#define _GNU_SOURCE
+#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#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 iss;
- } snd;
-
- struct {
- uint32_t nxt;
- uint32_t wnd;
- uint32_t irs;
- } rcv;
-
- utcp_recv_t recv;
-
- struct timeval conn_timeout;
- struct timeval rtrx_timeout;
+#ifndef EBADMSG
+#define EBADMSG 104
+#endif
- char *sndbuf;
- uint32_t sndbufsize;
-};
+#ifndef SHUT_RDWR
+#define SHUT_RDWR 2
+#endif
-struct utcp {
- void *priv;
+#ifdef poll
+#undef poll
+#endif
- utcp_accept_t accept;
- utcp_pre_accept_t pre_accept;
- utcp_send_t send;
+#ifndef timersub
+#define timersub(a, b, r) do {\
+ (r)->tv_sec = (a)->tv_sec - (b)->tv_sec;\
+ (r)->tv_usec = (a)->tv_usec - (b)->tv_usec;\
+ if((r)->tv_usec < 0)\
+ (r)->tv_sec--, (r)->tv_usec += 1000000;\
+} while (0)
+#endif
- uint16_t mtu;
- int timeout;
+#ifndef max
+#define max(a, b) ((a) > (b) ? (a) : (b))
+#endif
- struct utcp_connection **connections;
- int nconnections;
- int nallocated;
-};
+#ifdef UTCP_DEBUG
+#include <stdarg.h>
-static void set_state(struct utcp_connection *c, enum state state) {
- c->state = state;
- if(state == ESTABLISHED)
- timerclear(&c->conn_timeout);
- 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(struct utcp *utcp, const char *dir, const void *pkt, size_t len) {
struct hdr hdr;
if(len < sizeof hdr) {
- fprintf(stderr, "%p %s: short packet (%zu bytes)\n", utcp, dir, len);
+ debug("%p %s: short packet (%zu bytes)\n", utcp, dir, len);
return;
}
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)
- 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++) {
const char *data = pkt;
- fprintf(stderr, "%c", data[i] >= 32 ? data[i] : '.');
+ 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 bool fin_wanted(struct utcp_connection *c, uint32_t seq) {
+ if(seq != c->snd.last)
+ return false;
+ switch(c->state) {
+ case FIN_WAIT_1:
+ case CLOSING:
+ case LAST_ACK:
+ return true;
+ default:
+ return false;
+ }
}
static inline void list_connections(struct utcp *utcp) {
- fprintf(stderr, "%p has %d connections:\n", utcp, utcp->nconnections);
+ 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;
+}
+
+// Buffer functions
+// TODO: convert to ringbuffers to avoid memmove() operations.
+
+// Store data into the buffer
+static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data, size_t len) {
+ if(buf->maxsize <= buf->used)
+ return 0;
+
+ debug("buffer_put_at %zu %zu %zu\n", buf->used, offset, len);
+
+ size_t required = offset + len;
+ if(required > buf->maxsize) {
+ if(offset >= buf->maxsize)
+ return 0;
+ abort();
+ len = buf->maxsize - offset;
+ required = buf->maxsize;
+ }
+
+ if(required > buf->size) {
+ size_t newsize = buf->size;
+ if(!newsize) {
+ newsize = required;
+ } else {
+ do {
+ newsize *= 2;
+ } while(newsize < buf->used + len);
+ }
+ if(newsize > buf->maxsize)
+ newsize = buf->maxsize;
+ char *newdata = realloc(buf->data, newsize);
+ if(!newdata)
+ return -1;
+ buf->data = newdata;
+ buf->size = newsize;
+ }
+
+ memcpy(buf->data + offset, data, len);
+ if(required > buf->used)
+ buf->used = required;
+ return len;
+}
+
+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;
+ if(data)
+ memcpy(data, buf->data, len);
+ if(len < buf->used)
+ memmove(buf->data, buf->data + len, buf->used - 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;
+ if(offset + len > buf->used)
+ len = buf->used - offset;
+ memcpy(data, buf->data + offset, len);
+ return len;
+}
+
+static bool buffer_init(struct buffer *buf, uint32_t len, uint32_t maxlen) {
+ memset(buf, 0, sizeof *buf);
+ if(len) {
+ buf->data = malloc(len);
+ if(!buf->data)
+ return false;
+ }
+ buf->size = len;
+ buf->maxsize = maxlen;
+ return true;
+}
+
+static void buffer_exit(struct buffer *buf) {
+ free(buf->data);
+ memset(buf, 0, sizeof *buf);
+}
+
+static uint32_t buffer_free(const struct buffer *buf) {
+ return buf->maxsize - buf->used;
}
// Connections are stored in a sorted list.
