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mirror of https://git.FreeBSD.org/src.git synced 2024-12-24 11:29:10 +00:00
freebsd/usr.sbin/ppp/tcpmss.c
Brian Somers 30949fd4b5 o Add ipv6 support, abstracting most NCP addresses into opaque
structures (well, they're treated as opaque).

  It's now possible to manage IPv6 interface addresses and routing
  table entries and to filter IPV6 traffic whether encapsulated or
  not.

  IPV6CP support is crude for now, and hasn't been tested against
  any other implementations.

  RADIUS and IPv6 are independent of eachother for now.

  ppp.linkup/ppp.linkdown aren't currently used by IPV6CP

o Understand all protocols(5) in filter rules rather than only a select
  few.

o Allow a mask specification for the ``delete'' command.  It's now
  possible to specifically delete one of two conflicting routes.

o When creating and deleting proxy arp entries, do it for all IPv4
  interface addresses rather than doing it just for the ``current''
  peer address.

o When iface-alias isn't in effect, don't blow away manually (via ``iface
  add'') added interface addresses.

o When listening on a tcp server (diagnostic) socket, bind so that a
  tcp46 socket is created -- allowing both IPv4 and IPv6 connections.

o When displaying ICMP traffic, don't display the icmp type twice.
  When display traffic, display at least some information about unrecognised
  traffic.

o Bump version

Inspired after filtering work by: Makoto MATSUSHITA <matusita@jp.FreeBSD.org>
2001-08-14 16:05:52 +00:00

187 lines
5.0 KiB
C

/*-
* Copyright (c) 2000 Ruslan Ermilov and Brian Somers <brian@Awfulhak.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/socket.h>
#include <net/route.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <sys/un.h>
#include <termios.h>
#include "layer.h"
#include "defs.h"
#include "log.h"
#include "timer.h"
#include "fsm.h"
#include "mbuf.h"
#include "throughput.h"
#include "lqr.h"
#include "hdlc.h"
#include "lcp.h"
#include "ccp.h"
#include "link.h"
#include "iplist.h"
#include "slcompress.h"
#include "ncpaddr.h"
#include "ip.h"
#include "ipcp.h"
#include "filter.h"
#include "descriptor.h"
#include "mp.h"
#include "iface.h"
#ifndef NORADIUS
#include "radius.h"
#endif
#include "ipv6cp.h"
#include "ncp.h"
#include "bundle.h"
/*-
* We are in a liberal position about MSS
* (RFC 879, section 7).
*/
#define MAXMSS(mtu) (mtu - sizeof(struct ip) - sizeof(struct tcphdr))
/*-
* The following macro is used to update an
* internet checksum. "acc" is a 32-bit
* accumulation of all the changes to the
* checksum (adding in old 16-bit words and
* subtracting out new words), and "cksum"
* is the checksum value to be updated.
*/
#define ADJUST_CHECKSUM(acc, cksum) { \
acc += cksum; \
if (acc < 0) { \
acc = -acc; \
acc = (acc >> 16) + (acc & 0xffff); \
acc += acc >> 16; \
cksum = (u_short) ~acc; \
} else { \
acc = (acc >> 16) + (acc & 0xffff); \
acc += acc >> 16; \
cksum = (u_short) acc; \
} \
}
static void
MSSFixup(struct tcphdr *tc, ssize_t pktlen, u_int16_t maxmss)
{
int hlen, olen, optlen;
u_char *opt;
u_int16_t *mss;
int accumulate;
hlen = tc->th_off << 2;
/* Invalid header length or header without options. */
if (hlen <= sizeof(struct tcphdr) || hlen > pktlen)
return;
/* MSS option only allowed within SYN packets. */
if (!(tc->th_flags & TH_SYN))
return;
for (olen = hlen - sizeof(struct tcphdr), opt = (u_char *)(tc + 1);
olen > 0; olen -= optlen, opt += optlen) {
if (*opt == TCPOPT_EOL)
break;
else if (*opt == TCPOPT_NOP)
optlen = 1;
else {
optlen = *(opt + 1);
if (optlen <= 0 || optlen > olen)
break;
if (*opt == TCPOPT_MAXSEG) {
if (optlen != TCPOLEN_MAXSEG)
continue;
mss = (u_int16_t *)(opt + 2);
if (ntohs(*mss) > maxmss) {
log_Printf(LogDEBUG, "MSS: %u -> %u\n",
ntohs(*mss), maxmss);
accumulate = *mss;
*mss = htons(maxmss);
accumulate -= *mss;
ADJUST_CHECKSUM(accumulate, tc->th_sum);
}
}
}
}
}
static struct mbuf *
tcpmss_Check(struct bundle *bundle, struct mbuf *bp)
{
struct ip *pip;
int hlen, plen;
if (!Enabled(bundle, OPT_TCPMSSFIXUP))
return bp;
bp = m_pullup(bp);
plen = m_length(bp);
pip = (struct ip *)MBUF_CTOP(bp);
hlen = pip->ip_hl << 2;
/*
* Check for MSS option only for TCP packets with zero fragment offsets
* and correct total and header lengths.
*/
if (pip->ip_p == IPPROTO_TCP && (ntohs(pip->ip_off) & IP_OFFMASK) == 0 &&
ntohs(pip->ip_len) == plen && hlen <= plen &&
plen - hlen >= sizeof(struct tcphdr))
MSSFixup((struct tcphdr *)(MBUF_CTOP(bp) + hlen), plen - hlen,
MAXMSS(bundle->iface->mtu));
return bp;
}
static struct mbuf *
tcpmss_LayerPush(struct bundle *bundle, struct link *l, struct mbuf *bp,
int pri, u_short *proto)
{
return tcpmss_Check(bundle, bp);
}
static struct mbuf *
tcpmss_LayerPull(struct bundle *bundle, struct link *l, struct mbuf *bp,
u_short *proto)
{
return tcpmss_Check(bundle, bp);
}
struct layer tcpmsslayer =
{ LAYER_PROTO, "tcpmss", tcpmss_LayerPush, tcpmss_LayerPull };