I have a protocol that exactly follows ipv6 header format and is encapsulated in udp for transmission. Is there any way to make wireshark decode the udp data as an ip packet?
There's a protocol called "Teredo Tunneling" (which see) which encapsulates/tunnels IPV6 in UDP packets (using UDP port 3544).
If your capture is of a UDP conversation using UDP port 3544 on one end of the conversation, then Wireshark should automatically recognize the conversation as Teredo (i.e., IPV6 over UDP) and properly decode the IPV6 payload in the UDP data.
If your capture is using a different UDP port, do the following to specify that a particular UDP conversation is to be decoded as Teredo:
Right click on a UDP frame you wish to decode as Teredo.
Select "Decode As" in the right-click menu.
Select the "Transport" tab in the "Decode As" pop-up window.
Select Teredo in the right-hand "decode as" column.
Click "OK".
Related
As you can see in first figure, what does that Raw packet data mean? What is the difference between normal tcp packet in figure 2?
FYI, I'm using Wireshark 2.2.0.
Basically when you are capturing packets on an interface you have an associated link type to it (ethernet, 802.11, 802.15.4, etc).
Raw packet is used when you dont have any, the first bytes captured are directly the IPv6 or IPv4 header.
Raw IP; the packet begins with an IPv4 or IPv6 header, with the "version" field of the header indicating whether it's an IPv4 or IPv6 header.
From http://www.tcpdump.org/linktypes.html
where does the wireshark capture the packets in the linux kernel? If an output packet is captured by wireshark , will the packet be sent out definitely through corresponding interface?
In other words, could an output packet that captured by wireshark be dropped before it is sent out?
where does the wireshark capture the packets in the linux kernel?
On UN*Xes, it uses libpcap, which, on Linux, uses AF_PACKET sockets. (On Windows, it uses WinPcap, which is a driver plus a port of libpcap to use the driver.)
If an output packet is captured by wireshark , will the packet be sent out definitely through corresponding interface?
No. The networking stack hands the packet to the appropriate AF_PACKET sockets and to the driver; the driver might drop the packet (for example, if, on an Ethernet, it got multiple collisions and gave up) even though the packet was delivered to the AF_PACKET socket.
In other words, could an output packet that captured by wireshark be dropped before it is sent out?
Yes. See above.
I have a pcap file captured from a network. Now everytime I try to view the HTTP packets I place "http" in the filter. Is there a way where I can only save the HTTP filtered packets and not the lower level protocols included in the packet such as TCP, IP, Ethernet, Frames.
Try exporting rather than saving. There is an option there for exporting only selected packets.
So I have trouble finding a source that describes whether the TCP Packet is the payload of the IP Datagram or vice versa. I imagine the TCP Packet must be the payload because presumably the router can divide the IP Datagram therefore splitting up the TCP Packet and then the final router would have to reassamble them. Am I right?
If by "payload" you're referring to the data that comes after an IP header, then TCP is the "payload" of an IP packet when receiving data, since it's an upper level protocol.
The proper term for networking is actually encapsulation though.
It basically works by adding on progressive layers of protocols as information travels down from the application to the wire. After transmission, the packets are re-assembled and then the packets are error checked, the headers are stripped off, and what you are referring to as the "payload" becomes the next chunk of information that is checked. Once all of the outer protocol layers are stripped off the server/client has the information that directly corresponds to what the application sent.
Tcp\IP are two important proctocols. Tcp is connection oriented, while IP is a connection-less protocol. IP stands for a logical address, which works as packet address. The source packet has destination address for its destination. Tcp works with this logical address and helps the packets to reach their destinations, and provides acknowledgement when packet reached to its destination.
I am testing a network device driver's ability to cope with corrupted packets. The specific case I want to test is a when a large TCP packet is fragmented along the path because of smaller MTU in the way.
What most interests me about the IP Fragmentation of the large TCP packet is, is the protocol attribute of the IP Fragment packet set to TCP for each packet, or just the first fragment?
The protocol field will be set to TCP (6) for each fragment.
From RFC 791 - Internet Protocol
To fragment a long internet datagram,
an internet protocol module (for
example, in a gateway), creates two
new internet datagrams and copies the
contents of the internet header fields
from the long datagram into both new
internet headers. ... This procedure
can be generalized for an n-way split,
rather than the two-way split
described.
Protocol is part of the header and will consequently be copied into each of the fragments.
IP Fragmentation is a layer-3 activity, while the packet will be marked TCP, the intermediate fragments will not be usable by TCP. The TCP layer will have to wait for a re-assembly of the actual IP packet (unfragmented) before it can process it.
Wikipedia IP Fragmentation reference.
Path MTU-Discovery will usually update the source MTU and TCP packets (actually segments) will be sent with sizes limited to not cause fragmentation on the way