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 | |
10 | int 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 | } |
28 | EXPORT_SYMBOL_GPL(nf_ct_seqadj_init); |
29 | |
30 | int 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 | } |
58 | EXPORT_SYMBOL_GPL(nf_ct_seqadj_set); |
59 | |
60 | void 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 | } |
72 | EXPORT_SYMBOL_GPL(nf_ct_tcp_seqadj_set); |
73 | |
74 | /* Adjust one found SACK option including checksum correction */ |
75 | static 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 */ |
117 | static 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 */ |
164 | int 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); |
213 | out: |
214 | spin_unlock_bh(lock: &ct->lock); |
215 | |
216 | return res; |
217 | } |
218 | EXPORT_SYMBOL_GPL(nf_ct_seq_adjust); |
219 | |
220 | s32 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 | } |
234 | EXPORT_SYMBOL_GPL(nf_ct_seq_offset); |
235 | |