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tcp.c
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tcp.c
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#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/time.h>
#include "platform.h"
#include "util.h"
#include "net.h"
#include "ip.h"
#include "tcp.h"
#define TCP_FLG_FIN 0x01
#define TCP_FLG_SYN 0x02
#define TCP_FLG_RST 0x04
#define TCP_FLG_PSH 0x08
#define TCP_FLG_ACK 0x10
#define TCP_FLG_URG 0x20
#define TCP_FLG_IS(x, y) ((x & 0x3f) == (y))
#define TCP_FLG_ISSET(x, y) ((x & 0x3f) & (y) ? 1 : 0)
#define TCP_PCB_SIZE 16
#define TCP_PCB_MODE_RFC793 1
#define TCP_PCB_MODE_SOCKET 2
#define TCP_PCB_STATE_FREE 0
#define TCP_PCB_STATE_CLOSED 1
#define TCP_PCB_STATE_LISTEN 2
#define TCP_PCB_STATE_SYN_SENT 3
#define TCP_PCB_STATE_SYN_RECEIVED 4
#define TCP_PCB_STATE_ESTABLISHED 5
#define TCP_PCB_STATE_FIN_WAIT1 6
#define TCP_PCB_STATE_FIN_WAIT2 7
#define TCP_PCB_STATE_CLOSING 8
#define TCP_PCB_STATE_TIME_WAIT 9
#define TCP_PCB_STATE_CLOSE_WAIT 10
#define TCP_PCB_STATE_LAST_ACK 11
#define TCP_DEFAULT_RTO 200000 /* micro seconds */
#define TCP_RETRANSMIT_DEADLINE 12 /* seconds */
#define TCP_TIMEWAIT_SEC 30 /* substitute for 2MSL */
#define TCP_SOURCE_PORT_MIN 49152
#define TCP_SOURCE_PORT_MAX 65535
struct pseudo_hdr {
uint32_t src;
uint32_t dst;
uint8_t zero;
uint8_t protocol;
uint16_t len;
};
struct tcp_hdr {
uint16_t src;
uint16_t dst;
uint32_t seq;
uint32_t ack;
uint8_t off;
uint8_t flg;
uint16_t wnd;
uint16_t sum;
uint16_t up;
};
struct tcp_segment_info {
uint32_t seq;
uint32_t ack;
uint16_t len;
uint16_t wnd;
uint16_t up;
};
struct tcp_pcb {
int state;
int mode; /* user command mode */
struct ip_endpoint local;
struct ip_endpoint foreign;
struct {
uint32_t nxt;
uint32_t una;
uint16_t wnd;
uint16_t up;
uint32_t wl1;
uint32_t wl2;
} snd;
uint32_t iss;
struct {
uint32_t nxt;
uint16_t wnd;
uint16_t up;
} rcv;
uint32_t irs;
uint16_t mtu;
uint16_t mss;
uint8_t buf[65535]; /* receive buffer */
struct sched_ctx ctx;
struct queue_head queue; /* retransmit queue */
struct timeval tw_timer;
struct tcp_pcb *parent;
struct queue_head backlog;
};
struct tcp_queue_entry {
struct timeval first;
struct timeval last;
unsigned int rto; /* micro seconds */
uint32_t seq;
uint8_t flg;
size_t len;
};
static mutex_t mutex = MUTEX_INITIALIZER;
static struct tcp_pcb pcbs[TCP_PCB_SIZE];
static ssize_t
tcp_output_segment(uint32_t seq, uint32_t ack, uint8_t flg, uint16_t wnd, uint8_t *data, size_t len, struct ip_endpoint *local, struct ip_endpoint *foreign);
static char *
tcp_flg_ntoa(uint8_t flg)
{
static char str[9];
snprintf(str, sizeof(str), "--%c%c%c%c%c%c",
TCP_FLG_ISSET(flg, TCP_FLG_URG) ? 'U' : '-',
TCP_FLG_ISSET(flg, TCP_FLG_ACK) ? 'A' : '-',
TCP_FLG_ISSET(flg, TCP_FLG_PSH) ? 'P' : '-',
TCP_FLG_ISSET(flg, TCP_FLG_RST) ? 'R' : '-',
TCP_FLG_ISSET(flg, TCP_FLG_SYN) ? 'S' : '-',
TCP_FLG_ISSET(flg, TCP_FLG_FIN) ? 'F' : '-');
return str;
}
static void
tcp_dump(const uint8_t *data, size_t len)
