcb->flags |= TF_NAGLEMEMERR;
+ TCP_STATS_INC(tcp.memerr);
+
+ if (concat_p != NULL) {
+ pbuf_free(concat_p);
+ }
+ if (queue != NULL) {
+ tcp_segs_free(queue);
+ }
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_write: valid queue length", pcb->unacked != NULL ||
+ pcb->unsent != NULL);
+ }
+ LWIP_DEBUGF(TCP_QLEN_DEBUG | LWIP_DBG_STATE, ("tcp_write: %"S16_F" (with mem err)\n", pcb->snd_queuelen));
+ return ERR_MEM;
+}
+
+/**
+ * Enqueue TCP options for transmission.
+ *
+ * Called by tcp_connect(), tcp_listen_input(), and tcp_send_ctrl().
+ *
+ * @param pcb Protocol control block for the TCP connection.
+ * @param flags TCP header flags to set in the outgoing segment.
+ * @param optdata pointer to TCP options, or NULL.
+ * @param optlen length of TCP options in bytes.
+ */
+err_t
+tcp_enqueue_flags(struct tcp_pcb *pcb, u8_t flags)
+{
+ struct pbuf *p;
+ struct tcp_seg *seg;
+ u8_t optflags = 0;
+ u8_t optlen = 0;
+
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue_flags: queuelen: %"U16_F"\n", (u16_t)pcb->snd_queuelen));
+
+ LWIP_ASSERT("tcp_enqueue_flags: need either TCP_SYN or TCP_FIN in flags (programmer violates API)",
+ (flags & (TCP_SYN | TCP_FIN)) != 0);
+
+ /* check for configured max queuelen and possible overflow */
+ if ((pcb->snd_queuelen >= TCP_SND_QUEUELEN) || (pcb->snd_queuelen > TCP_SNDQUEUELEN_OVERFLOW)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue_flags: too long queue %"U16_F" (max %"U16_F")\n",
+ pcb->snd_queuelen, TCP_SND_QUEUELEN));
+ TCP_STATS_INC(tcp.memerr);
+ pcb->flags |= TF_NAGLEMEMERR;
+ return ERR_MEM;
+ }
+
+ if (flags & TCP_SYN) {
+ optflags = TF_SEG_OPTS_MSS;
+ }
+#if LWIP_TCP_TIMESTAMPS
+ if ((pcb->flags & TF_TIMESTAMP)) {
+ optflags |= TF_SEG_OPTS_TS;
+ }
+#endif /* LWIP_TCP_TIMESTAMPS */
+ optlen = LWIP_TCP_OPT_LENGTH(optflags);
+
+ /* tcp_enqueue_flags is always called with either SYN or FIN in flags.
+ * We need one available snd_buf byte to do that.
+ * This means we can't send FIN while snd_buf==0. A better fix would be to
+ * not include SYN and FIN sequence numbers in the snd_buf count. */
+ if (pcb->snd_buf == 0) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue_flags: no send buffer available\n"));
+ TCP_STATS_INC(tcp.memerr);
+ return ERR_MEM;
+ }
+
+ /* Allocate pbuf with room for TCP header + options */
+ if ((p = pbuf_alloc(PBUF_TRANSPORT, optlen, PBUF_RAM)) == NULL) {
+ pcb->flags |= TF_NAGLEMEMERR;
+ TCP_STATS_INC(tcp.memerr);
+ return ERR_MEM;
+ }
+ LWIP_ASSERT("tcp_enqueue_flags: check that first pbuf can hold optlen",
+ (p->len >= optlen));
+
+ /* Allocate memory for tcp_seg, and fill in fields. */
+ if ((seg = tcp_create_segment(pcb, p, flags, pcb->snd_lbb, optflags)) == NULL) {
+ pcb->flags |= TF_NAGLEMEMERR;
+ TCP_STATS_INC(tcp.memerr);
+ return ERR_MEM;
+ }
+ LWIP_ASSERT("seg->tcphdr not aligned", ((mem_ptr_t)seg->tcphdr % MEM_ALIGNMENT) == 0);
+ LWIP_ASSERT("tcp_enqueue_flags: invalid segment length", seg->len == 0);
+
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_TRACE,
+ ("tcp_enqueue_flags: queueing %"U32_F":%"U32_F" (0x%"X16_F")\n",
+ ntohl(seg->tcphdr->seqno),
+ ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg),
+ (u16_t)flags));
+
+ /* Now append seg to pcb->unsent queue */
+ if (pcb->unsent == NULL) {
+ pcb->unsent = seg;
+ } else {
+ struct tcp_seg *useg;
+ for (useg = pcb->unsent; useg->next != NULL; useg = useg->next);
+ useg->next = seg;
+ }
+#if TCP_OVERSIZE
