#include <sys/time.h>
#include <sys/socket.h>
-#define UTCP_INTERNAL
-#include "utcp.h"
-
-#define PREP(l) char pkt[(l) + sizeof struct hdr]; struct hdr *hdr = &pkt;
-
-#define SYN 1
-#define ACK 2
-#define FIN 4
-#define RST 8
-
-struct hdr {
- uint16_t src; // Source port
- uint16_t dst; // Destination port
- uint32_t seq; // Sequence number
- uint32_t ack; // Acknowledgement number
- uint32_t wnd; // Window size
- uint16_t ctl; // Flags (SYN, ACK, FIN, RST)
- uint16_t aux; // other stuff
-};
-
-enum state {
- CLOSED,
- LISTEN,
- SYN_SENT,
- SYN_RECEIVED,
- ESTABLISHED,
- FIN_WAIT_1,
- FIN_WAIT_2,
- CLOSE_WAIT,
- CLOSING,
- LAST_ACK,
- TIME_WAIT
-};
-
-const char *strstate[] = {
- "CLOSED",
- "LISTEN",
- "SYN_SENT",
- "SYN_RECEIVED",
- "ESTABLISHED",
- "FIN_WAIT_1",
- "FIN_WAIT_2",
- "CLOSE_WAIT",
- "CLOSING",
- "LAST_ACK",
- "TIME_WAIT"
-};
-
-struct utcp_connection {
- void *priv;
- struct utcp *utcp;
- bool reapable;
-
- uint16_t src;
- uint16_t dst;
- enum state state;
-
- // The following two structures form the TCB
+#include "utcp_priv.h"
- struct {
- uint32_t una;
- uint32_t nxt;
- uint32_t wnd;
- uint32_t up;
- uint32_t wl1;
- uint32_t wl2;
- uint32_t iss;
- } snd;
-
- struct {
- uint32_t nxt;
- uint32_t wnd;
- uint32_t up;
- uint32_t irs;
- } rcv;
-
- utcp_recv_t recv;
-
- struct timeval conn_timeout;
- struct timeval rtrx_timeout;
-
- char *sndbuf;
- uint32_t sndbufsize;
-};
+#ifdef UTCP_DEBUG
+#include <stdarg.h>
-struct utcp {
- void *priv;
-
- utcp_accept_t accept;
- utcp_pre_accept_t pre_accept;
- utcp_send_t send;
-
- uint16_t mtu;
-
- struct utcp_connection **connections;
- int nconnections;
- int nallocated;
- int gap;
-};
-
-static void set_state(struct utcp_connection *c, enum state state) {
- c->state = state;
- fprintf(stderr, "%p new state: %s\n", c->utcp, strstate[state]);
+static void debug(const char *format, ...) {
+ va_list ap;
+ va_start(ap, format);
+ vfprintf(stderr, format, ap);
+ va_end(ap);
}
-static void print_packet(void *pkt, size_t len) {
+static void print_packet(struct utcp *utcp, const char *dir, const void *pkt, size_t len) {
struct hdr hdr;
if(len < sizeof hdr) {
- fprintf(stderr, "short packet (%zu bytes)\n", len);
+ debug("%p %s: short packet (%zu bytes)\n", utcp, dir, len);
return;
}
memcpy(&hdr, pkt, sizeof hdr);
- fprintf (stderr, "src=%u dst=%u seq=%u ack=%u wnd=%u ctl=", hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd);
+ 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);
if(hdr.ctl & SYN)
- fprintf(stderr, "SYN");
+ debug("SYN");
if(hdr.ctl & RST)
- fprintf(stderr, "RST");
+ debug("RST");
if(hdr.ctl & FIN)
- fprintf(stderr, "FIN");
+ debug("FIN");
if(hdr.ctl & ACK)
- fprintf(stderr, "ACK");
+ debug("ACK");
if(len > sizeof hdr) {
- fprintf(stderr, " data=");
+ debug(" data=");
for(int i = sizeof hdr; i < len; i++) {
- char *data = pkt;
- fprintf(stderr, "%c", data[i] >= 32 ? data[i] : '.');
+ const char *data = pkt;
+ debug("%c", data[i] >= 32 ? data[i] : '.');
}
}
- fprintf(stderr, "\n");
+ debug("\n");
+}
+#else
+#define debug(...)
+#define print_packet(...)
