sctp: Update SWS avaoidance receiver side algorithm
We currently send window update SACKs every time we free up 1 PMTU
worth of data. That a lot more SACKs then necessary. Instead, we'll
now send back the actuall window every time we send a sack, and do
window-update SACKs when a fraction of the receive buffer has been
opened. The fraction is controlled with a sysctl.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
diff --git a/include/net/sctp/constants.h b/include/net/sctp/constants.h
index 58f714a..6390884 100644
--- a/include/net/sctp/constants.h
+++ b/include/net/sctp/constants.h
@@ -308,6 +308,10 @@
#define SCTP_DEFAULT_MINWINDOW 1500 /* default minimum rwnd size */
#define SCTP_DEFAULT_MAXWINDOW 65535 /* default rwnd size */
+#define SCTP_DEFAULT_RWND_SHIFT 4 /* by default, update on 1/16 of
+ * rcvbuf, which is 1/8 of initial
+ * window
+ */
#define SCTP_DEFAULT_MAXSEGMENT 1500 /* MTU size, this is the limit
* to which we will raise the P-MTU.
*/
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index cd2e187..90876b6 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -231,6 +231,11 @@
/* Flag to indicate whether computing and verifying checksum
* is disabled. */
int checksum_disable;
+
+ /* Threshold for rwnd update SACKS. Receive buffer shifted this many
+ * bits is an indicator of when to send and window update SACK.
+ */
+ int rwnd_update_shift;
} sctp_globals;
#define sctp_rto_initial (sctp_globals.rto_initial)
@@ -267,6 +272,7 @@
#define sctp_prsctp_enable (sctp_globals.prsctp_enable)
#define sctp_auth_enable (sctp_globals.auth_enable)
#define sctp_checksum_disable (sctp_globals.checksum_disable)
+#define sctp_rwnd_upd_shift (sctp_globals.rwnd_update_shift)
/* SCTP Socket type: UDP or TCP style. */
typedef enum {
diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 8e755eb..37e9825 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1383,8 +1383,9 @@
case SCTP_STATE_SHUTDOWN_RECEIVED:
case SCTP_STATE_SHUTDOWN_SENT:
if ((asoc->rwnd > asoc->a_rwnd) &&
- ((asoc->rwnd - asoc->a_rwnd) >=
- min_t(__u32, (asoc->base.sk->sk_rcvbuf >> 1), asoc->pathmtu)))
+ ((asoc->rwnd - asoc->a_rwnd) >= max_t(__u32,
+ (asoc->base.sk->sk_rcvbuf >> sctp_rwnd_upd_shift),
+ asoc->pathmtu)))
return 1;
break;
default:
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 08ef203..a3c8988 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1258,6 +1258,9 @@
/* Set SCOPE policy to enabled */
sctp_scope_policy = SCTP_SCOPE_POLICY_ENABLE;
+ /* Set the default rwnd update threshold */
+ sctp_rwnd_upd_shift = SCTP_DEFAULT_RWND_SHIFT;
+
sctp_sysctl_register();
INIT_LIST_HEAD(&sctp_address_families);
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index eda4fe7..8ae6709 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -217,8 +217,7 @@
sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
SCTP_TO(SCTP_EVENT_TIMEOUT_SACK));
} else {
- if (asoc->a_rwnd > asoc->rwnd)
- asoc->a_rwnd = asoc->rwnd;
+ asoc->a_rwnd = asoc->rwnd;
sack = sctp_make_sack(asoc);
if (!sack)
goto nomem;
diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index ab7151d..ae03ded 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -52,6 +52,7 @@
static int sack_timer_min = 1;
static int sack_timer_max = 500;
static int addr_scope_max = 3; /* check sctp_scope_policy_t in include/net/sctp/constants.h for max entries */
+static int rwnd_scale_max = 16;
extern int sysctl_sctp_mem[3];
extern int sysctl_sctp_rmem[3];
@@ -284,6 +285,18 @@
.extra1 = &zero,
.extra2 = &addr_scope_max,
},
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "rwnd_update_shift",
+ .data = &sctp_rwnd_upd_shift,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .strategy = &sysctl_intvec,
+ .extra1 = &one,
+ .extra2 = &rwnd_scale_max,
+ },
+
{ .ctl_name = 0 }
};