Message-Id: <20210428162553.719588-3-memxor@gmail.com>
Date:   Wed, 28 Apr 2021 21:55:52 +0530
From:   Kumar Kartikeya Dwivedi <memxor@...il.com>
To:     bpf@...r.kernel.org
Cc:     Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Shaun Crampton <shaun@...era.io>, netdev@...r.kernel.org
Subject: [PATCH bpf-next v5 2/3] libbpf: add low level TC-BPF API

This adds functions that wrap the netlink API used for adding,
manipulating, and removing traffic control filters.

An API summary:

A bpf_tc_hook represents a location where a TC-BPF filter can be
attached. This means that creating a hook leads to creation of the
backing qdisc, while destruction either removes all filters attached to
a hook, or destroys qdisc if requested explicitly (as discussed below).

The TC-BPF API functions operate on this bpf_tc_hook to attach, replace,
query, and detach tc filters.

All functions return 0 on success, and a negative error code on failure.

bpf_tc_hook_create - Create a hook
Parameters:
	@hook - Cannot be NULL, ifindex > 0, attach_point must be set to
		proper enum constant. Note that parent must be unset when
		attach_point is one of BPF_TC_INGRESS or BPF_TC_EGRESS. Note
		that as an exception BPF_TC_INGRESS|BPF_TC_EGRESS is also a
		valid value for attach_point.

		Returns -EOPNOTSUPP when hook has attach_point as BPF_TC_CUSTOM.

	@flags - Currently only BPF_TC_F_REPLACE, which creates qdisc in
		 non-exclusive mode (i.e. an existing qdisc will be replaced
		 instead of this function failing with -EEXIST).

bpf_tc_hook_destroy - Destroy the hook
Parameters:
        @hook - Cannot be NULL. The behaviour depends on value of
		attach_point.

		If BPF_TC_INGRESS, all filters attached to the ingress
		hook will be detached.
		If BPF_TC_EGRESS, all filters attached to the egress hook
		will be detached.
		If BPF_TC_INGRESS|BPF_TC_EGRESS, the clsact qdisc will be
		deleted, also detaching all filters.

		It is advised that if the qdisc is operated on by many programs,
		then the program atleast check that there are no other existing
		filters before deleting the clsact qdisc. An example is shown
		below:

		/* set opts as NULL, as we're not really interested in
		 * getting any info for a particular filter, but just
	 	 * detecting its presence.
		 */
		DECLARE_LIBBPF_OPTS(bpf_tc_hook, .ifindex = if_nametoindex("lo"),
				    .attach_point = BPF_TC_INGRESS);
		r = bpf_tc_query(&hook, NULL);
		if (r < 0 && r == -ENOENT) {
			/* no filters */
			hook.attach_point = BPF_TC_INGRESS|BPF_TC_EGREESS;
			return bpf_tc_hook_destroy(&hook);
		} else /* failed or r == 0, the latter means filters do exist */
			return r;

		Note that there is a small race between checking for no
		filters and deleting the qdisc. This is currently unavoidable.

		Returns -EOPNOTSUPP when hook has attach_point as BPF_TC_CUSTOM.

bpf_tc_attach - Attach a filter to a hook
Parameters:
	@hook - Cannot be NULL. Represents the hook the filter will be
		attached to. Requirements for ifindex and attach_point are
		same as described in bpf_tc_hook_create, but BPF_TC_CUSTOM
		is also supported.  In that case, parent must be set to the
		handle where the filter will be attached (using TC_H_MAKE).

		E.g. To set parent to 1:16 like in tc command line,
		     the equivalent would be TC_H_MAKE(1 << 16, 16)

	@opts - Cannot be NULL.

		The following opts are optional:
			handle - The handle of the filter
			priority - The priority of the filter
				   Must be >= 0 and <= UINT16_MAX
		The following opts must be set:
			prog_fd - The fd of the loaded SCHED_CLS prog
		The following opts must be unset:
			prog_id - The ID of the BPF prog

		The following opts will be filled by bpf_tc_attach on a
		successful attach operation if they are unset:
			handle - The handle of the attached filter
			priority - The priority of the attached filter
			prog_id - The ID of the attached SCHED_CLS prog

		This way, the user can know what the auto allocated
		values for optional opts like handle and priority are
		for the newly attached filter, if they were unset.

