openwrt/package/hostapd/patches/110-nl80211_socketfilter.patch

--- a/hostapd/driver_nl80211.c
+++ b/hostapd/driver_nl80211.c
@@ -27,6 +27,7 @@
 #include <net/if.h>
 #include <netpacket/packet.h>
 #include "wireless_copy.h"
+#include <linux/filter.h>
 #include <net/if_arp.h>
 
 #include "hostapd.h"
@@ -1728,6 +1729,9 @@ static void handle_frame(struct hostapd_
 		case WLAN_FC_TODS:
 			bssid = hdr->addr1;
 			break;
+		case WLAN_FC_FROMDS:
+			bssid = hdr->addr2;
+			break;
 		default:
 			/* discard */
 			return;
@@ -1908,6 +1912,150 @@ static void handle_monitor_read(int sock
 }
 
 
+/*
+ * we post-process the filter code later and rewrite
+ * this to the offset to the last instruction
+ */
+#define PASS	0xFF
+#define FAIL	0xFE
+
+static struct sock_filter msock_filter_insns[] = {
+	/*
+	 * do a little-endian load of the radiotap length field
+	 */
+	/* load lower byte into A */
+	BPF_STMT(BPF_LD  | BPF_B | BPF_ABS, 2),
+	/* put it into X (== index register) */
+	BPF_STMT(BPF_MISC| BPF_TAX, 0),
+	/* load upper byte into A */
+	BPF_STMT(BPF_LD  | BPF_B | BPF_ABS, 3),
+	/* left-shift it by 8 */
+	BPF_STMT(BPF_ALU | BPF_LSH | BPF_K, 8),
+	/* or with X */
+	BPF_STMT(BPF_ALU | BPF_OR | BPF_X, 0),
+	/* put result into X */
+	BPF_STMT(BPF_MISC| BPF_TAX, 0),
+
+	/*
+	 * Allow management frames through, this also gives us those
+	 * management frames that we sent ourselves with status
+	 */
+	/* load the lower byte of the IEEE 802.11 frame control field */
+	BPF_STMT(BPF_LD  | BPF_B | BPF_IND, 0),
+	/* mask off frame type and version */
+	BPF_STMT(BPF_ALU | BPF_AND | BPF_K, 0xF),
+	/* accept frame if it's both 0, fall through otherwise */
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0, PASS, 0),
+
+	/*
+	 * TODO: add a bit to radiotap RX flags that indicates
+	 * that the sending station is not associated, then
+	 * add a filter here that filters on our DA and that flag
+	 * to allow us to deauth frames to that bad station.
+	 *
+	 * Not a regression -- we didn't do it before either.
+	 */
+
+#if 0
+	/*
+	 * drop non-data frames, WDS frames
+	 */
+	/* load the lower byte of the frame control field */
+	BPF_STMT(BPF_LD   | BPF_B | BPF_IND, 0),
+	/* mask off QoS bit */
+	BPF_STMT(BPF_ALU  | BPF_AND | BPF_K, 0x0c),
+	/* drop non-data frames */
+	BPF_JUMP(BPF_JMP  | BPF_JEQ | BPF_K, 8, 0, FAIL),
+	/* load the upper byte of the frame control field */
+	BPF_STMT(BPF_LD   | BPF_B | BPF_IND, 0),
+	/* mask off toDS/fromDS */
+	BPF_STMT(BPF_ALU  | BPF_AND | BPF_K, 0x03),
+	/* drop WDS frames */
+	BPF_JUMP(BPF_JMP  | BPF_JEQ | BPF_K, 3, FAIL, 0),
+#endif
+
+	/*
+	 * add header length to index
+	 */
+	/* load the lower byte of the frame control field */
+	BPF_STMT(BPF_LD   | BPF_B | BPF_IND, 0),
+	/* mask off QoS bit */
+	BPF_STMT(BPF_ALU  | BPF_AND | BPF_K, 0x80),
+	/* right shift it by 6 to give 0 or 2 */
+	BPF_STMT(BPF_ALU  | BPF_RSH | BPF_K, 6),
+	/* add data frame header length */
+	BPF_STMT(BPF_ALU  | BPF_ADD | BPF_K, 24),
+	/* add index, was start of 802.11 header */
+	BPF_STMT(BPF_ALU  | BPF_ADD | BPF_X, 0),
+	/* move to index, now start of LL header */
+	BPF_STMT(BPF_MISC | BPF_TAX, 0),
+
+	/*
+	 * Accept empty data frames, we use those for
+	 * polling activity.
+	 */
+	BPF_STMT(BPF_LD  | BPF_W | BPF_LEN, 0),
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_X, 0, PASS, 0),
+
+	/*
+	 * Accept EAPOL frames
+	 */
+	BPF_STMT(BPF_LD  | BPF_W | BPF_IND, 0),
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0xAAAA0300, 0, FAIL),
+	BPF_STMT(BPF_LD  | BPF_W | BPF_IND, 4),
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0x0000888E, PASS, FAIL),
+
+	/* keep these last two statements or change the code below */
+	/* return 0 == "DROP" */
+	BPF_STMT(BPF_RET | BPF_K, 0),
+	/* return ~0 == "keep all" */
+	BPF_STMT(BPF_RET | BPF_K, ~0),
+};
+
+static struct sock_fprog msock_filter = {
+	.len = sizeof(msock_filter_insns)/sizeof(msock_filter_insns[0]),
+	.filter = msock_filter_insns,
+};
+
+
+static int add_monitor_filter(int s)
+{
+	int idx;
+
+	/* rewrite all PASS/FAIL jump offsets */
+	for (idx = 0; idx < msock_filter.len; idx++) {
+		struct sock_filter *insn = &msock_filter_insns[idx];
+
+		if (BPF_CLASS(insn->code) == BPF_JMP) {
+			if (insn->code == (BPF_JMP|BPF_JA)) {
+				if (insn->k == PASS)
+					insn->k = msock_filter.len - idx - 2;
+				else if (insn->k == FAIL)
+					insn->k = msock_filter.len - idx - 3;
+			}
+
+			if (insn->jt == PASS)
+				insn->jt = msock_filter.len - idx - 2;
+			else if (insn->jt == FAIL)
+				insn->jt = msock_filter.len - idx - 3;
+
+			if (insn->jf == PASS)
+				insn->jf = msock_filter.len - idx - 2;
+			else if (insn->jf == FAIL)
+				insn->jf = msock_filter.len - idx - 3;
+		}
+	}
+
+	if (setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER,
+		       &msock_filter, sizeof(msock_filter))) {
+		perror("SO_ATTACH_FILTER");
+		return -1;
+	}
+
+	return 0;
+}
+
+
 static int nl80211_create_monitor_interface(struct i802_driver_data *drv)
 {
 	char buf[IFNAMSIZ];
@@ -1936,6 +2084,12 @@ static int nl80211_create_monitor_interf
 		goto error;
 	}
 
+	if (add_monitor_filter(drv->monitor_sock)) {
+		wpa_printf(MSG_INFO, "Failed to set socket filter for monitor "
+			   "interface; do filtering in user space");
+		/* This works, but will cost in performance. */
+	}
+
 	if (bind(drv->monitor_sock, (struct sockaddr *) &ll,
 		 sizeof(ll)) < 0) {
 		perror("monitor socket bind");