Add support for extended ack error reporting via libmnl. This
is a better alternative to use existing library and not copy/paste
code from the kernel. Also make arguments const where possible.
Add a new function rtnl_talk_extack that takes a callback as an input
arg. If a netlink response contains extack attributes, the callback is
is invoked with the the err string, offset in the message and a pointer
to the message returned by the kernel.
Adding a new function allows commands to be moved over to the
extended error reporting over time.
For feedback, compile tested only.
---
include/libnetlink.h | 6 +++
lib/Makefile | 7 ++++
lib/libnetlink.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++----
3 files changed, 116 insertions(+), 7 deletions(-)
diff --git a/include/libnetlink.h b/include/libnetlink.h
index c43ab0a2d9d9..32d5177cd1ab 100644
--- a/include/libnetlink.h
+++ b/include/libnetlink.h
@@ -66,6 +66,9 @@ typedef int (*rtnl_listen_filter_t)(const struct sockaddr_nl
*,
struct rtnl_ctrl_data *,
struct nlmsghdr *n, void *);
+typedef int (*nl_ext_ack_fn_t)(const char *errmsg, uint32_t off,
+ const struct nlmsghdr *inner_nlh);
+
struct rtnl_dump_filter_arg {
rtnl_filter_t filter;
void *arg1;
@@ -82,6 +85,9 @@ int rtnl_dump_filter_nc(struct rtnl_handle *rth,
int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
struct nlmsghdr *answer, size_t len)
__attribute__((warn_unused_result));
+int rtnl_talk_extack(struct rtnl_handle *rtnl, struct nlmsghdr *n,
+ struct nlmsghdr *answer, size_t len, nl_ext_ack_fn_t errfn)
+ __attribute__((warn_unused_result));
int rtnl_talk_suppress_rtnl_errmsg(struct rtnl_handle *rtnl, struct nlmsghdr
*n,
struct nlmsghdr *answer, size_t len)
__attribute__((warn_unused_result));
diff --git a/lib/Makefile b/lib/Makefile
index 1d24ca24b9a3..f81888cca974 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -4,6 +4,13 @@ ifeq ($(IP_CONFIG_SETNS),y)
CFLAGS += -DHAVE_SETNS
endif
+ifeq ($(HAVE_MNL),y)
+ CFLAGS += $(shell $(PKG_CONFIG) libmnl --cflags)
+ LDLIBS += $(shell $(PKG_CONFIG) libmnl --libs)
+else
+@warn "libmnl required for error support"
+endif
+
CFLAGS += -fPIC
UTILOBJ = utils.o rt_names.o ll_types.o ll_proto.o ll_addr.o \
diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 5b75b2db4e0b..20ec7fe20d7c 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -36,6 +36,79 @@
int rcvbuf = 1024 * 1024;
+#ifdef HAVE_LIBMNL
+#include <libmnl/libmnl.h>
+
+static const enum mnl_attr_data_type extack_policy[NLMSGERR_ATTR_MAX + 1] = {
+ [NLMSGERR_ATTR_MSG] = MNL_TYPE_NUL_STRING,
+ [NLMSGERR_ATTR_OFFS] = MNL_TYPE_U32,
+};
+
+static int err_attr_cb(const struct nlattr *attr, void *data)
+{
+ const struct nlattr **tb = data;
+ uint16_t type;
+
+ if (mnl_attr_type_valid(attr, NLMSGERR_ATTR_MAX) < 0)
+ return MNL_CB_ERROR;
+
+ type = mnl_attr_get_type(attr);
+ if (mnl_attr_validate(attr, extack_policy[type]) < 0)
+ return MNL_CB_ERROR;
+
+
+ tb[type] = attr;
+ return MNL_CB_OK;
+}
+
+
+/* dump netlink extended ack error message */
+static int nl_dump_ext_err(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
+{
+ struct nlattr *tb[NLMSGERR_ATTR_MAX + 1];
+ const struct nlmsgerr *err = mnl_nlmsg_get_payload(nlh);
+ const struct nlmsghdr *err_nlh = NULL;
+ unsigned int hlen = sizeof(*err);
