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checkipheader.cc
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Wed, Jul 9, 04:55

checkipheader.cc
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/*
* checkipheader.{cc,hh} -- element checks IP header for correctness
* (checksums, lengths, source addresses)
* Robert Morris, Eddie Kohler
*
* Copyright (c) 1999-2000 Massachusetts Institute of Technology
* Copyright (c) 2003 International Computer Science Institute
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, subject to the conditions
* listed in the Click LICENSE file. These conditions include: you must
* preserve this copyright notice, and you cannot mention the copyright
* holders in advertising related to the Software without their permission.
* The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
* notice is a summary of the Click LICENSE file; the license in that file is
* legally binding.
*/
#include <click/config.h>
#include "checkipheader.hh"
#include <clicknet/ip.h>
#include <click/glue.hh>
#include <click/args.hh>
#include <click/straccum.hh>
#include <click/error.hh>
#include <click/standard/alignmentinfo.hh>
CLICK_DECLS
const char * const CheckIPHeader::reason_texts[NREASONS] = {
"tiny packet", "bad IP version", "bad IP header length",
"bad IP length", "bad IP checksum", "bad source address"
};
#define IPADDR_LIST_INTERFACES ((void *)0)
#define IPADDR_LIST_BADSRC ((void *)1)
#define IPADDR_LIST_BADSRC_OLD ((void *)2)
bool
CheckIPHeader::OldBadSrcArg::parse(const String &str, Vector<IPAddress> &result, Args &args)
{
if (IPAddressArg().parse(str, result, args)) {
result.push_back(IPAddress(0));
result.push_back(IPAddress(0xFFFFFFFFU));
return true;
} else
return false;
}
bool
CheckIPHeader::InterfacesArg::parse(const String &str,
Vector<IPAddress> &result_bad_src,
Vector<IPAddress> &result_good_dst,
Args &args)
{
String arg(str);
IPAddress ip, mask;
int nwords = 0;
while (String word = cp_shift_spacevec(arg)) {
++nwords;
if (IPPrefixArg(true).parse(word, ip, mask, args)) {
result_bad_src.push_back((ip & mask) | ~mask);
result_good_dst.push_back(ip);
} else
return false;
}
if (nwords == result_bad_src.size()) {
result_bad_src.push_back(IPAddress(0));
result_bad_src.push_back(IPAddress(0xFFFFFFFFU));
return true;
}
args.error("out of memory");
return false;
}
CheckIPHeader::CheckIPHeader()
: _checksum(true), _reason_drops(0)
{
_drops = 0;
}
CheckIPHeader::~CheckIPHeader()
{
delete[] _reason_drops;
}
int
CheckIPHeader::configure(Vector<String> &conf, ErrorHandler *errh)
{
_offset = 0;
bool verbose = false;
bool details = false;
bool offset_empower = false;
if (Args(this, errh).bind(conf)
.read("INTERFACES", InterfacesArg(), _bad_src, _good_dst)
.read("BADSRC", _bad_src)
.read("GOODDST", _good_dst)
.read("OFFSET", _offset)
.read("VERBOSE", verbose)
.read("DETAILS", details)
.read("CHECKSUM", _checksum)
.read("OFFSET_ACNE", offset_empower)
.consume() < 0)
return -1;
if (conf.size() == 0
|| (conf.size() == 1 && IntArg().parse(conf[0], _offset)))
/* nada */;
else if (Args(conf, this, errh)
.read("BADSRC", OldBadSrcArg(), _bad_src)
.read("OFFSET", _offset)
.complete() < 0)
return -1;
if(offset_empower)
_offset += sizeof(empower_header);
click_chatter("CheckIPHeader %s configured with offset %d", name().c_str(), _offset);
_verbose = verbose;
