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![Simon Horman](/assets/img/avatar_default.png)
This corrects an regression introduced by "net: Use 16bits for *_headers fields of struct skbuff" when NET_SKBUFF_DATA_USES_OFFSET is not set. In that case skb->tail will be a pointer whereas skb->network_header will be an offset from head. This is corrected by using wrappers that ensure that calculations are always made using pointers. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Reported-by: Chen Gang <gang.chen@asianux.com> Signed-off-by: Simon Horman <horms@verge.net.au> Signed-off-by: David S. Miller <davem@davemloft.net>
436 lines
12 KiB
C
436 lines
12 KiB
C
/* nf_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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* (C) 2007-2012 Patrick McHardy <kaber@trash.net>
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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/gfp.h>
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#include <linux/types.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/tcp.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_ecache.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_l3proto.h>
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#include <net/netfilter/nf_nat_l4proto.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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#define DUMP_OFFSET(x) \
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pr_debug("offset_before=%d, offset_after=%d, correction_pos=%u\n", \
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x->offset_before, x->offset_after, x->correction_pos);
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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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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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struct nf_conn_nat *nat = nfct_nat(ct);
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struct nf_nat_seq *this_way = &nat->seq[dir];
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pr_debug("adjust_tcp_sequence: seq = %u, sizediff = %d\n",
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seq, sizediff);
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pr_debug("adjust_tcp_sequence: 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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pr_debug("adjust_tcp_sequence: Seq_offset after: ");
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DUMP_OFFSET(this_way);
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}
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/* Get the offset value, for conntrack */
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s16 nf_nat_get_offset(const struct nf_conn *ct,
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enum ip_conntrack_dir dir,
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u32 seq)
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{
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struct nf_conn_nat *nat = nfct_nat(ct);
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struct nf_nat_seq *this_way;
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s16 offset;
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if (!nat)
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return 0;
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this_way = &nat->seq[dir];
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spin_lock_bh(&nf_nat_seqofs_lock);
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offset = after(seq, this_way->correction_pos)
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? this_way->offset_after : this_way->offset_before;
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spin_unlock_bh(&nf_nat_seqofs_lock);
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return offset;
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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 = skb_network_header(skb) + 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_pointer(skb) - (skb_network_header(skb) + dataoff +
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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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pr_debug("nf_nat_mangle_packet: Extending packet by "
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"%u from %u bytes\n", rep_len - match_len, skb->len);
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skb_put(skb, rep_len - match_len);
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} else {
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pr_debug("nf_nat_mangle_packet: Shrinking packet from "
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"%u from %u bytes\n", match_len - rep_len, skb->len);
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__skb_trim(skb, skb->len + rep_len - match_len);
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}
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if (nf_ct_l3num((struct nf_conn *)skb->nfct) == NFPROTO_IPV4) {
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/* fix IP hdr checksum information */
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ip_hdr(skb)->tot_len = htons(skb->len);
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ip_send_check(ip_hdr(skb));
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} else
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ipv6_hdr(skb)->payload_len =
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htons(skb->len - sizeof(struct ipv6hdr));
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}
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/* Unusual, but possible case. */
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static int enlarge_skb(struct sk_buff *skb, unsigned int extra)
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{
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if (skb->len + extra > 65535)
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return 0;
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if (pskb_expand_head(skb, 0, extra - skb_tailroom(skb), GFP_ATOMIC))
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return 0;
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return 1;
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}
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void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
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__be32 seq, s16 off)
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{
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if (!off)
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return;
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set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
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adjust_tcp_sequence(ntohl(seq), off, ct, ctinfo);
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nf_conntrack_event_cache(IPCT_NATSEQADJ, ct);
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}
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EXPORT_SYMBOL_GPL(nf_nat_set_seq_adjust);
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void nf_nat_tcp_seq_adjust(struct sk_buff *skb, struct nf_conn *ct,
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u32 ctinfo, int off)
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{
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const struct tcphdr *th;
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if (nf_ct_protonum(ct) != IPPROTO_TCP)
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return;
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th = (struct tcphdr *)(skb_network_header(skb)+ ip_hdrlen(skb));
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nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off);
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}
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EXPORT_SYMBOL_GPL(nf_nat_tcp_seq_adjust);
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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 __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int protoff,
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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, bool adjust)
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{
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const struct nf_nat_l3proto *l3proto;
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struct tcphdr *tcph;
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int oldlen, datalen;
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if (!skb_make_writable(skb, skb->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(skb) &&
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!enlarge_skb(skb, rep_len - match_len))
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return 0;
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SKB_LINEAR_ASSERT(skb);
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tcph = (void *)skb->data + protoff;
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oldlen = skb->len - protoff;
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mangle_contents(skb, protoff + tcph->doff*4,
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match_offset, match_len, rep_buffer, rep_len);
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datalen = skb->len - protoff;
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l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct));
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l3proto->csum_recalc(skb, IPPROTO_TCP, tcph, &tcph->check,
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datalen, oldlen);
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if (adjust && rep_len != match_len)
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nf_nat_set_seq_adjust(ct, ctinfo, tcph->seq,
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(int)rep_len - (int)match_len);
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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 *skb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int protoff,
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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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const struct nf_nat_l3proto *l3proto;
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struct udphdr *udph;
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int datalen, oldlen;
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if (!skb_make_writable(skb, skb->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(skb) &&
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!enlarge_skb(skb, rep_len - match_len))
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return 0;
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udph = (void *)skb->data + protoff;
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oldlen = skb->len - protoff;
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mangle_contents(skb, protoff + 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 = skb->len - protoff;
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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 && skb->ip_summed != CHECKSUM_PARTIAL)
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return 1;
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l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct));
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l3proto->csum_recalc(skb, IPPROTO_UDP, udph, &udph->check,
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datalen, oldlen);
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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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pr_debug("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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inet_proto_csum_replace4(&tcph->check, skb,
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sack->start_seq, new_start_seq, 0);
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inet_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 *skb,
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unsigned int protoff,
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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 = protoff + sizeof(struct tcphdr);
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optend = protoff + tcph->doff * 4;
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if (!skb_make_writable(skb, 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 = skb->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(skb, tcph, optoff+2,
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optoff+op[1], &nat->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 *skb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int protoff)
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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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s16 seqoff, ackoff;
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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->seq[dir];
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other_way = &nat->seq[!dir];
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if (!skb_make_writable(skb, protoff + sizeof(*tcph)))
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return 0;
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tcph = (void *)skb->data + protoff;
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if (after(ntohl(tcph->seq), this_way->correction_pos))
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seqoff = this_way->offset_after;
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else
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seqoff = 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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ackoff = other_way->offset_after;
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else
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ackoff = other_way->offset_before;
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newseq = htonl(ntohl(tcph->seq) + seqoff);
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newack = htonl(ntohl(tcph->ack_seq) - ackoff);
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inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, 0);
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inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0);
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pr_debug("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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return nf_nat_sack_adjust(skb, protoff, tcph, ct, ctinfo);
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}
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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 = NF_NAT_RANGE_MAP_IPS;
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range.min_addr = range.max_addr
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= ct->master->tuplehash[!exp->dir].tuple.dst.u3;
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nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
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/* For DST manip, map port here to where it's expected. */
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range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
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range.min_proto = range.max_proto = exp->saved_proto;
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range.min_addr = range.max_addr
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= ct->master->tuplehash[!exp->dir].tuple.src.u3;
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nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
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}
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EXPORT_SYMBOL(nf_nat_follow_master);
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