diff mbox series

[bpf-next,v4,6/7] libbpf: Add a support for getting xdp prog id on ifindex

Message ID 20190128191613.11705-7-maciejromanfijalkowski@gmail.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series xdp: Avoid unloading xdp prog not attached by sample | expand

Commit Message

Maciej Fijalkowski Jan. 28, 2019, 7:16 p.m. UTC 
From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

Since we have a dedicated netlink attributes for xdp setup on a
particular interface, it is now possible to retrieve the program id that
is currently attached to the interface. The use case is targeted for
sample xdp programs, which will store the program id just after loading
bpf program onto iface. On shutdown, the sample will make sure that it
can unload the program by querying again the iface and verifying that
both program id's matches.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
---
 tools/lib/bpf/libbpf.h   |  1 +
 tools/lib/bpf/libbpf.map |  1 +
 tools/lib/bpf/netlink.c  | 84 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 86 insertions(+)

Comments

John Fastabend Jan. 28, 2019, 9:07 p.m. UTC | #1 
On 1/28/19 11:16 AM, Maciej Fijalkowski wrote:
> From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> 
> Since we have a dedicated netlink attributes for xdp setup on a
> particular interface, it is now possible to retrieve the program id that
> is currently attached to the interface. The use case is targeted for
> sample xdp programs, which will store the program id just after loading
> bpf program onto iface. On shutdown, the sample will make sure that it
> can unload the program by querying again the iface and verifying that
> both program id's matches.
> 
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> ---

small nit.

> +
> +int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
> +{
> +	struct xdp_id_md xdp_id = {};
> +	int sock, ret;
> +	__u32 nl_pid;
> +	__u32 mask;
> +
> +	if (flags & ~XDP_FLAGS_MASK)
> +		return -EINVAL;
> +
> +	/* Check whether the single {HW,DRV,SKB} mode is set */
> +	flags &= XDP_FLAGS_MODES;
> +	mask = flags - 1;
> +	if (flags && flags & mask)
> +		return -EINVAL;
> +
> +	sock = libbpf_netlink_open(&nl_pid);
> +	if (sock < 0)
> +		return sock;
> +
> +	xdp_id.ifindex = ifindex;
> +	xdp_id.flags = flags;
> +
> +	ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_id, &xdp_id);
> +	*prog_id = xdp_id.id;

just a nit but should we really set prog_id from user if there is
an error. Probably friendlier not to set caller data in error
case.

> +
> +	close(sock);
> +	return ret;
> +}
> +
>  int libbpf_nl_get_link(int sock, unsigned int nl_pid,
>  		       libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
>  {
>
Maciej Fijalkowski Jan. 30, 2019, 5:53 p.m. UTC | #2 
On Mon, 28 Jan 2019 13:07:49 -0800
John Fastabend <john.fastabend@gmail.com> wrote:

> On 1/28/19 11:16 AM, Maciej Fijalkowski wrote:
> > From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> > 
> > Since we have a dedicated netlink attributes for xdp setup on a
> > particular interface, it is now possible to retrieve the program id that
> > is currently attached to the interface. The use case is targeted for
> > sample xdp programs, which will store the program id just after loading
> > bpf program onto iface. On shutdown, the sample will make sure that it
> > can unload the program by querying again the iface and verifying that
> > both program id's matches.
> > 
> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> > Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> > ---  
> 
> small nit.
> 
> > +
> > +int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
> > +{
> > +	struct xdp_id_md xdp_id = {};
> > +	int sock, ret;
> > +	__u32 nl_pid;
> > +	__u32 mask;
> > +
> > +	if (flags & ~XDP_FLAGS_MASK)
> > +		return -EINVAL;
> > +
> > +	/* Check whether the single {HW,DRV,SKB} mode is set */
> > +	flags &= XDP_FLAGS_MODES;
> > +	mask = flags - 1;
> > +	if (flags && flags & mask)
> > +		return -EINVAL;
> > +
> > +	sock = libbpf_netlink_open(&nl_pid);
> > +	if (sock < 0)
> > +		return sock;
> > +
> > +	xdp_id.ifindex = ifindex;
> > +	xdp_id.flags = flags;
> > +
> > +	ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_id, &xdp_id);
> > +	*prog_id = xdp_id.id;  
> 
> just a nit but should we really set prog_id from user if there is
> an error. Probably friendlier not to set caller data in error
> case.
>
Agree, besides checking the return value from libbpf_nl_get_link() we should
also check that we have assigned a value to xdp_id.id so that would mean we
have gone through whole get_xdp_id(). I'll post a v5 within several hours with
following check:

if (!ret && xdp_id.id)
	*prog_id = xdp_id;

