llc_conn.c

linux 内核源代码

/*
 * llc_conn.c - Driver routines for connection component.
 *
 * Copyright (c) 1997 by Procom Technology, Inc.
 *		 2001-2003 by Arnaldo Carvalho de Melo <[e-mail]>
 *
 * This program can be redistributed or modified under the terms of the
 * GNU General Public License as published by the Free Software Foundation.
 * This program is distributed without any warranty or implied warranty
 * of merchantability or fitness for a particular purpose.
 *
 * See the GNU General Public License for more details.
 */

#include <linux/init.h>
#include <net/llc_sap.h>
#include <net/llc_conn.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <net/llc_c_ev.h>
#include <net/llc_c_ac.h>
#include <net/llc_c_st.h>
#include <net/llc_pdu.h>

#if 0
#define dprintk(args...) printk(KERN_DEBUG args)
#else
#define dprintk(args...)
#endif

static int llc_find_offset(int state, int ev_type);
static void llc_conn_send_pdus(struct sock *sk);
static int llc_conn_service(struct sock *sk, struct sk_buff *skb);
static int llc_exec_conn_trans_actions(struct sock *sk,
				       struct llc_conn_state_trans *trans,
				       struct sk_buff *ev);
static struct llc_conn_state_trans *llc_qualify_conn_ev(struct sock *sk,
							struct sk_buff *skb);

/* Offset table on connection states transition diagram */
static int llc_offset_table[NBR_CONN_STATES][NBR_CONN_EV];

int sysctl_llc2_ack_timeout = LLC2_ACK_TIME * HZ;
int sysctl_llc2_p_timeout = LLC2_P_TIME * HZ;
int sysctl_llc2_rej_timeout = LLC2_REJ_TIME * HZ;
int sysctl_llc2_busy_timeout = LLC2_BUSY_TIME * HZ;

/**
 *	llc_conn_state_process - sends event to connection state machine
 *	@sk: connection
 *	@skb: occurred event
 *
 *	Sends an event to connection state machine. After processing event
 *	(executing it's actions and changing state), upper layer will be
 *	indicated or confirmed, if needed. Returns 0 for success, 1 for
 *	failure. The socket lock has to be held before calling this function.
 */
int llc_conn_state_process(struct sock *sk, struct sk_buff *skb)
{
	int rc;
	struct llc_sock *llc = llc_sk(skb->sk);
	struct llc_conn_state_ev *ev = llc_conn_ev(skb);

	/*
	 * We have to hold the skb, because llc_conn_service will kfree it in
	 * the sending path and we need to look at the skb->cb, where we encode
	 * llc_conn_state_ev.
	 */
	skb_get(skb);
	ev->ind_prim = ev->cfm_prim = 0;
	/*
	 * Send event to state machine
	 */
	rc = llc_conn_service(skb->sk, skb);
	if (unlikely(rc != 0)) {
		printk(KERN_ERR "%s: llc_conn_service failed\n", __FUNCTION__);
		goto out_kfree_skb;
	}

	if (unlikely(!ev->ind_prim && !ev->cfm_prim)) {
		/* indicate or confirm not required */
		/* XXX this is not very pretty, perhaps we should store
		 * XXX indicate/confirm-needed state in the llc_conn_state_ev
		 * XXX control block of the SKB instead? -DaveM
		 */
		if (!skb->next)
			goto out_kfree_skb;
		goto out_skb_put;
	}

	if (unlikely(ev->ind_prim && ev->cfm_prim)) /* Paranoia */
		skb_get(skb);

