Re: [PATCH bpf-next v4 2/3] libbpf: add error reporting in XDP

[Philippe Ombredanne]

On Sat, Dec 30, 2017 at 9:41 PM, Eric Leblond  wrote:
> Parse netlink ext attribute to get the error message returned by
> the card. Code is partially take from libnl.
>
> Signed-off-by: Eric Leblond 
> Acked-by: Alexei Starovoitov 



> --- /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 
> + */

Do you think you could get an ack or signoff from the author
(i.e.Thomas Graf)  to get a more streamlined thing such as this:

> +// SPDX-License-Identifier: LGPL-2.1
> +// NETLINK  Netlink attributes
> +// Copyright (c) 2003-2013 Thomas Graf 


-- 
Cordially
Philippe Ombredanne

[PATCH bpf-next v4 2/3] libbpf: add error reporting in XDP

[Eric Leblond]

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

Signed-off-by: Eric Leblond 
Acked-by: Alexei Starovoitov 
---
 tools/lib/bpf/Build|   2 +-
 tools/lib/bpf/bpf.c|  10 ++-
 tools/lib/bpf/nlattr.c | 187 +
 tools/lib/bpf/nlattr.h |  69 ++
 4 files changed, 266 insertions(+), 2 deletions(-)
 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 f00fba2edeae..ceb20c5cae3b 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -26,6 +26,7 @@
 #include 
 #include "bpf.h"
 #include "libbpf.h"
+#include "nlattr.h"
 #include 
 #include 
 #include 
@@ -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(, 0, sizeof(sa));
sa.nl_family = AF_NETLINK;
@@ -445,6 +447,11 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
return -errno;
}
 
+   if (setsockopt(sock, SOL_NETLINK, NETLINK_EXT_ACK,
+  , sizeof(one)) < 0) {
+   fprintf(stderr, "Netlink error reporting not supported\n");
+   }
+
if (bind(sock, (struct sockaddr *), sizeof(sa)) < 0) {
ret = -errno;
goto cleanup;
@@ -520,7 +527,8 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
err = (struct nlmsgerr *)NLMSG_DATA(nh);
if (!err->error)
continue;
-   ret = err->error;
+   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 ..4719434278b2
--- /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 
+ */
+
+#include 
+#include "nlattr.h"
+#include 
+#include 
+#include 
+
+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 = [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 maxtypeMaximum attribute type