nl80211: Optimize memory use in nl80211_get_assoc_freq()

Do not use the generic bss_info_handler() design to fetch all scan
results into temporary memory buffer. Instead, use a separate BSS info
handler that fetches the requested information without fully parsing the
BSS entries and without allocating any memory for collecting all the
results.

This is also simplifying bss_info_handler() and nl80211_parse_bss_info()
design by getting rid of the special case that was used only for
nl80211_get_assoc_freq() and not normal scan result fetching.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/drivers/driver_nl80211.c

@@ -1181,16 +1181,70 @@ static void wpa_driver_nl80211_event_rtm_dellink(void *ctx,
 }
 
 
+struct nl80211_get_assoc_freq_arg {
+	struct wpa_driver_nl80211_data *drv;
+	unsigned int assoc_freq;
+	unsigned int ibss_freq;
+	u8 assoc_bssid[ETH_ALEN];
+};
+
+static int nl80211_get_assoc_freq_handler(struct nl_msg *msg, void *arg)
+{
+	struct nlattr *tb[NL80211_ATTR_MAX + 1];
+	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
+	struct nlattr *bss[NL80211_BSS_MAX + 1];
+	static struct nla_policy bss_policy[NL80211_BSS_MAX + 1] = {
+		[NL80211_BSS_BSSID] = { .type = NLA_UNSPEC },
+		[NL80211_BSS_FREQUENCY] = { .type = NLA_U32 },
+		[NL80211_BSS_STATUS] = { .type = NLA_U32 },
+	};
+	struct nl80211_get_assoc_freq_arg *ctx = arg;
+	enum nl80211_bss_status status;
+
+	nla_parse(tb, NL80211_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
+		  genlmsg_attrlen(gnlh, 0), NULL);
+	if (!tb[NL80211_ATTR_BSS] ||
+	    nla_parse_nested(bss, NL80211_BSS_MAX, tb[NL80211_ATTR_BSS],
+			     bss_policy) ||
+	    !bss[NL80211_BSS_STATUS])
+		return NL_SKIP;
+
+	status = nla_get_u32(bss[NL80211_BSS_STATUS]);
+	if (status == NL80211_BSS_STATUS_ASSOCIATED &&
+	    bss[NL80211_BSS_FREQUENCY]) {
+		ctx->assoc_freq = nla_get_u32(bss[NL80211_BSS_FREQUENCY]);
+		wpa_printf(MSG_DEBUG, "nl80211: Associated on %u MHz",
+			   ctx->assoc_freq);
+	}
+	if (status == NL80211_BSS_STATUS_IBSS_JOINED &&
+	    bss[NL80211_BSS_FREQUENCY]) {
+		ctx->ibss_freq = nla_get_u32(bss[NL80211_BSS_FREQUENCY]);
+		wpa_printf(MSG_DEBUG, "nl80211: IBSS-joined on %u MHz",
+			   ctx->ibss_freq);
+	}
+	if (status == NL80211_BSS_STATUS_ASSOCIATED &&
+	    bss[NL80211_BSS_BSSID]) {
+		os_memcpy(ctx->assoc_bssid,
+			  nla_data(bss[NL80211_BSS_BSSID]), ETH_ALEN);
+		wpa_printf(MSG_DEBUG, "nl80211: Associated with "
+			   MACSTR, MAC2STR(ctx->assoc_bssid));
+	}
+
+	return NL_SKIP;
+}
+
+
 unsigned int nl80211_get_assoc_freq(struct wpa_driver_nl80211_data *drv)
 {
 	struct nl_msg *msg;
 	int ret;
-	struct nl80211_bss_info_arg arg;
+	struct nl80211_get_assoc_freq_arg arg;
 
 	msg = nl80211_drv_msg(drv, NLM_F_DUMP, NL80211_CMD_GET_SCAN);
 	os_memset(&arg, 0, sizeof(arg));
 	arg.drv = drv;
-	ret = send_and_recv_msgs(drv, msg, bss_info_handler, &arg);
+	ret = send_and_recv_msgs(drv, msg, nl80211_get_assoc_freq_handler,
+				 &arg);
 	if (ret == 0) {
 		unsigned int freq = drv->nlmode == NL80211_IFTYPE_ADHOC ?
 			arg.ibss_freq : arg.assoc_freq;

src/drivers/driver_nl80211.h

@@ -282,15 +282,6 @@ int wpa_driver_set_ap_wps_p2p_ie(void *priv, const struct wpabuf *beacon,
 
