/*
utcp.c -- Userspace TCP
- Copyright (C) 2014 Guus Sliepen <guus@tinc-vpn.org>
+ Copyright (C) 2014-2017 Guus Sliepen <guus@tinc-vpn.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#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 up;
- uint32_t wl1;
- uint32_t wl2;
- uint32_t iss;
- } snd;
+#ifndef EBADMSG
+#define EBADMSG 104
+#endif
- struct {
- uint32_t nxt;
- uint32_t wnd;
- uint32_t up;
- uint32_t irs;
- } rcv;
+#ifndef SHUT_RDWR
+#define SHUT_RDWR 2
+#endif
+
+#ifdef poll
+#undef poll
+#endif
+
+#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 += USEC_PER_SEC;\
+ } while (0)
+#endif
+
+static inline size_t max(size_t a, size_t b) {
+ return a > b ? a : b;
+}
+
+#ifdef UTCP_DEBUG
+#include <stdarg.h>
+
+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)) {
+ debug("%p %s: short packet (%lu bytes)\n", utcp, dir, (unsigned long)len);
+ return;
+ }
+
+ memcpy(&hdr, pkt, sizeof(hdr));
+ debug("%p %s: len=%lu, src=%u dst=%u seq=%u ack=%u wnd=%u aux=%x ctl=", utcp, dir, (unsigned long)len, hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd, hdr.aux);
- utcp_recv_t recv;
+ if(hdr.ctl & SYN) {
+ debug("SYN");
+ }
+
+ if(hdr.ctl & RST) {
+ debug("RST");
+ }
+
+ if(hdr.ctl & FIN) {
+ debug("FIN");
+ }
- struct timeval conn_timeout;
- struct timeval rtrx_timeout;
+ if(hdr.ctl & ACK) {
+ debug("ACK");
+ }
- char *sndbuf;
- uint32_t sndbufsize;
-};
+ if(len > sizeof(hdr)) {
+ uint32_t datalen = len - sizeof(hdr);
+ const uint8_t *data = (uint8_t *)pkt + sizeof(hdr);
+ char str[datalen * 2 + 1];
+ char *p = str;
-struct utcp {
- void *priv;
+ for(uint32_t i = 0; i < datalen; i++) {
+ *p++ = "0123456789ABCDEF"[data[i] >> 4];
+ *p++ = "0123456789ABCDEF"[data[i] & 15];
+ }
- utcp_accept_t accept;
- utcp_pre_accept_t pre_accept;
- utcp_send_t send;
+ *p = 0;
- uint16_t mtu;
- int timeout;
+ debug(" data=%s", str);
+ }
- struct utcp_connection **connections;
- int nconnections;
- int nallocated;
-};
+ debug("\n");
+}
+#else
+#define debug(...) do {} while(0)
+#define print_packet(...) do {} while(0)
+#endif
static void set_state(struct utcp_connection *c, enum state state) {
c->state = state;
- if(state == ESTABLISHED)
+
+ if(state == ESTABLISHED) {
timerclear(&c->conn_timeout);
- fprintf(stderr, "%p new state: %s\n", c->utcp, strstate[state]);
+ }
+
+ debug("%p new state: %s\n", c->utcp, strstate[state]);
}
-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);
- return;
+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 bool is_reliable(struct utcp_connection *c) {
+ return c->flags & UTCP_RELIABLE;
+}
+
+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) {
+ debug("buffer_put_at %lu %lu %lu\n", (unsigned long)buf->used, (unsigned long)offset, (unsigned long)len);
+
+ size_t required = offset + len;
+
+ if(required > buf->maxsize) {
+ if(offset >= buf->maxsize) {
+ return 0;
+ }
+
+ 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 < required);
+ }
+
+ 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(&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);
- if(hdr.ctl & SYN)
- fprintf(stderr, "SYN");
- if(hdr.ctl & RST)
- fprintf(stderr, "RST");
