dccp: make upper bound for seq_window consistent on 32/64 bit

The 'seq_window' sysctl sets the initial value for the DCCP Sequence Window,
which may range from 32..2^46-1 (RFC 4340, 7.5.2). The patch sets the upper
bound consistently to 2^32-1 on both 32 and 64 bit systems, which should be
sufficient - with a RTT of 1sec and 1-byte packets, a seq_window of 2^32-1
corresponds to a link speed of 34 Gbps.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

2 files changed, 4 insertions, 1 deletions

diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index b395ca6a49f2..811872b45bee 100644
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -167,6 +167,7 @@ rx_ccid = 2
 seq_window = 100
         The initial sequence window (sec. 7.5.2) of the sender. This influences
         the local ackno validity and the remote seqno validity windows (7.5.1).
+        Values in the range Wmin = 32 (RFC 4340, 7.5.2) up to 2^32-1 can be set.
 
 tx_qlen = 5
         The size of the transmit buffer in packets. A value of 0 corresponds
diff --git a/net/dccp/sysctl.c b/net/dccp/sysctl.c
index 563943822e58..42348824ee31 100644
--- a/net/dccp/sysctl.c
+++ b/net/dccp/sysctl.c
@@ -21,7 +21,8 @@
 /* Boundary values */
 static int              zero     = 0,
                         u8_max   = 0xFF;
-static unsigned long    seqw_min = 32;
+static unsigned long    seqw_min = DCCPF_SEQ_WMIN,
+                        seqw_max = 0xFFFFFFFF;          /* maximum on 32 bit */
 
 static struct ctl_table dccp_default_table[] = {
         {
@@ -31,6 +32,7 @@ static struct ctl_table dccp_default_table[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_doulongvec_minmax,
                 .extra1         = &seqw_min,            /* RFC 4340, 7.5.2 */
+                .extra2         = &seqw_max,
         },
         {
                 .procname       = "rx_ccid",