netdev - Re: [PATCH net-next 2/3] tcp: add a helper for setting EOR on tail skb

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Date: Fri, 31 May 2024 09:41:30 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jakub Kicinski <kuba@...nel.org>, 
 edumazet@...gle.com, 
 pabeni@...hat.com
Cc: davem@...emloft.net, 
 netdev@...r.kernel.org, 
 mptcp@...ts.linux.dev, 
 matttbe@...nel.org, 
 martineau@...nel.org, 
 borisp@...dia.com, 
 willemdebruijn.kernel@...il.com, 
 Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net-next 2/3] tcp: add a helper for setting EOR on tail
 skb

Jakub Kicinski wrote:
> TLS (and hopefully soon PSP will) use EOR to prevent skbs
> with different decrypted state from getting merged, without
> adding new tests to the skb handling. In both cases once
> the connection switches to an "encrypted" state, all subsequent
> skbs will be encrypted, so a single "EOR fence" is sufficient
> to prevent mixing.
> 
> Add a helper for setting the EOR bit, to make this arrangement
> more explicit.
> 
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>

> ---
>  include/net/tcp.h    |  9 +++++++++
>  net/tls/tls_device.c | 11 ++---------
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 32741856da01..08c3b99501cf 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -1066,6 +1066,7 @@ static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
>  static inline bool tcp_skb_can_collapse(const struct sk_buff *to,
>  					const struct sk_buff *from)
>  {
> +	/* skb_cmp_decrypted() not needed, use tcp_write_collapse_fence() */
>  	return likely(tcp_skb_can_collapse_to(to) &&
>  		      mptcp_skb_can_collapse(to, from) &&
>  		      skb_pure_zcopy_same(to, from));
> @@ -2102,6 +2103,14 @@ static inline void tcp_rtx_queue_unlink_and_free(struct sk_buff *skb, struct soc
>  	tcp_wmem_free_skb(sk, skb);
>  }
>  
> +static inline void tcp_write_collapse_fence(struct sock *sk)
> +{

const struct ptr?

> +	struct sk_buff *skb = tcp_write_queue_tail(sk);
> +
> +	if (skb)
> +		TCP_SKB_CB(skb)->eor = 1;
> +}