https://github.com/torvalds/linux
Tip revision: 7d1f9aeff1ee4a20b1aeb377dd0f579fe9647619 authored by Linus Torvalds on 18 January 2013, 03:25:45 UTC
Linux 3.8-rc4
Linux 3.8-rc4
Tip revision: 7d1f9ae
nf_nat_helper.c
/* nf_nat_helper.c - generic support functions for NAT helpers
*
* (C) 2000-2002 Harald Welte <laforge@netfilter.org>
* (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <net/tcp.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_helper.h>
#define DUMP_OFFSET(x) \
pr_debug("offset_before=%d, offset_after=%d, correction_pos=%u\n", \
x->offset_before, x->offset_after, x->correction_pos);
static DEFINE_SPINLOCK(nf_nat_seqofs_lock);
/* Setup TCP sequence correction given this change at this sequence */
static inline void
adjust_tcp_sequence(u32 seq,
int sizediff,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
struct nf_conn_nat *nat = nfct_nat(ct);
struct nf_nat_seq *this_way = &nat->seq[dir];
pr_debug("adjust_tcp_sequence: seq = %u, sizediff = %d\n",
seq, sizediff);
pr_debug("adjust_tcp_sequence: Seq_offset before: ");
DUMP_OFFSET(this_way);
spin_lock_bh(&nf_nat_seqofs_lock);
/* SYN adjust. If it's uninitialized, or this is after last
* correction, record it: we don't handle more than one
* adjustment in the window, but do deal with common case of a
* retransmit */
if (this_way->offset_before == this_way->offset_after ||
before(this_way->correction_pos, seq)) {
this_way->correction_pos = seq;
this_way->offset_before = this_way->offset_after;
this_way->offset_after += sizediff;
}
spin_unlock_bh(&nf_nat_seqofs_lock);
pr_debug("adjust_tcp_sequence: Seq_offset after: ");
DUMP_OFFSET(this_way);
}
/* Get the offset value, for conntrack */
s16 nf_nat_get_offset(const struct nf_conn *ct,
enum ip_conntrack_dir dir,
u32 seq)
{
struct nf_conn_nat *nat = nfct_nat(ct);
struct nf_nat_seq *this_way;
s16 offset;
if (!nat)
return 0;
this_way = &nat->seq[dir];
spin_lock_bh(&nf_nat_seqofs_lock);
offset = after(seq, this_way->correction_pos)
? this_way->offset_after : this_way->offset_before;
spin_unlock_bh(&nf_nat_seqofs_lock);
return offset;
}
/* Frobs data inside this packet, which is linear. */
static void mangle_contents(struct sk_buff *skb,
unsigned int dataoff,
unsigned int match_offset,
unsigned int match_len,
const char *rep_buffer,
unsigned int rep_len)
{
unsigned char *data;
BUG_ON(skb_is_nonlinear(skb));
data = skb_network_header(skb) + dataoff;
/* move post-replacement */
memmove(data + match_offset + rep_len,
data + match_offset + match_len,
skb->tail - (skb->network_header + dataoff +
match_offset + match_len));
/* insert data from buffer */
memcpy(data + match_offset, rep_buffer, rep_len);
/* update skb info */
if (rep_len > match_len) {
pr_debug("nf_nat_mangle_packet: Extending packet by "
"%u from %u bytes\n", rep_len - match_len, skb->len);
skb_put(skb, rep_len - match_len);
} else {
pr_debug("nf_nat_mangle_packet: Shrinking packet from "
"%u from %u bytes\n", match_len - rep_len, skb->len);
__skb_trim(skb, skb->len + rep_len - match_len);
}
if (nf_ct_l3num((struct nf_conn *)skb->nfct) == NFPROTO_IPV4) {
/* fix IP hdr checksum information */
ip_hdr(skb)->tot_len = htons(skb->len);
ip_send_check(ip_hdr(skb));
} else
ipv6_hdr(skb)->payload_len =
htons(skb->len - sizeof(struct ipv6hdr));
}
/* Unusual, but possible case. */
static int enlarge_skb(struct sk_buff *skb, unsigned int extra)
{
if (skb->len + extra > 65535)
return 0;
if (pskb_expand_head(skb, 0, extra - skb_tailroom(skb), GFP_ATOMIC))
return 0;
return 1;
}
void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
__be32 seq, s16 off)
{
if (!off)
return;
set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
adjust_tcp_sequence(ntohl(seq), off, ct, ctinfo);
nf_conntrack_event_cache(IPCT_NATSEQADJ, ct);
}
EXPORT_SYMBOL_GPL(nf_nat_set_seq_adjust);
void nf_nat_tcp_seq_adjust(struct sk_buff *skb, struct nf_conn *ct,
u32 ctinfo, int off)
{
const struct tcphdr *th;
if (nf_ct_protonum(ct) != IPPROTO_TCP)
return;
th = (struct tcphdr *)(skb_network_header(skb)+ ip_hdrlen(skb));
nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off);
}
EXPORT_SYMBOL_GPL(nf_nat_tcp_seq_adjust);
/* Generic function for mangling variable-length address changes inside
* NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
* command in FTP).
