xsk: add user memory registration support sockopt

In this commit the base structure of the AF_XDP address family is set
up. Further, we introduce the abilty register a window of user memory
to the kernel via the XDP_UMEM_REG setsockopt syscall. The memory
window is viewed by an AF_XDP socket as a set of equally large
frames. After a user memory registration all frames are "owned" by the
user application, and not the kernel.

v2: More robust checks on umem creation and unaccount on error.
    Call set_page_dirty_lock on cleanup.
    Simplified xdp_umem_reg.

Co-authored-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 215 insertions, 0 deletions

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
new file mode 100644
index 000000000000..84e0e867febb
--- /dev/null
+++ b/net/xdp/xsk.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0
+/* XDP sockets
+ *
+ * AF_XDP sockets allows a channel between XDP programs and userspace
+ * applications.
+ * Copyright(c) 2018 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * Author(s): Björn Töpel <bjorn.topel@intel.com>
+ *	      Magnus Karlsson <magnus.karlsson@intel.com>
+ */
+
+#define pr_fmt(fmt) "AF_XDP: %s: " fmt, __func__
+
+#include <linux/if_xdp.h>
+#include <linux/init.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/socket.h>
+#include <linux/file.h>
+#include <linux/uaccess.h>
+#include <linux/net.h>
+#include <linux/netdevice.h>
+#include <net/xdp_sock.h>
+
+#include "xdp_umem.h"
+
+static struct xdp_sock *xdp_sk(struct sock *sk)
+{
+	return (struct xdp_sock *)sk;
+}
+
+static int xsk_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct net *net;
+
+	if (!sk)
+		return 0;
+
+	net = sock_net(sk);
+
+	local_bh_disable();
+	sock_prot_inuse_add(net, sk->sk_prot, -1);
+	local_bh_enable();
+
+	sock_orphan(sk);
+	sock->sk = NULL;
+
+	sk_refcnt_debug_release(sk);
+	sock_put(sk);
+
+	return 0;
+}
+
+static int xsk_setsockopt(struct socket *sock, int level, int optname,
+			  char __user *optval, unsigned int optlen)
+{
+	struct sock *sk = sock->sk;
+	struct xdp_sock *xs = xdp_sk(sk);
+	int err;
+
+	if (level != SOL_XDP)
+		return -ENOPROTOOPT;
+
+	switch (optname) {
+	case XDP_UMEM_REG:
+	{
+		struct xdp_umem_reg mr;
+		struct xdp_umem *umem;
+
+		if (xs->umem)
+			return -EBUSY;
+
+		if (copy_from_user(&mr, optval, sizeof(mr)))
+			return -EFAULT;
+
+		mutex_lock(&xs->mutex);
+		err = xdp_umem_create(&umem);
+
+		err = xdp_umem_reg(umem, &mr);
+		if (err) {
+			kfree(umem);
+			mutex_unlock(&xs->mutex);
+			return err;
+		}
+
+		/* Make sure umem is ready before it can be seen by others */
+		smp_wmb();
+
+		xs->umem = umem;
+		mutex_unlock(&xs->mutex);
+		return 0;
+	}
+	default:
+		break;
+	}
+
+	return -ENOPROTOOPT;
+}
+
+static struct proto xsk_proto = {
+	.name =		"XDP",
+	.owner =	THIS_MODULE,
+	.obj_size =	sizeof(struct xdp_sock),
+};
+
+static const struct proto_ops xsk_proto_ops = {
+	.family =	PF_XDP,
+	.owner =	THIS_MODULE,
+	.release =	xsk_release,
+	.bind =		sock_no_bind,
+	.connect =	sock_no_connect,
+	.socketpair =	sock_no_socketpair,
+	.accept =	sock_no_accept,
+	.getname =	sock_no_getname,
+	.poll =		sock_no_poll,
+	.ioctl =	sock_no_ioctl,
+	.listen =	sock_no_listen,
+	.shutdown =	sock_no_shutdown,
+	.setsockopt =	xsk_setsockopt,
+	.getsockopt =	sock_no_getsockopt,
+	.sendmsg =	sock_no_sendmsg,
+	.recvmsg =	sock_no_recvmsg,
+	.mmap =		sock_no_mmap,
+	.sendpage =	sock_no_sendpage,
+};
+
+static void xsk_destruct(struct sock *sk)
+{
+	struct xdp_sock *xs = xdp_sk(sk);
+
+	if (!sock_flag(sk, SOCK_DEAD))
+		return;
+
+	xdp_put_umem(xs->umem);
+
+	sk_refcnt_debug_dec(sk);
+}
+
+static int xsk_create(struct net *net, struct socket *sock, int protocol,
+		      int kern)
+{
+	struct sock *sk;
+	struct xdp_sock *xs;
+
+	if (!ns_capable(net->user_ns, CAP_NET_RAW))
+		return -EPERM;
+	if (sock->type != SOCK_RAW)
+		return -ESOCKTNOSUPPORT;
+
+	if (protocol)
+		return -EPROTONOSUPPORT;
+
+	sock->state = SS_UNCONNECTED;
+
+	sk = sk_alloc(net, PF_XDP, GFP_KERNEL, &xsk_proto, kern);
+	if (!sk)
+		return -ENOBUFS;
+
+	sock->ops = &xsk_proto_ops;
+
+	sock_init_data(sock, sk);
+
+	sk->sk_family = PF_XDP;
+
+	sk->sk_destruct = xsk_destruct;
+	sk_refcnt_debug_inc(sk);
+
+	xs = xdp_sk(sk);
+	mutex_init(&xs->mutex);
+
+	local_bh_disable();
+	sock_prot_inuse_add(net, &xsk_proto, 1);
+	local_bh_enable();
+
+	return 0;
+}
+
+static const struct net_proto_family xsk_family_ops = {
+	.family = PF_XDP,
+	.create = xsk_create,
+	.owner	= THIS_MODULE,
+};
+
+static int __init xsk_init(void)
+{
+	int err;
+
+	err = proto_register(&xsk_proto, 0 /* no slab */);
+	if (err)
+		goto out;
+
+	err = sock_register(&xsk_family_ops);
+	if (err)
+		goto out_proto;
+
+	return 0;
+
+out_proto:
+	proto_unregister(&xsk_proto);
+out:
+	return err;
+}
+
+fs_initcall(xsk_init);