Implement slow start.

[utcp] / utcp.c

diff --git a/utcp.c b/utcp.c
index 1fae32cd2eaf44430f93311a0787034c58e2861d..cf33e4c174b1a63d7b5291a961ea479be9aad03f 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -19,6 +19,7 @@
 
 #define _GNU_SOURCE
 
+#include <assert.h>
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -49,7 +50,7 @@ static void print_packet(struct utcp *utcp, const char *dir, const void *pkt, si
        }
 
        memcpy(&hdr, pkt, sizeof hdr);
-       fprintf (stderr, "%p %s: src=%u dst=%u seq=%u ack=%u wnd=%u ctl=", utcp, dir, hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd);
+       fprintf (stderr, "%p %s: len=%zu, src=%u dst=%u seq=%u ack=%u wnd=%u ctl=", utcp, dir, len, hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd);
        if(hdr.ctl & SYN)
                debug("SYN");
        if(hdr.ctl & RST)
@@ -97,8 +98,9 @@ static int32_t seqdiff(uint32_t a, uint32_t b) {
 static int compare(const void *va, const void *vb) {
        const struct utcp_connection *a = *(struct utcp_connection **)va;
        const struct utcp_connection *b = *(struct utcp_connection **)vb;
-       if(!a->src || !b->src)
-               abort();
+
+       assert(a->src && b->src);
+
        int c = (int)a->src - (int)b->src;
        if(c)
                return c;
@@ -120,8 +122,8 @@ static struct utcp_connection *find_connection(const struct utcp *utcp, uint16_t
 static void free_connection(struct utcp_connection *c) {
        struct utcp *utcp = c->utcp;
        struct utcp_connection **cp = bsearch(&c, utcp->connections, utcp->nconnections, sizeof *utcp->connections, compare);
-       if(!cp)
-               abort();
+
+       assert(cp);
 
        int i = cp - utcp->connections;
        memmove(cp + i, cp + i + 1, (utcp->nconnections - i - 1) * sizeof *cp);
@@ -239,9 +241,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
        int32_t cwndleft = c->snd.cwnd - seqdiff(c->snd.nxt, c->snd.una);
        char *data = c->sndbuf + seqdiff(c->snd.nxt, c->snd.una);
 
-       fprintf(stderr, "ack, left=%d, cwndleft=%d, sendatleastone=%d\n", left, cwndleft, sendatleastone);
-       if(left < 0)
-               abort();
+       assert(left >= 0);
 
        if(cwndleft <= 0)
                cwndleft = 0;
@@ -377,7 +377,7 @@ static void swap_ports(struct hdr *hdr) {
        hdr->dst = tmp;
 }
 
-int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
+ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
        if(!utcp) {
                errno = EFAULT;
                return -1;
@@ -596,20 +596,38 @@ int 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) {
@@ -632,7 +650,8 @@ int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                        c->dupack++;
                        if(c->dupack >= 3) {
                                debug("Triplicate ACK\n");
-                               abort();
+                               //TODO: Resend one packet and go to fast recovery mode. See RFC 6582.
+                               //abort();
                        }
                }
        }
@@ -640,7 +659,7 @@ int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
        // 4. Update timers
 
        if(advanced) {
-               timerclear(&c->conn_timeout); // It should be set anew in utcp_timeout() if c->snd.una != c->snd.nxt.
+               timerclear(&c->conn_timeout); // It will be set anew in utcp_timeout() if c->snd.una != c->snd.nxt.
                if(c->snd.una == c->snd.nxt)
                        timerclear(&c->rtrx_timeout);
        }
@@ -714,10 +733,15 @@ int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                        abort();
                }
 
-               int rxd;
+               ssize_t rxd;
 
                if(c->recv) {
                        rxd = c->recv(c, data, len);
+                       if(rxd != len) {
+                               // TODO: once we have a receive buffer, handle the application not accepting all data.
+                               fprintf(stderr, "c->recv(%p, %p, %zu) returned %zd\n", c, data, len, rxd);
+                               abort();
+                       }
                        if(rxd < 0)
                                rxd = 0;
                        else if(rxd > len)
@@ -769,14 +793,14 @@ int 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:
@@ -797,7 +821,7 @@ reset:
 }
 
 int utcp_shutdown(struct utcp_connection *c, int dir) {
-       debug("%p shutdown %d\n", c->utcp, dir);
+       debug("%p shutdown %d\n", c ? c->utcp : NULL, dir);
        if(!c) {
                errno = EFAULT;
                return -1;