netsniff-ng(8) [debian man page]
netsniff-ng(8) netsniff-ng-toolkit netsniff-ng(8)
NAME
netsniff-ng - the packet sniffing beast
SYNOPSIS
netsniff-ng -i|-d|--dev|--in <dev|pcap> -o|--out <dev|pcap|dir|txf> [-f|--filter <bpf-file>][-t|--type <type>][-F|--interval <uint>]
[-s|--silent][-J|--jumbo-support][-n|--num <uint>][-r|--rand] [-M|--no-promisc][-m|--mmap | -c|--clrw][-S|--ring-size <size>]
[-k|--kernel-pull <uint>][-b|--bind-cpu <cpu> | -B|--unbind-cpu <cpu>] [-H|--prio-high][-Q|--notouch-irq][-q|--less | -X|--hex |
-l|--ascii] [-v|--version][-h|--help]
DESCRIPTION
The first sniffer that invoked both, the zero-copy RX_RING as well as the zero-copy TX_RING for high-performance network I/O and
scatter/gather or mmaped PCAP I/O.
EXAMPLES
netsniff-ng --in eth0 --out dump.pcap
Capture traffic from interface 'eth0' and save it pcap file 'dump.pcap'
netsniff-ng --in any --filter http.bpf --payload
Capture HTTP traffic from any interface and print its payload on stdout
netsniff-ng --in wlan0 --bind-cpu 0,1
Capture all traffic from wlan0 interface. Schedule process on CPU 0 and 1.
OPTIONS
-i|-d|--dev|--in <dev|pcap>
Input source. Can be a network device or pcap file.
-o|--out <dev|pcap|dir|txf>
Output sink. Can be a network device, pcap file, a trafgen txf file or a directory. (There's only pcap to txf translation possible.)
-f|--filter <bpf-file>
Use BPF filter file from bpfc.
-t|--type <type>
Only handle packets of defined type:
- broadcast
- multicast
- others
- outgoing
-F|--interval <uint>
Dump interval in seconds. if -o is a directory, a new pcap will be created at each interval. The older files are left untouched.
(default value: 60 seconds)
-s|--silent
Do not print captured packets to stdout.
-J|--jumbo-support
Support for 64KB Super Jumbo Frames.
-n|--num <uint>
When zerp, capture/replay until SIGINT is received (default). When non-zero, capture/replay the number of packets.
-r|--rand
Randomize packet forwarding order (replay mode only).
-M|--no-promisc
Do not place the interface in promiscuous mode.
-m|--mmap
Mmap pcap file i.e., for replaying. Default: scatter/gather I/O.
-c|--clrw
Instead of using scatter/gather I/O use slower read(2)/write(2) I/O.
-S|--ring-size <size>
Manually set ring size in KB/MB/GB, e.g. '10MB'.
-k|--kernel-pull <uint>
Kernel pull from user interval in microseconds. Default is 10us. (replay mode only).
-b|--bind-cpu <cpu>
Bind to specific CPU (or CPU-range).
-B|--unbind-cpu <cpu>
Forbid to use specific CPU (or CPU-range).
-H|--prio-high
Run the process in high-priority mode.
-Q|--notouch-irq
Do not touch IRQ CPU affinity of NIC.
-q|--less
Print less-verbose packet information.
-X|--hex
Print packet data in hex format.
-l|--ascii
Print human-readable packet data.
-v|--version
Print version.
-h|--help
Print help text and lists all options.
