Start implementation of congestion avoidance.

[utcp] / utcp.c

diff --git a/utcp.c b/utcp.c
index 8ff9553de87f966a2d0e3d9b17b38ae7f79ec844..454a497428dd0e698db2bdeae92189fda41eb0fb 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -181,6 +181,8 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
        c->snd.una = c->snd.iss;
        c->snd.nxt = c->snd.iss + 1;
        c->rcv.wnd = utcp->mtu;
+       c->snd.last = c->snd.nxt;
+       c->snd.cwnd = utcp->mtu;
        c->utcp = utcp;
 
        // Add it to the sorted list of connections
@@ -230,6 +232,46 @@ void utcp_accept(struct utcp_connection *c, utcp_recv_t recv, void *priv) {
        set_state(c, ESTABLISHED);
 }
 
+static void ack(struct utcp_connection *c, bool sendatleastone) {
+       uint32_t left = seqdiff(c->snd.last, c->snd.nxt);
+       int32_t cwndleft = c->snd.cwnd - seqdiff(c->snd.nxt, c->snd.una);
+       char *data = c->sndbuf + seqdiff(c->snd.nxt, c->snd.una);
+
+       if(cwndleft <= 0)
+               cwndleft = 0;
+
+       if(cwndleft < left)
+               left = cwndleft;
+
+       if(!left && !sendatleastone)
+               return;
+
+       struct {
+               struct hdr hdr;
+               char data[c->utcp->mtu];
+       } pkt;
+
+       pkt.hdr.src = c->src;
+       pkt.hdr.dst = c->dst;
+       pkt.hdr.ack = c->rcv.nxt;
+       pkt.hdr.wnd = c->snd.wnd;
+       pkt.hdr.ctl = ACK;
+
+       do {
+               uint32_t seglen = left > c->utcp->mtu ? c->utcp->mtu : left;
+               pkt.hdr.seq = c->snd.nxt;
+
+               memcpy(pkt.data, data, seglen);
+
+               c->snd.nxt += seglen;
+               data += seglen;
+               left -= seglen;
+
+               print_packet(c->utcp, "send", &pkt, sizeof pkt.hdr + seglen);
+               c->utcp->send(c->utcp, &pkt, sizeof pkt.hdr + seglen);
+       } while(left);
+}
+
 ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
        if(c->reapable) {
                debug("Error: send() called on closed connection %p\n", c);
@@ -277,11 +319,16 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
         */
 
        if(len > c->sndbufsize - bufused && c->sndbufsize < c->maxsndbufsize) {
+               uint32_t newbufsize;
                if(c->sndbufsize > c->maxsndbufsize / 2)
-                       c->sndbufsize = c->maxsndbufsize;
+                       newbufsize = c->maxsndbufsize;
                else
-                       c->sndbufsize *= 2;
-               c->sndbuf = realloc(c->sndbuf, c->sndbufsize);
+                       newbufsize = c->sndbufsize * 2;
+               char *newbuf = realloc(c->sndbuf, newbufsize);
+               if(newbuf) {
+                       c->sndbuf = newbuf;
+                       c->sndbufsize = newbufsize;
+               }
        }
 
        if(len > c->sndbufsize - bufused)
@@ -293,37 +340,9 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
        }
 
        memcpy(c->sndbuf + bufused, data, len);
+       c->snd.last += len;
 
-       // Send segments
-
-       struct {
-               struct hdr hdr;
-               char data[c->utcp->mtu];
-       } pkt;
-
-       pkt.hdr.src = c->src;
-       pkt.hdr.dst = c->dst;
-       pkt.hdr.ack = c->rcv.nxt;
-       pkt.hdr.wnd = c->snd.wnd;
-       pkt.hdr.ctl = ACK;
-
-       uint32_t left = len;
-
-       while(left) {
-               uint32_t seglen = left > c->utcp->mtu ? c->utcp->mtu : left;
-               pkt.hdr.seq = c->snd.nxt;
-
-               memcpy(pkt.data, data, seglen);
-
-               c->snd.nxt += seglen;
-               data += seglen;
-               left -= seglen;
-
-               print_packet(c->utcp, "send", &pkt, sizeof pkt.hdr + seglen);
-               c->utcp->send(c->utcp, &pkt, sizeof pkt.hdr + seglen);
-       }
-
-       fprintf(stderr, "len=%zu\n", len);
+       ack(c, false);
        return len;
 }
 
@@ -561,6 +580,18 @@ int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                uint32_t left = seqdiff(c->snd.nxt, hdr.ack);
                if(left)
                        memmove(c->sndbuf, c->sndbuf + advanced, left);
+               c->dupack = 0;
+               c->snd.cwnd += utcp->mtu;
+               if(c->snd.cwnd > c->maxsndbufsize)
+                       c->snd.cwnd = c->maxsndbufsize;
+       } else {
+               if(!len) {
+                       c->dupack++;
+                       if(c->dupack >= 3) {
+                               debug("Triplicate ACK\n");
+                               abort();
+                       }
+               }
        }
 
        // 4. Update timers
@@ -699,13 +730,7 @@ int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                return 0;
 
 ack:
-       hdr.src = c->src;
-       hdr.dst = c->dst;
-       hdr.seq = c->snd.nxt;
-       hdr.ack = c->rcv.nxt;
-       hdr.ctl = ACK;
-       print_packet(c->utcp, "send", &hdr, sizeof hdr);
-       utcp->send(utcp, &hdr, sizeof hdr);
+       ack(c, true);
        return 0;
 
 reset: