[iproute2-next] tipc: add support for the netlink extack

[Hoang Le]

Add support extack in tipc to dump the netlink extack error messages
(i.e -EINVAL) sent from kernel.

Acked-by: Jon Maloy <jma...@redhat.com>
Signed-off-by: Hoang Le <hoang.h...@dektech.com.au>
---
 tipc/msg.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/tipc/msg.c b/tipc/msg.c
index dc09d05048f3..f29b2f8d35ad 100644
--- a/tipc/msg.c
+++ b/tipc/msg.c
@@ -18,6 +18,7 @@
 #include <linux/genetlink.h>
 #include <libmnl/libmnl.h>
 
+#include "libnetlink.h"
 #include "msg.h"
 
 int parse_attrs(const struct nlattr *attr, void *data)
@@ -49,6 +50,7 @@ static struct mnl_socket *msg_send(struct nlmsghdr *nlh)
 {
        int ret;
        struct mnl_socket *nl;
+       int one = 1;
 
        nl = mnl_socket_open(NETLINK_GENERIC);
        if (nl == NULL) {
@@ -56,6 +58,8 @@ static struct mnl_socket *msg_send(struct nlmsghdr *nlh)
                return NULL;
        }
 
+       /* support to get extended ACK */
+       mnl_socket_setsockopt(nl, NETLINK_EXT_ACK, &one, sizeof(one));
        ret = mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID);
        if (ret < 0) {
                perror("mnl_socket_bind");
@@ -73,21 +77,32 @@ static struct mnl_socket *msg_send(struct nlmsghdr *nlh)
 
 static int msg_recv(struct mnl_socket *nl, mnl_cb_t callback, void *data, int 
seq)
 {
-       int ret;
        unsigned int portid;
        char buf[MNL_SOCKET_BUFFER_SIZE];
+       struct nlmsghdr *h;
+       size_t num_bytes;
+       int is_err = 0;
+       int ret = 0;
 
        portid = mnl_socket_get_portid(nl);
 
-       ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
-       while (ret > 0) {
-               ret = mnl_cb_run(buf, ret, seq, portid, callback, data);
+       num_bytes = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+       while (num_bytes > 0) {
+               ret = mnl_cb_run(buf, num_bytes, seq, portid, callback, data);
                if (ret <= 0)
                        break;
-               ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+               num_bytes = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+       }
+
+       if (ret == -1) {
+               if (num_bytes > 0) {
+                       h = (struct nlmsghdr *)buf;
+                       is_err = nl_dump_ext_ack(h, NULL);
+               }
+
+               if (!is_err)
+                       perror("error");
        }
-       if (ret == -1)
-               perror("error");
 
        mnl_socket_close(nl);
 
-- 
2.25.1