- if(hdr.ctl & FIN)
- fprintf(stderr, "FIN");
- if(hdr.ctl & ACK)
- fprintf(stderr, "ACK");
+ 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 > sizeof hdr) {
- fprintf(stderr, " data=");
- for(int i = sizeof hdr; i < len; i++) {
- const char *data = pkt;
- fprintf(stderr, "%c", data[i] >= 32 ? data[i] : '.');
+ if(len) {
+ buf->data = malloc(len);
+
+ if(!buf->data) {
+ return false;
}
}
- fprintf(stderr, "\n");
+ buf->size = len;
+ buf->maxsize = maxlen;
+ return true;
}
-static inline void list_connections(struct utcp *utcp) {
- fprintf(stderr, "%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]);
+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)
+
+ if(c) {
return c;
+ }
+
c = (int)a->dst - (int)b->dst;
return c;
}
static struct utcp_connection *find_connection(const struct utcp *utcp, uint16_t src, uint16_t dst) {
- if(!utcp->nconnections)
+ if(!utcp->nconnections) {
return NULL;
+ }
+
struct utcp_connection key = {
.src = src,
.dst = dst,
}, *keyp = &key;
- struct utcp_connection **match = bsearch(&keyp, utcp->connections, utcp->nconnections, sizeof *utcp->connections, compare);
+ struct utcp_connection **match = bsearch(&keyp, utcp->connections, utcp->nconnections, sizeof(*utcp->connections), compare);
return match ? *match : NULL;
}
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();
+ struct utcp_connection **cp = bsearch(&c, utcp->connections, utcp->nconnections, sizeof(*utcp->connections), compare);
+
+ 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->rcvbuf);
+ buffer_exit(&c->sndbuf);
free(c);
}
errno = ENOMEM;
return NULL;
}
+
src = rand() | 0x8000;
- while(find_connection(utcp, src, dst))
+
+ while(find_connection(utcp, src, dst)) {
src++;
+ }
}
// Allocate memory for the new connection
if(utcp->nconnections >= utcp->nallocated) {
- if(!utcp->nallocated)
+ if(!utcp->nallocated) {
utcp->nallocated = 4;
- else
+ } else {
utcp->nallocated *= 2;
- struct utcp_connection **new_array = realloc(utcp->connections, utcp->nallocated * sizeof *utcp->connections);
+ }
+
+ struct utcp_connection **new_array = realloc(utcp->connections, utcp->nallocated * sizeof(*utcp->connections));
+
if(!new_array) {
- errno = ENOMEM;
return NULL;
}
+
utcp->connections = new_array;
}
- struct utcp_connection *c = calloc(1, sizeof *c);
+ struct utcp_connection *c = calloc(1, sizeof(*c));
+
if(!c) {
- errno = ENOMEM;
+ return NULL;
+ }
+
+ if(!buffer_init(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
+ free(c);
+ return NULL;
+ }
+
+ if(!buffer_init(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
+ buffer_exit(&c->sndbuf);
+ 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
utcp->connections[utcp->nconnections++] = c;
- qsort(utcp->connections, utcp->nconnections, sizeof *utcp->connections, compare);
+ qsort(utcp->connections, utcp->nconnections, sizeof(*utcp->connections), compare);
return c;
}
-struct utcp_connection *utcp_connect(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv) {
+static inline uint32_t absdiff(uint32_t a, uint32_t b) {
+ if(a > b) {
+ return a - b;
+ } else {
+ return b - a;
+ }
+}
+
+// Update RTT variables. See RFC 6298.
