bad file descriptor

[pmazzini]

I've been seeing bad file descriptor error message sometimes when trying to read an incoming packet.

Problem:

• The responder creates a net.UDPConn via net.ListenUDP
• Afterwards, it calls connFd to get a file descriptor which uses the File method of the net.UDPConn.
• The File method creates a duplicate:

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished.

• The Close method is never explicitly called and the GC takes care of it
• This leads to the mentioned error message, trying to read from a closed fd

Solution:

There are at least 2 alternatives and I wanted to ask for opinions.

• Avoid creating a duplicate fd to read packets: This implies not using net.ListenUDP, (which doesn't expose the "original" fd) and using a syscall directly to create the listening socket.

• Explicitly close the duplicate file descriptor to avoid the GC closing it for us at an undesired time: This implies removing/modifying the connFd function.

Any other alternatives? Thoughts?

[leoleovich]

Explicitly close please ;)