1 files changed, 433 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
new file mode 100644
index 00000000000..98fbfc84d18
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -0,0 +1,433 @@
+/* ip_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/kmod.h>
+#include <linux/types.h>
+#include <linux/timer.h>
+#include <linux/skbuff.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <net/checksum.h>
+#include <net/tcp.h>
+
+#include <linux/netfilter_ipv4.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_protocol.h>
+#include <net/netfilter/nf_nat_core.h>
+#include <net/netfilter/nf_nat_helper.h>
+
+#if 0
+#define DEBUGP printk
+#define DUMP_OFFSET(x)	printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos);
+#else
+#define DEBUGP(format, args...)
+#define DUMP_OFFSET(x)
+#endif
+
+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)
+{
+	int dir;
+	struct nf_nat_seq *this_way, *other_way;
+	struct nf_conn_nat *nat = nfct_nat(ct);
+
+	DEBUGP("nf_nat_resize_packet: old_size = %u, new_size = %u\n",
+		(*skb)->len, new_size);
+
+	dir = CTINFO2DIR(ctinfo);
+
+	this_way = &nat->info.seq[dir];
+	other_way = &nat->info.seq[!dir];
+
+	DEBUGP("nf_nat_resize_packet: 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);
+
+	DEBUGP("nf_nat_resize_packet: Seq_offset after: ");
+	DUMP_OFFSET(this_way);
+}
+
+/* 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 = (unsigned char *)skb->nh.iph + dataoff;
+
+	/* move post-replacement */
+	memmove(data + match_offset + rep_len,
+		data + match_offset + match_len,
+		skb->tail - (data + match_offset + match_len));
+
+	/* insert data from buffer */
+	memcpy(data + match_offset, rep_buffer, rep_len);
+
+	/* update skb info */
+	if (rep_len > match_len) {
+		DEBUGP("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 {
+		DEBUGP("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);
+	}
+
+	/* fix IP hdr checksum information */
+	skb->nh.iph->tot_len = htons(skb->len);
+	ip_send_check(skb->nh.iph);
+}
+
+/* Unusual, but possible case. */
+static int enlarge_skb(struct sk_buff **pskb, unsigned int extra)
+{
+	struct sk_buff *nskb;
+
+	if ((*pskb)->len + extra > 65535)
+		return 0;
+
+	nskb = skb_copy_expand(*pskb, skb_headroom(*pskb), extra, GFP_ATOMIC);
+	if (!nskb)
+		return 0;
+
+	/* Transfer socket to new skb. */
+	if ((*pskb)->sk)
+		skb_set_owner_w(nskb, (*pskb)->sk);
+	kfree_skb(*pskb);
+	*pskb = nskb;
+	return 1;
+}
+
+/* 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 **pskb,
+			 struct nf_conn *ct,
+			 enum ip_conntrack_info ctinfo,
+			 unsigned int match_offset,
+			 unsigned int match_len,
+			 const char *rep_buffer,
+			 unsigned int rep_len)
+{
+	struct iphdr *iph;
+	struct tcphdr *tcph;
+	int oldlen, datalen;
+
+	if (!skb_make_writable(pskb, (*pskb)->len))
+		return 0;
+
+	if (rep_len > match_len &&
+	    rep_len - match_len > skb_tailroom(*pskb) &&
+	    !enlarge_skb(pskb, rep_len - match_len))
+		return 0;
+
+	SKB_LINEAR_ASSERT(*pskb);
+
+	iph = (*pskb)->nh.iph;
+	tcph = (void *)iph + iph->ihl*4;
+
+	oldlen = (*pskb)->len - iph->ihl*4;
+	mangle_contents(*pskb, iph->ihl*4 + tcph->doff*4,
+			match_offset, match_len, rep_buffer, rep_len);
+
+	datalen = (*pskb)->len - iph->ihl*4;
+	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
+		tcph->check = 0;
+		tcph->check = tcp_v4_check(tcph, datalen,
+					   iph->saddr, iph->daddr,
+					   csum_partial((char *)tcph,
+					   		datalen, 0));
+	} else
+		nf_proto_csum_replace2(&tcph->check, *pskb,
+				       htons(oldlen), htons(datalen), 1);
+
+	if (rep_len != match_len) {
+		set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
+		adjust_tcp_sequence(ntohl(tcph->seq),
+				    (int)rep_len - (int)match_len,
+				    ct, ctinfo);
+		/* Tell TCP window tracking about seq change */
+		nf_conntrack_tcp_update(*pskb, (*pskb)->nh.iph->ihl*4,
+					ct, CTINFO2DIR(ctinfo));
+	}
+	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 **pskb,
+			 struct nf_conn *ct,
+			 enum ip_conntrack_info ctinfo,
+			 unsigned int match_offset,
+			 unsigned int match_len,
+			 const char *rep_buffer,
+			 unsigned int rep_len)
+{
+	struct iphdr *iph;
+	struct udphdr *udph;
