netdev - Re: [COMPAT]: non-cmsg data gets interpreted as cmsg data (sparc64)

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Message-ID: <20080418142509.GA8742@gerrit.erg.abdn.ac.uk>
Date:	Fri, 18 Apr 2008 15:25:09 +0100
From:	Gerrit Renker <gerrit@....abdn.ac.uk>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [COMPAT]: non-cmsg data gets interpreted as cmsg data (sparc64)

| > The following code segment works without problems on IA-32:
| > 
| > 	uint32_t prio = 10;
| > 	struct msghdr msg;
| > 
| > 	// fill in iov bits of msg
| > 	// ...
| > 	msg.msg_control	   = &prio;
| > 	msg.msg_controllen = sizeof prio;
| > 
| > 	if (sendmsg(sockfd, &msg, 0))
| > 		err(1, "sendmsg failed");
| 
| It works in non-compat situations only by accident.
| 
| You have to use proper CMSG encoding to send things into the kernel
| vis the msg_control area.
| 
Many thanks indeed. This has helped to revise an otherwise ugly approach
into something which now works beautifully well and without problems -
as predicted.

Really, thanks a lot,
Gerrit


The University of Aberdeen is a charity registered in Scotland, No SC013683.

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