		Note that some other attributes are set to some default
		values listed below (this holds for all bpf_tc_* APIs):
			protocol - ETH_P_ALL
			mode - direct action
			chain index - 0
			class ID - 0 (this can be set by writing to the
			skb->tc_classid field from the BPF program)

	@flags - Currently only BPF_TC_F_REPLACE, which creates filter
		 in non-exclusive mode (i.e. an existing filter with the
		 same attributes will be replaced instead of this
		 function failing with -EEXIST).

bpf_tc_detach
Parameters:
	@hook: Cannot be NULL. Represents the hook the filter will be
		detached from. Requirements are same as described above
		in bpf_tc_attach.

	@opts:	Cannot be NULL.

		The following opts must be set:
			handle
			priority
		The following opts must be unset:
			prog_fd
			prog_id

bpf_tc_query
Parameters:
	@hook: Cannot be NULL. Represents the hook where the filter
	       lookup will be performed. Requires are same as described
	       above in bpf_tc_attach.

	@opts: Can be NULL.

	       The following opts are optional:
			handle
			priority
			prog_fd
			prog_id

	       However, only one of prog_fd and prog_id must be
	       set. Setting both leads to an error. Setting none is
	       allowed.

	       The following fields will be filled by bpf_tc_query on a
	       successful lookup if they are unset:
			handle
			priority
			prog_id

	       Based on the specified optional parameters, the matching
	       data for the first matching filter is filled in and 0 is
	       returned. When setting prog_fd, the prog_id will be
	       matched against prog_id of the loaded SCHED_CLS prog
	       represented by prog_fd.

	       To uniquely identify a filter, e.g. to detect its presence,
	       it is recommended to set both handle and priority fields.

Some usage examples (using bpf skeleton infrastructure):

BPF program (test_tc_bpf.c):

	#include <linux/bpf.h>
	#include <bpf/bpf_helpers.h>

	SEC("classifier")
	int cls(struct __sk_buff *skb)
	{
		return 0;
	}

Userspace loader:

	DECLARE_LIBBPF_OPTS(bpf_tc_opts, opts, 0);
	struct test_tc_bpf *skel = NULL;
	int fd, r;

	skel = test_tc_bpf__open_and_load();
	if (!skel)
		return -ENOMEM;

	fd = bpf_program__fd(skel->progs.cls);

	DECLARE_LIBBPF_OPTS(bpf_tc_hook, hook, .ifindex =
			    if_nametoindex("lo"), .attach_point =
			    BPF_TC_INGRESS);
	/* Create clsact qdisc */
	r = bpf_tc_hook_create(&hook, 0);
	if (r < 0)
		goto end;

	DECLARE_LIBBPF_OPTS(bpf_tc_opts, opts, .prog_fd = fd);
	r = bpf_tc_attach(&hook, &opts, 0);
	if (r < 0)
		goto end;
	/* Print the auto allocated handle and priority */
	printf("Handle=%"PRIu32", opts.handle);
	printf("Priority=%"PRIu32", opts.priority);

	opts.prog_fd = opts.prog_id = 0;
	bpf_tc_detach(&hook, &opts);
end:
	test_tc_bpf__destroy(skel);

This is equivalent to doing the following using tc command line:
  # tc qdisc add dev lo clsact
  # tc filter add dev lo ingress bpf obj foo.o sec classifier da

Another example replacing a filter (extending prior example):

	/* We can also choose both (or one), let's try replacing an
	 * existing filter.
	 */
	DECLARE_LIBBPF_OPTS(bpf_tc_opts, replace_opts, .handle =
			    opts.handle, .priority = opts.priority,
			    .prog_fd = fd);
	r = bpf_tc_attach(&hook, &replace_opts, 0);
	if (r < 0 && r == -EEXIST) {
		/* Expected, now use BPF_TC_F_REPLACE to replace it */
		return bpf_tc_attach(&hook, &replace_opts, BPF_TC_F_REPLACE);
	} else if (r == 0) {
		/* There must be no existing filter with these
		 * attributes, so cleanup and return an error.
		 */
		replace_opts.prog_fd = replace_opts.prog_id = 0;
		r = bpf_tc_detach(&hook, &replace_opts);
		if (r == 0)
			r = -1;
	}
	return r;

To obtain info of a particular filter:

	/* Find info for filter with handle 1 and priority 50 */
	DECLARE_LIBBPF_OPTS(bpf_tc_opts, info_opts, .handle = 1,
			    .priority = 50);
	r = bpf_tc_query(&hook, &info_opts);
	if (r < 0 && r == -ENOENT)
		printf("Filter not found");
	else if (r == 0)
		printf("Prog ID: %"PRIu32", info_opts.prog_id);
	return r;

We can also match using prog_id to find the same filter:

	DECLARE_LIBBPF_OPTS(bpf_tc_opts, info_opts2, .prog_id =
			    info_opts.prog_id);
	r = bpf_tc_query(&hook, &info_opts2);
	if (r < 0 && r == -ENOENT)
		printf("Filter not found");
	else if (r == 0) {
		/* If we know there's only one filter for this loaded prog,
		 * it is safe to assert that the handle and priority are
		 * as expected.
		 */
		assert(info_opts2.handle == 1);
		assert(info_opts2.priority == 50);
	}
	return r;

Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
---
 tools/lib/bpf/libbpf.h   |  41 ++++
 tools/lib/bpf/libbpf.map |   5 +
 tools/lib/bpf/netlink.c  | 463 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 508 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index bec4e6a6e31d..3de701f46a33 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -775,6 +775,47 @@ LIBBPF_API int bpf_linker__add_file(struct bpf_linker *linker, const char *filen
 LIBBPF_API int bpf_linker__finalize(struct bpf_linker *linker);
 LIBBPF_API void bpf_linker__free(struct bpf_linker *linker);
 
+enum bpf_tc_attach_point {
+	BPF_TC_INGRESS = 1 << 0,
+	BPF_TC_EGRESS  = 1 << 1,
+	BPF_TC_CUSTOM  = 1 << 2,
+};
+
+enum bpf_tc_attach_flags {
+	BPF_TC_F_REPLACE = 1 << 0,
+};
+
+struct bpf_tc_hook {
+	size_t sz;
+	int ifindex;
+	enum bpf_tc_attach_point attach_point;
+	__u32 parent;
+	size_t :0;
+};
+
+#define bpf_tc_hook__last_field parent
+
+struct bpf_tc_opts {
+	size_t sz;
+	int prog_fd;
+	__u32 prog_id;
+	__u32 handle;
+	__u32 priority;
+	size_t :0;
+};
+
+#define bpf_tc_opts__last_field priority
+
+LIBBPF_API int bpf_tc_hook_create(struct bpf_tc_hook *hook, int flags);
+LIBBPF_API int bpf_tc_hook_destroy(struct bpf_tc_hook *hook);
+LIBBPF_API int bpf_tc_attach(const struct bpf_tc_hook *hook,
+			     struct bpf_tc_opts *opts,
+			     int flags);
+LIBBPF_API int bpf_tc_detach(const struct bpf_tc_hook *hook,
+			     const struct bpf_tc_opts *opts);
+LIBBPF_API int bpf_tc_query(const struct bpf_tc_hook *hook,
+			    struct bpf_tc_opts *opts);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b9b29baf1df8..04509c7c144b 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -361,4 +361,9 @@ LIBBPF_0.4.0 {
 		bpf_linker__new;
 		bpf_map__inner_map;
 		bpf_object__set_kversion;
+		bpf_tc_hook_create;
+		bpf_tc_hook_destroy;
+		bpf_tc_attach;
+		bpf_tc_detach;
+		bpf_tc_query;
 } LIBBPF_0.3.0;
diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
index 6daee6640725..88f7b6144c78 100644
--- a/tools/lib/bpf/netlink.c
+++ b/tools/lib/bpf/netlink.c
@@ -4,7 +4,11 @@
 #include <stdlib.h>
 #include <memory.h>
 #include <unistd.h>
+#include <inttypes.h>
+#include <arpa/inet.h>
 #include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/pkt_cls.h>
 #include <linux/rtnetlink.h>
 #include <sys/socket.h>
 #include <errno.h>
@@ -73,6 +77,12 @@ static int libbpf_netlink_open(__u32 *nl_pid)
 	return ret;
 }
 
