[RFC v2 bpf-next 5/7] libbpf: add API to get XDP/XSK supported features

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Extend bpf_xdp_query routine in order to get XDP/XSK supported features
of netdev over route netlink interface.
Extend libbpf netlink implementation in order to support netlink_generic
protocol.

Co-developed-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Co-developed-by: Marek Majtyka <alardam@xxxxxxxxx>
Signed-off-by: Marek Majtyka <alardam@xxxxxxxxx>
Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
 tools/lib/bpf/libbpf.h  |  3 +-
 tools/lib/bpf/netlink.c | 98 +++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/nlattr.h  | 12 +++++
 3 files changed, 112 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 898db26e42e9..29cb7040fa77 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -982,9 +982,10 @@ struct bpf_xdp_query_opts {
 	__u32 hw_prog_id;	/* output */
 	__u32 skb_prog_id;	/* output */
 	__u8 attach_mode;	/* output */
+	__u64 fflags;		/* output */
 	size_t :0;
 };
-#define bpf_xdp_query_opts__last_field attach_mode
+#define bpf_xdp_query_opts__last_field fflags
 
 LIBBPF_API int bpf_xdp_attach(int ifindex, int prog_fd, __u32 flags,
 			      const struct bpf_xdp_attach_opts *opts);
diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
index d2468a04a6c3..66c7e3dbd41f 100644
--- a/tools/lib/bpf/netlink.c
+++ b/tools/lib/bpf/netlink.c
@@ -9,6 +9,7 @@
 #include <linux/if_ether.h>
 #include <linux/pkt_cls.h>
 #include <linux/rtnetlink.h>
+#include <linux/netdev.h>
 #include <sys/socket.h>
 #include <errno.h>
 #include <time.h>
@@ -39,6 +40,12 @@ struct xdp_id_md {
 	int ifindex;
 	__u32 flags;
 	struct xdp_link_info info;
+	__u64 fflags;
+};
+
+struct xdp_features_md {
+	int ifindex;
+	__u64 flags;
 };
 
 static int libbpf_netlink_open(__u32 *nl_pid, int proto)
@@ -238,6 +245,42 @@ static int libbpf_netlink_send_recv(struct libbpf_nla_req *req,
 	return ret;
 }
 
+static int parse_genl_family_id(struct nlmsghdr *nh, libbpf_dump_nlmsg_t fn,
+				void *cookie)
+{
+	struct nlattr *na = (struct nlattr *)(NLMSG_DATA(nh) + GENL_HDRLEN);
+
+	na = (struct nlattr *)((void *)na + NLA_ALIGN(na->nla_len));
+	if (na->nla_type == CTRL_ATTR_FAMILY_ID) {
+		__u16 *id = cookie;
+
+		*id = libbpf_nla_getattr_u16(na);
+		return NL_DONE;
+	}
+
+	return NL_CONT;
+}
+
+static int libbpf_netlink_resolve_genl_family_id(const char *name,
+						 __u16 len, __u16 *id)
+{
+	struct libbpf_nla_req req = {
+		.nh.nlmsg_len	= NLMSG_LENGTH(GENL_HDRLEN),
+		.nh.nlmsg_type	= GENL_ID_CTRL,
+		.nh.nlmsg_flags	= NLM_F_REQUEST,
+		.gnl.cmd	= CTRL_CMD_GETFAMILY,
+		.gnl.version	= 1,
+	};
+	int err;
+
+	err = nlattr_add(&req, CTRL_ATTR_FAMILY_NAME, name, len);
+	if (err < 0)
+		return err;
+
+	return libbpf_netlink_send_recv(&req, NETLINK_GENERIC,
+					parse_genl_family_id, NULL, id);
+}
+
 static int __bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
 					 __u32 flags)
 {
@@ -357,6 +400,29 @@ static int get_xdp_info(void *cookie, void *msg, struct nlattr **tb)
 	return 0;
 }
 
