[netsniff-ng] [PATCH v3 10/16] trafgen: l2: Add ARP header generation logic

[Vadim Kochan]

Add ARP proto header fields generation via src mac, src ip,
dst mac, dst ip & operaion.

By default Ethernet proto will be initialized, and ARP Announcement
request is filled.

Signed-off-by: Vadim Kochan <vadi...@gmail.com>
---
 trafgen_l2.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 trafgen_l2.h | 12 ++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/trafgen_l2.c b/trafgen_l2.c
index 1082049..a95ba91 100644
--- a/trafgen_l2.c
+++ b/trafgen_l2.c
@@ -3,10 +3,15 @@
  * Subject to the GPL, version 2.
  */
 
+#include <net/if_arp.h>
+#include <linux/if_ether.h>
+
 #include "built_in.h"
 #include "trafgen_l2.h"
 #include "trafgen_proto.h"
 
+#define ETH_BCAST { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }
+
 struct proto_field eth_fields[] = {
        { .id = ETH_DST_ADDR, .len = 6, },
        { .id = ETH_SRC_ADDR, .len = 6, .offset = 6 },
@@ -26,7 +31,54 @@ static struct proto_hdr eth_hdr = {
        .header_init    = eth_header_init,
 };
 
+static struct proto_field arp_fields[] = {
+       { .id = ARP_HTYPE, .len = 2 },
+       { .id = ARP_PTYPE, .len = 2, .offset = 2 },
+       { .id = ARP_HLEN,  .len = 1, .offset = 4 },
+       { .id = ARP_PLEN,  .len = 1, .offset = 5 },
+       { .id = ARP_OPER,  .len = 2, .offset = 6 },
+       { .id = ARP_SHA,   .len = 6, .offset = 8 },
+       { .id = ARP_SPA,   .len = 4, .offset = 14 },
+       { .id = ARP_THA,   .len = 6, .offset = 18 },
+       { .id = ARP_TPA,   .len = 4, .offset = 24 },
+};
+
+static void arp_header_init(struct proto_hdr *hdr)
+{
+       struct proto_hdr *lower;
+
+       proto_lower_default_add(PROTO_ETH);
+
+       lower = proto_current_header();
+
+       if (lower->id == PROTO_ETH) {
+               uint8_t bcast[6] = ETH_BCAST;
+
+               proto_field_set_default_bytes(lower, ETH_DST_ADDR, bcast);
+               proto_field_set_default_be16(lower, ETH_PROTO_ID, ETH_P_ARP);
+       }
+
+       proto_header_fields_add(hdr, arp_fields, array_size(arp_fields));
+
+       /* Generate Announce request by default */
+       proto_field_set_default_be16(hdr, ARP_HTYPE, ARPHRD_ETHER);
+       proto_field_set_default_be16(hdr, ARP_PTYPE, ETH_P_IP);
+       proto_field_set_default_u8(hdr, ARP_HLEN, 6);
+       proto_field_set_default_u8(hdr, ARP_PLEN, 4);
+       proto_field_set_default_be16(hdr, ARP_OPER, ARPOP_REQUEST);
+       proto_field_set_default_dev_mac(hdr, ARP_SHA);
+       proto_field_set_default_dev_ipv4(hdr, ARP_SPA);
+       proto_field_set_default_dev_ipv4(hdr, ARP_TPA);
+}
+
+static struct proto_hdr arp_hdr = {
+       .id             = PROTO_ARP,
+       .layer          = PROTO_L2,
+       .header_init    = arp_header_init,
+};
+
 void protos_l2_init(void)
 {
        proto_header_register(&eth_hdr);
+       proto_header_register(&arp_hdr);
 }
diff --git a/trafgen_l2.h b/trafgen_l2.h
index 75d3d33..63cef2f 100644
--- a/trafgen_l2.h
+++ b/trafgen_l2.h
@@ -7,6 +7,18 @@ enum eth_field {
        ETH_PROTO_ID,
 };
 
+enum arp_field {
+       ARP_HTYPE,
+       ARP_PTYPE,
+       ARP_HLEN,
+       ARP_PLEN,
+       ARP_OPER,
+       ARP_SHA,
+       ARP_SPA,
+       ARP_THA,
+       ARP_TPA,
+};
+
 extern void protos_l2_init(void);
 
 #endif /* TRAFGEN_L2_I_H */
-- 
2.6.3

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