[CCID2]: Larger initial windows also for CCID2

RFC 4341, sec. 5 states that "The cwnd parameter is initialized to at most
four packets for new connections, following the rules from [RFC3390]", which
is implemented by this patch.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 5 deletions

diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index ef19fb834299..9c5b6c73f7c9 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -741,15 +741,25 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
 {
         struct ccid2_hc_tx_sock *hctx = ccid_priv(ccid);
+        struct dccp_sock *dp = dccp_sk(sk);
+        u32 max_ratio;
 
-        ccid2_change_cwnd(hctx, 1);
-        /* Initialize ssthresh to infinity.  This means that we will exit the
-         * initial slow-start after the first packet loss.  This is what we
-         * want.
-         */
+        /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
         hctx->ccid2hctx_ssthresh  = ~0;
         hctx->ccid2hctx_numdupack = 3;
 
+        /*
+         * 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->ccid2hctx_cwnd = min(4U, max(2U, 4380U / dp->dccps_mss_cache));
+
+        /* Make sure that Ack Ratio is enabled and within bounds. */
+        max_ratio = DIV_ROUND_UP(hctx->ccid2hctx_cwnd, 2);
+        if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
+                dp->dccps_l_ack_ratio = max_ratio;
+
         /* XXX init ~ to window size... */
         if (ccid2_hc_tx_alloc_seq(hctx))
                 return -ENOMEM;