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