+ /* The new unsent tail has no space */
+ pcb->unsent_oversize = 0;
+#endif /* TCP_OVERSIZE */
+
+ /* SYN and FIN bump the sequence number */
+ if ((flags & TCP_SYN) || (flags & TCP_FIN)) {
+ pcb->snd_lbb++;
+ /* optlen does not influence snd_buf */
+ pcb->snd_buf--;
+ }
+ if (flags & TCP_FIN) {
+ pcb->flags |= TF_FIN;
+ }
+
+ /* update number of segments on the queues */
+ pcb->snd_queuelen += pbuf_clen(seg->p);
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue_flags: %"S16_F" (after enqueued)\n", pcb->snd_queuelen));
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_enqueue_flags: invalid queue length",
+ pcb->unacked != NULL || pcb->unsent != NULL);
+ }
+
+ return ERR_OK;
+}
+
+
+#if LWIP_TCP_TIMESTAMPS
+/* Build a timestamp option (12 bytes long) at the specified options pointer)
+ *
+ * @param pcb tcp_pcb
+ * @param opts option pointer where to store the timestamp option
+ */
+static void
+tcp_build_timestamp_option(struct tcp_pcb *pcb, u32_t *opts)
+{
+ /* Pad with two NOP options to make everything nicely aligned */
+ opts[0] = PP_HTONL(0x0101080A);
+ opts[1] = htonl(sys_now());
+ opts[2] = htonl(pcb->ts_recent);
+}
+#endif
+
+/** Send an ACK without data.
+ *
+ * @param pcb Protocol control block for the TCP connection to send the ACK
+ */
+err_t
+tcp_send_empty_ack(struct tcp_pcb *pcb)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+ u8_t optlen = 0;
+
+#if LWIP_TCP_TIMESTAMPS
+ if (pcb->flags & TF_TIMESTAMP) {
+ optlen = LWIP_TCP_OPT_LENGTH(TF_SEG_OPTS_TS);
+ }
+#endif
+
+ p = tcp_output_alloc_header(pcb, optlen, 0, htonl(pcb->snd_nxt));
+ if (p == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: (ACK) could not allocate pbuf\n"));
+ return ERR_BUF;
+ }
+ tcphdr = (struct tcp_hdr *)p->payload;
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG,
+ ("tcp_output: sending ACK for %"U32_F"\n", pcb->rcv_nxt));
+ /* remove ACK flags from the PCB, as we send an empty ACK now */
+ pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW);
+
+ /* NB. MSS option is only sent on SYNs, so ignore it here */
+#if LWIP_TCP_TIMESTAMPS
+ pcb->ts_lastacksent = pcb->rcv_nxt;
+
+ if (pcb->flags & TF_TIMESTAMP) {
+ tcp_build_timestamp_option(pcb, (u32_t *)(tcphdr + 1));
+ }
+#endif
+
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, &(pcb->local_ip), &(pcb->remote_ip),
+ IP_PROTO_TCP, p->tot_len);
+#endif
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP, &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+ pbuf_free(p);
+
+ return ERR_OK;
+}
+
+/**
+ * Find out what we can send and send it
+ *
+ * @param pcb Protocol control block for the TCP connection to send data
+ * @return ERR_OK if data has been sent or nothing to send
+ * another err_t on error
+ */
+err_t
+tcp_output(struct tcp_pcb *pcb)
+{
+ struct tcp_seg *seg, *useg;
+ u32_t wnd, snd_nxt;
+#if TCP_CWND_DEBUG
+ s16_t i = 0;
+#endif /* TCP_CWND_DEBUG */
+
+ /* First, check if we are invoked by the TCP input processing
+ code. If so, we do not output anything. Instead, we rely on the
+ input processing code to call us when input processing is done
+ with. */
+ if (tcp_input_pcb == pcb) {
+ return ERR_OK;
+ }
+
+ wnd = LWIP_MIN(pcb->snd_wnd, pcb->cwnd);
+
+ seg = pcb->unsent;
+
+ /* If the TF_ACK_NOW flag is set and no data will be sent (either
+ * because the ->unsent queue is empty or because the window does
+ * not allow it), construct an empty ACK segment and send it.
