While fixing a sparse warning in DCCP I found that the same code (conversion of
RFC3390 bytes-to-packets) appears identically in 3 different places:
* TCP uses RFC 3390 in a packet-oriented manner (tcp_input.c);
* CCID-2 uses RFC 3390 in packet-oriented manner (RFC 4341);
* CCID-3 uses RFC 3390 in a packet-oriented manner
(RFC 4342, rfc3448bis).
This patch consolidates the code common to both TCP and DCCP.
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
include/net/tcp.h | 14 ++++++++++++++
net/dccp/ccids/ccid2.c | 8 ++------
net/dccp/ccids/ccid3.c | 5 +----
net/ipv4/tcp_input.c | 17 ++---------------
4 files changed, 19 insertions(+), 25 deletions(-)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -809,25 +809,12 @@ 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);
}
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -770,6 +770,21 @@ static inline __u32 tcp_current_ssthresh
/* 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);
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -598,12 +598,8 @@ static int ccid2_hc_tx_init(struct ccid
/* 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 = min(4U, max(2U, 4380U / dp->dccps_mss_cache));
+ /* 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);
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -81,15 +81,12 @@ static void ccid3_hc_tx_set_state(struct
*
* X_init = min(4 * s, max(2 * s, 4380 bytes)) / RTT
*
- * Note that RFC 3390 uses MSS, RFC 4342 refers to RFC 3390, and rfc3448bis
- * (rev-02) clarifies the use of RFC 3390 with regard to the above formula.
* 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 ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
- const u32 w_init = min_t(u32, 4 * hctx->s,
- max_t(u32, 2 * hctx->s, 4380U));
+ const u32 w_init = hctx->s * rfc3390_bytes_to_packets(hctx->s);
return scaled_div(w_init << 6, hctx->rtt);
}
--
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