+#endif
+
+static void set_state(struct utcp_connection *c, enum state state) {
+ c->state = state;
+ if(state == ESTABLISHED)
+ timerclear(&c->conn_timeout);
+ debug("%p new state: %s\n", c->utcp, strstate[state]);
}
-static void list_connections(struct utcp *utcp) {
- fprintf(stderr, "%p has %d connections:\n", utcp, utcp->nconnections);
+static inline void list_connections(struct utcp *utcp) {
+ debug("%p has %d connections:\n", utcp, utcp->nconnections);
for(int i = 0; i < utcp->nconnections; i++)
- fprintf(stderr, " %u -> %u state %s\n", utcp->connections[i]->src, utcp->connections[i]->dst, strstate[utcp->connections[i]->state]);
+ debug(" %u -> %u state %s\n", utcp->connections[i]->src, utcp->connections[i]->dst, strstate[utcp->connections[i]->state]);
+}
+
+static int32_t seqdiff(uint32_t a, uint32_t b) {
+ return a - b;
}
// Connections are stored in a sorted list.
static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t src, uint16_t dst) {
// Check whether this combination of src and dst is free
-
+
if(src) {
if(find_connection(utcp, src, dst)) {
errno = EADDRINUSE;
else
utcp->nallocated *= 2;
struct utcp_connection **new_array = realloc(utcp->connections, utcp->nallocated * sizeof *utcp->connections);
- if(!new_array) {
- errno = ENOMEM;
+ if(!new_array)
return NULL;
- }
utcp->connections = new_array;
}
struct utcp_connection *c = calloc(1, sizeof *c);
- if(!c) {
- errno = ENOMEM;
+ if(!c)
+ return NULL;
+
+ c->sndbufsize = DEFAULT_SNDBUFSIZE;
+ c->maxsndbufsize = DEFAULT_MAXSNDBUFSIZE;
+ c->sndbuf = malloc(c->sndbufsize);
+ if(!c->sndbuf) {
+ free(c);
return NULL;
}
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
set_state(c, SYN_SENT);
+ print_packet(utcp, "send", &hdr, sizeof hdr);
utcp->send(utcp, &hdr, sizeof hdr);
- // Set timeout?
+ gettimeofday(&c->conn_timeout, NULL);
+ c->conn_timeout.tv_sec += utcp->timeout;
return c;
}
void utcp_accept(struct utcp_connection *c, utcp_recv_t recv, void *priv) {
if(c->reapable || c->state != SYN_RECEIVED) {
- fprintf(stderr, "Error: accept() called on invalid connection %p in state %s\n", c, strstate[c->state]);
+ debug("Error: accept() called on invalid connection %p in state %s\n", c, strstate[c->state]);
return;
}
- fprintf(stderr, "%p accepted, %p %p\n", c, recv, priv);
+ debug("%p accepted, %p %p\n", c, recv, priv);
c->recv = recv;
c->priv = priv;
set_state(c, ESTABLISHED);
}
-int utcp_send(struct utcp_connection *c, void *data, size_t len) {
+static void ack(struct utcp_connection *c, bool sendatleastone) {
+ int32_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);
+
+ fprintf(stderr, "ack, left=%d, cwndleft=%d, sendatleastone=%d\n", left, cwndleft, sendatleastone);
+ if(left < 0)
+ abort();
+
+ 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;
+
+ if(c->state != ESTABLISHED && !left && seglen) {
+ switch(c->state) {
+ case FIN_WAIT_1:
+ case CLOSING:
+ seglen--;
+ pkt.hdr.ctl |= FIN;
+ break;
+ default:
+ break;
+ }
+ }
+
+ 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) {
- fprintf(stderr, "Error: send() called on closed connection %p\n", c);
+ debug("Error: send() called on closed connection %p\n", c);
errno = EBADF;
return -1;
}
case LISTEN:
case SYN_SENT:
case SYN_RECEIVED:
- fprintf(stderr, "Error: send() called on unconnected connection %p\n", c);
+ debug("Error: send() called on unconnected connection %p\n", c);
errno = ENOTCONN;
return -1;
case ESTABLISHED:
case CLOSING:
case LAST_ACK:
case TIME_WAIT:
- fprintf(stderr, "Error: send() called on closing connection %p\n", c);
+ debug("Error: send() called on closing connection %p\n", c);
errno = EPIPE;
return -1;
}
+ // Add data to send buffer
+
if(!len)
return 0;
return -1;
}
-
- struct {
- struct hdr hdr;
- char data[len];
- } pkt;
+ uint32_t bufused = seqdiff(c->snd.nxt, c->snd.una);
- pkt.hdr.src = c->src;
- pkt.hdr.dst = c->dst;
- pkt.hdr.seq = c->snd.nxt;
- pkt.hdr.ack = c->rcv.nxt;
- pkt.hdr.wnd = c->snd.wnd;
- pkt.hdr.ctl = ACK;
+ /* Check our send buffer.