AUTHOR
Written by Daniel Borkmann <daniel@netsniff-ng.org> and Emmanuel Roullit <emmanuel@netsniff-ng.org>
DOCUMENTATION
Documentation by Emmanuel Roullit <emmanuel@netsniff-ng.org>
BUGS
Please report bugs to <bugs@netsniff-ng.org>
2012-06-29 netsniff-ng(8)
Check Out this Related Man Page
NETSNIFF-NG(8) netsniff-ng toolkit NETSNIFF-NG(8)
NAME
netsniff-ng - the packet sniffing beast
SYNOPSIS
netsniff-ng { [options] [filter-expression] }
DESCRIPTION
netsniff-ng is a fast, minimal tool to analyze network packets, capture pcap files, replay pcap files, and redirect traffic between inter-
faces with the help of zero-copy packet(7) sockets. netsniff-ng uses both Linux specific RX_RING and TX_RING interfaces to perform zero-
copy. This is to avoid copy and system call overhead between kernel and user address space. When we started working on netsniff-ng, the
pcap(3) library did not use this zero-copy facility.
netsniff-ng is Linux specific, meaning there is no support for other operating systems. Therefore we can keep the code footprint quite min-
imal and to the point. Linux packet(7) sockets and its RX_RING and TX_RING interfaces bypass the normal packet processing path through the
networking stack. This is the fastest capturing or transmission performance one can get from user space out of the box, without having to
load unsupported or non-mainline third-party kernel modules. We explicitly refuse to build netsniff-ng on top of ntop/PF_RING. Not because
we do not like it (we do find it interesting), but because of the fact that it is not part of the mainline kernel. Therefore, the ntop
project has to maintain and sync out-of-tree drivers to adapt them to their DNA. Eventually, we went for untainted Linux kernel, since its
code has a higher rate of review, maintenance, security and bug fixes.
netsniff-ng also supports early packet filtering in the kernel. It has support for low-level and high-level packet filters that are trans-
lated into Berkeley Packet Filter instructions.
netsniff-ng can capture pcap files in several different pcap formats that are interoperable with other tools. It has different pcap I/O
methods supported (scatter-gather, mmap(2), read(2), and write(2)) for efficient to-disc capturing. netsniff-ng is also able to rotate
pcap files based on data size or time intervals, thus, making it a useful backend tool for subsequent traffic analysis.
netsniff-ng itself also supports analysis, replaying, and dumping of raw 802.11 frames. For online or offline analysis, netsniff-ng has a
built-in packet dissector for the current 802.3 (Ethernet), 802.11* (WLAN), ARP, MPLS, 802.1Q (VLAN), 802.1QinQ, LLDP, IPv4, IPv6, ICMPv4,
ICMPv6, IGMP, TCP and UDP, including GeoIP location analysis. Since netsniff-ng does not establish any state or perform reassembly during
packet dissection, its memory footprint is quite low, thus, making netsniff-ng quite efficient for offline analysis of large pcap files as
well.
Note that netsniff-ng is currently not multithreaded. However, this does not prevent you from starting multiple netsniff-ng instances that
are pinned to different, non-overlapping CPUs and f.e. have different BPF filters attached. Likely that at some point in time your hard-
disc might become a bottleneck assuming you do not rotate such pcaps in ram (and from there periodically scheduled move to slower medias).
You can then use mergecap(1) to transform all pcaps into a single large pcap. Thus, netsniff-ng then works multithreaded eventually.
netsniff-ng can also be used to debug netlink traffic.
OPTIONS
-i <dev|pcap|->, -d <dev|pcap|->, --in <dev|pcap|->, --dev <dev|pcap|->
Defines an input device. This can either be a networking device, a pcap file or stdin ("-"). In case of a pcap file, the pcap type ("-D"
option) is determined automatically by the pcap file magic. In case of stdin, it is assumed that the input stream is a pcap file.
-o <dev|pcap|dir|cfg|->, --out <dev|pcap|dir|cfg|->
Defines the output device. This can either be a networking device, a pcap file, a folder, a trafgen(8) configuration file or stdout ("-").
In the case of a pcap file that should not have the default pcap type (0xa1b2c3d4), the additional option "-T" must be provided. If a
directory is given, then, instead of a single pcap file, multiple pcap files are generated with rotation based on maximum file size or a
given interval ("-F" option). A trafgen configuration file can currently only be specified if the input device is a pcap file. If stdout is
given as a device, then a trafgen configuration will be written to stdout if the input device is a pcap file, or a pcap file if the input
device is a networking device.