{
struct tcp_hdr *hdr;
flockfile(stderr);
hdr = (struct tcp_hdr *)data;
fprintf(stderr, " src: %u\n", ntoh16(hdr->src));
fprintf(stderr, " dst: %u\n", ntoh16(hdr->dst));
fprintf(stderr, " seq: %u\n", ntoh32(hdr->seq));
fprintf(stderr, " ack: %u\n", ntoh32(hdr->ack));
fprintf(stderr, " off: 0x%02x (%d)\n", hdr->off, (hdr->off >> 4) << 2);
fprintf(stderr, " flg: 0x%02x (%s)\n", hdr->flg, tcp_flg_ntoa(hdr->flg));
fprintf(stderr, " wnd: %u\n", ntoh16(hdr->wnd));
fprintf(stderr, " sum: 0x%04x\n", ntoh16(hdr->sum));
fprintf(stderr, " up: %u\n", ntoh16(hdr->up));
#ifdef HEXDUMP
hexdump(stderr, data, len);
#endif
funlockfile(stderr);
}
/*
* TCP Protocol Control Block (PCB)
*
* NOTE: TCP PCB functions must be called after mutex locked
*/
static struct tcp_pcb *
tcp_pcb_alloc(void)
{
struct tcp_pcb *pcb;
for (pcb = pcbs; pcb < tailof(pcbs); pcb++) {
if (pcb->state == TCP_PCB_STATE_FREE) {
pcb->state = TCP_PCB_STATE_CLOSED;
sched_ctx_init(&pcb->ctx);
return pcb;
}
}
return NULL;
}
static void
tcp_pcb_release(struct tcp_pcb *pcb)
{
struct queue_entry *entry;
struct tcp_pcb *est;
char ep1[IP_ENDPOINT_STR_LEN];
char ep2[IP_ENDPOINT_STR_LEN];
if (sched_ctx_destroy(&pcb->ctx) == -1) {
sched_wakeup(&pcb->ctx);
return;
}
while ((entry = queue_pop(&pcb->queue)) != NULL) {
memory_free(entry);
}
while ((est = queue_pop(&pcb->backlog)) != NULL) {
tcp_pcb_release(est);
}
debugf("released, local=%s, foreign=%s",
ip_endpoint_ntop(&pcb->local, ep1, sizeof(ep1)), ip_endpoint_ntop(&pcb->foreign, ep2, sizeof(ep2)));
memset(pcb, 0, sizeof(*pcb));
}
static struct tcp_pcb *
tcp_pcb_select(struct ip_endpoint *local, struct ip_endpoint *foreign)
{
struct tcp_pcb *pcb, *listen_pcb = NULL;
for (pcb = pcbs; pcb < tailof(pcbs); pcb++) {
if ((pcb->local.addr == IP_ADDR_ANY || pcb->local.addr == local->addr) && pcb->local.port == local->port) {
if (!foreign) {
return pcb;
}
if (pcb->foreign.addr == foreign->addr && pcb->foreign.port == foreign->port) {
return pcb;
}
if (pcb->state == TCP_PCB_STATE_LISTEN) {
if (pcb->foreign.addr == IP_ADDR_ANY && pcb->foreign.port == 0) {
/* LISTENed with wildcard foreign address/port */
listen_pcb = pcb;
}
}
}
}
return listen_pcb;
}
static struct tcp_pcb *
tcp_pcb_get(int id)
{
struct tcp_pcb *pcb;
if (id < 0 || id >= (int)countof(pcbs)) {
/* out of range */
return NULL;
}
pcb = &pcbs[id];
if (pcb->state == TCP_PCB_STATE_FREE) {
return NULL;
}
return pcb;
}
static int
tcp_pcb_id(struct tcp_pcb *pcb)
{
return indexof(pcbs, pcb);
}
/*
* TCP Retransmit
*
* NOTE: TCP Retransmit functions must be called after mutex locked
*/
static int
tcp_retransmit_queue_add(struct tcp_pcb *pcb, uint32_t seq, uint8_t flg, uint8_t *data, size_t len)
{
struct tcp_queue_entry *entry;
entry = memory_alloc(sizeof(*entry) + len);
if (!entry) {
errorf("memory_alloc() failure");
return -1;
}
entry->rto = TCP_DEFAULT_RTO;
entry->seq = seq;
entry->flg = flg;
entry->len = len;
memcpy(entry + 1, data, entry->len);
gettimeofday(&entry->first, NULL);
