Subject: Re: [PATCH] Fix sorting of SACK blocks

From: Stephen Hemminger <[email-masked]>
Date: Thu, 25 Jan 2007 10:36:10 -0800

On Thu, 25 Jan 2007 20:29:03 +0200
Baruch Even <[email-masked]> wrote:

> The sorting of SACK blocks actually munges them rather than sort, causing the
> TCP stack to ignore some SACK information and breaking the assumption of
> ordered SACK blocks after sorting.
> 
> The sort takes the data from a second buffer which isn't moved causing
> subsequent data moves to occur from the wrong location. The fix is to
> use a temporary buffer as a normal sort does.
> 
> Signed-Off-By: Baruch Even <[email-masked]>
> 
> diff -X 2.6-rc6/Documentation/dontdiff -ur 2.6-rc6/net/ipv4/tcp_input.c 2.6-mod/net/ipv4/tcp_input.c
> --- 2.6-rc6/net/ipv4/tcp_input.c	2007-01-25 19:04:20.000000000 +0200
> +++ 2.6-mod/net/ipv4/tcp_input.c	2007-01-25 19:52:04.000000000 +0200
> @@ -1011,10 +1011,11 @@
>  			for (j = 0; j < i; j++){
>  				if (after(ntohl(sp[j].start_seq),
>  					  ntohl(sp[j+1].start_seq))){
> -					sp[j].start_seq = htonl(tp->recv_sack_cache[j+1].start_seq);
> -					sp[j].end_seq = htonl(tp->recv_sack_cache[j+1].end_seq);
> -					sp[j+1].start_seq = htonl(tp->recv_sack_cache[j].start_seq);
> -					sp[j+1].end_seq = htonl(tp->recv_sack_cache[j].end_seq);
> +					struct tcp_sack_block_wire tmp;
> +
> +					tmp = sp[j];
> +					sp[j] = sp[j+1];
> +					sp[j+1] = tmp;
>  				}
>  
>  			}

This looks okay, but is there a test case that can be run?

-- 
Stephen Hemminger <[email-masked]>