1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/types.h>
3#include <linux/netfilter.h>
4#include <net/tcp.h>
5
6#include <net/netfilter/nf_conntrack.h>
7#include <net/netfilter/nf_conntrack_extend.h>
8#include <net/netfilter/nf_conntrack_seqadj.h>
9
10int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
11		      s32 off)
12{
13	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
14	struct nf_conn_seqadj *seqadj;
15	struct nf_ct_seqadj *this_way;
16
17	if (off == 0)
18		return 0;
19
20	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
21
22	seqadj = nfct_seqadj(ct);
23	this_way = &seqadj->seq[dir];
24	this_way->offset_before	 = off;
25	this_way->offset_after	 = off;
26	return 0;
27}
28EXPORT_SYMBOL_GPL(nf_ct_seqadj_init);
29
30int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
31		     __be32 seq, s32 off)
32{
33	struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
34	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
35	struct nf_ct_seqadj *this_way;
36
37	if (off == 0)
38		return 0;
39
40	if (unlikely(!seqadj)) {
41		WARN_ONCE(1, "Missing nfct_seqadj_ext_add() setup call\n");
42		return 0;
43	}
44
45	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
46
47	spin_lock_bh(&ct->lock);
48	this_way = &seqadj->seq[dir];
49	if (this_way->offset_before == this_way->offset_after ||
50	    before(this_way->correction_pos, ntohl(seq))) {
51		this_way->correction_pos = ntohl(seq);
52		this_way->offset_before	 = this_way->offset_after;
53		this_way->offset_after	+= off;
54	}
55	spin_unlock_bh(&ct->lock);
56	return 0;
57}
58EXPORT_SYMBOL_GPL(nf_ct_seqadj_set);
59
60void nf_ct_tcp_seqadj_set(struct sk_buff *skb,
61			  struct nf_conn *ct, enum ip_conntrack_info ctinfo,
62			  s32 off)
63{
64	const struct tcphdr *th;
65
66	if (nf_ct_protonum(ct) != IPPROTO_TCP)
67		return;
68
69	th = (struct tcphdr *)(skb_network_header(skb) + ip_hdrlen(skb));
70	nf_ct_seqadj_set(ct, ctinfo, th->seq, off);
71}
72EXPORT_SYMBOL_GPL(nf_ct_tcp_seqadj_set);
73
74/* Adjust one found SACK option including checksum correction */
75static void nf_ct_sack_block_adjust(struct sk_buff *skb,
76				    struct tcphdr *tcph,
77				    unsigned int sackoff,
78				    unsigned int sackend,
79				    struct nf_ct_seqadj *seq)
80{
81	while (sackoff < sackend) {
82		struct tcp_sack_block_wire *sack;
83		__be32 new_start_seq, new_end_seq;
84
85		sack = (void *)skb->data + sackoff;
86		if (after(ntohl(sack->start_seq) - seq->offset_before,
87			  seq->correction_pos))
88			new_start_seq = htonl(ntohl(sack->start_seq) -
89					seq->offset_after);
90		else
91			new_start_seq = htonl(ntohl(sack->start_seq) -
92					seq->offset_before);
93
94		if (after(ntohl(sack->end_seq) - seq->offset_before,
95			  seq->correction_pos))
96			new_end_seq = htonl(ntohl(sack->end_seq) -
97				      seq->offset_after);
98		else
99			new_end_seq = htonl(ntohl(sack->end_seq) -
100				      seq->offset_before);
101
102		pr_debug("sack_adjust: start_seq: %u->%u, end_seq: %u->%u\n",
103			 ntohl(sack->start_seq), ntohl(new_start_seq),
104			 ntohl(sack->end_seq), ntohl(new_end_seq));
105
106		inet_proto_csum_replace4(&tcph->check, skb,
107					 sack->start_seq, new_start_seq, false);
108		inet_proto_csum_replace4(&tcph->check, skb,
109					 sack->end_seq, new_end_seq, false);
110		sack->start_seq = new_start_seq;
111		sack->end_seq = new_end_seq;
112		sackoff += sizeof(*sack);
113	}
114}
115
116/* TCP SACK sequence number adjustment */
