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![Florian Westphal](/assets/img/avatar_default.png)
When adjusting sack block sequence numbers, skb_make_writable() gets called to make sure tcp options are all in the linear area, and buffer is not shared. This can cause tcp header pointer to get reallocated, so we must reaload it to avoid memory corruption. This bug pre-dates git history. Reported-by: Neel Mehta <nmehta@google.com> Reported-by: Shane Huntley <shuntley@google.com> Reported-by: Heather Adkins <argv@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
249 lines
6.5 KiB
C
249 lines
6.5 KiB
C
#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_make_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_make_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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