/*-
* ng_tcpmss.c
*
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2004, Alexey Popov <lollypop@flexuser.ru>
* 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 unmodified, 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.
*
* This software includes fragments of the following programs:
* tcpmssd Ruslan Ermilov <ru@FreeBSD.org>
*
* $FreeBSD$
*/
/*
* This node is netgraph tool for workaround of PMTUD problem. It acts
* like filter for IP packets. If configured, it reduces MSS of TCP SYN
* packets.
*
* Configuration can be done by sending NGM_TCPMSS_CONFIG message. The
* message sets filter for incoming packets on hook 'inHook'. Packet's
* TCP MSS field is lowered to 'maxMSS' parameter and resulting packet
* is sent to 'outHook'.
*
* XXX: statistics are updated not atomically, so they may broke on SMP.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/endian.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netgraph/ng_message.h>
#include <netgraph/netgraph.h>
#include <netgraph/ng_parse.h>
#include <netgraph/ng_tcpmss.h>
/* Per hook info. */
typedef struct {
hook_p outHook;
struct ng_tcpmss_hookstat stats;
} *hpriv_p;
/* Netgraph methods. */
static ng_constructor_t ng_tcpmss_constructor;
static ng_rcvmsg_t ng_tcpmss_rcvmsg;
static ng_newhook_t ng_tcpmss_newhook;
static ng_rcvdata_t ng_tcpmss_rcvdata;
static ng_disconnect_t ng_tcpmss_disconnect;
static int correct_mss(struct tcphdr *, int, uint16_t, int);
/* Parse type for struct ng_tcpmss_hookstat. */
static const struct ng_parse_struct_field ng_tcpmss_hookstat_type_fields[]
= NG_TCPMSS_HOOKSTAT_INFO;
static const struct ng_parse_type ng_tcpmss_hookstat_type = {
&ng_parse_struct_type,
&ng_tcpmss_hookstat_type_fields
};
/* Parse type for struct ng_tcpmss_config. */
static const struct ng_parse_struct_field ng_tcpmss_config_type_fields[]
= NG_TCPMSS_CONFIG_INFO;
static const struct ng_parse_type ng_tcpmss_config_type = {
&ng_parse_struct_type,
ng_tcpmss_config_type_fields
};
/* List of commands and how to convert arguments to/from ASCII. */
static const struct ng_cmdlist ng_tcpmss_cmds[] = {
{
NGM_TCPMSS_COOKIE,
NGM_TCPMSS_GET_STATS,
"getstats",
&ng_parse_hookbuf_type,
&ng_tcpmss_hookstat_type
},
{
NGM_TCPMSS_COOKIE,
NGM_TCPMSS_CLR_STATS,
"clrstats",
&ng_parse_hookbuf_type,
NULL
},
{
NGM_TCPMSS_COOKIE,
NGM_TCPMSS_GETCLR_STATS,
"getclrstats",
&ng_parse_hookbuf_type,
&ng_tcpmss_hookstat_type
},
{
NGM_TCPMSS_COOKIE,
NGM_TCPMSS_CONFIG,
"config",
&ng_tcpmss_config_type,
NULL
},
{ 0 }
};
/* Netgraph type descriptor. */
static struct ng_type ng_tcpmss_typestruct = {
.version = NG_ABI_VERSION,
.name = NG_TCPMSS_NODE_TYPE,
.constructor = ng_tcpmss_constructor,
.rcvmsg = ng_tcpmss_rcvmsg,
.newhook = ng_tcpmss_newhook,
.rcvdata = ng_tcpmss_rcvdata,
.disconnect = ng_tcpmss_disconnect,
.cmdlist = ng_tcpmss_cmds,
};
NETGRAPH_INIT(tcpmss, &ng_tcpmss_typestruct);
#define ERROUT(x) { error = (x); goto done; }
/*
* Node constructor. No special actions required.
*/
static int
ng_tcpmss_constructor(node_p node)
{
return (0);
}
/*
* Add a hook. Any unique name is OK.
*/
static int
ng_tcpmss_newhook(node_p node, hook_p hook, const char *name)
{
hpriv_p priv;
priv = malloc(sizeof(*priv), M_NETGRAPH, M_NOWAIT | M_ZERO);
if (priv == NULL)
return (ENOMEM);
NG_HOOK_SET_PRIVATE(hook, priv);
return (0);
}
/*
* Receive a control message.
*/
static int
ng_tcpmss_rcvmsg
(node_p node, item_p item, hook_p lasthook)
{
struct ng_mesg *msg, *resp = NULL;
int error = 0;
NGI_GET_MSG(item, msg);
switch (msg->header.typecookie) {
case NGM_TCPMSS_COOKIE:
switch (msg->header.cmd) {
case NGM_TCPMSS_GET_STATS:
case NGM_TCPMSS_CLR_STATS:
case NGM_TCPMSS_GETCLR_STATS:
{
hook_p hook;
hpriv_p priv;
/* Check that message is long enough. */
if (msg->header.arglen != NG_HOOKSIZ)
ERROUT(EINVAL);
/* Find this hook. */
hook = ng_findhook(node, (char *)msg->data);
if (hook == NULL)
ERROUT(ENOENT);
priv = NG_HOOK_PRIVATE(hook);
/* Create response. */
if (msg->header.cmd != NGM_TCPMSS_CLR_STATS) {
NG_MKRESPONSE(resp, msg,
sizeof(struct ng_tcpmss_hookstat), M_NOWAIT);
if (resp == NULL)
ERROUT(ENOMEM);
bcopy(&priv->stats, resp->data,
sizeof(struct ng_tcpmss_hookstat));
}
if (msg->header.cmd != NGM_TCPMSS_GET_STATS)
bzero(&priv->stats,
sizeof(struct ng_tcpmss_hookstat));
break;
}
case NGM_TCPMSS_CONFIG:
{
struct ng_tcpmss_config *set;
hook_p in, out;
hpriv_p priv;
/* Check that message is long enough. */
if (msg->header.arglen !=
sizeof(struct ng_tcpmss_config))
ERROUT(EINVAL);
set = (struct ng_tcpmss_config *)msg->data;
in = ng_findhook(node, set->inHook);
out = ng_findhook(node, set->outHook);
if (in == NULL || out == NULL)
ERROUT(ENOENT);
/* Configure MSS hack. */
priv = NG_HOOK_PRIVATE(in);
priv->outHook = out;
priv->stats.maxMSS = set->maxMSS;
break;
}
default:
error = EINVAL;
break;
}
break;
default:
error = EINVAL;
break;
}
done:
NG_RESPOND_MSG(error, node, item, resp);
NG_FREE_MSG(msg);
return (error);
}
/*
* Receive data on a hook, and hack MSS.
*
*/
static int
ng_tcpmss_rcvdata(hook_p hook, item_p item)
{
hpriv_p priv = NG_HOOK_PRIVATE(hook);
struct mbuf *m = NULL;
struct ip *ip;
struct tcphdr *tcp;
int iphlen, tcphlen, pktlen;
int pullup_len = 0;
int error = 0;
/* Drop packets if filter is not configured on this hook. */
if (priv->outHook == NULL)
goto done;
NGI_GET_M(item, m);
/* Update stats on incoming hook. */
pktlen = m->m_pkthdr.len;
priv->stats.Octets += pktlen;
priv->stats.Packets++;
/* Check whether we configured to fix MSS. */
if (priv->stats.maxMSS == 0)
goto send;
#define M_CHECK(length) do { \
pullup_len += length; \
if ((m)->m_pkthdr.len < pullup_len) \
goto send; \
if ((m)->m_len < pullup_len && \
(((m) = m_pullup((m), pullup_len)) == NULL)) \
ERROUT(ENOBUFS); \
} while (0)
/* Check mbuf packet size and arrange for IP header. */
M_CHECK(sizeof(struct ip));
ip = mtod(m, struct ip *);
/* Check IP version. */
if (ip->ip_v != IPVERSION)
ERROUT(EINVAL);
/* Check IP header length. */
iphlen = ip->ip_hl << 2;
if (iphlen < sizeof(struct ip) || iphlen > pktlen )
ERROUT(EINVAL);
/* Check if it is TCP. */
if (!(ip->ip_p == IPPROTO_TCP))
goto send;
/* Check mbuf packet size and arrange for IP+TCP header */
M_CHECK(iphlen - sizeof(struct ip) + sizeof(struct tcphdr));
ip = mtod(m, struct ip *);
tcp = (struct tcphdr *)((caddr_t )ip + iphlen);
/* Check TCP header length. */
tcphlen = tcp->th_off << 2;
if (tcphlen < sizeof(struct tcphdr) || tcphlen > pktlen - iphlen)
ERROUT(EINVAL);
/* Check SYN packet and has options. */
if (!(tcp->th_flags & TH_SYN) || tcphlen == sizeof(struct tcphdr))
goto send;
/* Update SYN stats. */
priv->stats.SYNPkts++;
M_CHECK(tcphlen - sizeof(struct tcphdr));
ip = mtod(m, struct ip *);
tcp = (struct tcphdr *)((caddr_t )ip + iphlen);
#undef M_CHECK
/* Fix MSS and update stats. */
if (correct_mss(tcp, tcphlen, priv->stats.maxMSS,
m->m_pkthdr.csum_flags))
priv->stats.FixedPkts++;
send:
/* Deliver frame out destination hook. */
NG_FWD_NEW_DATA(error, item, priv->outHook, m);
return (error);
done:
NG_FREE_ITEM(item);
NG_FREE_M(m);
return (error);
}
/*
* Hook disconnection.
* We must check all hooks, since they may reference this one.
*/
static int
ng_tcpmss_disconnect(hook_p hook)
{
node_p node = NG_HOOK_NODE(hook);
hook_p hook2;
LIST_FOREACH(hook2, &node->nd_hooks, hk_hooks) {
hpriv_p priv = NG_HOOK_PRIVATE(hook2);
if (priv->outHook == hook)
priv->outHook = NULL;
}
free(NG_HOOK_PRIVATE(hook), M_NETGRAPH);
if (NG_NODE_NUMHOOKS(NG_HOOK_NODE(hook)) == 0)
ng_rmnode_self(NG_HOOK_NODE(hook));
return (0);
}
/*
* Code from tcpmssd.
*/
/*-
* 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 TCPMSS_ADJUST_CHECKSUM(acc, cksum) do { \
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; \
} \
} while (0);
static int
correct_mss(struct tcphdr *tc, int hlen, uint16_t maxmss, int flags)
{
int olen, optlen;
u_char *opt;
int accumulate;
int res = 0;
uint16_t sum;
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;
accumulate = be16dec(opt + 2);
if (accumulate > maxmss) {
if ((flags & CSUM_TCP) == 0) {
accumulate -= maxmss;
sum = be16dec(&tc->th_sum);
TCPMSS_ADJUST_CHECKSUM(accumulate, sum);
be16enc(&tc->th_sum, sum);
}
be16enc(opt + 2, maxmss);
res = 1;
}
}
}
}
return (res);
}
