src: revisit tcp options support

Rework syntax, add tokens so we can extend the grammar more easily.
This has triggered several syntax changes with regards to the original
patch, specifically:

	tcp option sack0 left 1

There is no space between sack and the block number anymore, no more
offset field, now they are a single field. Just like we do with rt, rt0
and rt2. This simplifies our grammar and that is good since it makes our
life easier when extending it later on to accomodate new features.

I have also renamed sack_permitted to sack-permitted. I couldn't find
any option using underscore so far, so let's keep it consistent with
what we have.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 58 insertions, 89 deletions

diff --git a/src/tcpopt.c b/src/tcpopt.c
index e6f92bc6..f8612141 100644
--- a/src/tcpopt.c
+++ b/src/tcpopt.c
@@ -12,48 +12,6 @@
 #include <expression.h>
 #include <tcpopt.h>
 
-/* We do not need to export these enums, because the tcpopts are parsed at
- * runtime and not by bison.
- */
-enum tcpopt_eol_hdr_fields {
-	TCPOPT_EOLHDR_KIND,
-};
-
-enum tcpopt_nop_hdr_fields {
-	TCPOPT_NOPHDR_KIND,
-};
-
-enum tcpopt_maxseg_hdr_fields {
-	TCPOPT_MAXSEGHDR_KIND,
-	TCPOPT_MAXSEGHDR_LENGTH,
-	TCPOPT_MAXSEGHDR_SIZE,
-};
-
-enum tcpopt_window_hdr_fields {
-	TCPOPT_WINDOWHDR_KIND,
-	TCPOPT_WINDOWHDR_LENGTH,
-	TCPOPT_WINDOWHDR_COUNT,
-};
-
-enum tcpopt_sack_permitted_hdr_fields {
-	TCPOPT_SACKPERMHDR_KIND,
-	TCPOPT_SACKPERMHDR_LENGTH,
-};
-
-enum tcpopt_sack_hdr_fields {
-	TCPOPT_SACKHDR_KIND,
-	TCPOPT_SACKHDR_LENGTH,
-	TCPOPT_SACKHDR_LEFT,
-	TCPOPT_SACKHDR_RIGHT,
-};
-
-enum tcpopt_timestamp_hdr_fields {
-	TCPOPT_TIMESTAMPSHDR_KIND,
-	TCPOPT_TIMESTAMPSHDR_LENGTH,
-	TCPOPT_TIMESTAMPSHDR_TSVAL,
-	TCPOPT_TIMESTAMPSHDR_TSECR,
-};
-
 static const struct proto_hdr_template tcpopt_unknown_template =
 	PROTO_HDR_TEMPLATE("unknown", &invalid_type, BYTEORDER_INVALID, 0, 0);
 
@@ -64,7 +22,7 @@ const struct exthdr_desc tcpopt_eol = {
 	.name		= "eol",
 	.type		= TCPOPT_EOL,
 	.templates	= {
-		[TCPOPT_EOLHDR_KIND]		= PHT("kind",  0,    8),
+		[TCPOPTHDR_FIELD_KIND]		= PHT("kind",  0,    8),
 	},
 };
 
@@ -72,7 +30,7 @@ const struct exthdr_desc tcpopt_nop = {
 	.name		= "noop",
 	.type		= TCPOPT_NOP,
 	.templates	= {
-		[TCPOPT_NOPHDR_KIND]		= PHT("kind",   0,   8),
+		[TCPOPTHDR_FIELD_KIND]		= PHT("kind",   0,   8),
 	},
 };
 
@@ -80,9 +38,9 @@ const struct exthdr_desc tcptopt_maxseg = {
 	.name		= "maxseg",
 	.type		= TCPOPT_MAXSEG,
 	.templates	= {
-		[TCPOPT_MAXSEGHDR_KIND]		= PHT("kind",   0,  8),
-		[TCPOPT_MAXSEGHDR_LENGTH]	= PHT("length", 8,  8),
-		[TCPOPT_MAXSEGHDR_SIZE]		= PHT("size",  16, 16),
+		[TCPOPTHDR_FIELD_KIND]		= PHT("kind",   0,  8),
+		[TCPOPTHDR_FIELD_LENGTH]	= PHT("length", 8,  8),
+		[TCPOPTHDR_FIELD_SIZE]		= PHT("size",  16, 16),
 	},
 };
 