+static void update_rtt(struct utcp_connection *c, uint32_t rtt) {
+ if(!rtt) {
+ debug("invalid rtt\n");
+ return;
+ }
+
+ struct utcp *utcp = c->utcp;
+
+ 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);
+ }
+
+ if(utcp->rto > MAX_RTO) {
+ utcp->rto = MAX_RTO;
+ }
+
+ debug("rtt %u srtt %u rttvar %u rto %u\n", rtt, utcp->srtt, utcp->rttvar, utcp->rto);
+}
+
+static void start_retransmit_timer(struct utcp_connection *c) {
+ gettimeofday(&c->rtrx_timeout, NULL);
+ c->rtrx_timeout.tv_usec += c->utcp->rto;
+
+ while(c->rtrx_timeout.tv_usec >= 1000000) {
+ c->rtrx_timeout.tv_usec -= 1000000;
+ c->rtrx_timeout.tv_sec++;
+ }
+
+ debug("timeout set to %lu.%06lu (%u)\n", c->rtrx_timeout.tv_sec, c->rtrx_timeout.tv_usec, c->utcp->rto);
+}
+
+static void stop_retransmit_timer(struct utcp_connection *c) {
+ timerclear(&c->rtrx_timeout);
+ debug("timeout cleared\n");
+}
+
+struct utcp_connection *utcp_connect_ex(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv, uint32_t flags) {
struct utcp_connection *c = allocate_connection(utcp, 0, dst);
- if(!c)
+
+ if(!c) {
return NULL;
+ }
+ assert((flags & ~0xf) == 0);
+
+ c->flags = flags;
c->recv = recv;
+ c->priv = priv;
- struct hdr hdr;
+ struct {
+ struct hdr hdr;
+ uint8_t init[4];
+ } pkt;
- hdr.src = c->src;
- hdr.dst = c->dst;
- hdr.seq = c->snd.iss;
- hdr.ack = 0;
- hdr.ctl = SYN;
- hdr.wnd = c->rcv.wnd;
+ pkt.hdr.src = c->src;
+ pkt.hdr.dst = c->dst;
+ pkt.hdr.seq = c->snd.iss;
+ pkt.hdr.ack = 0;
+ pkt.hdr.wnd = c->rcv.wnd;
+ pkt.hdr.ctl = SYN;
+ pkt.hdr.aux = 0x0101;
+ pkt.init[0] = 1;
+ pkt.init[1] = 0;
+ pkt.init[2] = 0;
+ pkt.init[3] = flags & 0x7;
set_state(c, SYN_SENT);
- print_packet(utcp, "send", &hdr, sizeof hdr);
- utcp->send(utcp, &hdr, sizeof hdr);
+ print_packet(utcp, "send", &pkt, sizeof(pkt));
+ utcp->send(utcp, &pkt, sizeof(pkt));
gettimeofday(&c->conn_timeout, NULL);
c->conn_timeout.tv_sec += utcp->timeout;
+ start_retransmit_timer(c);
+
return c;
}
+struct utcp_connection *utcp_connect(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv) {
+ return utcp_connect_ex(utcp, dst, recv, priv, UTCP_TCP);
+}
+
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;
+ uint8_t 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;
+ }
+
+ if(!c->rtt_start.tv_sec) {
+ // Start RTT measurement
+ gettimeofday(&c->rtt_start, NULL);
+ c->rtt_seq = pkt->hdr.seq + seglen;
+ debug("Starting RTT measurement, expecting ack %u\n", c->rtt_seq);
+ }
+
+ 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;
}
switch(c->state) {
case CLOSED:
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 SYN_SENT:
+ case SYN_RECEIVED:
case ESTABLISHED:
case CLOSE_WAIT:
break;
+
case FIN_WAIT_1:
case FIN_WAIT_2:
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
+ // Exit early if we have nothing to send.
- if(!len)
+ if(!len) {
return 0;
+ }
if(!data) {
errno = EFAULT;
return -1;
}
- uint32_t bufused = c->snd.nxt - c->snd.una;
+ // Add data to send buffer.
- if(len > c->sndbufsize - bufused)
- len = c->sndbufsize - bufused;
+ len = buffer_put(&c->sndbuf, data, len);
- memcpy(c->sndbuf + (c->snd.nxt - c->snd.una), data, len);
-
- // Send segments
-
- struct {
- struct hdr hdr;
- char data[c->utcp->mtu];
- } pkt;
+ if(len <= 0) {
+ errno = EWOULDBLOCK;
+ return 0;
+ }
- 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;
+ c->snd.last += len;
- uint32_t left = len;
