libbpf: add error reporting in XDP

Parse netlink ext attribute to get the error message returned by
the card. Code is partially take from libnl.

We add netlink.h to the uapi include of tools. And we need to
avoid include of userspace netlink header to have a successful
build of sample so nlattr.h has a define to avoid
the inclusion. Using a direct define could have been an issue
as NLMSGERR_ATTR_MAX can change in the future.

We also define SOL_NETLINK if not defined to avoid to have to
copy socket.h for a fixed value.

Signed-off-by: Eric Leblond <eric@regit.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 72 insertions, 0 deletions

diff --git a/tools/lib/bpf/nlattr.h b/tools/lib/bpf/nlattr.h
new file mode 100644
index 000000000000..931a71f68f93
--- /dev/null
+++ b/tools/lib/bpf/nlattr.h
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: LGPL-2.1 */
+
+/*
+ * NETLINK      Netlink attributes
+ *
+ *      This library is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU Lesser General Public
+ *      License as published by the Free Software Foundation version 2.1
+ *      of the License.
+ *
+ * Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch>
+ */
+
+#ifndef __NLATTR_H
+#define __NLATTR_H
+
+#include <stdint.h>
+#include <linux/netlink.h>
+/* avoid multiple definition of netlink features */
+#define __LINUX_NETLINK_H
+
+/**
+ * Standard attribute types to specify validation policy
+ */
+enum {
+        NLA_UNSPEC,     /**< Unspecified type, binary data chunk */
+        NLA_U8,         /**< 8 bit integer */
+        NLA_U16,        /**< 16 bit integer */
+        NLA_U32,        /**< 32 bit integer */
+        NLA_U64,        /**< 64 bit integer */
+        NLA_STRING,     /**< NUL terminated character string */
+        NLA_FLAG,       /**< Flag */
+        NLA_MSECS,      /**< Micro seconds (64bit) */
+        NLA_NESTED,     /**< Nested attributes */
+        __NLA_TYPE_MAX,
+};
+
+#define NLA_TYPE_MAX (__NLA_TYPE_MAX - 1)
+
+/**
+ * @ingroup attr
+ * Attribute validation policy.
+ *
+ * See section @core_doc{core_attr_parse,Attribute Parsing} for more details.
+ */
+struct nla_policy {
+        /** Type of attribute or NLA_UNSPEC */
+        uint16_t        type;
+
+        /** Minimal length of payload required */
+        uint16_t        minlen;
+
+        /** Maximal length of payload allowed */
+        uint16_t        maxlen;
+};
+
+/**
+ * @ingroup attr
+ * Iterate over a stream of attributes
+ * @arg pos     loop counter, set to current attribute
+ * @arg head    head of attribute stream
+ * @arg len     length of attribute stream
+ * @arg rem     initialized to len, holds bytes currently remaining in stream
+ */
+#define nla_for_each_attr(pos, head, len, rem) \
+        for (pos = head, rem = len; \
+             nla_ok(pos, rem); \
+             pos = nla_next(pos, &(rem)))
+
+int nla_dump_errormsg(struct nlmsghdr *nlh);
+
+#endif /* __NLATTR_H */