+ *
+ * If data is to be sent, we will just piggyback the ACK (see below).
+ */
+ if (pcb->flags & TF_ACK_NOW &&
+ (seg == NULL ||
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > wnd)) {
+ return tcp_send_empty_ack(pcb);
+ }
+
+ /* useg should point to last segment on unacked queue */
+ useg = pcb->unacked;
+ if (useg != NULL) {
+ for (; useg->next != NULL; useg = useg->next);
+ }
+
+#if TCP_OUTPUT_DEBUG
+ if (seg == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: nothing to send (%p)\n",
+ (void*)pcb->unsent));
+ }
+#endif /* TCP_OUTPUT_DEBUG */
+#if TCP_CWND_DEBUG
+ if (seg == NULL) {
+ LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %"U16_F
+ ", cwnd %"U16_F", wnd %"U32_F
+ ", seg == NULL, ack %"U32_F"\n",
+ pcb->snd_wnd, pcb->cwnd, wnd, pcb->lastack));
+ } else {
+ LWIP_DEBUGF(TCP_CWND_DEBUG,
+ ("tcp_output: snd_wnd %"U16_F", cwnd %"U16_F", wnd %"U32_F
+ ", effwnd %"U32_F", seq %"U32_F", ack %"U32_F"\n",
+ pcb->snd_wnd, pcb->cwnd, wnd,
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len,
+ ntohl(seg->tcphdr->seqno), pcb->lastack));
+ }
+#endif /* TCP_CWND_DEBUG */
+ /* data available and window allows it to be sent? */
+ while (seg != NULL &&
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len <= wnd) {
+ LWIP_ASSERT("RST not expected here!",
+ (TCPH_FLAGS(seg->tcphdr) & TCP_RST) == 0);
+ /* Stop sending if the nagle algorithm would prevent it
+ * Don't stop:
+ * - if tcp_write had a memory error before (prevent delayed ACK timeout) or
+ * - if FIN was already enqueued for this PCB (SYN is always alone in a segment -
+ * either seg->next != NULL or pcb->unacked == NULL;
+ * RST is no sent using tcp_write/tcp_output.
+ */
+ if((tcp_do_output_nagle(pcb) == 0) &&
+ ((pcb->flags & (TF_NAGLEMEMERR | TF_FIN)) == 0)){
+ break;
+ }
+#if TCP_CWND_DEBUG
+ LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %"U16_F", cwnd %"U16_F", wnd %"U32_F", effwnd %"U32_F", seq %"U32_F", ack %"U32_F", i %"S16_F"\n",
+ pcb->snd_wnd, pcb->cwnd, wnd,
+ ntohl(seg->tcphdr->seqno) + seg->len -
+ pcb->lastack,
+ ntohl(seg->tcphdr->seqno), pcb->lastack, i));
+ ++i;
+#endif /* TCP_CWND_DEBUG */
+
+ pcb->unsent = seg->next;
+
+ if (pcb->state != SYN_SENT) {
+ TCPH_SET_FLAG(seg->tcphdr, TCP_ACK);
+ pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW);
+ }
+
+ tcp_output_segment(seg, pcb);
+ snd_nxt = ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg);
+ if (TCP_SEQ_LT(pcb->snd_nxt, snd_nxt)) {
+ pcb->snd_nxt = snd_nxt;
+ }
+ /* put segment on unacknowledged list if length > 0 */
+ if (TCP_TCPLEN(seg) > 0) {
+ seg->next = NULL;
+ /* unacked list is empty? */
+ if (pcb->unacked == NULL) {
+ pcb->unacked = seg;
+ useg = seg;
+ /* unacked list is not empty? */
+ } else {
+ /* In the case of fast retransmit, the packet should not go to the tail
+ * of the unacked queue, but rather somewhere before it. We need to check for
+ * this case. -STJ Jul 27, 2004 */
+ if (TCP_SEQ_LT(ntohl(seg->tcphdr->seqno), ntohl(useg->tcphdr->seqno))) {
+ /* add segment to before tail of unacked list, keeping the list sorted */
+ struct tcp_seg **cur_seg = &(pcb->unacked);
+ while (*cur_seg &&
+ TCP_SEQ_LT(ntohl((*cur_seg)->tcphdr->seqno), ntohl(seg->tcphdr->seqno))) {
+ cur_seg = &((*cur_seg)->next );
+ }
+ seg->next = (*cur_seg);
+ (*cur_seg) = seg;
+ } else {
+ /* add segment to tail of unacked list */
+ useg->next = seg;
+ useg = useg->next;
+ }
+ }
+ /* do not queue empty segments on the unacked list */
+ } else {
+ tcp_seg_free(seg);
+ }
+ seg = pcb->unsent;
+ }
+#if TCP_OVERSIZE
+ if (pcb->unsent == NULL) {
+ /* last unsent has been removed, reset unsent_oversize */
+ pcb->unsent_oversize = 0;
+ }
+#endif /* TCP_OVERSIZE */
+
+ if (seg != NULL && pcb->persist_backoff == 0 &&
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > pcb->snd_wnd) {
+ /* prepare for persist timer */
+ pcb->persist_cnt = 0;
+ pcb->persist_backoff = 1;
+ }
+
+ pcb->flags &= ~TF_NAGLEMEMERR;
+ return ERR_OK;
+}
+
+/**
+ * Called by tcp_output() to actually send a TCP segment over IP.