@@ -90,18 +48,18 @@ const struct exthdr_desc tcpopt_window = {
 	.name		= "window",
 	.type		= TCPOPT_WINDOW,
 	.templates	= {
-		[TCPOPT_WINDOWHDR_KIND]		= PHT("kind",   0,  8),
-		[TCPOPT_WINDOWHDR_LENGTH]	= PHT("length", 8,  8),
-		[TCPOPT_WINDOWHDR_COUNT]	= PHT("count", 16,  8),
+		[TCPOPTHDR_FIELD_KIND]		= PHT("kind",   0,  8),
+		[TCPOPTHDR_FIELD_LENGTH]	= PHT("length", 8,  8),
+		[TCPOPTHDR_FIELD_COUNT]		= PHT("count", 16,  8),
 	},
 };
 
 const struct exthdr_desc tcpopt_sack_permitted = {
-	.name		= "sack_permitted",
+	.name		= "sack-permitted",
 	.type		= TCPOPT_SACK_PERMITTED,
 	.templates	= {
-		[TCPOPT_SACKPERMHDR_KIND]	= PHT("kind",   0, 8),
-		[TCPOPT_SACKPERMHDR_LENGTH]	= PHT("length", 8, 8),
+		[TCPOPTHDR_FIELD_KIND]		= PHT("kind",   0, 8),
+		[TCPOPTHDR_FIELD_LENGTH]	= PHT("length", 8, 8),
 	},
 };
 
@@ -109,10 +67,10 @@ const struct exthdr_desc tcpopt_sack = {
 	.name		= "sack",
 	.type		= TCPOPT_SACK,
 	.templates	= {
-		[TCPOPT_SACKHDR_KIND]		= PHT("kind",   0,   8),
-		[TCPOPT_SACKHDR_LENGTH]		= PHT("length", 8,   8),
-		[TCPOPT_SACKHDR_LEFT]		= PHT("left",  16,  32),
-		[TCPOPT_SACKHDR_RIGHT]		= PHT("right", 48,  32),
+		[TCPOPTHDR_FIELD_KIND]		= PHT("kind",   0,   8),
+		[TCPOPTHDR_FIELD_LENGTH]		= PHT("length", 8,   8),
+		[TCPOPTHDR_FIELD_LEFT]		= PHT("left",  16,  32),
+		[TCPOPTHDR_FIELD_RIGHT]		= PHT("right", 48,  32),
 	},
 };
 
@@ -120,10 +78,10 @@ const struct exthdr_desc tcpopt_timestamp = {
 	.name		= "timestamp",
 	.type		= TCPOPT_TIMESTAMP,
 	.templates	= {
-		[TCPOPT_TIMESTAMPSHDR_KIND]	= PHT("kind",   0,  8),
-		[TCPOPT_TIMESTAMPSHDR_LENGTH]	= PHT("length", 8,  8),
-		[TCPOPT_TIMESTAMPSHDR_TSVAL]	= PHT("tsval",  16, 32),
-		[TCPOPT_TIMESTAMPSHDR_TSECR]	= PHT("tsecr",  48, 32),
+		[TCPOPTHDR_FIELD_KIND]		= PHT("kind",   0,  8),
+		[TCPOPTHDR_FIELD_LENGTH]	= PHT("length", 8,  8),
+		[TCPOPTHDR_FIELD_TSVAL]		= PHT("tsval",  16, 32),
+		[TCPOPTHDR_FIELD_TSECR]		= PHT("tsecr",  48, 32),
 	},
 };
 #undef PHT
@@ -178,46 +136,57 @@ static unsigned int calc_offset_reverse(const struct exthdr_desc *desc,
 	}
 }
 
