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Subject[PATCH 2/4] libbpf: add error reporting in XDP
Date
Parse netlink ext attribute to get the error message returned by
the card. Code is partially take from libnl.

Signed-off-by: Eric Leblond <eric@regit.org>
---
tools/lib/bpf/Build | 2 +-
tools/lib/bpf/bpf.c | 9 +++
tools/lib/bpf/nlattr.c | 187 +++++++++++++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/nlattr.h | 69 ++++++++++++++++++
4 files changed, 266 insertions(+), 1 deletion(-)
create mode 100644 tools/lib/bpf/nlattr.c
create mode 100644 tools/lib/bpf/nlattr.h

diff --git a/tools/lib/bpf/Build b/tools/lib/bpf/Build
index d8749756352d..64c679d67109 100644
--- a/tools/lib/bpf/Build
+++ b/tools/lib/bpf/Build
@@ -1 +1 @@
-libbpf-y := libbpf.o bpf.o
+libbpf-y := libbpf.o bpf.o nlattr.o
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 1e3cfe6b9fce..cdfabbe118cc 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -26,6 +26,7 @@
#include <linux/bpf.h>
#include "bpf.h"
#include "libbpf.h"
+#include "nlattr.h"
#include <linux/rtnetlink.h>
#include <sys/socket.h>
#include <errno.h>
@@ -436,6 +437,7 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
struct nlmsghdr *nh;
struct nlmsgerr *err;
socklen_t addrlen;
+ int one;

memset(&sa, 0, sizeof(sa));
sa.nl_family = AF_NETLINK;
@@ -445,6 +447,12 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
return -errno;
}