+ *
+ * @param seg the tcp_seg to send
+ * @param pcb the tcp_pcb for the TCP connection used to send the segment
+ */
+static void
+tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb)
+{
+ u16_t len;
+ struct netif *netif;
+ u32_t *opts;
+
+ /** @bug Exclude retransmitted segments from this count. */
+ snmp_inc_tcpoutsegs();
+
+ /* The TCP header has already been constructed, but the ackno and
+ wnd fields remain. */
+ seg->tcphdr->ackno = htonl(pcb->rcv_nxt);
+
+ /* advertise our receive window size in this TCP segment */
+ seg->tcphdr->wnd = htons(pcb->rcv_ann_wnd);
+
+ pcb->rcv_ann_right_edge = pcb->rcv_nxt + pcb->rcv_ann_wnd;
+
+ /* Add any requested options. NB MSS option is only set on SYN
+ packets, so ignore it here */
+ LWIP_ASSERT("seg->tcphdr not aligned", ((mem_ptr_t)seg->tcphdr % MEM_ALIGNMENT) == 0);
+ opts = (u32_t *)(void *)(seg->tcphdr + 1);
+ if (seg->flags & TF_SEG_OPTS_MSS) {
+ TCP_BUILD_MSS_OPTION(*opts);
+ opts += 1;
+ }
+#if LWIP_TCP_TIMESTAMPS
+ pcb->ts_lastacksent = pcb->rcv_nxt;
+
+ if (seg->flags & TF_SEG_OPTS_TS) {
+ tcp_build_timestamp_option(pcb, opts);
+ opts += 3;
+ }
+#endif
+
+ /* Set retransmission timer running if it is not currently enabled
+ This must be set before checking the route. */
+ if (pcb->rtime == -1) {
+ pcb->rtime = 0;
+ }
+
+ /* If we don't have a local IP address, we get one by
+ calling ip_route(). */
+ if (ip_addr_isany(&(pcb->local_ip))) {
+ netif = ip_route(&(pcb->remote_ip));
+ if (netif == NULL) {
+ return;
+ }
+ ip_addr_copy(pcb->local_ip, netif->ip_addr);
+ }
+
+ if (pcb->rttest == 0) {
+ pcb->rttest = tcp_ticks;
+ pcb->rtseq = ntohl(seg->tcphdr->seqno);
+
+ LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_output_segment: rtseq %"U32_F"\n", pcb->rtseq));
+ }
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output_segment: %"U32_F":%"U32_F"\n",
+ htonl(seg->tcphdr->seqno), htonl(seg->tcphdr->seqno) +
+ seg->len));
+
+ len = (u16_t)((u8_t *)seg->tcphdr - (u8_t *)seg->p->payload);
+
+ seg->p->len -= len;
+ seg->p->tot_len -= len;
+
+ seg->p->payload = seg->tcphdr;
+
+ seg->tcphdr->chksum = 0;
+#if CHECKSUM_GEN_TCP
+#if TCP_CHECKSUM_ON_COPY
+ {
+ u32_t acc;
+#if TCP_CHECKSUM_ON_COPY_SANITY_CHECK
+ u16_t chksum_slow = inet_chksum_pseudo(seg->p, &(pcb->local_ip),
+ &(pcb->remote_ip),
+ IP_PROTO_TCP, seg->p->tot_len);
+#endif /* TCP_CHECKSUM_ON_COPY_SANITY_CHECK */
+ if ((seg->flags & TF_SEG_DATA_CHECKSUMMED) == 0) {
+ LWIP_ASSERT("data included but not checksummed",
+ seg->p->tot_len == (TCPH_HDRLEN(seg->tcphdr) * 4));
+ }
+
+ /* rebuild TCP header checksum (TCP header changes for retransmissions!) */
+ acc = inet_chksum_pseudo_partial(seg->p, &(pcb->local_ip),
+ &(pcb->remote_ip),
+ IP_PROTO_TCP, seg->p->tot_len, TCPH_HDRLEN(seg->tcphdr) * 4);
+ /* add payload checksum */
+ if (seg->chksum_swapped) {
+ seg->chksum = SWAP_BYTES_IN_WORD(seg->chksum);
+ seg->chksum_swapped = 0;
+ }
+ acc += (u16_t)~(seg->chksum);
+ seg->tcphdr->chksum = FOLD_U32T(acc);
+#if TCP_CHECKSUM_ON_COPY_SANITY_CHECK
