CODEWITHSUNDEEP
javacsocketsnetwork-programmingudp
MinecraftShamrock
MinecraftShamrock

Reputation: 3574

Does Java's UDP API only receive packets with correct checksum?

I am new to UDP and Java's UDP API and I know that packets might arrive corrupted, splitted by IP or wrong in any other way. Of course, if such a packet arrives splitted, the checksum in the UDP header won't be right.

When reading a UDP packet in Java like DatagramSocket.receive(DatagramPacket), is it guaranteed, that the content of the received packet is correct (meaning that the calculated checksum is right)? Or will Java also pass corrupted UDP packets to the application?

Upvotes: 2

Views: 916

Answers (2)

Erik
Erik

Reputation: 4563

From IETF RFC 5405 section 3.4, I quote:

[...] application developers SHOULD implement additional checks where data integrity is important [...]

Now, how important data integrity is to your application and how you value the 'SHOULD' in capital letters, that's up to you.

In other words:

  • By definition UDP packet data integrity is guaranteed.
  • By specification UDP packet data integrity is not guaranteed in the application layer.

Therefore, by implementation in the network layer the integrity of received UDP packet data remains unclear in the application layer.

Upvotes: 0

snovelli
snovelli

Reputation: 6058

Short answer:

Yes, unless configured otherwise.

Long answer:

Udp packets includes CHECKSUM that is used by your OS is verifying the packets for you. When a packet with the wrong checksum is received is discarded by the OS stack (before reaching the application layer).

I've never tried it but in Ubuntu is possible to disable the checksum with 

ethtool --offload eth0 rx off

Upvotes: 1

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