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Commit d0c05fe4 authored by Gerrit Renker's avatar Gerrit Renker
Browse files

dccp ccid-3: Simplified handling of TX states 



Since CCIDs are only used during the established phase of a connection,
they have very little internal state; this specifically reduces to:

 * "no packet sent" if and only if s == 0, for the TX packet size s;

 * when the first packet has been sent (i.e. `s' > 0), the question is whether
   or not feedback has been received:
   - if a feedback packet is received, "feedback = yes" is set,
   - if the nofeedback timer expires,  "feedback = no"  is set.

Thus the CCID only needs to remember state about whether or not feedback
has been received. This is now implemented using a boolean flag, which is
toggled when a feedback packet arrives or the nofeedback timer expires.

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
parent f76fd327

net/dccp/ccids/ccid3.c

+6 −35
Original line number Diff line number Diff line
@@ -49,31 +49,6 @@ static int ccid3_debug; 
/*

 *	Transmitter Half-Connection Routines

 */

#ifdef CONFIG_IP_DCCP_CCID3_DEBUG

static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)

{

	static char *ccid3_state_names[] = {

	[TFRC_SSTATE_NO_SENT]  = "NO_SENT",

	[TFRC_SSTATE_NO_FBACK] = "NO_FBACK",

	[TFRC_SSTATE_FBACK]    = "FBACK",

	};



	return ccid3_state_names[state];

}

#endif



static void ccid3_hc_tx_set_state(struct sock *sk,

				  enum ccid3_hc_tx_states state)

{

	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

	enum ccid3_hc_tx_states oldstate = hctx->state;



	ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",

		       dccp_role(sk), sk, ccid3_tx_state_name(oldstate),

		       ccid3_tx_state_name(state));

	WARN_ON(state == oldstate);

	hctx->state = state;

}



/*

 * Compute the initial sending rate X_init in the manner of RFC 3390:
@@ -206,16 +181,15 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) 
		goto restart_timer;

	}



	ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,

		       ccid3_tx_state_name(hctx->state));

	ccid3_pr_debug("%s(%p) entry with%s feedback\n", dccp_role(sk), sk,

		       hctx->feedback ? "" : "out");



	/* Ignore and do not restart after leaving the established state */

	if ((1 << sk->sk_state) & ~(DCCPF_OPEN | DCCPF_PARTOPEN))

		goto out;



	/* Reset feedback state to "no feedback received" */

	if (hctx->state == TFRC_SSTATE_FBACK)

		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);

	hctx->feedback = false;



	/*

	 * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
@@ -290,7 +264,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb) 
	if (unlikely(skb->len == 0))

		return -EBADMSG;



	if (hctx->state == TFRC_SSTATE_NO_SENT) {

	if (hctx->s == 0) {

		sk_reset_timer(sk, &hctx->no_feedback_timer, (jiffies +

				usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));

		hctx->last_win_count   = 0;
@@ -324,8 +298,6 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb) 
		}

		ccid3_update_send_interval(hctx);



		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);



	} else {

		delay = ktime_us_delta(hctx->t_nom, now);

		ccid3_pr_debug("delay=%ld\n", (long)delay);
@@ -396,8 +368,8 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) 
	/*

	 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3

	 */

	if (hctx->state == TFRC_SSTATE_NO_FBACK) {

		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);

	if (!hctx->feedback) {

		hctx->feedback = true;



		if (hctx->t_rto == 0) {

			/*
@@ -502,7 +474,6 @@ static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk) 
{

	struct ccid3_hc_tx_sock *hctx = ccid_priv(ccid);



	hctx->state = TFRC_SSTATE_NO_SENT;

	hctx->hist  = NULL;

	setup_timer(&hctx->no_feedback_timer,

		    ccid3_hc_tx_no_feedback_timer, (unsigned long)sk);

net/dccp/ccids/ccid3.h

+2 −9
Original line number Diff line number Diff line
@@ -70,13 +70,6 @@ enum ccid3_options { 
	TFRC_OPT_RECEIVE_RATE	 = 194,

};



/* TFRC sender states */

enum ccid3_hc_tx_states {

	TFRC_SSTATE_NO_SENT = 1,

	TFRC_SSTATE_NO_FBACK,

	TFRC_SSTATE_FBACK,

};



/** struct ccid3_hc_tx_sock - CCID3 sender half-connection socket

 *

 * @x - Current sending rate in 64 * bytes per second
@@ -87,7 +80,7 @@ enum ccid3_hc_tx_states { 
 * @s - Packet size in bytes

 * @t_rto - Nofeedback Timer setting in usecs

 * @t_ipi - Interpacket (send) interval (RFC 3448, 4.6) in usecs

 * @state - Sender state, one of %ccid3_hc_tx_states

 * @feedback - Whether feedback has been received or not

 * @last_win_count - Last window counter sent

 * @t_last_win_count - Timestamp of earliest packet with

 *                     last_win_count value sent
@@ -105,7 +98,7 @@ struct ccid3_hc_tx_sock { 
	u32				t_rto;

	u32				t_ipi;

	u16				s;

	enum ccid3_hc_tx_states		state:8;

	bool				feedback:1;

	u8				last_win_count;

	ktime_t				t_last_win_count;

	struct timer_list		no_feedback_timer;