[LEDE-DEV] [PATCH iwinfo] nl80211: Do not block when driver aborts scan

[osivertsson at gmail.com]

From: Olof Sivertsson <olof.sivertsson at zenterio.com>

Drivers may abort a scan by calling cfg80211_scan_done() with a struct
cfg80211_scan_info that sets aborted to true.

To avoid blocking forever consider both NL80211_CMD_NEW_SCAN_RESULTS
and NL80211_CMD_SCAN_ABORTED when waiting for scan results.

Tested with Broadcom's bcmdhd driver.

Signed-off-by: Olof Sivertsson <olof.sivertsson at zenterio.com>
---
 iwinfo_nl80211.c | 12 ++++++++----
 iwinfo_nl80211.h |  1 +
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/iwinfo_nl80211.c b/iwinfo_nl80211.c
index 2776531..d84da24 100644
--- a/iwinfo_nl80211.c
+++ b/iwinfo_nl80211.c
@@ -510,7 +510,7 @@ static int nl80211_wait_cb(struct nl_msg *msg, void *arg)
 	struct nl80211_event_conveyor *cv = arg;
 	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
 
-	if (gnlh->cmd == cv->wait)
+	if (gnlh->cmd == cv->wait || gnlh->cmd == cv->cancel)
 		cv->recv = gnlh->cmd;
 
 	return NL_SKIP;
@@ -521,9 +521,9 @@ static int nl80211_wait_seq_check(struct nl_msg *msg, void *arg)
 	return NL_OK;
 }
 
-static int nl80211_wait(const char *family, const char *group, int cmd)
+static int nl80211_wait(const char *family, const char *group, int wait, int cancel)
 {
-	struct nl80211_event_conveyor cv = { .wait = cmd };
+	struct nl80211_event_conveyor cv = { .wait = wait, .cancel = cancel };
 	struct nl_cb *cb;
 	int err = 0;
 
@@ -544,6 +544,9 @@ static int nl80211_wait(const char *family, const char *group, int cmd)
 
 	nl_cb_put(cb);
 
+	if (cv.recv == cancel)
+		return -ECANCELED;
+
 	return err;
 }
 
@@ -2091,7 +2094,8 @@ static int nl80211_get_scanlist_nl(const char *ifname, char *buf, int *len)
 	if (nl80211_request(ifname, NL80211_CMD_TRIGGER_SCAN, 0, NULL, NULL))
 		goto out;
 
-	if (nl80211_wait("nl80211", "scan", NL80211_CMD_NEW_SCAN_RESULTS))
+	if (nl80211_wait("nl80211", "scan",
+			 NL80211_CMD_NEW_SCAN_RESULTS, NL80211_CMD_SCAN_ABORTED))
 		goto out;
 
 	if (nl80211_request(ifname, NL80211_CMD_GET_SCAN, NLM_F_DUMP,
diff --git a/iwinfo_nl80211.h b/iwinfo_nl80211.h
index bb5117e..38089d2 100644
--- a/iwinfo_nl80211.h
+++ b/iwinfo_nl80211.h
@@ -49,6 +49,7 @@ struct nl80211_msg_conveyor {
 
 struct nl80211_event_conveyor {
 	int wait;
+	int cancel;
 	int recv;
 };
 
-- 
2.15.1