[DCCP]: Initial implementation

Development to this point was done on a subversion repository at:

http://oops.ghostprotocols.net:81/cgi-bin/viewcvs.cgi/dccp-2.6/

This repository will be kept at this site for the foreseable future,
so that interested parties can see the history of this code,
attributions, etc.

If I ever decide to take this offline I'll provide the full history at
some other suitable place.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 139 insertions, 0 deletions

diff --git a/net/dccp/ccid.c b/net/dccp/ccid.c
new file mode 100644
index 000000000000..9d8fc0e289ea
--- /dev/null
+++ b/net/dccp/ccid.c
@@ -0,0 +1,139 @@
+/*
+ *  net/dccp/ccid.c
+ *
+ *  An implementation of the DCCP protocol
+ *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ *
+ *  CCID infrastructure
+ *
+ *      This program is free software; you can redistribute it and/or modify it
+ *      under the terms of the GNU General Public License version 2 as
+ *      published by the Free Software Foundation.
+ */
+
+#include "ccid.h"
+
+static struct ccid *ccids[CCID_MAX];
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
+static atomic_t ccids_lockct = ATOMIC_INIT(0);
+static DEFINE_SPINLOCK(ccids_lock);
+
+/*
+ * The strategy is: modifications ccids vector are short, do not sleep and
+ * veeery rare, but read access should be free of any exclusive locks.
+ */
+static void ccids_write_lock(void)
+{
+        spin_lock(&ccids_lock);
+        while (atomic_read(&ccids_lockct) != 0) {
+                spin_unlock(&ccids_lock);
+                yield();
+                spin_lock(&ccids_lock);
+        }
+}
+
+static inline void ccids_write_unlock(void)
+{
+        spin_unlock(&ccids_lock);
+}
+
+static inline void ccids_read_lock(void)
+{
+        atomic_inc(&ccids_lockct);
+        spin_unlock_wait(&ccids_lock);
+}
+
+static inline void ccids_read_unlock(void)
+{
+        atomic_dec(&ccids_lockct);
+}
+
+#else
+#define ccids_write_lock() do { } while(0)
+#define ccids_write_unlock() do { } while(0)
+#define ccids_read_lock() do { } while(0)
+#define ccids_read_unlock() do { } while(0)
+#endif
+
+int ccid_register(struct ccid *ccid)
+{
+        int err;
+
+        if (ccid->ccid_init == NULL)
+                return -1;
+
+        ccids_write_lock();
+        err = -EEXIST;
+        if (ccids[ccid->ccid_id] == NULL) {
+                ccids[ccid->ccid_id] = ccid;
+                err = 0;
+        }
+        ccids_write_unlock();
+        if (err == 0)
+                pr_info("CCID: Registered CCID %d (%s)\n",
+                        ccid->ccid_id, ccid->ccid_name);
+        return err;
+}
+
+EXPORT_SYMBOL_GPL(ccid_register);
+
+int ccid_unregister(struct ccid *ccid)
+{
+        ccids_write_lock();
+        ccids[ccid->ccid_id] = NULL;
+        ccids_write_unlock();
+        pr_info("CCID: Unregistered CCID %d (%s)\n",
+                ccid->ccid_id, ccid->ccid_name);
+        return 0;
+}
+
+EXPORT_SYMBOL_GPL(ccid_unregister);
+
+struct ccid *ccid_init(unsigned char id, struct sock *sk)
+{
+        struct ccid *ccid;
+
+#ifdef CONFIG_KMOD
+        if (ccids[id] == NULL)
+                request_module("net-dccp-ccid-%d", id);
+#endif
+        ccids_read_lock();
+
+        ccid = ccids[id];
+        if (ccid == NULL)
+                goto out;
+
+        if (!try_module_get(ccid->ccid_owner))
+                goto out_err;
+
+        if (ccid->ccid_init(sk) != 0)
+                goto out_module_put;
+out:
+        ccids_read_unlock();
+        return ccid;
+out_module_put:
+        module_put(ccid->ccid_owner);
+out_err:
+        ccid = NULL;
+        goto out;
+}
+
+EXPORT_SYMBOL_GPL(ccid_init);
+
+void ccid_exit(struct ccid *ccid, struct sock *sk)
+{
+        if (ccid == NULL)
+                return;
+
+        ccids_read_lock();
+
+        if (ccids[ccid->ccid_id] != NULL) {
+                if (ccid->ccid_exit != NULL)
+                        ccid->ccid_exit(sk);
+                module_put(ccid->ccid_owner);
+        }
+
+        ccids_read_unlock();
+}
+
+EXPORT_SYMBOL_GPL(ccid_exit);