diff options
Diffstat (limited to 'lwip/src/core/tcp_out.c')
| -rw-r--r-- | lwip/src/core/tcp_out.c | 2190 |
1 files changed, 2190 insertions, 0 deletions
diff --git a/lwip/src/core/tcp_out.c b/lwip/src/core/tcp_out.c new file mode 100644 index 0000000..724df10 --- /dev/null +++ b/lwip/src/core/tcp_out.c @@ -0,0 +1,2190 @@ +/** + * @file + * Transmission Control Protocol, outgoing traffic + * + * The output functions of TCP. + * + * There are two distinct ways for TCP segments to get sent: + * - queued data: these are segments transferring data or segments containing + * SYN or FIN (which both count as one sequence number). They are created as + * struct @ref pbuf together with a struct tcp_seg and enqueue to the + * unsent list of the pcb. They are sent by tcp_output: + * - @ref tcp_write : creates data segments + * - @ref tcp_split_unsent_seg : splits a data segment + * - @ref tcp_enqueue_flags : creates SYN-only or FIN-only segments + * - @ref tcp_output / tcp_output_segment : finalize the tcp header + * (e.g. sequence numbers, options, checksum) and output to IP + * - the various tcp_rexmit functions shuffle around segments between the + * unsent an unacked lists to retransmit them + * - tcp_create_segment and tcp_pbuf_prealloc allocate pbuf and + * segment for these functions + * - direct send: these segments don't contain data but control the connection + * behaviour. They are created as pbuf only and sent directly without + * enqueueing them: + * - @ref tcp_send_empty_ack sends an ACK-only segment + * - @ref tcp_rst sends a RST segment + * - @ref tcp_keepalive sends a keepalive segment + * - @ref tcp_zero_window_probe sends a window probe segment + * - tcp_output_alloc_header allocates a header-only pbuf for these functions + */ + +/* + * 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/priv/tcp_priv.h" +#include "lwip/def.h" +#include "lwip/mem.h" +#include "lwip/memp.h" +#include "lwip/ip_addr.h" +#include "lwip/netif.h" +#include "lwip/inet_chksum.h" +#include "lwip/stats.h" +#include "lwip/ip6.h" +#include "lwip/ip6_addr.h" +#if LWIP_TCP_TIMESTAMPS +#include "lwip/sys.h" +#endif + +#include <string.h> + +#ifdef LWIP_HOOK_FILENAME +#include LWIP_HOOK_FILENAME +#endif + +/* Allow to add custom TCP header options by defining this hook */ +#ifdef LWIP_HOOK_TCP_OUT_TCPOPT_LENGTH +#define LWIP_TCP_OPT_LENGTH_SEGMENT(flags, pcb) LWIP_HOOK_TCP_OUT_TCPOPT_LENGTH(pcb, LWIP_TCP_OPT_LENGTH(flags)) +#else +#define LWIP_TCP_OPT_LENGTH_SEGMENT(flags, pcb) LWIP_TCP_OPT_LENGTH(flags) +#endif + +/* 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 +/* Allow to override the failure of sanity check from warning to e.g. hard failure */ +#if TCP_CHECKSUM_ON_COPY_SANITY_CHECK +#ifndef TCP_CHECKSUM_ON_COPY_SANITY_CHECK_FAIL +#define TCP_CHECKSUM_ON_COPY_SANITY_CHECK_FAIL(msg) LWIP_DEBUGF(TCP_DEBUG | LWIP_DBG_LEVEL_WARNING, msg) +#endif +#endif + +#if TCP_OVERSIZE +/** The size of segment pbufs created when TCP_OVERSIZE is enabled */ +#ifndef TCP_OVERSIZE_CALC_LENGTH +#define TCP_OVERSIZE_CALC_LENGTH(length) ((length) + TCP_OVERSIZE) +#endif +#endif + +/* Forward declarations.*/ +static err_t tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb, struct netif *netif); + +/* tcp_route: common code that returns a fixed bound netif or calls ip_route */ +static struct netif * +tcp_route(const struct tcp_pcb *pcb, const ip_addr_t *src, const ip_addr_t *dst) +{ + LWIP_UNUSED_ARG(src); /* in case IPv4-only and source-based routing is disabled */ + + if ((pcb != NULL) && (pcb->netif_idx != NETIF_NO_INDEX)) { + return netif_get_by_index(pcb->netif_idx); + } else { + return ip_route(src, dst); + } +} + +/** + * Create a TCP segment with prefilled header. + * + * Called by @ref tcp_write, @ref tcp_enqueue_flags and @ref tcp_split_unsent_seg + * + * @param pcb Protocol control block for the TCP connection. + * @param p pbuf that is used to hold the TCP header. + * @param hdrflags 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(const struct tcp_pcb *pcb, struct pbuf *p, u8_t hdrflags, u32_t seqno, u8_t optflags) +{ + struct tcp_seg *seg; + u8_t optlen; + + LWIP_ASSERT("tcp_create_segment: invalid pcb", pcb != NULL); + LWIP_ASSERT("tcp_create_segment: invalid pbuf", p != NULL); + + optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(optflags, pcb); + + if ((seg = (struct tcp_seg *)memp_malloc(MEMP_TCP_SEG)) == NULL) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("tcp_create_segment: no memory.\n")); + pbuf_free(p); + return NULL; + } + seg->flags = optflags; + seg->next = NULL; + seg->p = p; + LWIP_ASSERT("p->tot_len >= optlen", p->tot_len >= optlen); + 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_add_header(p, TCP_HLEN)) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("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 = lwip_htons(pcb->local_port); + seg->tcphdr->dest = lwip_htons(pcb->remote_port); + seg->tcphdr->seqno = lwip_htonl(seqno); + /* ackno is set in tcp_output */ + TCPH_HDRLEN_FLAGS_SET(seg->tcphdr, (5 + optlen / 4), hdrflags); + /* 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. + * + * Called by @ref tcp_write + * + * @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 will 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. + */ +#if TCP_OVERSIZE +static struct pbuf * +tcp_pbuf_prealloc(pbuf_layer layer, u16_t length, u16_t max_length, + u16_t *oversize, const struct tcp_pcb *pcb, u8_t apiflags, + u8_t first_seg) +{ + struct pbuf *p; + u16_t alloc = length; + + LWIP_ASSERT("tcp_pbuf_prealloc: invalid oversize", oversize != NULL); + LWIP_ASSERT("tcp_pbuf_prealloc: invalid pcb", pcb != NULL); + +#if LWIP_NETIF_TX_SINGLE_PBUF + LWIP_UNUSED_ARG(max_length); + LWIP_UNUSED_ARG(pcb); + LWIP_UNUSED_ARG(apiflags); + LWIP_UNUSED_ARG(first_seg); + alloc = max_length; +#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(TCP_OVERSIZE_CALC_LENGTH(length))); + } + } +#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. + * + * Called by tcp_write and tcp_split_unsent_seg. + */ +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) +{ + LWIP_ASSERT("tcp_write_checks: invalid pcb", pcb != NULL); + + /* 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 | LWIP_DBG_LEVEL_SEVERE, ("tcp_write: too much data (len=%"U16_F" > snd_buf=%"TCPWNDSIZE_F")\n", + len, pcb->snd_buf)); + tcp_set_flags(pcb, TF_NAGLEMEMERR); + return