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/*
* (C) 2012 by Pablo Neira Ayuso <pablo@netfilter.org>
*
* 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 code has been sponsored by Vyatta Inc. <http://www.vyatta.com>
*/
#include <stdio.h>
#include <stdbool.h>
#include <arpa/inet.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#define _GNU_SOURCE
#include <netinet/udp.h>
#include <libnetfilter_queue/libnetfilter_queue.h>
#include <libnetfilter_queue/libnetfilter_queue_udp.h>
#include <libnetfilter_queue/libnetfilter_queue_ipv4.h>
#include <libnetfilter_queue/pktbuff.h>
#include "internal.h"
/**
* \defgroup udp UDP helper functions
* @{
*/
/**
* nfq_udp_get_hdr - get the UDP header.
* \param pktb: Pointer to network packet buffer
*
* This function returns NULL if invalid UDP header is found. On success,
* it returns the UDP header.
*/
EXPORT_SYMBOL
struct udphdr *nfq_udp_get_hdr(struct pkt_buff *pktb)
{
if (pktb->transport_header == NULL)
return NULL;
/* No room for the UDP header. */
if (pktb->tail - pktb->transport_header < sizeof(struct udphdr))
return NULL;
return (struct udphdr *)pktb->transport_header;
}
/**
* nfq_udp_get_payload - get the UDP packet payload.
* \param udph: Pointer to UDP header
* \param pktb: Pointer to network packet buffer
*/
EXPORT_SYMBOL
void *nfq_udp_get_payload(struct udphdr *udph, struct pkt_buff *pktb)
{
uint16_t len = ntohs(udph->len);
/* the UDP packet is too short. */
if (len < sizeof(struct udphdr))
return NULL;
/* malformed UDP packet. */
if (pktb->transport_header + len > pktb->tail)
return NULL;
return pktb->transport_header + sizeof(struct udphdr);
}
/**
* nfq_udp_get_payload_len - get the udp packet payload.
* \param udph: Pointer to UDP header
* \param pktb: Pointer to network packet buffer
*/
EXPORT_SYMBOL
unsigned int nfq_udp_get_payload_len(struct udphdr *udph, struct pkt_buff *pktb)
{
return pktb->tail - pktb->transport_header - sizeof(struct udphdr);
}
/**
* nfq_udp_set_checksum_ipv4 - computes a IPv4/TCP packet's segment
* \param iphdrp: pointer to the ip header
* \param ippayload: payload of the ip packet
*
* \returns the checksum of the udp segment.
*
* \see nfq_pkt_compute_ip_checksum
* \see nfq_pkt_compute_udp_checksum
*/
EXPORT_SYMBOL
void nfq_udp_compute_checksum_ipv4(struct udphdr *udph, struct iphdr *iph)
{
/* checksum field in header needs to be zero for calculation. */
udph->check = 0;
udph->check = nfq_checksum_tcpudp_ipv4(iph, IPPROTO_UDP);
}
/**
* nfq_udp_set_checksum_ipv6 - computes a IPv6/TCP packet's segment
* \param iphdrp: pointer to the ip header
* \param ippayload: payload of the ip packet
*
* \returns the checksum of the udp segment.
*
* \see nfq_pkt_compute_ip_checksum
* \see nfq_pkt_compute_udp_checksum
*/
EXPORT_SYMBOL
void nfq_udp_compute_checksum_ipv6(struct udphdr *udph, struct ip6_hdr *ip6h)
{
/* checksum field in header needs to be zero for calculation. */
udph->check = 0;
udph->check = nfq_checksum_tcpudp_ipv6(ip6h, udph, IPPROTO_UDP);
}
/**
* nfq_udp_mangle_ipv4 - Mangle UDP/IPv4 packet buffer
* \param pktb: Pointer to network packet buffer
* \param match_offset: Offset from start of UDP data of content that you want
* to mangle
* \param match_len: Length of the existing content you want to mangle
* \param rep_buffer: Pointer to data you want to use to replace current content
* \param rep_len: Length of data you want to use to replace current content
* \returns 1 for success and 0 for failure. See pktb_mangle() for failure case
* \note This function updates the IPv4 and UDP lengths and recalculates their
* checksums for you.
*/
EXPORT_SYMBOL
int nfq_udp_mangle_ipv4(struct pkt_buff *pktb,
unsigned int match_offset, unsigned int match_len,
const char *rep_buffer, unsigned int rep_len)
{
struct iphdr *iph;
struct udphdr *udph;
iph = (struct iphdr *)pktb->network_header;
udph = (struct udphdr *)(pktb->network_header + iph->ihl*4);
udph->len = htons(ntohs(udph->len) + rep_len - match_len);
if (!nfq_ip_mangle(pktb, iph->ihl*4 + sizeof(struct udphdr),
match_offset, match_len, rep_buffer, rep_len))
return 0;
nfq_udp_compute_checksum_ipv4(udph, iph);
return 1;
}
/**
* nfq_pkt_snprintf_udp_hdr - print udp header into one buffer in a humnan
* readable way
* \param buf: pointer to buffer that is used to print the object
* \param size: size of the buffer (or remaining room in it).
* \param udp: pointer to a valid udp header.
*
*/
EXPORT_SYMBOL
int nfq_udp_snprintf(char *buf, size_t size, const struct udphdr *udph)
{
return snprintf(buf, size, "SPT=%u DPT=%u ",
htons(udph->source), htons(udph->dest));
}
/**
* @}
*/
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