+static int parse_xdp_features(struct nlmsghdr *nh, libbpf_dump_nlmsg_t fn,
+			      void *cookie)
+{
+	struct nlattr *na = (struct nlattr *)(NLMSG_DATA(nh) + GENL_HDRLEN);
+	struct xdp_features_md *md = cookie;
+	int ifindex;
+
+	if (na->nla_type != NETDEV_A_DEV_IFINDEX)
+		return NL_CONT;
+
+	ifindex = libbpf_nla_getattr_u32(na);
+	if (ifindex != md->ifindex)
+		return NL_CONT;
+
+	na = (struct nlattr *)((void *)na + NLA_ALIGN(na->nla_len));
+	if (na->nla_type != NETDEV_A_DEV_XDP_FEATURES)
+		return NL_CONT;
+
+	md->flags = libbpf_nla_getattr_u64(na);
+
+	return NL_DONE;
+}
+
 int bpf_xdp_query(int ifindex, int xdp_flags, struct bpf_xdp_query_opts *opts)
 {
 	struct libbpf_nla_req req = {
@@ -393,6 +459,38 @@ int bpf_xdp_query(int ifindex, int xdp_flags, struct bpf_xdp_query_opts *opts)
 	OPTS_SET(opts, skb_prog_id, xdp_id.info.skb_prog_id);
 	OPTS_SET(opts, attach_mode, xdp_id.info.attach_mode);
 
+	if (OPTS_HAS(opts, fflags)) {
+		struct xdp_features_md md = {
+			.ifindex = ifindex,
+		};
+		__u16 id;
+
+		err = libbpf_netlink_resolve_genl_family_id("netdev",
+							    sizeof("netdev"),
+							    &id);
+		if (err < 0)
+			return libbpf_err(err);
+
+		memset(&req, 0, sizeof(req));
+		req.nh.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
+		req.nh.nlmsg_flags = NLM_F_REQUEST;
+		req.nh.nlmsg_type = id;
+		req.gnl.cmd = NETDEV_CMD_DEV_GET;
+		req.gnl.version = 1;
+
+		err = nlattr_add(&req, NETDEV_A_DEV_IFINDEX, &ifindex,
+				 sizeof(ifindex));
+		if (err < 0)
+			return err;
+
+		err = libbpf_netlink_send_recv(&req, NETLINK_GENERIC,
+					       parse_xdp_features, NULL, &md);
+		if (err)
+			return libbpf_err(err);
+
+		opts->fflags = md.flags;
+	}
+
 	return 0;
 }
 
diff --git a/tools/lib/bpf/nlattr.h b/tools/lib/bpf/nlattr.h
index 4d15ae2ff812..d92d1c1de700 100644
--- a/tools/lib/bpf/nlattr.h
+++ b/tools/lib/bpf/nlattr.h
@@ -14,6 +14,7 @@
 #include <errno.h>
 #include <linux/netlink.h>
 #include <linux/rtnetlink.h>
+#include <linux/genetlink.h>
 
 /* avoid multiple definition of netlink features */
 #define __LINUX_NETLINK_H
@@ -58,6 +59,7 @@ struct libbpf_nla_req {
 	union {
 		struct ifinfomsg ifinfo;
 		struct tcmsg tc;
+		struct genlmsghdr gnl;
 	};
 	char buf[128];
 };
@@ -89,11 +91,21 @@ static inline uint8_t libbpf_nla_getattr_u8(const struct nlattr *nla)
 	return *(uint8_t *)libbpf_nla_data(nla);
 }
 
+static inline uint16_t libbpf_nla_getattr_u16(const struct nlattr *nla)
+{
+	return *(uint16_t *)libbpf_nla_data(nla);
+}
+
 static inline uint32_t libbpf_nla_getattr_u32(const struct nlattr *nla)
 {
 	return *(uint32_t *)libbpf_nla_data(nla);
 }
 
+static inline uint64_t libbpf_nla_getattr_u64(const struct nlattr *nla)
+{
+	return *(uint64_t *)libbpf_nla_data(nla);
+}
+
 static inline const char *libbpf_nla_getattr_str(const struct nlattr *nla)
 {
 	return (const char *)libbpf_nla_data(nla);
-- 
2.39.0




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