ERR_MEM; + } + + LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_write: queuelen: %"TCPWNDSIZE_F"\n", (tcpwnd_size_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 >= LWIP_MIN(TCP_SND_QUEUELEN, (TCP_SNDQUEUELEN_OVERFLOW + 1))) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("tcp_write: too long queue %"U16_F" (max %"U16_F")\n", + pcb->snd_queuelen, (u16_t)TCP_SND_QUEUELEN)); + TCP_STATS_INC(tcp.memerr); + tcp_set_flags(pcb, 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; +} + +/** + * @ingroup tcp_raw + * 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(). + * + * This function enqueues the data pointed to by the argument dataptr. The length of + * the data is passed as the len parameter. The apiflags can be one or more of: + * - TCP_WRITE_FLAG_COPY: indicates whether the new memory should be allocated + * for the data to be copied into. If this flag is not given, no new memory + * should be allocated and the data should only be referenced by pointer. This + * also means that the memory behind dataptr must not change until the data is + * ACKed by the remote host + * - TCP_WRITE_FLAG_MORE: indicates that more data follows. If this is omitted, + * the PSH flag is set in the last segment created by this call to tcp_write. + * If this flag is given, the PSH flag is not set. + * + * The tcp_write() function will fail and return ERR_MEM if the length + * of the data exceeds the current send buffer size or if the length of + * the queue of outgoing segment is larger than the upper limit defined + * in lwipopts.h. The number of bytes available in the output queue can + * be retrieved with the tcp_sndbuf() function. + * + * The proper way to use this function is to call the function with at + * most tcp_sndbuf() bytes of data. If the function returns ERR_MEM, + * the application should wait until some of the currently enqueued + * data has been successfully received by the other host and try again. + * + * @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 not 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; + u8_t optflags = 0; +#if TCP_OVERSIZE + u16_t oversize = 0; + u16_t oversize_used = 0; +#if TCP_OVERSIZE_DBGCHECK + u16_t oversize_add = 0; +#endif /* TCP_OVERSIZE_DBGCHECK*/ +#endif /* TCP_OVERSIZE */ + u16_t extendlen = 0; +#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; + u16_t mss_local; + + LWIP_ERROR("tcp_write: invalid pcb", pcb != NULL, return ERR_ARG); + + /* don't allocate segments bigger than half the maximum window we ever received */ + mss_local = LWIP_MIN(pcb->mss, TCPWND_MIN16(pcb->snd_wnd_max / 2)); + mss_local = mss_local ? mss_local : pcb->mss; + + LWIP_ASSERT_CORE_LOCKED(); + +#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)) { + /* Make sure the timestamp option is only included in data segments if we + agreed about it with the remote host. */ + optflags = TF_SEG_OPTS_TS; + optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(TF_SEG_OPTS_TS, pcb); + /* ensure that segments can hold at least one data byte... */ + mss_local = LWIP_MAX(mss_local, LWIP_TCP_OPT_LEN_TS + 1); + } else +#endif /* LWIP_TCP_TIMESTAMPS */ + { + optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(0, pcb); + } + + + /* + * 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_SEGMENT(last_unsent->flags, pcb); + LWIP_ASSERT("mss_local is too small", mss_local >= last_unsent->len + unsent_optlen); + space = mss_local - (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->oversize_left */ + 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 <= space); + seg = last_unsent; + oversize_used = LWIP_MIN(space, LWIP_MIN(oversize, len)); + pos += oversize_used; + oversize -= oversize_used; + space -= oversize_used; + } + /* now we are either finished or oversize is zero */ + LWIP_ASSERT("inconsistent oversize vs. len", (oversize == 0) || (pos == len)); +#endif /* TCP_OVERSIZE */ + +#if !LWIP_NETIF_TX_SINGLE_PBUF + /* + * Phase 2: Chain a new pbuf to the end of pcb->unsent. + * + * As an exception when NOT copying the data, if the given data buffer + * directly follows the last unsent data buffer in memory, extend the last + * ROM pbuf reference to the buffer, thus saving a ROM pbuf allocation. + * + * 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. + * + * This phase is skipped for LWIP_NETIF_TX_SINGLE_PBUF as we could only execute + * it after rexmit puts a segment from unacked to unsent and at this point, + * oversize info is lost. + */ + if ((pos < len) && (space > 0) && (last_unsent->len > 0)) { + u16_t seglen = LWIP_MIN(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 | LWIP_DBG_LEVEL_SERIOUS, + ("tcp_write : could not allocate memory for pbuf copy size %"U16_F"\n", + seglen)); + goto memerr; + } +#if TCP_OVERSIZE_DBGCHECK + oversize_add = oversize; +#endif /* TCP_OVERSIZE_DBGCHECK */ + TCP_DATA_COPY2(concat_p->payload, (const u8_t *)arg + pos, seglen, &concat_chksum, &concat_chksum_swapped); +#if TCP_CHECKSUM_ON_COPY + concat_chksummed += seglen; +#endif /* TCP_CHECKSUM_ON_COPY */ + queuelen += pbuf_clen(concat_p); + } else { + /* Data is not copied */ + /* If the last unsent pbuf is of type PBUF_ROM, try to extend it. */ + struct pbuf *p; + for (p = last_unsent->p; p->next != NULL; p = p->next); + if (((p->type_internal & (PBUF_TYPE_FLAG_STRUCT_DATA_CONTIGUOUS | PBUF_TYPE_FLAG_DATA_VOLATILE)) == 0) && + (const u8_t *)p->payload + p->len == (const u8_t *)arg) { + LWIP_ASSERT("tcp_write: ROM pbufs cannot be oversized", pos == 0); + extendlen = seglen; + } else { + if ((concat_p = pbuf_alloc(PBUF_RAW, seglen, PBUF_ROM)) == NULL) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, + ("tcp_write: could not allocate memory for zero-copy pbuf\n")); + goto memerr; + } + /* reference the non-volatile payload data */ + ((struct pbuf_rom *)concat_p)->payload = (const u8_t *)arg + pos; + queuelen += pbuf_clen(concat_p); + } +#if TCP_CHECKSUM_ON_COPY + /* calculate the checksum of nocopy-data */ + tcp_seg_add_chksum(~inet_chksum((const u8_t *)arg + pos, seglen), seglen, + &concat_chksum, &concat_chksum_swapped); + concat_chksummed += seglen; +#endif /* TCP_CHECKSUM_ON_COPY */ + } + + pos += seglen; + } +#endif /* !LWIP_NETIF_TX_SINGLE_PBUF */ + } 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 = mss_local - optlen; + u16_t seglen = LWIP_MIN(left, max_len); +#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, mss_local, &oversize, pcb, apiflags, queue == NULL)) == NULL) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("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, (const 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 | LWIP_DBG_LEVEL_SERIOUS, ("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((const u8_t *)arg + pos, seglen); + if (seglen & 1) { + chksum_swapped = 1; + chksum = SWAP_BYTES_IN_WORD(chksum); + } +#endif /* TCP_CHECKSUM_ON_COPY */ + /* reference the non-volatile payload data */ + ((struct pbuf_rom *)p2)->payload = (const 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 | LWIP_DBG_LEVEL_SERIOUS, ("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 > LWIP_MIN(TCP_SND_QUEUELEN, TCP_SNDQUEUELEN_OVERFLOW)) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("tcp_write: queue too long %"U16_F" (%d)\n", + queuelen, (int)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", + lwip_ntohl(seg->tcphdr->seqno), + lwip_ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg))); + + pos += seglen; + } + + /* + * All three segmentation phases were successful. We can commit the + * transaction. + */ +#if TCP_OVERSIZE_DBGCHECK + if ((last_unsent != NULL) && (oversize_add != 0)) { + last_unsent->oversize_left += oversize_add; + } +#endif /* TCP_OVERSIZE_DBGCHECK */ + + /* + * 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 + LWIP_ASSERT("last_unsent->oversize_left >= oversize_used", + last_unsent->oversize_left >= oversize_used); + 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, unless we + * determined that the last ROM pbuf can be extended to include the new data. + */ + 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; + } else if (extendlen > 0) { + struct pbuf *p; + LWIP_ASSERT("tcp_write: extension of reference requires reference", + last_unsent != NULL && last_unsent->p != NULL); + for (p = last_unsent->p; p->next != NULL; p = p->next) { + p->tot_len += extendlen; + } + p->tot_len += extendlen; + p->len += extendlen; + last_unsent->len += extendlen; + } + +#if TCP_CHECKSUM_ON_COPY + if (concat_chksummed) { + LWIP_ASSERT("tcp_write: concat checksum needs concatenated data", + concat_p != NULL || extendlen > 0); + /*if concat checksumm swapped - swap it back */ + if (concat_chksum_swapped) { + concat_chksum = SWAP_BYTES_IN_WORD(concat_chksum); + } + 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: + tcp_set_flags(pcb, 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; +} + +/** + * Split segment on the head of the unsent queue. If return is not + * ERR_OK, existing head remains intact + * + * The split is accomplished by creating a new TCP segment and pbuf + * which holds the remainder payload after the split. The original + * pbuf is trimmed to new length. This allows splitting of read-only + * pbufs + * + * @param pcb the tcp_pcb for which to split the unsent head + * @param split the amount of payload to remain in the head + */ +err_t +tcp_split_unsent_seg(struct tcp_pcb *pcb, u16_t split) +{ + struct tcp_seg *seg = NULL, *useg = NULL; + struct pbuf *p = NULL; + u8_t optlen; + u8_t optflags; + u8_t split_flags; + u8_t remainder_flags; + u16_t remainder; + u16_t offset; +#if TCP_CHECKSUM_ON_COPY + u16_t chksum = 0; + u8_t chksum_swapped = 0; + struct pbuf *q; +#endif /* TCP_CHECKSUM_ON_COPY */ + + LWIP_ASSERT("tcp_split_unsent_seg: invalid pcb", pcb != NULL); + + useg = pcb->unsent; + if (useg == NULL) { + return ERR_MEM; + } + + if (split == 0) { + LWIP_ASSERT("Can't split segment into length 0", 0); + return ERR_VAL; + } + + if (useg->len <= split) { + return ERR_OK; + } + + LWIP_ASSERT("split <= mss", split <= pcb->mss); + LWIP_ASSERT("useg->len > 0", useg->len > 0); + + /* We should check that we don't exceed TCP_SND_QUEUELEN but we need + * to split this packet so we may actually exceed the max value by + * one! + */ + LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue: split_unsent_seg: %u\n", (unsigned int)pcb->snd_queuelen)); + + optflags = useg->flags; +#if TCP_CHECKSUM_ON_COPY + /* Remove since checksum is not stored until after tcp_create_segment() */ + optflags &= ~TF_SEG_DATA_CHECKSUMMED; +#endif /* TCP_CHECKSUM_ON_COPY */ + optlen = LWIP_TCP_OPT_LENGTH(optflags); + remainder = useg->len - split; + + /* Create new pbuf for the remainder of the split */ + p = pbuf_alloc(PBUF_TRANSPORT, remainder + optlen, PBUF_RAM); + if (p == NULL) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, + ("tcp_split_unsent_seg: could not allocate memory for pbuf remainder %u\n", remainder)); + goto memerr; + } + + /* Offset into the original pbuf is past TCP/IP headers, options, and split amount */ + offset = useg->p->tot_len - useg->len + split; + /* Copy remainder into new pbuf, headers and options will not be filled out */ + if (pbuf_copy_partial(useg->p, (u8_t *)p->payload + optlen, remainder, offset ) != remainder) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, + ("tcp_split_unsent_seg: could not copy pbuf remainder %u\n", remainder)); + goto memerr; + } +#if TCP_CHECKSUM_ON_COPY + /* calculate the checksum on remainder data */ + tcp_seg_add_chksum(~inet_chksum((const u8_t *)p->payload + optlen, remainder), remainder, + &chksum, &chksum_swapped); +#endif /* TCP_CHECKSUM_ON_COPY */ + + /* Options are created when calling tcp_output() */ + + /* Migrate flags from original segment */ + split_flags = TCPH_FLAGS(useg->tcphdr); + remainder_flags = 0; /* ACK added in tcp_output() */ + + if (split_flags & TCP_PSH) { + split_flags &= ~TCP_PSH; + remainder_flags |= TCP_PSH; + } + if (split_flags & TCP_FIN) { + split_flags &= ~TCP_FIN; + remainder_flags |= TCP_FIN; + } + /* SYN should be left on split, RST should not be present with data */ + + seg = tcp_create_segment(pcb, p, remainder_flags, lwip_ntohl(useg->tcphdr->seqno) + split, optflags); + if (seg == NULL) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_LEVEL_SERIOUS, + ("tcp_split_unsent_seg: could not create new TCP segment\n")); + goto memerr; + } + +#if TCP_CHECKSUM_ON_COPY + seg->chksum = chksum; + seg->chksum_swapped = chksum_swapped; + seg->flags |= TF_SEG_DATA_CHECKSUMMED; +#endif /* TCP_CHECKSUM_ON_COPY */ + + /* Remove this segment from the queue since trimming it may free pbufs */ + pcb->snd_queuelen -= pbuf_clen(useg->p); + + /* Trim the original pbuf into our split size. At this point our remainder segment must be setup + successfully because we are modifying the original segment */ + pbuf_realloc(useg->p, useg->p->tot_len - remainder); + useg->len -= remainder; + TCPH_SET_FLAG(useg->tcphdr, split_flags); +#if TCP_OVERSIZE_DBGCHECK + /* By trimming, realloc may have actually shrunk the pbuf, so clear oversize_left */ + useg->oversize_left = 0; +#endif /* TCP_OVERSIZE_DBGCHECK */ + + /* Add back to the queue with new trimmed pbuf */ + pcb->snd_queuelen += pbuf_clen(useg->p); + +#if TCP_CHECKSUM_ON_COPY + /* The checksum on the split segment is now incorrect. We need to re-run it over the split */ + useg->chksum = 0; + useg->chksum_swapped = 0; + q = useg->p; + offset = q->tot_len - useg->len; /* Offset due to exposed headers */ + + /* Advance to the pbuf where the offset ends */ + while (q != NULL && offset > q->len) { + offset -= q->len; + q = q->next; + } + LWIP_ASSERT("Found start of payload pbuf", q != NULL); + /* Checksum the first payload pbuf accounting for offset, then other pbufs are all payload */ + for (; q != NULL; offset = 0, q = q->next) { + tcp_seg_add_chksum(~inet_chksum((const u8_t *)q->payload + offset, q->len - offset), q->len - offset, + &useg->chksum, &useg->chksum_swapped); + } +#endif /* TCP_CHECKSUM_ON_COPY */ + + /* Update number of segments on the queues. Note that length now may + * exceed TCP_SND_QUEUELEN! We don't have to touch pcb->snd_buf + * because the total amount of data is constant when packet is split */ + pcb->snd_queuelen += pbuf_clen(seg->p); + + /* Finally insert remainder into queue after split (which stays head) */ + seg->next = useg->next; + useg->next = seg; + +#if TCP_OVERSIZE + /* If remainder is last segment on the unsent, ensure we clear the oversize amount + * because the remainder is always sized to the exact remaining amount */ + if (seg->next == NULL) { + pcb->unsent_oversize = 0; + } +#endif /* TCP_OVERSIZE */ + + return ERR_OK; +memerr: + TCP_STATS_INC(tcp.memerr); + + LWIP_ASSERT("seg == NULL", seg == NULL); + if (p != NULL) { + pbuf_free(p); + } + + return ERR_MEM; +} + +/** + * Called by tcp_close() to send a segment including FIN flag but not data. + * This FIN may be added to an existing segment or a new, otherwise empty + * segment is enqueued. + * + * @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) +{ + LWIP_ASSERT("tcp_send_fin: invalid pcb", pcb != NULL); + + /* 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); + tcp_set_flags(pcb, TF_FIN); + return ERR_OK; + } + } + /* no data, no length, flags, copy=1, no optdata */ + return tcp_enqueue_flags(pcb, TCP_FIN); +} + +/** + * Enqueue SYN or FIN for transmission. + * + * Called by @ref tcp_connect, tcp_listen_input, and @ref tcp_close + * (via @ref tcp_send_fin) + * + * @param pcb Protocol control block for the TCP connection. + * @param flags TCP header flags to set in the outgoing segment. + */ +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); + LWIP_ASSERT("tcp_enqueue_flags: invalid pcb", pcb != NULL); + + /* No need to check pcb->snd_queuelen if only SYN or FIN are allowed! */ + + /* Get options for this segment. This is a special case since this is the + only place where a SYN can be sent. */ + if (flags & TCP_SYN) { + optflags = TF_SEG_OPTS_MSS; +#if LWIP_WND_SCALE + if ((pcb->state != SYN_RCVD) || (pcb->flags & TF_WND_SCALE)) { + /* In a <SYN,ACK> (sent in state SYN_RCVD), the window scale option may only + be sent if we received a window scale option from the remote host. */ + optflags |= TF_SEG_OPTS_WND_SCALE; + } +#endif /* LWIP_WND_SCALE */ +#if LWIP_TCP_SACK_OUT + if ((pcb->state != SYN_RCVD) || (pcb->flags & TF_SACK)) { + /* In a <SYN,ACK> (sent in state SYN_RCVD), the SACK_PERM option may only + be sent if we received a SACK_PERM option from the remote host. */ + optflags |= TF_SEG_OPTS_SACK_PERM; + } +#endif /* LWIP_TCP_SACK_OUT */ + } +#if LWIP_TCP_TIMESTAMPS + if ((pcb->flags & TF_TIMESTAMP) || ((flags & TCP_SYN) && (pcb->state != SYN_RCVD))) { + /* Make sure the timestamp option is only included in data segments if we + agreed about it with the remote host (and in active open SYN segments). */ + optflags |= TF_SEG_OPTS_TS; + } +#endif /* LWIP_TCP_TIMESTAMPS */ + optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(optflags, pcb); + + /* Allocate pbuf with room for TCP header + options */ + if ((p = pbuf_alloc(PBUF_TRANSPORT, optlen, PBUF_RAM)) == NULL) { + tcp_set_flags(pcb, 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) { + tcp_set_flags(pcb, TF_NAGLEMEMERR); + TCP_STATS_INC(tcp.memerr); + return ERR_MEM; + } + LWIP_ASSERT("seg->tcphdr not aligned", ((mem_ptr_t)seg->tcphdr % LWIP_MIN(MEM_ALIGNMENT, 4)) == 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", + lwip_ntohl(seg->tcphdr->seqno), + lwip_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 */ + } + if (flags & TCP_FIN) { + tcp_set_flags(pcb, 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(const struct tcp_pcb *pcb, u32_t *opts) +{ + LWIP_ASSERT("tcp_build_timestamp_option: invalid pcb", pcb != NULL); + + /* Pad with two NOP options to make everything nicely aligned */ + opts[0] = PP_HTONL(0x0101080A); + opts[1] = lwip_htonl(sys_now()); + opts[2] = lwip_htonl(pcb->ts_recent); +} +#endif + +#if LWIP_TCP_SACK_OUT +/** + * Calculates the number of SACK entries that should be generated. + * It takes into account whether TF_SACK flag is set, + * the number of SACK entries in tcp_pcb that are valid, + * as well as the available options size. + * + * @param pcb tcp_pcb + * @param optlen the length of other TCP options (in bytes) + * @return the number of SACK ranges that can be used + */ +static u8_t +tcp_get_num_sacks(const struct tcp_pcb *pcb, u8_t optlen) +{ + u8_t num_sacks = 0; + + LWIP_ASSERT("tcp_get_num_sacks: invalid pcb", pcb != NULL); + + if (pcb->flags & TF_SACK) { + u8_t i; + + /* The first SACK takes up 12 bytes (it includes SACK header and two NOP options), + each additional one - 8 bytes. */ + optlen += 12; + + /* Max options size = 40, number of SACK array entries = LWIP_TCP_MAX_SACK_NUM */ + for (i = 0; (i < LWIP_TCP_MAX_SACK_NUM) && (optlen <= TCP_MAX_OPTION_BYTES) && + LWIP_TCP_SACK_VALID(pcb, i); ++i) { + ++num_sacks; + optlen += 8; + } + } + + return num_sacks; +} + +/** Build a SACK option (12 or more bytes long) at the specified options pointer) + * + * @param pcb tcp_pcb + * @param opts option pointer where to store the SACK option + * @param