-f, --filter <bpf-file|expr>
Specifies to not dump all traffic, but to filter the network packet haystack. As a filter, either a bpfc(8) compiled file can be passed as
a parameter or a tcpdump(1)-like filter expression in quotes. For details regarding the bpf-file have a look at bpfc(8), for details
regarding a tcpdump(1)-like filter have a look at section "filter example" or at pcap-filter(7). A filter expression may also be passed to
netsniff-ng without option "-f" in case there is no subsequent option following after the command-line filter expression.
-t, --type <type>
This defines some sort of filtering mechanisms in terms of addressing. Possible values for type are "host" (to us), "broadcast" (to all),
"multicast" (to group), "others" (promiscuous mode) or "outgoing" (from us).
-F, --interval <size|time>
If the output device is a folder, with "-F", it is possible to define the pcap file rotation interval either in terms of size or time.
Thus, when the interval limit has been reached, a new pcap file will be started. As size parameter, the following values are accepted
"<num>KiB/MiB/GiB"; As time parameter, it can be "<num>s/sec/min/hrs".
-J, --jumbo-support
By default, in pcap replay or redirect mode, netsniff-ng's ring buffer frames are a fixed size of 2048 bytes. This means that if you are
expecting jumbo frames or even super jumbo frames to pass through your network, then you need to enable support for that by using this
option. However, this has the disadvantage of performance degradation and a bigger memory footprint for the ring buffer. Note that this
doesn't affect (pcap) capturing mode, since tpacket in version 3 is used!
-R, --rfraw
In case the input or output networking device is a wireless device, it is possible with netsniff-ng to turn this into monitor mode and cre-
ate a mon<X> device that netsniff-ng will be listening on instead of wlan<X>, for instance. This enables netsniff-ng to analyze, dump, or
even replay raw 802.11 frames.
-n <0|uint>, --num <0|uint>
Process a number of packets and then exit. If the number of packets is 0, then this is equivalent to infinite packets resp. processing
until interrupted. Otherwise, a number given as an unsigned integer will limit processing.
-P <name>, --prefix <name>
When dumping pcap files into a folder, a file name prefix can be defined with this option. If not otherwise specified, the default prefix
is "dump-" followed by a Unix timestamp. Use "--prefex """ to set filename as seconds since the Unix Epoch e.g. 1369179203.pcap
-T <pcap-magic>, --magic <pcap-magic>
Specify a pcap type for storage. Different pcap types with their various meta data capabilities are shown with option "-D". If not other-
wise specified, the pcap-magic 0xa1b2c3d4, also known as a standard tcpdump-capable pcap format, is used. Pcap files with swapped endian-
ness are also supported.
-D, --dump-pcap-types
Dump all available pcap types with their capabilities and magic numbers that can be used with option "-T" to stdout and exit.
-B, --dump-bpf
If a Berkeley Packet Filter is given, for example via option "-f", then dump the BPF disassembly to stdout during ring setup. This only
serves for informative or verification purposes.
-r, --rand
If the input and output device are both networking devices, then this option will randomize packet order in the output ring buffer.
-M, --no-promisc
The networking interface will not be put into promiscuous mode. By default, promiscuous mode is turned on.
-A, --no-sock-mem
On startup and shutdown, netsniff-ng tries to increase socket read and write buffers if appropriate. This option will prevent netsniff-ng
from doing so.
-m, --mmap
Use mmap(2) as pcap file I/O. This is the default when replaying pcap files.
-G, --sg
Use scatter-gather as pcap file I/O. This is the default when capturing pcap files.
-c, --clrw
Use slower read(2) and write(2) I/O. This is not the default case anywhere, but in some situations it could be preferred as it has a lower
latency on write-back to disc.
-S <size>, --ring-size <size>
Manually define the RX_RING resp. TX_RING size in "<num>KiB/MiB/GiB". By default, the size is determined based on the network connectivity
rate.
