/** 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 = tcp_tx_pbuf_alloc(pcb, optlen + datalen, PBUF_RAM);
if (p != NULL) {
pbuf_header(p, TCP_HLEN);
LWIP_ASSERT("check that first pbuf can hold struct tcp_hdr",
(p->len >= TCP_HLEN + optlen));
tcphdr = (struct tcp_hdr *)p->payload;
tcphdr->src = htons(pcb->local_port);
tcphdr->dest = htons(pcb->remote_port);
tcphdr->seqno = seqno_be;
tcphdr->ackno = htonl(pcb->rcv_nxt);
TCPH_HDRLEN_FLAGS_SET(tcphdr, (5 + optlen / 4), TCP_ACK);
tcphdr->wnd = RCV_WND_SCALE(pcb, pcb->rcv_ann_wnd); // Which means: htons(pcb->rcv_ann_wnd >> pcb->rcv_scale);
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;
}
/** 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->connid1 = htonl(pcb->conn_id.connid1);
tcphdr->connid2 = htonl(pcb->conn_id.connid2);
tcphdr->seqno = seqno_be;
tcphdr->ackno = htonl(pcb->rcv_nxt);
TCPH_HDRLEN_FLAGS_SET(tcphdr, (5 + optlen / 4), TCP_ACK);
tcphdr->wnd = htons(TCPWND_MIN16(RCV_WND_SCALE(pcb, pcb->rcv_ann_wnd)));
/* 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_output() to actually send a TCP segment over IP.
*
* @param seg the tcp_seg to send
* @param pcb the tcp_pcb for the TCP connection used to send the segment
*/
static void
tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb)
{
u16_t len;
u32_t *opts;
/* The TCP header has already been constructed, but the ackno and
wnd fields remain. */
seg->tcphdr->ackno = htonl(pcb->rcv_nxt);
/* advertise our receive window size in this TCP segment */
seg->tcphdr->wnd = RCV_WND_SCALE(pcb, pcb->rcv_ann_wnd); // Which means: htons(pcb->rcv_ann_wnd >> pcb->rcv_scale);
pcb->rcv_ann_right_edge = pcb->rcv_nxt + pcb->rcv_ann_wnd;
/* Add any requested options. NB MSS option is only set on SYN
packets, so ignore it here */
LWIP_ASSERT("seg->tcphdr not aligned", ((mem_ptr_t)(seg->tcphdr + 1) % 4) == 0);
opts = (u32_t *)(void *)(seg->tcphdr + 1);
if (seg->flags & TF_SEG_OPTS_MSS) {
TCP_BUILD_MSS_OPTION(*opts, pcb->advtsd_mss);
opts += 1; // Move to the next line (meaning next 32 bit) as this option is 4 bytes long
}
/* If RCV_SCALE is set then prepare segment for window scaling option */
if (seg->flags & TF_SEG_OPTS_WNDSCALE) {
TCP_BUILD_WNDSCALE_OPTION(*opts, pcb->rcv_scale);
opts += 1; // Move to the next line (meaning next 32 bit) as this option is 3 bytes long + we added 1 byte NOOP padding => total 4 bytes
}
#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; // Move to the next line (meaning next 32 bit) as this option is 10 bytes long, 12 with padding (so jump 3 lines)
}
#endif
/* If we don't have a local IP address, we get one by
calling ip_route(). */
if (ip_addr_isany(&(pcb->local_ip))) {
LWIP_ASSERT("tcp_output_segment: need to find route to host", 0);
}
/* Set retransmission timer running if it is not currently enabled */
if(pcb->rtime == -1) {
pcb->rtime = 0;
}
if (pcb->rttest == 0) {
pcb->rttest = tcp_ticks;
pcb->rtseq = seg->seqno;
LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_output_segment: rtseq %"U32_F"\n", pcb->rtseq));
}
LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output_segment: %"U32_F":%"U32_F"\n",
htonl(seg->tcphdr->seqno), htonl(seg->tcphdr->seqno) +
seg->len));
len = (u16_t)((u8_t *)seg->tcphdr - (u8_t *)seg->p->payload);
seg->p->len -= len;
seg->p->tot_len -= len;
seg->p->payload = seg->tcphdr;
seg->tcphdr->chksum = 0;
TCP_STATS_INC(tcp.xmit);
#if LWIP_NETIF_HWADDRHINT
ip_output_hinted(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
IP_PROTO_TCP, &(pcb->addr_hint));
#elif LWIP_3RD_PARTY_L3
pcb->ip_output(seg->p, pcb, seg->seqno < pcb->snd_nxt);
#else /* LWIP_NETIF_HWADDRHINT*/
ip_output(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos, IP_PROTO_TCP);
#endif /* LWIP_NETIF_HWADDRHINT*/
}
