]> git.meshlink.io Git - utcp/blobdiff - utcp.c
Implement ringbuffers.
[utcp] / utcp.c
diff --git a/utcp.c b/utcp.c
index b939dc8a0e5e4f6723ea2eaa6f1b610adc1ecfee..f94c6e7e1be55ddef85b20efaff91ba143d9a620 100644 (file)
--- a/utcp.c
+++ b/utcp.c
@@ -153,12 +153,40 @@ static int32_t seqdiff(uint32_t a, uint32_t b) {
 }
 
 // Buffer functions
-// TODO: convert to ringbuffers to avoid memmove() operations.
+static bool buffer_wraps(struct buffer *buf) {
+       return buf->size - buf->offset < buf->used;
+}
+
+static bool buffer_resize(struct buffer *buf, uint32_t newsize) {
+       char *newdata = realloc(buf->data, newsize);
+
+       if(!newdata) {
+               return false;
+       }
+
+       buf->data = newdata;
+
+       if(buffer_wraps(buf)) {
+               // Shift the right part of the buffer until it hits the end of the new buffer.
+               // Old situation:
+               // [345......012]
+               // New situation:
+               // [345.........|........012]
+               uint32_t tailsize = buf->size - buf->offset;
+               uint32_t newoffset = newsize - tailsize;
+               memmove(buf + newoffset, buf + buf->offset, tailsize);
+               buf->offset = newoffset;
+       }
+
+       buf->size = newsize;
+       return true;
+}
 
 // Store data into the buffer
 static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data, size_t len) {
        debug("buffer_put_at %lu %lu %lu\n", (unsigned long)buf->used, (unsigned long)offset, (unsigned long)len);
 
+       // Ensure we don't store more than maxsize bytes in total
        size_t required = offset + len;
 
        if(required > buf->maxsize) {
@@ -170,32 +198,41 @@ static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data
                required = buf->maxsize;
        }
 
+       // Check if we need to resize the buffer
        if(required > buf->size) {
                size_t newsize = buf->size;
 
                if(!newsize) {
-                       newsize = required;
-               } else {
-                       do {
-                               newsize *= 2;
-                       } while(newsize < required);
+                       newsize = 4096;
                }
 
+               do {
+                       newsize *= 2;
+               } while(newsize < required);
+
                if(newsize > buf->maxsize) {
                        newsize = buf->maxsize;
                }
 
-               char *newdata = realloc(buf->data, newsize);
-
-               if(!newdata) {
+               if(!buffer_resize(buf, newsize)) {
                        return -1;
                }
+       }
 
-               buf->data = newdata;
-               buf->size = newsize;
+       uint32_t realoffset = buf->offset + offset;
+
+       if(buf->size - buf->offset < offset) {
+               // The offset wrapped
+               realoffset -= buf->size;
        }
 
-       memcpy(buf->data + offset, data, len);
+       if(buf->size - realoffset < len) {
+               // The new chunk of data must be wrapped
+               memcpy(buf->data + realoffset, data, buf->size - realoffset);
+               memcpy(buf->data, (char *)data + buf->size - realoffset, len - (buf->size - realoffset));
+       } else {
+               memcpy(buf->data + realoffset, data, len);
+       }
 
        if(required > buf->used) {
                buf->used = required;
@@ -208,52 +245,72 @@ static ssize_t buffer_put(struct buffer *buf, const void *data, size_t len) {
        return buffer_put_at(buf, buf->used, data, len);
 }
 
-// Get data from the buffer. data can be NULL.
-static ssize_t buffer_get(struct buffer *buf, void *data, size_t len) {
-       if(len > buf->used) {
-               len = buf->used;
+// Copy data from the buffer without removing it.
+static ssize_t buffer_copy(struct buffer *buf, void *data, size_t offset, size_t len) {
+       // Ensure we don't copy more than is actually stored in the buffer
+       if(offset >= buf->used) {
+               return 0;
        }
 
-       if(data) {
-               memcpy(data, buf->data, len);
+       if(buf->used - offset < len) {
+               len = buf->used - offset;
        }
 
-       if(len < buf->used) {
-               memmove(buf->data, buf->data + len, buf->used - len);
+       uint32_t realoffset = buf->offset + offset;
+
+       if(buf->size - buf->offset < offset) {
+               // The offset wrapped
+               realoffset -= buf->size;
+       }
+
+       if(buf->size - realoffset < len) {
+               // The data is wrapped
+               memcpy(data, buf->data + realoffset, buf->size - realoffset);
+               memcpy((char *)data + buf->size - realoffset, buf->data, len - (buf->size - realoffset));
+       } else {
+               memcpy(data, buf->data + realoffset, len);
        }
 
