monitor: add debug messages

Add some debug messages in the monitor/trace code paths to ease development
and debugging in case of errors.

After this patch, running 'nft monitor --debug=mnl,netlink' is more verbose.

Signed-off-by: Arturo Borrero Gonzalez <arturo@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mnl.c b/src/mnl.c
index da7c0906..cf060a40 100644
--- a/src/mnl.c
+++ b/src/mnl.c
@@ -1139,6 +1139,13 @@ int mnl_nft_event_listener(struct mnl_socket *nf_sock,
 			fprintf(stdout, "# ERROR: %s\n", strerror(errno));
 			break;
 		}
+
+#ifdef DEBUG
+		if (debug_level & DEBUG_MNL) {
+			mnl_nlmsg_fprintf(stdout, buf, sizeof(buf),
+					  sizeof(struct nfgenmsg));
+		}
+#endif /* DEBUG */
 		ret = mnl_cb_run(buf, ret, 0, 0, cb, cb_data);
 		if (ret <= 0)
 			break;