num_sacks the number of SACKs to store + */ +static void +tcp_build_sack_option(const struct tcp_pcb *pcb, u32_t *opts, u8_t num_sacks) +{ + u8_t i; + + LWIP_ASSERT("tcp_build_sack_option: invalid pcb", pcb != NULL); + LWIP_ASSERT("tcp_build_sack_option: invalid opts", opts != NULL); + + /* Pad with two NOP options to make everything nicely aligned. + We add the length (of just the SACK option, not the NOPs in front of it), + which is 2B of header, plus 8B for each SACK. */ + *(opts++) = PP_HTONL(0x01010500 + 2 + num_sacks * 8); + + for (i = 0; i < num_sacks; ++i) { + *(opts++) = lwip_htonl(pcb->rcv_sacks[i].left); + *(opts++) = lwip_htonl(pcb->rcv_sacks[i].right); + } +} + +#endif + +#if LWIP_WND_SCALE +/** Build a window scale option (3 bytes long) at the specified options pointer) + * + * @param opts option pointer where to store the window scale option + */ +static void +tcp_build_wnd_scale_option(u32_t *opts) +{ + LWIP_ASSERT("tcp_build_wnd_scale_option: invalid opts", opts != NULL); + + /* Pad with one NOP option to make everything nicely aligned */ + opts[0] = PP_HTONL(0x01030300 | TCP_RCV_SCALE); +} +#endif + +/** + * @ingroup tcp_raw + * 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; + err_t err; + struct netif *netif; +#if TCP_CWND_DEBUG + s16_t i = 0; +#endif /* TCP_CWND_DEBUG */ + + LWIP_ASSERT_CORE_LOCKED(); + + LWIP_ASSERT("tcp_output: invalid pcb", pcb != NULL); + /* pcb->state LISTEN not allowed here */ + LWIP_ASSERT("don't call tcp_output for listen-pcbs", + pcb->state != LISTEN); + + /* 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 (seg == NULL) { + LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: nothing to send (%p)\n", + (void *)pcb->unsent)); + LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %"TCPWNDSIZE_F + ", cwnd %"TCPWNDSIZE_F", wnd %"U32_F + ", seg == NULL, ack %"U32_F"\n", + pcb->snd_wnd, pcb->cwnd, wnd, pcb->lastack)); + + /* If the TF_ACK_NOW flag is set and the ->unsent queue is empty, construct + * an empty ACK segment and send it. */ + if (pcb->flags & TF_ACK_NOW) { + return tcp_send_empty_ack(pcb); + } + /* nothing to send: shortcut out of here */ + goto output_done; + } else { + LWIP_DEBUGF(TCP_CWND_DEBUG, + ("tcp_output: snd_wnd %"TCPWNDSIZE_F", cwnd %"TCPWNDSIZE_F", wnd %"U32_F + ", effwnd %"U32_F", seq %"U32_F", ack %"U32_F"\n", + pcb->snd_wnd, pcb->cwnd, wnd, + lwip_ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len, + lwip_ntohl(seg->tcphdr->seqno), pcb->lastack)); + } + + netif = tcp_route(pcb, &pcb->local_ip, &pcb->remote_ip); + if (netif == NULL) { + return ERR_RTE; + } + + /* If we don't have a local IP address, we get one from netif */ + if (ip_addr_isany(&pcb->local_ip)) { + const ip_addr_t *local_ip = ip_netif_get_local_ip(netif, &pcb->remote_ip); + if (local_ip == NULL) { + return ERR_RTE; + } + ip_addr_copy(pcb->local_ip, *local_ip); + } + + /* Handle the current segment not fitting within the window */ + if (lwip_ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > wnd) { + /* We need to start the persistent timer when the next unsent segment does not fit + * within the remaining (could be 0) send window and RTO timer is not running (we + * have no in-flight data). If window is still too small after persist timer fires, + * then we split the segment. We don't consider the congestion window since a cwnd + * smaller than 1 SMSS implies in-flight data + */ + if (wnd == pcb->snd_wnd && pcb->unacked == NULL && pcb->persist_backoff == 0) { + pcb->persist_cnt = 0; + pcb->persist_backoff = 1; + pcb->persist_probe = 0; + } + /* We need an ACK, but can't send data now, so send an empty ACK */ + if (pcb->flags & TF_ACK_NOW) { + return tcp_send_empty_ack(pcb); + } + goto output_done; + } + /* Stop persist timer, above conditions are not active */ + pcb->persist_backoff = 0; + + /* useg should point to last segment on unacked queue */ + useg = pcb->unacked; + if (useg != NULL) { + for (; useg->next != NULL; useg = useg->next); + } + /* data available and window allows it to be sent? */ + while (seg != NULL && + lwip_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 %"TCPWNDSIZE_F", cwnd %"TCPWNDSIZE_F", wnd %"U32_F", effwnd %"U32_F", seq %"U32_F", ack %"U32_F", i %"S16_F"\n", + pcb->snd_wnd, pcb->cwnd, wnd, + lwip_ntohl(seg->tcphdr->seqno) + seg->len - + pcb->lastack, + lwip_ntohl(seg->tcphdr->seqno), pcb->lastack, i)); + ++i; +#endif /* TCP_CWND_DEBUG */ + + if (pcb->state != SYN_SENT) { + TCPH_SET_FLAG(seg->tcphdr, TCP_ACK); + } + + err = tcp_output_segment(seg, pcb, netif); + if (err != ERR_OK) { + /* segment could not be sent, for whatever reason */ + tcp_set_flags(pcb, TF_NAGLEMEMERR); + return err; + } +#if TCP_OVERSIZE_DBGCHECK + seg->oversize_left = 0; +#endif /* TCP_OVERSIZE_DBGCHECK */ + pcb->unsent = seg->next; + if (pcb->state != SYN_SENT) { + tcp_clear_flags(pcb, TF_ACK_DELAY | TF_ACK_NOW); + } + snd_nxt = lwip_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(lwip_ntohl(seg->tcphdr->seqno), lwip_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(lwip_ntohl((*cur_seg)->tcphdr->seqno), lwip_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 */ + +output_done: + tcp_clear_flags(pcb, TF_NAGLEMEMERR); + return ERR_OK; +} + +/** Check if a segment's pbufs are used by someone else than TCP. + * This can happen on retransmission if the pbuf of this segment is still + * referenced by the netif driver due to deferred transmission. + * This is the case (only!) if someone down the TX call path called + * pbuf_ref() on one of the pbufs! + * + * @arg seg the tcp segment to check + * @return 1 if ref != 1, 0 if ref == 1 + */ +static int +tcp_output_segment_busy(const struct tcp_seg *seg) +{ + LWIP_ASSERT("tcp_output_segment_busy: invalid seg", seg != NULL); + + /* We only need to check the first pbuf here: + If a pbuf is queued for transmission, a driver calls pbuf_ref(), + which only changes the ref count of the first pbuf */ + if (seg->p->ref != 1) { + /* other reference found */ + return 1; + } + /* no other references found */ + return 0; +} + +/** + * 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 + * @param netif the netif used to send the segment + */ +static err_t +tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb, struct netif *netif) +{ + err_t err; + u16_t len; + u32_t *opts; +#if TCP_CHECKSUM_ON_COPY + int seg_chksum_was_swapped = 0; +#endif + + LWIP_ASSERT("tcp_output_segment: invalid seg", seg != NULL); + LWIP_ASSERT("tcp_output_segment: invalid pcb", pcb != NULL); + LWIP_ASSERT("tcp_output_segment: invalid netif", netif != NULL); + + if (tcp_output_segment_busy(seg)) { + /* This should not happen: rexmit functions should have checked this. + However, since this function modifies p->len, we must not continue in this case. */ + LWIP_DEBUGF(TCP_RTO_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("tcp_output_segment: segment busy\n")); + return ERR_OK; + } + + /* The TCP header has already been constructed, but the ackno and + wnd fields remain. */ + seg->tcphdr->ackno = lwip_htonl(pcb->rcv_nxt); + + /* advertise our receive window size in this TCP segment */ +#if LWIP_WND_SCALE + if (seg->flags & TF_SEG_OPTS_WND_SCALE) { + /* The Window field in a SYN segment itself (the only type where we send + the window scale option) is never scaled. */ + seg->tcphdr->wnd = lwip_htons(TCPWND_MIN16(pcb->rcv_ann_wnd)); + } else +#endif /* LWIP_WND_SCALE */ + { + seg->tcphdr->wnd = lwip_htons(TCPWND_MIN16(RCV_WND_SCALE(pcb, 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 */ + /* cast through void* to get rid of alignment warnings */ + opts = (u32_t *)(void *)(seg->tcphdr + 1); + if (seg->flags & TF_SEG_OPTS_MSS) { + u16_t mss; +#if TCP_CALCULATE_EFF_SEND_MSS + mss = tcp_eff_send_mss_netif(TCP_MSS, netif, &pcb->remote_ip); +#else /* TCP_CALCULATE_EFF_SEND_MSS */ + mss = TCP_MSS; +#endif /* TCP_CALCULATE_EFF_SEND_MSS */ + *opts = TCP_BUILD_MSS_OPTION(mss); + 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 +#if LWIP_WND_SCALE + if (seg->flags & TF_SEG_OPTS_WND_SCALE) { + tcp_build_wnd_scale_option(opts); + opts += 1; + } +#endif +#if LWIP_TCP_SACK_OUT + if (seg->flags & TF_SEG_OPTS_SACK_PERM) { + /* Pad with two NOP options to make everything nicely aligned + * NOTE: When we send both timestamp and SACK_PERM options, + * we could use the first two NOPs before the timestamp to store SACK_PERM option, + * but that would complicate the code. + */ + *(opts++) = PP_HTONL(0x01010402); + } +#endif + + /* Set retransmission timer running if it is not currently enabled + This must be set before checking the route. */ + if (pcb->rtime < 0) { + pcb->rtime = 0; + } + + if (pcb->rttest == 0) { + pcb->rttest = tcp_ticks; + pcb->rtseq = lwip_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", + lwip_htonl(seg->tcphdr->seqno), lwip_htonl(seg->tcphdr->seqno) + + seg->len)); + + len = (u16_t)((u8_t *)seg->tcphdr - (u8_t *)seg->p->payload); + if (len == 0) { + /** Exclude retransmitted segments from this count. */ + MIB2_STATS_INC(mib2.tcpoutsegs); + } + + seg->p->len -= len; + seg->p->tot_len -= len; + + seg->p->payload = seg->tcphdr; + + seg->tcphdr->chksum = 0; + +#ifdef LWIP_HOOK_TCP_OUT_ADD_TCPOPTS + opts = LWIP_HOOK_TCP_OUT_ADD_TCPOPTS(seg->p, seg->tcphdr, pcb, opts); +#endif + LWIP_ASSERT("options not filled", (u8_t *)opts == ((u8_t *)(seg->tcphdr + 1)) + LWIP_TCP_OPT_LENGTH_SEGMENT(seg->flags, pcb)); + +#if CHECKSUM_GEN_TCP + IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_TCP) { +#if TCP_CHECKSUM_ON_COPY + u32_t acc; +#if TCP_CHECKSUM_ON_COPY_SANITY_CHECK + u16_t chksum_slow = ip_chksum_pseudo(seg->p, IP_PROTO_TCP, + seg->p->tot_len, &pcb->local_ip, &pcb->remote_ip); +#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_BYTES(seg->tcphdr)); + } + + /* rebuild TCP header checksum (TCP header changes for retransmissions!) */ + acc = ip_chksum_pseudo_partial(seg->p, IP_PROTO_TCP, + seg->p->tot_len, TCPH_HDRLEN_BYTES(seg->tcphdr), &pcb->local_ip, &pcb->remote_ip); + /* add payload checksum */ + if (seg->chksum_swapped) { + seg_chksum_was_swapped = 1; + seg->chksum = SWAP_BYTES_IN_WORD(seg->chksum); + seg->chksum_swapped = 0; + } + acc = (u16_t)~acc + seg->chksum; + seg->tcphdr->chksum = (u16_t)~FOLD_U32T(acc); +#if TCP_CHECKSUM_ON_COPY_SANITY_CHECK + if (chksum_slow != seg->tcphdr->chksum) { + TCP_CHECKSUM_ON_COPY_SANITY_CHECK_FAIL( + ("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 = ip_chksum_pseudo(seg->p, IP_PROTO_TCP, + seg->p->tot_len, &pcb->local_ip, &pcb->remote_ip); +#endif /* TCP_CHECKSUM_ON_COPY */ + } +#endif /* CHECKSUM_GEN_TCP */ + TCP_STATS_INC(tcp.xmit); + + NETIF_SET_HINTS(netif, &(pcb->netif_hints)); + err = ip_output_if(seg->p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, + pcb->tos, IP_PROTO_TCP, netif); + NETIF_RESET_HINTS(netif); + +#if TCP_CHECKSUM_ON_COPY + if (seg_chksum_was_swapped) { + /* if data is added to this segment later, chksum needs to be swapped, + so restore this now */ + seg->chksum = SWAP_BYTES_IN_WORD(seg->chksum); + seg->chksum_swapped = 1; + } +#endif + + return err; +} + +/** + * 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 + */ +err_t +tcp_rexmit_rto_prepare(struct tcp_pcb *pcb) +{ + struct tcp_seg *seg; + + LWIP_ASSERT("tcp_rexmit_rto_prepare: invalid pcb", pcb != NULL); + + if (pcb->unacked == NULL) { + return ERR_VAL; + } + + /* Move all unacked segments to the head of the unsent queue. + However, give up if any of the unsent pbufs are still referenced by the + netif driver due to deferred transmission. No point loading the link further + if it is struggling to flush its buffered writes. */ + for (seg = pcb->unacked; seg->next != NULL; seg = seg->next) { + if (tcp_output_segment_busy(seg)) { + LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_rexmit_rto: segment busy\n")); + return ERR_VAL; + } + } + if (tcp_output_segment_busy(seg)) { + LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_rexmit_rto: segment busy\n")); + return ERR_VAL; + } + /* concatenate unsent queue after unacked queue */ + seg->next = pcb->unsent; +#if TCP_OVERSIZE_DBGCHECK + /* if last unsent changed, we need to update unsent_oversize */ + if (pcb->unsent == NULL) { + pcb->unsent_oversize = seg->oversize_left; + } +#endif /* TCP_OVERSIZE_DBGCHECK */ + /* unsent queue is the concatenated queue (of unacked, unsent) */ + pcb->unsent = pcb->unacked; + /* unacked queue is now empty */ + pcb->unacked = NULL; + + /* Mark RTO in-progress */ + tcp_set_flags(pcb, TF_RTO); + /* Record the next byte following retransmit */ + pcb->rto_end = lwip_ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg); + /* Don't take any RTT measurements after retransmitting. */ + pcb->rttest = 0; + + return ERR_OK; +} + +/** + * 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_commit(struct