Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Signed-off-by: David S. Miller <davem@davemloft.net>
434 lines
12 KiB
C
434 lines
12 KiB
C
/* ip_nat_helper.c - generic support functions for NAT helpers
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*
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* (C) 2000-2002 Harald Welte <laforge@netfilter.org>
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* (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/kmod.h>
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#include <linux/types.h>
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#include <linux/timer.h>
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#include <linux/skbuff.h>
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#include <linux/tcp.h>
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#include <linux/udp.h>
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#include <net/checksum.h>
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#include <net/tcp.h>
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#include <linux/netfilter_ipv4.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_expect.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_nat_protocol.h>
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#include <net/netfilter/nf_nat_core.h>
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#include <net/netfilter/nf_nat_helper.h>
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#if 0
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#define DEBUGP printk
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#define DUMP_OFFSET(x) printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos);
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#else
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#define DEBUGP(format, args...)
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#define DUMP_OFFSET(x)
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#endif
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static DEFINE_SPINLOCK(nf_nat_seqofs_lock);
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/* Setup TCP sequence correction given this change at this sequence */
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static inline void
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adjust_tcp_sequence(u32 seq,
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int sizediff,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo)
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{
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int dir;
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struct nf_nat_seq *this_way, *other_way;
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struct nf_conn_nat *nat = nfct_nat(ct);
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DEBUGP("nf_nat_resize_packet: old_size = %u, new_size = %u\n",
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(*skb)->len, new_size);
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dir = CTINFO2DIR(ctinfo);
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this_way = &nat->info.seq[dir];
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other_way = &nat->info.seq[!dir];
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DEBUGP("nf_nat_resize_packet: Seq_offset before: ");
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DUMP_OFFSET(this_way);
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spin_lock_bh(&nf_nat_seqofs_lock);
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/* SYN adjust. If it's uninitialized, or this is after last
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* correction, record it: we don't handle more than one
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* adjustment in the window, but do deal with common case of a
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* retransmit */
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if (this_way->offset_before == this_way->offset_after ||
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before(this_way->correction_pos, seq)) {
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this_way->correction_pos = seq;
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this_way->offset_before = this_way->offset_after;
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this_way->offset_after += sizediff;
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}
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spin_unlock_bh(&nf_nat_seqofs_lock);
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DEBUGP("nf_nat_resize_packet: Seq_offset after: ");
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DUMP_OFFSET(this_way);
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}
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/* Frobs data inside this packet, which is linear. */
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static void mangle_contents(struct sk_buff *skb,
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unsigned int dataoff,
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unsigned int match_offset,
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unsigned int match_len,
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const char *rep_buffer,
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unsigned int rep_len)
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{
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unsigned char *data;
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BUG_ON(skb_is_nonlinear(skb));
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data = (unsigned char *)skb->nh.iph + dataoff;
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/* move post-replacement */
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memmove(data + match_offset + rep_len,
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data + match_offset + match_len,
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skb->tail - (data + match_offset + match_len));
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/* insert data from buffer */
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memcpy(data + match_offset, rep_buffer, rep_len);
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/* update skb info */
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if (rep_len > match_len) {
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DEBUGP("nf_nat_mangle_packet: Extending packet by "
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"%u from %u bytes\n", rep_len - match_len,
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skb->len);
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skb_put(skb, rep_len - match_len);
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} else {
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DEBUGP("nf_nat_mangle_packet: Shrinking packet from "
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"%u from %u bytes\n", match_len - rep_len,
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skb->len);
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__skb_trim(skb, skb->len + rep_len - match_len);
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}
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/* fix IP hdr checksum information */
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skb->nh.iph->tot_len = htons(skb->len);
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ip_send_check(skb->nh.iph);
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}
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/* Unusual, but possible case. */
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static int enlarge_skb(struct sk_buff **pskb, unsigned int extra)
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{
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struct sk_buff *nskb;
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if ((*pskb)->len + extra > 65535)
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return 0;
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nskb = skb_copy_expand(*pskb, skb_headroom(*pskb), extra, GFP_ATOMIC);
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if (!nskb)
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return 0;
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/* Transfer socket to new skb. */
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if ((*pskb)->sk)
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skb_set_owner_w(nskb, (*pskb)->sk);
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kfree_skb(*pskb);
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*pskb = nskb;
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return 1;
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}
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/* Generic function for mangling variable-length address changes inside
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* NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
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* command in FTP).
