* [PATCH next 0/2] improvements to SSN and TSN handling
@ 2016-09-20 21:19 Marcelo Ricardo Leitner
2016-09-20 21:19 ` [PATCH next 1/2] sctp: fix the handling of SACK Gap Ack blocks Marcelo Ricardo Leitner
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Marcelo Ricardo Leitner @ 2016-09-20 21:19 UTC (permalink / raw)
To: netdev; +Cc: linux-sctp, Neil Horman, Vlad Yasevich, David Laight
First patch fixes a potential issue made visible by the second one
noticed by David Laight and is a preparation for the next one.
The second patch changes how SSN, TSN and ASCONF serials are compared so
they can use typecheck() and are more like time_before() macro.
Marcelo Ricardo Leitner (2):
sctp: fix the handling of SACK Gap Ack blocks
sctp: improve how SSN, TSN and ASCONF serial are compared
include/net/sctp/sm.h | 94 ++++++++++-----------------------------------------
net/sctp/outqueue.c | 11 +++---
2 files changed, 24 insertions(+), 81 deletions(-)
--
2.7.4
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH next 1/2] sctp: fix the handling of SACK Gap Ack blocks
2016-09-20 21:19 [PATCH next 0/2] improvements to SSN and TSN handling Marcelo Ricardo Leitner
@ 2016-09-20 21:19 ` Marcelo Ricardo Leitner
2016-09-21 10:21 ` David Laight
2016-09-20 21:19 ` [PATCH next 2/2] sctp: improve how SSN, TSN and ASCONF serial are compared Marcelo Ricardo Leitner
2016-09-23 10:55 ` [PATCH next 0/2] improvements to SSN and TSN handling David Miller
2 siblings, 1 reply; 6+ messages in thread
From: Marcelo Ricardo Leitner @ 2016-09-20 21:19 UTC (permalink / raw)
To: netdev; +Cc: linux-sctp, Neil Horman, Vlad Yasevich, David Laight
sctp_acked() is using 32bit arithmetics on 16bits vars, via TSN_lte()
macros, which is weird and confusing.
Once the offset to ctsn is calculated, all wrapping is already handled
and thus to verify the Gap Ack blocks we can just use pure
less/big-or-equal than checks.
Also, rename gap variable to tsn_offset, so it's more meaningful, as
it doesn't point to any gap at all.
Even so, I don't think this discrepancy resulted in any practical bug.
This patch is a preparation for the next one, which will introduce
typecheck() for TSN_lte() macros and would cause a compile error here.
Suggested-by: David Laight <David.Laight@ACULAB.COM>
Reported-by: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
net/sctp/outqueue.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 8c3f446d965c030376d0cfafd2c64b9a946d2cc1..3ec6da8bbb5360187007935838717885c97f9e91 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1719,7 +1719,7 @@ static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
{
int i;
sctp_sack_variable_t *frags;
- __u16 gap;
+ __u16 tsn_offset, blocks;
__u32 ctsn = ntohl(sack->cum_tsn_ack);
if (TSN_lte(tsn, ctsn))
@@ -1738,10 +1738,11 @@ static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
*/
frags = sack->variable;
- gap = tsn - ctsn;
- for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
- if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
- TSN_lte(gap, ntohs(frags[i].gab.end)))
+ blocks = ntohs(sack->num_gap_ack_blocks);
+ tsn_offset = tsn - ctsn;
+ for (i = 0; i < blocks; ++i) {
+ if (tsn_offset >= ntohs(frags[i].gab.start) &&
+ tsn_offset <= ntohs(frags[i].gab.end))
goto pass;
}
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH next 2/2] sctp: improve how SSN, TSN and ASCONF serial are compared
2016-09-20 21:19 [PATCH next 0/2] improvements to SSN and TSN handling Marcelo Ricardo Leitner
2016-09-20 21:19 ` [PATCH next 1/2] sctp: fix the handling of SACK Gap Ack blocks Marcelo Ricardo Leitner
@ 2016-09-20 21:19 ` Marcelo Ricardo Leitner
2016-09-23 10:55 ` [PATCH next 0/2] improvements to SSN and TSN handling David Miller
2 siblings, 0 replies; 6+ messages in thread
From: Marcelo Ricardo Leitner @ 2016-09-20 21:19 UTC (permalink / raw)
To: netdev; +Cc: linux-sctp, Neil Horman, Vlad Yasevich, David Laight
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: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
include/net/sctp/sm.h | 94 ++++++++++-----------------------------------------
1 file changed, 18 insertions(+), 76 deletions(-)
diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index bafe2a0ab9085f24e17038516c55c00cfddd02f4..ca6c971dd74aede829d4512ddf71006520c78f47 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -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
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* RE: [PATCH next 1/2] sctp: fix the handling of SACK Gap Ack blocks
2016-09-20 21:19 ` [PATCH next 1/2] sctp: fix the handling of SACK Gap Ack blocks Marcelo Ricardo Leitner
@ 2016-09-21 10:21 ` David Laight
2016-09-21 11:01 ` 'Marcelo Ricardo Leitner'
0 siblings, 1 reply; 6+ messages in thread
From: David Laight @ 2016-09-21 10:21 UTC (permalink / raw)
To: 'Marcelo Ricardo Leitner', netdev
Cc: linux-sctp, Neil Horman, Vlad Yasevich
From: Marcelo Ricardo Leitner
> Sent: 20 September 2016 22:19
> sctp_acked() is using 32bit arithmetics on 16bits vars, via TSN_lte()
> macros, which is weird and confusing.