tcp_pcb *pcb) +{ + LWIP_ASSERT("tcp_rexmit_rto_commit: invalid pcb", pcb != NULL); + + /* increment number of retransmissions */ + if (pcb->nrtx < 0xFF) { + ++pcb->nrtx; + } + /* Do the actual retransmission */ + tcp_output(pcb); +} + +/** + * Requeue all unacked segments for retransmission + * + * Called by tcp_process() only, tcp_slowtmr() needs to do some things between + * "prepare" and "commit". + * + * @param pcb the tcp_pcb for which to re-enqueue all unacked segments + */ +void +tcp_rexmit_rto(struct tcp_pcb *pcb) +{ + LWIP_ASSERT("tcp_rexmit_rto: invalid pcb", pcb != NULL); + + if (tcp_rexmit_rto_prepare(pcb) == ERR_OK) { + tcp_rexmit_rto_commit(pcb); + } +} + +/** + * Requeue the first unacked segment for retransmission + * + * Called by tcp_receive() for fast retransmit. + * + * @param pcb the tcp_pcb for which to retransmit the first unacked segment + */ +err_t +tcp_rexmit(struct tcp_pcb *pcb) +{ + struct tcp_seg *seg; + struct tcp_seg **cur_seg; + + LWIP_ASSERT("tcp_rexmit: invalid pcb", pcb != NULL); + + if (pcb->unacked == NULL) { + return ERR_VAL; + } + + seg = pcb->unacked; + + /* Give up if the segment is still referenced by the netif driver + due to deferred transmission. */ + if (tcp_output_segment_busy(seg)) { + LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_rexmit busy\n")); + return ERR_VAL; + } + + /* Move the first unacked segment to the unsent queue */ + /* Keep the unsent queue sorted. */ + pcb->unacked = seg->next; + + cur_seg = &(pcb->unsent); + while (*cur_seg && + TCP_SEQ_LT(lwip_ntohl((*cur_seg)->tcphdr->seqno), lwip_ntohl(seg->tcphdr->seqno))) { + cur_seg = &((*cur_seg)->next ); + } + seg->next = *cur_seg; + *cur_seg = seg; +#if TCP_OVERSIZE + if (seg->next == NULL) { + /* the retransmitted segment is last in unsent, so reset unsent_oversize */ + pcb->unsent_oversize = 0; + } +#endif /* TCP_OVERSIZE */ + + if (pcb->nrtx < 0xFF) { + ++pcb->nrtx; + } + + /* Don't take any rtt measurements after retransmitting. */ + pcb->rttest = 0; + + /* Do the actual retransmission. */ + MIB2_STATS_INC(mib2.tcpretranssegs); + /* No need to call tcp_output: we are always called from tcp_input() + and thus tcp_output directly returns. */ + return ERR_OK; +} + + +/** + * 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) +{ + LWIP_ASSERT("tcp_rexmit_fast: invalid pcb", pcb != NULL); + + 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, + lwip_ntohl(pcb->unacked->tcphdr->seqno))); + if (tcp_rexmit(pcb) == ERR_OK) { + /* Set ssthresh to half of the minimum of the current + * cwnd and the advertised window */ + pcb->ssthresh = LWIP_MIN(pcb->cwnd, pcb->snd_wnd) / 2; + + /* The minimum value for ssthresh should be 2 MSS */ + if (pcb->ssthresh < (2U * pcb->mss)) { + LWIP_DEBUGF(TCP_FR_DEBUG, + ("tcp_receive: The minimum value for ssthresh %"TCPWNDSIZE_F + " should be min 2 mss %"U16_F"...\n", + pcb->ssthresh, (u16_t)(2 * pcb->mss))); + pcb->ssthresh = 2 * pcb->mss; + } + + pcb->cwnd = pcb->ssthresh + 3 * pcb->mss; + tcp_set_flags(pcb, TF_INFR); + + /* Reset the retransmission timer to prevent immediate rto retransmissions */ + pcb->rtime = 0; + } + } +} + +static struct pbuf * +tcp_output_alloc_header_common(u32_t ackno, u16_t optlen, u16_t datalen, + u32_t seqno_be /* already in network byte order */, + u16_t src_port, u16_t dst_port, u8_t flags, u16_t wnd) +{ + struct tcp_hdr *tcphdr; + struct pbuf *p; + + 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 = lwip_htons(src_port); + tcphdr->dest = lwip_htons(dst_port); + tcphdr->seqno = seqno_be; + tcphdr->ackno = lwip_htonl(ackno); + TCPH_HDRLEN_FLAGS_SET(tcphdr, (5 + optlen / 4), flags); + tcphdr->wnd = lwip_htons(wnd); + tcphdr->chksum = 0; + tcphdr->urgp = 0; + } + return p; +} + +/** 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 pbuf *p; + + LWIP_ASSERT("tcp_output_alloc_header: invalid pcb", pcb != NULL); + + p = tcp_output_alloc_header_common(pcb->rcv_nxt, optlen, datalen, + seqno_be, pcb->local_port, pcb->remote_port, TCP_ACK, + TCPWND_MIN16(RCV_WND_SCALE(pcb, pcb->rcv_ann_wnd))); + if (p != NULL) { + /* 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; +} + +/* Fill in options for control segments */ +static void +tcp_output_fill_options(const struct tcp_pcb *pcb, struct pbuf *p, u8_t optflags, u8_t num_sacks) +{ + struct tcp_hdr *tcphdr; + u32_t *opts; + u16_t sacks_len = 0; + + LWIP_ASSERT("tcp_output_fill_options: invalid pbuf", p != NULL); + + tcphdr = (struct tcp_hdr *)p->payload; + opts = (u32_t *)(void *)(tcphdr + 1); + + /* NB. MSS and window scale options are only sent on SYNs, so ignore them here */ + +#if LWIP_TCP_TIMESTAMPS + if (optflags & TF_SEG_OPTS_TS) { + tcp_build_timestamp_option(pcb, opts); + opts += 3; + } +#endif + +#if LWIP_TCP_SACK_OUT + if (pcb && (num_sacks > 0)) { + tcp_build_sack_option(pcb, opts, num_sacks); + /* 1 word for SACKs header (including 2xNOP), and 2 words for each SACK */ + sacks_len = 1 + num_sacks * 2; + opts += sacks_len; + } +#else + LWIP_UNUSED_ARG(num_sacks); +#endif + +#ifdef LWIP_HOOK_TCP_OUT_ADD_TCPOPTS + opts = LWIP_HOOK_TCP_OUT_ADD_TCPOPTS(p, tcphdr, pcb, opts); +#endif + + LWIP_UNUSED_ARG(pcb); + LWIP_UNUSED_ARG(sacks_len); + LWIP_ASSERT("options not filled", (u8_t *)opts == ((u8_t *)(tcphdr + 1)) + sacks_len * 4 + LWIP_TCP_OPT_LENGTH_SEGMENT(optflags, pcb)); + LWIP_UNUSED_ARG(optflags); /* for LWIP_NOASSERT */ + LWIP_UNUSED_ARG(opts); /* for LWIP_NOASSERT */ +} + +/** Output a control segment pbuf to IP. + * + * Called from tcp_rst, tcp_send_empty_ack, tcp_keepalive and tcp_zero_window_probe, + * this function combines selecting a netif for transmission, generating the tcp + * header checksum and calling ip_output_if while handling netif hints and stats. + */ +static err_t +tcp_output_control_segment(const struct tcp_pcb *pcb, struct pbuf *p, + const ip_addr_t *src, const ip_addr_t *dst) +{ + err_t err; + struct netif *netif; + + LWIP_ASSERT("tcp_output_control_segment: invalid pbuf", p != NULL); + + netif = tcp_route(pcb, src, dst); + if (netif == NULL) { + err = ERR_RTE; + } else { + u8_t ttl, tos; +#if CHECKSUM_GEN_TCP + IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_TCP) { + struct tcp_hdr *tcphdr = (struct tcp_hdr *)p->payload; + tcphdr->chksum = ip_chksum_pseudo(p, IP_PROTO_TCP, p->tot_len, + src, dst); + } +#endif + if (pcb != NULL) { + NETIF_SET_HINTS(netif, LWIP_CONST_CAST(struct