This came up recently in a comment on dccp@vger. Following this up showed that
* unsigned long on 64 bit systems can be 8 bytes
Here the upper bound of 2^46-1 is neither checked nor enforced, causing
connections to silently fail.
* unsigned long on 32 bit systems is 4 bytes
This limits the maximum upper bound to 2^32-1.
The fix is to enforce the same limit of 2^32-1 on both systems, and document it.
>>>>>>>>>>>>>>>>>>>>>>>> Patch <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
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@xxxxxxxxxxxxxx>
---
Documentation/networking/dccp.txt | 1 +
net/dccp/sysctl.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
--- 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
--- 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_tab
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
.extra1 = &seqw_min, /* RFC 4340, 7.5.2 */
+ .extra2 = &seqw_max,
},
{
.procname = "rx_ccid",
--
--
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