>
> Once the offset to ctsn is calculated, all wrapping is already handled
> and thus to verify the Gap Ack blocks we can just use pure
> less/big-or-equal than checks.
>
> Also, rename gap variable to tsn_offset, so it's more meaningful, as
> it doesn't point to any gap at all.
>
> Even so, I don't think this discrepancy resulted in any practical bug.
I think it might if gab.start/end are greater than 32767
...
> - gap = tsn - ctsn;
> - for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
> - if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
> - TSN_lte(gap, ntohs(frags[i].gab.end)))
> + blocks = ntohs(sack->num_gap_ack_blocks);
> + tsn_offset = tsn - ctsn;
> + for (i = 0; i < blocks; ++i) {
> + if (tsn_offset >= ntohs(frags[i].gab.start) &&
> + tsn_offset <= ntohs(frags[i].gab.end))
...
David
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH next 1/2] sctp: fix the handling of SACK Gap Ack blocks
2016-09-21 10:21 ` David Laight
@ 2016-09-21 11:01 ` 'Marcelo Ricardo Leitner'
0 siblings, 0 replies; 6+ messages in thread
From: 'Marcelo Ricardo Leitner' @ 2016-09-21 11:01 UTC (permalink / raw)
To: David Laight; +Cc: netdev, linux-sctp, Neil Horman, Vlad Yasevich
On Wed, Sep 21, 2016 at 10:21:43AM +0000, David Laight wrote:
> From: Marcelo Ricardo Leitner
> > Sent: 20 September 2016 22:19
> > sctp_acked() is using 32bit arithmetics on 16bits vars, via TSN_lte()
> > macros, which is weird and confusing.
> >
> > Once the offset to ctsn is calculated, all wrapping is already handled
> > and thus to verify the Gap Ack blocks we can just use pure
> > less/big-or-equal than checks.
> >
> > Also, rename gap variable to tsn_offset, so it's more meaningful, as
> > it doesn't point to any gap at all.
> >
> > Even so, I don't think this discrepancy resulted in any practical bug.
>
> I think it might if gab.start/end are greater than 32767
Why? Mind sharing a case that it goes wrong?
Marcelo
>
> ...
> > - gap = tsn - ctsn;
> > - for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
> > - if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
> > - TSN_lte(gap, ntohs(frags[i].gab.end)))
> > + blocks = ntohs(sack->num_gap_ack_blocks);
> > + tsn_offset = tsn - ctsn;
> > + for (i = 0; i < blocks; ++i) {
> > + if (tsn_offset >= ntohs(frags[i].gab.start) &&
> > + tsn_offset <= ntohs(frags[i].gab.end))
> ...
>
> David
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH next 0/2] improvements to SSN and TSN handling
2016-09-20 21:19 [PATCH next 0/2] improvements to SSN and TSN handling Marcelo Ricardo Leitner
2016-09-20 21:19 ` [PATCH next 1/2] sctp: fix the handling of SACK Gap Ack blocks Marcelo Ricardo Leitner
2016-09-20 21:19 ` [PATCH next 2/2] sctp: improve how SSN, TSN and ASCONF serial are compared Marcelo Ricardo Leitner
@ 2016-09-23 10:55 ` David Miller
2 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2016-09-23 10:55 UTC (permalink / raw)
To: marcelo.leitner; +Cc: netdev, linux-sctp, nhorman, vyasevich, David.Laight
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: Tue, 20 Sep 2016 18:19:12 -0300
> First patch fixes a potential issue made visible by the second one
> noticed by David Laight and is a preparation for the next one.
>
> The second patch changes how SSN, TSN and ASCONF serials are compared so
> they can use typecheck() and are more like time_before() macro.
Series applied, thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2016-09-20 21:19 [PATCH next 0/2] improvements to SSN and TSN handling Marcelo Ricardo Leitner
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2016-09-21 10:21 ` David Laight
2016-09-21 11:01 ` 'Marcelo Ricardo Leitner'
2016-09-20 21:19 ` [PATCH next 2/2] sctp: improve how SSN, TSN and ASCONF serial are compared Marcelo Ricardo Leitner
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