When wpa_supplicant is running on a Linux interface that is configured in
promiscuous mode, and it is not a member of a bridge, incoming EAPOL
packets are processed regardless of the Destination Address in the frame.
As a consequence, there are situations where wpa_supplicant replies to
EAPOL packets that are not destined for it.
This behavior seems undesired (see IEEE Std 802.1X-2010, 11.4.a), and can
be avoided by attaching a BPF filter that lets the kernel discard packets
having pkt_type equal to PACKET_OTHERHOST.
Signed-off-by: Davide Caratti <davide.caratti@xxxxxxxxx>
---
src/l2_packet/l2_packet.h | 1 +
src/l2_packet/l2_packet_linux.c | 22 ++++++++++++++++++++++
wpa_supplicant/wpa_supplicant.c | 5 +++++
3 files changed, 28 insertions(+)
diff --git a/src/l2_packet/l2_packet.h b/src/l2_packet/l2_packet.h
index 2a4524582..53871774b 100644
--- a/src/l2_packet/l2_packet.h
+++ b/src/l2_packet/l2_packet.h
@@ -42,6 +42,7 @@ struct l2_ethhdr {
enum l2_packet_filter_type {
L2_PACKET_FILTER_DHCP,
L2_PACKET_FILTER_NDISC,
+ L2_PACKET_FILTER_PKTTYPE,
};
/**
diff --git a/src/l2_packet/l2_packet_linux.c b/src/l2_packet/l2_packet_linux.c
index 65b490679..c5d889dca 100644
--- a/src/l2_packet/l2_packet_linux.c
+++ b/src/l2_packet/l2_packet_linux.c
@@ -84,6 +84,25 @@ static const struct sock_fprog ndisc_sock_filter = {
.filter = ndisc_sock_filter_insns,
};
+/* drop packet if skb->pkt_type is PACKET_OTHERHOST (0x03). Generated by:
+ * $ bpfc - <<-EOF
+ * > ldb #type
+ * > jeq #0x03, drop
+ * > pass: ret #-1
+ * > drop: ret #0
+ * > EOF
+ */
+static struct sock_filter pkt_type_filter_insns[] = {
+ { 0x30, 0, 0, 0xfffff004 },
+ { 0x15, 1, 0, 0x00000003 },
+ { 0x6, 0, 0, 0xffffffff },
+ { 0x6, 0, 0, 0x00000000 },
+};
+
+static const struct sock_fprog pkt_type_sock_filter = {
+ .len = ARRAY_SIZE(pkt_type_filter_insns),
+ .filter = pkt_type_filter_insns,
+};
int l2_packet_get_own_addr(struct l2_packet_data *l2, u8 *addr)
{
@@ -471,6 +490,9 @@ int l2_packet_set_packet_filter(struct l2_packet_data *l2,
case L2_PACKET_FILTER_NDISC:
sock_filter = &ndisc_sock_filter;
break;
+ case L2_PACKET_FILTER_PKTTYPE:
+ sock_filter = &pkt_type_sock_filter;
+ break;
default:
return -1;
}
diff --git a/wpa_supplicant/wpa_supplicant.c b/wpa_supplicant/wpa_supplicant.c
index fcb267764..7e6844a75 100644
--- a/wpa_supplicant/wpa_supplicant.c
+++ b/wpa_supplicant/wpa_supplicant.c
@@ -3993,6 +3993,11 @@ int wpa_supplicant_update_mac_addr(struct wpa_supplicant *wpa_s)
wpa_supplicant_rx_eapol, wpa_s, 0);
if (wpa_s->l2 == NULL)
return -1;
+
+ if (l2_packet_set_packet_filter(wpa_s->l2,
+ L2_PACKET_FILTER_PKTTYPE))
+ wpa_msg(wpa_s, MSG_DEBUG,
+ "Failed to attach pkt_type filter");
} else {
const u8 *addr = wpa_drv_get_mac_addr(wpa_s);
if (addr)
--
2.14.3
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