// SPDX-License-Identifier: GPL-2.0-only
#include <linux/types.h>
#include <linux/netfilter.h>
#include <net/tcp.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_extend.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
s32 off)
{
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
struct nf_conn_seqadj *seqadj;
struct nf_ct_seqadj *this_way;
if (off == 0)
return 0;
set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
seqadj = nfct_seqadj(ct);
this_way = &seqadj->seq[dir];
this_way->offset_before = off;
this_way->offset_after = off;
return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_seqadj_init);
int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
__be32 seq, s32 off)
{
struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
struct nf_ct_seqadj *this_way;
if (off == 0)
return 0;
if (unlikely(!seqadj)) {
WARN_ONCE(1, "Missing nfct_seqadj_ext_add() setup call\n");
return 0;
}
set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
spin_lock_bh(&ct->lock);
this_way = &seqadj->seq[dir];
if (this_way->offset_before == this_way->offset_after ||
before(this_way->correction_pos, ntohl(seq))) {
this_way->correction_pos = ntohl(seq);
this_way->offset_before = this_way->offset_after;
this_way->offset_after += off;
}
spin_unlock_bh(&ct->lock);
return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_seqadj_set);
void nf_ct_tcp_seqadj_set(struct sk_buff *skb,
struct nf_conn *ct, enum ip_conntrack_info ctinfo,
s32 off)
{
const struct tcphdr *th;
if (nf_ct_protonum(ct) != IPPROTO_TCP)
return;
th = (struct tcphdr *)(skb_network_header(skb) + ip_hdrlen(skb));
nf_ct_seqadj_set(ct, ctinfo, th->seq, off);
}
EXPORT_SYMBOL_GPL(nf_ct_tcp_seqadj_set);
/* Adjust one found SACK option including checksum correction */
static void nf_ct_sack_block_adjust(struct sk_buff *skb,
struct tcphdr *tcph,
unsigned int sackoff,
unsigned int sackend,
struct nf_ct_seqadj *seq)
{
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) - seq->offset_before,
seq->correction_pos))
new_start_seq = htonl(ntohl(sack->start_seq) -
seq->offset_after);
else
new_start_seq = htonl(ntohl(sack->start_seq) -
seq->offset_before);
if (after(ntohl(sack->end_seq) - seq->offset_before,
seq->correction_pos))
new_end_seq = htonl(ntohl(sack->end_seq) -
seq->offset_after);
else
new_end_seq = htonl(ntohl(sack->end_seq) -
seq->offset_before);
pr_debug("sack_adjust: start_seq: %u->%u, end_seq: %u->%u\n",
ntohl(sack->start_seq), ntohl(new_start_seq),
ntohl(sack->end_seq), ntohl(new_end_seq));
inet_proto_csum_replace4(&tcph->check, skb,
sack->start_seq, new_start_seq, false);
inet_proto_csum_replace4(&tcph->check, skb,
sack->end_seq, new_end_seq, false);
sack->start_seq = new_start_seq;
sack->end_seq = new_end_seq;
sackoff += sizeof(*sack);
}
}
/* TCP SACK sequence number adjustment */
static unsigned int nf_ct_sack_adjust(struct sk_buff *skb,
unsigned int protoff,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
struct tcphdr *tcph = (void *)skb->data + protoff;
struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
unsigned int dir, optoff, optend;
optoff = protoff + sizeof(struct tcphdr);
optend = protoff + tcph->doff * 4;
if (skb_ensure_writable(skb, optend))
return 0;
tcph = (void *)skb->data + protoff;
dir = CTINFO2DIR(ctinfo);
while (optoff < optend) {
/* Usually: option, length. */
unsigned char *op = skb->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)
nf_ct_sack_block_adjust(skb, tcph, optoff + 2,
optoff+op[1],
&seqadj->seq[!dir]);
optoff += op[1];
}
}
return 1;
}
/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
int nf_ct_seq_adjust(struct sk_buff *skb,
struct nf_conn *ct, enum ip_conntrack_info ctinfo,
unsigned int protoff)
{
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
struct tcphdr *tcph;
__be32 newseq, newack;
s32 seqoff, ackoff;
struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
struct nf_ct_seqadj *this_way, *other_way;
int res = 1;
this_way = &seqadj->seq[dir];
other_way = &seqadj->seq[!dir];
if (skb_ensure_writable(skb, protoff + sizeof(*tcph)))
return 0;
tcph = (void *)skb->data + protoff;
spin_lock_bh(&ct->lock);
if (after(ntohl(tcph->seq), this_way->correction_pos))
seqoff = this_way->offset_after;
else
seqoff = this_way->offset_before;
newseq = htonl(ntohl(tcph->seq) + seqoff);
inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, false);
pr_debug("Adjusting sequence number from %u->%u\n",
ntohl(tcph->seq), ntohl(newseq));
tcph->seq = newseq;
if (!tcph->ack)
goto out;
if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
other_way->correction_pos))
ackoff = other_way->offset_after;
else
ackoff = other_way->offset_before;
newack = htonl(ntohl(tcph->ack_seq) - ackoff);
inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack,
false);
pr_debug("Adjusting ack number from %u->%u, ack from %u->%u\n",
ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
ntohl(newack));
tcph->ack_seq = newack;
res = nf_ct_sack_adjust(skb, protoff, ct, ctinfo);
out:
spin_unlock_bh(&ct->lock);
return res;
}
EXPORT_SYMBOL_GPL(nf_ct_seq_adjust);
s32 nf_ct_seq_offset(const struct nf_conn *ct,
enum ip_conntrack_dir dir,
u32 seq)
{
struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
struct nf_ct_seqadj *this_way;
if (!seqadj)
return 0;
this_way = &seqadj->seq[dir];
return after(seq, this_way->correction_pos) ?
this_way->offset_after : this_way->offset_before;
}
EXPORT_SYMBOL_GPL(nf_ct_seq_offset);
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