// This gives O(log(N)) lookup time, O(N log(N)) insertion time and O(N) deletion time.
static int compare(const void *va, const void *vb) {
+ assert(va && 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 && b);
+ assert(a->src && b->src);
+
int c = (int)a->src - (int)b->src;
if(c)
return c;
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);
+ memmove(cp, cp + 1, (utcp->nconnections - i - 1) * sizeof *cp);
utcp->nconnections--;
+ buffer_exit(&c->sndbuf);
free(c);
}
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;
+
+ if(!buffer_init(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
+ free(c);
+ return NULL;
+ }
+
+ if(!buffer_init(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
+ free(c);
return NULL;
}
c->src = src;
c->dst = dst;
+#ifdef UTCP_DEBUG
+ c->snd.iss = 0;
+#else
c->snd.iss = rand();
+#endif
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;
- c->sndbufsize = 65536;
- c->sndbuf = malloc(c->sndbufsize);
- if(!c->sndbuf)
- c->sndbufsize = 0;
// Add it to the sorted list of connections
return NULL;
c->recv = recv;
+ c->priv = priv;
struct hdr hdr;
hdr.dst = c->dst;
hdr.seq = c->snd.iss;
hdr.ack = 0;
- hdr.ctl = SYN;
hdr.wnd = c->rcv.wnd;
+ hdr.ctl = SYN;
+ hdr.aux = 0;
set_state(c, SYN_SENT);
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);
}
+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);
+ debug("cwndleft = %d\n", cwndleft);
+
+ assert(left >= 0);
+
+ if(cwndleft <= 0)
+ cwndleft = 0;
+
+ if(cwndleft < left)
+ left = cwndleft;
+
+ if(!left && !sendatleastone)
+ return;
+
+ struct {
+ struct hdr hdr;
+ char data[];
+ } *pkt;
+
+ pkt = malloc(sizeof pkt->hdr + c->utcp->mtu);
+ if(!pkt)
+ return;
+
+ 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;
+ pkt->hdr.aux = 0;
+
+ do {
+ uint32_t seglen = left > c->utcp->mtu ? c->utcp->mtu : left;
+ pkt->hdr.seq = c->snd.nxt;
+
+ buffer_copy(&c->sndbuf, pkt->data, seqdiff(c->snd.nxt, c->snd.una), seglen);
+
+ c->snd.nxt += seglen;
+ left -= seglen;
+
+ if(seglen && fin_wanted(c, c->snd.nxt)) {
+ seglen--;
+ pkt->hdr.ctl |= FIN;
+ }
+
+ 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) {
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;
}
return -1;
}
- uint32_t bufused = c->snd.nxt - c->snd.una;
-
- /* Check our send buffer.
- * - If it's big enough, just put the data in there.
- * - If not, decide whether to enlarge. (TODO, now we just always enlarge)
- * - Cap len so it doesn't overflow our buffer.
