iwinfo: generic improvement of assoclist handling

include/iwinfo.h

@@ -409,6 +409,13 @@ struct iwinfo_ops {
 	int (*hardware_name)(const char *, char *);
 	int (*encryption)(const char *, char *);
 	int (*phyname)(const char *, char *);
+	/*
+	 * assoclist might receive a NULL buf as second element.
+	 * In such case assoclist should only return the length
+	 * of the expected buffer.
+	 * Third element is always set to the size of the buffer.
+	 * assoclist should stop parsing elements if this is reached.
+	 */
 	int (*assoclist)(const char *, char *, int *);
 	int (*txpwrlist)(const char *, char *, int *);
 	int (*scanlist)(const char *, char *, int *);

iwinfo_cli.c

@@ -784,12 +784,12 @@ static void print_freqlist(const struct iwinfo_ops *iw, const char *ifname)
 
 static void print_assoclist(const struct iwinfo_ops *iw, const char *ifname)
 {
-	int i, len;
-	char buf[IWINFO_BUFSIZE];
+	int i, len = 0;
+	char *buf = NULL;
 	struct iwinfo_assoclist_entry *e;
 
-	if (iw->assoclist(ifname, buf, &len))
-	{
+	/* Call assoclist with NULL buf to get number of element to alloc */
+	if (iw->assoclist(ifname, NULL, &len)) {
 		printf("No information available\n");
 		return;
 	}
@@ -799,6 +799,24 @@ static void print_assoclist(const struct iwinfo_ops *iw, const char *ifname)
 		return;
 	}
 
+	buf = malloc(len * sizeof(*e));
+	if (!buf) {
+		printf("No space to allocate assoc elements buf\n");
+		return;
+	}
+
+	/* Pass to assoclist the size of buf allocated with len */
+	if (iw->assoclist(ifname, buf, &len))
+	{
+		printf("No information available\n");
+		goto exit;
+	}
+	else if (len <= 0)
+	{
+		printf("No station connected\n");
+		goto exit;
+	}
+
 	for (i = 0; i < len; i += sizeof(struct iwinfo_assoclist_entry))
 	{
 		e = (struct iwinfo_assoclist_entry *) &buf[i];
@@ -823,6 +841,9 @@ static void print_assoclist(const struct iwinfo_ops *iw, const char *ifname)
 		printf("	expected throughput: %s\n\n",
 			format_rate(e->thr));
 	}
+
+exit:
+	free(buf);
 }
 
 

iwinfo_madwifi.c

@@ -772,6 +772,14 @@ static int madwifi_get_assoclist(const char *ifname, char *buf, int *len)
 		do {
 			si = (struct ieee80211req_sta_info *) cp;
 
+			/* If buf is NULL, we only count the station */
+			if (!buf)
+				goto next;
+
+			/* stop parsing more elements as we reached max buf */
+			if (bl + sizeof(entry) > *len)
+				break;
+
 			memset(&entry, 0, sizeof(entry));
 
 			entry.signal = (si->isi_rssi - 95);
@@ -797,6 +805,7 @@ static int madwifi_get_assoclist(const char *ifname, char *buf, int *len)
 
 			memcpy(&buf[bl], &entry, sizeof(struct iwinfo_assoclist_entry));
 
+next:
 			bl += sizeof(struct iwinfo_assoclist_entry);
 			cp += si->isi_len;
 			tl -= si->isi_len;

iwinfo_nl80211.c

@@ -2254,6 +2254,14 @@ static int nl80211_get_assoclist_cb(struct nl_msg *msg, void *arg)
 		[NL80211_RATE_INFO_SHORT_GI]     = { .type = NLA_FLAG   },
 	};
 
+	/* With NULL buf, we just count the stations */
+	if (!arr->buf)
+		goto exit;
+
+	/* stop parsing more elements as we reached max buf */
+	if (arr->count >= arr->max)
+		return NL_STOP;
+
 	/* advance to end of array */
 	e += arr->count;
 	memset(e, 0, sizeof(*e));
@@ -2369,6 +2377,8 @@ static int nl80211_get_assoclist_cb(struct nl_msg *msg, void *arg)
 	}
 
 	e->noise = 0; /* filled in by caller */
+
+exit:
 	arr->count++;
 
 	return NL_SKIP;
@@ -2397,6 +2407,13 @@ static int nl80211_get_assoclist(const char *ifname, char *buf, int *len)
 	struct nl80211_array_buf arr = { .buf = buf, .count = 0 };
 	struct iwinfo_assoclist_entry *e;
 
+	/* If len is not set, use IWINFO_BUFSIZE by default */
+	if (!*len)
+		*len = IWINFO_BUFSIZE;
+
+	/* Limit element to the preallocated space */
+	arr.max = *len / sizeof(*e);
+
 	if ((d = opendir("/sys/class/net")) != NULL)
 	{
 		while ((de = readdir(d)) != NULL)
@@ -2412,7 +2429,8 @@ static int nl80211_get_assoclist(const char *ifname, char *buf, int *len)
 
 		closedir(d);
 
-		if (!nl80211_get_noise(ifname, &noise))
+		/* Skip setting noise if we are just counting station */
+		if (arr.buf && !nl80211_get_noise(ifname, &noise))
 			for (i = 0, e = arr.buf; i < arr.count; i++, e++)
 				e->noise = noise;
 

iwinfo_nl80211.h

@@ -67,6 +67,7 @@ struct nl80211_rssi_rate {
 struct nl80211_array_buf {
 	void *buf;
 	int count;
+	int max;
 };
 
 #endif