src: Adding support for segment routing header 'srh'

Segment Routing Header "SRH" is new type of IPv6 Routing extension
header (type 4).

SRH contains a list of segments (each is represented as an IPv6 address)
to be visited by packets during the journey from source to destination.

The SRH specification are defined in the below IETF SRH draft.
https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-07

Signed-off-by: Ahmed Abdelsalam <amsalam20@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

5 files changed, 71 insertions, 3 deletions

diff --git a/include/exthdr.h b/include/exthdr.h
index 06bf6285..32f99c9c 100644
--- a/include/exthdr.h
+++ b/include/exthdr.h
@@ -57,6 +57,14 @@ enum rt2_hdr_fields {
 	RT2HDR_ADDR,
 };
 
+enum rt4_hdr_fields {
+	RT4HDR_INVALID,
+	RT4HDR_LASTENT,
+	RT4HDR_FLAGS,
+	RT4HDR_TAG,
+	RT4HDR_SID_1,
+};
+
 enum frag_hdr_fields {
 	FRAGHDR_INVALID,
 	FRAGHDR_NEXTHDR,
@@ -87,6 +95,7 @@ extern const struct exthdr_desc exthdr_hbh;
 extern const struct exthdr_desc exthdr_rt;
 extern const struct exthdr_desc exthdr_rt0;
 extern const struct exthdr_desc exthdr_rt2;
+extern const struct exthdr_desc exthdr_rt4;
 extern const struct exthdr_desc exthdr_frag;
 extern const struct exthdr_desc exthdr_dst;
 extern const struct exthdr_desc exthdr_mh;
diff --git a/include/headers.h b/include/headers.h
index 469d6740..3d564deb 100644
--- a/include/headers.h
+++ b/include/headers.h
@@ -112,6 +112,18 @@ struct ip6_mh {
 	uint8_t		data[0];
 };
 
+/* Type 4 Routing header - well known as srh */
+struct ip6_rt4 {
+	uint8_t		ip6r4_nxt;		/* next header			*/
+	uint8_t		ip6r4_len;		/* length in units of 8 octets	*/
+	uint8_t		ip6r4_type;		/* always zero			*/
+	uint8_t		ip6r4_segleft;		/* segments left		*/
+	uint8_t		ip6r4_last_entry;	/* last entry			*/
+	uint8_t		ip6r4_flags;		/* flags			*/
+	uint16_t	ip6r4_tag;		/* tag				*/
+	struct in6_addr	ip6r4_segments[0];	/* SID list			*/
+};
+
 /* RFC 3775 */
 #define IP6_MH_TYPE_BRR		0	/* Binding Refresh Request	*/
 #define IP6_MH_TYPE_HOTI	1	/* HOTI Message			*/
diff --git a/src/exthdr.c b/src/exthdr.c
index 3757f335..cbe0da86 100644
--- a/src/exthdr.c
+++ b/src/exthdr.c
@@ -101,6 +101,9 @@ struct expr *exthdr_expr_alloc(const struct location *loc,
 		case 2:
 			expr->exthdr.op = NFT_EXTHDR_OP_RT2;
 			break;
+		case 4:
+			expr->exthdr.op = NFT_EXTHDR_OP_RT4;
+			break;
 		}
 	}
 	return expr;
@@ -165,6 +168,8 @@ void exthdr_init_raw(struct expr *expr, uint8_t type,
 		expr->exthdr.desc = &exthdr_rt0;
 	else if (op == NFT_EXTHDR_OP_RT2)
 		expr->exthdr.desc = &exthdr_rt2;
+	else if (op == NFT_EXTHDR_OP_RT4)
+		expr->exthdr.desc = &exthdr_rt4;
 	else if (type < array_size(exthdr_protocols))
 		expr->exthdr.desc = exthdr_protocols[type];
 
@@ -274,6 +279,24 @@ const struct exthdr_desc exthdr_rt0 = {
 	},
 };
 
+#define RT4_FIELD(__name, __member, __dtype) \
+	HDR_TEMPLATE(__name, __dtype, struct ip6_rt4, __member)
+
+const struct exthdr_desc exthdr_rt4 = {
+	.name		= "srh",
+	.type		= IPPROTO_ROUTING,
+	.proto_key	= 4,
+	.templates      = {
+		[RT4HDR_LASTENT]	= RT4_FIELD("last-entry", ip6r4_last_entry, &integer_type),
+		[RT4HDR_FLAGS]		= RT4_FIELD("flags", ip6r4_flags, &integer_type),
+		[RT4HDR_TAG]		= RT4_FIELD("tag", ip6r4_tag, &integer_type),
+		[RT4HDR_SID_1]		= RT4_FIELD("sid[1]", ip6r4_segments[0], &ip6addr_type),
+		[RT4HDR_SID_1 + 1]	= RT4_FIELD("sid[1]", ip6r4_segments[0], &ip6addr_type),
+		// ...
+	},
+};
+
+
 #define RT_FIELD(__name, __member, __dtype) \
 	HDR_TEMPLATE(__name, __dtype, struct ip6_rthdr, __member)
 
diff --git a/src/parser_bison.y b/src/parser_bison.y
index 2ccaf9ab..5f84d794 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -364,8 +364,12 @@ int nft_lex(void *, void *, void *);
 %token RT			"rt"
 %token RT0			"rt0"
 %token RT2			"rt2"
+%token RT4			"srh"
 %token SEG_LEFT			"seg-left"
 %token ADDR			"addr"
+%token LAST_ENT			"last-entry"
+%token TAG			"tag"
+%token SID			"sid"
 
 %token HBH			"hbh"
 
@@ -674,9 +678,9 @@ int nft_lex(void *, void *, void *);
 %type <expr>			hbh_hdr_expr	frag_hdr_expr		dst_hdr_expr
 %destructor { expr_free($$); }	hbh_hdr_expr	frag_hdr_expr		dst_hdr_expr
 %type <val>			hbh_hdr_field	frag_hdr_field		dst_hdr_field
-%type <expr>			rt_hdr_expr	rt0_hdr_expr		rt2_hdr_expr
-%destructor { expr_free($$); }	rt_hdr_expr	rt0_hdr_expr		rt2_hdr_expr
-%type <val>			rt_hdr_field	rt0_hdr_field		rt2_hdr_field
+%type <expr>			rt_hdr_expr	rt0_hdr_expr		rt2_hdr_expr	rt4_hdr_expr
+%destructor { expr_free($$); }	rt_hdr_expr	rt0_hdr_expr		rt2_hdr_expr	rt4_hdr_expr
+%type <val>			rt_hdr_field	rt0_hdr_field		rt2_hdr_field	rt4_hdr_field
 %type <expr>			mh_hdr_expr
 %destructor { expr_free($$); }	mh_hdr_expr
 %type <val>			mh_hdr_field
@@ -3921,6 +3925,7 @@ exthdr_expr		:	hbh_hdr_expr
 			|	rt_hdr_expr
 			|	rt0_hdr_expr
 			|	rt2_hdr_expr
+			|	rt4_hdr_expr
 			|	frag_hdr_expr
 			|	dst_hdr_expr
 			|	mh_hdr_expr
@@ -3969,6 +3974,21 @@ rt2_hdr_expr		:	RT2	rt2_hdr_field
 rt2_hdr_field		:	ADDR		{ $$ = RT2HDR_ADDR; }
 			;
 
+rt4_hdr_expr		:	RT4	rt4_hdr_field
+			{
+				$$ = exthdr_expr_alloc(&@$, &exthdr_rt4, $2);
+			}
+			;
+
+rt4_hdr_field		:	LAST_ENT	{ $$ = RT4HDR_LASTENT; }
+			|	FLAGS		{ $$ = RT4HDR_FLAGS; }
+			|	TAG		{ $$ = RT4HDR_TAG; }
+			|	SID		'['	NUM	']'
+			{
+				$$ = RT4HDR_SID_1 + $3 - 1;
+			}
+			;
+
 frag_hdr_expr		:	FRAG	frag_hdr_field
 			{
 				$$ = exthdr_expr_alloc(&@$, &exthdr_frag, $2);
diff --git a/src/scanner.l b/src/scanner.l
index ab10738b..1d8e8ba0 100644
--- a/src/scanner.l
+++ b/src/scanner.l
@@ -456,8 +456,12 @@ addrstring	({macaddr}|{ip4addr}|{ip6addr})
 "rt"			{ return RT; }
 "rt0"			{ return RT0; }
 "rt2"			{ return RT2; }
+"srh"			{ return RT4; }
 "seg-left"		{ return SEG_LEFT; }
 "addr"			{ return ADDR; }
+"last-entry"		{ return LAST_ENT; }
+"tag"			{ return TAG; }
+"sid"			{ return SID; }
 
 "hbh"			{ return HBH; }