-       buf->used -= len;
        return len;
 }
 
-// Copy data from the buffer without removing it.
-static ssize_t buffer_copy(struct buffer *buf, void *data, size_t offset, size_t len) {
-       if(offset >= buf->used) {
-               return 0;
-       }
+// Get data from the buffer.
+static ssize_t buffer_get(struct buffer *buf, void *data, size_t len) {
+       len = buffer_copy(buf, data, 0, len);
 
-       if(offset + len > buf->used) {
-               len = buf->used - offset;
+       if(buf->size - buf->offset < len) {
+               buf->offset -= buf->size;
        }
 
-       memcpy(data, buf->data + offset, len);
+       buf->offset += len;
+       buf->used -= len;
        return len;
 }
 
-static bool buffer_init(struct buffer *buf, uint32_t len, uint32_t maxlen) {
-       memset(buf, 0, sizeof(*buf));
+// Discard data from the buffer.
+static ssize_t buffer_discard(struct buffer *buf, size_t len) {
+       if(buf->used < len) {
+               len = buf->used;
+       }
 
-       if(len) {
-               buf->data = malloc(len);
+       if(buf->size - buf->offset < len) {
+               buf->offset -= buf->size;
+       }
 
-               if(!buf->data) {
-                       return false;
-               }
+       buf->offset += len;
+       buf->used -= len;
+
+       return len;
+}
+
+static bool buffer_set_size(struct buffer *buf, uint32_t minsize, uint32_t maxsize) {
+       if(maxsize < minsize) {
+               maxsize = minsize;
        }
 
-       buf->size = len;
-       buf->maxsize = maxlen;
-       return true;
+       buf->maxsize = maxsize;
+
+       return buf->size >= minsize || buffer_resize(buf, minsize);
 }
 
 static void buffer_exit(struct buffer *buf) {
@@ -360,12 +417,12 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
                return NULL;
        }
 
-       if(!buffer_init(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
+       if(!buffer_set_size(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
                free(c);
                return NULL;
        }
 
-       if(!buffer_init(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
+       if(!buffer_set_size(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
                buffer_exit(&c->sndbuf);
                free(c);
                return NULL;
@@ -415,13 +472,13 @@ static void update_rtt(struct utcp_connection *c, uint32_t rtt) {
        if(!utcp->srtt) {
                utcp->srtt = rtt;
                utcp->rttvar = rtt / 2;
-               utcp->rto = rtt + max(2 * rtt, CLOCK_GRANULARITY);
        } else {
                utcp->rttvar = (utcp->rttvar * 3 + absdiff(utcp->srtt, rtt)) / 4;
                utcp->srtt = (utcp->srtt * 7 + rtt) / 8;
-               utcp->rto = utcp->srtt + max(utcp->rttvar, CLOCK_GRANULARITY);
        }
 
+       utcp->rto = utcp->srtt + max(4 * utcp->rttvar, CLOCK_GRANULARITY);
+
        if(utcp->rto > MAX_RTO) {
                utcp->rto = MAX_RTO;
        }
@@ -453,7 +510,7 @@ struct utcp_connection *utcp_connect_ex(struct utcp *utcp, uint16_t dst, utcp_re
                return NULL;
        }
 
-       assert((flags & ~0xf) == 0);
+       assert((flags & ~0x1f) == 0);
 
        c->flags = flags;
        c->recv = recv;
@@ -527,13 +584,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
        struct {
                struct hdr hdr;
                uint8_t data[];
-       } *pkt;
-
-       pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-       if(!pkt) {
-               return;
-       }
+       } *pkt = c->utcp->pkt;
 
        pkt->hdr.src = c->src;
        pkt->hdr.dst = c->dst;
@@ -566,8 +617,6 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
                print_packet(c->utcp, "send", pkt, sizeof(pkt->hdr) + seglen);
                c->utcp->send(c->utcp, pkt, sizeof(pkt->hdr) + seglen);
        } while(left);
-
-       free(pkt);
 }
 
 ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
@@ -580,12 +629,12 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
        switch(c->state) {
        case CLOSED:
        case LISTEN:
-       case SYN_SENT:
-       case SYN_RECEIVED:
                debug("Error: send() called on unconnected connection %p\n", c);
                errno = ENOTCONN;
                return -1;
 
