iproute: Add support for extended ack to rtnl_talk

Add support for extended ack error reporting via libmnl.
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.

If iproute2 is built without libmnl, it will still work but
extended error reports from kernel will not be available.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/include/libnetlink.h b/include/libnetlink.h
index 643c3bc56929a1c59f49d8711e3325889f531620..69257f0e605154936185b6ea5581751e6099dc90 100644 (file)
--- a/include/libnetlink.h
+++ b/include/libnetlink.h
@@ -76,6 +76,9 @@ 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;
@@ -92,6 +95,9 @@ 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 1d24ca24b9a39fcd5705273f6cf72e482a23796d..f81888cca974f1cd28890d15e51409f5dfe433d1 100644 (file)
--- 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 d4b831f67ea223bb18861bacea03eac2c40e3cee..41353b7dbb3152298b94c6a6968f3a54a1202c0d 100644 (file)
--- 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 +145,10 @@ int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int subscriptions,
                return -1;
        }
 
+       /* Older kernels may no support extended ACK reporting */
+       setsockopt(rth->fd, SOL_NETLINK, NETLINK_EXT_ACK,
+                  &one, sizeof(one));
+
        memset(&rth->local, 0, sizeof(rth->local));
        rth->local.nl_family = AF_NETLINK;
        rth->local.nl_groups = subscriptions;
@@ -423,9 +501,19 @@ 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;
@@ -512,10 +600,10 @@ 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;
                        }
@@ -547,13 +635,20 @@ 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)