*
* Takes care about all the nasty sequence number changes, checksumming,
* skb enlargement, ...
*
* */
int __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
unsigned int protoff,
unsigned int match_offset,
unsigned int match_len,
const char *rep_buffer,
unsigned int rep_len, bool adjust)
{
const struct nf_nat_l3proto *l3proto;
struct tcphdr *tcph;
int oldlen, datalen;
if (!skb_make_writable(skb, skb->len))
return 0;
if (rep_len > match_len &&
rep_len - match_len > skb_tailroom(skb) &&
!enlarge_skb(skb, rep_len - match_len))
return 0;
SKB_LINEAR_ASSERT(skb);
tcph = (void *)skb->data + protoff;
oldlen = skb->len - protoff;
mangle_contents(skb, protoff + tcph->doff*4,
match_offset, match_len, rep_buffer, rep_len);
datalen = skb->len - protoff;
l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct));
l3proto->csum_recalc(skb, IPPROTO_TCP, tcph, &tcph->check,
datalen, oldlen);
if (adjust && rep_len != match_len)
nf_nat_set_seq_adjust(ct, ctinfo, tcph->seq,
(int)rep_len - (int)match_len);
return 1;
}
EXPORT_SYMBOL(__nf_nat_mangle_tcp_packet);
/* Generic function for mangling variable-length address changes inside
* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
* command in the Amanda protocol)
*
* Takes care about all the nasty sequence number changes, checksumming,
* skb enlargement, ...
*
* XXX - This function could be merged with nf_nat_mangle_tcp_packet which
* should be fairly easy to do.
*/
int
nf_nat_mangle_udp_packet(struct sk_buff *skb,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
unsigned int protoff,
unsigned int match_offset,
unsigned int match_len,
const char *rep_buffer,
unsigned int rep_len)
{
const struct nf_nat_l3proto *l3proto;
struct udphdr *udph;
int datalen, oldlen;
if (!skb_make_writable(skb, skb->len))
return 0;
if (rep_len > match_len &&
rep_len - match_len > skb_tailroom(skb) &&
!enlarge_skb(skb, rep_len - match_len))
return 0;
udph = (void *)skb->data + protoff;
oldlen = skb->len - protoff;
mangle_contents(skb, protoff + sizeof(*udph),
match_offset, match_len, rep_buffer, rep_len);
/* update the length of the UDP packet */
datalen = skb->len - protoff;
udph->len = htons(datalen);
/* fix udp checksum if udp checksum was previously calculated */
if (!udph->check && skb->ip_summed != CHECKSUM_PARTIAL)
return 1;
l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct));
l3proto->csum_recalc(skb, IPPROTO_UDP, udph, &udph->check,
datalen, oldlen);
return 1;
}
EXPORT_SYMBOL(nf_nat_mangle_udp_packet);
/* Adjust one found SACK option including checksum correction */
static void
sack_adjust(struct sk_buff *skb,
struct tcphdr *tcph,
unsigned int sackoff,
unsigned int sackend,
struct nf_nat_seq *natseq)
{
while (sackoff < sackend) {
struct tcp_sack_block_wire *sack;
__be32 new_start_seq, new_end_seq;
sack = (void *)skb->data + sackoff;
if (after(ntohl(sack->start_seq) - natseq->offset_before,
natseq->correction_pos))
new_start_seq = htonl(ntohl(sack->start_seq)
- natseq->offset_after);
else
new_start_seq = htonl(ntohl(sack->start_seq)
- natseq->offset_before);
if (after(ntohl(sack->end_seq) - natseq->offset_before,
natseq->correction_pos))
new_end_seq = htonl(ntohl(sack->end_seq)
- natseq->offset_after);
else
new_end_seq = htonl(ntohl(sack->end_seq)
- natseq->offset_before);
pr_debug("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