+       case SYN_SENT:
+       case SYN_RECEIVED:
        case ESTABLISHED:
        case CLOSE_WAIT:
                break;
@@ -611,16 +660,45 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
                return -1;
        }
 
+       // Check if we need to be able to buffer all data
+
+       if(c->flags & UTCP_NO_PARTIAL) {
+               if(len > buffer_free(&c->sndbuf)) {
+                       if(len > c->sndbuf.maxsize) {
+                               errno = EMSGSIZE;
+                               return -1;
+                       } else {
+                               errno = EWOULDBLOCK;
+                               return 0;
+                       }
+               }
+       }
+
        // 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);
+       } else {
+               return 0;
+       }
 
        if(len <= 0) {
-               errno = EWOULDBLOCK;
-               return 0;
+               if(is_reliable(c)) {
+                       errno = EWOULDBLOCK;
+                       return 0;
+               } else {
+                       return len;
+               }
        }
 
        c->snd.last += len;
+
+       // Don't send anything yet if the connection has not fully established yet
+
+       if(c->state == SYN_SENT || c->state == SYN_RECEIVED) {
+               return len;
+       }
+
        ack(c, false);
 
        if(!is_reliable(c)) {
@@ -632,6 +710,11 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
                start_retransmit_timer(c);
        }
 
+       if(is_reliable(c) && !timerisset(&c->conn_timeout)) {
+               gettimeofday(&c->conn_timeout, NULL);
+               c->conn_timeout.tv_sec += c->utcp->timeout;
+       }
+
        return len;
 }
 
@@ -653,13 +736,7 @@ static void retransmit(struct utcp_connection *c) {
        struct {
                struct hdr hdr;
                uint8_t data[];
-       } *pkt;
-
-       pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-       if(!pkt) {
-               return;
-       }
+       } *pkt = c->utcp->pkt;
 
        pkt->hdr.src = c->src;
        pkt->hdr.dst = c->dst;
@@ -739,7 +816,7 @@ static void retransmit(struct utcp_connection *c) {
        c->rtt_start.tv_sec = 0; // invalidate RTT timer
 
 cleanup:
-       free(pkt);
+       return;
 }
 
 /* Update receive buffer and SACK entries after consuming data.
@@ -892,6 +969,8 @@ static void handle_incoming_data(struct utcp_connection *c, uint32_t seq, const
 
 
 ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
+       const uint8_t *ptr = data;
+
        if(!utcp) {
                errno = EFAULT;
                return -1;
@@ -919,8 +998,8 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
        // Make a copy from the potentially unaligned data to a struct hdr
 
-       memcpy(&hdr, data, sizeof(hdr));
-       data += sizeof(hdr);
+       memcpy(&hdr, ptr, sizeof(hdr));
+       ptr += sizeof(hdr);
        len -= sizeof(hdr);
 
        // Drop packets with an unknown CTL flag
@@ -952,7 +1031,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                                return -1;
                        }
 
-                       init = data;
+                       init = ptr;
                        break;
 
                default:
@@ -961,7 +1040,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                }
 
                len -= auxlen;
-               data += auxlen;
+               ptr += auxlen;
 
                if(!(aux & 0x800)) {
                        break;
@@ -972,11 +1051,13 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                        return -1;
                }
 
-               memcpy(&aux, data, 2);
+               memcpy(&aux, ptr, 2);
                len -= 2;
-               data += 2;
+               ptr += 2;
        }
 
+       bool has_data = len || (hdr.ctl & (SYN | FIN));
+
        // Try to match the packet to an existing connection
 
        struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
@@ -1019,6 +1100,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                                c->flags = UTCP_TCP;
                        }
 
+synack:
                        // Return SYN+ACK, go to SYN_RECEIVED state
                        c->snd.wnd = hdr.wnd;
                        c->rcv.irs = hdr.seq;
@@ -1071,8 +1153,6 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
        // It is for an existing connection.
 
-       uint32_t prevrcvnxt = c->rcv.nxt;
-
        // 1. Drop invalid packets.
 
