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Message-Id: <20180327165919.17933-6-bjorn.topel@gmail.com>
Date:   Tue, 27 Mar 2018 18:59:10 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     bjorn.topel@...il.com, magnus.karlsson@...el.com,
        alexander.h.duyck@...el.com, alexander.duyck@...il.com,
        john.fastabend@...il.com, ast@...com, brouer@...hat.com,
        willemdebruijn.kernel@...il.com, daniel@...earbox.net,
        netdev@...r.kernel.org
Cc:     michael.lundkvist@...csson.com, jesse.brandeburg@...el.com,
        anjali.singhai@...el.com, qi.z.zhang@...el.com,
        ravineet.singh@...csson.com
Subject: [RFC PATCH v2 05/14] xsk: add support for bind for Rx

From: Magnus Karlsson <magnus.karlsson@...el.com>

Here, the bind syscall is added. Binding an AF_XDP socket, means
associating the socket to an umem, a netdev and a queue index. This
can be done in two ways.

The first way, creating a "socket from scratch". Create the umem using
the XDP_UMEM_REG setsockopt and an associated fill queue with
XDP_UMEM_FILL_QUEUE. Create the Rx queue using the XDP_RX_QUEUE
setsockopt. Call bind passing ifindex and queue index ("channel" in
ethtool speak).

The second way to bind a socket, is simply skipping the
umem/netdev/queue index, and passing another already setup AF_XDP
socket. The new socket will then have the same umem/netdev/queue index
as the parent so it will share the same umem. You must also set the
flags field in the socket address to XDP_SHARED_UMEM.

Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
---
 include/uapi/linux/if_xdp.h |  11 ++++
 net/xdp/xdp_umem.c          |   9 ++++
 net/xdp/xdp_umem.h          |   2 +
 net/xdp/xsk.c               | 125 +++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 146 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
index 118456064e01..e3593df7323c 100644
--- a/include/uapi/linux/if_xdp.h
+++ b/include/uapi/linux/if_xdp.h
@@ -20,6 +20,17 @@
 
 #include <linux/types.h>
 
+/* Options for the sxdp_flags field */
+#define XDP_SHARED_UMEM 1
+
+struct sockaddr_xdp {
+	__u16 sxdp_family;
+	__u32 sxdp_ifindex;
+	__u32 sxdp_queue_id;
+	__u32 sxdp_shared_umem_fd;
+	__u16 sxdp_flags;
+};
+
 /* XDP socket options */
 #define XDP_RX_QUEUE		  1
 #define XDP_UMEM_REG		  3
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index f2c0768ca63e..96395beb980e 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -97,6 +97,11 @@ static void xdp_umem_release(struct xdp_umem *umem)
 	kfree(umem);
 }
 
+void xdp_get_umem(struct xdp_umem *umem)
+{
+	atomic_inc(&umem->users);
+}
+
 void xdp_put_umem(struct xdp_umem *umem)
 {
 	if (!umem)
@@ -243,3 +248,7 @@ int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	return err;
 }
 
+bool xdp_umem_validate_queues(struct xdp_umem *umem)
+{
+	return umem->fq;
+}
diff --git a/net/xdp/xdp_umem.h b/net/xdp/xdp_umem.h
index b3538dd2118c..ad041b911b38 100644
--- a/net/xdp/xdp_umem.h
+++ b/net/xdp/xdp_umem.h
@@ -36,7 +36,9 @@ struct xdp_umem {
 	struct user_struct *user;
 };
 
+bool xdp_umem_validate_queues(struct xdp_umem *umem);
 int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr);
+void xdp_get_umem(struct xdp_umem *umem);
 void xdp_put_umem(struct xdp_umem *umem);
 int xdp_umem_create(struct xdp_umem **umem);
 
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index f82f750cadc2..d99a1b830f94 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -43,6 +43,8 @@ struct xdp_sock {
 	/* Protects multiple processes in the control path */
 	struct mutex mutex;
 	struct xdp_umem *umem;
+	u32 ifindex;
+	u16 queue_id;
 };
 
 static struct xdp_sock *xdp_sk(struct sock *sk)
@@ -66,9 +68,18 @@ static int xsk_init_queue(u32 entries, struct xsk_queue **queue,
 	return 0;
 }
 
