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dccp: Lockless integration of CCID congestion-control plugins

Browse source 
Based on Arnaldo's earlier patch, this patch integrates the standardised
CCID congestion control plugins (CCID-2 and CCID-3) of DCCP with dccp.ko:

 * enables a faster connection path by eliminating the need to always go 
   through the CCID registration lock;

 * updates the implementation to use only a single array whose size equals
   the number of configured CCIDs instead of the maximum (256);

 * since the CCIDs are now fixed array elements, synchronization is no
   longer needed, simplifying use and implementation.

CCID-2 is suggested as minimum for a basic DCCP implementation (RFC 4340, 10);
CCID-3 is a standards-track CCID supported by RFC 4342 and RFC 5348.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2009-01-04 21:42:53 -08:00 committed by David S. Miller
parent 6ea2fde13a
commit ddebc973c5
11 changed files with 148 additions and 168 deletions
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4
net/dccp/Kconfig
View file

@ -1,7 +1,6 @@
menuconfig IP_DCCP
tristate "The DCCP Protocol (EXPERIMENTAL)"
depends on INET && EXPERIMENTAL
select IP_DCCP_CCID2
---help---
Datagram Congestion Control Protocol (RFC 4340)
@ -25,9 +24,6 @@ config INET_DCCP_DIAG
def_tristate y if (IP_DCCP = y && INET_DIAG = y)
def_tristate m
config IP_DCCP_ACKVEC
bool
source "net/dccp/ccids/Kconfig"
menu "DCCP Kernel Hacking"

9
net/dccp/Makefile
View file

@ -2,14 +2,19 @@ obj-$(CONFIG_IP_DCCP) += dccp.o dccp_ipv4.o
dccp-y := ccid.o feat.o input.o minisocks.o options.o output.o proto.o timer.o
#
# CCID algorithms to be used by dccp.ko
#
# CCID-2 is default (RFC 4340, p. 77) and has Ack Vectors as dependency
dccp-y += ccids/ccid2.o ackvec.o
dccp-$(CONFIG_IP_DCCP_CCID3) += ccids/ccid3.o
dccp_ipv4-y := ipv4.o
# build dccp_ipv6 as module whenever either IPv6 or DCCP is a module
obj-$(subst y,$(CONFIG_IP_DCCP),$(CONFIG_IPV6)) += dccp_ipv6.o
dccp_ipv6-y := ipv6.o
dccp-$(CONFIG_IP_DCCP_ACKVEC) += ackvec.o
obj-$(CONFIG_INET_DCCP_DIAG) += dccp_diag.o
obj-$(CONFIG_NET_DCCPPROBE) += dccp_probe.o

4
net/dccp/ackvec.h
View file

@ -84,7 +84,7 @@ struct dccp_ackvec_record {
struct sock;
struct sk_buff;
#ifdef CONFIG_IP_DCCP_ACKVEC
#ifndef ___OLD_INTERFACE_TO_BE_REMOVED___
extern int dccp_ackvec_init(void);
extern void dccp_ackvec_exit(void);
@ -106,7 +106,7 @@ static inline int dccp_ackvec_pending(const struct dccp_ackvec *av)
{
return av->av_vec_len;
}
#else /* CONFIG_IP_DCCP_ACKVEC */
#else /* ___OLD_INTERFACE_TO_BE_REMOVED___ */
static inline int dccp_ackvec_init(void)
{
return 0;

