dccp: Lockless integration of CCID congestion-control plugins
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>
diff --git a/net/dccp/ccid.c b/net/dccp/ccid.c
index bcc643f..538d3b1 100644
--- a/net/dccp/ccid.c
+++ b/net/dccp/ccid.c
@@ -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 @@
#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 @@
}
}
+#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 @@
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 @@
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 @@
}
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 @@
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 @@
}
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]);
+}