+ * - If it's big enough, just put the data in there.
+ * - If not, decide whether to enlarge if possible.
+ * - Cap len so it doesn't overflow our buffer.
+ */
- memcpy(pkt.data, data, len);
+ if(len > c->sndbufsize - bufused && c->sndbufsize < c->maxsndbufsize) {
+ uint32_t newbufsize;
+ if(c->sndbufsize > c->maxsndbufsize / 2)
+ newbufsize = c->maxsndbufsize;
+ else
+ newbufsize = c->sndbufsize * 2;
+ if(bufused + len > newbufsize) {
+ if(bufused + len > c->maxsndbufsize)
+ newbufsize = c->maxsndbufsize;
+ else
+ newbufsize = bufused + len;
+ }
+ char *newbuf = realloc(c->sndbuf, newbufsize);
+ if(newbuf) {
+ c->sndbuf = newbuf;
+ c->sndbufsize = newbufsize;
+ }
+ }
- c->snd.nxt += len;
+ if(len > c->sndbufsize - bufused)
+ len = c->sndbufsize - bufused;
- c->utcp->send(c->utcp, &pkt, sizeof pkt.hdr + len);
- //
- // Can we add it to the send window?
-
- // Do we need to kick some timers?
-
- return 0;
+ if(!len) {
+ errno == EWOULDBLOCK;
+ return 0;
+ }
+
+ memcpy(c->sndbuf + bufused, data, len);
+ c->snd.last += len;
+
+ ack(c, false);
+ return len;
}
static void swap_ports(struct hdr *hdr) {
hdr->dst = tmp;
}
-static int16_t seqdiff(uint16_t a, uint16_t b) {
- return a -b;
-}
-
-int utcp_recv(struct utcp *utcp, void *data, size_t len) {
+int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
if(!utcp) {
errno = EFAULT;
return -1;
return -1;
}
- fprintf(stderr, "%p got: ", utcp);
- print_packet(data, len);
+ print_packet(utcp, "recv", data, len);
+
+ // Drop packets smaller than the header
struct hdr hdr;
if(len < sizeof hdr) {
return -1;
}
+ // Make a copy from the potentially unaligned data to a struct hdr
+
memcpy(&hdr, data, sizeof hdr);
data += sizeof hdr;
len -= sizeof hdr;
+ // Drop packets with an unknown CTL flag
+
if(hdr.ctl & ~(SYN | ACK | RST | FIN)) {
errno = EBADMSG;
return -1;
}
- //list_connections(utcp);
+ // Try to match the packet to an existing connection
struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
// Is it for a new connection?
if(!c) {
+ // Ignore RST packets
+
if(hdr.ctl & RST)
return 0;
- if(hdr.ctl & SYN && !(hdr.ctl & ACK) && utcp->accept && (!utcp->pre_accept || utcp->pre_accept(utcp, hdr.dst)) && (c = allocate_connection(utcp, hdr.dst, hdr.src))) { // LISTEN
- // Return SYN+ACK
+ // Is it a SYN packet and are we LISTENing?
+
+ if(hdr.ctl & SYN && !(hdr.ctl & ACK) && utcp->accept) {
+ // If we don't want to accept it, send a RST back
+ if((utcp->pre_accept && !utcp->pre_accept(utcp, hdr.dst))) {
+ len = 1;
+ goto reset;
+ }
+
+ // Try to allocate memory, otherwise send a RST back
+ c = allocate_connection(utcp, hdr.dst, hdr.src);
+ if(!c) {
+ len = 1;
+ goto reset;
+ }
+
+ // Return SYN+ACK, go to SYN_RECEIVED state
c->snd.wnd = hdr.wnd;
c->rcv.irs = hdr.seq;
c->rcv.nxt = c->rcv.irs + 1;
hdr.ack = c->rcv.irs + 1;
hdr.seq = c->snd.iss;
hdr.ctl = SYN | ACK;
+ print_packet(c->utcp, "send", &hdr, sizeof hdr);
utcp->send(utcp, &hdr, sizeof hdr);
- return 0;
- } else { // CLOSED
+ } else {
+ // No, we don't want your packets, send a RST back
len = 1;
goto reset;
}
+
+ return 0;
}
- fprintf(stderr, "%p state %s\n", c->utcp, strstate[c->state]);
+ debug("%p state %s\n", c->utcp, strstate[c->state]);
- if(c->state == CLOSED) {
- fprintf(stderr, "Error: packet recv()d on closed connection %p\n", c);
- errno = EBADF;
- return -1;
- }
+ // In case this is for a CLOSED connection, ignore the packet.