+ // Don't send anything yet if the connection has not fully established yet
- while(left) {
- uint32_t seglen = left > c->utcp->mtu ? c->utcp->mtu : left;
- pkt.hdr.seq = c->snd.nxt;
+ if(c->state == SYN_SENT || c->state == SYN_RECEIVED) {
+ return len;
+ }
- memcpy(pkt.data, data, seglen);
+ ack(c, false);
- c->snd.nxt += seglen;
- data += seglen;
- left -= seglen;
+ if(!is_reliable(c)) {
+ c->snd.una = c->snd.nxt = c->snd.last;
+ buffer_get(&c->sndbuf, NULL, c->sndbuf.used);
+ }
- print_packet(c->utcp, "send", &pkt, sizeof pkt.hdr + seglen);
- c->utcp->send(c->utcp, &pkt, sizeof pkt.hdr + seglen);
+ if(is_reliable(c) && !timerisset(&c->rtrx_timeout)) {
+ start_retransmit_timer(c);
}
- fprintf(stderr, "len=%zu\n", len);
return len;
}
hdr->dst = tmp;
}
-static int32_t seqdiff(uint32_t a, uint32_t b) {
- return a - b;
-}
-
-int utcp_recv(struct utcp *utcp, const void *data, size_t len) {
- if(!utcp) {
- errno = EFAULT;
- return -1;
+static void retransmit(struct utcp_connection *c) {
+ if(c->state == CLOSED || c->snd.last == c->snd.una) {
+ debug("Retransmit() called but nothing to retransmit!\n");
+ stop_retransmit_timer(c);
+ return;
}
- if(!len)
- return 0;
+ struct utcp *utcp = c->utcp;
- if(!data) {
- errno = EFAULT;
- return -1;
- }
+ struct {
+ struct hdr hdr;
+ uint8_t data[];
+ } *pkt;
- print_packet(utcp, "recv", data, len);
+ pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
- struct hdr hdr;
- if(len < sizeof hdr) {
- errno = EBADMSG;
- return -1;
+ if(!pkt) {
+ return;
}
- memcpy(&hdr, data, sizeof hdr);
- data += sizeof hdr;
- len -= sizeof hdr;
+ pkt->hdr.src = c->src;
+ pkt->hdr.dst = c->dst;
+ pkt->hdr.wnd = c->rcv.wnd;
+ pkt->hdr.aux = 0;
- if(hdr.ctl & ~(SYN | ACK | RST | FIN)) {
- errno = EBADMSG;
- return -1;
- }
+ switch(c->state) {
+ case SYN_SENT:
+ // Send our SYN again
+ pkt->hdr.seq = c->snd.iss;
+ pkt->hdr.ack = 0;
+ pkt->hdr.ctl = SYN;
+ pkt->hdr.aux = 0x0101;
+ pkt->data[0] = 1;
+ pkt->data[1] = 0;
+ pkt->data[2] = 0;
+ pkt->data[3] = c->flags & 0x7;
+ print_packet(c->utcp, "rtrx", pkt, sizeof(pkt->hdr) + 4);
+ utcp->send(utcp, pkt, sizeof(pkt->hdr) + 4);
+ break;
- //list_connections(utcp);
+ 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;
- struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
+ 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;
+
+ 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
+ stop_retransmit_timer(c);
+ goto cleanup;
+ }
+
+ start_retransmit_timer(c);
+ utcp->rto *= 2;
+
+ if(utcp->rto > MAX_RTO) {
+ utcp->rto = MAX_RTO;
+ }
+
+ c->rtt_start.tv_sec = 0; // invalidate RTT timer
+
+cleanup:
+ free(pkt);
+}
+
+/* Update receive buffer and SACK entries after consuming data.
+ *
+ * Situation:
+ *
+ * |.....0000..1111111111.....22222......3333|
+ * |---------------^
+ *
+ * 0..3 represent the SACK entries. The ^ indicates up to which point we want
+ * to remove data from the receive buffer. The idea is to substract "len"
+ * from the offset of all the SACK entries, and then remove/cut down entries
+ * that are shifted to before the start of the receive buffer.
+ *
+ * There are three cases:
+ * - the SACK entry is after ^, in that case just change the offset.
+ * - the SACK entry starts before and ends after ^, so we have to
+ * change both its offset and size.
+ * - the SACK entry is completely before ^, in that case delete it.
