Date:   Wed, 23 Jan 2019 14:19:49 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     bjorn.topel@...il.com, ast@...nel.org, netdev@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        magnus.karlsson@...el.com, magnus.karlsson@...il.com
Subject: Re: [PATCH bpf-next 3/3] xsk: add sock_diag interface for AF_XDP

On 01/18/2019 02:03 PM, bjorn.topel@...il.com wrote:
> From: Björn Töpel <bjorn.topel@...el.com>
> 
> This patch adds the sock_diag interface for querying sockets from user
> space. Tools like iproute2 ss(8) can use this interface to list open
> AF_XDP sockets.
> 
> The user-space ABI is defined in linux/xdp_diag.h and includes netlink
> request and response structs. The request can query sockets and the
> response contains socket information about the rings, umems, inode and
> more.
> 
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>

Series looks good, few minor nits inline:

> ---
>  include/uapi/linux/xdp_diag.h |  72 +++++++++++++
>  net/xdp/Kconfig               |   8 ++
>  net/xdp/Makefile              |   1 +
>  net/xdp/xsk.c                 |   6 +-
>  net/xdp/xsk.h                 |  12 +++
>  net/xdp/xsk_diag.c            | 192 ++++++++++++++++++++++++++++++++++
>  6 files changed, 286 insertions(+), 5 deletions(-)
>  create mode 100644 include/uapi/linux/xdp_diag.h
>  create mode 100644 net/xdp/xsk.h
>  create mode 100644 net/xdp/xsk_diag.c
> 
> diff --git a/include/uapi/linux/xdp_diag.h b/include/uapi/linux/xdp_diag.h
> new file mode 100644
> index 000000000000..efe8ce281dce
> --- /dev/null
> +++ b/include/uapi/linux/xdp_diag.h
> @@ -0,0 +1,72 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + * xdp_diag: interface for query/monitor XDP sockets
> + * Copyright(c) 2019 Intel Corporation.
> + */
> +
> +#ifndef _LINUX_XDP_DIAG_H
> +#define _LINUX_XDP_DIAG_H
> +
> +#include <linux/types.h>
> +
> +struct xdp_diag_req {
> +	__u8	sdiag_family;
> +	__u8	sdiag_protocol;
> +	__u16	pad;

Presumably this one is for future use? Maybe better as '__u16 :16;' to
avoid compile errors if someone tries to zero 'pad' member manually?

> +	__u32	xdiag_ino;
> +	__u32	xdiag_show;
> +	__u32	xdiag_cookie[2];
> +};
> +
> +struct xdp_diag_msg {
> +	__u8	xdiag_family;
> +	__u8	xdiag_type;
> +	__u32	xdiag_ino;
> +	__u32	xdiag_cookie[2];
> +};
> +
> +#define XDP_SHOW_INFO		(1 << 0) /* Basic information */
> +#define XDP_SHOW_RING_CFG	(1 << 1)
> +#define XDP_SHOW_UMEM		(1 << 2)
> +#define XDP_SHOW_MEMINFO	(1 << 3)
> +
> +enum {
> +	XDP_DIAG_NONE,
> +	XDP_DIAG_INFO,
> +	XDP_DIAG_UID,
> +	XDP_DIAG_RX_RING,
> +	XDP_DIAG_TX_RING,
> +	XDP_DIAG_UMEM,
> +	XDP_DIAG_UMEM_FILL_RING,
> +	XDP_DIAG_UMEM_COMPLETION_RING,
> +	XDP_DIAG_MEMINFO,
> +	__XDP_DIAG_MAX,
> +};
> +
> +#define XDP_DIAG_MAX (__XDP_DIAG_MAX - 1)
> +
> +struct xdp_diag_info {
> +	__u32	ifindex;
> +	__u32	queue_id;
> +};
> +
> +struct xdp_diag_ring {
> +	__u32	entries; /*num descs */
> +};
> +
> +#define XDP_DU_F_ZEROCOPY (1 << 0)
> +
> +struct xdp_diag_umem {
> +	__u64	size;
> +	__u32	id;
> +	__u32	num_pages;
> +	__u32	chunk_size;
> +	__u32	headroom;
> +	__u32	ifindex;
> +	__u32	queue_id;
> +	__u32	flags;
> +	__u32	refs;
> +};
> +
> +

