dccp: Initialisation and type-checking of feature sysctls

This patch takes care of initialising and type-checking sysctls
related to feature negotiation. Type checking is important since some
of the sysctls now directly impact the feature-negotiation process.

The sysctls are initialised with the known default values for each
feature.  For the type-checking the value constraints from RFC 4340
are used:

 * Sequence Window uses the specified Wmin=32, the maximum is ulong (4 bytes),
   tested and confirmed that it works up to 4294967295 - for Gbps speed;
 * Ack Ratio is between 0 .. 0xffff (2-byte unsigned integer);
 * CCIDs are between 0 .. 255;
 * request_retries, retries1, retries2 also between 0..255 for good measure;
 * tx_qlen is checked to be non-negative;
 * sync_ratelimit remains as before.

Notes:
------
 1. Die s@sysctl_dccp_feat@sysctl_dccp@g since the sysctls are now in feat.c.
 2. As pointed out by Arnaldo, the pattern of type-checking repeats itself in
    other places, sometimes with exactly the same kind of definitions (e.g.
    "static int zero;"). It may be a good idea (kernel janitors?) to consolidate
    type checking. For the sake of keeping the changeset small and in order not
    to affect other subsystems, I have not strived to generalise here.

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

1 files changed, 30 insertions, 13 deletions

diff --git a/net/dccp/sysctl.c b/net/dccp/sysctl.c
index 018e210875e1..a5a1856234e7 100644
--- a/net/dccp/sysctl.c
+++ b/net/dccp/sysctl.c
@@ -18,55 +18,72 @@
 #error This file should not be compiled without CONFIG_SYSCTL defined
 #endif
 
+/* Boundary values */
+static int		zero     = 0,
+			u8_max   = 0xFF;
+static unsigned long	seqw_min = 32;
+
 static struct ctl_table dccp_default_table[] = {
 	{
 		.procname	= "seq_window",
-		.data		= &sysctl_dccp_feat_sequence_window,
-		.maxlen		= sizeof(sysctl_dccp_feat_sequence_window),
+		.data		= &sysctl_dccp_sequence_window,
+		.maxlen		= sizeof(sysctl_dccp_sequence_window),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_doulongvec_minmax,
+		.extra1		= &seqw_min,		/* RFC 4340, 7.5.2 */
 	},
 	{
 		.procname	= "rx_ccid",
-		.data		= &sysctl_dccp_feat_rx_ccid,
-		.maxlen		= sizeof(sysctl_dccp_feat_rx_ccid),
+		.data		= &sysctl_dccp_rx_ccid,
+		.maxlen		= sizeof(sysctl_dccp_rx_ccid),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &u8_max,		/* RFC 4340, 10. */
 	},
 	{
 		.procname	= "tx_ccid",
-		.data		= &sysctl_dccp_feat_tx_ccid,
-		.maxlen		= sizeof(sysctl_dccp_feat_tx_ccid),
+		.data		= &sysctl_dccp_tx_ccid,
+		.maxlen		= sizeof(sysctl_dccp_tx_ccid),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &u8_max,		/* RFC 4340, 10. */
 	},
 	{
 		.procname	= "request_retries",
 		.data		= &sysctl_dccp_request_retries,
 		.maxlen		= sizeof(sysctl_dccp_request_retries),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &u8_max,
 	},
 	{
 		.procname	= "retries1",
 		.data		= &sysctl_dccp_retries1,
 		.maxlen		= sizeof(sysctl_dccp_retries1),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &u8_max,
 	},
 	{
 		.procname	= "retries2",
 		.data		= &sysctl_dccp_retries2,
 		.maxlen		= sizeof(sysctl_dccp_retries2),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &u8_max,
 	},
 	{
 		.procname	= "tx_qlen",
 		.data		= &sysctl_dccp_tx_qlen,
 		.maxlen		= sizeof(sysctl_dccp_tx_qlen),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
 	},
 	{
 		.procname	= "sync_ratelimit",