entry->last = entry->first;
if (!queue_push(&pcb->queue, entry)) {
errorf("queue_push() failure");
memory_free(entry);
return -1;
}
return 0;
}
static void
tcp_retransmit_queue_cleanup(struct tcp_pcb *pcb)
{
struct tcp_queue_entry *entry;
while ((entry = queue_peek(&pcb->queue))) {
if (entry->seq >= pcb->snd.una) {
break;
}
entry = queue_pop(&pcb->queue);
debugf("remove, seq=%u, flags=%s, len=%u", entry->seq, tcp_flg_ntoa(entry->flg), entry->len);
memory_free(entry);
}
return;
}
static void
tcp_retransmit_queue_emit(void *arg, void *data)
{
struct tcp_pcb *pcb;
struct tcp_queue_entry *entry;
struct timeval now, diff, timeout;
pcb = (struct tcp_pcb *)arg;
entry = (struct tcp_queue_entry *)data;
gettimeofday(&now, NULL);
timersub(&now, &entry->first, &diff);
if (diff.tv_sec >= TCP_RETRANSMIT_DEADLINE) {
pcb->state = TCP_PCB_STATE_CLOSED;
sched_wakeup(&pcb->ctx);
return;
}
timeout = entry->last;
timeval_add_usec(&timeout, entry->rto);
if (timercmp(&now, &timeout, >)) {
tcp_output_segment(entry->seq, pcb->rcv.nxt, entry->flg, pcb->rcv.wnd, (uint8_t *)(entry+1), entry->len, &pcb->local, &pcb->foreign);
entry->last = now;
entry->rto *= 2;
}
}
static void
tcp_set_timewait_timer(struct tcp_pcb *pcb)
{
gettimeofday(&pcb->tw_timer, NULL);
pcb->tw_timer.tv_sec += TCP_TIMEWAIT_SEC;
debugf("start time_wait timer: %d seconds", TCP_TIMEWAIT_SEC);
}
static ssize_t
tcp_output_segment(uint32_t seq, uint32_t ack, uint8_t flg, uint16_t wnd, uint8_t *data, size_t len, struct ip_endpoint *local, struct ip_endpoint *foreign)
{
uint8_t buf[IP_PAYLOAD_SIZE_MAX] = {};
struct tcp_hdr *hdr;
struct pseudo_hdr pseudo;
uint16_t psum;
uint16_t total;
char ep1[IP_ENDPOINT_STR_LEN];
char ep2[IP_ENDPOINT_STR_LEN];
hdr = (struct tcp_hdr *)buf;
hdr->src = local->port;
hdr->dst = foreign->port;
hdr->seq = hton32(seq);
hdr->ack = hton32(ack);
hdr->off = (sizeof(*hdr) >> 2) << 4;
hdr->flg = flg;
hdr->wnd = hton16(wnd);
hdr->sum = 0;
hdr->up = 0;
memcpy(hdr + 1, data, len);
pseudo.src = local->addr;
pseudo.dst = foreign->addr;
pseudo.zero = 0;
pseudo.protocol = IP_PROTOCOL_TCP;
total = sizeof(*hdr) + len;
pseudo.len = hton16(total);
psum = ~cksum16((uint16_t *)&pseudo, sizeof(pseudo), 0);
hdr->sum = cksum16((uint16_t *)hdr, total, psum);
debugf("%s => %s, len=%zu (payload=%zu)",
ip_endpoint_ntop(local, ep1, sizeof(ep1)), ip_endpoint_ntop(foreign, ep2, sizeof(ep2)), total, len);
tcp_dump((uint8_t *)hdr, total);
if (ip_output(IP_PROTOCOL_TCP, (uint8_t *)hdr, total, local->addr, foreign->addr) == -1) {
return -1;
}
return len;
}
static ssize_t
tcp_output(struct tcp_pcb *pcb, uint8_t flg, uint8_t *data, size_t len)
{
uint32_t seq;
seq = pcb->snd.nxt;
if (TCP_FLG_ISSET(flg, TCP_FLG_SYN)) {
seq = pcb->iss;
}
if (TCP_FLG_ISSET(flg, TCP_FLG_SYN | TCP_FLG_FIN) || len) {
tcp_retransmit_queue_add(pcb, seq, flg, data, len);
}
return tcp_output_segment(seq, pcb->rcv.nxt, flg, pcb->rcv.wnd, data, len, &pcb->local, &pcb->foreign);
}
/* rfc793 - section 3.9 [Event Processing > SEGMENT ARRIVES] */