156
net/dccp/ccid.c
View file

@ -13,6 +13,70 @@
#include "ccid.h"
static struct ccid_operations *ccids[] = {
&ccid2_ops,
#ifdef CONFIG_IP_DCCP_CCID3
&ccid3_ops,
#endif
};
static struct ccid_operations *ccid_by_number(const u8 id)
{
int i;
for (i = 0; i < ARRAY_SIZE(ccids); i++)
if (ccids[i]->ccid_id == id)
return ccids[i];
return NULL;
}
/* check that up to @array_len members in @ccid_array are supported */
bool ccid_support_check(u8 const *ccid_array, u8 array_len)
{
while (array_len > 0)
if (ccid_by_number(ccid_array[--array_len]) == NULL)
return false;
return true;
}
/**
* ccid_get_builtin_ccids - Populate a list of built-in CCIDs
* @ccid_array: pointer to copy into
* @array_len: value to return length into
* This function allocates memory - caller must see that it is freed after use.
*/
int ccid_get_builtin_ccids(u8 **ccid_array, u8 *array_len)
{
*ccid_array = kmalloc(ARRAY_SIZE(ccids), gfp_any());
if (*ccid_array == NULL)
return -ENOBUFS;
for (*array_len = 0; *array_len < ARRAY_SIZE(ccids); *array_len += 1)
(*ccid_array)[*array_len] = ccids[*array_len]->ccid_id;
return 0;
}
int ccid_getsockopt_builtin_ccids(struct sock *sk, int len,
char __user *optval, int __user *optlen)
{
u8 *ccid_array, array_len;
int err = 0;
if (len < ARRAY_SIZE(ccids))
return -EINVAL;
if (ccid_get_builtin_ccids(&ccid_array, &array_len))
return -ENOBUFS;
if (put_user(array_len, optlen) ||
copy_to_user(optval, ccid_array, array_len))
err = -EFAULT;
kfree(ccid_array);
return err;
}
#ifdef ___OLD_INTERFACE_TO_BE_REMOVED___
static u8 builtin_ccids[] = {
DCCPC_CCID2, /* CCID2 is supported by default */
#if defined(CONFIG_IP_DCCP_CCID3) || defined(CONFIG_IP_DCCP_CCID3_MODULE)
@ -62,6 +126,7 @@ static inline void ccids_read_unlock(void)
#define ccids_read_lock() do { } while(0)
#define ccids_read_unlock() do { } while(0)
#endif
#endif /* ___OLD_INTERFACE_TO_BE_REMOVED___ */
static struct kmem_cache *ccid_kmem_cache_create(int obj_size, const char *fmt,...)
{
@ -93,6 +158,7 @@ static void ccid_kmem_cache_destroy(struct kmem_cache *slab)
}
}
#ifdef ___OLD_INTERFACE_TO_BE_REMOVED___
/* check that up to @array_len members in @ccid_array are supported */
bool ccid_support_check(u8 const *ccid_array, u8 array_len)
{
@ -133,8 +199,9 @@ int ccid_getsockopt_builtin_ccids(struct sock *sk, int len,
return -EFAULT;
return 0;
}
#endif /* ___OLD_INTERFACE_TO_BE_REMOVED___ */
int ccid_register(struct ccid_operations *ccid_ops)
static int ccid_activate(struct ccid_operations *ccid_ops)
{
int err = -ENOBUFS;
@ -152,79 +219,40 @@ int ccid_register(struct ccid_operations *ccid_ops)
if (ccid_ops->ccid_hc_tx_slab == NULL)
goto out_free_rx_slab;
ccids_write_lock();
err = -EEXIST;
if (ccids[ccid_ops->ccid_id] == NULL) {
ccids[ccid_ops->ccid_id] = ccid_ops;
err = 0;
}
ccids_write_unlock();
if (err != 0)
goto out_free_tx_slab;
pr_info("CCID: Registered CCID %d (%s)\n",
pr_info("CCID: Activated CCID %d (%s)\n",
ccid_ops->ccid_id, ccid_ops->ccid_name);
err = 0;
out:
return err;
out_free_tx_slab:
ccid_kmem_cache_destroy(ccid_ops->ccid_hc_tx_slab);
ccid_ops->ccid_hc_tx_slab = NULL;
goto out;
out_free_rx_slab:
ccid_kmem_cache_destroy(ccid_ops->ccid_hc_rx_slab);
ccid_ops->ccid_hc_rx_slab = NULL;
goto out;
}
EXPORT_SYMBOL_GPL(ccid_register);
int ccid_unregister(struct ccid_operations *ccid_ops)
static void ccid_deactivate(struct ccid_operations *ccid_ops)
{
ccids_write_lock();
ccids[ccid_ops->ccid_id] = NULL;
ccids_write_unlock();
ccid_kmem_cache_destroy(ccid_ops->ccid_hc_tx_slab);
ccid_ops->ccid_hc_tx_slab = NULL;
ccid_kmem_cache_destroy(ccid_ops->ccid_hc_rx_slab);
ccid_ops->ccid_hc_rx_slab = NULL;
pr_info("CCID: Unregistered CCID %d (%s)\n",
pr_info("CCID: Deactivated CCID %d (%s)\n",
ccid_ops->ccid_id, ccid_ops->ccid_name);
return 0;
}
EXPORT_SYMBOL_GPL(ccid_unregister);
struct ccid *ccid_new(unsigned char id, struct sock *sk, int rx, gfp_t gfp)
{
struct ccid_operations *ccid_ops;
struct ccid_operations *ccid_ops = ccid_by_number(id);
struct ccid *ccid = NULL;
ccids_read_lock();
#ifdef CONFIG_MODULES
if (ccids[id] == NULL) {
/* We only try to load if in process context */
ccids_read_unlock();
if (gfp & GFP_ATOMIC)
goto out;
request_module("net-dccp-ccid-%d", id);
ccids_read_lock();
}
#endif
ccid_ops = ccids[id];
if (ccid_ops == NULL)
goto out_unlock;
if (!try_module_get(ccid_ops->ccid_owner))
goto out_unlock;
ccids_read_unlock();
goto out;
ccid = kmem_cache_alloc(rx ? ccid_ops->ccid_hc_rx_slab :
ccid_ops->ccid_hc_tx_slab, gfp);
if (ccid == NULL)
goto out_module_put;
goto out;
ccid->ccid_ops = ccid_ops;
if (rx) {
memset(ccid + 1, 0, ccid_ops->ccid_hc_rx_obj_size);
@ -239,15 +267,10 @@ struct ccid *ccid_new(unsigned char id, struct sock *sk, int rx, gfp_t gfp)
}
out:
return ccid;
out_unlock:
ccids_read_unlock();
goto out;
out_free_ccid:
kmem_cache_free(rx ? ccid_ops->ccid_hc_rx_slab :
ccid_ops->ccid_hc_tx_slab, ccid);
ccid = NULL;
out_module_put:
module_put(ccid_ops->ccid_owner);
goto out;
}
@ -270,10 +293,6 @@ static void ccid_delete(struct ccid *ccid, struct sock *sk, int rx)
ccid_ops->ccid_hc_tx_exit(sk);
kmem_cache_free(ccid_ops->ccid_hc_tx_slab, ccid);
}
ccids_read_lock();
if (ccids[ccid_ops->ccid_id] != NULL)
module_put(ccid_ops->ccid_owner);
ccids_read_unlock();
}
void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk)
@ -289,3 +308,28 @@ void ccid_hc_tx_delete(struct ccid *ccid, struct sock *sk)
}
EXPORT_SYMBOL_GPL(ccid_hc_tx_delete);
int __init ccid_initialize_builtins(void)
{
int i, err;
for (i = 0; i < ARRAY_SIZE(ccids); i++) {
err = ccid_activate(ccids[i]);
if (err)
goto unwind_registrations;
}
return 0;
unwind_registrations:
while(--i >= 0)
ccid_deactivate(ccids[i]);
return err;
}
void ccid_cleanup_builtins(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(ccids); i++)
ccid_deactivate(ccids[i]);
}