+ if (chksum_slow != seg->tcphdr->chksum) {
+ LWIP_DEBUGF(TCP_DEBUG | LWIP_DBG_LEVEL_WARNING,
+ ("tcp_output_segment: calculated checksum is %"X16_F" instead of %"X16_F"\n",
+ seg->tcphdr->chksum, chksum_slow));
+ seg->tcphdr->chksum = chksum_slow;
+ }
+#endif /* TCP_CHECKSUM_ON_COPY_SANITY_CHECK */
+ }
+#else /* TCP_CHECKSUM_ON_COPY */
+ seg->tcphdr->chksum = inet_chksum_pseudo(seg->p, &(pcb->local_ip),
+ &(pcb->remote_ip),
+ IP_PROTO_TCP, seg->p->tot_len);
+#endif /* TCP_CHECKSUM_ON_COPY */
+#endif /* CHECKSUM_GEN_TCP */
+ TCP_STATS_INC(tcp.xmit);
+
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP, &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+}
+
+/**
+ * Send a TCP RESET packet (empty segment with RST flag set) either to
+ * abort a connection or to show that there is no matching local connection
+ * for a received segment.
+ *
+ * Called by tcp_abort() (to abort a local connection), tcp_input() (if no
+ * matching local pcb was found), tcp_listen_input() (if incoming segment
+ * has ACK flag set) and tcp_process() (received segment in the wrong state)
+ *
+ * Since a RST segment is in most cases not sent for an active connection,
+ * tcp_rst() has a number of arguments that are taken from a tcp_pcb for
+ * most other segment output functions.
+ *
+ * @param seqno the sequence number to use for the outgoing segment
+ * @param ackno the acknowledge number to use for the outgoing segment
+ * @param local_ip the local IP address to send the segment from
+ * @param remote_ip the remote IP address to send the segment to
+ * @param local_port the local TCP port to send the segment from
+ * @param remote_port the remote TCP port to send the segment to
+ */
+void
+tcp_rst(u32_t seqno, u32_t ackno,
+ ip_addr_t *local_ip, ip_addr_t *remote_ip,
+ u16_t local_port, u16_t remote_port)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+ p = pbuf_alloc(PBUF_IP, TCP_HLEN, PBUF_RAM);
+ if (p == NULL) {
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_rst: could not allocate memory for pbuf\n"));
+ return;
+ }
+ LWIP_ASSERT("check that first pbuf can hold struct tcp_hdr",
+ (p->len >= sizeof(struct tcp_hdr)));
+
+ tcphdr = (struct tcp_hdr *)p->payload;
+ tcphdr->src = htons(local_port);
+ tcphdr->dest = htons(remote_port);
+ tcphdr->seqno = htonl(seqno);
+ tcphdr->ackno = htonl(ackno);
+ TCPH_HDRLEN_FLAGS_SET(tcphdr, TCP_HLEN/4, TCP_RST | TCP_ACK);
+ tcphdr->wnd = PP_HTONS(TCP_WND);
+ tcphdr->chksum = 0;
+ tcphdr->urgp = 0;
+
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, local_ip, remote_ip,
+ IP_PROTO_TCP, p->tot_len);
+#endif
+ TCP_STATS_INC(tcp.xmit);
+ snmp_inc_tcpoutrsts();
+ /* Send output with hardcoded TTL since we have no access to the pcb */
+ ip_output(p, local_ip, remote_ip, TCP_TTL, 0, IP_PROTO_TCP);
+ pbuf_free(p);
+ LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_rst: seqno %"U32_F" ackno %"U32_F".\n", seqno, ackno));
+}
+
+/**
+ * Requeue all unacked segments for retransmission
+ *
+ * Called by tcp_slowtmr() for slow retransmission.
