[B.A.T.M.A.N.] [PATCH 38/38] batctl: Add command to monitor for netlink events

[Sven Eckelmann <sven@narfation.org>]

The netlink multicast groups of batman-adv are currently used to inform
userspace about finished throughputmeter runs. It will later also be used
to inform about changes of settings of a specific batadv interface.

The "event" will wait for these messages and print brief summaries about
the received data. This can be used during the development of new features
or to monitor running systems.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 Makefile     |   1 +
 event.c      | 246 +++++++++++++++++++++++++++++++++++++++++++++++++++
 man/batctl.8 |   4 +
 3 files changed, 251 insertions(+)
 create mode 100644 event.c

diff --git a/Makefile b/Makefile
index a6971d8..cf2b1c7 100755
--- a/Makefile
+++ b/Makefile
@@ -43,6 +43,7 @@ OBJ += dat_cache.o
 OBJ += debugfs.o
 OBJ += debug.o
 OBJ += distributed_arp_table.o
+OBJ += event.o
 OBJ += fragmentation.o
 OBJ += functions.o
 OBJ += gateways.o
diff --git a/event.c b/event.c
new file mode 100644
index 0000000..73c5a68
--- /dev/null
+++ b/event.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2009-2018  B.A.T.M.A.N. contributors:
+ *
+ * Marek Lindner <mareklindner@neomailbox.ch>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA
+ *
+ * License-Filename: LICENSES/preferred/GPL-2.0
+ */
+
+#include <errno.h>
+#include <getopt.h>
+#include <netlink/netlink.h>
+#include <netlink/genl/genl.h>
+#include <netlink/genl/ctrl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <sys/time.h>
+
+#include "batadv_packet.h"
+#include "batman_adv.h"
+#include "bat-hosts.h"
+#include "debug.h"
+#include "functions.h"
+#include "genl.h"
+#include "main.h"
+#include "netlink.h"
+
+enum event_time_mode {
+	EVENT_TIME_NO,
+	EVENT_TIME_LOCAL,
+	EVENT_TIME_RELATIVE,
+};
+
+struct event_args {
+	enum event_time_mode mode;
+	struct timeval tv;
+};
+
+static void event_usage(void)
+{
+	fprintf(stderr, "Usage: batctl [options] event [parameters]\n");
+	fprintf(stderr, "parameters:\n");
+	fprintf(stderr, " \t -h print this help\n");
+	fprintf(stderr, " \t -t print local timestamp\n");
+	fprintf(stderr, " \t -r print relative timestamp\n");
+}
+
+static int event_prepare(struct state *state)
+{
+	int ret;
+	int mcid;
+
+	if (!state->sock)
+		return -EOPNOTSUPP;
+
+	mcid = nl_get_multicast_id(state->sock, BATADV_NL_NAME,
+				   BATADV_NL_MCAST_GROUP_TPMETER);
+	if (mcid < 0) {
+		fprintf(stderr, "Failed to resolve batadv tp_meter multicast group: %d\n",
+			mcid);
+		/* ignore error for now */
+		goto skip_tp_meter;
+	}
+
+	ret = nl_socket_add_membership(state->sock, mcid);
+	if (ret) {
+		fprintf(stderr, "Failed to join batadv tp_meter multicast group: %d\n",
+			ret);
+		/* ignore error for now */
+		goto skip_tp_meter;
+	}
+
+skip_tp_meter:
+
+	return 0;
+}
+
+static int no_seq_check(struct nl_msg *msg __maybe_unused,
+			void *arg __maybe_unused)
+{
+	return NL_OK;
+}
+
+static const int tp_meter_mandatory[] = {
+	BATADV_ATTR_TPMETER_COOKIE,
+	BATADV_ATTR_TPMETER_RESULT,
+};
+
+static void event_parse_tp_meter(struct nlattr **attrs)
+{
+	const char *result_str;
+	uint32_t cookie;
+	uint8_t result;
+
+	/* ignore entry when attributes are missing */
+	if (missing_mandatory_attrs(attrs, tp_meter_mandatory,
+				    ARRAY_SIZE(tp_meter_mandatory)))
+		return;
+
+	cookie = nla_get_u32(attrs[BATADV_ATTR_TPMETER_COOKIE]);
+	result = nla_get_u8(attrs[BATADV_ATTR_TPMETER_RESULT]);
+
+	switch (result) {
+	case BATADV_TP_REASON_DST_UNREACHABLE:
+		result_str = "Destination unreachable";
+		break;
+	case BATADV_TP_REASON_RESEND_LIMIT:
+		result_str = "The number of retry for the same window exceeds the limit, test aborted";
+		break;
+	case BATADV_TP_REASON_ALREADY_ONGOING:
+		result_str = "Cannot run two test towards the same node";
+		break;
+	case BATADV_TP_REASON_MEMORY_ERROR:
+		result_str = "Kernel cannot allocate memory, aborted";
+		break;
+	case BATADV_TP_REASON_TOO_MANY:
+		result_str = "Too many ongoing sessions";
+		break;
+	case BATADV_TP_REASON_CANCEL:
+		result_str = "CANCEL received: test aborted";
+		break;
+	case BATADV_TP_REASON_COMPLETE:
+		result_str = "complete";
+		break;
+	default:
+		result_str = "unknown";
+		break;
+	}
+
+	printf("tp_meter 0x%08x: %s\n", cookie, result_str);
+}
+
+static unsigned long long get_timestamp(struct event_args *event_args)
+{
+	unsigned long long prevtime = 0;
+	unsigned long long now;
+	struct timeval tv;
+
+	gettimeofday(&tv, NULL);
+	now = 1000000ULL * tv.tv_sec + tv.tv_usec;
+
+	if (event_args->mode == EVENT_TIME_RELATIVE) {
+		prevtime = 1000000ULL * event_args->tv.tv_sec + event_args->tv.tv_usec;
+		event_args->tv = tv;
+	}
+
+	return now - prevtime;
+}
+
+static int event_parse(struct nl_msg *msg, void *arg)
+{
+	struct nlmsghdr *nlh = nlmsg_hdr(msg);
+	struct nlattr *attrs[NUM_BATADV_ATTR];
+	struct event_args *event_args = arg;
+	unsigned long long timestamp;
+	struct genlmsghdr *ghdr;
+
+	if (!genlmsg_valid_hdr(nlh, 0))
+		return NL_OK;
+
+	ghdr = nlmsg_data(nlh);
+
+	if (nla_parse(attrs, BATADV_ATTR_MAX, genlmsg_attrdata(ghdr, 0),
+		      genlmsg_len(ghdr), batadv_netlink_policy)) {
+		fputs("Received invalid data from kernel.\n", stderr);
+		return NL_OK;
+	}
+
+	if (event_args->mode != EVENT_TIME_NO) {
+		timestamp = get_timestamp(event_args);
+		printf("%llu.%06llu: ", timestamp / 1000000, timestamp % 1000000);
+	}
+
+	switch (ghdr->cmd) {
+	case BATADV_CMD_TP_METER:
+		event_parse_tp_meter(attrs);
+		break;
+	default:
+		printf("Received unknown event %u\n", ghdr->cmd);
+		break;
+	}
+
+	return NL_OK;
+}
+
+static int event(struct state *state, int argc __maybe_unused,
+		 char **argv __maybe_unused)
+{
+	struct event_args event_args = {
+		.mode = EVENT_TIME_NO,
+	};
+	int opt;
+	int ret;
+
+	while ((opt = getopt(argc, argv, "htr")) != -1) {
+		switch (opt) {
+		case 'h':
+			event_usage();
+			return EXIT_SUCCESS;
+		case 't':
+			event_args.mode = EVENT_TIME_LOCAL;
+			break;
+		case 'r':
+			event_args.mode = EVENT_TIME_RELATIVE;
+			break;
+		default:
+			event_usage();
+			return  EXIT_FAILURE;
+		}
+	}
+
+	ret = event_prepare(state);
+	if (ret < 0) {
+		fprintf(stderr, "Failed to prepare event netlink: %s (%d)\n",
+			strerror(-ret), -ret);
+		return 1;
+	}
+
+	if (event_args.mode == EVENT_TIME_RELATIVE)
+		get_timestamp(&event_args);
+
+	nl_cb_set(state->cb, NL_CB_SEQ_CHECK, NL_CB_CUSTOM, no_seq_check, NULL);
+	nl_cb_set(state->cb, NL_CB_VALID, NL_CB_CUSTOM, event_parse, &event_args);
+
+	while (1)
+		nl_recvmsgs(state->sock, state->cb);
+
+	return 0;
+}
+
+COMMAND(SUBCOMMAND, event, "e", COMMAND_FLAG_NETLINK, NULL,
+	"                  \tdisplay events from batman-adv");
diff --git a/man/batctl.8 b/man/batctl.8
index d5fc530..fe6cf93 100644
--- a/man/batctl.8
+++ b/man/batctl.8
@@ -89,6 +89,10 @@ OGM packet aggregation.
 If no parameter is given the current bonding mode setting is displayed. Otherwise the parameter is used to enable or disable
 the bonding mode.
 .br
+.IP "\fBevent\fP|\fBe\fP [\fB\-t\fP|\fB\-r\fP]"
+batctl will monitor for events from the netlink kernel interface of batman-adv. The local timestamp of the event will be printed
+when parameter \fB\-t\fP is specified. Parameter \fB\-r\fP will do the same but with relative timestamps.
+.br
 .IP "\fBfragmentation\fP|\fBf\fP [\fB0\fP|\fB1\fP]"
 If no parameter is given the current fragmentation mode setting is displayed. Otherwise the parameter is used to enable or
 disable fragmentation.
-- 
2.19.1