static void
tcp_segment_arrives(struct tcp_segment_info *seg, uint8_t flags, uint8_t *data, size_t len, struct ip_endpoint *local, struct ip_endpoint *foreign)
{
struct tcp_pcb *pcb, *new_pcb;
int acceptable = 0;
pcb = tcp_pcb_select(local, foreign);
if (!pcb || pcb->state == TCP_PCB_STATE_CLOSED) {
if (TCP_FLG_ISSET(flags, TCP_FLG_RST)) {
return;
}
if (!TCP_FLG_ISSET(flags, TCP_FLG_ACK)) {
tcp_output_segment(0, seg->seq + seg->len, TCP_FLG_RST | TCP_FLG_ACK, 0, NULL, 0, local, foreign);
} else {
tcp_output_segment(seg->ack, 0, TCP_FLG_RST, 0, NULL, 0, local, foreign);
}
return;
}
switch(pcb->state) {
case TCP_PCB_STATE_LISTEN:
/*
* first check for an RST
*/
if (TCP_FLG_ISSET(flags, TCP_FLG_RST)) {
return;
}
/*
* second check for an ACK
*/
if (TCP_FLG_ISSET(flags, TCP_FLG_ACK)) {
tcp_output_segment(seg->ack, 0, TCP_FLG_RST, 0, NULL, 0, local, foreign);
return;
}
/*
* third check for an SYN
*/
if (TCP_FLG_ISSET(flags, TCP_FLG_SYN)) {
/* ignore: security/compartment check */
/* ignore: precedence check */
if (pcb->mode == TCP_PCB_MODE_SOCKET) {
new_pcb = tcp_pcb_alloc();
if (!new_pcb) {
errorf("tcp_pcb_alloc() failure");
return;
}
new_pcb->mode = TCP_PCB_MODE_SOCKET;
new_pcb->parent = pcb;
pcb = new_pcb;
}
pcb->local = *local;
pcb->foreign = *foreign;
pcb->rcv.wnd = sizeof(pcb->buf);
pcb->rcv.nxt = seg->seq + 1;
pcb->irs = seg->seq;
pcb->iss = random();
tcp_output(pcb, TCP_FLG_SYN | TCP_FLG_ACK, NULL, 0);
pcb->snd.nxt = pcb->iss + 1;
pcb->snd.una = pcb->iss;
pcb->state = TCP_PCB_STATE_SYN_RECEIVED;
/* ignore: Note that any other incoming control or data (combined with SYN) will be processed
in the SYN-RECEIVED state, but processing of SYN and ACK should not be repeated */
return;
}
/*
* fourth other text or control
*/
/* drop segment */
return;
case TCP_PCB_STATE_SYN_SENT:
/*
* first check the ACK bit
*/
if (TCP_FLG_ISSET(flags, TCP_FLG_ACK)) {
if (seg->ack <= pcb->iss || seg->ack > pcb->snd.nxt) {
tcp_output_segment(seg->ack, 0, TCP_FLG_RST, 0, NULL, 0, local, foreign);
return;
}
if (pcb->snd.una <= seg->ack && seg->ack <= pcb->snd.nxt) {
acceptable = 1;
}
}
/*
* second check the RST bit
*/
if (TCP_FLG_ISSET(flags, TCP_FLG_RST)) {
if (acceptable) {
errorf("connection reset");
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
}
/* drop segment */
return;
}
/*
* ignore: third check security and precedence
*/
/*
* fourth check the SYN bit
*/
if (TCP_FLG_ISSET(flags, TCP_FLG_SYN)) {
pcb->rcv.nxt = seg->seq + 1;
pcb->irs = seg->seq;
if (acceptable) {
pcb->snd.una = seg->ack;
tcp_retransmit_queue_cleanup(pcb);
}
if (pcb->snd.una > pcb->iss) {
pcb->state = TCP_PCB_STATE_ESTABLISHED;
tcp_output(pcb, TCP_FLG_ACK, NULL, 0);
/* NOTE: not specified in the RFC793, but send window initialization required */
pcb->snd.wnd = seg->wnd;
pcb->snd.wl1 = seg->seq;
pcb->snd.wl2 = seg->ack;
sched_wakeup(&pcb->ctx);
/* ignore: continue processing at the sixth step below where the URG bit is checked */
return;
} else {