+ // TODO: make it so incoming packets can never match a CLOSED connection.
+
+ if(c->state == CLOSED)
+ return 0;
// It is for an existing connection.
-
- if(c->state == SYN_SENT) {
- if(hdr.ctl & ACK) {
- if(seqdiff(hdr.ack, c->snd.iss) <= 0 || seqdiff(hdr.ack, c->snd.nxt) > 0) {
- fprintf(stderr, "Invalid ACK, %u %u %u\n", hdr.ack, c->snd.iss, c->snd.nxt);
- goto reset;
- }
- }
- if(hdr.ctl & RST) {
- if(!(hdr.ctl & ACK))
- return 0;
- set_state(c, CLOSED);
- errno = ECONNREFUSED;
- c->recv(c, NULL, 0);
- return 0;
- }
- if(hdr.ctl & SYN) {
- c->dst = hdr.src;
- c->rcv.nxt = hdr.seq + 1;
- c->rcv.irs = hdr.seq;
- c->snd.wnd = hdr.wnd;
- if(hdr.ctl & ACK)
- c->snd.una = hdr.ack;
- if(seqdiff(c->snd.una, c->snd.iss) > 0) {
- set_state(c, ESTABLISHED);
- // TODO: signal app?
- swap_ports(&hdr);
- hdr.seq = c->snd.nxt;
- hdr.ack = c->rcv.nxt;
- hdr.ctl = ACK;
- } else {
- set_state(c, SYN_RECEIVED);
- swap_ports(&hdr);
- hdr.seq = c->snd.iss;
- hdr.ack = c->rcv.nxt;
- hdr.ctl = SYN | ACK;
- }
- utcp->send(utcp, &hdr, sizeof hdr);
- // TODO: queue any data?
- }
+ // 1. Drop invalid packets.
- return 0;
+ // 1a. Drop packets that should not happen in our current state.
+
+ switch(c->state) {
+ case SYN_SENT:
+ case SYN_RECEIVED:
+ case ESTABLISHED:
+ case FIN_WAIT_1:
+ case FIN_WAIT_2:
+ case CLOSE_WAIT:
+ case CLOSING:
+ case LAST_ACK:
+ case TIME_WAIT:
+ break;
+ default:
+ abort();
}
+ // 1b. Drop packets with a sequence number not in our receive window.
+
bool acceptable;
- if(len == 0)
+ if(c->state == SYN_SENT)
+ acceptable = true;
+
+ // TODO: handle packets overlapping c->rcv.nxt.
+#if 0
+ // Only use this when accepting out-of-order packets.
+ else if(len == 0)
if(c->rcv.wnd == 0)
acceptable = hdr.seq == c->rcv.nxt;
else
- acceptable = (hdr.seq >= c->rcv.nxt && hdr.seq < c->rcv.nxt + c->rcv.wnd);
+ acceptable = (seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt + c->rcv.wnd) < 0);
else
if(c->rcv.wnd == 0)
+ // We don't accept data when the receive window is zero.
acceptable = false;
else
- acceptable = (hdr.seq >= c->rcv.nxt && hdr.seq < c->rcv.nxt + c->rcv.wnd)
- || (hdr.seq + len - 1 >= c->rcv.nxt && hdr.seq + len - 1 < c->rcv.nxt + c->rcv.wnd);
+ // Both start and end of packet must be within the receive window
+ acceptable = (seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt + c->rcv.wnd) < 0)
+ || (seqdiff(hdr.seq + len + 1, c->rcv.nxt) >= 0 && seqdiff(hdr.seq + len - 1, c->rcv.nxt + c->rcv.wnd) < 0);
+#else
+ if(c->state != SYN_SENT)
+ acceptable = hdr.seq == c->rcv.nxt;
+#endif
if(!acceptable) {
- fprintf(stderr, "Packet not acceptable, %u %u %u %zu\n", hdr.seq, c->rcv.nxt, c->rcv.wnd, len);
+ debug("Packet not acceptable, %u <= %u + %zu < %u\n", c->rcv.nxt, hdr.seq, len, c->rcv.nxt + c->rcv.wnd);
+ // Ignore unacceptable RST packets.
if(hdr.ctl & RST)
return 0;
- goto ack_and_drop;
+ // Otherwise, send an ACK back in the hope things improve.
+ goto ack;
}
- c->snd.wnd = hdr.wnd;
+ c->snd.wnd = hdr.wnd; // TODO: move below
+
+ // 1c. Drop packets with an invalid ACK.