+	int datalen, oldlen;
+
+	/* UDP helpers might accidentally mangle the wrong packet */
+	iph = (*pskb)->nh.iph;
+	if ((*pskb)->len < iph->ihl*4 + sizeof(*udph) +
+	                       match_offset + match_len)
+		return 0;
+
+	if (!skb_make_writable(pskb, (*pskb)->len))
+		return 0;
+
+	if (rep_len > match_len &&
+	    rep_len - match_len > skb_tailroom(*pskb) &&
+	    !enlarge_skb(pskb, rep_len - match_len))
+		return 0;
+
+	iph = (*pskb)->nh.iph;
+	udph = (void *)iph + iph->ihl*4;
+
+	oldlen = (*pskb)->len - iph->ihl*4;
+	mangle_contents(*pskb, iph->ihl*4 + sizeof(*udph),
+			match_offset, match_len, rep_buffer, rep_len);
+
+	/* update the length of the UDP packet */
+	datalen = (*pskb)->len - iph->ihl*4;
+	udph->len = htons(datalen);
+
+	/* fix udp checksum if udp checksum was previously calculated */
+	if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL)
+		return 1;
+
+	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
+		udph->check = 0;
+		udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
+		                                datalen, IPPROTO_UDP,
+		                                csum_partial((char *)udph,
+		                                             datalen, 0));
+		if (!udph->check)
+			udph->check = CSUM_MANGLED_0;
+	} else
+		nf_proto_csum_replace2(&udph->check, *pskb,
+				       htons(oldlen), htons(datalen), 1);
+
+	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);
+
+		DEBUGP("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);
+
+		nf_proto_csum_replace4(&tcph->check, skb,
+				       sack->start_seq, new_start_seq, 0);
+		nf_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 **pskb,
+		   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 = (*pskb)->nh.iph->ihl*4 + sizeof(struct tcphdr);
+	optend = (*pskb)->nh.iph->ihl*4 + tcph->doff*4;
+
+	if (!skb_make_writable(pskb, optend))
+		return 0;
+
+	dir = CTINFO2DIR(ctinfo);
+
+	while (optoff < optend) {
+		/* Usually: option, length. */
+		unsigned char *op = (*pskb)->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(*pskb, tcph, optoff+2,
+					    optoff+op[1],
+					    &nat->info.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 **pskb,
+		  struct nf_conn *ct,
+		  enum ip_conntrack_info ctinfo)
+{
+	struct tcphdr *tcph;
+	int dir;
+	__be32 newseq, newack;
+	struct nf_conn_nat *nat = nfct_nat(ct);
+	struct nf_nat_seq *this_way, *other_way;
+
+	dir = CTINFO2DIR(ctinfo);
+
+	this_way = &nat->info.seq[dir];
+	other_way = &nat->info.seq[!dir];
+
+	if (!skb_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph)))
+		return 0;
+
+	tcph = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
+	if (after(ntohl(tcph->seq), this_way->correction_pos))
+		newseq = htonl(ntohl(tcph->seq) + this_way->offset_after);
+	else
+		newseq = htonl(ntohl(tcph->seq) + this_way->offset_before);
+
+	if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
+		  other_way->correction_pos))
+		newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after);
+	else
+		newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before);
+
+	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0);
+	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0);
+
+	DEBUGP("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;
+
+	if (!nf_nat_sack_adjust(pskb, tcph, ct, ctinfo))
+		return 0;
+
+	nf_conntrack_tcp_update(*pskb, (*pskb)->nh.iph->ihl*4, ct, dir);
+
+	return 1;
+}
+EXPORT_SYMBOL(nf_nat_seq_adjust);
+
+/* 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 = IP_NAT_RANGE_MAP_IPS;
+	range.min_ip = range.max_ip
+		= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
+	/* hook doesn't matter, but it has to do source manip */
+	nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
+
+	/* For DST manip, map port here to where it's expected. */
+	range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
+	range.min = range.max = exp->saved_proto;
+	range.min_ip = range.max_ip
+		= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
+	/* hook doesn't matter, but it has to do destination manip */
+	nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
+}
+EXPORT_SYMBOL(nf_nat_follow_master);