mask tcp[tcpflags] with 0x0fff to provide tcp flags only

rscheff · rscheff · commit 70da6682b48f · 2023-09-05T10:18:51.000+02:00
diff --git a/grammar.y.in b/grammar.y.in
@@ -856,7 +856,10 @@ arth:	  pnum			{ CHECK_PTR_VAL(($$ = gen_loadi(cstate, $1))); }
 	;
 tcpflags: TCPFLAGS
 	;
-narth:	  pname '[' tcpflags ']'	{ CHECK_PTR_VAL(($$ = gen_load(cstate, $1, gen_loadi(cstate, 12), 2))); }
+narth:	  pname '[' tcpflags ']'	{ CHECK_PTR_VAL(($$ =
+						gen_arth(cstate, BPF_AND,
+						    gen_load(cstate, $1, gen_loadi(cstate, 12), 2),
+						    gen_loadi(cstate, 0x0FFF)))); }
 	| pname '[' arth ']'		{ CHECK_PTR_VAL(($$ = gen_load(cstate, $1, $3, 1))); }
 	| pname '[' arth ':' NUM ']'	{ CHECK_PTR_VAL(($$ = gen_load(cstate, $1, $3, $5))); }
 	| arth '+' arth			{ CHECK_PTR_VAL(($$ = gen_arth(cstate, BPF_ADD, $1, $3))); }

Original file line number	Diff line number	Diff line change
`@@ -856,7 +856,10 @@ arth: pnum { CHECK_PTR_VAL(($$ = gen_loadi(cstate, $1))); }`
`856`	`856`	`;`
`857`	`857`	`tcpflags: TCPFLAGS`
`858`	`858`	`;`
`859`		`-narth: pname '[' tcpflags ']' { CHECK_PTR_VAL(($$ = gen_load(cstate, $1, gen_loadi(cstate, 12), 2))); }`
	`859`	`+narth: pname '[' tcpflags ']' { CHECK_PTR_VAL(($$ =`
	`860`	`+ gen_arth(cstate, BPF_AND,`
	`861`	`+ gen_load(cstate, $1, gen_loadi(cstate, 12), 2),`
	`862`	`+ gen_loadi(cstate, 0x0FFF)))); }`
`860`	`863`	`\| pname '[' arth ']' { CHECK_PTR_VAL(($$ = gen_load(cstate, $1, $3, 1))); }`
`861`	`864`	`\| pname '[' arth ':' NUM ']' { CHECK_PTR_VAL(($$ = gen_load(cstate, $1, $3, $5))); }`
`862`	`865`	`\| arth '+' arth { CHECK_PTR_VAL(($$ = gen_arth(cstate, BPF_ADD, $1, $3))); }`