Subject: Re: [PATCH] Generalize socket rx gap / receive queue overflow cmsg (v3)

From: Eric Dumazet <[email-masked]>
Date: Sat, 10 Oct 2009 07:12:10 +0200

Neil Horman a écrit :
> Ok, take 3 with Erics new notes
> 
> Change Notes:
> 
> 1) Modified inlining of sock_recv_ts_and_drops to be more efficient
> 
> 2) modify getsockopt for SO_RXQ_OVFL to gurantee only a 1 or 0 return
> 
> =============================================================
> 
> 
> Create a new socket level option to report number of queue overflows
> 
> Recently I augmented the AF_PACKET protocol to report the number of frames lost
> on the socket receive queue between any two enqueued frames.  This value was
> exported via a SOL_PACKET level cmsg.  AFter I completed that work it was
> requested that this feature be generalized so that any datagram oriented socket
> could make use of this option.  As such I've created this patch, It creates a
> new SOL_SOCKET level option called SO_RXQ_OVFL, which when enabled exports a
> SOL_SOCKET level cmsg that reports the nubmer of times the sk_receive_queue
> overflowed between any two given frames.  It also augments the AF_PACKET
> protocol to take advantage of this new feature (as it previously did not touch
> sk->sk_drops, which this patch uses to record the overflow count).  Tested
> successfully by me.
> 
> Notes:

> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -951,7 +951,7 @@ try_again:
>  		UDP_INC_STATS_USER(sock_net(sk),
>  				UDP_MIB_INDATAGRAMS, is_udplite);
>  
> -	sock_recv_timestamp(msg, sk, skb);
> +	sock_recv_ts_and_drops(msg, sk, skb);
>  
>  	/* Copy the address. */
>  	if (sin) {

As a followup to my patch about udp_poll(), I realize we dont atomic_inc(&sk->sk_drops)
in the event a packet is dropped because of a bad checksum.

I'll post a fixup once David reviewed previous patch