diff options
| -rw-r--r-- | net/ipv4/tcp_input.c | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 1a34e9278c07..bfa165cc455a 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5199,6 +5199,23 @@ static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) return err; } +/* Accept RST for rcv_nxt - 1 after a FIN. + * When tcp connections are abruptly terminated from Mac OSX (via ^C), a + * FIN is sent followed by a RST packet. The RST is sent with the same + * sequence number as the FIN, and thus according to RFC 5961 a challenge + * ACK should be sent. However, Mac OSX rate limits replies to challenge + * ACKs on the closed socket. In addition middleboxes can drop either the + * challenge ACK or a subsequent RST. + */ +static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) && + (1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK | + TCPF_CLOSING)); +} + /* Does PAWS and seqno based validation of an incoming segment, flags will * play significant role here. */ @@ -5237,20 +5254,25 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, LINUX_MIB_TCPACKSKIPPEDSEQ, &tp->last_oow_ack_time)) tcp_send_dupack(sk, skb); + } else if (tcp_reset_check(sk, skb)) { + tcp_reset(sk); } goto discard; } /* Step 2: check RST bit */ if (th->rst) { - /* RFC 5961 3.2 (extend to match against SACK too if available): - * If seq num matches RCV.NXT or the right-most SACK block, + /* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a + * FIN and SACK too if available): + * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or + * the right-most SACK block, * then * RESET the connection * else * Send a challenge ACK */ - if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { + if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt || + tcp_reset_check(sk, skb)) { rst_seq_match = true; } else if (tcp_is_sack(tp) && tp->rx_opt.num_sacks > 0) { struct tcp_sack_block *sp = &tp->selective_acks[0]; |