[RFC PATCH bpf-next 3/4] libbpf: move xdp program removal to libbpf

[Maciej Fijalkowski <maciejromanfijalkowski@gmail.com>]

Since xsk support in libbpf loads the xdp program interface, make it
also responsible for its removal. Store the prog id in xsk_socket_config
so when removing the program we are still able to compare the current
program id with the id from the attachment time and make a decision
onward.

While at it, remove the socket/umem in xdpsock's error path.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
 samples/bpf/xdpsock_user.c | 33 ++++++++++-----------------------
 tools/lib/bpf/xsk.c        | 32 ++++++++++++++++++++++++++++++++
 tools/lib/bpf/xsk.h        |  1 +
 3 files changed, 43 insertions(+), 23 deletions(-)

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index e9dceb09b6d1..123862b16dd4 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -68,7 +68,6 @@ static int opt_queue;
 static int opt_poll;
 static int opt_interval = 1;
 static u32 opt_xdp_bind_flags;
-static __u32 prog_id;
 
 struct xsk_umem_info {
 	struct xsk_ring_prod fq;
@@ -170,22 +169,6 @@ static void *poller(void *arg)
 	return NULL;
 }
 
-static void remove_xdp_program(void)
-{
-	__u32 curr_prog_id = 0;
-
-	if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
-		printf("bpf_get_link_xdp_id failed\n");
-		exit(EXIT_FAILURE);
-	}
-	if (prog_id == curr_prog_id)
-		bpf_set_link_xdp_fd(opt_ifindex, -1, opt_xdp_flags);
-	else if (!curr_prog_id)
-		printf("couldn't find a prog id on a given interface\n");
-	else
-		printf("program on interface changed, not removing\n");
-}
-
 static void int_exit(int sig)
 {
 	struct xsk_umem *umem = xsks[0]->umem->umem;
@@ -195,7 +178,6 @@ static void int_exit(int sig)
 	dump_stats();
 	xsk_socket__delete(xsks[0]->xsk);
 	(void)xsk_umem__delete(umem);
-	remove_xdp_program();
 
 	exit(EXIT_SUCCESS);
 }
@@ -206,7 +188,16 @@ static void __exit_with_error(int error, const char *file, const char *func,
 	fprintf(stderr, "%s:%s:%i: errno: %d/\"%s\"\n", file, func,
 		line, error, strerror(error));
 	dump_stats();
-	remove_xdp_program();
+
+	if (xsks[0]->xsk)
+		xsk_socket__delete(xsks[0]->xsk);
+
+	if (xsks[0]->umem) {
+		struct xsk_umem *umem = xsks[0]->umem->umem;
+
+		(void)xsk_umem__delete(umem);
+	}
+
 	exit(EXIT_FAILURE);
 }
 
@@ -312,10 +303,6 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
 	if (ret)
 		exit_with_error(-ret);
 
-	ret = bpf_get_link_xdp_id(opt_ifindex, &prog_id, opt_xdp_flags);
-	if (ret)
-		exit_with_error(-ret);
-
 	return xsk;
 }
 
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 514ab3fb06f4..e28bedb0b078 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -259,6 +259,8 @@ int xsk_umem__create(struct xsk_umem **umem_ptr, void *umem_area, __u64 size,
 static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 {
 	static const int log_buf_size = 16 * 1024;
+	struct bpf_prog_info info = {};
+	__u32 info_len = sizeof(info);
 	char log_buf[log_buf_size];
 	int err, prog_fd;
 
@@ -321,6 +323,14 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 		return err;
 	}
 
+	err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
+	if (err) {
+		pr_warning("can't get prog info - %s\n", strerror(errno));
+		close(prog_fd);
+		return err;
+	}
+	xsk->config.prog_id = info.id;
+
 	xsk->prog_fd = prog_fd;
 	return 0;
 }
@@ -483,6 +493,25 @@ static int xsk_set_bpf_maps(struct xsk_socket *xsk)
 	return err;
 }
 
+static void xsk_remove_xdp_prog(struct xsk_socket *xsk)
+{
+	__u32 prog_id = xsk->config.prog_id;
+	__u32 curr_prog_id = 0;
+	int err;
+
+	err = bpf_get_link_xdp_id(xsk->ifindex, &curr_prog_id,
+				  xsk->config.xdp_flags);
+	if (err)
+		return;
+
+	if (prog_id == curr_prog_id)
+		bpf_set_link_xdp_fd(xsk->ifindex, -1, xsk->config.xdp_flags);
+	else if (!curr_prog_id)
+		pr_warning("couldn't find a prog id on a given interface\n");
+	else
+		pr_warning("program on interface changed, not removing\n");
+}
+
 static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
 {
 	__u32 prog_id = 0;
@@ -506,6 +535,7 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
 		err = xsk_lookup_bpf_maps(xsk);
 		if (err)
 			goto out_load;
+		xsk->config.prog_id = prog_id;
 	}
 
 	err = xsk_set_bpf_maps(xsk);
@@ -744,6 +774,8 @@ void xsk_socket__delete(struct xsk_socket *xsk)
 
 	}
 
+	xsk_remove_xdp_prog(xsk);
+
 	xsk->umem->refcount--;
 	/* Do not close an fd that also has an associated umem connected
 	 * to it.
diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
index 82ea71a0f3ec..e1b23e9432c9 100644
--- a/tools/lib/bpf/xsk.h
+++ b/tools/lib/bpf/xsk.h
@@ -186,6 +186,7 @@ struct xsk_socket_config {
 	__u32 tx_size;
 	__u32 libbpf_flags;
 	__u32 xdp_flags;
+	__u32 prog_id;
 	__u16 bind_flags;
 };
 
-- 
2.16.1