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Follow RFC 4443 p2.2 and always use own addresses for reflected ICMPv6

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datagrams.

Previously destination address from original datagram was used. That
looked confusing, especially in the traceroute6 output.
Also honor IPSTEALTH kernel option and do TTL/HLIM decrementing only
when stealth mode is disabled.

Reported by:	Marco van Tol <marco at tols org>
Reviewed by:	melifaro
MFC after:	2 weeks
Sponsored by:	Yandex LLC
Differential Revision:	https://reviews.freebsd.org/D22631
This commit is contained in:
Andrey V. Elsukov 2019-12-12 13:28:46 +00:00
parent e63adc105d
commit 2873980947
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=355650
2 changed files with 67 additions and 14 deletions
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1
sys/modules/ipfw_nat64/Makefile
View File

@ -7,6 +7,7 @@ SRCS= ip_fw_nat64.c nat64_translate.c
SRCS+= nat64clat.c nat64clat_control.c
SRCS+= nat64lsn.c nat64lsn_control.c
SRCS+= nat64stl.c nat64stl_control.c
SRCS+= opt_ipstealth.h
CFLAGS+= -I${SRCTOP}/sys/contrib/ck/include

80
sys/netpfil/ipfw/nat64/nat64_translate.c
View File

@ -29,6 +29,8 @@
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ipstealth.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/counter.h>
@ -101,14 +103,39 @@ static const struct nat64_methods nat64_direct = {
.output = nat64_direct_output,
.output_one = nat64_direct_output_one
};
VNET_DEFINE_STATIC(const struct nat64_methods *, nat64out) = &nat64_netisr;
#define V_nat64out VNET(nat64out)
/* These variables should be initialized explicitly on module loading */
VNET_DEFINE_STATIC(const struct nat64_methods *, nat64out);
VNET_DEFINE_STATIC(const int *, nat64ipstealth);
VNET_DEFINE_STATIC(const int *, nat64ip6stealth);
#define V_nat64out VNET(nat64out)
#define V_nat64ipstealth VNET(nat64ipstealth)
#define V_nat64ip6stealth VNET(nat64ip6stealth)
static const int stealth_on = 1;
#ifndef IPSTEALTH
static const int stealth_off = 0;
#endif
void
nat64_set_output_method(int direct)
{
V_nat64out = direct != 0 ? &nat64_direct: &nat64_netisr;
if (direct != 0) {
V_nat64out = &nat64_direct;
#ifdef IPSTEALTH
/* Honor corresponding variables, if IPSTEALTH is defined */
V_nat64ipstealth = &V_ipstealth;
V_nat64ip6stealth = &V_ip6stealth;
#else
/* otherwise we need to decrement HLIM/TTL for direct case */
V_nat64ipstealth = V_nat64ip6stealth = &stealth_off;
#endif
} else {
V_nat64out = &nat64_netisr;
/* Leave TTL/HLIM decrementing to forwarding code */
V_nat64ipstealth = V_nat64ip6stealth = &stealth_on;
}
}
int
@ -486,8 +513,7 @@ nat64_init_ip4hdr(const struct ip6_hdr *ip6, const struct ip6_frag *frag,
ip->ip_tos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
ip->ip_len = htons(sizeof(*ip) + plen);
ip->ip_ttl = ip6->ip6_hlim;
/* Forwarding code will decrement TTL for netisr based output. */
if (V_nat64out == &nat64_direct)
if (*V_nat64ip6stealth == 0)