netif_hint*, &(pcb->netif_hints))); + ttl = pcb->ttl; + tos = pcb->tos; + } else { + /* Send output with hardcoded TTL/HL since we have no access to the pcb */ + ttl = TCP_TTL; + tos = 0; + } + TCP_STATS_INC(tcp.xmit); + err = ip_output_if(p, src, dst, ttl, tos, IP_PROTO_TCP, netif); + NETIF_RESET_HINTS(netif); + } + pbuf_free(p); + return err; +} + +/** + * 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 pcb TCP pcb (may be NULL if no pcb is available) + * @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(const struct tcp_pcb *pcb, u32_t seqno, u32_t ackno, + const ip_addr_t *local_ip, const ip_addr_t *remote_ip, + u16_t local_port, u16_t remote_port) +{ + struct pbuf *p; + u16_t wnd; + u8_t optlen; + + LWIP_ASSERT("tcp_rst: invalid local_ip", local_ip != NULL); + LWIP_ASSERT("tcp_rst: invalid remote_ip", remote_ip != NULL); + + optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(0, pcb); + +#if LWIP_WND_SCALE + wnd = PP_HTONS(((TCP_WND >> TCP_RCV_SCALE) & 0xFFFF)); +#else + wnd = PP_HTONS(TCP_WND); +#endif + + p = tcp_output_alloc_header_common(ackno, optlen, 0, lwip_htonl(seqno), local_port, + remote_port, TCP_RST | TCP_ACK, wnd); + if (p == NULL) { + LWIP_DEBUGF(TCP_DEBUG, ("tcp_rst: could not allocate memory for pbuf\n")); + return; + } + tcp_output_fill_options(pcb, p, 0, optlen); + + MIB2_STATS_INC(mib2.tcpoutrsts); + + tcp_output_control_segment(pcb, p, local_ip, remote_ip); + LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_rst: seqno %"U32_F" ackno %"U32_F".\n", seqno, ackno)); +} + +/** + * 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) +{ + err_t err; + struct pbuf *p; + u8_t optlen, optflags = 0; + u8_t num_sacks = 0; + + LWIP_ASSERT("tcp_send_empty_ack: invalid pcb", pcb != NULL); + +#if LWIP_TCP_TIMESTAMPS + if (pcb->flags & TF_TIMESTAMP) { + optflags = TF_SEG_OPTS_TS; + } +#endif + optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(optflags, pcb); + +#if LWIP_TCP_SACK_OUT + /* For now, SACKs are only sent with empty ACKs */ + if ((num_sacks = tcp_get_num_sacks(pcb, optlen)) > 0) { + optlen += 4 + num_sacks * 8; /* 4 bytes for header (including 2*NOP), plus 8B for each SACK */ + } +#endif + + p = tcp_output_alloc_header(pcb, optlen, 0, lwip_htonl(pcb->snd_nxt)); + if (p == NULL) { + /* let tcp_fasttmr retry sending this ACK */ + tcp_set_flags(pcb, TF_ACK_DELAY | TF_ACK_NOW); + LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: (ACK) could not allocate pbuf\n")); + return ERR_BUF; + } + tcp_output_fill_options(pcb, p, optflags, num_sacks); + +#if LWIP_TCP_TIMESTAMPS + pcb->ts_lastacksent = pcb->rcv_nxt; +#endif + + LWIP_DEBUGF(TCP_OUTPUT_DEBUG, + ("tcp_output: sending ACK for %"U32_F"\n", pcb->rcv_nxt)); + err = tcp_output_control_segment(pcb, p, &pcb->local_ip, &pcb->remote_ip); + if (err != ERR_OK) { + /* let tcp_fasttmr retry sending this ACK */ + tcp_set_flags(pcb, TF_ACK_DELAY | TF_ACK_NOW); + } else { + /* remove ACK flags from the PCB, as we sent an empty ACK now */ + tcp_clear_flags(pcb, TF_ACK_DELAY | TF_ACK_NOW); + } + + return err; +} + +/** + * 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 + */ +err_t +tcp_keepalive(struct tcp_pcb *pcb) +{ + err_t err; + struct pbuf *p; + u8_t optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(0, pcb); + + LWIP_ASSERT("tcp_keepalive: invalid pcb", pcb != NULL); + + LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: sending KEEPALIVE probe to ")); + ip_addr_debug_print_val(TCP_DEBUG, pcb->remote_ip); + LWIP_DEBUGF(TCP_DEBUG, ("\n")); + + 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, (u16_t)pcb->keep_cnt_sent)); + + p = tcp_output_alloc_header(pcb, optlen, 0, lwip_htonl(pcb->snd_nxt - 1)); + if (p == NULL) { + LWIP_DEBUGF(TCP_DEBUG, + ("tcp_keepalive: could not allocate memory for pbuf\n")); + return ERR_MEM; + } + tcp_output_fill_options(pcb, p, 0, optlen); + err = tcp_output_control_segment(pcb, p, &pcb->local_ip, &pcb->remote_ip); + + LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: seqno %"U32_F" ackno %"U32_F" err %d.\n", + pcb->snd_nxt - 1, pcb->rcv_nxt, (int)err)); + return err; +} + +/** + * 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 + */ +err_t +tcp_zero_window_probe(struct tcp_pcb *pcb) +{ + err_t err; + struct pbuf *p; + struct tcp_hdr *tcphdr; + struct tcp_seg *seg; + u16_t len; + u8_t is_fin; + u32_t snd_nxt; + u8_t optlen = LWIP_TCP_OPT_LENGTH_SEGMENT(0, pcb); + + LWIP_ASSERT("tcp_zero_window_probe: invalid pcb", pcb != NULL); + + LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: sending ZERO WINDOW probe to ")); + ip_addr_debug_print_val(TCP_DEBUG, pcb->remote_ip); + LWIP_DEBUGF(TCP_DEBUG, ("\n")); + + 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, (u16_t)pcb->keep_cnt_sent)); + + /* Only consider unsent, persist timer should be off when there is data in-flight */ + seg = pcb->unsent; + if (seg == NULL) { + /* Not expected, persist timer should be off when the send buffer is empty */ + return ERR_OK; + } + + /* increment probe count. NOTE: we record probe even if it fails + to actually transmit due to an error. This ensures memory exhaustion/ + routing problem doesn't leave a zero-window pcb as an indefinite zombie. + RTO mechanism has similar behavior, see pcb->nrtx */ + if (pcb->persist_probe < 0xFF) { + ++pcb->persist_probe; + } + + 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, optlen, len, seg->tcphdr->seqno); + if (p == NULL) { + LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: no memory for pbuf\n")); + return ERR_MEM; + } + 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 */ + char *d = ((char *)p->payload + TCP_HLEN); + /* Depending on whether the segment has already been sent (unacked) or not + (unsent), seg->p->payload points to the IP header or TCP header. + Ensure we copy the first TCP data byte: */ + pbuf_copy_partial(seg->p, d, 1, seg->p->tot_len - seg->len); + } + + /* The byte may be acknowledged without the window being opened. */ + snd_nxt = lwip_ntohl(seg->tcphdr->seqno) + 1; + if (TCP_SEQ_LT(pcb->snd_nxt, snd_nxt)) { + pcb->snd_nxt = snd_nxt; + } + tcp_output_fill_options(pcb, p, 0, optlen); + + err = tcp_output_control_segment(pcb, p, &pcb->local_ip, &pcb->remote_ip); + + LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: seqno %"U32_F + " ackno %"U32_F" err %d.\n", + pcb->snd_nxt - 1, pcb->rcv_nxt, (int)err)); + return err; +} +#endif /* LWIP_TCP */ |