pcb->state = TCP_PCB_STATE_SYN_RECEIVED;
tcp_output(pcb, TCP_FLG_SYN | TCP_FLG_ACK, NULL, 0);
/* ignore: If there are other controls or text in the segment, queue them for processing after the ESTABLISHED state has been reached */
return;
}
}
/*
* fifth, if neither of the SYN or RST bits is set then drop the segment and return
*/
/* drop segment */
return;
}
/*
* Otherwise
*/
/*
* first check sequence number
*/
switch (pcb->state) {
case TCP_PCB_STATE_SYN_RECEIVED:
case TCP_PCB_STATE_ESTABLISHED:
case TCP_PCB_STATE_FIN_WAIT1:
case TCP_PCB_STATE_FIN_WAIT2:
case TCP_PCB_STATE_CLOSE_WAIT:
case TCP_PCB_STATE_CLOSING:
case TCP_PCB_STATE_LAST_ACK:
case TCP_PCB_STATE_TIME_WAIT:
if (!seg->len) {
if (!pcb->rcv.wnd) {
if (seg->seq == pcb->rcv.nxt) {
acceptable = 1;
}
} else {
if (pcb->rcv.nxt <= seg->seq && seg->seq < pcb->rcv.nxt + pcb->rcv.wnd) {
acceptable = 1;
}
}
} else {
if (!pcb->rcv.wnd) {
/* not acceptable */
} else {
if ((pcb->rcv.nxt <= seg->seq && seg->seq < pcb->rcv.nxt + pcb->rcv.wnd) ||
(pcb->rcv.nxt <= seg->seq + seg->len - 1 && seg->seq + seg->len - 1 < pcb->rcv.nxt + pcb->rcv.wnd)) {
acceptable = 1;
}
}
}
if (!acceptable) {
if (!TCP_FLG_ISSET(flags, TCP_FLG_RST)) {
tcp_output(pcb, TCP_FLG_ACK, NULL, 0);
}
return;
}
/*
* In the following it is assumed that the segment is the idealized
* segment that begins at RCV.NXT and does not exceed the window.
* One could tailor actual segments to fit this assumption by
* trimming off any portions that lie outside the window (including
* SYN and FIN), and only processing further if the segment then
* begins at RCV.NXT. Segments with higher begining sequence
* numbers may be held for later processing.
*/
}
/*
* second check the RST bit
*/
switch (pcb->state) {
case TCP_PCB_STATE_SYN_RECEIVED:
if (TCP_FLG_ISSET(flags, TCP_FLG_RST)) {
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
return;
}
break;
case TCP_PCB_STATE_ESTABLISHED:
case TCP_PCB_STATE_FIN_WAIT1:
case TCP_PCB_STATE_FIN_WAIT2:
case TCP_PCB_STATE_CLOSE_WAIT:
if (TCP_FLG_ISSET(flags, TCP_FLG_RST)) {
errorf("connection reset");
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
return;
}
break;
case TCP_PCB_STATE_CLOSING:
case TCP_PCB_STATE_LAST_ACK:
case TCP_PCB_STATE_TIME_WAIT:
if (TCP_FLG_ISSET(flags, TCP_FLG_RST)) {
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
return;
}
break;
}
/*
* ignore: third check security and precedence
*/
/*
* fourth check the SYN bit
*/
switch (pcb->state) {
case TCP_PCB_STATE_SYN_RECEIVED:
case TCP_PCB_STATE_ESTABLISHED:
case TCP_PCB_STATE_FIN_WAIT1:
case TCP_PCB_STATE_FIN_WAIT2:
case TCP_PCB_STATE_CLOSE_WAIT:
case TCP_PCB_STATE_CLOSING:
case TCP_PCB_STATE_LAST_ACK:
case TCP_PCB_STATE_TIME_WAIT:
if (TCP_FLG_ISSET(flags, TCP_FLG_SYN)) {
tcp_output(pcb, TCP_FLG_RST, NULL, 0);
errorf("connection reset");
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
return;
}
}
/*
* fifth check the ACK field
*/
if (!TCP_FLG_ISSET(flags, TCP_FLG_ACK)) {
/* drop segment */
return;
}
switch (pcb->state) {
