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Commit 6224877b authored by Gerrit Renker's avatar Gerrit Renker
Browse files

tcp/dccp: Consolidate common code for RFC 3390 conversion 



This patch consolidates the code common to TCP and CCID-2:
 * TCP uses RFC 3390 in a packet-oriented manner (tcp_input.c) and
 * CCID-2 uses RFC 3390 in packet-oriented manner (RFC 4341).

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
parent b25b0c60

include/net/tcp.h

+15 −0
Original line number Diff line number Diff line
@@ -782,6 +782,21 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk) 
/* Use define here intentionally to get WARN_ON location shown at the caller */

#define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)



/*

 * Convert RFC3390 larger initial windows into an equivalent number of packets.

 *

 * John Heffner states:

 *

 *	The RFC specifies a window of no more than 4380 bytes

 *	unless 2*MSS > 4380.  Reading the pseudocode in the RFC

 *	is a bit misleading because they use a clamp at 4380 bytes

 *	rather than a multiplier in the relevant range.

 */

static inline u32 rfc3390_bytes_to_packets(const u32 bytes)

{

	return bytes <= 1095 ? 4 : (bytes > 1460 ? 2 : 3);

}



extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);

extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);

net/dccp/ccids/ccid2.c

+2 −6
Original line number Diff line number Diff line
@@ -596,12 +596,8 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk) 
	/* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */

	hctx->ssthresh = ~0U;



	/*

	 * RFC 4341, 5: "The cwnd parameter is initialized to at most four

	 * packets for new connections, following the rules from [RFC3390]".

	 * We need to convert the bytes of RFC3390 into the packets of RFC 4341.

	 */

	hctx->cwnd = clamp(4380U / dp->dccps_mss_cache, 2U, 4U);

	/* Use larger initial windows (RFC 3390, rfc2581bis) */

	hctx->cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);



	/* Make sure that Ack Ratio is enabled and within bounds. */

	max_ratio = DIV_ROUND_UP(hctx->cwnd, 2);

net/ipv4/tcp_input.c

+2 −15
Original line number Diff line number Diff line
@@ -811,25 +811,12 @@ void tcp_update_metrics(struct sock *sk) 
	}

}



/* Numbers are taken from RFC3390.

 *

 * John Heffner states:

 *

 *	The RFC specifies a window of no more than 4380 bytes

 *	unless 2*MSS > 4380.  Reading the pseudocode in the RFC

 *	is a bit misleading because they use a clamp at 4380 bytes

 *	rather than use a multiplier in the relevant range.

 */

__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)

{

	__u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);



	if (!cwnd) {

		if (tp->mss_cache > 1460)

			cwnd = 2;

		else

			cwnd = (tp->mss_cache > 1095) ? 3 : 4;

	}

	if (!cwnd)

		cwnd = rfc3390_bytes_to_packets(tp->mss_cache);

	return min_t(__u32, cwnd, tp->snd_cwnd_clamp);

}