11
net/dccp/ccid.h
View file

@ -29,7 +29,6 @@ struct tcp_info;
* @ccid_id: numerical CCID ID (up to %CCID_MAX, cf. table 5 in RFC 4340, 10.)
* @ccid_ccmps: the CCMPS including network/transport headers (0 when disabled)
* @ccid_name: alphabetical identifier string for @ccid_id
* @ccid_owner: module which implements/owns this CCID
* @ccid_hc_{r,t}x_slab: memory pool for the receiver/sender half-connection
* @ccid_hc_{r,t}x_obj_size: size of the receiver/sender half-connection socket
*
@ -48,7 +47,6 @@ struct ccid_operations {
unsigned char ccid_id;
__u32 ccid_ccmps;
const char *ccid_name;
struct module *ccid_owner;
struct kmem_cache *ccid_hc_rx_slab,
*ccid_hc_tx_slab;
__u32 ccid_hc_rx_obj_size,
@ -90,8 +88,13 @@ struct ccid_operations {
int __user *optlen);
};
extern int ccid_register(struct ccid_operations *ccid_ops);
extern int ccid_unregister(struct ccid_operations *ccid_ops);
extern struct ccid_operations ccid2_ops;
#ifdef CONFIG_IP_DCCP_CCID3
extern struct ccid_operations ccid3_ops;
#endif
extern int ccid_initialize_builtins(void);
extern void ccid_cleanup_builtins(void);
struct ccid {
struct ccid_operations *ccid_ops;