+enum {
+	BPF_NL_CONT,
+	BPF_NL_NEXT,
+	BPF_NL_DONE,
+};
+
 static int bpf_netlink_recv(int sock, __u32 nl_pid, int seq,
 			    __dump_nlmsg_t _fn, libbpf_dump_nlmsg_t fn,
 			    void *cookie)
@@ -84,6 +94,7 @@ static int bpf_netlink_recv(int sock, __u32 nl_pid, int seq,
 	int len, ret;
 
 	while (multipart) {
+start:
 		multipart = false;
 		len = recv(sock, buf, sizeof(buf), 0);
 		if (len < 0) {
@@ -121,8 +132,18 @@ static int bpf_netlink_recv(int sock, __u32 nl_pid, int seq,
 			}
 			if (_fn) {
 				ret = _fn(nh, fn, cookie);
-				if (ret)
+				if (ret < 0)
+					return ret;
+				switch (ret) {
+				case BPF_NL_CONT:
+					break;
+				case BPF_NL_NEXT:
+					goto start;
+				case BPF_NL_DONE:
+					return 0;
+				default:
 					return ret;
+				}
 			}
 		}
 	}
@@ -357,3 +378,443 @@ static int libbpf_nl_send_recv(struct nlmsghdr *nh, __dump_nlmsg_t fn,
 	close(sock);
 	return ret;
 }
+
+/* TC-HOOK */
+
+typedef int (*qdisc_config_t)(struct nlmsghdr *nh, struct tcmsg *t,
+			      size_t maxsz);
+
+static int clsact_config(struct nlmsghdr *nh, struct tcmsg *t, size_t maxsz)
+{
+	int ret;
+
+	t->tcm_parent = TC_H_CLSACT;
+	t->tcm_handle = TC_H_MAKE(TC_H_CLSACT, 0);
+
+	ret = nlattr_add(nh, maxsz, TCA_KIND, "clsact", sizeof("clsact"));
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int attach_point_to_config(struct bpf_tc_hook *hook, qdisc_config_t *configp)
+{
+	if (!hook)
+		return -EINVAL;
+
+	switch ((int)OPTS_GET(hook, attach_point, 0)) {
+		case BPF_TC_INGRESS:
+		case BPF_TC_EGRESS:
+		case BPF_TC_INGRESS|BPF_TC_EGRESS:
+			if (OPTS_GET(hook, parent, 0))
+				return -EINVAL;
+			*configp = &clsact_config;
+			break;
+		case BPF_TC_CUSTOM:
+			return -EOPNOTSUPP;
+		default:
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static long long int tc_get_tcm_parent(enum bpf_tc_attach_point attach_point,
+				       __u32 parent)
+{
+	long long int ret;
+
+	switch (attach_point) {
+	case BPF_TC_INGRESS:
+		if (parent)
+			return -EINVAL;
+		ret = TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_INGRESS);
+		break;
+	case BPF_TC_EGRESS:
+		if (parent)
+			return -EINVAL;
+		ret = TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS);
+		break;
+	case BPF_TC_CUSTOM:
+		if (!parent)
+			return -EINVAL;
+		ret = parent;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static int tc_qdisc_modify(struct bpf_tc_hook *hook, int cmd, int flags)
+{
+	qdisc_config_t config;
+	int ret = 0;
+	struct {
+		struct nlmsghdr nh;
+		struct tcmsg t;
+		char buf[256];
+	} req;
+
+	ret = attach_point_to_config(hook, &config);
+	if (ret < 0)
+		return ret;
+
+	memset(&req, 0, sizeof(req));
+	req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg));
+	req.nh.nlmsg_flags =
+		NLM_F_REQUEST | NLM_F_ACK | flags;
+	req.nh.nlmsg_type = cmd;
+	req.t.tcm_family = AF_UNSPEC;
+	req.t.tcm_ifindex = OPTS_GET(hook, ifindex, 0);
+
+	ret = config(&req.nh, &req.t, sizeof(req));
+	if (ret < 0)
+		return ret;
+
+	ret = libbpf_nl_send_recv(&req.nh, NULL, NULL, NULL);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int tc_qdisc_create_excl(struct bpf_tc_hook *hook, int flags)
