A-MPDU extension

Since there haven't been any objections to the A-MPDU proposal, here's a repost of the normative text for the A-MPDU field. I'll make the wiki changes next week and will post the patches to the relevant projects.

--- begin description ---

Bit Number: 20
Structure: u32 reference number,
u16 flags,
u8 delimiter CRC value,
u8 reserved
Required Alignment: 4 bytes

The presence of this field indicates that the frame was received as part of an a-MPDU.

The reference number is generated by the capture device and is the same across each subframe of an A-MPDU. Since the capture device might be capable of capturing multiple channels or data from multiple (concurrent) captures could be merged, the reference number is not guaranteed to be unique across different channels. As a result, applications should use the channel information together with the reference number to identify the subframes belonging to the same A-MPDU.

The following flags are defined:

0x0001: driver reports 0-length subframes
0x0002: frame is 0-length subframe (valid only if 0x0001 is set) 0x0004: last subframe is known (should be set for all subframes in an

        A-MPDU)

0x0008: this frame is the last subframe
0x0010: delimiter CRC error
0x0020: delimiter CRC value known: the delimiter CRC value field is
valid
0xffc0: reserved

Within an A-MPDU, the subframe index can be determined by the application so it is not included, but depending on the driver reporting this may miss 0-length subframes.

--- end of description ---

johannes

Ok I've made the wiki changes and posted the wireshark patch to the bug
tracker: https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=7583

I'm on vacation this week and next, I'll take care of the Linux patches when I return (but they're in the queue already anyway, I just need to send them up)

johannes