Commit a21f9f96 authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
Browse files

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



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: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: default avatarIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1761f7d7

net/dccp/ccids/ccid3.c

+18 −7
Original line number Diff line number Diff line
@@ -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);

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