Skip to content

Commit

Permalink
Make timestamp optional
Browse files Browse the repository at this point in the history 
This change makes the timestmap optional and also moves it past the
Options data. This way if the packet is compressed, the compression
would also include the options, as well as the timestamp.
  • Loading branch information
@saleyn
saleyn committed Aug 17, 2016
1 parent 5b04803 commit d1c0dda
Showing 1 changed file with 121 additions and 64 deletions.
185 changes: 121 additions & 64 deletions draft-tuexen-opsawg-pcapng.xml
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1937,90 +1937,171 @@ Section Header

<section title="Experimental Blocks (deserve further investigation)">

<section anchor="section_apb" title="Alternative Packet Blocks (experimental)">
<section anchor="section_apb" title="Alternative Packet Block (experimental)">

<t>Alternative Packet Block offers an intermediate layout between
the Simple Packet Block and the Enhanced Packet Block. Just like the
Enhanced Packet Block it stores a timestamp of each packet, but
all other fields in the fixed part of the Alternative Packet
Block's body are made optional and can be stored in the Options
section. The packet's body of this block MAY be compressed.
the Simple Packet Block and the Enhanced Packet Block. The
timestamp of a packet, and other fields that are present in the
Enhanced Packet Block are made optional in the Alternative Packet
Block and can be stored in the Options section. The Options,
Timestmap, and packet's body of this block MAY be compressed.
This packet block type is intended for use cases that store large
number of packets, are concerned about storage size and optionally
engage compression. This block type has minimal overhead of 16
octets in storing packet data (size of: 'Block Type',
2 * 'Block Total Length', 'APB Flags').
</t>

<figure anchor="formatapb" title="Alternative Packet Block Format">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------------------------------------------------------+
0 | Block Type = 0x00000010 |
0 | Block Type = 0x0000000A |
+---------------------------------------------------------------+
4 | Block Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Timestamp (High) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 | Timestamp (Low) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 / /
/ Options (variable) /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ /
/ Packet Data /
/ variable length, padded to 32 bits /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | APB Flags (apb_flags, code = 0x2001) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \
12 / / \
/ Options (variable) / +
/ / |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Optional Timestamp (High) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +- This part MAY
| Optional Timestamp (Low) | | be compressed
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
/ / |
/ Packet Data / |
/ variable length, padded to 32 bits / +
/ / /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
| Block Total Length |
+---------------------------------------------------------------+
</artwork>
</figure>

<t>The permissible options listed in the table below are of
Simple Option type (see <xref target="section_simple_option"/>)
<t>The Alternative Packet Block has the following fields:
<list style="symbols">
<t>Block Type: the block type of the Enhanced
Packet Block is 0x0A</t>

<t>Block Total Length: total size of this block,
as described in <xref target="section_block"/></t>

<t>APB Flags Option: Alternative
Packet Block Flags - MANDATORY option formatted as Simple Option
(see <xref target="section_simple_option"/>)
with code 0x2001. The APB Flags indicate presence of a Timestamp,
uncompressed Options size, and characteristics of the Packet Data.
See <xref target="apb_flags"/> for permissible bit settings.
This option MAY include total byte size of Options. If the size
is specified, then the opt_endofopt option is OPTIONAL. The value
of apb_opt_size is the number of octets comprising the entire
Options section in this block not counting the APB Flags. If
present, this option MUST be the first one in the Options data.</t>

<t>Options: list of permissible option values listed in the table
below are of Simple Option type (see
<xref target="section_simple_option"/>). The Options MAY be
compressed if the Compression Bits of the apb_flags are on.</t>

<t>Optional Timestmap (High) and Timestamp (Low): upper 32 bits
and lower 32 bits of a 64-bit timestamp. If the Timestamp bit of
the apb_flags is on, then the Timestamp (High/Low) is present
after the Options. If there is no apb_flags option or the
Timestamp bit of the apb_flags option is off, then the timestamp
is not present. If the Compression bits of the apb_flags option
are on, then the Options, Timestamp, and Packet Data are
compressed using Compression Type specified in the apb_flags.
Otherwise it's not compressed.
The timestamp is a single 64-bit unsigned integer that
represents the number of units of time that have elapsed since
1/1/1970 00:00:00 UTC. The length of a unit of time is specified
by the 'if_tsresol' option (see <xref target="format_idb"/>) of
the Interface Description block referenced by this packet.
Note that, unlike timestamps in the libpcap file format,
timestamps in Enhanced Packet Blocks are not saved as two 32-bit
values that represent the seconds and microseconds that have
elapsed since 1/1/1970 00:00:00 UTC. Timestamps in Enhanced
Packet Blocks are saved as two 32-bit words that represent
the upper and lower 32 bits of a single 64-bit quantity.</t>