+{
+	flags = flags & BPF_TC_F_REPLACE ? NLM_F_REPLACE : NLM_F_EXCL;
+	return tc_qdisc_modify(hook, RTM_NEWQDISC, NLM_F_CREATE | flags);
+}
+
+static int tc_qdisc_delete(struct bpf_tc_hook *hook)
+{
+	return tc_qdisc_modify(hook, RTM_DELQDISC, 0);
+}
+
+int bpf_tc_hook_create(struct bpf_tc_hook *hook, int flags)
+{
+	if (!hook || !OPTS_VALID(hook, bpf_tc_hook))
+		return -EINVAL;
+	if (OPTS_GET(hook, ifindex, 0) <= 0 || flags & ~BPF_TC_F_REPLACE)
+		return -EINVAL;
+
+	return tc_qdisc_create_excl(hook, flags);
+}
+
+static int tc_cls_detach(const struct bpf_tc_hook *hook,
+			 const struct bpf_tc_opts *opts, bool flush);
+
+int bpf_tc_hook_destroy(struct bpf_tc_hook *hook)
+{
+	if (!hook || !OPTS_VALID(hook, bpf_tc_hook) ||
+	    OPTS_GET(hook, ifindex, 0) <= 0)
+		return -EINVAL;
+
+	switch ((int)OPTS_GET(hook, attach_point, 0)) {
+		case BPF_TC_INGRESS:
+		case BPF_TC_EGRESS:
+			return tc_cls_detach(hook, NULL, true);
+		case BPF_TC_INGRESS|BPF_TC_EGRESS:
+			return tc_qdisc_delete(hook);
+		case BPF_TC_CUSTOM:
+			return -EOPNOTSUPP;
+		default:
+			return -EINVAL;
+	}
+}
+
+struct pass_info {
+	struct bpf_tc_opts *opts;
+	__u32 match_prog_id;
+	bool processed;
+};
+
+/* TC-BPF */
+
+static int tc_cls_add_fd_and_name(struct nlmsghdr *nh, size_t maxsz, int fd)
+{
+	struct bpf_prog_info info = {};
+	char name[256] = {};
+	int len, ret;
+
+	ret = bpf_obj_get_info_by_fd(fd, &info, &(__u32){sizeof(info)});
+	if (ret < 0)
+		return ret;
+
+	ret = nlattr_add(nh, maxsz, TCA_BPF_FD, &fd, sizeof(fd));
+	if (ret < 0)
+		return ret;
+
+	len = snprintf(name, sizeof(name), "%s:[%" PRIu32 "]", info.name,
+		       info.id);
+	if (len < 0 || len >= sizeof(name))
+		return len < 0 ? -EINVAL : -ENAMETOOLONG;
+
+	return nlattr_add(nh, maxsz, TCA_BPF_NAME, name, len + 1);
+}
+
+
+static int cls_get_info(struct nlmsghdr *nh, libbpf_dump_nlmsg_t fn,
+			void *cookie);
+
+int bpf_tc_attach(const struct bpf_tc_hook *hook,
+		  struct bpf_tc_opts *opts, int flags)
+{
+	__u32 protocol = 0, bpf_flags;
+	struct pass_info info = {};
+	long long int tcm_parent;
+	struct nlattr *nla;
+	int ret;
+	struct {
+		struct nlmsghdr nh;
+		struct tcmsg t;
+		char buf[256];
+	} req;
+
+	if (!hook || !opts || !OPTS_VALID(hook, bpf_tc_opts) ||
+	    !OPTS_VALID(opts, bpf_tc_opts))
+		return -EINVAL;
+	if (OPTS_GET(hook, ifindex, 0) <= 0 || !OPTS_GET(opts, prog_fd, 0) ||
+	    OPTS_GET(opts, prog_id, 0))
+		return -EINVAL;
+	if (OPTS_GET(opts, priority, 0) > UINT16_MAX)
+		return -EINVAL;
+	if (flags & ~BPF_TC_F_REPLACE)
+		return -EINVAL;
+
+	protocol = ETH_P_ALL;
+	flags = flags & BPF_TC_F_REPLACE ? NLM_F_REPLACE : NLM_F_EXCL;
+
+	memset(&req, 0, sizeof(req));
+	req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg));
+	req.nh.nlmsg_flags =
+		NLM_F_REQUEST | NLM_F_ACK | NLM_F_CREATE | NLM_F_ECHO | flags;
+	req.nh.nlmsg_type = RTM_NEWTFILTER;
+	req.t.tcm_family = AF_UNSPEC;
+	req.t.tcm_handle = OPTS_GET(opts, handle, 0);
+	req.t.tcm_ifindex = OPTS_GET(hook, ifindex, 0);