+ // ackno should not roll back, and it should also not be bigger than snd.nxt.
+
+ if(hdr.ctl & ACK && (seqdiff(hdr.ack, c->snd.nxt) > 0 || seqdiff(hdr.ack, c->snd.una) < 0)) {
+ debug("Packet ack seqno out of range, %u %u %u\n", hdr.ack, c->snd.una, c->snd.nxt);
+ // Ignore unacceptable RST packets.
+ if(hdr.ctl & RST)
+ return 0;
+ goto reset;
+ }
+
+ // 2. Handle RST packets
- // TODO: check whether segment really starts at rcv.nxt, otherwise trim it.
-
if(hdr.ctl & RST) {
switch(c->state) {
+ case SYN_SENT:
+ if(!(hdr.ctl & ACK))
+ return 0;
+ // The peer has refused our connection.
+ set_state(c, CLOSED);
+ errno = ECONNREFUSED;
+ if(c->recv)
+ c->recv(c, NULL, 0);
+ return 0;
case SYN_RECEIVED:
- // TODO: delete connection?
- break;
+ if(hdr.ctl & ACK)
+ return 0;
+ // We haven't told the application about this connection yet. Silently delete.
+ free_connection(c);
+ return 0;
case ESTABLISHED:
case FIN_WAIT_1:
case FIN_WAIT_2:
case CLOSE_WAIT:
+ if(hdr.ctl & ACK)
+ return 0;
+ // The peer has aborted our connection.
set_state(c, CLOSED);
errno = ECONNRESET;
- c->recv(c, NULL, 0);
- break;
+ if(c->recv)
+ c->recv(c, NULL, 0);
+ return 0;
case CLOSING:
case LAST_ACK:
case TIME_WAIT:
- // TODO: delete connection?
+ if(hdr.ctl & ACK)
+ return 0;
+ // As far as the application is concerned, the connection has already been closed.
+ // If it has called utcp_close() already, we can immediately free this connection.
+ if(c->reapable) {
+ free_connection(c);
+ return 0;
+ }
+ // Otherwise, immediately move to the CLOSED state.
+ set_state(c, CLOSED);
+ return 0;
+ default:
+ abort();
+ }
+ }
+
+ // 3. Advance snd.una
+
+ uint32_t advanced = seqdiff(hdr.ack, c->snd.una);
+ c->snd.una = hdr.ack;
+
+ if(advanced) {
+ debug("%p advanced %u\n", utcp, advanced);
+ // 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);
+ 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) {
+ case FIN_WAIT_1:
+ if(c->snd.una == c->snd.last)
+ set_state(c, FIN_WAIT_2);
+ break;
+ case CLOSING:
+ if(c->snd.una == c->snd.last) {
+ gettimeofday(&c->conn_timeout, NULL);
+ c->conn_timeout.tv_sec += 60;
+ set_state(c, TIME_WAIT);
+ }
break;
default:
- // TODO: wtf?
- return 0;
+ break;
+ }
+ } else {
+ if(!len) {
+ c->dupack++;
+ if(c->dupack >= 3) {
+ debug("Triplicate ACK\n");
+ abort();
+ }
}
- set_state(c, CLOSED);
- return 0;
}
+ // 4. Update timers
+
+ if(advanced) {
+ timerclear(&c->conn_timeout); // It should be set anew in utcp_timeout() if c->snd.una != c->snd.nxt.
+ if(c->snd.una == c->snd.nxt)
+ timerclear(&c->rtrx_timeout);
+ }
+
+ // 5. Process SYN stuff
+
if(hdr.ctl & SYN) {
switch(c->state) {
+ case SYN_SENT:
+ // This is a SYNACK. It should always have ACKed the SYN.
+ if(!advanced)
+ goto reset;
+ c->rcv.irs = hdr.seq;
+ c->rcv.nxt = hdr.seq;
+ set_state(c, ESTABLISHED);
+ // TODO: notify application of this somehow.
+ break;
case SYN_RECEIVED:
case ESTABLISHED:
case FIN_WAIT_1:
case CLOSING:
case LAST_ACK:
case TIME_WAIT:
- set_state(c, CLOSED);
- errno = ECONNRESET;
- c->recv(c, NULL, 0);
+ // Ehm, no. We should never receive a second SYN.
goto reset;
- break;
default:
- // TODO: wtf?