case TCP_PCB_STATE_SYN_RECEIVED:
if (pcb->snd.una <= seg->ack && seg->ack <= pcb->snd.nxt) {
pcb->state = TCP_PCB_STATE_ESTABLISHED;
sched_wakeup(&pcb->ctx);
if (pcb->parent) {
queue_push(&pcb->parent->backlog, pcb);
sched_wakeup(&pcb->parent->ctx);
}
} else {
tcp_output_segment(seg->ack, 0, TCP_FLG_RST, 0, NULL, 0, local, foreign);
return;
}
/* fall through */
case TCP_PCB_STATE_ESTABLISHED:
case TCP_PCB_STATE_FIN_WAIT1:
case TCP_PCB_STATE_FIN_WAIT2:
case TCP_PCB_STATE_CLOSE_WAIT:
case TCP_PCB_STATE_CLOSING:
if (pcb->snd.una < seg->ack && seg->ack <= pcb->snd.nxt) {
pcb->snd.una = seg->ack;
tcp_retransmit_queue_cleanup(pcb);
/* ignore: Users should receive positive acknowledgments for buffers
which have been SENT and fully acknowledged (i.e., SEND buffer should be returned with "ok" response) */
if (pcb->snd.wl1 < seg->seq || (pcb->snd.wl1 == seg->seq && pcb->snd.wl2 <= seg->ack)) {
pcb->snd.wnd = seg->wnd;
pcb->snd.wl1 = seg->seq;
pcb->snd.wl2 = seg->ack;
}
} else if (seg->ack < pcb->snd.una) {
/* ignore */
} else if (seg->ack > pcb->snd.nxt) {
tcp_output(pcb, TCP_FLG_ACK, NULL, 0);
return;
}
switch (pcb->state) {
case TCP_PCB_STATE_FIN_WAIT1:
if (seg->ack == pcb->snd.nxt) {
pcb->state = TCP_PCB_STATE_FIN_WAIT2;
}
break;
case TCP_PCB_STATE_FIN_WAIT2:
/* do not delete the TCB */
break;
case TCP_PCB_STATE_CLOSE_WAIT:
/* do nothing */
break;
case TCP_PCB_STATE_CLOSING:
if (seg->ack == pcb->snd.nxt) {
pcb->state = TCP_PCB_STATE_TIME_WAIT;
/* NOTE: set 2MSL timer, although it is not explicitly stated in the RFC */
tcp_set_timewait_timer(pcb);
sched_wakeup(&pcb->ctx);
}
break;
}
break;
case TCP_PCB_STATE_LAST_ACK:
if (seg->ack == pcb->snd.nxt) {
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
}
return;
case TCP_PCB_STATE_TIME_WAIT:
if (TCP_FLG_ISSET(flags, TCP_FLG_FIN)) {
tcp_set_timewait_timer(pcb); /* restart time-wait timer */
}
break;
}
/*
* ignore: sixth, check the URG bit
*/
/*
* seventh, process the segment text
*/
switch (pcb->state) {
case TCP_PCB_STATE_ESTABLISHED:
case TCP_PCB_STATE_FIN_WAIT1:
case TCP_PCB_STATE_FIN_WAIT2:
if (len) {
memcpy(pcb->buf + (sizeof(pcb->buf) - pcb->rcv.wnd), data, len);
pcb->rcv.nxt = seg->seq + seg->len;
pcb->rcv.wnd -= len;
tcp_output(pcb, TCP_FLG_ACK, NULL, 0);
sched_wakeup(&pcb->ctx);
}
break;
case TCP_PCB_STATE_CLOSE_WAIT:
case TCP_PCB_STATE_CLOSING:
case TCP_PCB_STATE_LAST_ACK:
case TCP_PCB_STATE_TIME_WAIT:
/* ignore segment text */
break;
}
/*
* eighth, check the FIN bit
*/
if (TCP_FLG_ISSET(flags, TCP_FLG_FIN)) {
switch (pcb->state) {
case TCP_PCB_STATE_CLOSED:
case TCP_PCB_STATE_LISTEN:
case TCP_PCB_STATE_SYN_SENT:
/* drop segment */
return;
}
pcb->rcv.nxt = seg->seq + 1;
tcp_output(pcb, TCP_FLG_ACK, NULL, 0);
switch (pcb->state) {
case TCP_PCB_STATE_SYN_RECEIVED:
case TCP_PCB_STATE_ESTABLISHED:
pcb->state = TCP_PCB_STATE_CLOSE_WAIT;
sched_wakeup(&pcb->ctx);
break;
case TCP_PCB_STATE_FIN_WAIT1:
if (seg->ack == pcb->snd.nxt) {
pcb->state = TCP_PCB_STATE_TIME_WAIT;