	switch (ev->ind_prim) {
	case LLC_DATA_PRIM:
		llc_save_primitive(sk, skb, LLC_DATA_PRIM);
		if (unlikely(sock_queue_rcv_skb(sk, skb))) {
			/*
			 * shouldn't happen
			 */
			printk(KERN_ERR "%s: sock_queue_rcv_skb failed!\n",
			       __FUNCTION__);
			kfree_skb(skb);
		}
		break;
	case LLC_CONN_PRIM:
		/*
		 * Can't be sock_queue_rcv_skb, because we have to leave the
		 * skb->sk pointing to the newly created struct sock in
		 * llc_conn_handler. -acme
		 */
		skb_queue_tail(&sk->sk_receive_queue, skb);
		sk->sk_state_change(sk);
		break;
	case LLC_DISC_PRIM:
		sock_hold(sk);
		if (sk->sk_type == SOCK_STREAM &&
		    sk->sk_state == TCP_ESTABLISHED) {
			sk->sk_shutdown       = SHUTDOWN_MASK;
			sk->sk_socket->state  = SS_UNCONNECTED;
			sk->sk_state          = TCP_CLOSE;
			if (!sock_flag(sk, SOCK_DEAD)) {
				sock_set_flag(sk, SOCK_DEAD);
				sk->sk_state_change(sk);
			}
		}
		kfree_skb(skb);
		sock_put(sk);
		break;
	case LLC_RESET_PRIM:
		/*
		 * FIXME:
		 * RESET is not being notified to upper layers for now
		 */
		printk(KERN_INFO "%s: received a reset ind!\n", __FUNCTION__);
		kfree_skb(skb);
		break;
	default:
		if (ev->ind_prim) {
			printk(KERN_INFO "%s: received unknown %d prim!\n",
				__FUNCTION__, ev->ind_prim);
			kfree_skb(skb);
		}
		/* No indication */
		break;
	}

	switch (ev->cfm_prim) {
	case LLC_DATA_PRIM:
		if (!llc_data_accept_state(llc->state))
			sk->sk_write_space(sk);
		else
			rc = llc->failed_data_req = 1;
		break;
	case LLC_CONN_PRIM:
		if (sk->sk_type == SOCK_STREAM &&
		    sk->sk_state == TCP_SYN_SENT) {
			if (ev->status) {
				sk->sk_socket->state = SS_UNCONNECTED;
				sk->sk_state         = TCP_CLOSE;
			} else {
				sk->sk_socket->state = SS_CONNECTED;
				sk->sk_state         = TCP_ESTABLISHED;
			}
			sk->sk_state_change(sk);
		}
		break;
	case LLC_DISC_PRIM:
		sock_hold(sk);
		if (sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_CLOSING) {
			sk->sk_socket->state = SS_UNCONNECTED;
			sk->sk_state         = TCP_CLOSE;
			sk->sk_state_change(sk);
		}
		sock_put(sk);
		break;
	case LLC_RESET_PRIM:
		/*
		 * FIXME:
		 * RESET is not being notified to upper layers for now
		 */
		printk(KERN_INFO "%s: received a reset conf!\n", __FUNCTION__);
		break;
	default:
		if (ev->cfm_prim) {
			printk(KERN_INFO "%s: received unknown %d prim!\n",
					__FUNCTION__, ev->cfm_prim);
			break;
		}
		goto out_skb_put; /* No confirmation */
	}
out_kfree_skb:
	kfree_skb(skb);
out_skb_put:
	kfree_skb(skb);
	return rc;
}

void llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb)
{
	/* queue PDU to send to MAC layer */
	skb_queue_tail(&sk->sk_write_queue, skb);
	llc_conn_send_pdus(sk);
}

/**
 *	llc_conn_rtn_pdu - sends received data pdu to upper layer
 *	@sk: Active connection
 *	@skb: Received data frame
 *
 *	Sends received data pdu to upper layer (by using indicate function).
 *	Prepares service parameters (prim and prim_data). calling indication
 *	function will be done in llc_conn_state_process.
 */
void llc_conn_rtn_pdu(struct sock *sk, struct sk_buff *skb)
{
	struct llc_conn_state_ev *ev = llc_conn_ev(skb);

	ev->ind_prim = LLC_DATA_PRIM;
}

/**
 *	llc_conn_resend_i_pdu_as_cmd - resend all all unacknowledged I PDUs
 *	@sk: active connection
 *	@nr: NR
 *	@first_p_bit: p_bit value of first pdu
 *
 *	Resend all unacknowledged I PDUs, starting with the NR; send first as
 *	command PDU with P bit equal first_p_bit; if more than one send
 *	subsequent as command PDUs with P bit equal zero (0).
 */
void llc_conn_resend_i_pdu_as_cmd(struct sock *sk, u8 nr, u8 first_p_bit)
{
	struct sk_buff *skb;
	struct llc_pdu_sn *pdu;
	u16 nbr_unack_pdus;
	struct llc_sock *llc;
	u8 howmany_resend = 0;