+ *
+ * @param pcb the tcp_pcb for which to re-enqueue all unacked segments
+ */
+void
+tcp_rexmit_rto(struct tcp_pcb *pcb)
+{
+ struct tcp_seg *seg;
+
+ if (pcb->unacked == NULL) {
+ return;
+ }
+
+ /* Move all unacked segments to the head of the unsent queue */
+ for (seg = pcb->unacked; seg->next != NULL; seg = seg->next);
+ /* concatenate unsent queue after unacked queue */
+ seg->next = pcb->unsent;
+ /* unsent queue is the concatenated queue (of unacked, unsent) */
+ pcb->unsent = pcb->unacked;
+ /* unacked queue is now empty */
+ pcb->unacked = NULL;
+
+ /* increment number of retransmissions */
+ ++pcb->nrtx;
+
+ /* Don't take any RTT measurements after retransmitting. */
+ pcb->rttest = 0;
+
+ /* Do the actual retransmission */
+ tcp_output(pcb);
+}
+
+/**
+ * Requeue the first unacked segment for retransmission
+ *
+ * Called by tcp_receive() for fast retramsmit.
+ *
+ * @param pcb the tcp_pcb for which to retransmit the first unacked segment
+ */
+void
+tcp_rexmit(struct tcp_pcb *pcb)
+{
+ struct tcp_seg *seg;
+ struct tcp_seg **cur_seg;
+
+ if (pcb->unacked == NULL) {
+ return;
+ }
+
+ /* Move the first unacked segment to the unsent queue */
+ /* Keep the unsent queue sorted. */
+ seg = pcb->unacked;
+ pcb->unacked = seg->next;
+
+ cur_seg = &(pcb->unsent);
+ while (*cur_seg &&
+ TCP_SEQ_LT(ntohl((*cur_seg)->tcphdr->seqno), ntohl(seg->tcphdr->seqno))) {
+ cur_seg = &((*cur_seg)->next );
+ }
+ seg->next = *cur_seg;
+ *cur_seg = seg;
+
+ ++pcb->nrtx;
+
+ /* Don't take any rtt measurements after retransmitting. */
+ pcb->rttest = 0;
+
+ /* Do the actual retransmission. */
+ snmp_inc_tcpretranssegs();
+ /* No need to call tcp_output: we are always called from tcp_input()
+ and thus tcp_output directly returns. */
+}
+
+
+/**
+ * Handle retransmission after three dupacks received
+ *
+ * @param pcb the tcp_pcb for which to retransmit the first unacked segment
+ */
+void
+tcp_rexmit_fast(struct tcp_pcb *pcb)
+{
+ if (pcb->unacked != NULL && !(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 half of the minimum of the current
+ * cwnd and the advertised window */
+ if (pcb->cwnd > pcb->snd_wnd) {
+ pcb->ssthresh = pcb->snd_wnd / 2;
+ } else {
+ pcb->ssthresh = pcb->cwnd / 2;
+ }
+
+ /* The minimum value for ssthresh should be 2 MSS */
+ if (pcb->ssthresh < 2*pcb->mss) {
+ LWIP_DEBUGF(TCP_FR_DEBUG,
+ ("tcp_receive: The minimum value for ssthresh %"U16_F
+ " should be min 2 mss %"U16_F"...\n",
+ pcb->ssthresh, 2*pcb->mss));
+ pcb->ssthresh = 2*pcb->mss;
+ }
+
+ pcb->cwnd = pcb->ssthresh + 3 * pcb->mss;
+ pcb->flags |= TF_INFR;
+ }
+}
+
+
+/**
+ * Send keepalive packets to keep a connection active although
+ * no data is sent over it.