-k <uint>, --kernel-pull <uint>
Manually define the interval in micro-seconds where the kernel should be triggered to batch process the ring buffer frames. By default, it
is every 10us, but it can manually be prolonged, for instance.
-b <cpu>, --bind-cpu <cpu>
Pin netsniff-ng to a specific CPU and also pin resp. migrate the NIC's IRQ CPU affinity to this CPU. This option should be preferred in
combination with "-s" in case a middle to high packet rate is expected.
-u <uid>, --user <uid> resp. -g <gid>, --group <gid>
After ring setup drop privileges to a non-root user/group combination.
-H, --prio-high
Set this process as a high priority process in order to achieve a higher scheduling rate resp. CPU time. This is however not the default
setting, since it could lead to starvation of other processes, for example low priority kernel threads.
-Q, --notouch-irq
Do not reassign the NIC's IRQ CPU affinity settings.
-s, --silent
Do not enter the packet dissector at all and do not print any packet information to the terminal. Just shut up and be silent. This option
should be preferred in combination with pcap recording or replay, since it will not flood your terminal which causes a significant perfor-
mance degradation.
-q, --less
Print a less verbose one-line information for each packet to the terminal.
-X, --hex
Only dump packets in hex format to the terminal.
-l, --ascii
Only display ASCII printable characters.
-U, --update
If geographical IP location is used, the built-in database update mechanism will be invoked to get Maxmind's latest database. To configure
search locations for databases, the file /etc/netsniff-ng/geoip.conf contains possible addresses. Thus, to save bandwidth or for mirroring
of Maxmind's databases (to bypass their traffic limit policy), different hosts or IP addresses can be placed into geoip.conf, separated by
a newline.
-V, --verbose
Be more verbose during startup i.e. show detailed ring setup information.
-v, --version
Show version information and exit.
-h, --help
Show user help and exit.
USAGE EXAMPLE
netsniff-ng
The most simple command is to just run "netsniff-ng". This will start listening on all available networking devices in promiscuous mode and
dump the packet dissector output to the terminal. No files will be recorded.
netsniff-ng --in eth0 --out dump.pcap -s -T 0xa1e2cb12 -b 0 tcp or udp
Capture TCP or UDP traffic from the networking device eth0 into the pcap file named dump.pcap, which has netsniff-ng specific pcap exten-
sions (see "netsniff-ng -D" for capabilities). Also, do not print the content to the terminal and pin the process and NIC IRQ affinity to
CPU 0. The pcap write method is scatter-gather I/O.
netsniff-ng --in wlan0 --rfraw --out dump.pcap --silent --bind-cpu 0
Put the wlan0 device into monitoring mode and capture all raw 802.11 frames into the file dump.pcap. Do not dissect and print the content
to the terminal and pin the process and NIC IRQ affinity to CPU 0. The pcap write method is scatter-gather I/O.
netsniff-ng --in dump.pcap --mmap --out eth0 -k1000 --silent --bind-cpu 0
Replay the pcap file dump.pcap which is read through mmap(2) I/O and send the packets out via the eth0 networking device. Do not dissect
and print the content to the terminal and pin the process and NIC IRQ affinity to CPU 0. Also, trigger the kernel every 1000us to traverse
the TX_RING instead of every 10us. Note that the pcap magic type is detected automatically from the pcap file header.
netsniff-ng --in eth0 --out eth1 --silent --bind-cpu 0 --type host -r
Redirect network traffic from the networking device eth0 to eth1 for traffic that is destined for our host, thus ignore broadcast, multi-
cast and promiscuous traffic. Randomize the order of packets for the outgoing device and do not print any packet contents to the terminal.