+ if (setsockopt(sock, SOL_NETLINK, NETLINK_EXT_ACK,
+ &one, sizeof(one)) < 0) {
+ /* debug/verbose message that it is not supported */
+ fprintf(stderr, "Netlink error reporting not supported\n");
+ }
+
if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
ret = -errno;
goto cleanup;
@@ -521,6 +529,7 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
if (!err->error)
continue;
ret = err->error;
+ nla_dump_errormsg(nh);
goto cleanup;
case NLMSG_DONE:
break;
diff --git a/tools/lib/bpf/nlattr.c b/tools/lib/bpf/nlattr.c
new file mode 100644
index 000000000000..5cc74fa98049
--- /dev/null
+++ b/tools/lib/bpf/nlattr.c
@@ -0,0 +1,187 @@
+/* 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>
+ */
+
+#include <errno.h>
+#include "nlattr.h"
+#include <linux/rtnetlink.h>
+#include <string.h>
+#include <stdio.h>
+
+static uint16_t nla_attr_minlen[NLA_TYPE_MAX+1] = {
+ [NLA_U8] = sizeof(uint8_t),
+ [NLA_U16] = sizeof(uint16_t),
+ [NLA_U32] = sizeof(uint32_t),
+ [NLA_U64] = sizeof(uint64_t),
+ [NLA_STRING] = 1,
+ [NLA_FLAG] = 0,
+};
+
+static int nla_len(const struct nlattr *nla)
+{
+ return nla->nla_len - NLA_HDRLEN;
+}
+
+static struct nlattr *nla_next(const struct nlattr *nla, int *remaining)
+{
+ int totlen = NLA_ALIGN(nla->nla_len);
+
+ *remaining -= totlen;
+ return (struct nlattr *) ((char *) nla + totlen);
+}
+
+static int nla_ok(const struct nlattr *nla, int remaining)
+{
+ return remaining >= sizeof(*nla) &&
+ nla->nla_len >= sizeof(*nla) &&
+ nla->nla_len <= remaining;
+}
+
+static void *nla_data(const struct nlattr *nla)
+{
+ return (char *) nla + NLA_HDRLEN;
+}
+
+static int nla_type(const struct nlattr *nla)
+{
+ return nla->nla_type & NLA_TYPE_MASK;
+}
+
+static int validate_nla(struct nlattr *nla, int maxtype,
+ struct nla_policy *policy)
+{
+ struct nla_policy *pt;
+ unsigned int minlen = 0;
+ int type = nla_type(nla);
+
+ if (type < 0 || type > maxtype)
+ return 0;
+
+ pt = &policy[type];
+
+ if (pt->type > NLA_TYPE_MAX)
+ return 0;
+
+ if (pt->minlen)
+ minlen = pt->minlen;
+ else if (pt->type != NLA_UNSPEC)
+ minlen = nla_attr_minlen[pt->type];
+
+ if (nla_len(nla) < minlen)
+ return -1;
+
+ if (pt->maxlen && nla_len(nla) > pt->maxlen)
+ return -1;
+
+ if (pt->type == NLA_STRING) {
+ char *data = nla_data(nla);
+ if (data[nla_len(nla) - 1] != '\0')
+ return -1;
+ }
+
+ return 0;
+}
+
+static inline int nlmsg_len(const struct nlmsghdr *nlh)
+{
+ return nlh->nlmsg_len - NLMSG_HDRLEN;
+}
+
+/**
+ * Create attribute index based on a stream of attributes.
+ * @arg tb Index array to be filled (maxtype+1 elements).
+ * @arg maxtype Maximum attribute type expected and accepted.
+ * @arg head Head of attribute stream.
+ * @arg len Length of attribute stream.
+ * @arg policy Attribute validation policy.
+ *
+ * Iterates over the stream of attributes and stores a pointer to each
+ * attribute in the index array using the attribute type as index to
+ * the array. Attribute with a type greater than the maximum type
+ * specified will be silently ignored in order to maintain backwards
+ * compatibility. If \a policy is not NULL, the attribute will be
+ * validated using the specified policy.
+ *
+ * @see nla_validate
+ * @return 0 on success or a negative error code.
+ */
+static int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
+ struct nla_policy *policy)
+{
+ struct nlattr *nla;
+ int rem, err;
+
+ memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
+
+ nla_for_each_attr(nla, head, len, rem) {
+ int type = nla_type(nla);
+
+ if (type > maxtype)
+ continue;
+
+ if (policy) {
+ err = validate_nla(nla, maxtype, policy);
+ if (err < 0)
+ goto errout;
+ }
+
+ if (tb[type])
+ fprintf(stderr, "Attribute of type %#x found multiple times in message, "
+ "previous attribute is being ignored.\n", type);
+
+ tb[type] = nla;
+ }
+
+ err = 0;
+errout:
+ return err;
+}
+
+/* dump netlink extended ack error message */
+int nla_dump_errormsg(struct nlmsghdr *nlh)
+{
+ struct nla_policy extack_policy[NLMSGERR_ATTR_MAX + 1] = {
+ [NLMSGERR_ATTR_MSG] = { .type = NLA_STRING },
+ [NLMSGERR_ATTR_OFFS] = { .type = NLA_U32 },
+ };
+ struct nlattr *tb[NLMSGERR_ATTR_MAX + 1], *attr;
+ struct nlmsgerr *err;
+ char *errmsg = NULL;
+ int hlen, alen;
+
+ /* no TLVs, nothing to do here */
+ if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
+ return 0;
+
+ err = (struct nlmsgerr *)NLMSG_DATA(nlh);
+ hlen = sizeof(*err);
+
+ /* if NLM_F_CAPPED is set then the inner err msg was capped */
+ if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
+ hlen += nlmsg_len(&err->msg);
+
+ attr = (struct nlattr *) ((void *) err + hlen);
+ alen = nlh->nlmsg_len - hlen;
+
+ if (nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen, extack_policy) != 0) {
+ fprintf(stderr,
+ "Failed to parse extended error attributes\n");
+ return 0;
+ }
+
+ if (tb[NLMSGERR_ATTR_MSG])
+ errmsg = (char *) nla_data(tb[NLMSGERR_ATTR_MSG]);
+
+ fprintf(stderr, "Kernel error message: %s\n", errmsg);
+
+ return 0;
+}
diff --git a/tools/lib/bpf/nlattr.h b/tools/lib/bpf/nlattr.h
new file mode 100644
index 000000000000..fa2d015334ef
--- /dev/null
+++ b/tools/lib/bpf/nlattr.h
@@ -0,0 +1,69 @@
+/* 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 <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 */
--
2.15.1
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