trafgen: l7: Add DNS header generation API

Add trafgen_l7.c module with DNS proto header generation with
support of filling DNS query/answer/authority/additional sections
as sub headers.

Introcuded new concept as 'sub header' which is needed to easy handle
DNS sections which might be added on-demand, and to simplify using
sub-header as regular header with a fields, offset, etc. There is a
parent header which contains array of pointers of sub-headers, and the
array is ordered as they are located in the parent header. The
sub-headers mostly encapsulated by the parent header which 'knows'
the semantic of them. The new proto_hdr->push_sub_header(...) callback
was added to tell the parent header to push the sub-header's fields,
sub-header also may have proto_ops which must be filled by the parent.
This sub-header concept might be used in the future if it will be needed
to support DHCP, WLAN headers.

There are 4 kinds of DNS sub-headers - query, answer, authority,
additional. 'id' of each sub-header is used to only differentiate these
types of sections. These sections have strict order inside DNS header,
and there was added the proto_hdr_move_sub_header(...) to sort them in
required order.

Actually there are only 2 proto_hdr's which describes 4 DNS sections -
query & rrecord, because rrecord covers another 3 - answer, auhority,
additional which have the same layout.

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

1 files changed, 32 insertions, 0 deletions

diff --git a/trafgen_l4.c b/trafgen_l4.c
index 5a694b3..198d622 100644
--- a/trafgen_l4.c
+++ b/trafgen_l4.c
@@ -80,6 +80,21 @@ static void udp_packet_finish(struct proto_hdr *hdr)
 	udp_csum_update(hdr);
 }
 
+static void udp_set_next_proto(struct proto_hdr *hdr, enum proto_id pid)
+{
+	uint16_t dport;
+
+	switch (pid) {
+	case PROTO_DNS:
+		dport = 53;
+		break;
+	default:
+		bug();
+	}
+
+	proto_hdr_field_set_default_be16(hdr, UDP_DPORT, dport);
+}
+
 static const struct proto_ops udp_proto_ops = {
 	.id		= PROTO_UDP,
 	.layer		= PROTO_L4,
@@ -87,6 +102,7 @@ static const struct proto_ops udp_proto_ops = {
 	.packet_update  = udp_csum_update,
 	.packet_finish  = udp_packet_finish,
 	.field_changed  = udp_field_changed,
+	.set_next_proto = udp_set_next_proto,
 };
 
 static struct proto_field tcp_fields[] = {
@@ -160,6 +176,21 @@ static void tcp_csum_update(struct proto_hdr *hdr)
 	hdr->is_csum_valid = true;
 }
 
+static void tcp_set_next_proto(struct proto_hdr *hdr, enum proto_id pid)
+{
+	uint16_t dport;
+
+	switch (pid) {
+	case PROTO_DNS:
+		dport = 53;
+		break;
+	default:
+		bug();
+	}
+
+	proto_hdr_field_set_default_be16(hdr, TCP_DPORT, dport);
+}
+
 static const struct proto_ops tcp_proto_ops = {
 	.id		= PROTO_TCP,
 	.layer		= PROTO_L4,
@@ -167,6 +198,7 @@ static const struct proto_ops tcp_proto_ops = {
 	.packet_update  = tcp_csum_update,
 	.packet_finish  = tcp_csum_update,
 	.field_changed  = tcp_field_changed,
+	.set_next_proto = tcp_set_next_proto,
 };
 
 static struct proto_field icmpv4_fields[] = {