+ */
+static void sack_consume(struct utcp_connection *c, size_t len) {
+ debug("sack_consume %lu\n", (unsigned long)len);
+
+ if(len > c->rcvbuf.used) {
+ debug("All SACK entries consumed");
+ c->sacks[0].len = 0;
+ return;
+ }
+
+ 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].len -= len - c->sacks[i].offset;
+ c->sacks[i].offset = 0;
+ i++;
+ } else {
+ if(i < NSACKS - 1) {
+ memmove(&c->sacks[i], &c->sacks[i + 1], (NSACKS - 1 - i) * sizeof(c->sacks)[i]);
+ c->sacks[NSACKS - 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 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 < 0 || (size_t)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;
+ } else {
+ debug("SACK entries full, dropping packet\n");
+ }
+
+ 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 %lu connected with SACK at %u\n", (unsigned long)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 < 0 || (size_t)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) {
+ if(!is_reliable(c)) {
+ c->recv(c, data, len);
+ c->rcv.nxt = seq + len;
+ return;
+ }
+
+ 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);
+ }
+}
+
+
+ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
+ const uint8_t *ptr = data;
+
+ if(!utcp) {
+ errno = EFAULT;
+ return -1;
+ }
+
+ if(!len) {
+ return 0;
+ }
+
+ if(!data) {
+ errno = EFAULT;
+ return -1;
+ }
+
+ print_packet(utcp, "recv", data, len);
+
+ // Drop packets smaller than the header
+
+ struct hdr hdr;
+
+ if(len < sizeof(hdr)) {
+ errno = EBADMSG;
+ return -1;
+ }
+
+ // Make a copy from the potentially unaligned data to a struct hdr
+
+ memcpy(&hdr, ptr, sizeof(hdr));
+ ptr += sizeof(hdr);
+ len -= sizeof(hdr);
+
+ // Drop packets with an unknown CTL flag
+
+ if(hdr.ctl & ~(SYN | ACK | RST | FIN)) {
+ errno = EBADMSG;
+ return -1;
+ }
+
+ // Check for auxiliary headers
+
+ const uint8_t *init = NULL;
+
+ uint16_t aux = hdr.aux;
+
+ while(aux) {
+ size_t auxlen = 4 * (aux >> 8) & 0xf;
+ uint8_t auxtype = aux & 0xff;
+
+ if(len < auxlen) {
+ errno = EBADMSG;
+ return -1;
+ }
+
+ switch(auxtype) {
+ case AUX_INIT:
+ if(!(hdr.ctl & SYN) || auxlen != 4) {
+ errno = EBADMSG;
+ return -1;
+ }
+
+ init = ptr;
+ break;
+
+ default:
+ errno = EBADMSG;
+ return -1;
+ }
+
+ len -= auxlen;
+ ptr += auxlen;
+
+ if(!(aux & 0x800)) {
+ break;
+ }
+
+ if(len < 2) {
+ errno = EBADMSG;
+ return -1;
+ }
+
+ memcpy(&aux, ptr, 2);
+ len -= 2;
+ ptr += 2;
+ }
+
+ // 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) {
- if(hdr.ctl & RST)
+ // Ignore RST packets
+
+ if(hdr.ctl & RST) {
return 0;
+ }
+
+ // Is it a SYN packet and are we LISTENing?
- 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
+ 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;
+ }
+
+ // Parse auxilliary information
+ if(init) {
+ if(init[0] < 1) {
+ len = 1;
+ goto reset;
+ }
+
+ c->flags = init[3] & 0x7;
+ } else {
+ c->flags = UTCP_TCP;
+ }
+
+ // 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;
set_state(c, SYN_RECEIVED);
- hdr.dst = c->dst;
- hdr.src = c->src;
- 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
+ struct {
+ struct hdr hdr;
+ uint8_t data[4];
+ } pkt;
+
+ pkt.hdr.src = c->src;
+ pkt.hdr.dst = c->dst;
+ pkt.hdr.ack = c->rcv.irs + 1;
+ pkt.hdr.seq = c->snd.iss;
+ pkt.hdr.wnd = c->rcv.wnd;
+ pkt.hdr.ctl = SYN | ACK;
+
+ if(init) {
+ pkt.hdr.aux = 0x0101;
+ pkt.data[0] = 1;
+ pkt.data[1] = 0;
+ pkt.data[2] = 0;
+ pkt.data[3] = c->flags & 0x7;
+ print_packet(c->utcp, "send", &pkt, sizeof(hdr) + 4);
+ utcp->send(utcp, &pkt, sizeof(hdr) + 4);
+ } else {
+ pkt.hdr.aux = 0;
+ print_packet(c->utcp, "send", &pkt, sizeof(hdr));
+ utcp->send(utcp, &pkt, sizeof(hdr));
+ }
+ } 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]);
+
+ // 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) {
- fprintf(stderr, "Error: packet recv()d on closed connection %p\n", c);
- errno = EBADF;
- return -1;
+ debug("Got packet for closed connection\n");
+ return 0;
}
// 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.