Also, pin the process and NIC IRQ affinity to CPU 0.
netsniff-ng --in team0 --out /opt/probe/ -s -m --interval 100MiB -b 0
Capture on an aggregated team0 networking device and dump packets into multiple pcap files that are split into 100MiB each. Use mmap(2) I/O
as a pcap write method, support for super jumbo frames is built-in (does not need to be configured here), and do not print the captured
data to the terminal. Pin netsniff-ng and NIC IRQ affinity to CPU 0. The default pcap magic type is 0xa1b2c3d4 (tcpdump-capable pcap).
netsniff-ng --in vlan0 --out dump.pcap -c -u `id -u bob` -g `id -g bob`
Capture network traffic on device wlan0 into a pcap file called dump.pcap by using normal read(2), write(2) I/O for the pcap file (slower
but less latency). Also, after setting up the RX_RING for capture, drop privileges from root to the user and group "bob". Invoke the packet
dissector and print packet contents to the terminal for further analysis.
netsniff-ng --in any --filter http.bpf -B --ascii -V
Capture from all available networking interfaces and install a low-level filter that was previously compiled by bpfc(8) into http.bpf in
order to filter HTTP traffic. Super jumbo frame support is automatically enabled and only print human readable packet data to the terminal,
and also be more verbose during setup phase. Moreover, dump a BPF disassembly of http.bpf.
netsniff-ng --in dump.pcap --out dump.cfg --silent
Convert the pcap file dump.pcap into a trafgen(8) configuration file dump.cfg. Do not print pcap contents to the terminal.
netsniff-ng -i dump.pcap -f beacon.bpf -o -
Convert the pcap file dump.pcap into a trafgen(8) configuration file and write it to stdout. However, do not dump all of its content, but
only the one that passes the low-level filter for raw 802.11 from beacon.bpf. The BPF engine here is invoked in user space inside of net-
sniff-ng, so Linux extensions are not available.
cat foo.pcap | netsniff-ng -i - -o -
Read a pcap file from stdin and convert it into a trafgen(8) configuration file to stdout.
modprobe nlmon
ip link add type nlmon
ip link set nlmon0 up
netsniff-ng -i nlmon0 -o dump.pcap -s
ip link set nlmon0 down
ip link del dev nlmon0
rmmod nlmon
In this example, netlink traffic is being captured. If not already done, a netlink monitoring device needs to be set up before it can be
used to capture netlink socket buffers (iproute2's ip(1) commands are given for nlmon device setup and teardown). netsniff-ng can then make
use of the nlmon device as an input device. In this example a pcap file with netlink traffic is being recorded.
CONFIG FILES
Files under /etc/netsniff-ng/ can be modified to extend netsniff-ng's functionality:
* oui.conf - OUI/MAC vendor database
* ether.conf - Ethernet type descriptions
* tcp.conf - TCP port/services map
* udp.conf - UDP port/services map
* geoip.conf - GeoIP database mirrors
FILTER EXAMPLE
netsniff-ng supports both, low-level and high-level filters that are attached to its packet(7) socket. Low-level filters are described in
the bpfc(8) man page.
Low-level filters can be used with netsniff-ng in the following way:
1. bpfc foo > bar
2. netsniff-ng -f bar
Here, foo is the bpfc program that will be translated into a netsniff-ng readable "opcodes" file and passed to netsniff-ng through the -f
option.
Similarly, high-level filter can be either passed through the -f option, e.g. -f "tcp or udp" or at the end of all options without the
"-f".
The filter syntax is the same as in tcpdump(8), which is described in the man page pcap-filter(7). Just to quote some examples from pcap-
filter(7):
host sundown
To select all packets arriving at or departing from sundown.
host helios and hot or ace
To select traffic between helios and either hot or ace.
ip host ace and not helios
To select all IP packets between ace and any host except helios.
net ucb-ether
To select all traffic between local hosts and hosts at Berkeley.
gateway snup and (port ftp or ftp-data)
To select all FTP traffic through Internet gateway snup.
ip and not net localnet
To select traffic neither sourced from, nor destined for, local hosts. If you have a gateway to another network, this traffic should never
make it onto your local network.
tcp[tcpflags] & (tcp-syn|tcp-fin) != 0 and not src and dst net localnet
To select the start and end packets (the SYN and FIN packets) of each TCP conversation that involve a non-local host.
tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)
To select all IPv4 HTTP packets to and from port 80, that is to say, print only packets that contain data, not, for example, SYN and FIN
packets and ACK-only packets. (IPv6 is left as an exercise for the reader.)
gateway snup and ip[2:2] > 576
To select IP packets longer than 576 bytes sent through gateway snup.
ether[0] & 1 = 0 and ip[16] >= 224
To select IP broadcast or multicast packets that were not sent via Ethernet broadcast or multicast.
icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply
To select all ICMP packets that are not echo requests or replies (that is to say, not "ping" packets).
PCAP FORMATS
:
netsniff-ng supports a couple of pcap formats, visible through ``netsniff-ng -D'':
tcpdump-capable pcap (default)
Pcap magic number is encoded as 0xa1b2c3d4 resp. 0xd4c3b2a1. As packet meta data this format contains the timeval in microseconds, the
original packet length and the captured packet length.
tcpdump-capable pcap with ns resolution
Pcap magic number is encoded as 0xa1b23c4d resp. 0x4d3cb2a1. As packet meta data this format contains the timeval in nanoseconds, the orig-
inal packet length and the captured packet length.
Alexey Kuznetzov's pcap
Pcap magic number is encoded as 0xa1b2cd34 resp. 0x34cdb2a1. As packet meta data this format contains the timeval in microseconds, the
original packet length, the captured packet length, the interface index (sll_ifindex), the packet's protocol (sll_protocol), and the packet
type (sll_pkttype).
netsniff-ng pcap
Pcap magic number is encoded as 0xa1e2cb12 resp. 0x12cbe2a1. As packet meta data this format contains the timeval in nanoseconds, the orig-
inal packet length, the captured packet length, the timestamp hw/sw source, the interface index (sll_ifindex), the packet's protocol
(sll_protocol), the packet type (sll_pkttype) and the hardware type (sll_hatype).
For further implementation details or format support in your application, have a look at pcap_io.h.
NOTE
For introducing bit errors, delays with random variation and more while replaying pcaps, make use of tc(8) with its disciplines such as
netem.
netsniff-ng does only some basic, architecture generic tuning on startup. If you are considering to do high performance capturing, you need
to carefully tune your machine, both hardware and software. Simply letting netsniff-ng run without thinking about your underlying system
might not necessarily give you the desired performance. Note that tuning your system is always a tradeoff and fine-grained balancing act
(throughput versus latency). You should know what you are doing!
One recommendation for software-based tuning is tuned(8). Besides that, there are many other things to consider. Just to throw you a few
things that you might want to look at: NAPI networking drivers, tickless kernel, I/OAT DMA engine, Direct Cache Access, RAM-based file sys-
tems, multi-queues, and many more things. Also, you might want to read the kernel's Documentation/networking/scaling.txt file regarding
technologies such as RSS, RPS, RFS, aRFS and XPS. Also check your ethtool(8) settings, for example regarding offloading or Ethernet pause
frames.
Moreover, to get a deeper understanding of netsniff-ng internals and how it interacts with the Linux kernel, the kernel documentation under
Documentation/networking/{packet_mmap.txt, filter.txt, multiqueue.txt} might be of interest.
How do you sniff in a switched environment? I rudely refer to dSniff's documentation that says:
The easiest route is simply to impersonate the local gateway, stealing client traffic en route to some remote destination. Of course, the
traffic must be forwarded by your attacking machine, either by enabling kernel IP forwarding or with a userland program that accomplishes
the same (fragrouter -B1).
Several people have reportedly destroyed connectivity on their LAN to the outside world by ARP spoofing the gateway, and forgetting to
enable IP forwarding on the attacking machine. Do not do this. You have been warned.
A safer option than ARP spoofing would be to use a "port mirror" function if your switch hardware supports it and if you have access to the
switch.
If you do not need to dump all possible traffic, you have to consider running netsniff-ng with a BPF filter for the ingress path. For that
purpose, read the bpfc(8) man page.