+ const char *errmsg = NULL;
+ uint32_t off = 0;
+
+ if (!errfn)
+ return 0;
+
+ /* no TLVs, nothing to do here */
+ if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
+ return 0;
+
+ /* if NLM_F_CAPPED is set then the inner err msg was capped */
+ if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
+ hlen += mnl_nlmsg_get_payload_len(&err->msg);
+
+ mnl_attr_parse(nlh, hlen, err_attr_cb, tb);
+
+ if (tb[NLMSGERR_ATTR_MSG])
+ errmsg = mnl_attr_get_str(tb[NLMSGERR_ATTR_MSG]);
+
+ if (tb[NLMSGERR_ATTR_OFFS]) {
+ off = mnl_attr_get_u32(tb[NLMSGERR_ATTR_OFFS]);
+
+ if (off > nlh->nlmsg_len) {
+ fprintf(stderr,
+ "Invalid offset for NLMSGERR_ATTR_OFFS\n");
+ off = 0;
+ } else if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
+ err_nlh = &err->msg;
+ }
+
+ return errfn(errmsg, off, err_nlh);
+}
+#else
+/* No extended error ack without libmnl */
+static int nl_dump_ext_err(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
+{
+ return 0;
+}
+#endif
+
void rtnl_close(struct rtnl_handle *rth)
{
if (rth->fd >= 0) {
@@ -49,6 +122,7 @@ int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int
subscriptions,
{
socklen_t addr_len;
int sndbuf = 32768;
+ int one = 1;
memset(rth, 0, sizeof(*rth));
@@ -71,6 +145,11 @@ int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int
subscriptions,
return -1;
}
+ if (setsockopt(rth->fd, SOL_NETLINK, NETLINK_EXT_ACK,
+ &one, sizeof(one)) < 0) {
+ /* debug/verbose message that it is not supported */
+ }
+
memset(&rth->local, 0, sizeof(rth->local));
rth->local.nl_family = AF_NETLINK;
rth->local.nl_groups = subscriptions;
@@ -417,9 +496,19 @@ int rtnl_dump_filter_nc(struct rtnl_handle *rth,
return rtnl_dump_filter_l(rth, a);
}
+static void rtnl_talk_error(struct nlmsghdr *h, struct nlmsgerr *err,
+ nl_ext_ack_fn_t errfn)
+{
+ if (nl_dump_ext_err(h, errfn))
+ return;
+
+ fprintf(stderr, "RTNETLINK answers: %s\n",
+ strerror(-err->error));
+}
+
static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
struct nlmsghdr *answer, size_t maxlen,
- bool show_rtnl_err)
+ bool show_rtnl_err, nl_ext_ack_fn_t errfn)
{
int status;
unsigned int seq;
@@ -506,10 +595,10 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct
nlmsghdr *n,
return 0;
}
- if (rtnl->proto != NETLINK_SOCK_DIAG &&
show_rtnl_err)
- fprintf(stderr,
- "RTNETLINK answers: %s\n",
- strerror(-err->error));
+ if (rtnl->proto != NETLINK_SOCK_DIAG &&
+ show_rtnl_err)
+ rtnl_talk_error(h, err, errfn);
+
errno = -err->error;
return -1;
}
@@ -541,13 +630,20 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct
nlmsghdr *n,
int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
struct nlmsghdr *answer, size_t maxlen)
{
- return __rtnl_talk(rtnl, n, answer, maxlen, true);
+ return __rtnl_talk(rtnl, n, answer, maxlen, true, NULL);
+}
+
+int rtnl_talk_extack(struct rtnl_handle *rtnl, struct nlmsghdr *n,
+ struct nlmsghdr *answer, size_t maxlen,
+ nl_ext_ack_fn_t errfn)
+{
+ return __rtnl_talk(rtnl, n, answer, maxlen, true, errfn);
}
int rtnl_talk_suppress_rtnl_errmsg(struct rtnl_handle *rtnl, struct nlmsghdr
*n,
struct nlmsghdr *answer, size_t maxlen)
{
- return __rtnl_talk(rtnl, n, answer, maxlen, false);
+ return __rtnl_talk(rtnl, n, answer, maxlen, false, NULL);
}
int rtnl_listen_all_nsid(struct rtnl_handle *rth)
--
2.11.0