- */
-
- if(len > c->sndbufsize - bufused) {
- c->sndbufsize *= 2;
- c->sndbuf = realloc(c->sndbuf, c->sndbufsize);
+ len = buffer_put(&c->sndbuf, data, len);
+ if(len <= 0) {
+ errno = EWOULDBLOCK;
+ return 0;
}
- if(len > c->sndbufsize - bufused)
- len = c->sndbufsize - bufused;
+ c->snd.last += len;
+ ack(c, false);
+ return len;
+}
- if(!len) {
- errno == EWOULDBLOCK;
- return 0;
- }
+static void swap_ports(struct hdr *hdr) {
+ uint16_t tmp = hdr->src;
+ hdr->src = hdr->dst;
+ hdr->dst = tmp;
+}
- memcpy(c->sndbuf + bufused, data, len);
+static void retransmit(struct utcp_connection *c) {
+ if(c->state == CLOSED || c->snd.nxt == c->snd.una)
+ return;
- // Send segments
+ struct utcp *utcp = c->utcp;
struct {
struct hdr hdr;
- char data[c->utcp->mtu];
- } pkt;
+ char data[];
+ } *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;
+ pkt = malloc(sizeof pkt->hdr + c->utcp->mtu);
+ if(!pkt)
+ return;
- uint32_t left = len;
+ pkt->hdr.src = c->src;
+ pkt->hdr.dst = c->dst;
- while(left) {
- uint32_t seglen = left > c->utcp->mtu ? c->utcp->mtu : left;
- pkt.hdr.seq = c->snd.nxt;
+ switch(c->state) {
+ case SYN_SENT:
+ // Send our SYN again
+ 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;
- memcpy(pkt.data, data, seglen);
+ case SYN_RECEIVED:
+ // Send SYNACK again
+ 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;
- c->snd.nxt += seglen;
- data += seglen;
- left -= seglen;
+ case ESTABLISHED:
+ case FIN_WAIT_1:
+ case CLOSE_WAIT:
+ case CLOSING:
+ case LAST_ACK:
+ // Send unacked data again.
+ pkt->hdr.seq = c->snd.una;
+ pkt->hdr.ack = c->rcv.nxt;
+ pkt->hdr.ctl = ACK;
+ uint32_t len = seqdiff(c->snd.last, c->snd.una);
+ if(len > utcp->mtu)
+ len = utcp->mtu;
+ if(fin_wanted(c, c->snd.una + len)) {
+ len--;
+ pkt->hdr.ctl |= FIN;
+ }
+ c->snd.nxt = c->snd.una + len;
+ c->snd.cwnd = utcp->mtu; // reduce cwnd on retransmit
+ buffer_copy(&c->sndbuf, pkt->data, 0, len);
+ print_packet(c->utcp, "rtrx", pkt, sizeof pkt->hdr + len);
+ utcp->send(utcp, pkt, sizeof pkt->hdr + len);
+ break;
- print_packet(c->utcp, "send", &pkt, sizeof pkt.hdr + seglen);
- c->utcp->send(c->utcp, &pkt, sizeof pkt.hdr + seglen);
+ case CLOSED:
+ case LISTEN:
+ case TIME_WAIT:
+ case FIN_WAIT_2:
+ // We shouldn't need to retransmit anything in this state.
+#ifdef UTCP_DEBUG
+ abort();
+#endif
+ timerclear(&c->rtrx_timeout);
+ break;
}
- fprintf(stderr, "len=%zu\n", len);
- return len;
+ free(pkt);
}
-static void swap_ports(struct hdr *hdr) {
- uint16_t tmp = hdr->src;
- hdr->src = hdr->dst;
- hdr->dst = tmp;
+// Update receive buffer and SACK entries after consuming data.
+static void sack_consume(struct utcp_connection *c, size_t len) {
+ debug("sack_consume %zu\n", len);
+ if(len > c->rcvbuf.used)
+ abort();
+
+ buffer_get(&c->rcvbuf, NULL, len);
+
+ for(int i = 0; i < NSACKS && c->sacks[i].len; ) {
+ if(len < c->sacks[i].offset) {
+ c->sacks[i].offset -= len;
+ i++;
+ } else if(len < c->sacks[i].offset + c->sacks[i].len) {
+ c->sacks[i].offset = 0;
+ c->sacks[i].len -= len - c->sacks[i].offset;
+ i++;
+ } else {
+ if(i < NSACKS - 1) {
+ memmove(&c->sacks[i], &c->sacks[i + 1], (NSACKS - 1 - i) * sizeof c->sacks[i]);
+ c->sacks[i + 1].len = 0;
+ } else {
+ c->sacks[i].len = 0;
+ break;
+ }
+ }
+ }
+
+ for(int i = 0; i < NSACKS && c->sacks[i].len; i++)
+ debug("SACK[%d] offset %u len %u\n", i, c->sacks[i].offset, c->sacks[i].len);
}
-static int32_t seqdiff(uint32_t a, uint32_t b) {
- return a - b;
+static void handle_out_of_order(struct utcp_connection *c, uint32_t offset, const void *data, size_t len) {
+ debug("out of order packet, offset %u\n", offset);
+ // Packet loss or reordering occured. Store the data in the buffer.