Nit: one newline too much

> +#endif /* _LINUX_XDP_DIAG_H */
> diff --git a/net/xdp/Kconfig b/net/xdp/Kconfig
> index 90e4a7152854..0255b33cff4b 100644
> --- a/net/xdp/Kconfig
> +++ b/net/xdp/Kconfig
> @@ -5,3 +5,11 @@ config XDP_SOCKETS
>  	help
>  	  XDP sockets allows a channel between XDP programs and
>  	  userspace applications.
> +
> +config XDP_SOCKETS_DIAG
> +	tristate "XDP sockets: monitoring interface"
> +	depends on XDP_SOCKETS
> +	default n
> +	help
> +	  Support for PF_XDP sockets monitoring interface used by the ss tool.
> +	  If unsure, say Y.
> diff --git a/net/xdp/Makefile b/net/xdp/Makefile
> index 04f073146256..59dbfdf93dca 100644
> --- a/net/xdp/Makefile
> +++ b/net/xdp/Makefile
> @@ -1 +1,2 @@
>  obj-$(CONFIG_XDP_SOCKETS) += xsk.o xdp_umem.o xsk_queue.o
> +obj-$(CONFIG_XDP_SOCKETS_DIAG) += xsk_diag.o
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 80ca48cefc42..949d3bbccb2f 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -27,14 +27,10 @@
>  
>  #include "xsk_queue.h"
>  #include "xdp_umem.h"
> +#include "xsk.h"
>  
>  #define TX_BATCH_SIZE 16
>  
> -static struct xdp_sock *xdp_sk(struct sock *sk)
> -{
> -	return (struct xdp_sock *)sk;
> -}
> -
>  bool xsk_is_setup_for_bpf_map(struct xdp_sock *xs)
>  {
>  	return READ_ONCE(xs->rx) &&  READ_ONCE(xs->umem) &&
> diff --git a/net/xdp/xsk.h b/net/xdp/xsk.h
> new file mode 100644
> index 000000000000..ba8120610426
> --- /dev/null
> +++ b/net/xdp/xsk.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright(c) 2019 Intel Corporation. */
> +
> +#ifndef XSK_H_
> +#define XSK_H_
> +
> +static inline struct xdp_sock *xdp_sk(struct sock *sk)
> +{
> +	return (struct xdp_sock *)sk;
> +}
> +
> +#endif /* XSK_H_ */
> diff --git a/net/xdp/xsk_diag.c b/net/xdp/xsk_diag.c
> new file mode 100644
> index 000000000000..2585d7a4ac2f
> --- /dev/null
> +++ b/net/xdp/xsk_diag.c
> @@ -0,0 +1,192 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* XDP sockets monitoring support
> + *
> + * Copyright(c) 2019 Intel Corporation.
> + *
> + * Author: Björn Töpel <bjorn.topel@...el.com>
> + */
> +
> +#include <linux/module.h>
> +#include <net/xdp_sock.h>
> +#include <linux/xdp_diag.h>
> +#include <linux/sock_diag.h>
> +
> +#include "xsk_queue.h"
> +#include "xsk.h"
> +
> +static int xsk_diag_put_info(const struct xdp_sock *xs, struct sk_buff *nlskb)
> +{
> +	struct xdp_diag_info di;

Not a bug, but can we generally zero all the structs on stack such that once
we extend them nothing gets potentially leaked.

> +	di.ifindex = xs->dev ? xs->dev->ifindex : 0;
> +	di.queue_id = xs->queue_id;
> +	return nla_put(nlskb, XDP_DIAG_INFO, sizeof(di), &di);
> +}
> +
> +static int xsk_diag_put_ring(const struct xsk_queue *queue, int nl_type,
> +			     struct sk_buff *nlskb)
> +{
> +	struct xdp_diag_ring dr;

Ditto.

> +	dr.entries = queue->nentries;
> +	return nla_put(nlskb, nl_type, sizeof(dr), &dr);
> +}
> +
> +static int xsk_diag_put_rings_cfg(const struct xdp_sock *xs,
> +				  struct sk_buff *nlskb)
> +{
> +	int err = 0;
> +
> +	if (xs->rx)
> +		err = xsk_diag_put_ring(xs->rx, XDP_DIAG_RX_RING, nlskb);
> +	if (!err && xs->tx)
> +		err = xsk_diag_put_ring(xs->tx, XDP_DIAG_TX_RING, nlskb);
> +	return err;
> +}
> +
> +static int xsk_diag_put_umem(const struct xdp_sock *xs, struct sk_buff *nlskb)
> +{
> +	struct xdp_umem *umem = xs->umem;
> +	struct xdp_diag_umem du;