+
+ 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:
+#ifdef UTCP_DEBUG
+ abort();
+#endif
+ break;
+ }
+
+ // 1b. Drop packets with a sequence number not in our receive window.
+
+ bool acceptable;
+
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;
+ 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;
+
+ 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;
}
+ }
+
+ 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) {
- if(!(hdr.ctl & ACK))
- return 0;
- set_state(c, CLOSED);
- errno = ECONNREFUSED;
- if(c->recv)
- 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;
- }
- print_packet(c->utcp, "send", &hdr, sizeof hdr);
- utcp->send(utcp, &hdr, sizeof hdr);
- // TODO: queue any data?
- }
- return 0;
+ // Otherwise, continue processing.
+ len = 0;
}
- bool acceptable;
+ c->snd.wnd = hdr.wnd; // TODO: move below
- 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);
- else
- if(c->rcv.wnd == 0)
- 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);
+ // 1c. Drop packets with an invalid ACK.
+ // 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(!acceptable) {
- fprintf(stderr, "Packet not acceptable, %u %u %u %zu\n", hdr.seq, c->rcv.nxt, c->rcv.wnd, len);
- if(hdr.ctl & RST)
+ 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);
+
+ // Ignore unacceptable RST packets.
+ if(hdr.ctl & RST) {
return 0;
- goto ack_and_drop;
- }
+ }
- c->snd.wnd = hdr.wnd;
+ goto reset;
+ }
- // TODO: check whether segment really starts at rcv.nxt, otherwise trim it.
+ // 2. Handle RST packets
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;
- if(c->recv)
+
+ if(c->recv) {
c->recv(c, NULL, 0);
- break;
+ }
+
+ 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:
+#ifdef UTCP_DEBUG
+ abort();
+#endif
break;
+ }
+ }
+
+ uint32_t advanced;
+
+ if(!(hdr.ctl & ACK)) {
+ advanced = 0;
+ goto skip_ack;
+ }
+
+ // 3. Advance snd.una
+
+ advanced = seqdiff(hdr.ack, c->snd.una);
+ prevrcvnxt = c->rcv.nxt;
+
+ if(advanced) {
+ // RTT measurement
+ if(c->rtt_start.tv_sec) {
+ if(c->rtt_seq == hdr.ack) {
+ struct timeval now, diff;
+ gettimeofday(&now, NULL);
+ timersub(&now, &c->rtt_start, &diff);
+ update_rtt(c, diff.tv_sec * 1000000 + diff.tv_usec);
+ c->rtt_start.tv_sec = 0;
+ } else if(c->rtt_seq < hdr.ack) {
+ debug("Cancelling RTT measurement: %u < %u\n", c->rtt_seq, hdr.ack);
+ c->rtt_start.tv_sec = 0;
+ }
+ }
+
+ int32_t data_acked = advanced;
+
+ switch(c->state) {
+ case SYN_SENT:
+ case SYN_RECEIVED:
+ data_acked--;
+ break;
+
+ // TODO: handle FIN as well.
default:
- // TODO: wtf?
- return 0;
+ 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 && is_reliable(c)) {
+ 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;
+ start_retransmit_timer(c);
+ }
+ }
+ }
+
+ // 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);
+ } else if(is_reliable(c)) {
+ start_retransmit_timer(c);
}
- set_state(c, CLOSED);
- return 0;
}
+skip_ack:
+ // 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;
+
+ 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:
case ESTABLISHED:
case FIN_WAIT_1:
case CLOSING:
case LAST_ACK:
case TIME_WAIT:
- set_state(c, CLOSED);
- errno = ECONNRESET;
- if(c->recv)
- c->recv(c, NULL, 0);
- goto reset;
- break;
+ // Ehm, no. We should never receive a second SYN.
+ return 0;
+
default:
- // TODO: wtf?
+#ifdef UTCP_DEBUG
+ abort();
+#endif
return 0;
}
+
+ // 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;
-
- c->snd.una = hdr.ack;
- 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);
+
+ // Are we still LISTENing?
+ if(utcp->accept) {
+ utcp->accept(c, c->src);
}
- break;
- case LAST_ACK:
- if(hdr.ack == c->snd.nxt) {
+
+ 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.
