tcp.c

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    ip_header_t  *ip = pkt->ip_hdr;
    tcp_socket_t *prev,*s;
    dword        ack;
    int          queued = 0;

    /* set length for pseudo sum calculation */
    ip->length = htons(pkt->pkt_bytes);

    if (__sum((word *)tcp, pkt->pkt_bytes, __pseudo_sum(ip)) == 0) {
	for (prev = NULL, s = tcp_list; s; prev = s, s = s->next) {
	    if (s->our_port == ntohs(tcp->dest_port)) {
		if (s->his_port == 0)
		    break;
		if (s->his_port == ntohs(tcp->src_port) &&
		    !memcmp(r->ip_addr, s->his_addr.ip_addr, sizeof(ip_addr_t)))
		    break;
	    }
	}

	if (s) {
	    /* found the socket this packet belongs to */
	    
	    /* refresh his ethernet address */
	    memcpy(s->his_addr.enet_addr, r->enet_addr, sizeof(enet_addr_t));

	    if (s->state != _SYN_RCVD && tcp->flags & TCP_FLAG_RST) {
		BSPLOG(bsp_log("TCP_FLAG_RST rcvd\n"));
		do_reset(s);
		__pktbuf_free(pkt);
		return;
	    }

	    switch (s->state) {

	      case _SYN_SENT:
		/* active open not supported */
		break;

	      case _LISTEN:
		if (tcp->flags & TCP_FLAG_SYN) {
		    s->state = _SYN_RCVD;
		    s->ack = ntohl(tcp->seqnum) + 1;
		    s->his_port = ntohs(tcp->src_port);
		    memcpy(s->his_addr.ip_addr, r->ip_addr, sizeof(ip_addr_t));
		    s->data_bytes = 0;
		    s->ack_pending = 0;

		    BSPLOG(bsp_log("SYN from %d.%d.%d.%d:%d (seq %x)\n",
			       s->his_addr.ip_addr[0],s->his_addr.ip_addr[1],
			       s->his_addr.ip_addr[2],s->his_addr.ip_addr[3],
			       s->his_port, ntohl(tcp->seqnum)));

		    tcp_send(s, TCP_FLAG_SYN | TCP_FLAG_ACK, 0);
		}
		else
		    send_reset(pkt, r);
		break;

	      case _SYN_RCVD:
		BSPLOG(bsp_log("_SYN_RCVD timer cancel.\n"));
		__timer_cancel(&s->timer);

		/* go back to _LISTEN state if reset */
		if (tcp->flags & TCP_FLAG_RST) {
		    s->state = _LISTEN;

		    BSPLOG(bsp_log("_SYN_RCVD --> _LISTEN\n"));

		} else if (tcp->flags & TCP_FLAG_SYN) {
		    /* apparently our SYN/ACK was lost? */
		    tcp_send(s, 0, 1);

		    BSPLOG(bsp_log("retransmitting SYN/ACK\n"));

		} else if ((tcp->flags & TCP_FLAG_ACK) &&
			   ntohl(tcp->acknum) == (s->seq + 1)) {
		    /* we've established the connection */
		    s->state = _ESTABLISHED;
		    s->seq++;

		    BSPLOG(bsp_log("ACK received - connection established\n"));
		}
		break;

	      case _ESTABLISHED:
	      case _CLOSE_WAIT:
		ack = s->ack;  /* save original ack */
		if (tcp->flags & TCP_FLAG_ACK)
		    handle_ack(s, pkt);

		queued = handle_data(s, pkt);

		if ((tcp->flags & TCP_FLAG_FIN) &&
		    ntohl(tcp->seqnum) == s->ack) {

		    BSPLOG(bsp_log("FIN received - going to _CLOSE_WAIT\n"));

		    s->ack++;
		    s->state = _CLOSE_WAIT;
		}
		/*
		 * Send an ack if neccessary.
		 */
		if (s->ack != ack || s->ack_pending) {
		    /*
		     * we can't send an ack if our write packet is holding outgoing
		     * data pending an incoming ack.
		     */
		    if (s->data_bytes == 0) {
			BSPLOG(bsp_log("Sending ack: new[%x] old[%x]\n", s->ack, ack));
			__timer_cancel(&s->timer);
			tcp_send(s, TCP_FLAG_ACK, 0);
			s->ack_pending = 0;
		    } else
			s->ack_pending = 1;
		}
		break;