+ ssize_t rxd = buffer_put_at(&c->rcvbuf, offset, data, len);
+ if(rxd < len)
+ abort();
+
+ // Make note of where we put it.
+ for(int i = 0; i < NSACKS; i++) {
+ if(!c->sacks[i].len) { // nothing to merge, add new entry
+ debug("New SACK entry %d\n", i);
+ c->sacks[i].offset = offset;
+ c->sacks[i].len = rxd;
+ break;
+ } else if(offset < c->sacks[i].offset) {
+ if(offset + rxd < c->sacks[i].offset) { // insert before
+ if(!c->sacks[NSACKS - 1].len) { // only if room left
+ debug("Insert SACK entry at %d\n", i);
+ memmove(&c->sacks[i + 1], &c->sacks[i], (NSACKS - i - 1) * sizeof c->sacks[i]);
+ c->sacks[i].offset = offset;
+ c->sacks[i].len = rxd;
+ }
+ break;
+ } else { // merge
+ debug("Merge with start of SACK entry at %d\n", i);
+ c->sacks[i].offset = offset;
+ break;
+ }
+ } else if(offset <= c->sacks[i].offset + c->sacks[i].len) {
+ if(offset + rxd > c->sacks[i].offset + c->sacks[i].len) { // merge
+ debug("Merge with end of SACK entry at %d\n", i);
+ c->sacks[i].len = offset + rxd - c->sacks[i].offset;
+ // TODO: handle potential merge with next entry
+ }
+ break;
+ }
+ }
+
+ for(int i = 0; i < NSACKS && c->sacks[i].len; i++)
+ debug("SACK[%d] offset %u len %u\n", i, c->sacks[i].offset, c->sacks[i].len);
+}
+
+static void handle_in_order(struct utcp_connection *c, const void *data, size_t len) {
+ // Check if we can process out-of-order data now.
+ if(c->sacks[0].len && len >= c->sacks[0].offset) { // TODO: handle overlap with second SACK
+ debug("incoming packet len %zu connected with SACK at %u\n", len, c->sacks[0].offset);
+ buffer_put_at(&c->rcvbuf, 0, data, len); // TODO: handle return value
+ len = max(len, c->sacks[0].offset + c->sacks[0].len);
+ data = c->rcvbuf.data;
+ }
+
+ if(c->recv) {
+ ssize_t rxd = c->recv(c, data, len);
+ if(rxd != len) {
+ // TODO: handle the application not accepting all data.
+ abort();
+ }
+ }
+
+ if(c->rcvbuf.used)
+ sack_consume(c, len);
+
+ c->rcv.nxt += len;
+}
+
+
+static void handle_incoming_data(struct utcp_connection *c, uint32_t seq, const void *data, size_t len) {
+ uint32_t offset = seqdiff(seq, c->rcv.nxt);
+ if(offset + len > c->rcvbuf.maxsize)
+ abort();
+
+ if(offset)
+ handle_out_of_order(c, offset, data, len);
+ else
+ handle_in_order(c, data, len);
}
-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;
return 0;
}
- fprintf(stderr, "%p state %s\n", c->utcp, strstate[c->state]);
+ debug("%p state %s\n", c->utcp, strstate[c->state]);
// In case this is for a CLOSED connection, ignore the packet.
// TODO: make it so incoming packets can never match a CLOSED connection.
// 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.
case TIME_WAIT:
break;
default:
+#ifdef UTCP_DEBUG
abort();
+#endif
+ break;
}
// 1b. Drop packets with a sequence number not in our receive window.
acceptable = true;
// TODO: handle packets overlapping c->rcv.nxt.
-#if 0
+#if 1
// 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 = (seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt + c->rcv.wnd) < 0);
+ acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0;
else
- if(c->rcv.wnd == 0)
- // We don't accept data when the receive window is zero.
