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-rw-r--r--trafgen_l4.c71
1 files changed, 71 insertions, 0 deletions
diff --git a/trafgen_l4.c b/trafgen_l4.c
new file mode 100644
index 0000000..286e54a
--- /dev/null
+++ b/trafgen_l4.c
@@ -0,0 +1,71 @@
+/*
+ * netsniff-ng - the packet sniffing beast
+ * Subject to the GPL, version 2.
+ */
+
+#include <stdbool.h>
+#include <netinet/in.h>
+
+#include "die.h"
+#include "csum.h"
+#include "built_in.h"
+#include "trafgen_l3.h"
+#include "trafgen_l4.h"
+#include "trafgen_conf.h"
+#include "trafgen_proto.h"
+
+static struct proto_field udp_fields[] = {
+ { .id = UDP_SPORT, .len = 2, .offset = 0 },
+ { .id = UDP_DPORT, .len = 2, .offset = 2 },
+ { .id = UDP_LEN, .len = 2, .offset = 4 },
+ { .id = UDP_CSUM, .len = 2, .offset = 6 },
+};
+
+static void udp_header_init(struct proto_hdr *hdr)
+{
+ struct proto_hdr *lower;
+
+ proto_lower_default_add(PROTO_IP4);
+
+ lower = proto_current_header();
+
+ if (lower->id == PROTO_IP4)
+ proto_field_set_default_u8(lower, IP4_PROTO, IPPROTO_UDP);
+
+ proto_header_fields_add(hdr, udp_fields, array_size(udp_fields));
+}
+
+static void udp_packet_finish(struct proto_hdr *hdr)
+{
+ struct proto_hdr *lower = proto_lower_header(hdr);
+ struct packet *pkt = current_packet();
+ uint16_t total_len;
+ uint16_t csum;
+
+ total_len = pkt->len - hdr->pkt_offset;
+ proto_field_set_default_be16(hdr, UDP_LEN, total_len);
+
+ if (proto_field_is_set(hdr, UDP_CSUM))
+ return;
+
+ if (!lower || lower->id != PROTO_IP4)
+ return;
+
+ total_len = proto_field_get_u16(hdr, UDP_LEN);
+ csum = p4_csum((void *) proto_header_ptr(lower), proto_header_ptr(hdr),
+ total_len, IPPROTO_UDP);
+
+ proto_field_set_be16(hdr, UDP_CSUM, bswap_16(csum));
+}
+
+static struct proto_hdr udp_hdr = {
+ .id = PROTO_UDP,
+ .layer = PROTO_L4,
+ .header_init = udp_header_init,
+ .packet_finish = udp_packet_finish,
+};
+
+void protos_l4_init(void)
+{
+ proto_header_register(&udp_hdr);
+}