Re: [PATCH net 1/3] unix/dgram: peek beyond 0-sized skbs

From: Eric Dumazet
Date: Thu Apr 25 2013 - 14:49:05 EST

On Thu, 2013-04-25 at 09:47 -0400, Benjamin Poirier wrote:
> "77c1090 net: fix infinite loop in __skb_recv_datagram()" (v3.8) introduced a
> regression:
> After that commit, recv can no longer peek beyond a 0-sized skb in the queue.
> __skb_recv_datagram() instead stops at the first skb with len == 0 and results
> in the system call failing with -EFAULT via skb_copy_datagram_iovec().

if MSG_PEEK is not used, what happens here ?

It doesn't look right to me that we return -EFAULT if skb->len is 0,
EFAULT is reserved to faulting (ie reading/writing at least one byte)

How are we telling the user message had 0 byte, but its not EOF ?

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