Subject: Re: [PATCH 4/5] dccp: Initialisation and type-checking of feature sysctls

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Mon, 15 Dec 2008 12:15:44 -0200

Em Sat, Dec 13, 2008 at 02:41:24PM +0100, Gerrit Renker escreveu:
> 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 act on 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.
> 
> Further changes:
> ----------------
> Performed s@sysctl_dccp_feat@sysctl_dccp@g since the sysctls are now in feat.c.
> 
> Signed-off-by: Gerrit Renker <[email-masked]>
> Acked-by: Ian McDonald <[email-masked]>
> ---
>  include/linux/dccp.h |    8 --------
>  net/dccp/dccp.h      |    3 ---
>  net/dccp/feat.c      |   11 ++++++++---
>  net/dccp/feat.h      |    8 ++++++++
>  net/dccp/options.c   |    4 ----
>  net/dccp/sysctl.c    |   43 ++++++++++++++++++++++++++++++-------------
>  6 files changed, 46 insertions(+), 31 deletions(-)
> 
> --- a/net/dccp/feat.h
> +++ b/net/dccp/feat.h
> @@ -100,6 +100,13 @@ struct ccid_dependency {
>  	u8	val;
>  };
>  
> +/*
> + * Sysctls to seed defaults for feature negotiation
> + */
> +extern unsigned long sysctl_dccp_sequence_window;
> +extern int	     sysctl_dccp_rx_ccid;
> +extern int	     sysctl_dccp_tx_ccid;
> +
>  #ifdef CONFIG_IP_DCCP_DEBUG
>  extern const char *dccp_feat_typename(const u8 type);
>  extern const char *dccp_feat_name(const u8 feat);
> @@ -114,6 +121,7 @@ static inline void dccp_feat_debug(const u8 type, const u8 feat, const u8 val)
>  #endif /* CONFIG_IP_DCCP_DEBUG */
>  
>  extern int  dccp_feat_init(struct sock *sk);
> +extern void dccp_feat_initialise_sysctls(void);
>  extern int  dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
>  				  u8 const *list, u8 len);
>  extern int  dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val);
> --- a/net/dccp/feat.c
> +++ b/net/dccp/feat.c
> @@ -25,6 +25,11 @@
>  #include "ccid.h"
>  #include "feat.h"
>  
> +/* feature-specific sysctls - initialised to the defaults from RFC 4340, 6.4 */
> +unsigned long	sysctl_dccp_sequence_window __read_mostly = 100;
> +int		sysctl_dccp_rx_ccid	    __read_mostly = 2,
> +		sysctl_dccp_tx_ccid	    __read_mostly = 2;
> +
>  /*
>   * Feature activation handlers.
>   *
> @@ -1146,7 +1151,7 @@ int dccp_feat_init(struct sock *sk)
>  
>  	/* Non-negotiable (NN) features */
>  	rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0,
> -				    sysctl_dccp_feat_sequence_window);
> +				    sysctl_dccp_sequence_window);
>  	if (rc)
>  		return rc;
>  
> @@ -1177,8 +1182,8 @@ int dccp_feat_init(struct sock *sk)
>  	if (ccid_request_modules(tx.val, tx.len))
>  		goto free_ccid_lists;
>  
> -	if (!dccp_feat_prefer(sysctl_dccp_feat_tx_ccid, tx.val, tx.len) ||
> -	    !dccp_feat_prefer(sysctl_dccp_feat_rx_ccid, rx.val, rx.len))
> +	if (!dccp_feat_prefer(sysctl_dccp_tx_ccid, tx.val, tx.len) ||
> +	    !dccp_feat_prefer(sysctl_dccp_rx_ccid, rx.val, rx.len))
>  		goto free_ccid_lists;
>  
>  	rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);
> --- a/net/dccp/dccp.h
> +++ b/net/dccp/dccp.h
> @@ -95,9 +95,6 @@ extern void dccp_time_wait(struct sock *sk, int state, int timeo);
>  extern int  sysctl_dccp_request_retries;
>  extern int  sysctl_dccp_retries1;
>  extern int  sysctl_dccp_retries2;
> -extern int  sysctl_dccp_feat_sequence_window;
> -extern int  sysctl_dccp_feat_rx_ccid;
> -extern int  sysctl_dccp_feat_tx_ccid;
>  extern int  sysctl_dccp_tx_qlen;
>  extern int  sysctl_dccp_sync_ratelimit;
>  
> --- a/include/linux/dccp.h
> +++ b/include/linux/dccp.h
> @@ -355,14 +355,6 @@ static inline unsigned int dccp_hdr_len(const struct sk_buff *skb)
>  	return __dccp_hdr_len(dccp_hdr(skb));
>  }
>  
> -
> -/* initial values for each feature */
> -#define DCCPF_INITIAL_SEQUENCE_WINDOW		100
> -#define DCCPF_INITIAL_ACK_RATIO			2
> -#define DCCPF_INITIAL_CCID			DCCPC_CCID2
> -/* FIXME: for now we're default to 1 but it should really be 0 */
> -#define DCCPF_INITIAL_SEND_NDP_COUNT		1
> -
>  /**
>   * struct dccp_request_sock  -  represent DCCP-specific connection request
>   * @dreq_inet_rsk: structure inherited from
> --- a/net/dccp/options.c
> +++ b/net/dccp/options.c
> @@ -23,10 +23,6 @@
>  #include "dccp.h"
>  #include "feat.h"
>  
> -int sysctl_dccp_feat_sequence_window = DCCPF_INITIAL_SEQUENCE_WINDOW;
> -int sysctl_dccp_feat_rx_ccid	      = DCCPF_INITIAL_CCID;
> -int sysctl_dccp_feat_tx_ccid	      = DCCPF_INITIAL_CCID;
> -
>  u64 dccp_decode_value_var(const u8 *bf, const u8 len)
>  {
>  	u64 value = 0;
> --- 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;

I wonder if these aren't available for wider use... some files have it:

./kernel/sysctl.c
./fs/inotify_user.c
./net/sunrpc/xprtrdma/transport.c
./net/ipv4/ip_fragment.c
./net/ipv4/sysctl_net_ipv4.c
./net/sctp/sysctl.c (well, this one also does the not needed '= 0' :) */

static int zero;

Some others, such as ./net/netrom/sysctl_net_netrom.c, could also use it

And one, etc, and it seems some people are even more crazy about saving
some bytes:

/* Constants used for minimum and  maximum */
#if defined(CONFIG_HIGHMEM) || defined(CONFIG_DETECT_SOFTLOCKUP)
static int one = 1;
#endif

Unsure if the cost of exporting this to modules will do us good tho...

Perhaps some janitor may be interested in doing some measurements and
looking at u8_max (int_max, etc) too? :-)

Other than that:

Acked-by: Arnaldo Carvalho de Melo <[email-masked]>

- Arnaldo

> +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",
> --
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