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*
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* Takes care about all the nasty sequence number changes, checksumming,
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* skb enlargement, ...
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*
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* */
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int
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nf_nat_mangle_tcp_packet(struct sk_buff **pskb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int match_offset,
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unsigned int match_len,
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const char *rep_buffer,
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unsigned int rep_len)
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{
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struct iphdr *iph;
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struct tcphdr *tcph;
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int oldlen, datalen;
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if (!skb_make_writable(pskb, (*pskb)->len))
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return 0;
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if (rep_len > match_len &&
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rep_len - match_len > skb_tailroom(*pskb) &&
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!enlarge_skb(pskb, rep_len - match_len))
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return 0;
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SKB_LINEAR_ASSERT(*pskb);
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iph = (*pskb)->nh.iph;
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tcph = (void *)iph + iph->ihl*4;
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oldlen = (*pskb)->len - iph->ihl*4;
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mangle_contents(*pskb, iph->ihl*4 + tcph->doff*4,
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match_offset, match_len, rep_buffer, rep_len);
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datalen = (*pskb)->len - iph->ihl*4;
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if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
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tcph->check = 0;
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tcph->check = tcp_v4_check(datalen,
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iph->saddr, iph->daddr,
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csum_partial((char *)tcph,
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datalen, 0));
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} else
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nf_proto_csum_replace2(&tcph->check, *pskb,
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htons(oldlen), htons(datalen), 1);
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if (rep_len != match_len) {
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set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
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adjust_tcp_sequence(ntohl(tcph->seq),
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(int)rep_len - (int)match_len,
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ct, ctinfo);
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/* Tell TCP window tracking about seq change */
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nf_conntrack_tcp_update(*pskb, (*pskb)->nh.iph->ihl*4,
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ct, CTINFO2DIR(ctinfo));
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}
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return 1;
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}
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EXPORT_SYMBOL(nf_nat_mangle_tcp_packet);
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/* Generic function for mangling variable-length address changes inside
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* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
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* command in the Amanda protocol)
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*
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* Takes care about all the nasty sequence number changes, checksumming,
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* skb enlargement, ...
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*
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* XXX - This function could be merged with nf_nat_mangle_tcp_packet which
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* should be fairly easy to do.
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*/
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int
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nf_nat_mangle_udp_packet(struct sk_buff **pskb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int match_offset,
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unsigned int match_len,
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const char *rep_buffer,
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unsigned int rep_len)
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{
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struct iphdr *iph;
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struct udphdr *udph;
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int datalen, oldlen;
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/* UDP helpers might accidentally mangle the wrong packet */
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iph = (*pskb)->nh.iph;
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if ((*pskb)->len < iph->ihl*4 + sizeof(*udph) +
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match_offset + match_len)
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return 0;
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if (!skb_make_writable(pskb, (*pskb)->len))
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return 0;
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if (rep_len > match_len &&
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rep_len - match_len > skb_tailroom(*pskb) &&
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!enlarge_skb(pskb, rep_len - match_len))
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return 0;
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iph = (*pskb)->nh.iph;
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udph = (void *)iph + iph->ihl*4;
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oldlen = (*pskb)->len - iph->ihl*4;
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mangle_contents(*pskb, iph->ihl*4 + sizeof(*udph),
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match_offset, match_len, rep_buffer, rep_len);
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/* update the length of the UDP packet */
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datalen = (*pskb)->len - iph->ihl*4;
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udph->len = htons(datalen);
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/* fix udp checksum if udp checksum was previously calculated */
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if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL)
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return 1;
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if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
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udph->check = 0;
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udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
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datalen, IPPROTO_UDP,
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csum_partial((char *)udph,
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datalen, 0));
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if (!udph->check)
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udph->check = CSUM_MANGLED_0;
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} else
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nf_proto_csum_replace2(&udph->check, *pskb,
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htons(oldlen), htons(datalen), 1);
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return 1;
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}
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EXPORT_SYMBOL(nf_nat_mangle_udp_packet);
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/* Adjust one found SACK option including checksum correction */
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static void
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sack_adjust(struct sk_buff *skb,
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struct tcphdr *tcph,
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unsigned int sackoff,
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unsigned int sackend,
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struct nf_nat_seq *natseq)
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{
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while (sackoff < sackend) {
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struct tcp_sack_block_wire *sack;
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__be32 new_start_seq, new_end_seq;
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sack = (void *)skb->data + sackoff;
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if (after(ntohl(sack->start_seq) - natseq->offset_before,
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natseq->correction_pos))
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new_start_seq = htonl(ntohl(sack->start_seq)
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- natseq->offset_after);
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else
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new_start_seq = htonl(ntohl(sack->start_seq)
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- natseq->offset_before);