+ *
+ * Called by tcp_slowtmr()
+ *
+ * @param pcb the tcp_pcb for which to send a keepalive packet
+ */
+void
+tcp_keepalive(struct tcp_pcb *pcb)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: sending KEEPALIVE probe to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
+ ip4_addr1_16(&pcb->remote_ip), ip4_addr2_16(&pcb->remote_ip),
+ ip4_addr3_16(&pcb->remote_ip), ip4_addr4_16(&pcb->remote_ip)));
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: tcp_ticks %"U32_F" pcb->tmr %"U32_F" pcb->keep_cnt_sent %"U16_F"\n",
+ tcp_ticks, pcb->tmr, pcb->keep_cnt_sent));
+
+ p = tcp_output_alloc_header(pcb, 0, 0, htonl(pcb->snd_nxt - 1));
+ if(p == NULL) {
+ LWIP_DEBUGF(TCP_DEBUG,
+ ("tcp_keepalive: could not allocate memory for pbuf\n"));
+ return;
+ }
+ tcphdr = (struct tcp_hdr *)p->payload;
+
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, &pcb->local_ip, &pcb->remote_ip,
+ IP_PROTO_TCP, p->tot_len);
+#endif
+ TCP_STATS_INC(tcp.xmit);
+
+ /* Send output to IP */
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP,
+ &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+
+ pbuf_free(p);
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: seqno %"U32_F" ackno %"U32_F".\n",
+ pcb->snd_nxt - 1, pcb->rcv_nxt));
+}
+
+
+/**
+ * Send persist timer zero-window probes to keep a connection active
+ * when a window update is lost.
+ *
+ * Called by tcp_slowtmr()
+ *
+ * @param pcb the tcp_pcb for which to send a zero-window probe packet
+ */
+void
+tcp_zero_window_probe(struct tcp_pcb *pcb)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+ struct tcp_seg *seg;
+ u16_t len;
+ u8_t is_fin;
+
+ LWIP_DEBUGF(TCP_DEBUG,
+ ("tcp_zero_window_probe: sending ZERO WINDOW probe to %"
+ U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
+ ip4_addr1_16(&pcb->remote_ip), ip4_addr2_16(&pcb->remote_ip),
+ ip4_addr3_16(&pcb->remote_ip), ip4_addr4_16(&pcb->remote_ip)));
+
+ LWIP_DEBUGF(TCP_DEBUG,
+ ("tcp_zero_window_probe: tcp_ticks %"U32_F
+ " pcb->tmr %"U32_F" pcb->keep_cnt_sent %"U16_F"\n",
+ tcp_ticks, pcb->tmr, pcb->keep_cnt_sent));
+
+ seg = pcb->unacked;
+
+ if(seg == NULL) {
+ seg = pcb->unsent;
+ }
+ if(seg == NULL) {
+ return;
+ }
+
+ is_fin = ((TCPH_FLAGS(seg->tcphdr) & TCP_FIN) != 0) && (seg->len == 0);
+ /* we want to send one seqno: either FIN or data (no options) */
+ len = is_fin ? 0 : 1;
+
+ p = tcp_output_alloc_header(pcb, 0, len, seg->tcphdr->seqno);
+ if(p == NULL) {
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: no memory for pbuf\n"));
+ return;
+ }
+ tcphdr = (struct tcp_hdr *)p->payload;
+
+ if (is_fin) {
+ /* FIN segment, no data */
+ TCPH_FLAGS_SET(tcphdr, TCP_ACK | TCP_FIN);
+ } else {
+ /* Data segment, copy in one byte from the head of the unacked queue */
+ struct tcp_hdr *thdr = (struct tcp_hdr *)seg->p->payload;
+ char *d = ((char *)p->payload + TCP_HLEN);
+ pbuf_copy_partial(seg->p, d, 1, TCPH_HDRLEN(thdr) * 4);
+ }
+
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, &pcb->local_ip, &pcb->remote_ip,
+ IP_PROTO_TCP, p->tot_len);
+#endif
+ TCP_STATS_INC(tcp.xmit);
+
+ /* Send output to IP */
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP,
+ &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+
+ pbuf_free(p);
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: seqno %"U32_F
+ " ackno %"U32_F".\n",
+ pcb->snd_nxt - 1, pcb->rcv_nxt));
+}
+#endif /* LWIP_TCP */