- acceptable = false;
- else
- // 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);
+ acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt) + len <= c->rcvbuf.maxsize;
#else
if(c->state != SYN_SENT)
acceptable = hdr.seq == c->rcv.nxt;
#endif
if(!acceptable) {
- fprintf(stderr, "Packet not acceptable, %u <= %u + %zu < %u\n", c->rcv.nxt, hdr.seq, len, c->rcv.nxt + c->rcv.wnd);
+ debug("Packet not acceptable, %u <= %u + %zu < %u\n", c->rcv.nxt, hdr.seq, len, c->rcv.nxt + c->rcvbuf.maxsize);
// Ignore unacceptable RST packets.
if(hdr.ctl & RST)
return 0;
// Otherwise, send an ACK back in the hope things improve.
- goto ack;
+ ack(c, true);
+ return 0;
}
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)) {
- fprintf(stderr, "Packet ack seqno out of range, %u %u %u\n", hdr.ack, c->snd.una, c->snd.nxt);
+ // 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(hdr.ctl & ACK &&
+ ((seqdiff(hdr.ack, c->snd.una + c->sndbuf.used) > 0 &&
+ seqdiff(hdr.ack, c->snd.nxt) > 0) // TODO: simplify this if
+ || 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);
// Ignore unacceptable RST packets.
if(hdr.ctl & RST)
return 0;
set_state(c, CLOSED);
return 0;
default:
+#ifdef UTCP_DEBUG
abort();
+#endif
+ break;
}
}
// 3. Advance snd.una
uint32_t advanced = seqdiff(hdr.ack, c->snd.una);
- c->snd.una = hdr.ack;
+ prevrcvnxt = c->rcv.nxt;
if(advanced) {
- fprintf(stderr, "%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);
+ 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);
+
+ if(data_acked)
+ buffer_get(&c->sndbuf, NULL, data_acked);
+
+ // Also advance snd.nxt if possible
+ if(seqdiff(c->snd.nxt, hdr.ack) < 0)
+ c->snd.nxt = hdr.ack;
+
+ c->snd.una = hdr.ack;
+
+ c->dupack = 0;
+ c->snd.cwnd += utcp->mtu;
+ if(c->snd.cwnd > c->sndbuf.maxsize)
+ c->snd.cwnd = c->sndbuf.maxsize;
+
+ // 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:
+ break;
+ }
+ } else {
+ if(!len) {
+ c->dupack++;
+ if(c->dupack == 3) {
+ debug("Triplicate ACK\n");
+ //TODO: Resend one packet and go to fast recovery mode. See RFC 6582.
+ //We do a very simple variant here; reset the nxt pointer to the last acknowledged packet from the peer.
+ //Reset the congestion window so we wait for ACKs.
+ c->snd.nxt = c->snd.una;
+ c->snd.cwnd = utcp->mtu;
+ }
+ }
}
// 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);
}
// Ehm, no. We should never receive a second SYN.
goto reset;
default:
+#ifdef UTCP_DEBUG
abort();
+#endif
+ return 0;
}
// SYN counts as one sequence number
case SYN_SENT:
case SYN_RECEIVED:
// This should never happen.
+#ifdef UTCP_DEBUG
abort();
+#endif
+ return 0;
case ESTABLISHED:
case FIN_WAIT_1:
case FIN_WAIT_2:
// Ehm no, We should never receive more data after a FIN.
goto reset;
default:
+#ifdef UTCP_DEBUG
abort();
+#endif
+ return 0;
}
- int rxd;
-
- 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;
+ handle_incoming_data(c, hdr.seq, data, len);
}
// 7. Process FIN stuff
- if(hdr.ctl & FIN) {
+ if((hdr.ctl & FIN) && hdr.seq + len == c->rcv.nxt) {
switch(c->state) {
case SYN_SENT:
case SYN_RECEIVED:
// This should never happen.