tcp_set_timewait_timer(pcb);
} else {
pcb->state = TCP_PCB_STATE_CLOSING;
}
break;
case TCP_PCB_STATE_FIN_WAIT2:
pcb->state = TCP_PCB_STATE_TIME_WAIT;
tcp_set_timewait_timer(pcb);
break;
case TCP_PCB_STATE_CLOSE_WAIT:
/* Remain in the CLOSE-WAIT state */
break;
case TCP_PCB_STATE_CLOSING:
/* Remain in the CLOSING state */
break;
case TCP_PCB_STATE_LAST_ACK:
/* Remain in the LAST-ACK state */
break;
case TCP_PCB_STATE_TIME_WAIT:
/* Remain in the TIME-WAIT state */
tcp_set_timewait_timer(pcb); /* restart time-wait timer */
break;
}
}
return;
}
static void
tcp_input(const uint8_t *data, size_t len, ip_addr_t src, ip_addr_t dst, struct ip_iface *iface)
{
struct tcp_hdr *hdr;
struct pseudo_hdr pseudo;
uint16_t psum, hlen;
char addr1[IP_ADDR_STR_LEN];
char addr2[IP_ADDR_STR_LEN];
struct ip_endpoint local, foreign;
struct tcp_segment_info seg;
if (len < sizeof(*hdr)) {
errorf("too short");
return;
}
hdr = (struct tcp_hdr *)data;
pseudo.src = src;
pseudo.dst = dst;
pseudo.zero = 0;
pseudo.protocol = IP_PROTOCOL_TCP;
pseudo.len = hton16(len);
psum = ~cksum16((uint16_t *)&pseudo, sizeof(pseudo), 0);
if (cksum16((uint16_t *)hdr, len, psum) != 0) {
errorf("checksum error: sum=0x%04x, verify=0x%04x", ntoh16(hdr->sum), ntoh16(cksum16((uint16_t *)hdr, len, -hdr->sum + psum)));
return;
}
if (src == IP_ADDR_BROADCAST || src == iface->broadcast || dst == IP_ADDR_BROADCAST || dst == iface->broadcast) {
errorf("only supports unicast, src=%s, dst=%s",
ip_addr_ntop(src, addr1, sizeof(addr1)), ip_addr_ntop(dst, addr2, sizeof(addr2)));
return;
}
debugf("%s:%d => %s:%d, len=%zu (payload=%zu)",
ip_addr_ntop(src, addr1, sizeof(addr1)), ntoh16(hdr->src),
ip_addr_ntop(dst, addr2, sizeof(addr2)), ntoh16(hdr->dst),
len, len - sizeof(*hdr));
tcp_dump(data, len);
local.addr = dst;
local.port = hdr->dst;
foreign.addr = src;
foreign.port = hdr->src;
hlen = (hdr->off >> 4) << 2;
seg.seq = ntoh32(hdr->seq);
seg.ack = ntoh32(hdr->ack);
seg.len = len - hlen;
if (TCP_FLG_ISSET(hdr->flg, TCP_FLG_SYN)) {
seg.len++; /* SYN flag consumes one sequence number */
}
if (TCP_FLG_ISSET(hdr->flg, TCP_FLG_FIN)) {
seg.len++; /* FIN flag consumes one sequence number */
}
seg.wnd = ntoh16(hdr->wnd);
seg.up = ntoh16(hdr->up);
mutex_lock(&mutex);
tcp_segment_arrives(&seg, hdr->flg, (uint8_t *)hdr + hlen, len - hlen, &local, &foreign);
mutex_unlock(&mutex);
return;
}
static void
tcp_timer(void)
{
struct tcp_pcb *pcb;
struct timeval now;
char ep1[IP_ENDPOINT_STR_LEN];
char ep2[IP_ENDPOINT_STR_LEN];
mutex_lock(&mutex);
gettimeofday(&now, NULL);
for (pcb = pcbs; pcb < tailof(pcbs); pcb++) {
if (pcb->state == TCP_PCB_STATE_FREE) {
continue;
}
if (pcb->state == TCP_PCB_STATE_TIME_WAIT) {
if (timercmp(&now, &pcb->tw_timer, >) != 0) {
debugf("timewait has elapsed, local=%s, foreign=%s",
ip_endpoint_ntop(&pcb->local, ep1, sizeof(ep1)), ip_endpoint_ntop(&pcb->foreign, ep2, sizeof(ep2)));
tcp_pcb_release(pcb);
continue;
}
}
queue_foreach(&pcb->queue, tcp_retransmit_queue_emit, pcb);
}