+static const struct exthdr_desc *tcpopthdr_protocols[] = {
+	[TCPOPTHDR_EOL]			= &tcpopt_eol,
+	[TCPOPTHDR_NOOP]		= &tcpopt_nop,
+	[TCPOPTHDR_MAXSEG]		= &tcptopt_maxseg,
+	[TCPOPTHDR_WINDOW]		= &tcpopt_window,
+	[TCPOPTHDR_SACK_PERMITTED]	= &tcpopt_sack_permitted,
+	[TCPOPTHDR_SACK0]		= &tcpopt_sack,
+	[TCPOPTHDR_SACK1]		= &tcpopt_sack,
+	[TCPOPTHDR_SACK2]		= &tcpopt_sack,
+	[TCPOPTHDR_SACK3]		= &tcpopt_sack,
+	[TCPOPTHDR_ECHO]		= TCPOPT_OBSOLETE,
+	[TCPOPTHDR_ECHO_REPLY]		= TCPOPT_OBSOLETE,
+	[TCPOPTHDR_TIMESTAMP]		= &tcpopt_timestamp,
+};
+
+static uint8_t tcpopt_optnum[] = {
+	[TCPOPTHDR_SACK0]	= 0,
+	[TCPOPTHDR_SACK1]	= 1,
+	[TCPOPTHDR_SACK2]	= 2,
+	[TCPOPTHDR_SACK3]	= 3,
+};
 
-struct expr *tcpopt_expr_alloc(const struct location *loc,
-			       const char *option_str,
-			       const unsigned int option_num,
-			       const char *option_field)
+static uint8_t tcpopt_find_optnum(uint8_t optnum)
 {
-	const struct proto_hdr_template *tmp, *tmpl = &tcpopt_unknown_template;
-	const struct exthdr_desc *desc = NULL;
-	struct expr *expr;
-	unsigned int i, j;
+	if (optnum > TCPOPTHDR_SACK3)
+		return 0;
 
-	for (i = 0; i < array_size(tcpopt_protocols); ++i) {
-		if (tcpopt_protocols[i] == TCPOPT_OBSOLETE)
-			continue;
+	return tcpopt_optnum[optnum];
+}
 
-		if (!tcpopt_protocols[i]->name ||
-		    strcmp(option_str, tcpopt_protocols[i]->name))
-			continue;
+struct expr *tcpopt_expr_alloc(const struct location *loc, uint8_t type,
+			       uint8_t field)
+{
+	const struct proto_hdr_template *tmpl;
+	const struct exthdr_desc *desc;
+	struct expr *expr;
+	uint8_t optnum;
 
-		for (j = 0; j < array_size(tcpopt_protocols[i]->templates); ++j) {
-			tmp = &tcpopt_protocols[i]->templates[j];
-			if (!tmp->token || strcmp(option_field, tmp->token))
-				continue;
+	desc = tcpopthdr_protocols[type];
+	tmpl = &desc->templates[field];
+	if (!tmpl)
+		return NULL;
 
-			desc = tcpopt_protocols[i];
-			tmpl = tmp;
-			goto found;
-		}
-	}
+	optnum = tcpopt_find_optnum(type);
 
-found:
-	/* tmpl still points to tcpopt_unknown_template if nothing was found and
-	 * desc is null
-	 */
 	expr = expr_alloc(loc, &exthdr_expr_ops, tmpl->dtype,
 			  BYTEORDER_BIG_ENDIAN, tmpl->len);
 	expr->exthdr.desc   = desc;
 	expr->exthdr.tmpl   = tmpl;
 	expr->exthdr.op     = NFT_EXTHDR_OP_TCPOPT;
-	expr->exthdr.offset = calc_offset(desc, tmpl, option_num);
+	expr->exthdr.offset = calc_offset(desc, tmpl, optnum);
 
 	return expr;
 }