- return 0;
+ abort();
}
+
+ // SYN counts as one sequence number
+ c->rcv.nxt++;
}
- if(!(hdr.ctl & ACK))
- return 0;
+ // 6. Process new data
- switch(c->state) {
- case SYN_RECEIVED:
- if(seqdiff(hdr.ack, c->snd.una) >= 0 && seqdiff(hdr.ack, c->snd.nxt) <= 0)
- c->utcp->accept(c, hdr.dst);
-
- if(c->state != ESTABLISHED)
+ if(c->state == SYN_RECEIVED) {
+ // This is the ACK after the SYNACK. It should always have ACKed the SYNACK.
+ if(!advanced)
goto reset;
- break;
- case ESTABLISHED:
- case CLOSE_WAIT:
- if(seqdiff(hdr.ack, c->snd.una) < 0)
- return 0;
- if(seqdiff(hdr.ack, c->snd.nxt) > 0)
- goto ack_and_drop;
- if(seqdiff(hdr.ack, c->snd.una) > 0 && seqdiff(hdr.ack, c->snd.nxt) <= 0) {
- c->snd.una = hdr.ack;
- if(seqdiff(c->snd.wl1, hdr.seq) < 0 || (c->snd.wl1 == hdr.seq && seqdiff(c->snd.wl2, hdr.ack) <= 0)) {
- c->snd.wnd = hdr.wnd;
- c->snd.wl1 = hdr.seq;
- c->snd.wl2 = hdr.ack;
- }
- }
- break;
- case FIN_WAIT_1:
- if(hdr.ack == c->snd.nxt)
- set_state(c, FIN_WAIT_2);
- break;
- case FIN_WAIT_2:
- // TODO: If nothing left to send, close.
- break;
- case CLOSING:
- if(hdr.ack == c->snd.nxt) {
- set_state(c, TIME_WAIT);
- }
- break;
- case LAST_ACK:
- if(hdr.ack == c->snd.nxt) {
+
+ // Are we still LISTENing?
+ if(utcp->accept)
+ utcp->accept(c, c->src);
+
+ if(c->state != ESTABLISHED) {
set_state(c, CLOSED);
+ c->reapable = true;
+ goto reset;
}
- return 0;
- case TIME_WAIT:
- // TODO: retransmission of remote FIN, ACK and restart 2 MSL timeout
- break;
- default:
- goto reset;
}
- // Process data
+ if(len) {
+ switch(c->state) {
+ case SYN_SENT:
+ case SYN_RECEIVED:
+ // This should never happen.
+ abort();
+ case ESTABLISHED:
+ case FIN_WAIT_1:
+ case FIN_WAIT_2:
+ break;
+ case CLOSE_WAIT:
+ case CLOSING:
+ case LAST_ACK:
+ case TIME_WAIT:
+ // Ehm no, We should never receive more data after a FIN.
+ goto reset;
+ default:
+ abort();
+ }
+
+ int rxd;
- switch(c->state) {
- case ESTABLISHED:
- case FIN_WAIT_1:
- case FIN_WAIT_2:
- // TODO: process the data, see page 74
- break;
- case CLOSE_WAIT:
- case CLOSING:
- case LAST_ACK:
- case TIME_WAIT:
- break;
- default:
- abort();
+ if(c->recv) {
+ rxd = c->recv(c, data, len);
+ if(rxd < 0)
+ rxd = 0;
+ else if(rxd > len)
+ rxd = len; // Bad application, bad!
+ } else {
+ rxd = len;
+ }
+
+ c->rcv.nxt += len;
}
+ // 7. Process FIN stuff
+
if(hdr.ctl & FIN) {
switch(c->state) {
- case CLOSED:
- case LISTEN:
case SYN_SENT:
- return 0;
case SYN_RECEIVED:
+ // This should never happen.
+ abort();
case ESTABLISHED:
set_state(c, CLOSE_WAIT);
- c->rcv.nxt++;
- goto ack_and_drop;
+ break;
case FIN_WAIT_1:
set_state(c, CLOSING);
- c->rcv.nxt++;
- goto ack_and_drop;
+ break;
case FIN_WAIT_2:
+ gettimeofday(&c->conn_timeout, NULL);
+ c->conn_timeout.tv_sec += 60;
set_state(c, TIME_WAIT);
- c->rcv.nxt++;
- goto ack_and_drop;
+ break;
case CLOSE_WAIT:
case CLOSING:
case LAST_ACK:
case TIME_WAIT:
- break;
+ // Ehm, no. We should never receive a second FIN.
+ goto reset;
default:
abort();
}
- }
- // Process the data
-
- if(len && c->recv) {
- c->recv(c, data, len);
- c->rcv.nxt += len;
- goto ack_and_drop;
+ // FIN counts as one sequence number
+ c->rcv.nxt++;
+
+ // Inform the application that the peer closed the connection.
