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tcp/dccp: Consolidate common code for RFC 3390 conversion 

This patch consolidates initial-window 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: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2010-08-29 19:23:12 +00:00 committed by David S. Miller
parent d26eeb07fd
commit 22b71c8f4f
3 changed files with 19 additions and 21 deletions
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15
include/net/tcp.h
View File

@ -779,6 +779,21 @@ 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 RFC 3390 larger initial window 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 smss)
{
return smss <= 1095 ? 4 : (smss > 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);

8
net/dccp/ccids/ccid2.c
View File

@ -641,12 +641,8 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
/* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
hc->tx_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.
*/
hc->tx_cwnd = clamp(4380U / dp->dccps_mss_cache, 2U, 4U);
/* Use larger initial windows (RFC 4341, section 5). */
hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
/* Make sure that Ack Ratio is enabled and within bounds. */
max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);

17
net/ipv4/tcp_input.c
View File

@ -805,25 +805,12 @@ 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);
}