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[CCID3]: Wrap computation of RFC3390-initial rate into separate function

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The CCID 3 and TFRC specs (RFC 4342, RFC 3448, draft-3448bis) make frequent
reference to the computation of the RFC-3390 initial sending rate:

  1. Initial sending rate when RTT is known (RFC 4342, p. 6)
  2. Response to Idle/Application-Limited periods (RFC 4342, 5.1)

This warrants putting the code into its own function, for later code reuse.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2007-03-20 15:12:10 -03:00 committed by David S. Miller
parent 1761f7d7fe
commit a21f9f96cd
1 changed files with 18 additions and 7 deletions
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25
net/dccp/ccids/ccid3.c
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@ -81,6 +81,21 @@ static void ccid3_hc_tx_set_state(struct sock *sk,
hctx->ccid3hctx_state = state;
}
/*
* Compute the initial sending rate X_init according to RFC 3390:
* w_init = min(4 * MSS, max(2 * MSS, 4380 bytes))
* X_init = w_init / RTT
* For consistency with other parts of the code, X_init is scaled by 2^6.
*/
static inline u64 rfc3390_initial_rate(struct sock *sk)
{
const struct dccp_sock *dp = dccp_sk(sk);
const __u32 w_init = min(4 * dp->dccps_mss_cache,
max(2 * dp->dccps_mss_cache, 4380U));
return scaled_div(w_init << 6, ccid3_hc_tx_sk(sk)->ccid3hctx_rtt);
}
/*
* Recalculate t_ipi and delta (should be called whenever X changes)
*/
@ -469,20 +484,16 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
/*
* Larger Initial Windows [RFC 4342, sec. 5]
*/
__u32 w_init = min(4 * dp->dccps_mss_cache,
max(2 * dp->dccps_mss_cache, 4380U));
hctx->ccid3hctx_rtt = r_sample;
hctx->ccid3hctx_x = scaled_div(w_init << 6, r_sample);
hctx->ccid3hctx_x = rfc3390_initial_rate(sk);
hctx->ccid3hctx_t_ld = now;
ccid3_update_send_interval(hctx);
ccid3_pr_debug("%s(%p), s=%u, MSS=%u, w_init=%u, "
ccid3_pr_debug("%s(%p), s=%u, MSS=%u, "
"R_sample=%dus, X=%u\n", dccp_role(sk),
sk, hctx->ccid3hctx_s,
dp->dccps_mss_cache,
w_init,
(int)r_sample,
dp->dccps_mss_cache, (int)r_sample,
(unsigned)(hctx->ccid3hctx_x >> 6));
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);