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-rw-r--r--include/linux/netfilter/nf_conntrack_tcp.h3
-rw-r--r--net/netfilter/nf_conntrack_proto_tcp.c51
2 files changed, 44 insertions, 10 deletions
diff --git a/include/linux/netfilter/nf_conntrack_tcp.h b/include/linux/netfilter/nf_conntrack_tcp.h
index 4352feed2377..ece22e94dcbf 100644
--- a/include/linux/netfilter/nf_conntrack_tcp.h
+++ b/include/linux/netfilter/nf_conntrack_tcp.h
@@ -67,6 +67,9 @@ struct ip_ct_tcp
u_int32_t last_ack; /* Last sequence number seen in opposite dir */
u_int32_t last_end; /* Last seq + len */
u_int16_t last_win; /* Last window advertisement seen in dir */
+ /* For SYN packets while we may be out-of-sync */
+ u_int8_t last_wscale; /* Last window scaling factor seen */
+ u_int8_t last_flags; /* Last flags set */
};
#endif /* __KERNEL__ */
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 97a82ba75376..9cc6b5cb06af 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -908,23 +908,54 @@ static int tcp_packet(struct nf_conn *ct,
/* b) This SYN/ACK acknowledges a SYN that we earlier
* ignored as invalid. This means that the client and
* the server are both in sync, while the firewall is
- * not. We kill this session and block the SYN/ACK so
- * that the client cannot but retransmit its SYN and
- * thus initiate a clean new session.
+ * not. We get in sync from the previously annotated
+ * values.
*/
- spin_unlock_bh(&ct->lock);
- if (LOG_INVALID(net, IPPROTO_TCP))
- nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
- "nf_ct_tcp: killing out of sync session ");
- nf_ct_kill(ct);
- return NF_DROP;
+ old_state = TCP_CONNTRACK_SYN_SENT;
+ new_state = TCP_CONNTRACK_SYN_RECV;
+ ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end =
+ ct->proto.tcp.last_end;
+ ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend =
+ ct->proto.tcp.last_end;
+ ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin =
+ ct->proto.tcp.last_win == 0 ?
+ 1 : ct->proto.tcp.last_win;
+ ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale =
+ ct->proto.tcp.last_wscale;
+ ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
+ ct->proto.tcp.last_flags;
+ memset(&ct->proto.tcp.seen[dir], 0,
+ sizeof(struct ip_ct_tcp_state));
+ break;
}
ct->proto.tcp.last_index = index;
ct->proto.tcp.last_dir = dir;
ct->proto.tcp.last_seq = ntohl(th->seq);
ct->proto.tcp.last_end =
segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
-
+ ct->proto.tcp.last_win = ntohs(th->window);
+
+ /* a) This is a SYN in ORIGINAL. The client and the server
+ * may be in sync but we are not. In that case, we annotate
+ * the TCP options and let the packet go through. If it is a
+ * valid SYN packet, the server will reply with a SYN/ACK, and
+ * then we'll get in sync. Otherwise, the server ignores it. */
+ if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) {
+ struct ip_ct_tcp_state seen = {};
+
+ ct->proto.tcp.last_flags =
+ ct->proto.tcp.last_wscale = 0;
+ tcp_options(skb, dataoff, th, &seen);
+ if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
+ ct->proto.tcp.last_flags |=
+ IP_CT_TCP_FLAG_WINDOW_SCALE;
+ ct->proto.tcp.last_wscale = seen.td_scale;
+ }
+ if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) {
+ ct->proto.tcp.last_flags |=
+ IP_CT_TCP_FLAG_SACK_PERM;
+ }
+ }
spin_unlock_bh(&ct->lock);
if (LOG_INVALID(net, IPPROTO_TCP))
nf_log_packet(pf, 0, skb, NULL, NULL, NULL,