	llc_conn_remove_acked_pdus(sk, nr, &nbr_unack_pdus);
	if (!nbr_unack_pdus)
		goto out;
	/*
	 * Process unack PDUs only if unack queue is not empty; remove
	 * appropriate PDUs, fix them up, and put them on mac_pdu_q.
	 */
	llc = llc_sk(sk);

	while ((skb = skb_dequeue(&llc->pdu_unack_q)) != NULL) {
		pdu = llc_pdu_sn_hdr(skb);
		llc_pdu_set_cmd_rsp(skb, LLC_PDU_CMD);
		llc_pdu_set_pf_bit(skb, first_p_bit);
		skb_queue_tail(&sk->sk_write_queue, skb);
		first_p_bit = 0;
		llc->vS = LLC_I_GET_NS(pdu);
		howmany_resend++;
	}
	if (howmany_resend > 0)
		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
	/* any PDUs to re-send are queued up; start sending to MAC */
	llc_conn_send_pdus(sk);
out:;
}

/**
 *	llc_conn_resend_i_pdu_as_rsp - Resend all unacknowledged I PDUs
 *	@sk: active connection.
 *	@nr: NR
 *	@first_f_bit: f_bit value of first pdu.
 *
 *	Resend all unacknowledged I PDUs, starting with the NR; send first as
 *	response PDU with F bit equal first_f_bit; if more than one send
 *	subsequent as response PDUs with F bit equal zero (0).
 */
void llc_conn_resend_i_pdu_as_rsp(struct sock *sk, u8 nr, u8 first_f_bit)
{
	struct sk_buff *skb;
	u16 nbr_unack_pdus;
	struct llc_sock *llc = llc_sk(sk);
	u8 howmany_resend = 0;

	llc_conn_remove_acked_pdus(sk, nr, &nbr_unack_pdus);
	if (!nbr_unack_pdus)
		goto out;
	/*
	 * Process unack PDUs only if unack queue is not empty; remove
	 * appropriate PDUs, fix them up, and put them on mac_pdu_q
	 */
	while ((skb = skb_dequeue(&llc->pdu_unack_q)) != NULL) {
		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);

		llc_pdu_set_cmd_rsp(skb, LLC_PDU_RSP);
		llc_pdu_set_pf_bit(skb, first_f_bit);
		skb_queue_tail(&sk->sk_write_queue, skb);
		first_f_bit = 0;
		llc->vS = LLC_I_GET_NS(pdu);
		howmany_resend++;
	}
	if (howmany_resend > 0)
		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
	/* any PDUs to re-send are queued up; start sending to MAC */
	llc_conn_send_pdus(sk);
out:;
}

/**
 *	llc_conn_remove_acked_pdus - Removes acknowledged pdus from tx queue
 *	@sk: active connection
 *	nr: NR
 *	how_many_unacked: size of pdu_unack_q after removing acked pdus
 *
 *	Removes acknowledged pdus from transmit queue (pdu_unack_q). Returns
 *	the number of pdus that removed from queue.
 */
int llc_conn_remove_acked_pdus(struct sock *sk, u8 nr, u16 *how_many_unacked)
{
	int pdu_pos, i;
	struct sk_buff *skb;
	struct llc_pdu_sn *pdu;
	int nbr_acked = 0;
	struct llc_sock *llc = llc_sk(sk);
	int q_len = skb_queue_len(&llc->pdu_unack_q);

	if (!q_len)
		goto out;
	skb = skb_peek(&llc->pdu_unack_q);
	pdu = llc_pdu_sn_hdr(skb);

	/* finding position of last acked pdu in queue */
	pdu_pos = ((int)LLC_2_SEQ_NBR_MODULO + (int)nr -
			(int)LLC_I_GET_NS(pdu)) % LLC_2_SEQ_NBR_MODULO;

	for (i = 0; i < pdu_pos && i < q_len; i++) {
		skb = skb_dequeue(&llc->pdu_unack_q);
		if (skb)
			kfree_skb(skb);
		nbr_acked++;
	}
out:
	*how_many_unacked = skb_queue_len(&llc->pdu_unack_q);
	return nbr_acked;
}

