[net-next v4 3/6] net: Add UDP ULP operations, initialization and handling prototype functions.

[Adel Abouchaev <adel.abushaev@gmail.com>]

Define functions to add UDP ULP handling, registration with UDP protocol
and supporting data structures. Create structure for QUIC ULP and add empty
prototype functions to support it.

Signed-off-by: Adel Abouchaev <adel.abushaev@gmail.com>

---

Removed reference to net/quic/Kconfig from this patch into the next.

Fixed formatting around brackets.
---
 include/net/inet_sock.h  |   2 +
 include/net/udp.h        |  33 +++++++
 include/uapi/linux/udp.h |   1 +
 net/Makefile             |   1 +
 net/ipv4/Makefile        |   3 +-
 net/ipv4/udp.c           |   6 ++
 net/ipv4/udp_ulp.c       | 192 +++++++++++++++++++++++++++++++++++++++
 7 files changed, 237 insertions(+), 1 deletion(-)
 create mode 100644 net/ipv4/udp_ulp.c

diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index bf5654ce711e..650e332bdb50 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -249,6 +249,8 @@ struct inet_sock {
 	__be32			mc_addr;
 	struct ip_mc_socklist __rcu	*mc_list;
 	struct inet_cork_full	cork;
+	const struct udp_ulp_ops	*udp_ulp_ops;
+	void __rcu		*ulp_data;
 };
 
 #define IPCORK_OPT	1	/* ip-options has been held in ipcork.opt */
diff --git a/include/net/udp.h b/include/net/udp.h
index 5ee88ddf79c3..f22ebabbb186 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -523,4 +523,37 @@ struct proto *udp_bpf_get_proto(struct sock *sk, struct sk_psock *psock);
 int udp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
 #endif
 
+/*
+ * Interface for adding Upper Level Protocols over UDP
+ */
+
+#define UDP_ULP_NAME_MAX	16
+#define UDP_ULP_MAX		128
+
+struct udp_ulp_ops {
+	struct list_head	list;
+
+	/* initialize ulp */
+	int (*init)(struct sock *sk);
+	/* cleanup ulp */
+	void (*release)(struct sock *sk);
+
+	char		name[UDP_ULP_NAME_MAX];
+	struct module	*owner;
+};
+
+int udp_register_ulp(struct udp_ulp_ops *type);
+void udp_unregister_ulp(struct udp_ulp_ops *type);
+int udp_set_ulp(struct sock *sk, const char *name);
+void udp_get_available_ulp(char *buf, size_t len);
+void udp_cleanup_ulp(struct sock *sk);
+int udp_setsockopt_ulp(struct sock *sk, sockptr_t optval,
+		       unsigned int optlen);
+int udp_getsockopt_ulp(struct sock *sk, char __user *optval,
+		       int __user *optlen);
+
+#define MODULE_ALIAS_UDP_ULP(name)\
+	__MODULE_INFO(alias, alias_userspace, name);\
+	__MODULE_INFO(alias, alias_udp_ulp, "udp-ulp-" name)
+
 #endif	/* _UDP_H */
diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h
index 0ee4c598e70b..893691f0108a 100644
--- a/include/uapi/linux/udp.h
+++ b/include/uapi/linux/udp.h
@@ -34,6 +34,7 @@ struct udphdr {
 #define UDP_NO_CHECK6_RX 102	/* Disable accpeting checksum for UDP6 */
 #define UDP_SEGMENT	103	/* Set GSO segmentation size */
 #define UDP_GRO		104	/* This socket can receive UDP GRO packets */
+#define UDP_ULP		105	/* Attach ULP to a UDP socket */
 #define UDP_QUIC_ADD_TX_CONNECTION	106 /* Add QUIC Tx crypto offload */
 #define UDP_QUIC_DEL_TX_CONNECTION	107 /* Del QUIC Tx crypto offload */
 #define UDP_QUIC_ENCRYPT		108 /* QUIC encryption parameters */
diff --git a/net/Makefile b/net/Makefile
index 6a62e5b27378..021ea3698d3a 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -16,6 +16,7 @@ obj-y				+= ethernet/ 802/ sched/ netlink/ bpf/ ethtool/
 obj-$(CONFIG_NETFILTER)		+= netfilter/
 obj-$(CONFIG_INET)		+= ipv4/
 obj-$(CONFIG_TLS)		+= tls/
+obj-$(CONFIG_QUIC)		+= quic/
 obj-$(CONFIG_XFRM)		+= xfrm/
 obj-$(CONFIG_UNIX_SCM)		+= unix/
 obj-y				+= ipv6/
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index bbdd9c44f14e..88d3baf4af95 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -14,7 +14,8 @@ obj-y     := route.o inetpeer.o protocol.o \
 	     udp_offload.o arp.o icmp.o devinet.o af_inet.o igmp.o \
 	     fib_frontend.o fib_semantics.o fib_trie.o fib_notifier.o \
 	     inet_fragment.o ping.o ip_tunnel_core.o gre_offload.o \
-	     metrics.o netlink.o nexthop.o udp_tunnel_stub.o
+	     metrics.o netlink.o nexthop.o udp_tunnel_stub.o \
+	     udp_ulp.o
 
 obj-$(CONFIG_BPFILTER) += bpfilter/
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index cd72158e953a..0f5c842dbd3f 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2781,6 +2781,9 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 		up->pcflag |= UDPLITE_RECV_CC;
 		break;
 