        // 1a. Drop packets that should not happen in our current state.
@@ -1096,41 +1176,43 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                break;
        }
 
-       // 1b. Drop packets with a sequence number not in our receive window.
+       // 1b. Discard data that is 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) {
-                               data -= 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
@@ -1139,6 +1221,12 @@ 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);
 
@@ -1167,6 +1255,10 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                                c->recv(c, NULL, 0);
                        }
 
+                       if(c->poll && !c->reapable) {
+                               c->poll(c, 0);
+                       }
+
                        return 0;
 
                case SYN_RECEIVED:
@@ -1194,6 +1286,10 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                                c->recv(c, NULL, 0);
                        }
 
+                       if(c->poll && !c->reapable) {
+                               c->poll(c, 0);
+                       }
+
                        return 0;
 
                case CLOSING:
@@ -1222,14 +1318,16 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                }
        }
 
+       uint32_t advanced;
+
        if(!(hdr.ctl & ACK)) {
+               advanced = 0;
                goto skip_ack;
        }
 
        // 3. Advance snd.una
 
-       uint32_t advanced = seqdiff(hdr.ack, c->snd.una);
-       prevrcvnxt = c->rcv.nxt;
+       advanced = seqdiff(hdr.ack, c->snd.una);
 
        if(advanced) {
                // RTT measurement
@@ -1261,11 +1359,13 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
                assert(data_acked >= 0);
 
+#ifndef NDEBUG
                int32_t bufused = seqdiff(c->snd.last, c->snd.una);
                assert(data_acked <= bufused);
+#endif
 
                if(data_acked) {
-                       buffer_get(&c->sndbuf, NULL, data_acked);
+                       buffer_discard(&c->sndbuf, data_acked);
                }
 
                // Also advance snd.nxt if possible
@@ -1294,7 +1394,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
                case CLOSING:
                        if(c->snd.una == c->snd.last) {
                                gettimeofday(&c->conn_timeout, NULL);
-                               c->conn_timeout.tv_sec += 60;
+                               c->conn_timeout.tv_sec += utcp->timeout;
                                set_state(c, TIME_WAIT);
                        }
 
@@ -1322,12 +1422,13 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
        // 4. Update timers
 
        if(advanced) {
-               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.last) {
                        stop_retransmit_timer(c);
+                       timerclear(&c->conn_timeout);
                } else if(is_reliable(c)) {
                        start_retransmit_timer(c);
+                       gettimeofday(&c->conn_timeout, NULL);
+                       c->conn_timeout.tv_sec += utcp->timeout;
                }
        }
 
@@ -1345,11 +1446,21 @@ skip_ack:
 
                        c->rcv.irs = hdr.seq;
                        c->rcv.nxt = hdr.seq;
-                       set_state(c, ESTABLISHED);
+
+                       if(c->shut_wr) {
+                               c->snd.last++;
+                               set_state(c, FIN_WAIT_1);
+                       } else {
+                               set_state(c, ESTABLISHED);
+                       }
+
                        // TODO: notify application of this somehow.
                        break;
 
                case SYN_RECEIVED:
+                       // This is a retransmit of a SYN, send back the SYNACK.
+                       goto synack;
+
                case ESTABLISHED:
                case FIN_WAIT_1:
                case FIN_WAIT_2:
@@ -1420,12 +1531,12 @@ skip_ack:
                        return 0;
                }
 
-               handle_incoming_data(c, hdr.seq, data, len);
+               handle_incoming_data(c, hdr.seq, ptr, len);
        }
 
        // 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:
@@ -1445,7 +1556,7 @@ skip_ack:
 
                case FIN_WAIT_2:
                        gettimeofday(&c->conn_timeout, NULL);
-                       c->conn_timeout.tv_sec += 60;
+                       c->conn_timeout.tv_sec += utcp->timeout;
                        set_state(c, TIME_WAIT);
                        break;
 
@@ -1467,7 +1578,7 @@ skip_ack:
                c->rcv.nxt++;
                len++;
 
-               // Inform the application that the peer closed the connection.
+               // Inform the application that the peer closed its end of the connection.
                if(c->recv) {
                        errno = 0;
                        c->recv(c, NULL, 0);
@@ -1475,12 +1586,15 @@ skip_ack:
        }
 
        // Now we send something back if:
-       // - we advanced rcv.nxt (ie, we got some data that needs to be ACKed)
+       // - we received data, so we have to send back an ACK
        //   -> sendatleastone = true
        // - 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, has_data);
+       }
+
        return 0;
 
 reset:
@@ -1533,6 +1647,13 @@ int utcp_shutdown(struct utcp_connection *c, int dir) {
                return 0;
        }
 