	      case _LAST_ACK:
		if (tcp->flags & TCP_FLAG_ACK) {
		    handle_ack(s, pkt);
		    if (ntohl(tcp->acknum) == (s->seq + 1)) {
			BSPLOG(bsp_log("_LAST_ACK --> _CLOSED\n"));
			s->state = _CLOSED;
			unlink_socket(s);
		    }
		}
		break;

	      case _FIN_WAIT_1:
		if (tcp->flags & TCP_FLAG_ACK) {
		    handle_ack(s, pkt);
		    if (ntohl(tcp->acknum) == (s->seq + 1)) {
			/* got ACK for FIN packet */
			if (tcp->flags & TCP_FLAG_FIN) {
			    BSPLOG(bsp_log("_FIN_WAIT_1 --> _TIME_WAIT\n"));
			    s->ack++;
			    s->state = _TIME_WAIT;
			    tcp_send(s, TCP_FLAG_ACK, 0);
			} else {
			    s->state = _FIN_WAIT_2;
			    BSPLOG(bsp_log("_FIN_WAIT_1 --> _FIN_WAIT_2\n"));
			}
		    }
		}
		if (tcp->flags & TCP_FLAG_FIN) {
		    BSPLOG(bsp_log("_FIN_WAIT_1 --> _CLOSING\n"));
		    __timer_cancel(&s->timer);
		    s->ack++;
		    s->state = _CLOSING;
		    tcp_send(s, TCP_FLAG_FIN | TCP_FLAG_ACK, 0);
		}
		break;

	      case _FIN_WAIT_2:
		queued = handle_data(s, pkt);
		if (tcp->flags & TCP_FLAG_FIN) {
		    BSPLOG(bsp_log("_FIN_WAIT_2 --> _TIME_WAIT\n"));
		    s->ack++;
		    s->state = _TIME_WAIT;
		    tcp_send(s, TCP_FLAG_ACK, 0);
		}
		break;

	      case _CLOSING:
		if (tcp->flags & TCP_FLAG_ACK) {
		    handle_ack(s, pkt);
		    if (ntohl(tcp->acknum) == (s->seq + 1)) {
			/* got ACK for FIN packet */
			BSPLOG(bsp_log("_CLOSING --> _TIME_WAIT\n"));
			__timer_cancel(&s->timer);
			s->state = _TIME_WAIT;
		    }
		}
		break;

	      case _TIME_WAIT:
		BSPLOG(bsp_log("_TIME_WAIT resend.\n"));
		tcp_send(s, 0, 1); /* just resend ack */
		break;
	    }
	} else {
	    BSPLOG(bsp_log("Unexpected segment from: %d.%d.%d.%d:%d\n",
			   r->ip_addr[0], r->ip_addr[1], r->ip_addr[3],
			   r->ip_addr[4], ntohs(tcp->src_port)));
	    send_reset(pkt, r);
	}
    }
    if (!queued)
	__pktbuf_free(pkt);
}


void
__tcp_poll(void)
{
    __enet_poll();
    __timer_poll();
}


int
__tcp_listen(tcp_socket_t *s, word port)
{
    BSPLOG(bsp_log("tcp_listen: s[%p] port[%x]\n", s, port));

    memset(s, 0, sizeof(tcp_socket_t));
    s->state    = _LISTEN;
    s->our_port = port;
    s->pkt.buf = (word *)s->pktbuf;
    s->pkt.bufsize = ETH_MAX_PKTLEN;
#if 0
    s->pkt.eth_hdr = (eth_header_t *)s->pkt.buf;
    s->pkt.ip_hdr  = (ip_header_t *)(s->pkt.eth_hdr + 1);
#else
    s->pkt.ip_hdr  = (ip_header_t *)s->pkt.buf;
#endif
    s->pkt.tcp_hdr = (tcp_header_t *)(s->pkt.ip_hdr + 1);

    s->next = tcp_list;