117static unsigned int nf_ct_sack_adjust(struct sk_buff *skb,
118				      unsigned int protoff,
119				      struct nf_conn *ct,
120				      enum ip_conntrack_info ctinfo)
121{
122	struct tcphdr *tcph = (void *)skb->data + protoff;
123	struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
124	unsigned int dir, optoff, optend;
125
126	optoff = protoff + sizeof(struct tcphdr);
127	optend = protoff + tcph->doff * 4;
128
129	if (skb_ensure_writable(skb, optend))
130		return 0;
131
132	tcph = (void *)skb->data + protoff;
133	dir = CTINFO2DIR(ctinfo);
134
135	while (optoff < optend) {
136		/* Usually: option, length. */
137		unsigned char *op = skb->data + optoff;
138
139		switch (op[0]) {
140		case TCPOPT_EOL:
141			return 1;
142		case TCPOPT_NOP:
143			optoff++;
144			continue;
145		default:
146			/* no partial options */
147			if (optoff + 1 == optend ||
148			    optoff + op[1] > optend ||
149			    op[1] < 2)
150				return 0;
151			if (op[0] == TCPOPT_SACK &&
152			    op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
153			    ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
154				nf_ct_sack_block_adjust(skb, tcph, optoff + 2,
155							optoff+op[1],
156							&seqadj->seq[!dir]);
157			optoff += op[1];
158		}
159	}
160	return 1;
161}
162
163/* TCP sequence number adjustment.  Returns 1 on success, 0 on failure */
164int nf_ct_seq_adjust(struct sk_buff *skb,
165		     struct nf_conn *ct, enum ip_conntrack_info ctinfo,
166		     unsigned int protoff)
167{
168	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
169	struct tcphdr *tcph;
170	__be32 newseq, newack;
171	s32 seqoff, ackoff;
172	struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
173	struct nf_ct_seqadj *this_way, *other_way;
174	int res = 1;
175
176	this_way  = &seqadj->seq[dir];
177	other_way = &seqadj->seq[!dir];
178
179	if (skb_ensure_writable(skb, protoff + sizeof(*tcph)))
180		return 0;
181
182	tcph = (void *)skb->data + protoff;
183	spin_lock_bh(&ct->lock);
184	if (after(ntohl(tcph->seq), this_way->correction_pos))
185		seqoff = this_way->offset_after;
186	else
187		seqoff = this_way->offset_before;
188
189	newseq = htonl(ntohl(tcph->seq) + seqoff);
190	inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, false);
191	pr_debug("Adjusting sequence number from %u->%u\n",
192		 ntohl(tcph->seq), ntohl(newseq));
193	tcph->seq = newseq;
194
195	if (!tcph->ack)
196		goto out;
197
198	if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
199		  other_way->correction_pos))
200		ackoff = other_way->offset_after;
201	else
202		ackoff = other_way->offset_before;
203
204	newack = htonl(ntohl(tcph->ack_seq) - ackoff);
205	inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack,
206				 false);
207	pr_debug("Adjusting ack number from %u->%u, ack from %u->%u\n",
208		 ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
209		 ntohl(newack));
210	tcph->ack_seq = newack;
211
212	res = nf_ct_sack_adjust(skb, protoff, ct, ctinfo);
213out:
214	spin_unlock_bh(&ct->lock);
215
216	return res;
217}
218EXPORT_SYMBOL_GPL(nf_ct_seq_adjust);
219
220s32 nf_ct_seq_offset(const struct nf_conn *ct,
221		     enum ip_conntrack_dir dir,
222		     u32 seq)
223{
224	struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
225	struct nf_ct_seqadj *this_way;
226
227	if (!seqadj)
228		return 0;
229
230	this_way = &seqadj->seq[dir];
231	return after(seq, this_way->correction_pos) ?
232		 this_way->offset_after : this_way->offset_before;
233}
234EXPORT_SYMBOL_GPL(nf_ct_seq_offset);
235