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(nr: IPS_SEQ_ADJUST_BIT, addr: &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(nr: IPS_SEQ_ADJUST_BIT, addr: &ct->status);
46
47 spin_lock_bh(lock: &ct->lock);
48 this_way = &seqadj->seq[dir];
49 if (this_way->offset_before == this_way->offset_after ||
50 before(seq1: 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(lock: &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(sum: &tcph->check, skb,
107 from: sack->start_seq, to: new_start_seq, pseudohdr: false);
108 inet_proto_csum_replace4(sum: &tcph->check, skb,
109 from: sack->end_seq, to: new_end_seq, pseudohdr: 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, write_len: 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, sackoff: optoff + 2,
155 sackend: optoff+op[1],
156 seq: &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, write_len: protoff + sizeof(*tcph)))
180 return 0;
181
182 tcph = (void *)skb->data + protoff;
183 spin_lock_bh(lock: &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(sum: &tcph->check, skb, from: tcph->seq, to: newseq, pseudohdr: 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(sum: &tcph->check, skb, from: tcph->ack_seq, to: newack,
206 pseudohdr: 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(lock: &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

source code of linux/net/netfilter/nf_conntrack_seqadj.c