+#ifdef UTCP_DEBUG
+ abort();
+#endif
+ return 0;
+
+ 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:
+#ifdef UTCP_DEBUG
+ abort();
+#endif
+ return 0;
+ }
- 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();
+ handle_incoming_data(c, hdr.seq, ptr, len);
}
- if(hdr.ctl & FIN) {
+ // 7. Process FIN stuff
+
+ if((hdr.ctl & FIN) && hdr.seq + len == c->rcv.nxt) {
switch(c->state) {
- case CLOSED:
- case LISTEN:
case SYN_SENT:
- return 0;
case SYN_RECEIVED:
+ // This should never happen.
+#ifdef UTCP_DEBUG
+ abort();
+#endif
+ break;
+
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:
+#ifdef UTCP_DEBUG
abort();
+#endif
+ break;
}
- }
- // Process the data
+ // FIN counts as one sequence number
+ c->rcv.nxt++;
+ len++;
- if(len && c->recv) {
- c->recv(c, data, len);
- c->rcv.nxt += len;
- goto ack_and_drop;
+ // Inform the application that the peer closed the connection.
+ if(c->recv) {
+ errno = 0;
+ c->recv(c, NULL, 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(c, len || prevrcvnxt != c->rcv.nxt);
return 0;
reset:
swap_ports(&hdr);
hdr.wnd = 0;
+ hdr.aux = 0;
+
if(hdr.ctl & ACK) {
hdr.seq = hdr.ack;
hdr.ctl = RST;
hdr.seq = 0;
hdr.ctl = RST | ACK;
}
- print_packet(c->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;
- print_packet(c->utcp, "send", &hdr, sizeof hdr);
- utcp->send(utcp, &hdr, sizeof hdr);
- if(c->state == CLOSE_WAIT || c->state == TIME_WAIT) {
- errno = 0;
- if(c->recv)
- c->recv(c, NULL, 0);
- }
+ print_packet(utcp, "send", &hdr, sizeof(hdr));
+ utcp->send(utcp, &hdr, sizeof(hdr));
return 0;
+
}
int utcp_shutdown(struct utcp_connection *c, int 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;
+ }
+
+ // Only process shutting down writes once.
+ if(c->shut_wr) {
+ return 0;
+ }
+
+ c->shut_wr = true;
switch(c->state) {
case CLOSED:
- return 0;
case LISTEN:
+ errno = ENOTCONN;
+ return -1;
+
case SYN_SENT:
- set_state(c, CLOSED);
return 0;
case SYN_RECEIVED:
case ESTABLISHED:
set_state(c, FIN_WAIT_1);
break;
+
case FIN_WAIT_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.last++;
- c->snd.nxt += 1;
+ ack(c, false);
- print_packet(c->utcp, "send", &hdr, sizeof hdr);
- c->utcp->send(c->utcp, &hdr, sizeof hdr);
- return 0;
-}
+ if(!timerisset(&c->rtrx_timeout)) {
+ start_retransmit_timer(c);
+ }
-int utcp_close(struct utcp_connection *c) {
- if(utcp_shutdown(c, SHUT_RDWR))
- return -1;
- 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) {
- 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;
+ return false;
}
- c->reapable = true;
+ c->recv = NULL;
+ c->poll = NULL;
switch(c->state) {
case CLOSED:
- return 0;
+ return true;
+
case LISTEN:
case SYN_SENT:
case CLOSING:
case LAST_ACK:
case TIME_WAIT:
set_state(c, CLOSED);
- return 0;
+ return true;
case SYN_RECEIVED:
case ESTABLISHED:
hdr.wnd = 0;
hdr.ctl = RST;
- print_packet(c->utcp, "send", &hdr, sizeof hdr);
- c->utcp->send(c->utcp, &hdr, sizeof hdr);
- return 0;
+ print_packet(c->utcp, "send", &hdr, sizeof(hdr));
+ c->utcp->send(c->utcp, &hdr, sizeof(hdr));
+ return true;
}
-static void retransmit(struct utcp_connection *c) {
- if(c->state == CLOSED || c->snd.nxt == c->snd.una)
+// Closes all the opened connections
+void utcp_abort_all_connections(struct utcp *utcp) {
+ if(!utcp) {
+ errno = EINVAL;
return;
+ }
- struct utcp *utcp = c->utcp;
+ for(int i = 0; i < utcp->nconnections; i++) {
+ struct utcp_connection *c = utcp->connections[i];
- struct {
- struct hdr hdr;
- char data[c->utcp->mtu];
- } pkt;
+ if(c->reapable || c->state == CLOSED) {
+ continue;
+ }
- pkt.hdr.src = c->src;
- pkt.hdr.dst = c->dst;
+ reset_connection(c);
- switch(c->state) {
- case LISTEN:
- // TODO: this should not happen
- break;
+ if(c->recv) {
+ errno = 0;
+ c->recv(c, NULL, 0);
+ }
+ }
- 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;
+ return;
+}
- 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;
+int utcp_close(struct utcp_connection *c) {
+ if(utcp_shutdown(c, SHUT_RDWR) && errno != ENOTCONN) {
+ return -1;
+ }
- 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;
+ c->recv = NULL;
+ c->poll = NULL;
+ c->reapable = true;
+ return 0;
+}
- default:
- // TODO: implement
- abort();
+int utcp_abort(struct utcp_connection *c) {
+ if(!reset_connection(c)) {
+ return -1;
}
+
+ c->reapable = true;
+ return 0;
}
/* Handle timeouts.
