dccp ccid-2: use new interface to refactor dynamic negotiation

Using the new function dccp_feat_get_nn_next_val(), this simplifies existing
code to not trigger a new negotiation if the requested new value equals the
old one.
---
 net/dccp/ccids/ccid2.c |   22 +++++-----------------
 net/dccp/feat.c        |    5 +++--
 2 files changed, 8 insertions(+), 19 deletions(-)

--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -815,10 +815,11 @@ int dccp_feat_signal_nn_change(struct so
 	    !dccp_feat_is_valid_nn_val(feat, nn_val))
 		return -EINVAL;
 
+	if (nn_val == dccp_feat_get_nn_next_val(sk, feat))
+		return 0;	/* already set or negotiation under way */
+
 	entry = dccp_feat_list_lookup(fn, feat, 1);
 	if (entry != NULL) {
-		if (entry->val.nn == fval.nn)
-			return 0;
 		dccp_pr_debug("Clobbering existing NN entry %llu -> %llu\n",
 			      (unsigned long long)entry->val.nn,
 			      (unsigned long long)nn_val);
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -102,27 +102,15 @@ static void ccid2_change_l_ack_ratio(str
 		DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
 		val = max_ratio;
 	}
-	if (val > DCCPF_ACK_RATIO_MAX)
-		val = DCCPF_ACK_RATIO_MAX;
-
-	if (val == ccid2_ack_ratio_next(sk))
-		return;
-
-	ccid2_pr_debug("changing local ack ratio to %u\n", val);
-	dccp_feat_signal_nn_change(sk, DCCPF_ACK_RATIO, val);
+	dccp_feat_signal_nn_change(sk, DCCPF_ACK_RATIO,
+				   min_t(u32, val, DCCPF_ACK_RATIO_MAX));
 }
 
 static void ccid2_change_l_seq_window(struct sock *sk, u64 val)
 {
-	struct dccp_sock *dp = dccp_sk(sk);
-
-	if (val < DCCPF_SEQ_WMIN)
-		val = DCCPF_SEQ_WMIN;
-	if (val > DCCPF_SEQ_WMAX)
-		val = DCCPF_SEQ_WMAX;
-
-	if (val != dp->dccps_l_seq_win)
-		dccp_feat_signal_nn_change(sk, DCCPF_SEQUENCE_WINDOW, val);
+	dccp_feat_signal_nn_change(sk, DCCPF_SEQUENCE_WINDOW,
+				   clamp_val(val, DCCPF_SEQ_WMIN,
+						  DCCPF_SEQ_WMAX));
 }
 
 static void ccid2_hc_tx_rto_expire(unsigned long data)