+ if(c->recv) {
+ errno = 0;
+ c->recv(c, NULL, 0);
+ }
}
+ if(!len && !advanced)
+ return 0;
+
+ if(!len && !(hdr.ctl & SYN) && !(hdr.ctl & FIN))
+ return 0;
+
+ack:
+ ack(c, true);
return 0;
reset:
hdr.seq = 0;
hdr.ctl = RST | ACK;
}
+ print_packet(utcp, "send", &hdr, sizeof hdr);
utcp->send(utcp, &hdr, sizeof hdr);
return 0;
-ack_and_drop:
- swap_ports(&hdr);
- hdr.seq = c->snd.nxt;
- hdr.ack = c->rcv.nxt;
- hdr.ctl = ACK;
- utcp->send(utcp, &hdr, sizeof hdr);
- if(c->state == CLOSE_WAIT || c->state == TIME_WAIT) {
- errno = 0;
- c->recv(c, NULL, 0);
- }
- return 0;
}
int utcp_shutdown(struct utcp_connection *c, int dir) {
+ debug("%p shutdown %d\n", c->utcp, dir);
if(!c) {
errno = EFAULT;
return -1;
}
if(c->reapable) {
- fprintf(stderr, "Error: shutdown() called on closed connection %p\n", c);
+ debug("Error: shutdown() called on closed connection %p\n", c);
errno = EBADF;
return -1;
}
case FIN_WAIT_2:
return 0;
case CLOSE_WAIT:
- set_state(c, LAST_ACK);
+ set_state(c, CLOSING);
break;
case CLOSING:
return 0;
}
- // Send FIN
-
- struct hdr hdr;
-
- hdr.src = c->src;
- hdr.dst = c->dst;
- hdr.seq = c->snd.nxt;
- hdr.ack = c->rcv.nxt;
- hdr.wnd = c->snd.wnd;
- hdr.ctl = FIN | ACK;
-
- c->snd.nxt += 1;
+ c->snd.last++;
- c->utcp->send(c->utcp, &hdr, sizeof hdr);
+ ack(c, false);
return 0;
}
}
if(c->reapable) {
- fprintf(stderr, "Error: abort() called on closed connection %p\n", c);
+ debug("Error: abort() called on closed connection %p\n", c);
errno = EBADF;
return -1;
}
hdr.wnd = 0;
hdr.ctl = RST;
+ print_packet(c->utcp, "send", &hdr, sizeof hdr);
c->utcp->send(c->utcp, &hdr, sizeof hdr);
return 0;
}
-void utcp_timeout(struct utcp *utcp) {
+static void retransmit(struct utcp_connection *c) {
+ if(c->state == CLOSED || c->snd.nxt == c->snd.una)
+ return;
+
+ struct utcp *utcp = c->utcp;
+
+ struct {
+ struct hdr hdr;
+ char data[c->utcp->mtu];
+ } pkt;
+
+ pkt.hdr.src = c->src;
+ pkt.hdr.dst = c->dst;
+
+ switch(c->state) {
+ case LISTEN:
+ // TODO: this should not happen
+ break;
+
+ case SYN_SENT:
+ pkt.hdr.seq = c->snd.iss;
+ pkt.hdr.ack = 0;
+ pkt.hdr.wnd = c->rcv.wnd;
+ pkt.hdr.ctl = SYN;
+ print_packet(c->utcp, "rtrx", &pkt, sizeof pkt.hdr);
+ utcp->send(utcp, &pkt, sizeof pkt.hdr);
+ break;
+
+ case SYN_RECEIVED:
+ pkt.hdr.seq = c->snd.nxt;
+ pkt.hdr.ack = c->rcv.nxt;
+ pkt.hdr.ctl = SYN | ACK;
+ print_packet(c->utcp, "rtrx", &pkt, sizeof pkt.hdr);
+ utcp->send(utcp, &pkt, sizeof pkt.hdr);
+ break;
+
+ case ESTABLISHED:
+ case FIN_WAIT_1:
+ pkt.hdr.seq = c->snd.una;
+ pkt.hdr.ack = c->rcv.nxt;
+ pkt.hdr.ctl = ACK;
+ uint32_t len = seqdiff(c->snd.nxt, c->snd.una);
+ if(c->state == FIN_WAIT_1)
+ len--;
+ if(len > utcp->mtu)
+ len = utcp->mtu;
+ else {
+ if(c->state == FIN_WAIT_1)
+ pkt.hdr.ctl |= FIN;
+ }
+ memcpy(pkt.data, c->sndbuf, len);
+ print_packet(c->utcp, "rtrx", &pkt, sizeof pkt.hdr + len);
+ utcp->send(utcp, &pkt, sizeof pkt.hdr + len);
+ break;
+
+ default:
+ // TODO: implement
+ abort();
+ }
+}
+
+/* Handle timeouts.