#if 1
    /* limit to one open socket at a time */
    if (s->next) {
	BSPLOG(bsp_log("tcp_listen: recursion error\n"));
	BSPLOG(while(1));
    }
#endif
    
    tcp_list = s;

    return 0;
}


/*
 * Block while waiting for all data to be transmitted.
 */
void
__tcp_drain(tcp_socket_t *s)
{
    BSPLOG(bsp_log("__tcp_drain.\n"));
    while (s->state != _CLOSED && s->data_bytes)
			__tcp_poll();
    BSPLOG(bsp_log("__tcp_drain done.\n"));
}



/*
 * Close the tcp connection.
 */
void
__tcp_close(tcp_socket_t *s)
{
    __tcp_drain(s);
    if (s->state == _ESTABLISHED || s->state == _SYN_RCVD) {
	BSPLOG(bsp_log("__tcp_close: going to _FIN_WAIT_1\n"));
	s->state = _FIN_WAIT_1;
	tcp_send(s, TCP_FLAG_ACK | TCP_FLAG_FIN, 0);
    } else if (s->state == _CLOSE_WAIT) {

	BSPLOG(bsp_log("__tcp_close: going to _LAST_ACK\n"));

	s->state = _LAST_ACK;
	tcp_send(s, TCP_FLAG_ACK | TCP_FLAG_FIN, 0);
    }
    free_rxlist(s);
}


/*
 * Wait for connection to be fully closed.
 */
void
__tcp_close_wait(tcp_socket_t *s)
{
    BSPLOG(bsp_log("__tcp_close_wait.\n"));
    while (s->state != _CLOSED)
			__tcp_poll();
    BSPLOG(bsp_log("__tcp_close_wait done.\n"));
}


/*
 * Read up to 'len' bytes without blocking.
 */
int
__tcp_read(tcp_socket_t *s, char *buf, int len)
{
    int          nread;
    pktbuf_t     *pkt;
    tcp_header_t *tcp;

    if (len <= 0 || s->rxcnt == 0)
	return 0;

    if (s->state != _ESTABLISHED && s->rxcnt == 0)
	return -1;

    nread = 0;
    while (len) {
	if (len < s->rxcnt) {
	    memcpy(buf, s->rxptr, len);
	    BSPLOG(bsp_log("tcp_read: read %d bytes.\n", len));
	    s->rxptr += len;
	    s->rxcnt -= len;
	    nread    += len;

	    BSPLOG(bsp_log("tcp_read: %d bytes left in rxlist head.\n", s->rxcnt));

	    break;
	} else {
	    memcpy(buf, s->rxptr, s->rxcnt);
	    BSPLOG(bsp_log("tcp_read: read %d bytes. pkt[%x] freed.\n", s->rxcnt, s->rxlist));
	    nread += s->rxcnt;
	    buf   += s->rxcnt;
	    len   -= s->rxcnt;

	    /* setup for next packet in list */
	    pkt = s->rxlist;
	    s->rxlist = pkt->next;
	    __pktbuf_free(pkt);

	    if ((pkt = s->rxlist) != NULL) {
		tcp = pkt->tcp_hdr;
		s->rxcnt = pkt->pkt_bytes - (tcp->hdr_len << 2);
		s->rxptr = ((char *)tcp)  + (tcp->hdr_len << 2);

		BSPLOG(bsp_log("tcp_read: next pkt[%x] has %d bytes.\n", s->rxlist, s->rxcnt));
	    } else {

		BSPLOG(bsp_log("tcp_read: no more data.\n"));

		s->rxcnt = 0;
		break;
	    }
	}
    }
    return nread;
}


int
__tcp_write(tcp_socket_t *s, char *buf, int len)
{
    tcp_header_t *tcp = s->pkt.tcp_hdr;

    if (len <= 0)
	return 0;

    if (s->state != _ESTABLISHED && s->state != _CLOSE_WAIT)
	return -1;

    if (s->data_bytes)
	return 0;

    if (len > MAX_TCP_DATA)
	len = MAX_TCP_DATA;

    memcpy(tcp + 1, buf, len);
    s->data_bytes = len;

    tcp_send(s, TCP_FLAG_ACK, 0);

    return len;
}