* 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};
for(int i = 0; i < utcp->nconnections; i++) {
struct utcp_connection *c = utcp->connections[i];
- if(!c)
+
+ if(!c) {
continue;
+ }
+ // delete connections that have been utcp_close()d.
if(c->state == CLOSED) {
if(c->reapable) {
- fprintf(stderr, "Reaping %p\n", c);
+ debug("Reaping %p\n", c);
free_connection(c);
i--;
}
+
continue;
}
if(timerisset(&c->conn_timeout) && timercmp(&c->conn_timeout, &now, <)) {
errno = ETIMEDOUT;
c->state = CLOSED;
- if(c->recv)
+
+ if(c->recv) {
c->recv(c, NULL, 0);
+ }
+
continue;
}
if(timerisset(&c->rtrx_timeout) && timercmp(&c->rtrx_timeout, &now, <)) {
+ debug("retransmit()\n");
retransmit(c);
}
- if(timerisset(&c->conn_timeout) && timercmp(&c->conn_timeout, &next, <))
- next = c->conn_timeout;
+ if(c->poll) {
+ if((c->state == ESTABLISHED || c->state == CLOSE_WAIT)) {
+ uint32_t len = buffer_free(&c->sndbuf);
- if(c->snd.nxt != c->snd.una) {
- c->rtrx_timeout = now;
- c->rtrx_timeout.tv_sec++;
- } else {
- timerclear(&c->rtrx_timeout);
+ if(len) {
+ c->poll(c, len);
+ }
+ } else if(c->state == CLOSED) {
+ c->poll(c, 0);
+ }
+ }
+
+ if(timerisset(&c->conn_timeout) && timercmp(&c->conn_timeout, &next, <)) {
+ next = c->conn_timeout;
}
- if(timerisset(&c->rtrx_timeout) && timercmp(&c->rtrx_timeout, &next, <))
+ 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;
+
+ 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);
- if(!utcp)
- return NULL;
+bool utcp_is_active(struct utcp *utcp) {
+ if(!utcp) {
+ 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; // sec
+ utcp->rto = START_RTO; // usec
return utcp;
}
void utcp_exit(struct utcp *utcp) {
- if(!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++) {
+ struct utcp_connection *c = utcp->connections[i];
+
+ if(!c->reapable)
+ if(c->recv) {
+ c->recv(c, NULL, 0);
+ }
+
+ buffer_exit(&c->rcvbuf);
+ buffer_exit(&c->sndbuf);
+ free(c);
+ }
+
+ 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;
+ }
+}
+
+void utcp_reset_timers(struct utcp *utcp) {
+ if(!utcp) {
+ return;
+ }
+
+ struct timeval now, then;
+
+ gettimeofday(&now, NULL);
+
+ then = now;
+
+ 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;
+ }
+
+ if(utcp->rto > START_RTO) {
+ utcp->rto = START_RTO;
+ }
+}
+
+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) {
+ return 0;
+ }
+
+ switch(c->state) {
+ case SYN_SENT:
+ case SYN_RECEIVED:
+ case ESTABLISHED:
+ case CLOSE_WAIT:
+ return buffer_free(&c->sndbuf);
+
+ default:
+ 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