+	case UDP_ULP:
+		return udp_setsockopt_ulp(sk, optval, optlen);
+
 	default:
 		err = -ENOPROTOOPT;
 		break;
@@ -2849,6 +2852,9 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
 		val = up->pcrlen;
 		break;
 
+	case UDP_ULP:
+		return udp_getsockopt_ulp(sk, optval, optlen);
+
 	default:
 		return -ENOPROTOOPT;
 	}
diff --git a/net/ipv4/udp_ulp.c b/net/ipv4/udp_ulp.c
new file mode 100644
index 000000000000..138818690151
--- /dev/null
+++ b/net/ipv4/udp_ulp.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Pluggable UDP upper layer protocol support, based on 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.
+ * Copyright (c) 2021-2022, Meta Platforms, Inc. All rights reserved.
+ */
+
+#include <linux/gfp.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/types.h>
+#include <linux/skmsg.h>
+#include <net/tcp.h>
+#include <net/udp.h>
+
+static DEFINE_SPINLOCK(udp_ulp_list_lock);
+static LIST_HEAD(udp_ulp_list);
+
+/* Simple linear search, don't expect many entries! */
+static struct udp_ulp_ops *udp_ulp_find(const char *name)
+{
+	struct udp_ulp_ops *e;
+
+	list_for_each_entry_rcu(e, &udp_ulp_list, list,
+				lockdep_is_held(&udp_ulp_list_lock)) {
+		if (strcmp(e->name, name) == 0)
+			return e;
+	}
+
+	return NULL;
+}
+
+static const struct udp_ulp_ops *__udp_ulp_find_autoload(const char *name)
+{
+	const struct udp_ulp_ops *ulp = NULL;
+
+	rcu_read_lock();
+	ulp = udp_ulp_find(name);
+
+#ifdef CONFIG_MODULES
+	if (!ulp && capable(CAP_NET_ADMIN)) {
+		rcu_read_unlock();
+		request_module("udp-ulp-%s", name);
+		rcu_read_lock();
+		ulp = udp_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 udp_register_ulp(struct udp_ulp_ops *ulp)
+{
+	int ret = 0;
+
+	spin_lock(&udp_ulp_list_lock);
+	if (udp_ulp_find(ulp->name))
+		ret = -EEXIST;
+	else
+		list_add_tail_rcu(&ulp->list, &udp_ulp_list);
+
+	spin_unlock(&udp_ulp_list_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(udp_register_ulp);
+
+void udp_unregister_ulp(struct udp_ulp_ops *ulp)
+{
+	spin_lock(&udp_ulp_list_lock);
+	list_del_rcu(&ulp->list);
+	spin_unlock(&udp_ulp_list_lock);
+
+	synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(udp_unregister_ulp);
+
+void udp_cleanup_ulp(struct sock *sk)
+{
+	struct inet_sock *inet = inet_sk(sk);
+
+	/* No sock_owned_by_me() check here as at the time the
+	 * stack calls this function, the socket is dead and
+	 * about to be destroyed.
+	 */
+	if (!inet->udp_ulp_ops)
+		return;
+
+	if (inet->udp_ulp_ops->release)
+		inet->udp_ulp_ops->release(sk);
+	module_put(inet->udp_ulp_ops->owner);
+
+	inet->udp_ulp_ops = NULL;
+}
+
+static int __udp_set_ulp(struct sock *sk, const struct udp_ulp_ops *ulp_ops)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	int err;
+
+	err = -EEXIST;
+	if (inet->udp_ulp_ops)
+		goto out_err;
+
+	err = ulp_ops->init(sk);
+	if (err)
+		goto out_err;
+
+	inet->udp_ulp_ops = ulp_ops;
+	return 0;
+
+out_err:
+	module_put(ulp_ops->owner);
+	return err;
+}
+
+int udp_set_ulp(struct sock *sk, const char *name)
+{
+	struct sk_psock *psock = sk_psock_get(sk);
+	const struct udp_ulp_ops *ulp_ops;
+
+	if (psock) {
+		sk_psock_put(sk, psock);
+		return -EINVAL;
+	}
+
+	sock_owned_by_me(sk);
+	ulp_ops = __udp_ulp_find_autoload(name);
+	if (!ulp_ops)
+		return -ENOENT;
+
+	return __udp_set_ulp(sk, ulp_ops);
+}
+
+int udp_setsockopt_ulp(struct sock *sk, sockptr_t optval, unsigned int optlen)
+{
+	char name[UDP_ULP_NAME_MAX];
+	int val, err;
+
+	if (!optlen || optlen > UDP_ULP_NAME_MAX)
+		return -EINVAL;
+
+	val = strncpy_from_sockptr(name, optval, optlen);
+	if (val < 0)
+		return -EFAULT;
+
+	if (val == UDP_ULP_NAME_MAX)
+		return -EINVAL;
+
+	name[val] = 0;
+	lock_sock(sk);
+	err = udp_set_ulp(sk, name);
+	release_sock(sk);
+	return err;
+}
+
+int udp_getsockopt_ulp(struct sock *sk, char __user *optval, int __user *optlen)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	int len;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	len = min_t(unsigned int, len, UDP_ULP_NAME_MAX);
+	if (len < 0)
+		return -EINVAL;
+
+	if (!inet->udp_ulp_ops) {
+		if (put_user(0, optlen))
+			return -EFAULT;
+		return 0;
+	}
+
+	if (put_user(len, optlen))
+		return -EFAULT;
+	if (copy_to_user(optval, inet->udp_ulp_ops->name, len))
+		return -EFAULT;
+
+	return 0;
+}
-- 
2.30.2