diff options
| -rw-r--r-- | net/netfilter/nf_conntrack_proto_tcp.c | 32 |
1 files changed, 26 insertions, 6 deletions
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index 3e0ccca..202d7fa 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -125,7 +125,7 @@ enum tcp_bit_set { * CLOSE_WAIT: ACK seen (after FIN) * LAST_ACK: FIN seen (after FIN) * TIME_WAIT: last ACK seen - * CLOSE: closed connection + * CLOSE: closed connection (RST) * * LISTEN state is not used. * @@ -824,7 +824,21 @@ static int tcp_packet(struct nf_conn *ct, case TCP_CONNTRACK_SYN_SENT: if (old_state < TCP_CONNTRACK_TIME_WAIT) break; - if ((ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_CLOSE_INIT) + /* RFC 1122: "When a connection is closed actively, + * it MUST linger in TIME-WAIT state for a time 2xMSL + * (Maximum Segment Lifetime). However, it MAY accept + * a new SYN from the remote TCP to reopen the connection + * directly from TIME-WAIT state, if..." + * We ignore the conditions because we are in the + * TIME-WAIT state anyway. + * + * Handle aborted connections: we and the server + * think there is an existing connection but the client + * aborts it and starts a new one. + */ + if (((ct->proto.tcp.seen[dir].flags + | ct->proto.tcp.seen[!dir].flags) + & IP_CT_TCP_FLAG_CLOSE_INIT) || (ct->proto.tcp.last_dir == dir && ct->proto.tcp.last_index == TCP_RST_SET)) { /* Attempt to reopen a closed/aborted connection. @@ -838,15 +852,22 @@ static int tcp_packet(struct nf_conn *ct, case TCP_CONNTRACK_IGNORE: /* Ignored packets: * + * Our connection entry may be out of sync, so ignore + * packets which may signal the real connection between + * the client and the server. + * * a) SYN in ORIGINAL * b) SYN/ACK in REPLY * c) ACK in reply direction after initial SYN in original. + * + * If the ignored packet is invalid, the receiver will send + * a RST we'll catch below. */ if (index == TCP_SYNACK_SET && ct->proto.tcp.last_index == TCP_SYN_SET && ct->proto.tcp.last_dir != dir && ntohl(th->ack_seq) == ct->proto.tcp.last_end) { - /* This SYN/ACK acknowledges a SYN that we earlier + /* 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 @@ -870,7 +891,7 @@ static int tcp_packet(struct nf_conn *ct, write_unlock_bh(&tcp_lock); if (LOG_INVALID(IPPROTO_TCP)) nf_log_packet(pf, 0, skb, NULL, NULL, NULL, - "nf_ct_tcp: invalid packed ignored "); + "nf_ct_tcp: invalid packet ignored "); return NF_ACCEPT; case TCP_CONNTRACK_MAX: /* Invalid packet */ @@ -924,8 +945,7 @@ static int tcp_packet(struct nf_conn *ct, ct->proto.tcp.state = new_state; if (old_state != new_state - && (new_state == TCP_CONNTRACK_FIN_WAIT - || new_state == TCP_CONNTRACK_CLOSE)) + && new_state == TCP_CONNTRACK_CLOSE) ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT; timeout = ct->proto.tcp.retrans >= nf_ct_tcp_max_retrans && tcp_timeouts[new_state] > nf_ct_tcp_timeout_max_retrans |