Also, to aggregate multiple NICs that you want to capture on, you should consider using team devices, further explained in libteam resp.
teamd(8).
The following netsniff-ng pcap magic numbers are compatible with other tools, at least tcpdump or Wireshark:
0xa1b2c3d4 (tcpdump-capable pcap)
0xa1b23c4d (tcpdump-capable pcap with ns resolution)
0xa1b2cd34 (Alexey Kuznetzov's pcap)
Pcap files with different meta data endianness are supported by netsniff-ng as well.
BUGS
When replaying pcap files, the timing information from the pcap packet header is currently ignored.
Also, when replaying pcap files, demultiplexing traffic among multiple networking interfaces does not work. Currently, it is only sent via
the interface that is given by the --out parameter.
When performing traffic capture on the Ethernet interface, the pcap file is created and packets are received but without a 802.1Q header.
When one uses tshark, all headers are visible, but netsniff-ng removes 802.1Q headers. Is that normal behavior?
Yes and no. The way VLAN headers are handled in PF_PACKET sockets by the kernel is somewhat "problematic" [1]. The problem in the Linux
kernel is that some drivers already handle VLANs, others do not. Those who handle it can have different implementations, such as hardware
acceleration and so on. So in some cases the VLAN tag is even stripped before entering the protocol stack, in some cases probably not. The
bottom line is that a "hack" was introduced in PF_PACKET so that a VLAN ID is visible in some helper data structure that is accessible from
the RX_RING.
Then it gets really messy in the user space to artificially put the VLAN header back into the right place. Not to mention the resulting
performance implications on all of libpcap(3) tools since parts of the packet need to be copied for reassembly via memmove(3).
A user reported the following, just to demonstrate this mess: some tests were made with two machines, and it seems that results depend on
the driver ...
AR8131:
ethtool -k eth0 gives "rx-vlan-offload: on"
- wireshark gets the vlan header
- netsniff-ng doesn't get the vlan header
ethtool -K eth0 rxvlan off
- wireshark gets a QinQ header even though noone sent QinQ
- netsniff-ng gets the vlan header
RTL8111/8168B:
ethtool -k eth0 gives "rx-vlan-offload: on"
- wireshark gets the vlan header
- netsniff-ng doesn't get the vlan header
ethtool -K eth0 rxvlan off
- wireshark gets the vlan header
- netsniff-ng doesn't get the vlan header
Even if we agreed on doing the same workaround as libpcap, we still will not be able to see QinQ, for instance, due to the fact that only
one VLAN tag is stored in the kernel helper data structure. We think that there should be a good consensus on the kernel space side about
what gets transferred to userland first.
Update (28.11.2012): the Linux kernel and also bpfc(8) has built-in support for hardware accelerated VLAN filtering, even though tags might
not be visible in the payload itself as reported here. However, the filtering for VLANs works reliable if your NIC supports it. See bpfc(8)
for an example.
[1] http://lkml.indiana.edu/hypermail/linux/kernel/0710.3/3816.html
LEGAL
netsniff-ng is licensed under the GNU GPL version 2.0.
HISTORY
netsniff-ng was originally written for the netsniff-ng toolkit by Daniel Borkmann. Bigger contributions were made by Emmanuel Roullit,
Markus Amend, Tobias Klauser and Christoph Jaeger. It is currently maintained by Tobias Klauser <tklauser@distanz.ch> and Daniel Borkmann
<dborkma@tik.ee.ethz.ch>.
SEE ALSO
trafgen(8), mausezahn(8), ifpps(8), bpfc(8), flowtop(8), astraceroute(8), curvetun(8)
AUTHOR
Manpage was written by Daniel Borkmann.
COLOPHON
This page is part of the Linux netsniff-ng toolkit project. A description of the project, and information about reporting bugs, can be
found at http://netsniff-ng.org/.
Linux 03 March 2013 NETSNIFF-NG(8)