Udp short packet
Protocol data unit (pdu) explained
The User Datagram Protocol (UDP) is a key member of the Internet protocol suite of computer networking. Computer applications may send messages, referred to as datagrams in this case, to other hosts on an Internet Protocol (IP) network using UDP. Setting up communication channels or data paths does not necessitate prior communication.
UDP utilizes a straightforward connectionless communication model with few protocol mechanisms. At the source and destination of the datagram, UDP provides checksums for data integrity and port numbers for addressing various functions. It lacks handshaking dialogues, exposing the user’s software to the underlying network’s unreliability; distribution, ordering, and duplicate protection are not guaranteed. If an application needs error-correction capabilities at the network interface level, it may use the Transmission Control Protocol (TCP) or the Stream Control Transmission Protocol (SCTP), which are both configured for this purpose.
UDP is ideal for applications where error checking and correction are either not required or performed in-app; UDP eliminates the overhead of such processing in the protocol stack. UDP is often used in time-critical applications because dropping packets is preferable to waiting for packets that have been delayed due to retransmission, which might not be possible in a real-time system. 1st
Top 10 wireshark filters
Unfortunately, I must confess that I, too, have experienced the same issue: about a month ago, shortly after an udp attack, the server’s network interface went down, and the server was unreachable at the time; the server had to be shut down and restarted.
Keep in mind that you just want to block traffic if a service is behind it! If there is nothing to block, you can end up with a very long iptable (ddos attack), which is inconvenient, particularly if you have several virtual machines running. Until now, there hasn’t been a cluster solution. 🙁
What is tcp/ip?
When the bad commit (2783ef2) was committed to Linux is what I’m having trouble finding out. TomatoUSB uses 2.6.22 with multiple updates, but the workaround is in 2.6.32 (not 2.6.34). I suppose I should search at the kernel source in TomatoUSB and see whether the saddr/daddr assignments have been transferred or not.
If the IP addresses involved appear to be correct**, the above commits aren’t applicable (meaning the kernel is so old that we’re not vulnerable to that issue — sometimes old is nice (or lucky)), and a clarification of what the message implies is required:
The message expresses that the UDP payload length (as specified in the UDP header) does not correspond to the payload length received (the payload is smaller than the length). This may be triggered by a number of reasons, but the most likely reason is that a router or computer somewhere (far away from you) is misbehaving. You should notify your VPN provider / endpoint about this, because they will need to do packet captures (as will you) to see what they’re sending vs. what you’re getting. It’s also probable that this data is being munged by a router somewhere on the Internet (it happens more often than you might think).
Linux telephony: not so short overview
a brief definition: The User Datagram Protocol (UDP) is a data-transfer protocol used on the Internet. UDP prioritizes speed over reliability, sending data packets to a destination without requiring a link. UDP is suitable for time-sensitive use cases like video streaming, Voice over Internet Protocol (VoIP), video gaming, and DNS lookups due to its low latency.
Unlike the most common protocol for transmitting data over the Internet, Transmission Control Protocol (TCP), UDP does not order data packets or create a direct connection between endpoints, such as an IoT security camera and a smartphone. Instead, the data is assured to reach its destination by the network devices that link those endpoints.
Data packets may arrive out of order or get lost in transmission while exchanging data over the Internet Protocol. TCP will request that missing data packets be retransmitted, as well as reorganize packets that arrive out of order. This improves precision but adds latency, and if individual packets of an audio or video file are lost, humans are often unable to detect errors. Retransmitting lost packets or reordering them until they arrive would just add to the real-time data stream’s intrusion.