tcp: ULP infrastructure
Add the infrustructure for attaching Upper Layer Protocols (ULPs) over TCP
sockets. Based on a similar infrastructure in tcp_cong. The idea is that any
ULP can add its own logic by changing the TCP proto_ops structure to its own
methods.
Example usage:
setsockopt(sock, SOL_TCP, TCP_ULP, "tls", sizeof("tls"));
modules will call:
tcp_register_ulp(&tcp_tls_ulp_ops);
to register/unregister their ulp, with an init function and name.
A list of registered ulps will be returned by tcp_get_available_ulp, which is
hooked up to /proc. Example:
$ cat /proc/sys/net/ipv4/tcp_available_ulp
tls
There is currently no functionality to remove or chain ULPs, but
it should be possible to add these in the future if needed.
Signed-off-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_ulp.c b/net/ipv4/tcp_ulp.c
new file mode 100644
index 0000000..e855ea7
--- /dev/null
+++ b/net/ipv4/tcp_ulp.c
@@ -0,0 +1,134 @@
+/*
+ * Pluggable TCP upper layer protocol support.
+ *
+ * Copyright (c) 2016-2017, Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016-2017, Dave Watson <davejwatson@fb.com>. All rights reserved.
+ *
+ */
+
+#include<linux/module.h>
+#include <linux/mm.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/gfp.h>
+#include <net/tcp.h>
+
+static DEFINE_SPINLOCK(tcp_ulp_list_lock);
+static LIST_HEAD(tcp_ulp_list);
+
+/* Simple linear search, don't expect many entries! */
+static struct tcp_ulp_ops *tcp_ulp_find(const char *name)
+{
+ struct tcp_ulp_ops *e;
+
+ list_for_each_entry_rcu(e, &tcp_ulp_list, list) {
+ if (strcmp(e->name, name) == 0)
+ return e;
+ }
+
+ return NULL;
+}
+
+static const struct tcp_ulp_ops *__tcp_ulp_find_autoload(const char *name)
+{
+ const struct tcp_ulp_ops *ulp = NULL;
+
+ rcu_read_lock();
+ ulp = tcp_ulp_find(name);
+
+#ifdef CONFIG_MODULES
+ if (!ulp && capable(CAP_NET_ADMIN)) {
+ rcu_read_unlock();
+ request_module("%s", name);
+ rcu_read_lock();
+ ulp = tcp_ulp_find(name);
+ }
+#endif
+ if (!ulp || !try_module_get(ulp->owner))
+ ulp = NULL;
+
+ rcu_read_unlock();
+ return ulp;
+}
+
+/* Attach new upper layer protocol to the list
+ * of available protocols.
+ */
+int tcp_register_ulp(struct tcp_ulp_ops *ulp)
+{
+ int ret = 0;
+
+ spin_lock(&tcp_ulp_list_lock);
+ if (tcp_ulp_find(ulp->name)) {
+ pr_notice("%s already registered or non-unique name\n",
+ ulp->name);
+ ret = -EEXIST;
+ } else {
+ list_add_tail_rcu(&ulp->list, &tcp_ulp_list);
+ }
+ spin_unlock(&tcp_ulp_list_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(tcp_register_ulp);
+
+void tcp_unregister_ulp(struct tcp_ulp_ops *ulp)
+{
+ spin_lock(&tcp_ulp_list_lock);
+ list_del_rcu(&ulp->list);
+ spin_unlock(&tcp_ulp_list_lock);
+
+ synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(tcp_unregister_ulp);
+
+/* Build string with list of available upper layer protocl values */
+void tcp_get_available_ulp(char *buf, size_t maxlen)
+{
+ struct tcp_ulp_ops *ulp_ops;
+ size_t offs = 0;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(ulp_ops, &tcp_ulp_list, list) {
+ offs += snprintf(buf + offs, maxlen - offs,
+ "%s%s",
+ offs == 0 ? "" : " ", ulp_ops->name);
+ }
+ rcu_read_unlock();
+}
+
+void tcp_cleanup_ulp(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+
+ if (!icsk->icsk_ulp_ops)
+ return;
+
+ if (icsk->icsk_ulp_ops->release)
+ icsk->icsk_ulp_ops->release(sk);
+ module_put(icsk->icsk_ulp_ops->owner);
+}
+
+/* Change upper layer protocol for socket */
+int tcp_set_ulp(struct sock *sk, const char *name)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ const struct tcp_ulp_ops *ulp_ops;
+ int err = 0;
+
+ if (icsk->icsk_ulp_ops)
+ return -EEXIST;
+
+ ulp_ops = __tcp_ulp_find_autoload(name);
+ if (!ulp_ops)
+ err = -ENOENT;
+ else
+ err = ulp_ops->init(sk);
+
+ if (err)
+ goto out;
+
+ icsk->icsk_ulp_ops = ulp_ops;
+ out:
+ return err;
+}