/*
 * netsniff-ng - the packet sniffing beast
 * Subject to the GPL, version 2.
 */

#include <linux/if_ether.h>

#include "csum.h"
#include "built_in.h"
#include "trafgen_l2.h"
#include "trafgen_l3.h"
#include "trafgen_proto.h"
#include "trafgen_conf.h"

static struct proto_field ipv4_fields[] = {
	{ .id = IP4_VER,       .len = 1, .offset = 0, .shift = 4, .mask = 0xf0 },
	{ .id = IP4_IHL,       .len = 1, .offset = 0, .shift = 0, .mask = 0x0f },
	{ .id = IP4_DSCP,      .len = 1, .offset = 1, .shift = 2, .mask = 0xfc },
	{ .id = IP4_ECN,       .len = 1, .offset = 1, .shift = 0, .mask = 0x03 },
	{ .id = IP4_TOS,       .len = 1, .offset = 1 },
	{ .id = IP4_LEN,       .len = 2, .offset = 2 },
	{ .id = IP4_ID,        .len = 2, .offset = 4 },
	{ .id = IP4_FLAGS,     .len = 2, .offset = 6, .shift = 13, .mask = 0xe000 },
	{ .id = IP4_MF,        .len = 2, .offset = 6, .shift = 13, .mask = 0x2000 },
	{ .id = IP4_DF,        .len = 2, .offset = 6, .shift = 14, .mask = 0x4000 },
	{ .id = IP4_FRAG_OFFS, .len = 2, .offset = 6, .shift = 0,  .mask = 0x1fff },
	{ .id = IP4_TTL,       .len = 1, .offset = 8 },
	{ .id = IP4_PROTO,     .len = 1, .offset = 9 },
	{ .id = IP4_CSUM,      .len = 2, .offset = 10 },
	{ .id = IP4_SADDR,     .len = 4, .offset = 12 },
	{ .id = IP4_DADDR,     .len = 4, .offset = 16 },
};

static void ipv4_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)
		proto_field_set_default_be16(lower, ETH_PROTO_ID, ETH_P_IP);
	else if (lower->id == PROTO_IP4)
		proto_field_set_default_u8(lower, IP4_PROTO, IPPROTO_IPIP);

	proto_header_fields_add(hdr, ipv4_fields, array_size(ipv4_fields));

	proto_field_set_default_u8(hdr, IP4_VER, 4);
	proto_field_set_default_u8(hdr, IP4_IHL, 5);
	proto_field_set_default_dev_ipv4(hdr, IP4_SADDR);
}

static void ipv4_packet_finish(struct proto_hdr *hdr)
{
	struct packet *pkt = current_packet();
	uint16_t total_len;

	total_len = pkt->len - hdr->pkt_offset;
	proto_field_set_default_be16(hdr, IP4_LEN, total_len);

	if (!proto_field_is_set(hdr, IP4_CSUM)) {
		uint16_t csum;
		uint8_t ihl;

		ihl = proto_field_get_u8(hdr, IP4_IHL);
		csum = htons(calc_csum(&pkt->payload[hdr->pkt_offset], ihl * 4));
		proto_field_set_u16(hdr, IP4_CSUM, bswap_16(csum));
	}
}

static struct proto_hdr ipv4_hdr = {
	.id		= PROTO_IP4,
	.layer		= PROTO_L3,
	.header_init	= ipv4_header_init,
	.packet_finish  = ipv4_packet_finish,
};

void protos_l3_init(void)
{
	proto_header_register(&ipv4_hdr);
}
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<div class='content'><table summary='tree listing' class='list'>
<tr class='nohover'><th class='left'>Mode</th><th class='left'>Name</th><th class='right'>Size</th><th/></tr>