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/*
* Copyright 2013 Google Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/*
* Author: ncardwell@google.com (Neal Cardwell)
*
* Implementation for module for formatting UDP packets.
*/
#include "udp_packet.h"
#include "ip_packet.h"
#include "udp.h"
struct packet *new_udp_packet(int address_family,
enum direction_t direction,
struct ip_info ip_info,
u16 udp_payload_bytes,
u16 src_port,
u16 dst_port,
char **error)
{
struct packet *packet = NULL; /* the newly-allocated result packet */
struct header *udp_header = NULL; /* the UDP header info */
/* Calculate lengths in bytes of all sections of the packet */
const int ip_option_bytes = 0;
const int ip_header_bytes = (ip_header_min_len(address_family) +
ip_option_bytes);
const int udp_header_bytes = sizeof(struct udp);
const int ip_bytes =
ip_header_bytes + udp_header_bytes + udp_payload_bytes;
/* Sanity-check all the various lengths */
if (ip_option_bytes & 0x3) {
asprintf(error, "IP options are not padded correctly "
"to ensure IP header is a multiple of 4 bytes: "
"%d excess bytes", ip_option_bytes & 0x3);
return NULL;
}
assert((udp_header_bytes & 0x3) == 0);
assert((ip_header_bytes & 0x3) == 0);
if (ip_bytes > MAX_UDP_DATAGRAM_BYTES) {
asprintf(error, "UDP datagram too large");
return NULL;
}
/* Allocate and zero out a packet object of the desired size */
packet = packet_new(ip_bytes);
memset(packet->buffer, 0, ip_bytes);
packet->direction = direction;
packet->flags = 0;
packet->tos_chk = ip_info.tos.check;
/* Set IP header fields */
set_packet_ip_header(packet, address_family, ip_bytes,
ip_info.tos.value, ip_info.flow_label,
ip_info.ttl, IPPROTO_UDP);
udp_header = packet_append_header(packet, HEADER_UDP,
sizeof(struct udp));
udp_header->total_bytes = udp_header_bytes + udp_payload_bytes;
/* Find the start of UDP section of the packet */
packet->udp = (struct udp *) (ip_start(packet) + ip_header_bytes);
/* Set UDP header fields */
packet->udp->src_port = htons(src_port);
packet->udp->dst_port = htons(dst_port);
packet->udp->len = htons(udp_header_bytes + udp_payload_bytes);
packet->udp->check = 0;
packet->ip_bytes = ip_bytes;
return packet;
}
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