+#ifdef UTCP_DEBUG
abort();
+#endif
+ break;
case ESTABLISHED:
set_state(c, CLOSE_WAIT);
break;
set_state(c, CLOSING);
break;
case FIN_WAIT_2:
+ gettimeofday(&c->conn_timeout, NULL);
+ c->conn_timeout.tv_sec += 60;
set_state(c, TIME_WAIT);
break;
case CLOSE_WAIT:
// Ehm, no. We should never receive a second FIN.
goto reset;
default:
+#ifdef UTCP_DEBUG
abort();
+#endif
+ break;
}
// FIN counts as one sequence number
c->rcv.nxt++;
+ len++;
// Inform the application that the peer closed the connection.
if(c->recv) {
}
}
- 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:
- 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, prevrcvnxt != c->rcv.nxt);
return 0;
reset:
}
int utcp_shutdown(struct utcp_connection *c, int dir) {
- fprintf(stderr, "%p shutdown %d\n", c->utcp, dir);
+ debug("%p shutdown %d at %u\n", c ? c->utcp : NULL, dir, c ? c->snd.last : 0);
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;
}
- // TODO: handle dir
+ if(!(dir == UTCP_SHUT_RD || dir == UTCP_SHUT_WR || dir == UTCP_SHUT_RDWR)) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ // TCP does not have a provision for stopping incoming packets.
+ // The best we can do is to just ignore them.
+ if(dir == UTCP_SHUT_RD || dir == UTCP_SHUT_RDWR)
+ c->recv = NULL;
+
+ // The rest of the code deals with shutting down writes.
+ if(dir == UTCP_SHUT_RD)
+ return 0;
switch(c->state) {
case CLOSED:
- return 0;
case LISTEN:
+ errno = ENOTCONN;
+ return -1;
+
case SYN_SENT:
set_state(c, CLOSED);
return 0;
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.last++;
- c->snd.nxt += 1;
-
- print_packet(c->utcp, "send", &hdr, sizeof hdr);
- c->utcp->send(c->utcp, &hdr, sizeof hdr);
+ ack(c, false);
return 0;
}
int utcp_close(struct utcp_connection *c) {
if(utcp_shutdown(c, SHUT_RDWR))
return -1;
+ c->recv = NULL;
+ c->poll = NULL;
c->reapable = true;
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;
}
+ c->recv = NULL;
+ c->poll = NULL;
c->reapable = true;
switch(c->state) {
return 0;
}
-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:
- 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(len > utcp->mtu)
- len = utcp->mtu;
- 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 utcp_timeout(struct utcp *utcp) {
struct timeval now;
gettimeofday(&now, NULL);
struct timeval next = {now.tv_sec + 3600, now.tv_usec};
if(c->state == CLOSED) {
if(c->reapable) {
- fprintf(stderr, "Reaping %p\n", c);
+ debug("Reaping %p\n", c);
free_connection(c);
i--;
}
retransmit(c);
}
+ if(c->poll && buffer_free(&c->sndbuf) && (c->state == ESTABLISHED || c->state == CLOSE_WAIT))
+ c->poll(c, buffer_free(&c->sndbuf));
+
if(timerisset(&c->conn_timeout) && timercmp(&c->conn_timeout, &next, <))
next = c->conn_timeout;
struct timeval diff;
timersub(&next, &now, &diff);
- if(diff.tv_sec < 0)
- return 0;
- return diff.tv_sec * 1000 + diff.tv_usec / 1000;
+ return diff;
}
-struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_send_t send, void *priv) {
- struct utcp *utcp = calloc(1, sizeof *utcp);
+bool utcp_is_active(struct utcp *utcp) {
if(!utcp)
- return NULL;
+ return false;
+
+ for(int i = 0; i < utcp->nconnections; i++)
+ if(utcp->connections[i]->state != CLOSED && utcp->connections[i]->state != TIME_WAIT)
