Re: [PATCH nf 1/2] netfilter: conntrack: move synack init code to helper

[Jozsef Kadlecsik <kadlec@netfilter.org>]

On Sat, 29 Jan 2022, Florian Westphal wrote:

> It seems more readable to use a common helper in the followup fix rather
> than copypaste or goto.
> 
> No functional change intended.  The function is only called for syn-ack
> or syn in repy direction in case of simultaneous open.
> 
> Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
> Signed-off-by: Florian Westphal <fw@strlen.de>

Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>

> ---
>  net/netfilter/nf_conntrack_proto_tcp.c | 47 ++++++++++++++++----------
>  1 file changed, 29 insertions(+), 18 deletions(-)
> 
> diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
> index af5115e127cf..88c89e97d8a2 100644
> --- a/net/netfilter/nf_conntrack_proto_tcp.c
> +++ b/net/netfilter/nf_conntrack_proto_tcp.c
> @@ -446,6 +446,32 @@ static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
>  	}
>  }
>  
> +static void tcp_init_sender(struct ip_ct_tcp_state *sender,
> +			    struct ip_ct_tcp_state *receiver,
> +			    const struct sk_buff *skb,
> +			    unsigned int dataoff,
> +			    const struct tcphdr *tcph,
> +			    u32 end, u32 win)
> +{
> +	/* SYN-ACK in reply to a SYN
> +	 * or SYN from reply direction in simultaneous open.
> +	 */
> +	sender->td_end =
> +	sender->td_maxend = end;
> +	sender->td_maxwin = (win == 0 ? 1 : win);
> +
> +	tcp_options(skb, dataoff, tcph, sender);
> +	/* RFC 1323:
> +	 * Both sides must send the Window Scale option
> +	 * to enable window scaling in either direction.
> +	 */
> +	if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
> +	      receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE)) {
> +		sender->td_scale = 0;
> +		receiver->td_scale = 0;
> +	}
> +}
> +
>  static bool tcp_in_window(struct nf_conn *ct,
>  			  enum ip_conntrack_dir dir,
>  			  unsigned int index,
> @@ -499,24 +525,9 @@ static bool tcp_in_window(struct nf_conn *ct,
>  		 * Initialize sender data.
>  		 */
>  		if (tcph->syn) {
> -			/*
> -			 * SYN-ACK in reply to a SYN
> -			 * or SYN from reply direction in simultaneous open.
> -			 */
> -			sender->td_end =
> -			sender->td_maxend = end;
> -			sender->td_maxwin = (win == 0 ? 1 : win);
> -
> -			tcp_options(skb, dataoff, tcph, sender);
> -			/*
> -			 * RFC 1323:
> -			 * Both sides must send the Window Scale option
> -			 * to enable window scaling in either direction.
> -			 */
> -			if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
> -			      && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
> -				sender->td_scale =
> -				receiver->td_scale = 0;
> +			tcp_init_sender(sender, receiver,
> +					skb, dataoff, tcph,
> +					end, win);
>  			if (!tcph->ack)
>  				/* Simultaneous open */
>  				return true;
> -- 
> 2.34.1
> 
> 

-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.hu
PGP key : https://wigner.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics
          H-1525 Budapest 114, POB. 49, Hungary