Do NOT assume that, just because a frame didn't show a "Malformed frame" error, it didn't have an FCS the "Malformed frame" errors are due to Wireshark thinking the FCS is frame data, and trying to dissect items larger than the 4 bytes of the FCS. When I looked at the same capture, and forced the "FCS at end" flag on, I found that a LOT of frames other than those frames had an FCS that Wireshark reported as valid. My experiment with my laptop with a wireless adapter Qualcomm Atheros AR9485WB-EG Wireless Network Adapter shows that Beacon and Reassociation Response packets have FCS and all other 802.11 packets don't have one. *((UCHAR*)Dot11RadiotapHeader + cur) |= IEEE80211_RADIOTAP_F_BADFCS // 0x40: frame failed FCS check If ((pwInfo->uReceiveFlags & DOT11_RECV_FLAG_RAW_PACKET_FCS_FAILURE) = DOT11_RECV_FLAG_RAW_PACKET_FCS_FAILURE) *((UCHAR*)Dot11RadiotapHeader + cur) = IEEE80211_RADIOTAP_F_FCS // 0x10: frame includes FCS *((UCHAR*)Dot11RadiotapHeader + cur) = 0x0 // 0x0: none PRadiotapHeader->it_present |= BIT(IEEE80211_RADIOTAP_FLAGS) We always have no FCS for all packets currently. If (TRUE) // The packet doesn't have FCS. My code is like below, and I want to know how to write the if condition. This is why I need to determine the availability of FCS in my driver. And the wrong Flags in the radiotap header will cause Wireshark to show Malformed Packet for those packets. I'm asking this because i'm adding Radiotap header ( ) to the packets and radiotap has a field called Flags that specified whether the 802.11 packet has a FCS or not. My question is how to determine whether a 802.11 raw packet has FCS (frame check sequence, 4bytes) in my driver? Then I switched my wireless adapter to Monitor Mode.īy now my filter driver can receive all the 802.11 control and management packets. I have bound it below NativeWiFi Filter so I can see 802.11 packets instead of fake Ethernet packets.Īnd I have set the NDIS_PACKET_TYPE_802_11_RAW_DATA and NDIS_PACKET_TYPE_802_11_RAW_MGMT in the packet filter based on: (v=vs.85).aspx, so I can receive the Raw 802.11 Packets indications from the miniport. I have a NDIS 6 filter driver working on Windows Vista and later systems.
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