+ return true;
+
+ return false;
+}
+struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_send_t send, void *priv) {
if(!send) {
errno = EFAULT;
return NULL;
}
+ struct utcp *utcp = calloc(1, sizeof *utcp);
+ if(!utcp)
+ return NULL;
+
utcp->accept = accept;
utcp->pre_accept = pre_accept;
utcp->send = send;
utcp->priv = priv;
- utcp->mtu = 1000;
- utcp->timeout = 60;
+ utcp->mtu = DEFAULT_MTU;
+ utcp->timeout = DEFAULT_USER_TIMEOUT; // s
return utcp;
}
void utcp_exit(struct utcp *utcp) {
if(!utcp)
return;
- for(int i = 0; i < utcp->nconnections; i++)
- free_connection(utcp->connections[i]);
+ for(int i = 0; i < utcp->nconnections; i++) {
+ if(!utcp->connections[i]->reapable)
+ debug("Warning, freeing unclosed connection %p\n", utcp->connections[i]);
+ buffer_exit(&utcp->connections[i]->sndbuf);
+ free(utcp->connections[i]);
+ }
+ free(utcp->connections);
free(utcp);
}
-int utcp_set_connection_timeout(struct utcp *u, int timeout) {
- int prev = u->timeout;
- u->timeout = timeout;
- return prev;
+uint16_t utcp_get_mtu(struct utcp *utcp) {
+ return utcp ? utcp->mtu : 0;
+}
+
+void utcp_set_mtu(struct utcp *utcp, uint16_t mtu) {
+ // TODO: handle overhead of the header
+ if(utcp)
+ utcp->mtu = mtu;
+}
+
+int utcp_get_user_timeout(struct utcp *u) {
+ return u ? u->timeout : 0;
+}
+
+void utcp_set_user_timeout(struct utcp *u, int timeout) {
+ if(u)
+ u->timeout = timeout;
+}
+
+size_t utcp_get_sndbuf(struct utcp_connection *c) {
+ return c ? c->sndbuf.maxsize : 0;
+}
+
+size_t utcp_get_sndbuf_free(struct utcp_connection *c) {
+ if(c && (c->state == ESTABLISHED || c->state == CLOSE_WAIT))
+ return buffer_free(&c->sndbuf);
+ else
+ return 0;
+}
+
+void utcp_set_sndbuf(struct utcp_connection *c, size_t size) {
+ if(!c)
+ return;
+ c->sndbuf.maxsize = size;
+ if(c->sndbuf.maxsize != size)
+ c->sndbuf.maxsize = -1;
+}
+
+size_t utcp_get_rcvbuf(struct utcp_connection *c) {
+ return c ? c->rcvbuf.maxsize : 0;
+}
+
+size_t utcp_get_rcvbuf_free(struct utcp_connection *c) {
+ if(c && (c->state == ESTABLISHED || c->state == CLOSE_WAIT))
+ return buffer_free(&c->rcvbuf);
+ else
+ return 0;
+}
+
+void utcp_set_rcvbuf(struct utcp_connection *c, size_t size) {
+ if(!c)
+ return;
+ c->rcvbuf.maxsize = size;
+ if(c->rcvbuf.maxsize != size)
+ c->rcvbuf.maxsize = -1;
+}
+
+bool utcp_get_nodelay(struct utcp_connection *c) {
+ return c ? c->nodelay : false;
+}
+
+void utcp_set_nodelay(struct utcp_connection *c, bool nodelay) {
+ if(c)
+ c->nodelay = nodelay;
+}
+
+bool utcp_get_keepalive(struct utcp_connection *c) {
+ return c ? c->keepalive : false;
+}
+
+void utcp_set_keepalive(struct utcp_connection *c, bool keepalive) {
+ if(c)
+ c->keepalive = keepalive;
+}
+
+size_t utcp_get_outq(struct utcp_connection *c) {
+ return c ? seqdiff(c->snd.nxt, c->snd.una) : 0;
+}
+
+void utcp_set_recv_cb(struct utcp_connection *c, utcp_recv_t recv) {
+ if(c)
+ c->recv = recv;
+}
+
+void utcp_set_poll_cb(struct utcp_connection *c, utcp_poll_t poll) {
+ if(c)
+ c->poll = poll;
+}
+
+void utcp_set_accept_cb(struct utcp *utcp, utcp_accept_t accept, utcp_pre_accept_t pre_accept) {
+ if(utcp) {
+ utcp->accept = accept;
+ utcp->pre_accept = pre_accept;
+ }
}
projects / utcp / blobdiff