if (details) {
_reason_drops = new atomic_uint32_t[NREASONS];
for (int i = 0; i < NREASONS; ++i)
_reason_drops[i] = 0;
}
#if HAVE_FAST_CHECKSUM && FAST_CHECKSUM_ALIGNED
// check alignment
if (_checksum) {
int ans, c, o;
ans = AlignmentInfo::query(this, 0, c, o);
o = (o + 4 - (_offset % 4)) % 4;
_aligned = (ans && c == 4 && o == 0);
if (!_aligned)
errh->warning("IP header unaligned, cannot use fast IP checksum");
if (!ans)
errh->message("(Try passing the configuration through `click-align'.)");
}
#endif
//for (int i = 0; i < _bad_src.n; i++)
// click_chatter("bad: %s", IPAddress(_bad_src.vec[i]).s().c_str());
//for (int i = 0; i < _good_dst.n; i++)
// click_chatter("good: %s", IPAddress(_good_dst.vec[i]).s().c_str());
return 0;
}
Packet *
CheckIPHeader::drop(Reason reason, Packet *p)
{
if (_drops == 0 || _verbose)
click_chatter("%s: IP header check failed: %s", name().c_str(), reason_texts[reason]);
_drops++;
if (_reason_drops)
_reason_drops[reason]++;
if (noutputs() == 2)
output(1).push(p);
else
p->kill();
return 0;
}
Packet *
CheckIPHeader::simple_action(Packet *p)
{
const click_ip *ip = reinterpret_cast<const click_ip *>(p->data() + _offset);
unsigned plen = p->length() - _offset;
unsigned hlen, len;
// cast to int so very large plen is interpreted as negative
if ((int)plen < (int)sizeof(click_ip))
return drop(MINISCULE_PACKET, p);
if (ip->ip_v != 4)
return drop(BAD_VERSION, p);
hlen = ip->ip_hl << 2;
if (hlen < sizeof(click_ip))
return drop(BAD_HLEN, p);
len = ntohs(ip->ip_len);
if (len > plen || len < hlen)
return drop(BAD_IP_LEN, p);
if (_checksum) {
int val;
#if HAVE_FAST_CHECKSUM && FAST_CHECKSUM_ALIGNED
if (_aligned)
val = ip_fast_csum((unsigned char *)ip, ip->ip_hl);
else
val = click_in_cksum((const unsigned char *)ip, hlen);
#elif HAVE_FAST_CHECKSUM
val = ip_fast_csum((unsigned char *)ip, ip->ip_hl);
#else
val = click_in_cksum((const unsigned char *)ip, hlen);
#endif
if (val != 0)
return drop(BAD_CHECKSUM, p);
}
/*
* RFC1812 5.3.7 and 4.2.2.11: discard illegal source addresses.
* Configuration string should have listed all subnet
* broadcast addresses known to this router.
*/
if (find(_bad_src.begin(), _bad_src.end(), IPAddress(ip->ip_src)) < _bad_src.end()
&& find(_good_dst.begin(), _good_dst.end(), IPAddress(ip->ip_dst)) == _good_dst.end())
return drop(BAD_SADDR, p);
/*
* RFC1812 4.2.3.1: discard illegal destinations.
* We now do this in the IP routing table.
*/
p->set_ip_header(ip, hlen);
// shorten packet according to IP length field -- 7/28/2000
if (plen > len)
p->take(plen - len);
// set destination IP address annotation if it doesn't exist already --
// 9/26/2001
// always set destination IP address annotation; linuxmodule problem
// reported by Parveen Kumar Patel at Utah -- 4/3/2002
p->set_dst_ip_anno(ip->ip_dst);
return(p);
}
String
CheckIPHeader::read_handler(Element *e, void *)
{
CheckIPHeader *c = reinterpret_cast<CheckIPHeader *>(e);
StringAccum sa;
for (int i = 0; i < NREASONS; i++)
sa << c->_reason_drops[i] << '\t' << reason_texts[i] << '\n';
return sa.take_string();
}
void
CheckIPHeader::add_handlers()
{
add_data_handlers("drops", Handler::OP_READ, &_drops);
if (_reason_drops)
add_read_handler("drop_details", read_handler, 1);
}
CLICK_ENDDECLS
EXPORT_ELEMENT(CheckIPHeader)

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