70
net/dccp/ccids/Kconfig
View file

@ -1,80 +1,52 @@
menu "DCCP CCIDs Configuration (EXPERIMENTAL)"
depends on EXPERIMENTAL
config IP_DCCP_CCID2
tristate "CCID2 (TCP-Like) (EXPERIMENTAL)"
def_tristate IP_DCCP
select IP_DCCP_ACKVEC
---help---
CCID 2, TCP-like Congestion Control, denotes Additive Increase,
Multiplicative Decrease (AIMD) congestion control with behavior
modelled directly on TCP, including congestion window, slow start,
timeouts, and so forth [RFC 2581]. CCID 2 achieves maximum
bandwidth over the long term, consistent with the use of end-to-end
congestion control, but halves its congestion window in response to
each congestion event. This leads to the abrupt rate changes
typical of TCP. Applications should use CCID 2 if they prefer
maximum bandwidth utilization to steadiness of rate. This is often
the case for applications that are not playing their data directly
to the user. For example, a hypothetical application that
transferred files over DCCP, using application-level retransmissions
for lost packets, would prefer CCID 2 to CCID 3. On-line games may
also prefer CCID 2. See RFC 4341 for further details.
CCID2 is the default CCID used by DCCP.
config IP_DCCP_CCID2_DEBUG
bool "CCID2 debugging messages"
depends on IP_DCCP_CCID2
---help---
Enable CCID2-specific debugging messages.
bool "CCID-2 debugging messages"
---help---
Enable CCID-2 specific debugging messages.
When compiling CCID2 as a module, this debugging output can
additionally be toggled by setting the ccid2_debug module
parameter to 0 or 1.
The debugging output can additionally be toggled by setting the
ccid2_debug parameter to 0 or 1.
If in doubt, say N.
If in doubt, say N.
config IP_DCCP_CCID3
tristate "CCID3 (TCP-Friendly) (EXPERIMENTAL)"
def_tristate IP_DCCP
bool "CCID-3 (TCP-Friendly) (EXPERIMENTAL)"
def_bool y if (IP_DCCP = y || IP_DCCP = m)
select IP_DCCP_TFRC_LIB
---help---
CCID 3 denotes TCP-Friendly Rate Control (TFRC), an equation-based
CCID-3 denotes TCP-Friendly Rate Control (TFRC), an equation-based
rate-controlled congestion control mechanism. TFRC is designed to
be reasonably fair when competing for bandwidth with TCP-like flows,
where a flow is "reasonably fair" if its sending rate is generally
within a factor of two of the sending rate of a TCP flow under the
same conditions. However, TFRC has a much lower variation of
throughput over time compared with TCP, which makes CCID 3 more
suitable than CCID 2 for applications such streaming media where a
throughput over time compared with TCP, which makes CCID-3 more
suitable than CCID-2 for applications such streaming media where a
relatively smooth sending rate is of importance.
CCID 3 is further described in RFC 4342,
CCID-3 is further described in RFC 4342,
http://www.ietf.org/rfc/rfc4342.txt
The TFRC congestion control algorithms were initially described in
RFC 3448.
RFC 5448.
This text was extracted from RFC 4340 (sec. 10.2),
http://www.ietf.org/rfc/rfc4340.txt
To compile this CCID as a module, choose M here: the module will be
called dccp_ccid3.
If in doubt, say M.
If in doubt, say N.
config IP_DCCP_CCID3_DEBUG
bool "CCID3 debugging messages"
depends on IP_DCCP_CCID3
---help---
Enable CCID3-specific debugging messages.
bool "CCID-3 debugging messages"
depends on IP_DCCP_CCID3
---help---
Enable CCID-3 specific debugging messages.
When compiling CCID3 as a module, this debugging output can
additionally be toggled by setting the ccid3_debug module
parameter to 0 or 1.
The debugging output can additionally be toggled by setting the
ccid3_debug parameter to 0 or 1.
If in doubt, say N.
If in doubt, say N.
config IP_DCCP_CCID3_RTO
int "Use higher bound for nofeedback timer"

8
net/dccp/ccids/Makefile
View file

@ -1,9 +1 @@
obj-$(CONFIG_IP_DCCP_CCID3) += dccp_ccid3.o
dccp_ccid3-y := ccid3.o
obj-$(CONFIG_IP_DCCP_CCID2) += dccp_ccid2.o
dccp_ccid2-y := ccid2.o
obj-y += lib/