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if (after(ntohl(sack->end_seq) - natseq->offset_before,
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natseq->correction_pos))
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new_end_seq = htonl(ntohl(sack->end_seq)
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- natseq->offset_after);
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else
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new_end_seq = htonl(ntohl(sack->end_seq)
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- natseq->offset_before);
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DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
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ntohl(sack->start_seq), new_start_seq,
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ntohl(sack->end_seq), new_end_seq);
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nf_proto_csum_replace4(&tcph->check, skb,
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sack->start_seq, new_start_seq, 0);
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nf_proto_csum_replace4(&tcph->check, skb,
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sack->end_seq, new_end_seq, 0);
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sack->start_seq = new_start_seq;
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sack->end_seq = new_end_seq;
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sackoff += sizeof(*sack);
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}
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}
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/* TCP SACK sequence number adjustment */
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static inline unsigned int
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nf_nat_sack_adjust(struct sk_buff **pskb,
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struct tcphdr *tcph,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo)
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{
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unsigned int dir, optoff, optend;
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struct nf_conn_nat *nat = nfct_nat(ct);
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optoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct tcphdr);
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optend = (*pskb)->nh.iph->ihl*4 + tcph->doff*4;
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if (!skb_make_writable(pskb, optend))
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return 0;
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dir = CTINFO2DIR(ctinfo);
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while (optoff < optend) {
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/* Usually: option, length. */
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unsigned char *op = (*pskb)->data + optoff;
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switch (op[0]) {
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case TCPOPT_EOL:
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return 1;
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case TCPOPT_NOP:
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optoff++;
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continue;
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default:
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/* no partial options */
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if (optoff + 1 == optend ||
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optoff + op[1] > optend ||
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op[1] < 2)
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return 0;
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if (op[0] == TCPOPT_SACK &&
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op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
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((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
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sack_adjust(*pskb, tcph, optoff+2,
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optoff+op[1],
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&nat->info.seq[!dir]);
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optoff += op[1];
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}
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}
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return 1;
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}
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/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
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int
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nf_nat_seq_adjust(struct sk_buff **pskb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo)
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{
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struct tcphdr *tcph;
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int dir;
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__be32 newseq, newack;
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struct nf_conn_nat *nat = nfct_nat(ct);
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struct nf_nat_seq *this_way, *other_way;
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dir = CTINFO2DIR(ctinfo);
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this_way = &nat->info.seq[dir];
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other_way = &nat->info.seq[!dir];
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if (!skb_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph)))
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return 0;
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tcph = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
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if (after(ntohl(tcph->seq), this_way->correction_pos))
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newseq = htonl(ntohl(tcph->seq) + this_way->offset_after);
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else
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newseq = htonl(ntohl(tcph->seq) + this_way->offset_before);
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if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
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other_way->correction_pos))
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newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after);
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else
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newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before);
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nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0);
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nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0);
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DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
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ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
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ntohl(newack));
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tcph->seq = newseq;
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tcph->ack_seq = newack;
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if (!nf_nat_sack_adjust(pskb, tcph, ct, ctinfo))
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return 0;
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nf_conntrack_tcp_update(*pskb, (*pskb)->nh.iph->ihl*4, ct, dir);
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return 1;
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}
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EXPORT_SYMBOL(nf_nat_seq_adjust);
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/* Setup NAT on this expected conntrack so it follows master. */
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/* If we fail to get a free NAT slot, we'll get dropped on confirm */
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void nf_nat_follow_master(struct nf_conn *ct,
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struct nf_conntrack_expect *exp)
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{
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struct nf_nat_range range;
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/* This must be a fresh one. */
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BUG_ON(ct->status & IPS_NAT_DONE_MASK);
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/* Change src to where master sends to */
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range.flags = IP_NAT_RANGE_MAP_IPS;
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range.min_ip = range.max_ip
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= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
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/* hook doesn't matter, but it has to do source manip */
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nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
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/* For DST manip, map port here to where it's expected. */
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range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
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range.min = range.max = exp->saved_proto;
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range.min_ip = range.max_ip
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= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
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/* hook doesn't matter, but it has to do destination manip */
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nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
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}
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EXPORT_SYMBOL(nf_nat_follow_master);
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