Ditto

> +	int err;
> +
> +	if (!umem)
> +		return 0;
> +
> +	du.id = umem->id;
> +	du.size = umem->size;
> +	du.num_pages = umem->npgs;
> +	du.chunk_size = (__u32)(~umem->chunk_mask + 1);
> +	du.headroom = umem->headroom;
> +	du.ifindex = umem->dev ? umem->dev->ifindex : 0;
> +	du.queue_id = umem->queue_id;
> +	du.flags = 0;
> +	if (umem->zc)
> +		du.flags |= XDP_DU_F_ZEROCOPY;
> +	du.refs = refcount_read(&umem->users);
> +
> +	err = nla_put(nlskb, XDP_DIAG_UMEM, sizeof(du), &du);
> +
> +	if (!err && umem->fq)
> +		err = xsk_diag_put_ring(xs->tx, XDP_DIAG_UMEM_FILL_RING, nlskb);
> +	if (!err && umem->cq) {
> +		err = xsk_diag_put_ring(xs->tx, XDP_DIAG_UMEM_COMPLETION_RING,
> +					nlskb);
> +	}
> +	return err;
> +}
> +
> +static int xsk_diag_fill(struct sock *sk, struct sk_buff *nlskb,
> +			 struct xdp_diag_req *req,
> +			 struct user_namespace *user_ns,
> +			 u32 portid, u32 seq, u32 flags, int sk_ino)
> +{
> +	struct xdp_sock *xs = xdp_sk(sk);
> +	struct xdp_diag_msg *msg;
> +	struct nlmsghdr *nlh;
> +
> +	nlh = nlmsg_put(nlskb, portid, seq, SOCK_DIAG_BY_FAMILY, sizeof(*msg),
> +			flags);
> +	if (!nlh)
> +		return -EMSGSIZE;
> +
> +	msg = nlmsg_data(nlh);
> +	msg->xdiag_family = AF_XDP;
> +	msg->xdiag_type = sk->sk_type;
> +	msg->xdiag_ino = sk_ino;
> +	sock_diag_save_cookie(sk, msg->xdiag_cookie);

Don't we have a hole in struct xdp_diag_msg after xdiag_type? Probably better
to memset everything in the beginning as well.

> +	if ((req->xdiag_show & XDP_SHOW_INFO) && xsk_diag_put_info(xs, nlskb))
> +		goto out_nlmsg_trim;
> +
> +	if ((req->xdiag_show & XDP_SHOW_INFO) &&
> +	    nla_put_u32(nlskb, XDP_DIAG_UID,
> +			from_kuid_munged(user_ns, sock_i_uid(sk))))
> +		goto out_nlmsg_trim;
> +
> +	if ((req->xdiag_show & XDP_SHOW_RING_CFG) &&
> +	    xsk_diag_put_rings_cfg(xs, nlskb))
> +		goto out_nlmsg_trim;
> +
> +	if ((req->xdiag_show & XDP_SHOW_UMEM) &&
> +	    xsk_diag_put_umem(xs, nlskb))
> +		goto out_nlmsg_trim;
> +
> +	if ((req->xdiag_show & XDP_SHOW_MEMINFO) &&
> +	    sock_diag_put_meminfo(sk, nlskb, XDP_DIAG_MEMINFO))
> +		goto out_nlmsg_trim;
> +
> +	nlmsg_end(nlskb, nlh);
> +	return 0;
> +
> +out_nlmsg_trim:
> +	nlmsg_cancel(nlskb, nlh);
> +	return -EMSGSIZE;
> +}
> +
> +static int xsk_diag_dump(struct sk_buff *nlskb, struct netlink_callback *cb)
> +{
> +	struct xdp_diag_req *req = nlmsg_data(cb->nlh);
> +	struct net *net = sock_net(nlskb->sk);
> +	int num = 0, s_num = cb->args[0];
> +	struct sock *sk;
> +
> +	mutex_lock(&net->xdp.lock);
> +
> +	sk_for_each(sk, &net->xdp.list) {
> +		if (!net_eq(sock_net(sk), net))
> +			continue;
> +		if (num++ < s_num)
> +			continue;
> +
> +		if (xsk_diag_fill(sk, nlskb, req,
> +				  sk_user_ns(NETLINK_CB(cb->skb).sk),
> +				  NETLINK_CB(cb->skb).portid,
> +				  cb->nlh->nlmsg_seq, NLM_F_MULTI,
> +				  sock_i_ino(sk)) < 0) {
> +			num--;
> +			break;
> +		}
> +	}
> +
> +	mutex_unlock(&net->xdp.lock);
> +	cb->args[0] = num;
> +	return nlskb->len;
> +}
> +
> +static int xsk_diag_handler_dump(struct sk_buff *nlskb, struct nlmsghdr *hdr)
> +{
> +	struct netlink_dump_control c = { .dump = xsk_diag_dump };
> +	int hdrlen = sizeof(struct xdp_diag_req);
> +	struct net *net = sock_net(nlskb->sk);
> +	struct xdp_diag_req *req;
> +
> +	if (nlmsg_len(hdr) < hdrlen)
> +		return -EINVAL;
> +
> +	if (!(hdr->nlmsg_flags & NLM_F_DUMP))
> +		return -EOPNOTSUPP;
> +
> +	req = nlmsg_data(hdr);
> +	return netlink_dump_start(net->diag_nlsk, nlskb, hdr, &c);
> +}
> +
> +static const struct sock_diag_handler xsk_diag_handler = {
> +	.family = AF_XDP,
> +	.dump = xsk_diag_handler_dump,
> +};
> +
> +static int __init xsk_diag_init(void)
> +{
> +	return sock_diag_register(&xsk_diag_handler);
> +}
> +
> +static void __exit xsk_diag_exit(void)
> +{
> +	sock_diag_unregister(&xsk_diag_handler);
> +}
> +
> +module_init(xsk_diag_init);
> +module_exit(xsk_diag_exit);
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_NETLINK, NETLINK_SOCK_DIAG, AF_XDP);
> 

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