 /* driver_nl80211_scan.c */
 
-struct nl80211_bss_info_arg {
-	struct wpa_driver_nl80211_data *drv;
-	struct wpa_scan_results *res;
-	unsigned int assoc_freq;
-	unsigned int ibss_freq;
-	u8 assoc_bssid[ETH_ALEN];
-};
-
-int bss_info_handler(struct nl_msg *msg, void *arg);
 void wpa_driver_nl80211_scan_timeout(void *eloop_ctx, void *timeout_ctx);
 int wpa_driver_nl80211_scan(struct i802_bss *bss,
 			    struct wpa_driver_scan_params *params);

src/drivers/driver_nl80211_scan.c

@@ -628,7 +628,7 @@ static int nl80211_scan_filtered(struct wpa_driver_nl80211_data *drv,
 
 static struct wpa_scan_res *
 nl80211_parse_bss_info(struct wpa_driver_nl80211_data *drv,
-		       struct nl_msg *msg, struct nl80211_bss_info_arg *_arg)
+		       struct nl_msg *msg)
 {
 	struct nlattr *tb[NL80211_ATTR_MAX + 1];
 	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
@@ -658,33 +658,6 @@ nl80211_parse_bss_info(struct wpa_driver_nl80211_data *drv,
 	if (nla_parse_nested(bss, NL80211_BSS_MAX, tb[NL80211_ATTR_BSS],
 			     bss_policy))
 		return NULL;
-	if (bss[NL80211_BSS_STATUS] && _arg) {
-		enum nl80211_bss_status status;
-		status = nla_get_u32(bss[NL80211_BSS_STATUS]);
-		if (status == NL80211_BSS_STATUS_ASSOCIATED &&
-		    bss[NL80211_BSS_FREQUENCY]) {
-			_arg->assoc_freq =
-				nla_get_u32(bss[NL80211_BSS_FREQUENCY]);
-			wpa_printf(MSG_DEBUG, "nl80211: Associated on %u MHz",
-				   _arg->assoc_freq);
-		}
-		if (status == NL80211_BSS_STATUS_IBSS_JOINED &&
-		    bss[NL80211_BSS_FREQUENCY]) {
-			_arg->ibss_freq =
-				nla_get_u32(bss[NL80211_BSS_FREQUENCY]);
-			wpa_printf(MSG_DEBUG, "nl80211: IBSS-joined on %u MHz",
-				   _arg->ibss_freq);
-		}
-		if (status == NL80211_BSS_STATUS_ASSOCIATED &&
-		    bss[NL80211_BSS_BSSID]) {
-			os_memcpy(_arg->assoc_bssid,
-				  nla_data(bss[NL80211_BSS_BSSID]), ETH_ALEN);
-			wpa_printf(MSG_DEBUG, "nl80211: Associated with "
-				   MACSTR, MAC2STR(_arg->assoc_bssid));
-		}
-	}
-	if (_arg && !_arg->res)
-		return NULL;
 	if (bss[NL80211_BSS_INFORMATION_ELEMENTS]) {
 		ie = nla_data(bss[NL80211_BSS_INFORMATION_ELEMENTS]);
 		ie_len = nla_len(bss[NL80211_BSS_INFORMATION_ELEMENTS]);
@@ -761,14 +734,19 @@ nl80211_parse_bss_info(struct wpa_driver_nl80211_data *drv,
 }
 
 
-int bss_info_handler(struct nl_msg *msg, void *arg)
+struct nl80211_bss_info_arg {
+	struct wpa_driver_nl80211_data *drv;
+	struct wpa_scan_results *res;
+};
+
+static int bss_info_handler(struct nl_msg *msg, void *arg)
 {
 	struct nl80211_bss_info_arg *_arg = arg;
 	struct wpa_scan_results *res = _arg->res;
 	struct wpa_scan_res **tmp;
 	struct wpa_scan_res *r;
 
-	r = nl80211_parse_bss_info(_arg->drv, msg, _arg);
+	r = nl80211_parse_bss_info(_arg->drv, msg);
 	if (!r)
 		return NL_SKIP;
 
@@ -920,7 +898,7 @@ static int nl80211_dump_scan_handler(struct nl_msg *msg, void *arg)
 	struct nl80211_dump_scan_ctx *ctx = arg;
 	struct wpa_scan_res *r;
 
-	r = nl80211_parse_bss_info(ctx->drv, msg, NULL);
+	r = nl80211_parse_bss_info(ctx->drv, msg);
 	if (!r)
 		return NL_SKIP;
 	wpa_printf(MSG_DEBUG, "nl80211: %d " MACSTR " %d%s",