Hope that makes sense.
> > +
> > +	close(sock);
> > +	return ret;
> > +}
> > +
> >  int libbpf_nl_get_link(int sock, unsigned int nl_pid,
> >  		       libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
> >  {
> >   
>
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 931be6f3408c..43c77e98df6f 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -317,6 +317,7 @@  LIBBPF_API int bpf_prog_load(const char *file, enum bpf_prog_type type,
 			     struct bpf_object **pobj, int *prog_fd);
 
 LIBBPF_API int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags);
+LIBBPF_API int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags);
 
 enum bpf_perf_event_ret {
 	LIBBPF_PERF_EVENT_DONE	= 0,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b183c6c3b990..d0e023a75d72 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -131,4 +131,5 @@  LIBBPF_0.0.2 {
 		bpf_probe_map_type;
 		bpf_probe_prog_type;
 		bpf_object__find_map_fd_by_name;
+		bpf_get_link_xdp_id;
 } LIBBPF_0.0.1;
diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
index 0ce67aea8f3b..e44a6ef25678 100644
--- a/tools/lib/bpf/netlink.c
+++ b/tools/lib/bpf/netlink.c
@@ -21,6 +21,12 @@ 
 typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, libbpf_dump_nlmsg_t,
 			      void *cookie);
 
+struct xdp_id_md {
+	int ifindex;
+	__u32 flags;
+	__u32 id;
+};
+
 int libbpf_netlink_open(__u32 *nl_pid)
 {
 	struct sockaddr_nl sa;
@@ -196,6 +202,84 @@  static int __dump_link_nlmsg(struct nlmsghdr *nlh,
 	return dump_link_nlmsg(cookie, ifi, tb);
 }
 
+static unsigned char get_xdp_id_attr(unsigned char mode, __u32 flags)
+{
+	if (mode != XDP_ATTACHED_MULTI)
+		return IFLA_XDP_PROG_ID;
+	if (flags & XDP_FLAGS_DRV_MODE)
+		return IFLA_XDP_DRV_PROG_ID;
+	if (flags & XDP_FLAGS_HW_MODE)
+		return IFLA_XDP_HW_PROG_ID;
+	if (flags & XDP_FLAGS_SKB_MODE)
+		return IFLA_XDP_SKB_PROG_ID;
+
+	return IFLA_XDP_UNSPEC;
+}
+
+static int get_xdp_id(void *cookie, void *msg, struct nlattr **tb)
+{
+	struct nlattr *xdp_tb[IFLA_XDP_MAX + 1];
+	struct xdp_id_md *xdp_id = cookie;
+	struct ifinfomsg *ifinfo = msg;
+	unsigned char mode, xdp_attr;
+	int ret;
+
+	if (xdp_id->ifindex && xdp_id->ifindex != ifinfo->ifi_index)
+		return 0;
+
+	if (!tb[IFLA_XDP])
+		return 0;
+
+	ret = libbpf_nla_parse_nested(xdp_tb, IFLA_XDP_MAX, tb[IFLA_XDP], NULL);
+	if (ret)
+		return ret;
+
+	if (!xdp_tb[IFLA_XDP_ATTACHED])
+		return 0;
+
+	mode = libbpf_nla_getattr_u8(xdp_tb[IFLA_XDP_ATTACHED]);
+	if (mode == XDP_ATTACHED_NONE)
+		return 0;
+
+	xdp_attr = get_xdp_id_attr(mode, xdp_id->flags);
+	if (!xdp_attr || !xdp_tb[xdp_attr])
+		return -ENOENT;
+
+	xdp_id->id = libbpf_nla_getattr_u32(xdp_tb[xdp_attr]);
+
+	return 0;
+}
+
+int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
+{
+	struct xdp_id_md xdp_id = {};
+	int sock, ret;
+	__u32 nl_pid;
+	__u32 mask;
+
+	if (flags & ~XDP_FLAGS_MASK)
+		return -EINVAL;
+
+	/* Check whether the single {HW,DRV,SKB} mode is set */
+	flags &= XDP_FLAGS_MODES;
+	mask = flags - 1;
+	if (flags && flags & mask)
+		return -EINVAL;
+
+	sock = libbpf_netlink_open(&nl_pid);
+	if (sock < 0)
+		return sock;
+
+	xdp_id.ifindex = ifindex;
+	xdp_id.flags = flags;
+
+	ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_id, &xdp_id);
+	*prog_id = xdp_id.id;
+
+	close(sock);
+	return ret;
+}
+
 int libbpf_nl_get_link(int sock, unsigned int nl_pid,
 		       libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
 {