+       // Only process shutting down writes once.
+       if(c->shut_wr) {
+               return 0;
+       }
+
+       c->shut_wr = true;
+
        switch(c->state) {
        case CLOSED:
        case LISTEN:
@@ -1540,7 +1661,6 @@ int utcp_shutdown(struct utcp_connection *c, int dir) {
                return -1;
 
        case SYN_SENT:
-               set_state(c, CLOSED);
                return 0;
 
        case SYN_RECEIVED:
@@ -1573,36 +1693,24 @@ int utcp_shutdown(struct utcp_connection *c, int dir) {
        return 0;
 }
 
-int utcp_close(struct utcp_connection *c) {
-       if(utcp_shutdown(c, SHUT_RDWR) && errno != ENOTCONN) {
-               return -1;
-       }
-
-       c->recv = NULL;
-       c->poll = NULL;
-       c->reapable = true;
-       return 0;
-}
-
-int utcp_abort(struct utcp_connection *c) {
+static bool reset_connection(struct utcp_connection *c) {
        if(!c) {
                errno = EFAULT;
-               return -1;
+               return false;
        }
 
        if(c->reapable) {
                debug("Error: abort() called on closed connection %p\n", c);
                errno = EBADF;
-               return -1;
+               return false;
        }
 
        c->recv = NULL;
        c->poll = NULL;
-       c->reapable = true;
 
        switch(c->state) {
        case CLOSED:
-               return 0;
+               return true;
 
        case LISTEN:
        case SYN_SENT:
@@ -1610,7 +1718,7 @@ int utcp_abort(struct utcp_connection *c) {
        case LAST_ACK:
        case TIME_WAIT:
                set_state(c, CLOSED);
-               return 0;
+               return true;
 
        case SYN_RECEIVED:
        case ESTABLISHED:
@@ -1634,6 +1742,59 @@ int utcp_abort(struct utcp_connection *c) {
 
        print_packet(c->utcp, "send", &hdr, sizeof(hdr));
        c->utcp->send(c->utcp, &hdr, sizeof(hdr));
+       return true;
+}
+
+// Closes all the opened connections
+void utcp_abort_all_connections(struct utcp *utcp) {
+       if(!utcp) {
+               errno = EINVAL;
+               return;
+       }
+
+       for(int i = 0; i < utcp->nconnections; i++) {
+               struct utcp_connection *c = utcp->connections[i];
+
+               if(c->reapable || c->state == CLOSED) {
+                       continue;
+               }
+
+               utcp_recv_t old_recv = c->recv;
+               utcp_poll_t old_poll = c->poll;
+
+               reset_connection(c);
+
+               if(old_recv) {
+                       errno = 0;
+                       old_recv(c, NULL, 0);
+               }
+
+               if(old_poll && !c->reapable) {
+                       errno = 0;
+                       old_poll(c, 0);
+               }
+       }
+
+       return;
+}
+
+int utcp_close(struct utcp_connection *c) {
+       if(utcp_shutdown(c, SHUT_RDWR) && errno != ENOTCONN) {
+               return -1;
+       }
+
+       c->recv = NULL;
+       c->poll = NULL;
+       c->reapable = true;
+       return 0;
+}
+
+int utcp_abort(struct utcp_connection *c) {
+       if(!reset_connection(c)) {
+               return -1;
+       }
+
+       c->reapable = true;
        return 0;
 }
 
@@ -1674,6 +1835,10 @@ struct timeval utcp_timeout(struct utcp *utcp) {
                                c->recv(c, NULL, 0);
                        }
 
+                       if(c->poll && !c->reapable) {
+                               c->poll(c, 0);
+                       }
+
                        continue;
                }
 
@@ -1739,7 +1904,7 @@ struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_
        utcp->pre_accept = pre_accept;
        utcp->send = send;
        utcp->priv = priv;
-       utcp->mtu = DEFAULT_MTU;
+       utcp_set_mtu(utcp, DEFAULT_MTU);
        utcp->timeout = DEFAULT_USER_TIMEOUT; // sec
        utcp->rto = START_RTO; // usec
 
@@ -1754,11 +1919,16 @@ void utcp_exit(struct utcp *utcp) {
        for(int i = 0; i < utcp->nconnections; i++) {
                struct utcp_connection *c = utcp->connections[i];
 
-               if(!c->reapable)
+               if(!c->reapable) {
                        if(c->recv) {
                                c->recv(c, NULL, 0);
                        }
 
