/*
* (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 <libnetfilter_queue/libnetfilter_queue.h>
#include <libnetfilter_queue/libnetfilter_queue_ipv4.h>
#include <libnetfilter_queue/pktbuff.h>
#include "internal.h"
/**
* \defgroup ipv4 IPv4 helper functions
* @{
*/
/**
* nfq_ip_get_hdr - get the IPv4 header
* \param pktb: Pointer to user-space network packet buffer
* \returns validated pointer to the IPv4 header or NULL if IP is malformed or
* not version 4
*
* Many programs will not need to call this function. A possible use is to
* determine the layer 4 protocol. The validation is that the buffer is big
* enough for the declared lengths in the header, i.e. an extra check for packet
* truncation.
*/
EXPORT_SYMBOL
struct iphdr *nfq_ip_get_hdr(struct pkt_buff *pktb)
{
struct iphdr *iph;
unsigned int pktlen = pktb_tail(pktb) - pktb->network_header;
/* Not enough room for IPv4 header. */
if (pktlen < sizeof(struct iphdr))
return NULL;
iph = (struct iphdr *)pktb->network_header;
/* Not IPv4 packet. */
if (iph->version != 4)
return NULL;
/* Malformed IPv4 total length field. */
if (ntohs(iph->tot_len) > pktlen)
return NULL;
return iph;
}
/**
* nfq_ip_set_transport_header - set the \b transport_header field in \b pktb
* \param pktb: Pointer to user-space network packet buffer
* \param iph: Pointer to the IPv4 header
* \returns 0 on success or -1 if a minimal validation check fails
* \note
* Most programs should call __nfq_ip_set_transport_header__ as soon as
* possible, since most layer 4 helper functions assume the
* \b transport_header field is valid.
*/
EXPORT_SYMBOL
int nfq_ip_set_transport_header(struct pkt_buff *pktb, struct iphdr *iph)
{
int doff = iph->ihl * 4;
/* Wrong offset to IPv4 payload. */
if ((int)pktb->len - doff <= 0)
return -1;
pktb->transport_header = pktb->network_header + doff;
return 0;
}
/**
* \defgroup ip_internals Internal IP functions
*
* Most user-space programs will never need these.
*
* @{
*/
/**
* nfq_ip_set_checksum - set IPv4 checksum
* \param iph: Pointer to the IPv4 header
* \note
* nfq_ip_mangle() invokes this function.
* As long as developers always use the appropriate mangler for the layer being
* mangled, there is no need to call __nfq_ip_set_checksum__.
*/
EXPORT_SYMBOL
void nfq_ip_set_checksum(struct iphdr *iph)
{
uint32_t iph_len = iph->ihl * 4;
iph->check = 0;
iph->check = nfq_checksum(0, (uint16_t *)iph, iph_len);
}
/**
* @}
*/
/**
* nfq_ip_mangle - mangle IPv4 packet buffer
* \param pktb: Pointer to user-space network packet buffer
* \param dataoff: Offset to layer 4 header, or zero to mangle IP header
* \param match_offset: Offset to 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 length if necessary and recalculates the
* IPv4 checksum.
*/
EXPORT_SYMBOL
int nfq_ip_mangle(struct pkt_buff *pktb, unsigned int dataoff,
unsigned int match_offset, unsigned int match_len,
const char *rep_buffer, unsigned int rep_len)
{
struct iphdr *iph = (struct iphdr *) pktb->network_header;
if (!pktb_mangle(pktb, dataoff, match_offset, match_len, rep_buffer,
rep_len))
return 0;
/* fix IP hdr checksum information */
iph->tot_len = htons(pktb_tail(pktb) - pktb->network_header);
nfq_ip_set_checksum(iph);
return 1;
}
/**
* nfq_pkt_snprintf_ip - print IPv4 header into buffer in iptables LOG format
* \param buf: Pointer to buffer that will be used to print the header
* \param size: Size of the buffer (or remaining room in it)
* \param iph: Pointer to a valid IPv4 header
* \returns same as snprintf
* \sa **snprintf**(3)
*/
EXPORT_SYMBOL
int nfq_ip_snprintf(char *buf, size_t size, const struct iphdr *iph)
{
int ret;
struct in_addr src = { iph->saddr };
struct in_addr dst = { iph->daddr };
char src_str[INET_ADDRSTRLEN];
char dst_str[INET_ADDRSTRLEN];
ret = snprintf(buf, size, "SRC=%s DST=%s LEN=%u TOS=0x%X "
"PREC=0x%X TTL=%u ID=%u PROTO=%u ",
inet_ntop(AF_INET, &src, src_str, INET_ADDRSTRLEN),
inet_ntop(AF_INET, &dst, dst_str, INET_ADDRSTRLEN),
ntohs(iph->tot_len), IPTOS_TOS(iph->tos),
IPTOS_PREC(iph->tos), iph->ttl, ntohs(iph->id),
iph->protocol);
return ret;
}
/**
* @}
*/