Subject: why are error messages suppressed if IP_RECVERR is not set?

From: Chris Friesen <[email-masked]>
Date: Mon, 25 Aug 2003 11:08:43 -0400

I'm tracking down an issue where we are sending udp packets and they are 
being dropped (I suspect) in the device queue.

In ip_build_xmit() we get the error code back saying that the packet was 
dropped, but unless IP_RECVERR is set, it seems that this error is 
hidden from userspace.

I notice that the man page says that sendto will never give an errno of 
ENOBUFS, but if you turn on IP_RECVERR this is exactly what will happen.

I guess I have two questions then: 1) why do we hide the fact that we've 
dropped the packet, and 2) why doesn't the man page talk about the 
IP_RECVERR option?

I'm using 2.4.18, if it matters.

Thanks,

Chris

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