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dccp ccid-3: remove dead states
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This patch is thanks to an investigation by Leandro Sales de Melo and his
colleagues. They worked out two state diagrams which highlight the fact that
the xxx_TERM states in CCID-3/4 are in fact not necessary.

And this can be confirmed by in turn looking at the code: the xxx_TERM states
are only ever set in ccid3_hc_{rx,tx}_exit(): when CCID-3 sets the state
to xxx_TERM, it is at a time where no more processing should be going on,
hence it is not necessary to introduce a dedicated exit state - this is already
implied by unloading the CCID.

Signed-off-by: Gerrit Renker <[email protected]>
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Gerrit Renker committed Sep 21, 2010
1 parent a18213d commit 80763df
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Showing 2 changed files with 9 additions and 30 deletions.
37 changes: 9 additions & 28 deletions net/dccp/ccids/ccid3.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,6 @@ static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
[TFRC_SSTATE_NO_SENT] = "NO_SENT",
[TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
[TFRC_SSTATE_FBACK] = "FBACK",
[TFRC_SSTATE_TERM] = "TERM",
};

return ccid3_state_names[state];
Expand Down Expand Up @@ -208,10 +207,13 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
ccid3_pr_debug("%s(%p, state=%s) - entry\n", dccp_role(sk), sk,
ccid3_tx_state_name(hc->tx_state));

/* 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 (hc->tx_state == TFRC_SSTATE_FBACK)
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
else if (hc->tx_state != TFRC_SSTATE_NO_FBACK)
goto out;

/*
* Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
Expand Down Expand Up @@ -287,8 +289,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
if (unlikely(skb->len == 0))
return -EBADMSG;

switch (hc->tx_state) {
case TFRC_SSTATE_NO_SENT:
if (hc->tx_state == TFRC_SSTATE_NO_SENT) {
sk_reset_timer(sk, &hc->tx_no_feedback_timer, (jiffies +
usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
hc->tx_last_win_count = 0;
Expand Down Expand Up @@ -323,9 +324,8 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
ccid3_update_send_interval(hc);

ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
break;
case TFRC_SSTATE_NO_FBACK:
case TFRC_SSTATE_FBACK:

} else {
delay = ktime_us_delta(hc->tx_t_nom, now);
ccid3_pr_debug("delay=%ld\n", (long)delay);
/*
Expand All @@ -340,10 +340,6 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
return (u32)delay / USEC_PER_MSEC;

ccid3_hc_tx_update_win_count(hc, now);
break;
case TFRC_SSTATE_TERM:
DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
return -EINVAL;
}

/* prepare to send now (add options etc.) */
Expand Down Expand Up @@ -379,11 +375,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
return;
/* ... and only in the established state */
if (hc->tx_state != TFRC_SSTATE_FBACK &&
hc->tx_state != TFRC_SSTATE_NO_FBACK)
return;

/*
* Locate the acknowledged packet in the TX history.
*
Expand Down Expand Up @@ -529,9 +520,7 @@ static void ccid3_hc_tx_exit(struct sock *sk)
{
struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);

ccid3_hc_tx_set_state(sk, TFRC_SSTATE_TERM);
sk_stop_timer(sk, &hc->tx_no_feedback_timer);

tfrc_tx_hist_purge(&hc->tx_hist);
}

Expand Down Expand Up @@ -590,7 +579,6 @@ static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
static const char *const ccid3_rx_state_names[] = {
[TFRC_RSTATE_NO_DATA] = "NO_DATA",
[TFRC_RSTATE_DATA] = "DATA",
[TFRC_RSTATE_TERM] = "TERM",
};

return ccid3_rx_state_names[state];
Expand All @@ -616,14 +604,9 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
{
struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
struct dccp_sock *dp = dccp_sk(sk);
ktime_t now;
ktime_t now = ktime_get_real();
s64 delta = 0;

if (unlikely(hc->rx_state == TFRC_RSTATE_TERM))
return;

now = ktime_get_real();

switch (fbtype) {
case CCID3_FBACK_INITIAL:
hc->rx_x_recv = 0;
Expand Down Expand Up @@ -827,8 +810,6 @@ static void ccid3_hc_rx_exit(struct sock *sk)
{
struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);

ccid3_hc_rx_set_state(sk, TFRC_RSTATE_TERM);

tfrc_rx_hist_purge(&hc->rx_hist);
tfrc_lh_cleanup(&hc->rx_li_hist);
}
Expand Down
2 changes: 0 additions & 2 deletions net/dccp/ccids/ccid3.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,6 @@ enum ccid3_hc_tx_states {
TFRC_SSTATE_NO_SENT = 1,
TFRC_SSTATE_NO_FBACK,
TFRC_SSTATE_FBACK,
TFRC_SSTATE_TERM,
};

/**
Expand Down Expand Up @@ -130,7 +129,6 @@ static inline struct ccid3_hc_tx_sock *ccid3_hc_tx_sk(const struct sock *sk)
enum ccid3_hc_rx_states {
TFRC_RSTATE_NO_DATA = 1,
TFRC_RSTATE_DATA,
TFRC_RSTATE_TERM = 127,
};

/**
Expand Down

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