+                       if(c->poll && !c->reapable) {
+                               c->poll(c, 0);
+                       }
+               }
+
                buffer_exit(&c->rcvbuf);
                buffer_exit(&c->sndbuf);
                free(c);
@@ -1773,10 +1943,25 @@ uint16_t utcp_get_mtu(struct utcp *utcp) {
 }
 
 void utcp_set_mtu(struct utcp *utcp, uint16_t mtu) {
-       // TODO: handle overhead of the header
-       if(utcp) {
-               utcp->mtu = mtu;
+       if(!utcp) {
+               return;
+       }
+
+       if(mtu <= sizeof(struct hdr)) {
+               return;
        }
+
+       if(mtu > utcp->mtu) {
+               char *new = realloc(utcp->pkt, mtu + sizeof(struct hdr));
+
+               if(!new) {
+                       return;
+               }
+
+               utcp->pkt = new;
+       }
+
+       utcp->mtu = mtu;
 }
 
 void utcp_reset_timers(struct utcp *utcp) {
@@ -1793,9 +1978,21 @@ void utcp_reset_timers(struct utcp *utcp) {
        then.tv_sec += utcp->timeout;
 
        for(int i = 0; i < utcp->nconnections; i++) {
-               utcp->connections[i]->rtrx_timeout = now;
-               utcp->connections[i]->conn_timeout = then;
-               utcp->connections[i]->rtt_start.tv_sec = 0;
+               struct utcp_connection *c = utcp->connections[i];
+
+               if(c->reapable) {
+                       continue;
+               }
+
+               if(timerisset(&c->rtrx_timeout)) {
+                       c->rtrx_timeout = now;
+               }
+
+               if(timerisset(&c->conn_timeout)) {
+                       c->conn_timeout = then;
+               }
+
+               c->rtt_start.tv_sec = 0;
        }
 
        if(utcp->rto > START_RTO) {
@@ -1818,9 +2015,18 @@ size_t utcp_get_sndbuf(struct utcp_connection *c) {
 }
 
 size_t utcp_get_sndbuf_free(struct utcp_connection *c) {
-       if(c && (c->state == ESTABLISHED || c->state == CLOSE_WAIT)) {
+       if(!c) {
+               return 0;
+       }
+
+       switch(c->state) {
+       case SYN_SENT:
+       case SYN_RECEIVED:
+       case ESTABLISHED:
+       case CLOSE_WAIT:
                return buffer_free(&c->sndbuf);
-       } else {
+
+       default:
                return 0;
        }
 }
@@ -1861,6 +2067,14 @@ void utcp_set_rcvbuf(struct utcp_connection *c, size_t size) {
        }
 }
 
+size_t utcp_get_sendq(struct utcp_connection *c) {
+       return c->sndbuf.used;
+}
+
+size_t utcp_get_recvq(struct utcp_connection *c) {
+       return c->rcvbuf.used;
+}
+
 bool utcp_get_nodelay(struct utcp_connection *c) {
        return c ? c->nodelay : false;
 }
@@ -1903,3 +2117,53 @@ void utcp_set_accept_cb(struct utcp *utcp, utcp_accept_t accept, utcp_pre_accept
                utcp->pre_accept = pre_accept;
        }
 }
+
+void utcp_expect_data(struct utcp_connection *c, bool expect) {
+       if(!c || c->reapable) {
+               return;
+       }
+
+       if(!(c->state == ESTABLISHED || c->state == FIN_WAIT_1 || c->state == FIN_WAIT_2)) {
+               return;
+       }
+
+       if(expect) {
+               // If we expect data, start the connection timer.
+               if(!timerisset(&c->conn_timeout)) {
+                       gettimeofday(&c->conn_timeout, NULL);
+                       c->conn_timeout.tv_sec += c->utcp->timeout;
+               }
+       } else {
+               // If we want to cancel expecting data, only clear the timer when there is no unACKed data.
+               if(c->snd.una == c->snd.last) {
+                       timerclear(&c->conn_timeout);
+               }
+       }
+}
+
+void utcp_offline(struct utcp *utcp, bool offline) {
+       struct timeval now;
+       gettimeofday(&now, NULL);
+
+       for(int i = 0; i < utcp->nconnections; i++) {
+               struct utcp_connection *c = utcp->connections[i];
+
+               if(c->reapable) {
+                       continue;
+               }
+
+               utcp_expect_data(c, offline);
+
+               if(!offline) {
+                       if(timerisset(&c->rtrx_timeout)) {
+                               c->rtrx_timeout = now;
+                       }
+
+                       utcp->connections[i]->rtt_start.tv_sec = 0;
+               }
+       }
+
+       if(!offline && utcp->rto > START_RTO) {
+               utcp->rto = START_RTO;
+       }
+}