330 lines
8.1 KiB
C
330 lines
8.1 KiB
C
/*-
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* Copyright 2005, Gleb Smirnoff <glebius@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/mbuf.h>
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#include <sys/malloc.h>
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#include <sys/ctype.h>
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#include <sys/errno.h>
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#include <sys/syslog.h>
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#include <netinet/in_systm.h>
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#include <netinet/in.h>
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#include <netinet/ip.h>
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#include <netinet/ip_var.h>
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#include <netinet/tcp.h>
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#include <machine/in_cksum.h>
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#include <netinet/libalias/alias.h>
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#include <netgraph/ng_message.h>
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#include <netgraph/ng_parse.h>
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#include <netgraph/ng_nat.h>
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#include <netgraph/netgraph.h>
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static ng_constructor_t ng_nat_constructor;
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static ng_rcvmsg_t ng_nat_rcvmsg;
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static ng_shutdown_t ng_nat_shutdown;
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static ng_newhook_t ng_nat_newhook;
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static ng_rcvdata_t ng_nat_rcvdata;
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static ng_disconnect_t ng_nat_disconnect;
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/* List of commands and how to convert arguments to/from ASCII. */
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static const struct ng_cmdlist ng_nat_cmdlist[] = {
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{
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NGM_NAT_COOKIE,
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NGM_NAT_SET_IPADDR,
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"setaliasaddr",
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&ng_parse_ipaddr_type,
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NULL
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},
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{ 0 }
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};
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/* Netgraph node type descriptor. */
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static struct ng_type typestruct = {
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.version = NG_ABI_VERSION,
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.name = NG_NAT_NODE_TYPE,
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.constructor = ng_nat_constructor,
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.rcvmsg = ng_nat_rcvmsg,
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.shutdown = ng_nat_shutdown,
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.newhook = ng_nat_newhook,
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.rcvdata = ng_nat_rcvdata,
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.disconnect = ng_nat_disconnect,
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.cmdlist = ng_nat_cmdlist,
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};
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NETGRAPH_INIT(nat, &typestruct);
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MODULE_DEPEND(ng_nat, libalias, 1, 1, 1);
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/* Information we store for each node. */
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struct ng_nat_priv {
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node_p node; /* back pointer to node */
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hook_p in; /* hook for demasquerading */
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hook_p out; /* hook for masquerading */
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struct libalias *lib; /* libalias handler */
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uint32_t flags; /* status flags */
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};
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typedef struct ng_nat_priv *priv_p;
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/* Values of flags */
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#define NGNAT_READY 0x1 /* We have everything to work */
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#define NGNAT_ADDR_DEFINED 0x2 /* NGM_NAT_SET_IPADDR happened */
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static int
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ng_nat_constructor(node_p node)
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{
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priv_p priv;
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/* Initialize private descriptor. */
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MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH,
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M_NOWAIT | M_ZERO);
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if (priv == NULL)
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return (ENOMEM);
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/* Init aliasing engine. */
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priv->lib = LibAliasInit(NULL);
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if (priv->lib == NULL) {
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FREE(priv, M_NETGRAPH);
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return (ENOMEM);
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}
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/* Set same ports on. */
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(void )LibAliasSetMode(priv->lib, PKT_ALIAS_SAME_PORTS,
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PKT_ALIAS_SAME_PORTS);
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/* Link structs together. */
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NG_NODE_SET_PRIVATE(node, priv);
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priv->node = node;
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/*
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* libalias is not thread safe, so our node
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* must be single threaded.
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*/
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NG_NODE_FORCE_WRITER(node);
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return (0);
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}
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static int
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ng_nat_newhook(node_p node, hook_p hook, const char *name)
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{
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const priv_p priv = NG_NODE_PRIVATE(node);
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if (strcmp(name, NG_NAT_HOOK_IN) == 0) {
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priv->in = hook;
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} else if (strcmp(name, NG_NAT_HOOK_OUT) == 0) {
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priv->out = hook;
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} else
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return (EINVAL);
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if (priv->out != NULL &&
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priv->in != NULL &&
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priv->flags & NGNAT_ADDR_DEFINED)
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priv->flags |= NGNAT_READY;
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return(0);
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}
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static int
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ng_nat_rcvmsg(node_p node, item_p item, hook_p lasthook)
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{
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const priv_p priv = NG_NODE_PRIVATE(node);
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struct ng_mesg *resp = NULL;
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struct ng_mesg *msg;
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int error = 0;
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NGI_GET_MSG(item, msg);
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switch (msg->header.typecookie) {
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case NGM_NAT_COOKIE:
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switch (msg->header.cmd) {
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case NGM_NAT_SET_IPADDR:
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{
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struct in_addr *const ia = (struct in_addr *)msg->data;
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if (msg->header.arglen < sizeof(*ia)) {
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error = EINVAL;
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break;
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}
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LibAliasSetAddress(priv->lib, *ia);
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priv->flags |= NGNAT_ADDR_DEFINED;
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if (priv->out != NULL &&
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priv->in != NULL)
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priv->flags |= NGNAT_READY;
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}
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break;
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default:
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error = EINVAL; /* unknown command */
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break;
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}
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break;
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default:
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error = EINVAL; /* unknown cookie type */
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break;
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}
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NG_RESPOND_MSG(error, node, item, resp);
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NG_FREE_MSG(msg);
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return (error);
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}
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static int
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ng_nat_rcvdata(hook_p hook, item_p item )
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{
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const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
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struct mbuf *m;
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struct ip *ip;
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int rval, error = 0;
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char *c;
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if (!(priv->flags & NGNAT_READY)) {
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NG_FREE_ITEM(item);
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return (ENXIO);
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}
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m = NGI_M(item);
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if ((m = m_megapullup(m, m->m_pkthdr.len)) == NULL) {
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NGI_M(item) = NULL; /* avoid double free */
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NG_FREE_ITEM(item);
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return (ENOBUFS);
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}
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NGI_M(item) = m;
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c = mtod(m, char *);
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ip = mtod(m, struct ip *);
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KASSERT(m->m_pkthdr.len == ntohs(ip->ip_len),
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("ng_nat: ip_len != m_pkthdr.len"));
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if (hook == priv->in) {
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rval = LibAliasIn(priv->lib, c, MCLBYTES);
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if (rval != PKT_ALIAS_OK &&
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rval != PKT_ALIAS_FOUND_HEADER_FRAGMENT) {
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NG_FREE_ITEM(item);
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return (EINVAL);
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}
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} else if (hook == priv->out) {
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rval = LibAliasOut(priv->lib, c, MCLBYTES);
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if (rval != PKT_ALIAS_OK) {
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NG_FREE_ITEM(item);
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return (EINVAL);
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}
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} else
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panic("ng_nat: unknown hook!\n");
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m->m_pkthdr.len = m->m_len = ntohs(ip->ip_len);
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if ((ip->ip_off & htons(IP_OFFMASK)) == 0 &&
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ip->ip_p == IPPROTO_TCP) {
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struct tcphdr *th = (struct tcphdr *)((caddr_t)ip +
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(ip->ip_hl << 2));
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/*
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* Here is our terrible HACK.
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*
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* Sometimes LibAlias edits contents of TCP packet.
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* In this case it needs to recompute full TCP
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* checksum. However, the problem is that LibAlias
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* doesn't have any idea about checksum offloading
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* in kernel. To workaround this, we do not do
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* checksumming in LibAlias, but only mark the
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* packets in th_x2 field. If we receive a marked
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* packet, we calculate correct checksum for it
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* aware of offloading.
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*
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* Why do I do such a terrible hack instead of
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* recalculating checksum for each packet?
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* Because the previous checksum was not checked!
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* Recalculating checksums for EVERY packet will
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* hide ALL transmission errors. Yes, marked packets
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* still suffer from this problem. But, sigh, natd(8)
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* has this problem, too.
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*/
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if (th->th_x2) {
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th->th_x2 = 0;
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ip->ip_len = ntohs(ip->ip_len);
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th->th_sum = in_pseudo(ip->ip_src.s_addr,
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ip->ip_dst.s_addr, htons(IPPROTO_TCP +
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ip->ip_len - (ip->ip_hl << 2)));
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if ((m->m_pkthdr.csum_flags & CSUM_TCP) == 0) {
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m->m_pkthdr.csum_data = offsetof(struct tcphdr,
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th_sum);
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in_delayed_cksum(m);
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}
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ip->ip_len = htons(ip->ip_len);
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}
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}
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if (hook == priv->in)
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NG_FWD_ITEM_HOOK(error, item, priv->out);
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else
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NG_FWD_ITEM_HOOK(error, item, priv->in);
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return (error);
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}
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static int
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ng_nat_shutdown(node_p node)
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{
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const priv_p priv = NG_NODE_PRIVATE(node);
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NG_NODE_SET_PRIVATE(node, NULL);
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NG_NODE_UNREF(node);
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LibAliasUninit(priv->lib);
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FREE(priv, M_NETGRAPH);
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return (0);
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}
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static int
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ng_nat_disconnect(hook_p hook)
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{
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const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
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priv->flags &= ~NGNAT_READY;
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if (hook == priv->out)
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priv->out = NULL;
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if (hook == priv->in)
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priv->in = NULL;
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if (priv->out == NULL && priv->in == NULL)
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ng_rmnode_self(NG_HOOK_NODE(hook));
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return (0);
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}
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