+	req.t.tcm_info = TC_H_MAKE(OPTS_GET(opts, priority, 0) << 16, htons(protocol));
+
+	tcm_parent = tc_get_tcm_parent(OPTS_GET(hook, attach_point, 0), OPTS_GET(hook, parent, 0));
+	if (tcm_parent < 0)
+		return tcm_parent;
+	req.t.tcm_parent = tcm_parent;
+
+	ret = nlattr_add(&req.nh, sizeof(req), TCA_KIND, "bpf", sizeof("bpf"));
+	if (ret < 0)
+		return ret;
+
+	nla = nlattr_begin_nested(&req.nh, sizeof(req), TCA_OPTIONS);
+	if (!nla)
+		return -EMSGSIZE;
+
+	ret = tc_cls_add_fd_and_name(&req.nh, sizeof(req), OPTS_GET(opts, prog_fd, 0));
+	if (ret < 0)
+		return ret;
+
+	/* direct action mode is always enabled */
+	bpf_flags = TCA_BPF_FLAG_ACT_DIRECT;
+	ret = nlattr_add(&req.nh, sizeof(req), TCA_BPF_FLAGS,
+			 &bpf_flags, sizeof(bpf_flags));
+	if (ret < 0)
+		return ret;
+
+	nlattr_end_nested(&req.nh, nla);
+
+	info.opts = opts;
+
+	ret = libbpf_nl_send_recv(&req.nh, &cls_get_info, NULL, &info);
+	if (ret < 0)
+		return ret;
+
+	/* Failed to process unicast response */
+	if (!info.processed)
+		ret = -ENOENT;
+
+	return ret;
+}
+
+static int tc_cls_detach(const struct bpf_tc_hook *hook,
+			 const struct bpf_tc_opts *opts, bool flush)
+{
+	long long int tcm_parent;
+	__u32 protocol = 0;
+	int ret, c;
+	struct {
+		struct nlmsghdr nh;
+		struct tcmsg t;
+		char buf[256];
+	} req;
+
+	if (!hook || !OPTS_VALID(hook, bpf_tc_opts) ||
+	    !OPTS_VALID(opts, bpf_tc_opts))
+		return -EINVAL;
+	if (OPTS_GET(hook, ifindex, 0) <= 0 || OPTS_GET(opts, prog_fd, 0) ||
+	    OPTS_GET(opts, prog_id, 0))
+		return -EINVAL;
+	c = !!OPTS_GET(opts, handle, 0) + !!OPTS_GET(opts, priority, 0);
+	if ((flush && c != 0) || (!flush && c != 2))
+		return -EINVAL;
+	if (OPTS_GET(opts, priority, 0) > UINT16_MAX)
+		return -EINVAL;
+
+	if (!flush)
+		protocol = ETH_P_ALL;
+
+	memset(&req, 0, sizeof(req));
+	req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg));
+	req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+	req.nh.nlmsg_type = RTM_DELTFILTER;
+	req.t.tcm_family = AF_UNSPEC;
+	if (!flush)
+		req.t.tcm_handle = OPTS_GET(opts, handle, 0);
+	req.t.tcm_ifindex = OPTS_GET(hook, ifindex, 0);
+	if (!flush)
+		req.t.tcm_info = TC_H_MAKE(OPTS_GET(opts, priority, 0) << 16,
+					   htons(protocol));
+
+	tcm_parent = tc_get_tcm_parent(OPTS_GET(hook, attach_point, 0), OPTS_GET(hook, parent, 0));
+	if (tcm_parent < 0)
+		return tcm_parent;
+	req.t.tcm_parent = tcm_parent;
+
+	if (!flush) {
+		ret = nlattr_add(&req.nh, sizeof(req), TCA_KIND, "bpf", sizeof("bpf"));
+		if (ret < 0)
+			return ret;
+	}
+
+	return libbpf_nl_send_recv(&req.nh, NULL, NULL, NULL);
+}
+
+int bpf_tc_detach(const struct bpf_tc_hook *hook,
+		  const struct bpf_tc_opts *opts)
+{
+	if (!opts)
+		return -EINVAL;
+
+	return tc_cls_detach(hook, opts, false);
+}
+
+static int __cls_get_info(void *cookie, void *msg, struct nlattr **tb,
+			  bool unicast)
+{
+	struct nlattr *tbb[TCA_BPF_MAX + 1];
+	struct pass_info *info = cookie;
+	struct tcmsg *t = msg;
+	__u32 prog_id;
+
+	if (!info)
+		return -EINVAL;
+	if (unicast && info->processed)
+		return -EINVAL;