ip->ip_ttl -= IPV6_HLIMDEC;
ip->ip_sum = 0;
ip->ip_p = (proto == IPPROTO_ICMPV6) ? IPPROTO_ICMP: proto;
@ -623,18 +649,18 @@ nat64_icmp6_reflect(struct mbuf *m, uint8_t type, uint8_t code, uint32_t mtu,
struct icmp6_hdr *icmp6;
struct ip6_hdr *ip6, *oip6;
struct mbuf *n;
int len, plen;
int len, plen, proto;
len = 0;
plen = nat64_getlasthdr(m, &len);
if (plen < 0) {
proto = nat64_getlasthdr(m, &len);
if (proto < 0) {
DPRINTF(DP_DROPS, "mbuf isn't contigious");
goto freeit;
}
/*
* Do not send ICMPv6 in reply to ICMPv6 errors.
*/
if (plen == IPPROTO_ICMPV6) {
if (proto == IPPROTO_ICMPV6) {
if (m->m_len < len + sizeof(*icmp6)) {
DPRINTF(DP_DROPS, "mbuf isn't contigious");
goto freeit;
@ -646,6 +672,21 @@ nat64_icmp6_reflect(struct mbuf *m, uint8_t type, uint8_t code, uint32_t mtu,
"ICMPv6 errors");
goto freeit;
}
/*
* If there are extra headers between IPv6 and ICMPv6,
* strip off them.
*/
if (len > sizeof(struct ip6_hdr)) {
/*
* NOTE: ipfw_chk already did m_pullup() and it is
* expected that data is contigious from the start
* of IPv6 header up to the end of ICMPv6 header.
*/
bcopy(mtod(m, caddr_t),
mtodo(m, len - sizeof(struct ip6_hdr)),
sizeof(struct ip6_hdr));
m_adj(m, len - sizeof(struct ip6_hdr));
}
}
/*
if (icmp6_ratelimit(&ip6->ip6_src, type, code))
@ -687,7 +728,19 @@ nat64_icmp6_reflect(struct mbuf *m, uint8_t type, uint8_t code, uint32_t mtu,
n->m_len = n->m_pkthdr.len = sizeof(struct ip6_hdr) + plen;
oip6 = mtod(n, struct ip6_hdr *);
oip6->ip6_src = ip6->ip6_dst;
/*
* Make IPv6 source address selection for reflected datagram.
* nat64_check_ip6() doesn't allow scoped addresses, therefore
* we use zero scopeid.
*/
if (in6_selectsrc_addr(M_GETFIB(n), &ip6->ip6_src, 0,
n->m_pkthdr.rcvif, &oip6->ip6_src, NULL) != 0) {
/*
* Failed to find proper source address, drop the packet.
*/
m_freem(n);
goto freeit;
}
oip6->ip6_dst = ip6->ip6_src;
oip6->ip6_nxt = IPPROTO_ICMPV6;
oip6->ip6_flow = 0;
@ -1182,7 +1235,7 @@ nat64_do_handle_ip4(struct mbuf *m, struct in6_addr *saddr,
ip = mtod(m, struct ip*);
if (ip->ip_ttl <= IPTTLDEC) {
if (*V_nat64ipstealth == 0 && ip->ip_ttl <= IPTTLDEC) {
nat64_icmp_reflect(m, ICMP_TIMXCEED,
ICMP_TIMXCEED_INTRANS, 0, &cfg->stats, logdata);
return (NAT64RETURN);
@ -1229,8 +1282,7 @@ nat64_do_handle_ip4(struct mbuf *m, struct in6_addr *saddr,
ip6.ip6_flow = htonl(ip->ip_tos << 20);
ip6.ip6_vfc |= IPV6_VERSION;
ip6.ip6_hlim = ip->ip_ttl;
/* Forwarding code will decrement TTL for netisr based output. */
if (V_nat64out == &nat64_direct)
if (*V_nat64ipstealth == 0)
ip6.ip6_hlim -= IPTTLDEC;
ip6.ip6_plen = htons(plen);
ip6.ip6_nxt = (proto == IPPROTO_ICMP) ? IPPROTO_ICMPV6: proto;
@ -1533,7 +1585,7 @@ nat64_do_handle_ip6(struct mbuf *m, uint32_t aaddr, uint16_t aport,
return (NAT64MFREE);
}
if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
if (*V_nat64ip6stealth == 0 && ip6->ip6_hlim <= IPV6_HLIMDEC) {
nat64_icmp6_reflect(m, ICMP6_TIME_EXCEEDED,
ICMP6_TIME_EXCEED_TRANSIT, 0, &cfg->stats, logdata);
return (NAT64RETURN);