Several fixes for handling UDP-like channels.

- Drop data sent before the connection is established.
- Relax checks on incoming ACK seqnos
- Always consider all data ACKed
- Disregard hdr.seq when a FIN packet is received
- Don't ACK pure data packets

diff --git a/utcp.c b/utcp.c
index 5dc7501a20d805e0d57520196bae31ec41657e78..7e28f9e27e3aef2a7f0937597eabbd5bd3c36f7a 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -627,11 +627,17 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
 
        // Add data to send buffer.
 
-       len = buffer_put(&c->sndbuf, data, len);
+       if(is_reliable(c) || (c->state != SYN_SENT && c->state != SYN_RECEIVED)) {
+               len = buffer_put(&c->sndbuf, data, len);
+       }
 
        if(len <= 0) {
-               errno = EWOULDBLOCK;
-               return 0;
+               if(is_reliable(c)) {
+                       errno = EWOULDBLOCK;
+                       return 0;
+               } else {
+                       return len;
+               }
        }
 
        c->snd.last += len;
@@ -1126,39 +1132,41 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
        // 1b. Drop packets with a sequence number not in our receive window.
 
-       bool acceptable;
+       if(is_reliable(c)) {
+               bool acceptable;
 
-       if(c->state == SYN_SENT) {
-               acceptable = true;
-       } else if(len == 0) {
-               acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0;
-       } else {
-               int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
+               if(c->state == SYN_SENT) {
+                       acceptable = true;
+               } else if(len == 0) {
+                       acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0;
+               } else {
+                       int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
 
-               // cut already accepted front overlapping
-               if(rcv_offset < 0) {
-                       acceptable = len > (size_t) - rcv_offset;
+                       // cut already accepted front overlapping
+                       if(rcv_offset < 0) {
+                               acceptable = len > (size_t) - rcv_offset;
 
-                       if(acceptable) {
-                               ptr -= rcv_offset;
-                               len += rcv_offset;
-                               hdr.seq -= rcv_offset;
+                               if(acceptable) {
+                                       ptr -= rcv_offset;
+                                       len += rcv_offset;
+                                       hdr.seq -= rcv_offset;
+                               }
+                       } else {
+                               acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt) + len <= c->rcvbuf.maxsize;
                        }
-               } else {
-                       acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt) + len <= c->rcvbuf.maxsize;
                }
-       }
 
-       if(!acceptable) {
-               debug("Packet not acceptable, %u <= %u + %lu < %u\n", c->rcv.nxt, hdr.seq, (unsigned long)len, c->rcv.nxt + c->rcvbuf.maxsize);
+               if(!acceptable) {
+                       debug("Packet not acceptable, %u <= %u + %lu < %u\n", c->rcv.nxt, hdr.seq, (unsigned long)len, c->rcv.nxt + c->rcvbuf.maxsize);
 
-               // Ignore unacceptable RST packets.
-               if(hdr.ctl & RST) {
-                       return 0;
-               }
+                       // Ignore unacceptable RST packets.
+                       if(hdr.ctl & RST) {
+                               return 0;
+                       }
 
-               // Otherwise, continue processing.
-               len = 0;
+                       // Otherwise, continue processing.
+                       len = 0;
+               }
        }
 
        c->snd.wnd = hdr.wnd; // TODO: move below
@@ -1167,6 +1175,12 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
        // ackno should not roll back, and it should also not be bigger than what we ever could have sent
        // (= snd.una + c->sndbuf.used).
 
+       if(!is_reliable(c)) {
+               if(hdr.ack != c->snd.last && c->state >= ESTABLISHED) {
+                       hdr.ack = c->snd.una;
+               }
+       }
+
        if(hdr.ctl & ACK && (seqdiff(hdr.ack, c->snd.last) > 0 || seqdiff(hdr.ack, c->snd.una) < 0)) {
                debug("Packet ack seqno out of range, %u <= %u < %u\n", c->snd.una, hdr.ack, c->snd.una + c->sndbuf.used);
 
@@ -1472,7 +1486,7 @@ skip_ack:
 
        // 7. Process FIN stuff
 
-       if((hdr.ctl & FIN) && hdr.seq + len == c->rcv.nxt) {
+       if((hdr.ctl & FIN) && (!is_reliable(c) || hdr.seq + len == c->rcv.nxt)) {
                switch(c->state) {
                case SYN_SENT:
                case SYN_RECEIVED:
@@ -1527,7 +1541,10 @@ skip_ack:
        // - or we got an ack, so we should maybe send a bit more data
        //   -> sendatleastone = false
 
-       ack(c, len || prevrcvnxt != c->rcv.nxt);
+       if(is_reliable(c) || hdr.ctl & SYN || hdr.ctl & FIN) {
+               ack(c, len || prevrcvnxt != c->rcv.nxt);
+       }
+
        return 0;
 
 reset: