Re: [PATCH nft 5/7] src: implement shortcut for tcp mss size mangling

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Sun, Aug 20, 2017 at 01:14:11AM +0200, Florian Westphal wrote:
> short-hand version of tcp option maxseg size 1:
> tcp option mss set 1
> 
> Reverse also prints the more compact representation.

Why not just keep with the shortcut (more compact) representation?

> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
>  src/exthdr.c       |  1 +
>  src/parser_bison.y |  7 +++++++
>  src/scanner.l      |  1 +
>  src/tcpopt.c       | 11 +++++++++--
>  4 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/src/exthdr.c b/src/exthdr.c
> index 7d13c83c9943..a4d4fa5b0864 100644
> --- a/src/exthdr.c
> +++ b/src/exthdr.c
> @@ -20,6 +20,7 @@
>  
>  #include <utils.h>
>  #include <headers.h>
> +#include <tcpopt.h>
>  #include <expression.h>
>  #include <statement.h>
>  
> diff --git a/src/parser_bison.y b/src/parser_bison.y
> index 7898ea3fe7bc..533347264729 100644
> --- a/src/parser_bison.y
> +++ b/src/parser_bison.y
> @@ -334,6 +334,7 @@ static void location_update(struct location *loc, struct location *rhs, int n)
>  %token RIGHT			"right"
>  %token TSVAL			"tsval"
>  %token TSECR			"tsecr"
> +%token MSS			"mss"
>  
>  %token DCCP			"dccp"
>  
> @@ -3214,6 +3215,12 @@ payload_stmt		:	payload_expr		SET	expr
>  				else
>  					$$ = payload_stmt_alloc(&@$, $1, $3);
>  			}
> +			|	TCP	OPTION	MSS	SET	expr
> +			{
> +				$$ = exthdr_stmt_alloc(&@$,
> +							tcpopt_expr_alloc(&@$, TCPOPTHDR_MAXSEG, TCPOPTHDR_FIELD_SIZE),
> +							$5);
> +			}
>  			;
>  
>  payload_expr		:	payload_raw_expr
> diff --git a/src/scanner.l b/src/scanner.l
> index b6ba32d88f4a..ede6ed73e5df 100644
> --- a/src/scanner.l
> +++ b/src/scanner.l
> @@ -433,6 +433,7 @@ addrstring	({macaddr}|{ip4addr}|{ip6addr})
>  "window"		{ return WINDOW; }
>  "urgptr"		{ return URGPTR; }
>  "option"		{ return OPTION; }
> +"mss"			{ return MSS; }
>  
>  "dccp"			{ return DCCP; }
>  
> diff --git a/src/tcpopt.c b/src/tcpopt.c
> index 63f0c236c9cf..c0540b7a31b2 100644
> --- a/src/tcpopt.c
> +++ b/src/tcpopt.c
> @@ -249,8 +249,15 @@ void tcpopt_expr_print(const struct expr *expr, struct output_ctx *octx)
>  
>  void tcpopt_stmt_print(const struct stmt *stmt, struct output_ctx *octx)
>  {
> -	tcpopt_expr_print(stmt->exthdr.expr, octx);
> -	printf(" set ");
> +	if (stmt->exthdr.expr->exthdr.desc->type == TCPOPT_MAXSEG &&
> +	    stmt->exthdr.expr->exthdr.tmpl ==
> +	    &stmt->exthdr.expr->exthdr.desc->templates[TCPOPTHDR_FIELD_SIZE]) {
> +		printf("tcp option mss set ");
> +	} else {
> +		tcpopt_expr_print(stmt->exthdr.expr, octx);
> +		printf(" set ");
> +	}
> +
>  	expr_print(stmt->exthdr.val, octx);
>  }
>  
> -- 
> 2.13.0
> 
> --
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