Implement slow start.

diff --git a/utcp.c b/utcp.c
index 9f668edd37256e214db12347722c48a79dd8f4cf..cf33e4c174b1a63d7b5291a961ea479be9aad03f 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -596,20 +596,38 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
        // 3. Advance snd.una
 
        uint32_t advanced = seqdiff(hdr.ack, c->snd.una);
-       c->snd.una = hdr.ack;
+       uint32_t prevrcvnxt = c->rcv.nxt;
 
        if(advanced) {
-               debug("%p advanced %u\n", utcp, advanced);
+               int32_t data_acked = advanced;
+
+               switch(c->state) {
+                       case SYN_SENT:
+                       case SYN_RECEIVED:
+                               data_acked--;
+                               break;
+                       // TODO: handle FIN as well.
+                       default:
+                               break;
+               }
+
+               assert(data_acked >= 0);
+
+               int32_t bufused = seqdiff(c->snd.last, c->snd.una);
+               assert(data_acked <= bufused);
+
                // Make room in the send buffer.
                // TODO: try to avoid memmoving too much. Circular buffer?
-               uint32_t left = seqdiff(c->snd.nxt, hdr.ack);
-               if(left)
-                       memmove(c->sndbuf, c->sndbuf + advanced, left);
+               uint32_t left = bufused - data_acked;
+               if(data_acked && left)
+                       memmove(c->sndbuf, c->sndbuf + data_acked, left);
+
+               c->snd.una = hdr.ack;
+
                c->dupack = 0;
                c->snd.cwnd += utcp->mtu;
                if(c->snd.cwnd > c->maxsndbufsize)
                        c->snd.cwnd = c->maxsndbufsize;
-               debug("%p increasing cwnd to %u\n", utcp, c->snd.cwnd);
 
                // Check if we have sent a FIN that is now ACKed.
                switch(c->state) {
@@ -775,14 +793,14 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                }
        }
 
-       if(!len && !advanced)
-               return 0;
-
-       if(!len && !(hdr.ctl & SYN) && !(hdr.ctl & FIN))
-               return 0;
+       // Now we send something back if:
+       // - we advanced rcv.nxt (ie, we got some data that needs to be ACKed)
+       //   -> sendatleastone = true
+       // - or we got an ack, so we should maybe send a bit more data
+       //   -> sendatleastone = false
 
 ack:
-       ack(c, true);
+       ack(c, prevrcvnxt != c->rcv.nxt);
        return 0;
 
 reset: