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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2010-08-29 19:23:12 +0000
committerDavid S. Miller <davem@davemloft.net>2010-08-30 13:45:26 -0700
commit22b71c8f4f3db8df92f5e7b081c265bc56c0bd2f (patch)
treeb913f63369b09ad703ed52a42b367455785ef3af
parentd26eeb07fd02de31848b59d19687daff0e93532f (diff)
downloadop-kernel-dev-22b71c8f4f3db8df92f5e7b081c265bc56c0bd2f.zip
op-kernel-dev-22b71c8f4f3db8df92f5e7b081c265bc56c0bd2f.tar.gz
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>
-rw-r--r--include/net/tcp.h15
-rw-r--r--net/dccp/ccids/ccid2.c8
-rw-r--r--net/ipv4/tcp_input.c17
3 files changed, 19 insertions, 21 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index df6a2eb..a640221 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -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);
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 8c95813..b9c942a 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -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);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e663b78..1bc87a0 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -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);
}
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