diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c index ddece521..9be2a309 100644 --- a/src/core/tcp_out.c +++ b/src/core/tcp_out.c @@ -14,13 +14,18 @@ * - @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 - * - @ref tcp_rst - * - @ref tcp_keepalive - * - @ref tcp_zero_window_probe + * - @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 */ /* @@ -124,69 +129,6 @@ tcp_route(const struct tcp_pcb *pcb, const ip_addr_t *src, const ip_addr_t *dst) } } -/** 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 = lwip_htons(pcb->local_port); - tcphdr->dest = lwip_htons(pcb->remote_port); - tcphdr->seqno = seqno_be; - tcphdr->ackno = lwip_htonl(pcb->rcv_nxt); - TCPH_HDRLEN_FLAGS_SET(tcphdr, (5 + optlen / 4), TCP_ACK); - tcphdr->wnd = lwip_htons(TCPWND_MIN16(RCV_WND_SCALE(pcb, 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. - * 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) -{ - /* 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); -} - /** * Create a TCP segment with prefilled header. * @@ -841,6 +783,212 @@ memerr: 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 */ + + 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 |= 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); + + if (seg != NULL) { + tcp_segs_free(seg); + } + 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) +{ + /* 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. * @@ -1035,106 +1183,6 @@ tcp_build_wnd_scale_option(u32_t *opts) } #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) -{ - err_t err; - struct pbuf *p; - u8_t optlen = 0; - struct netif *netif; -#if CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT - struct tcp_hdr *tcphdr; -#if LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT - u32_t *opts; -#if LWIP_TCP_SACK_OUT - u8_t num_sacks; -#endif /* LWIP_TCP_SACK_OUT */ -#endif /* LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ -#endif /* CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ - -#if LWIP_TCP_TIMESTAMPS - if (pcb->flags & TF_TIMESTAMP) { - optlen = LWIP_TCP_OPT_LENGTH(TF_SEG_OPTS_TS); - } -#endif - -#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; - } - -#if CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT - tcphdr = (struct tcp_hdr *)p->payload; -#if LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT - /* cast through void* to get rid of alignment warnings */ - opts = (u32_t *)(void *)(tcphdr + 1); -#endif /* LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ -#endif /* CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ - - LWIP_DEBUGF(TCP_OUTPUT_DEBUG, - ("tcp_output: sending ACK for %"U32_F"\n", pcb->rcv_nxt)); - - /* NB. MSS and window scale options are only sent on SYNs, so ignore them here */ -#if LWIP_TCP_TIMESTAMPS - pcb->ts_lastacksent = pcb->rcv_nxt; - - if (pcb->flags & TF_TIMESTAMP) { - tcp_build_timestamp_option(pcb, opts); - opts += 3; - } -#endif - -#if LWIP_TCP_SACK_OUT - if (num_sacks > 0) { - tcp_build_sack_option(pcb, opts, num_sacks); - /* 1 word for SACKs header (including 2xNOP), and 2 words for each SACK */ - opts += 1 + num_sacks * 2; - } -#endif - - netif = tcp_route(pcb, &pcb->local_ip, &pcb->remote_ip); - if (netif == NULL) { - err = ERR_RTE; - } else { -#if CHECKSUM_GEN_TCP - IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_TCP) { - tcphdr->chksum = ip_chksum_pseudo(p, IP_PROTO_TCP, p->tot_len, - &pcb->local_ip, &pcb->remote_ip); - } -#endif - NETIF_SET_HINTS(netif, &(pcb->netif_hints)); - err = ip_output_if(p, &pcb->local_ip, &pcb->remote_ip, - pcb->ttl, pcb->tos, IP_PROTO_TCP, netif); - NETIF_RESET_HINTS(netif); - } - pbuf_free(p); - - 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; -} - /** * @ingroup tcp_raw * Find out what we can send and send it @@ -1502,75 +1550,6 @@ tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb, struct netif *netif 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; - struct tcp_hdr *tcphdr; - struct netif *netif; - 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 = lwip_htons(local_port); - tcphdr->dest = lwip_htons(remote_port); - tcphdr->seqno = lwip_htonl(seqno); - tcphdr->ackno = lwip_htonl(ackno); - TCPH_HDRLEN_FLAGS_SET(tcphdr, TCP_HLEN / 4, TCP_RST | TCP_ACK); -#if LWIP_WND_SCALE - tcphdr->wnd = PP_HTONS(((TCP_WND >> TCP_RCV_SCALE) & 0xFFFF)); -#else - tcphdr->wnd = PP_HTONS(TCP_WND); -#endif - tcphdr->chksum = 0; - tcphdr->urgp = 0; - - TCP_STATS_INC(tcp.xmit); - MIB2_STATS_INC(mib2.tcpoutrsts); - - netif = tcp_route(pcb, local_ip, remote_ip); - if (netif != NULL) { -#if CHECKSUM_GEN_TCP - IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_TCP) { - tcphdr->chksum = ip_chksum_pseudo(p, IP_PROTO_TCP, p->tot_len, - local_ip, remote_ip); - } -#endif - /* Send output with hardcoded TTL/HL since we have no access to the pcb */ - ip_output_if(p, local_ip, remote_ip, TCP_TTL, 0, IP_PROTO_TCP, netif); - } - 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 * @@ -1755,6 +1734,209 @@ tcp_rexmit_fast(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 = lwip_htons(pcb->local_port); + tcphdr->dest = lwip_htons(pcb->remote_port); + tcphdr->seqno = seqno_be; + tcphdr->ackno = lwip_htonl(pcb->rcv_nxt); + TCPH_HDRLEN_FLAGS_SET(tcphdr, (5 + optlen / 4), TCP_ACK); + tcphdr->wnd = lwip_htons(TCPWND_MIN16(RCV_WND_SCALE(pcb, 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; +} + +/** + * 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; + struct tcp_hdr *tcphdr; + struct netif *netif; + 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 = lwip_htons(local_port); + tcphdr->dest = lwip_htons(remote_port); + tcphdr->seqno = lwip_htonl(seqno); + tcphdr->ackno = lwip_htonl(ackno); + TCPH_HDRLEN_FLAGS_SET(tcphdr, TCP_HLEN / 4, TCP_RST | TCP_ACK); +#if LWIP_WND_SCALE + tcphdr->wnd = PP_HTONS(((TCP_WND >> TCP_RCV_SCALE) & 0xFFFF)); +#else + tcphdr->wnd = PP_HTONS(TCP_WND); +#endif + tcphdr->chksum = 0; + tcphdr->urgp = 0; + + TCP_STATS_INC(tcp.xmit); + MIB2_STATS_INC(mib2.tcpoutrsts); + + netif = tcp_route(pcb, local_ip, remote_ip); + if (netif != NULL) { +#if CHECKSUM_GEN_TCP + IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_TCP) { + tcphdr->chksum = ip_chksum_pseudo(p, IP_PROTO_TCP, p->tot_len, + local_ip, remote_ip); + } +#endif + /* Send output with hardcoded TTL/HL since we have no access to the pcb */ + ip_output_if(p, local_ip, remote_ip, TCP_TTL, 0, IP_PROTO_TCP, netif); + } + pbuf_free(p); + 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 = 0; + struct netif *netif; +#if CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT + struct tcp_hdr *tcphdr; +#if LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT + u32_t *opts; +#if LWIP_TCP_SACK_OUT + u8_t num_sacks; +#endif /* LWIP_TCP_SACK_OUT */ +#endif /* LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ +#endif /* CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ + +#if LWIP_TCP_TIMESTAMPS + if (pcb->flags & TF_TIMESTAMP) { + optlen = LWIP_TCP_OPT_LENGTH(TF_SEG_OPTS_TS); + } +#endif + +#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; + } + +#if CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT + tcphdr = (struct tcp_hdr *)p->payload; +#if LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT + /* cast through void* to get rid of alignment warnings */ + opts = (u32_t *)(void *)(tcphdr + 1); +#endif /* LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ +#endif /* CHECKSUM_GEN_TCP || LWIP_TCP_TIMESTAMPS || LWIP_TCP_SACK_OUT */ + + LWIP_DEBUGF(TCP_OUTPUT_DEBUG, + ("tcp_output: sending ACK for %"U32_F"\n", pcb->rcv_nxt)); + + /* NB. MSS and window scale options are only sent on SYNs, so ignore them here */ +#if LWIP_TCP_TIMESTAMPS + pcb->ts_lastacksent = pcb->rcv_nxt; + + if (pcb->flags & TF_TIMESTAMP) { + tcp_build_timestamp_option(pcb, opts); + opts += 3; + } +#endif + +#if LWIP_TCP_SACK_OUT + if (num_sacks > 0) { + tcp_build_sack_option(pcb, opts, num_sacks); + /* 1 word for SACKs header (including 2xNOP), and 2 words for each SACK */ + opts += 1 + num_sacks * 2; + } +#endif + + netif = tcp_route(pcb, &pcb->local_ip, &pcb->remote_ip); + if (netif == NULL) { + err = ERR_RTE; + } else { +#if CHECKSUM_GEN_TCP + IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_TCP) { + tcphdr->chksum = ip_chksum_pseudo(p, IP_PROTO_TCP, p->tot_len, + &pcb->local_ip, &pcb->remote_ip); + } +#endif + NETIF_SET_HINTS(netif, &(pcb->netif_hints)); + err = ip_output_if(p, &pcb->local_ip, &pcb->remote_ip, + pcb->ttl, pcb->tos, IP_PROTO_TCP, netif); + NETIF_RESET_HINTS(netif); + } + pbuf_free(p); + + 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 @@ -1809,184 +1991,6 @@ tcp_keepalive(struct tcp_pcb *pcb) return err; } -/** - * 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 */ - - 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 |= 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); - - if (seg != NULL) { - tcp_segs_free(seg); - } - if (p != NULL) { - pbuf_free(p); - } - - return ERR_MEM; -} - /** * Send persist timer zero-window probes to keep a connection active * when a window update is lost.