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BUG20515: rework way TCP window updates are calculated and sent

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This commit is contained in:
kieranm
2009-03-31 14:23:40 +00:00
parent 4b14621208
commit f1a9f7ea70
6 changed files with 90 additions and 74 deletions
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72
src/core/tcp.c
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@@ -383,6 +383,33 @@ tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog)
return (struct tcp_pcb *)lpcb;
}
/**
* Update the state that tracks the available window space to advertise.
*
* Returns how much extra window would be advertised if we sent an
* update now.
*/
u32_t tcp_update_rcv_ann_wnd(struct tcp_pcb *pcb)
{
u32_t new_right_edge = pcb->rcv_nxt + pcb->rcv_wnd;
if (TCP_SEQ_GEQ(new_right_edge, pcb->rcv_ann_right_edge + pcb->mss)) {
/* we can advertise more window */
pcb->rcv_ann_wnd = pcb->rcv_wnd;
return new_right_edge - pcb->rcv_ann_right_edge;
} else {
if (TCP_SEQ_GT(pcb->rcv_nxt, pcb->rcv_ann_right_edge)) {
/* Can happen due to other end sending out of advertised window,
* but within actual available (but not yet advertised) window */
pcb->rcv_ann_wnd = 0;
} else {
/* keep the right edge of window constant */
pcb->rcv_ann_wnd = pcb->rcv_ann_right_edge - pcb->rcv_nxt;
}
return 0;
}
}
/**
* This function should be called by the application when it has
* processed the data. The purpose is to advertise a larger window
@@ -394,40 +421,20 @@ tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog)
void
tcp_recved(struct tcp_pcb *pcb, u16_t len)
{
if ((u32_t)pcb->rcv_wnd + len > TCP_WND) {
pcb->rcv_wnd = TCP_WND;
pcb->rcv_ann_wnd = TCP_WND;
} else {
pcb->rcv_wnd += len;
if (pcb->rcv_wnd >= pcb->mss) {
pcb->rcv_ann_wnd = pcb->rcv_wnd;
}
}
int wnd_inflation;
if (!(pcb->flags & TF_ACK_DELAY) &&
!(pcb->flags & TF_ACK_NOW)) {
/*
* We send an ACK here (if one is not already pending, hence
* the above tests) as tcp_recved() implies that the application
* has processed some data, and so we can open the receiver's
* window to allow more to be transmitted. This could result in
* two ACKs being sent for each received packet in some limited cases
* (where the application is only receiving data, and is slow to
* process it) but it is necessary to guarantee that the sender can
* continue to transmit.
*/
tcp_ack(pcb);
}
else if (pcb->flags & TF_ACK_DELAY && pcb->rcv_wnd >= TCP_WND/2) {
/* If we can send a window update such that there is a full
* segment available in the window, do so now. This is sort of
* nagle-like in its goals, and tries to hit a compromise between
* sending acks each time the window is updated, and only sending
* window updates when a timer expires. The "threshold" used
* above (currently TCP_WND/2) can be tuned to be more or less
* aggressive */
pcb->rcv_wnd += len;
if (pcb->rcv_wnd > TCP_WND)
pcb->rcv_wnd = TCP_WND;
wnd_inflation = tcp_update_rcv_ann_wnd(pcb);
/* If the change in the right edge of window is significant (default
* watermark is TCP_WND/2), then send an explicit update now.
* Otherwise wait for a packet to be sent in the normal course of
* events (or more window to be available later) */
if (wnd_inflation >= TCP_WND_UPDATE_THRESHOLD)
tcp_ack_now(pcb);
}
LWIP_DEBUGF(TCP_DEBUG, ("tcp_recved: recveived %"U16_F" bytes, wnd %"U16_F" (%"U16_F").\n",
len, pcb->rcv_wnd, TCP_WND - pcb->rcv_wnd));
@@ -510,6 +517,7 @@ tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
pcb->snd_lbb = iss - 1;
pcb->rcv_wnd = TCP_WND;
pcb->rcv_ann_wnd = TCP_WND;
pcb->rcv_ann_right_edge = pcb->rcv_nxt;
pcb->snd_wnd = TCP_WND;
/* As initial send MSS, we use TCP_MSS but limit it to 536.
The send MSS is updated when an MSS option is received. */