+ * One call to this function will loop through all connections,
+ * checking if something needs to be resent or not.
+ * The return value is the time to the next timeout in milliseconds,
+ * or maybe a negative value if the timeout is infinite.
+ */
+int utcp_timeout(struct utcp *utcp) {
struct timeval now;
gettimeofday(&now, NULL);
+ struct timeval next = {now.tv_sec + 3600, now.tv_usec};
for(int i = 0; i < utcp->nconnections; i++) {
struct utcp_connection *c = utcp->connections[i];
if(!c)
continue;
- if(c->reapable) {
- fprintf(stderr, "Reaping %p\n", c);
- free_connection(c);
+ if(c->state == CLOSED) {
+ if(c->reapable) {
+ debug("Reaping %p\n", c);
+ free_connection(c);
+ i--;
+ }
continue;
}
- if(c->state == CLOSED)
- return;
-
- if(c->conn_timeout.tv_sec && timercmp(&c->conn_timeout, &now, <)) {
- if(!c->reapable) {
- errno = ETIMEDOUT;
- c->recv(c, NULL, 0);
- }
+ if(timerisset(&c->conn_timeout) && timercmp(&c->conn_timeout, &now, <)) {
+ errno = ETIMEDOUT;
c->state = CLOSED;
- return;
+ if(c->recv)
+ c->recv(c, NULL, 0);
+ continue;
}
- if(c->rtrx_timeout.tv_sec && timercmp(&c->rtrx_timeout, &now, <)) {
- // TODO: retransmit stuff;
+ if(timerisset(&c->rtrx_timeout) && timercmp(&c->rtrx_timeout, &now, <)) {
+ retransmit(c);
}
+
+ if(timerisset(&c->conn_timeout) && timercmp(&c->conn_timeout, &next, <))
+ next = c->conn_timeout;
+
+ if(c->snd.nxt != c->snd.una) {
+ c->rtrx_timeout = now;
+ c->rtrx_timeout.tv_sec++;
+ } else {
+ timerclear(&c->rtrx_timeout);
+ }
+
+ if(timerisset(&c->rtrx_timeout) && timercmp(&c->rtrx_timeout, &next, <))
+ next = c->rtrx_timeout;
}
+
+ struct timeval diff;
+ timersub(&next, &now, &diff);
+ if(diff.tv_sec < 0)
+ return 0;
+ return diff.tv_sec * 1000 + diff.tv_usec / 1000;
}
struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_send_t send, void *priv) {
if(!utcp)
return NULL;
+ if(!send) {
+ errno = EFAULT;
+ return NULL;
+ }
+
utcp->accept = accept;
utcp->pre_accept = pre_accept;
utcp->send = send;
utcp->priv = priv;
- utcp->gap = -1;
utcp->mtu = 1000;
+ utcp->timeout = 60;
return utcp;
}
free_connection(utcp->connections[i]);
free(utcp);
}
+
+uint16_t utcp_get_mtu(struct utcp *utcp) {
+ return utcp->mtu;
+}
+
+void utcp_set_mtu(struct utcp *utcp, uint16_t mtu) {
+ // TODO: handle overhead of the header
+ utcp->mtu = mtu;
+}
+
+int utcp_get_user_timeout(struct utcp *u) {
+ return u->timeout;
+}
+
+void utcp_set_user_timeout(struct utcp *u, int timeout) {
+ u->timeout = timeout;
+}
+
+size_t utcp_get_sndbuf(struct utcp_connection *c) {
+ return c->maxsndbufsize;
+}
+
+void utcp_set_sndbuf(struct utcp_connection *c, size_t size) {
+ c->maxsndbufsize = size;
+ if(c->maxsndbufsize != size)
+ c->maxsndbufsize = -1;
+}
+
+bool utcp_get_nodelay(struct utcp_connection *c) {
+ return c->nodelay;
+}
+
+void utcp_set_nodelay(struct utcp_connection *c, bool nodelay) {
+ c->nodelay = nodelay;
+}
+
+bool utcp_get_keepalive(struct utcp_connection *c) {
+ return c->keepalive;
+}
+
+void utcp_set_keepalive(struct utcp_connection *c, bool keepalive) {
+ c->keepalive = keepalive;
+}
+
+size_t utcp_get_outq(struct utcp_connection *c) {
+ return seqdiff(c->snd.nxt, c->snd.una);
+}
projects / utcp / blobdiff