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>
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@ -779,6 +779,21 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
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/* Use define here intentionally to get WARN_ON location shown at the caller */
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#define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
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/*
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* Convert RFC 3390 larger initial window into an equivalent number of packets.
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*
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* John Heffner states:
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*
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* The RFC specifies a window of no more than 4380 bytes
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* unless 2*MSS > 4380. Reading the pseudocode in the RFC
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* is a bit misleading because they use a clamp at 4380 bytes
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* rather than a multiplier in the relevant range.
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*/
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static inline u32 rfc3390_bytes_to_packets(const u32 smss)
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{
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return smss <= 1095 ? 4 : (smss > 1460 ? 2 : 3);
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}
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extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
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extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);
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@ -641,12 +641,8 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
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/* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
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hc->tx_ssthresh = ~0U;
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/*
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* RFC 4341, 5: "The cwnd parameter is initialized to at most four
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* packets for new connections, following the rules from [RFC3390]".
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* We need to convert the bytes of RFC3390 into the packets of RFC 4341.
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*/
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hc->tx_cwnd = clamp(4380U / dp->dccps_mss_cache, 2U, 4U);
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/* Use larger initial windows (RFC 4341, section 5). */
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hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
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/* Make sure that Ack Ratio is enabled and within bounds. */
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max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
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@ -805,25 +805,12 @@ void tcp_update_metrics(struct sock *sk)
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}
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}
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/* Numbers are taken from RFC3390.
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*
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* John Heffner states:
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*
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* The RFC specifies a window of no more than 4380 bytes
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* unless 2*MSS > 4380. Reading the pseudocode in the RFC
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* is a bit misleading because they use a clamp at 4380 bytes
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* rather than use a multiplier in the relevant range.
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*/
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__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
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{
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__u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
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if (!cwnd) {
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if (tp->mss_cache > 1460)
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cwnd = 2;
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else
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cwnd = (tp->mss_cache > 1095) ? 3 : 4;
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}
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if (!cwnd)
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cwnd = rfc3390_bytes_to_packets(tp->mss_cache);
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return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
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}
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