ntohl(sack->start_seq), new_start_seq,
ntohl(sack->end_seq), new_end_seq);
inet_proto_csum_replace4(&tcph->check, skb,
sack->start_seq, new_start_seq, 0);
inet_proto_csum_replace4(&tcph->check, skb,
sack->end_seq, new_end_seq, 0);
sack->start_seq = new_start_seq;
sack->end_seq = new_end_seq;
sackoff += sizeof(*sack);
}
}
/* TCP SACK sequence number adjustment */
static inline unsigned int
nf_nat_sack_adjust(struct sk_buff *skb,
unsigned int protoff,
struct tcphdr *tcph,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
unsigned int dir, optoff, optend;
struct nf_conn_nat *nat = nfct_nat(ct);
optoff = protoff + sizeof(struct tcphdr);
optend = protoff + tcph->doff * 4;
if (!skb_make_writable(skb, optend))
return 0;
dir = CTINFO2DIR(ctinfo);
while (optoff < optend) {
/* Usually: option, length. */
unsigned char *op = skb->data + optoff;
switch (op[0]) {
case TCPOPT_EOL:
return 1;
case TCPOPT_NOP:
optoff++;
continue;
default:
/* no partial options */
if (optoff + 1 == optend ||
optoff + op[1] > optend ||
op[1] < 2)
return 0;
if (op[0] == TCPOPT_SACK &&
op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
sack_adjust(skb, tcph, optoff+2,
optoff+op[1], &nat->seq[!dir]);
optoff += op[1];
}
}
return 1;
}
/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
int
nf_nat_seq_adjust(struct sk_buff *skb,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
unsigned int protoff)
{
struct tcphdr *tcph;
int dir;
__be32 newseq, newack;
s16 seqoff, ackoff;
struct nf_conn_nat *nat = nfct_nat(ct);
struct nf_nat_seq *this_way, *other_way;
dir = CTINFO2DIR(ctinfo);
this_way = &nat->seq[dir];
other_way = &nat->seq[!dir];
if (!skb_make_writable(skb, protoff + sizeof(*tcph)))
return 0;
tcph = (void *)skb->data + protoff;
if (after(ntohl(tcph->seq), this_way->correction_pos))
seqoff = this_way->offset_after;
else
seqoff = this_way->offset_before;
if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
other_way->correction_pos))
ackoff = other_way->offset_after;
else
ackoff = other_way->offset_before;
newseq = htonl(ntohl(tcph->seq) + seqoff);
newack = htonl(ntohl(tcph->ack_seq) - ackoff);
inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, 0);
inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0);
pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n",
ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
ntohl(newack));
tcph->seq = newseq;
tcph->ack_seq = newack;
return nf_nat_sack_adjust(skb, protoff, tcph, ct, ctinfo);
}
/* Setup NAT on this expected conntrack so it follows master. */
/* If we fail to get a free NAT slot, we'll get dropped on confirm */
void nf_nat_follow_master(struct nf_conn *ct,
struct nf_conntrack_expect *exp)
{
struct nf_nat_range range;
/* This must be a fresh one. */
BUG_ON(ct->status & IPS_NAT_DONE_MASK);
/* Change src to where master sends to */
range.flags = NF_NAT_RANGE_MAP_IPS;
range.min_addr = range.max_addr
= ct->master->tuplehash[!exp->dir].tuple.dst.u3;
nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
/* For DST manip, map port here to where it's expected. */
range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
range.min_proto = range.max_proto = exp->saved_proto;
range.min_addr = range.max_addr
= ct->master->tuplehash[!exp->dir].tuple.src.u3;
nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
}
EXPORT_SYMBOL(nf_nat_follow_master);