[PATCH 5/8] alfred: vis: report failures while reading the answer

[Sven Eckelmann <sven@narfation.org>]

vis_read_answer() returns NULL for a:

* closed connection
* read error
* malformed packet
* unexpected answer

All of them were indistinguishable from the latter regular end of the
answer. Even on errors batadv-vis printed an empty (well formed document).
An error could not directly be detected by the return code.

Report the error state of the packet parsing separately and use it for the
exit code.

Fixes: 2e3e312f7757 ("alfred: add vis")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 vis/vis.c | 40 +++++++++++++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 9 deletions(-)

diff --git a/vis/vis.c b/vis/vis.c
index 33fa692..451d79c 100644
--- a/vis/vis.c
+++ b/vis/vis.c
@@ -718,7 +718,8 @@ static ssize_t read_full(int fd, void *buf, size_t count)
 	return read_len;
 }
 
-static struct vis_v1 *vis_receive_answer_packet(int sock, uint16_t *len)
+static struct vis_v1 *vis_receive_answer_packet(int sock, uint16_t *len,
+						int *error)
 {
 	struct alfred_push_data_v0 *push;
 	static uint8_t buf[65536];
@@ -727,15 +728,29 @@ static struct vis_v1 *vis_receive_answer_packet(int sock, uint16_t *len)
 	int ret;
 	int l;
 
+	*error = -1;
+
 	ret = read_full(sock, buf, sizeof(*tlv));
-	if (ret < 0)
+	if (ret < 0) {
+		perror("read from unix socket failed");
 		return NULL;
+	}
+
+	/* end of the answer */
+	if (ret == 0) {
+		*error = 0;
+		return NULL;
+	}
 
 	if (ret < (int)sizeof(*tlv))
 		return NULL;
 
 	tlv = (struct alfred_tlv *)buf;
-	/* TODO: might return an ALFRED_STATUS_ERROR too, handle it */
+	if (tlv->type == ALFRED_STATUS_ERROR) {
+		fprintf(stderr, "Request of vis data failed\n");
+		return NULL;
+	}
+
 	if (tlv->type != ALFRED_PUSH_DATA)
 		return NULL;
 
@@ -763,6 +778,8 @@ static struct vis_v1 *vis_receive_answer_packet(int sock, uint16_t *len)
 	if (data->header.version != VIS_PACKETVERSION)
 		return NULL;
 
+	*error = 0;
+
 	return (struct vis_v1 *) data->data;
 }
 
@@ -995,6 +1012,7 @@ static int vis_read_answer(struct globals *globals)
 	struct vis_iface *ifaces;
 	struct vis_v1 *vis_data;
 	uint16_t len;
+	int ret = 0;
 
 	switch (globals->vis_format) {
 	case FORMAT_DOT:
@@ -1013,7 +1031,7 @@ static int vis_read_answer(struct globals *globals)
 	ops->preamble();
 
 	while ((vis_data =
-		vis_receive_answer_packet(globals->unix_sock, &len)) != NULL) {
+		vis_receive_answer_packet(globals->unix_sock, &len, &ret)) != NULL) {
 		if (len < sizeof(*vis_data))
 			return -1;
 
@@ -1037,19 +1055,21 @@ static int vis_read_answer(struct globals *globals)
 	}
 	ops->postamble();
 
-	return 0;
+	return ret;
 }
 
 static int vis_get_data(struct globals *globals)
 {
+	int ret;
+
 	globals->unix_sock = vis_request_data(globals);
 	if (globals->unix_sock < 0)
 		return -1;
 
-	vis_read_answer(globals);
+	ret = vis_read_answer(globals);
 	close(globals->unix_sock);
 
-	return 0;
+	return ret;
 }
 
 static void vis_usage(void)
@@ -1176,8 +1196,10 @@ int main(int argc, char *argv[])
 		return vis_server(globals);
 		break;
 	case OPMODE_CLIENT:
-		return vis_get_data(globals);
-		break;
+		if (vis_get_data(globals) < 0)
+			return 1;
+
+		return 0;
 	}
 
 	return 0;

-- 
2.47.3