Commit 182691d0 authored by Marcelo Ricardo Leitner's avatar Marcelo Ricardo Leitner Committed by David S. Miller
Browse files

sctp: improve how SSN, TSN and ASCONF serial are compared 



Make it similar to time_before() macros:
- easier to understand
- make use of typecheck() to avoid working on unexpected variable types
  (made the issue on previous patch visible)
- for _[lg]te versions, slighly faster, as the compiler used to generate
  a sequence of cmp/je/cmp/js instructions and now it's sub/test/jle
  (for _lte):

Before, for sctp_outq_sack:
	if (primary->cacc.changeover_active) {
    1f01:	80 b9 84 02 00 00 00 	cmpb   $0x0,0x284(%rcx)
    1f08:	74 6e                	je     1f78 <sctp_outq_sack+0xe8>
		u8 clear_cycling = 0;

		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
    1f0a:	8b 81 80 02 00 00    	mov    0x280(%rcx),%eax
	return ((s) - (t)) & TSN_SIGN_BIT;
}

static inline int TSN_lte(__u32 s, __u32 t)
{
	return ((s) == (t)) || (((s) - (t)) & TSN_SIGN_BIT);
    1f10:	8b 7d bc             	mov    -0x44(%rbp),%edi
    1f13:	39 c7                	cmp    %eax,%edi
    1f15:	74 25                	je     1f3c <sctp_outq_sack+0xac>
    1f17:	39 f8                	cmp    %edi,%eax
    1f19:	78 21                	js     1f3c <sctp_outq_sack+0xac>
			primary->cacc.changeover_active = 0;

After:
	if (primary->cacc.changeover_active) {
    1ee7:	80 b9 84 02 00 00 00 	cmpb   $0x0,0x284(%rcx)
    1eee:	74 73                	je     1f63 <sctp_outq_sack+0xf3>
		u8 clear_cycling = 0;

		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
    1ef0:	8b 81 80 02 00 00    	mov    0x280(%rcx),%eax
    1ef6:	2b 45 b4             	sub    -0x4c(%rbp),%eax
    1ef9:	85 c0                	test   %eax,%eax
    1efb:	7e 26                	jle    1f23 <sctp_outq_sack+0xb3>
			primary->cacc.changeover_active = 0;

*_lt() generated pretty much the same code.
Tested with gcc (GCC) 6.1.1 20160621.

This patch also removes SSN_lte as it is not used and cleanups some
comments.

Signed-off-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a3007446

include/net/sctp/sm.h

+18 −76
Original line number Diff line number Diff line
@@ -307,85 +307,27 @@ static inline __u16 sctp_data_size(struct sctp_chunk *chunk) 
}



/* Compare two TSNs */

#define TSN_lt(a,b)	\

	(typecheck(__u32, a) && \

	 typecheck(__u32, b) && \

	 ((__s32)((a) - (b)) < 0))



/* RFC 1982 - Serial Number Arithmetic

 *

 * 2. Comparison

 *  Then, s1 is said to be equal to s2 if and only if i1 is equal to i2,

 *  in all other cases, s1 is not equal to s2.

 *

 * s1 is said to be less than s2 if, and only if, s1 is not equal to s2,

 * and

 *

 *      (i1 < i2 and i2 - i1 < 2^(SERIAL_BITS - 1)) or

 *      (i1 > i2 and i1 - i2 > 2^(SERIAL_BITS - 1))

 *

 * s1 is said to be greater than s2 if, and only if, s1 is not equal to

 * s2, and

 *

 *      (i1 < i2 and i2 - i1 > 2^(SERIAL_BITS - 1)) or

 *      (i1 > i2 and i1 - i2 < 2^(SERIAL_BITS - 1))

 */



/*

 * RFC 2960

 *  1.6 Serial Number Arithmetic

 *

 * Comparisons and arithmetic on TSNs in this document SHOULD use Serial

 * Number Arithmetic as defined in [RFC1982] where SERIAL_BITS = 32.

 */



enum {

	TSN_SIGN_BIT = (1<<31)

};



static inline int TSN_lt(__u32 s, __u32 t)

{

	return ((s) - (t)) & TSN_SIGN_BIT;

}



static inline int TSN_lte(__u32 s, __u32 t)

{

	return ((s) == (t)) || (((s) - (t)) & TSN_SIGN_BIT);

}

#define TSN_lte(a,b)	\

	(typecheck(__u32, a) && \

	 typecheck(__u32, b) && \

	 ((__s32)((a) - (b)) <= 0))



/* Compare two SSNs */



/*

 * RFC 2960

 *  1.6 Serial Number Arithmetic

 *

 * Comparisons and arithmetic on Stream Sequence Numbers in this document

 * SHOULD use Serial Number Arithmetic as defined in [RFC1982] where

 * SERIAL_BITS = 16.

 */

enum {

	SSN_SIGN_BIT = (1<<15)

};



static inline int SSN_lt(__u16 s, __u16 t)

{

	return ((s) - (t)) & SSN_SIGN_BIT;

}



static inline int SSN_lte(__u16 s, __u16 t)

{

	return ((s) == (t)) || (((s) - (t)) & SSN_SIGN_BIT);

}



/*

 * ADDIP 3.1.1

 * The valid range of Serial Number is from 0 to 4294967295 (2**32 - 1). Serial

 * Numbers wrap back to 0 after reaching 4294967295.

 */

enum {

	ADDIP_SERIAL_SIGN_BIT = (1<<31)

};



static inline int ADDIP_SERIAL_gte(__u32 s, __u32 t)

{

	return ((s) == (t)) || (((t) - (s)) & ADDIP_SERIAL_SIGN_BIT);

}

#define SSN_lt(a,b)		\

	(typecheck(__u16, a) && \

	 typecheck(__u16, b) && \

	 ((__s16)((a) - (b)) < 0))



/* ADDIP 3.1.1 */

#define ADDIP_SERIAL_gte(a,b)	\

	(typecheck(__u32, a) && \

	 typecheck(__u32, b) && \

	 ((__s32)((b) - (a)) <= 0))



/* Check VTAG of the packet matches the sender's own tag. */

static inline int

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