+static void __xsk_release(struct xdp_sock *xs)
+{
+	/* Wait for driver to stop using the xdp socket. */
+	synchronize_net();
+
+	dev_put(xs->dev);
+}
+
 static int xsk_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
+	struct xdp_sock *xs = xdp_sk(sk);
 	struct net *net;
 
 	if (!sk)
@@ -80,6 +91,11 @@ static int xsk_release(struct socket *sock)
 	sock_prot_inuse_add(net, sk->sk_prot, -1);
 	local_bh_enable();
 
+	if (xs->dev) {
+		__xsk_release(xs);
+		xs->dev = NULL;
+	}
+
 	sock_orphan(sk);
 	sock->sk = NULL;
 
@@ -89,6 +105,113 @@ static int xsk_release(struct socket *sock)
 	return 0;
 }
 
+static struct socket *xsk_lookup_xsk_from_fd(int fd, int *err)
+{
+	struct socket *sock;
+
+	*err = -ENOTSOCK;
+	sock = sockfd_lookup(fd, err);
+	if (!sock)
+		return NULL;
+
+	if (sock->sk->sk_family != PF_XDP) {
+		*err = -ENOPROTOOPT;
+		sockfd_put(sock);
+		return NULL;
+	}
+
+	*err = 0;
+	return sock;
+}
+
+static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
+{
+	struct sockaddr_xdp *sxdp = (struct sockaddr_xdp *)addr;
+	struct sock *sk = sock->sk;
+	struct net_device *dev, *dev_curr;
+	struct xdp_sock *xs = xdp_sk(sk);
+	struct xdp_umem *old_umem = NULL;
+	int err = 0;
+
+	if (addr_len < sizeof(struct sockaddr_xdp))
+		return -EINVAL;
+	if (sxdp->sxdp_family != AF_XDP)
+		return -EINVAL;
+
+	mutex_lock(&xs->mutex);
+	dev_curr = xs->dev;
+	dev = dev_get_by_index(sock_net(sk), sxdp->sxdp_ifindex);
+	if (!dev) {
+		err = -ENODEV;
+		goto out_release;
+	}
+
+	if (!xs->rx) {
+		err = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (sxdp->sxdp_queue_id >= dev->num_rx_queues) {
+		err = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (sxdp->sxdp_flags & XDP_SHARED_UMEM) {
+		struct xdp_sock *umem_xs;
+		struct socket *sock;
+
+		if (xs->umem) {
+			/* We have already our own. */
+			err = -EINVAL;
+			goto out_unlock;
+		}
+
+		sock = xsk_lookup_xsk_from_fd(sxdp->sxdp_shared_umem_fd, &err);
+		if (!sock)
+			goto out_unlock;
+
+		umem_xs = xdp_sk(sock->sk);
+		if (!umem_xs->umem) {
+			/* No umem to inherit. */
+			err = -EBADF;
+			sockfd_put(sock);
+			goto out_unlock;
+		} else if (umem_xs->dev != dev ||
+			   umem_xs->queue_id != sxdp->sxdp_queue_id) {
+			err = -EINVAL;
+			sockfd_put(sock);
+			goto out_unlock;
+		}
+
+		xdp_get_umem(umem_xs->umem);
+		old_umem = xs->umem;
+		xs->umem = umem_xs->umem;
+		sockfd_put(sock);
+	} else if (!xs->umem || !xdp_umem_validate_queues(xs->umem)) {
+		err = -EINVAL;
+		goto out_unlock;
+	}
+
+	/* Rebind? */
+	if (dev_curr && (dev_curr != dev ||
+			 xs->queue_id != sxdp->sxdp_queue_id)) {
+		__xsk_release(xs);
+		if (old_umem)
+			xdp_put_umem(old_umem);
+	}
+
+	xs->dev = dev;
+	xs->ifindex = sxdp->sxdp_ifindex;
+	xs->queue_id = sxdp->sxdp_queue_id;
+
+out_unlock:
+	if (err)
+		dev_put(dev);
+out_release:
+	mutex_unlock(&xs->mutex);
+	return err;
+}
+
 static int xsk_setsockopt(struct socket *sock, int level, int optname,
 			  char __user *optval, unsigned int optlen)
 {
@@ -212,7 +335,7 @@ static const struct proto_ops xsk_proto_ops = {
 	.family =	PF_XDP,
 	.owner =	THIS_MODULE,
 	.release =	xsk_release,
-	.bind =		sock_no_bind,
+	.bind =		xsk_bind,
 	.connect =	sock_no_connect,
 	.socketpair =	sock_no_socketpair,
 	.accept =	sock_no_accept,
-- 
2.14.1

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