22
net/dccp/ccids/ccid2.c
View file

@ -768,10 +768,9 @@ static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
}
}
static struct ccid_operations ccid2 = {
struct ccid_operations ccid2_ops = {
.ccid_id = DCCPC_CCID2,
.ccid_name = "TCP-like",
.ccid_owner = THIS_MODULE,
.ccid_hc_tx_obj_size = sizeof(struct ccid2_hc_tx_sock),
.ccid_hc_tx_init = ccid2_hc_tx_init,
.ccid_hc_tx_exit = ccid2_hc_tx_exit,
@ -784,22 +783,5 @@ static struct ccid_operations ccid2 = {
#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
module_param(ccid2_debug, bool, 0644);
MODULE_PARM_DESC(ccid2_debug, "Enable debug messages");
MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
#endif
static __init int ccid2_module_init(void)
{
return ccid_register(&ccid2);
}
module_init(ccid2_module_init);
static __exit void ccid2_module_exit(void)
{
ccid_unregister(&ccid2);
}
module_exit(ccid2_module_exit);
MODULE_AUTHOR("Andrea Bittau <a.bittau@cs.ucl.ac.uk>");
MODULE_DESCRIPTION("DCCP TCP-Like (CCID2) CCID");
MODULE_LICENSE("GPL");
MODULE_ALIAS("net-dccp-ccid-2");

23
net/dccp/ccids/ccid3.c
View file

@ -940,10 +940,9 @@ static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
return 0;
}
static struct ccid_operations ccid3 = {
struct ccid_operations ccid3_ops = {
.ccid_id = DCCPC_CCID3,
.ccid_name = "TCP-Friendly Rate Control",
.ccid_owner = THIS_MODULE,
.ccid_hc_tx_obj_size = sizeof(struct ccid3_hc_tx_sock),
.ccid_hc_tx_init = ccid3_hc_tx_init,
.ccid_hc_tx_exit = ccid3_hc_tx_exit,
@ -964,23 +963,5 @@ static struct ccid_operations ccid3 = {
#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
module_param(ccid3_debug, bool, 0644);
MODULE_PARM_DESC(ccid3_debug, "Enable debug messages");
MODULE_PARM_DESC(ccid3_debug, "Enable CCID-3 debug messages");
#endif
static __init int ccid3_module_init(void)
{
return ccid_register(&ccid3);
}
module_init(ccid3_module_init);
static __exit void ccid3_module_exit(void)
{
ccid_unregister(&ccid3);
}
module_exit(ccid3_module_exit);
MODULE_AUTHOR("Ian McDonald <ian.mcdonald@jandi.co.nz>, "
"Arnaldo Carvalho de Melo <acme@ghostprotocols.net>");
MODULE_DESCRIPTION("DCCP TFRC CCID3 CCID");
MODULE_LICENSE("GPL");
MODULE_ALIAS("net-dccp-ccid-3");

2
net/dccp/dccp.h
View file

@ -432,10 +432,8 @@ static inline int dccp_ack_pending(const struct sock *sk)
{
const struct dccp_sock *dp = dccp_sk(sk);
return dp->dccps_timestamp_echo != 0 ||
#ifdef CONFIG_IP_DCCP_ACKVEC
(dp->dccps_hc_rx_ackvec != NULL &&
dccp_ackvec_pending(dp->dccps_hc_rx_ackvec)) ||
#endif
inet_csk_ack_scheduled(sk);
}

7
net/dccp/proto.c
View file

@ -1118,9 +1118,15 @@ static int __init dccp_init(void)
if (rc)
goto out_ackvec_exit;
rc = ccid_initialize_builtins();
if (rc)
goto out_sysctl_exit;
dccp_timestamping_init();
out:
return rc;
out_sysctl_exit:
dccp_sysctl_exit();
out_ackvec_exit:
dccp_ackvec_exit();
out_free_dccp_mib:
@ -1143,6 +1149,7 @@ out_free_percpu:
static void __exit dccp_fini(void)
{
ccid_cleanup_builtins();
dccp_mib_exit();
free_pages((unsigned long)dccp_hashinfo.bhash,
get_order(dccp_hashinfo.bhash_size *