Subject: Re: [PATCH] net: netem: fix skb length BUG_ON in __skb_to_sgvec

From: Eric Dumazet <[email-masked]>
Date: Tue, 26 Feb 2019 08:08:17 -0800

On 02/26/2019 07:59 AM, Stephen Hemminger wrote:
> 
> 
> Maybe the fix is to stop TSO fragment from overwriting by doing something like:
> 
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 730bc44dbad9..5fe91d0224f6 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -1856,7 +1856,7 @@ static int tso_fragment(struct sock *sk, enum tcp_queue tcp_queue,
>  	u8 flags;
>  
>  	/* All of a TSO frame must be composed of paged data.  */
> -	if (skb->len != skb->data_len)
> +	if (skb->len != skb->data_len || skb_cloned(skb))
>  		return tcp_fragment(sk, tcp_queue, skb, len, mss_now, gfp);
>  
>  	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
> 

tso_fragment() is only called with packets that were not yet transmit.