2 files changed, 23 insertions, 8 deletions

diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index a62fdf7a6bf..cdb64922ba1 100644
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -1,18 +1,20 @@
 DCCP protocol
-============
+=============
 
 
 Contents
 ========
-
 - Introduction
 - Missing features
 - Socket options
+- Sysctl variables
+- IOCTLs
+- Other tunables
 - Notes
 
+
 Introduction
 ============
-
 Datagram Congestion Control Protocol (DCCP) is an unreliable, connection
 oriented protocol designed to solve issues present in UDP and TCP, particularly
 for real-time and multimedia (streaming) traffic.
@@ -29,9 +31,9 @@ It has a base protocol and pluggable congestion control IDs (CCIDs).
 DCCP is a Proposed Standard (RFC 2026), and the homepage for DCCP as a protocol
 is at http://www.ietf.org/html.charters/dccp-charter.html
 
+
 Missing features
 ================
-
 The Linux DCCP implementation does not currently support all the features that are
 specified in RFCs 4340...42.
 
@@ -45,7 +47,6 @@ http://linux-net.osdl.org/index.php/DCCP_Testing#Experimental_DCCP_source_tree
 
 Socket options
 ==============
-
 DCCP_SOCKOPT_SERVICE sets the service. The specification mandates use of
 service codes (RFC 4340, sec. 8.1.2); if this socket option is not set,
 the socket will fall back to 0 (which means that no meaningful service code
@@ -112,6 +113,7 @@ DCCP_SOCKOPT_CCID_TX_INFO
 On unidirectional connections it is useful to close the unused half-connection
 via shutdown (SHUT_WR or SHUT_RD): this will reduce per-packet processing costs.
 
+
 Sysctl variables
 ================
 Several DCCP default parameters can be managed by the following sysctls
@@ -155,15 +157,27 @@ sync_ratelimit = 125 ms
         sequence-invalid packets on the same socket (RFC 4340, 7.5.4). The unit
         of this parameter is milliseconds; a value of 0 disables rate-limiting.
 
+
 IOCTLS
 ======
 FIONREAD
         Works as in udp(7): returns in the `int' argument pointer the size of
         the next pending datagram in bytes, or 0 when no datagram is pending.
 
+
+Other tunables
+==============
+Per-route rto_min support
+        CCID-2 supports the RTAX_RTO_MIN per-route setting for the minimum value
+        of the RTO timer. This setting can be modified via the 'rto_min' option
+        of iproute2; for example:
+                > ip route change 10.0.0.0/24   rto_min 250j dev wlan0
+                > ip route add    10.0.0.254/32 rto_min 800j dev wlan0
+                > ip route show dev wlan0
+
+
 Notes
 =====
-
 DCCP does not travel through NAT successfully at present on many boxes. This is
 because the checksum covers the pseudo-header as per TCP and UDP. Linux NAT
 support for DCCP has been added.
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index b9c942a09c9..dc18172b1e5 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -325,8 +325,9 @@ static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
                 hc->tx_srtt = m << 3;
                 hc->tx_mdev = m << 1;
 
-                hc->tx_mdev_max = max(TCP_RTO_MIN, hc->tx_mdev);
+                hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
                 hc->tx_rttvar   = hc->tx_mdev_max;
+
                 hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
         } else {
                 /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
@@ -367,7 +368,7 @@ static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
                                 hc->tx_rttvar -= (hc->tx_rttvar -
                                                   hc->tx_mdev_max) >> 2;
                         hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
-                        hc->tx_mdev_max = TCP_RTO_MIN;
+                        hc->tx_mdev_max = tcp_rto_min(sk);
                 }
         }