mutex_unlock(&mutex);
}
static void
event_handler(void *arg)
{
struct tcp_pcb *pcb;
mutex_lock(&mutex);
for (pcb = pcbs; pcb < tailof(pcbs); pcb++) {
if (pcb->state != TCP_PCB_STATE_FREE) {
sched_interrupt(&pcb->ctx);
}
}
mutex_unlock(&mutex);
}
int
tcp_init(void)
{
struct timeval interval = {0,100000};
if (ip_protocol_register("TCP", IP_PROTOCOL_TCP, tcp_input) == -1) {
errorf("ip_protocol_register() failure");
return -1;
}
if (net_timer_register("TCP Timer", interval, tcp_timer) == -1) {
errorf("net_timer_register() failure");
return -1;
}
net_event_subscribe(event_handler, NULL);
return 0;
}
/*
* TCP User Command (RFC793)
*/
int
tcp_open_rfc793(struct ip_endpoint *local, struct ip_endpoint *foreign, int active)
{
struct tcp_pcb *pcb;
char ep1[IP_ENDPOINT_STR_LEN];
char ep2[IP_ENDPOINT_STR_LEN];
int state, id;
mutex_lock(&mutex);
pcb = tcp_pcb_alloc();
if (!pcb) {
errorf("tcp_pcb_alloc() failure");
mutex_unlock(&mutex);
return -1;
}
pcb->mode = TCP_PCB_MODE_RFC793;
if (!active) {
debugf("passive open: local=%s, waiting for connection...", ip_endpoint_ntop(local, ep1, sizeof(ep1)));
pcb->local = *local;
if (foreign) {
pcb->foreign = *foreign;
}
pcb->state = TCP_PCB_STATE_LISTEN;
} else {
debugf("active open: local=%s, foreign=%s, connecting...",
ip_endpoint_ntop(local, ep1, sizeof(ep1)), ip_endpoint_ntop(foreign, ep2, sizeof(ep2)));
pcb->local = *local;
pcb->foreign = *foreign;
pcb->rcv.wnd = sizeof(pcb->buf);
pcb->iss = random();
if (tcp_output(pcb, TCP_FLG_SYN, NULL, 0) == -1) {
errorf("tcp_output() failure");
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
mutex_unlock(&mutex);
return -1;
}
pcb->snd.una = pcb->iss;
pcb->snd.nxt = pcb->iss + 1;
pcb->state = TCP_PCB_STATE_SYN_SENT;
}
AGAIN:
state = pcb->state;
/* waiting for state changed */
while (pcb->state == state) {
if (sched_sleep(&pcb->ctx, &mutex, NULL) == -1) {
debugf("interrupted");
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
mutex_unlock(&mutex);
errno = EINTR;
return -1;
}
}
if (pcb->state != TCP_PCB_STATE_ESTABLISHED) {
if (pcb->state == TCP_PCB_STATE_SYN_RECEIVED) {
goto AGAIN;
}
errorf("open error: %d", pcb->state);
pcb->state = TCP_PCB_STATE_CLOSED;
tcp_pcb_release(pcb);
mutex_unlock(&mutex);
return -1;
}
id = tcp_pcb_id(pcb);
debugf("connection established: local=%s, foreign=%s",
ip_endpoint_ntop(&pcb->local, ep1, sizeof(ep1)), ip_endpoint_ntop(&pcb->foreign, ep2, sizeof(ep2)));
mutex_unlock(&mutex);
return id;
}
int
tcp_state(int id)
{
struct tcp_pcb *pcb;
int state;
mutex_lock(&mutex);
pcb = tcp_pcb_get(id);
if (!pcb) {
errorf("pcb not found");
mutex_unlock(&mutex);
return -1;
}
if (pcb->mode != TCP_PCB_MODE_RFC793) {
errorf("not opened in rfc793 mode");
mutex_unlock(&mutex);
return -1;
}
state = pcb->state;
mutex_unlock(&mutex);
return state;
}
/*
* TCP User Command (Socket)
*/
int
tcp_open(void)
{
struct tcp_pcb *pcb;
int id;
mutex_lock(&mutex);
pcb = tcp_pcb_alloc();
if (!pcb) {
errorf("tcp_pcb_alloc() failure");
mutex_unlock(&mutex);
return -1;