</list>
</t>

<texttable title="Alternative Packet Block Flags" anchor="apb_flags">
<ttcol align="left">Bit Number</ttcol>
<ttcol align="left">Description</ttcol>

<c>0</c>
<c>Timestamp bit (0 = no timestamp, 1 = has timestmap)</c>

<c>1-2</c>
<c>Packet Direction. (00 = information not
available, 01 = inbound packet, 10 = outbound packet)</c>

<c>3-5</c>
<c>Reception Type (000 = not specified, 001 = unicast,
010 = multicast, 011 = broadcast, 100 = promiscuous).</c>

<c>6-11</c>
<c>Compression Type. When specified, the optional Timestamp and
Packet Data contents are compressed. Permissible types:
0 (uncompressed), 1 (lzw), 2 (gzip), 3 (bzip2), 4 (zip),
5 (7z), 6 (lzo), 7 (ucl), 8 (snappy), other???</c>

<c>12-15</c>
<c>Reserved</c>

<c>16-23</c>
<c>Total uncompressed byte size of Options in this section
excluding the APB Flags. This setting is OPTIONAL. If set to 0,
then opt_endofopt is REQUIRED.</c>
</texttable>

<t>Options are described in the table below:</t>

<texttable anchor="options_apb" title="Alternative Packet Block Options">
<ttcol align="left">Name</ttcol>
<ttcol align="left">Code</ttcol>
<ttcol align="left">Length</ttcol>
<ttcol align="left">Multiple allowed?</ttcol>

<c>apb_opt_size</c>
<c>0x2001</c>
<c>-</c>
<c>no</c>

<c>apb_orig_len</c>
<c>0x2002</c>
<c>-</c>
<c>no</c>

<c>apb_iface_id</c>
<c>apb_capt_len</c>
<c>0x2003</c>
<c>-</c>
<c>no</c>

<c>apb_flags</c>
<c>apb_iface_id</c>
<c>0x2004</c>
<c>-</c>
<c>no</c>

</texttable>

<t>
<list hangIndent="8" style="hanging">
<t hangText="apb_opt_size:"><vspace blankLines="0"/>
Total byte size of options. If this option is specified, then
the opt_endofopt option is OPTIONAL. The value of apb_opt_size
is the number of octets comprising the entire Options section in
this block. If present, this option MUST be the first one in the
Options data.</t>

<t hangText="apb_orig_len:"><vspace blankLines="0"/>Packet's
Original Length. Actual length of the packet when it was
<t hangText="apb_orig_len:"><vspace blankLines="0"/>Original
Packet Length. Actual length of the packet when it was
transmitted on the network. It can be different from captured
packet length, which is the min(snapshot length, bytes left in
the block), if the packet has been truncated by the capture
packet length if the packet has been truncated by the capture
process.</t>

<t hangText="apb_capt_len:"><vspace blankLines="0"/>Captured
Packet Length: number of octets captured from the packet (i.e.
the length of the uncompressed Packet Data field). It will be
the minimum value among the Original Packet Length and the
snapshot length for the interface (SnapLen, defined in
<xref target="format_idb"/>). The value of this field does not
include the padding octets added at the end of the Packet Data
field to align the Packet Data field to a 32-bit boundary.</t>

<t hangText="apb_iface_id:"><vspace blankLines="0"/>It
specifies the interface this packet comes from; the correct
interface will be the one whose Interface Description Block
Expand All @@ -2030,33 +2111,9 @@ Section Header
matching interface description block MUST exist. If this option
is not defined, interface ID defaults to 0.</t>

<t hangText="apb_flags:"><vspace blankLines="0"/>Alternative
Packet Block Flags indicate characteristics of the Packet Data.
See <xref target="apb_flags"/> for permissible bit settings.</t>
</list>
</t>

<texttable title="Alternative Packet Block Flags" anchor="apb_flags">
<ttcol align="left">Bit Number</ttcol>
<ttcol align="left">Description</ttcol>

<c>0-1</c>
<c>Inbound / Outbound packet (00 = information not
available, 01 = inbound, 10 = outbound)</c>

<c>2-4</c>
<c>Reception type (000 = not specified, 001 = unicast,
010 = multicast, 011 = broadcast, 100 = promiscuous).</c>

<c>5-12</c>
<c>Compression type. When specified, the Packet Data
content is compressed. Permissible types:
0 (uncompressed), 1 (lzw), 2 (gzip), 3 (bzip2), 4 (zip),
5 (7z), 6 (lzo), 7 (ucl), 8 (snappy), other???</c>

<c>13-23</c>
<c>Reserved</c>
</texttable>
</section>

<section title="Compression Block (experimental)">
Expand Down

0 comments on commit d1c0dda

Please sign in to comment.