+	if (!tb[TCA_OPTIONS])
+		return BPF_NL_CONT;
+
+	libbpf_nla_parse_nested(tbb, TCA_BPF_MAX, tb[TCA_OPTIONS], NULL);
+	if (!tbb[TCA_BPF_ID])
+		return -EINVAL;
+
+	if (!info->opts) {
+		/* This is a special case, where user isn't really looking for
+		 * info for the filter, but just wants to detect if there's
+		 * atleast one attached. In that case, terminate processing as a
+		 * short cut.
+		 */
+		if (unicast)
+			return -EINVAL;
+		goto end;
+	}
+
+	prog_id = libbpf_nla_getattr_u32(tbb[TCA_BPF_ID]);
+	if (info->match_prog_id && info->match_prog_id != prog_id)
+		return BPF_NL_CONT;
+
+	OPTS_SET(info->opts, handle, t->tcm_handle);
+	OPTS_SET(info->opts, priority, TC_H_MAJ(t->tcm_info) >> 16);
+	OPTS_SET(info->opts, prog_id, prog_id);
+
+end:
+	info->processed = true;
+	return unicast ? BPF_NL_NEXT : BPF_NL_DONE;
+}
+
+static int cls_get_info(struct nlmsghdr *nh, libbpf_dump_nlmsg_t fn,
+			void *cookie)
+{
+	struct tcmsg *t = NLMSG_DATA(nh);
+	struct nlattr *tb[TCA_MAX + 1];
+
+	libbpf_nla_parse(tb, TCA_MAX,
+			 (struct nlattr *)((char *)t + NLMSG_ALIGN(sizeof(*t))),
+			 NLMSG_PAYLOAD(nh, sizeof(*t)), NULL);
+	if (!tb[TCA_KIND])
+		return -EINVAL;
+
+	return __cls_get_info(cookie, t, tb, nh->nlmsg_flags & NLM_F_ECHO);
+}
+
+int bpf_tc_query(const struct bpf_tc_hook *hook,
+	         struct bpf_tc_opts *opts)
+{
+	struct pass_info pinfo = {};
+	long long int tcm_parent;
+	__u32 protocol;
+	int ret;
+	struct {
+		struct nlmsghdr nh;
+		struct tcmsg t;
+		char buf[256];
+	} req;
+
+	if (!hook || !OPTS_VALID(hook, bpf_tc_hook) ||
+	    !OPTS_VALID(opts, bpf_tc_opts))
+		return -EINVAL;
+	if (OPTS_GET(hook, ifindex, 0) <= 0 || (OPTS_GET(opts, prog_fd, 0) &&
+	    OPTS_GET(opts, prog_id, 0)))
+		return -EINVAL;
+	if (OPTS_GET(opts, priority, 0) > UINT16_MAX)
+		return -EINVAL;
+
+	protocol = ETH_P_ALL;
+
+	memset(&req, 0, sizeof(req));
+	req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg));
+	req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
+	req.nh.nlmsg_type = RTM_GETTFILTER;
+	req.t.tcm_family = AF_UNSPEC;
+	req.t.tcm_handle = OPTS_GET(opts, handle, 0);
+	req.t.tcm_ifindex = OPTS_GET(hook, ifindex, 0);
+	req.t.tcm_info = TC_H_MAKE(OPTS_GET(opts, priority, 0) << 16, htons(protocol));
+
+	tcm_parent = tc_get_tcm_parent(OPTS_GET(hook, attach_point, 0), OPTS_GET(hook, parent, 0));
+	if (tcm_parent < 0)
+		return tcm_parent;
+	req.t.tcm_parent = tcm_parent;
+
+	ret = nlattr_add(&req.nh, sizeof(req), TCA_KIND, "bpf", sizeof("bpf"));
+	if (ret < 0)
+		return ret;
+
+	if (OPTS_GET(opts, prog_fd, 0)) {
+		struct bpf_prog_info info = {};
+		ret = bpf_obj_get_info_by_fd(OPTS_GET(opts, prog_fd, 0), &info, &(__u32){sizeof(info)});
+		if (ret < 0)
+			return ret;
+
+		pinfo.match_prog_id = info.id;
+	} else
+		pinfo.match_prog_id = OPTS_GET(opts, prog_id, 0);
+
+	pinfo.opts = opts;
+
+	ret = libbpf_nl_send_recv(&req.nh, cls_get_info, NULL, &pinfo);
+	if (ret < 0)
+		return ret;
+
+	if (!pinfo.processed)
+		ret = -ENOENT;
+
+	return ret;
+}
-- 
2.30.2

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