/**
 *	llc_conn_send_pdus - Sends queued PDUs
 *	@sk: active connection
 *
 *	Sends queued pdus to MAC layer for transmission.
 */
static void llc_conn_send_pdus(struct sock *sk)
{
	struct sk_buff *skb;

	while ((skb = skb_dequeue(&sk->sk_write_queue)) != NULL) {
		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);

		if (LLC_PDU_TYPE_IS_I(pdu) &&
		    !(skb->dev->flags & IFF_LOOPBACK)) {
			struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);

			skb_queue_tail(&llc_sk(sk)->pdu_unack_q, skb);
			if (!skb2)
				break;
			skb = skb2;
		}
		dev_queue_xmit(skb);
	}
}

/**
 *	llc_conn_service - finds transition and changes state of connection
 *	@sk: connection
 *	@skb: happened event
 *
 *	This function finds transition that matches with happened event, then
 *	executes related actions and finally changes state of connection.
 *	Returns 0 for success, 1 for failure.
 */
static int llc_conn_service(struct sock *sk, struct sk_buff *skb)
{
	int rc = 1;
	struct llc_sock *llc = llc_sk(sk);
	struct llc_conn_state_trans *trans;

	if (llc->state > NBR_CONN_STATES)
		goto out;
	rc = 0;
	trans = llc_qualify_conn_ev(sk, skb);
	if (trans) {
		rc = llc_exec_conn_trans_actions(sk, trans, skb);
		if (!rc && trans->next_state != NO_STATE_CHANGE) {
			llc->state = trans->next_state;
			if (!llc_data_accept_state(llc->state))
				sk->sk_state_change(sk);
		}
	}
out:
	return rc;
}

/**
 *	llc_qualify_conn_ev - finds transition for event
 *	@sk: connection
 *	@skb: happened event
 *
 *	This function finds transition that matches with happened event.
 *	Returns pointer to found transition on success, %NULL otherwise.
 */
static struct llc_conn_state_trans *llc_qualify_conn_ev(struct sock *sk,
							struct sk_buff *skb)
{
	struct llc_conn_state_trans **next_trans;
	llc_conn_ev_qfyr_t *next_qualifier;
	struct llc_conn_state_ev *ev = llc_conn_ev(skb);
	struct llc_sock *llc = llc_sk(sk);
	struct llc_conn_state *curr_state =
					&llc_conn_state_table[llc->state - 1];

	/* search thru events for this state until
	 * list exhausted or until no more
	 */
	for (next_trans = curr_state->transitions +
		llc_find_offset(llc->state - 1, ev->type);
	     (*next_trans)->ev; next_trans++) {
		if (!((*next_trans)->ev)(sk, skb)) {
			/* got POSSIBLE event match; the event may require
			 * qualification based on the values of a number of
			 * state flags; if all qualifications are met (i.e.,
			 * if all qualifying functions return success, or 0,
			 * then this is THE event we're looking for
			 */
			for (next_qualifier = (*next_trans)->ev_qualifiers;
			     next_qualifier && *next_qualifier &&
			     !(*next_qualifier)(sk, skb); next_qualifier++)
				/* nothing */;
			if (!next_qualifier || !*next_qualifier)
				/* all qualifiers executed successfully; this is
				 * our transition; return it so we can perform
				 * the associated actions & change the state
				 */
				return *next_trans;
		}
	}
	return NULL;
}

/**
 *	llc_exec_conn_trans_actions - executes related actions
 *	@sk: connection
 *	@trans: transition that it's actions must be performed
 *	@skb: event
 *
 *	Executes actions that is related to happened event. Returns 0 for
 *	success, 1 to indicate failure of at least one action.
 */
static int llc_exec_conn_trans_actions(struct sock *sk,
				       struct llc_conn_state_trans *trans,
				       struct sk_buff *skb)
{
	int rc = 0;
	llc_conn_action_t *next_action;

	for (next_action = trans->ev_actions;
	     next_action && *next_action; next_action++) {
		int rc2 = (*next_action)(sk, skb);

		if (rc2 == 2) {
			rc = rc2;
			break;
		} else if (rc2)
			rc = 1;
	}
	return rc;
}

/**
 *	__llc_lookup_established - Finds connection for the remote/local sap/mac